final draft engineering evaluation gregory …...• one (1) blower with a tbd hp electric motor,...

FINAL DRAFT

ENGINEERING EVALUATION

GREGORY CANYON LANDFILL

SAN DIEGO AIR POLLUTION CONTROL DISTRICT

Application Number APCD2007-APP-985364

August 5, 2013

Senior Engineer: Steven Moore

Application Number: APCD2007-APP-985364

Site ID Number: APCD1998-SITE-10497

Fee Schedule: 48C

BEC: New

APPLICATION INFORMATION

Owner / Operator: Gregory Canyon, Ltd.

Mailing Address: 160 Industrial St #200

San Marcos, CA, 92078

Equipment Address: 9708 Pala Road

Pala, California, 92059

4

Contact: Jim Simmons

Company: *****

Position: Project Manager

Phone Number: ******

Fax Number: ******

TABLE OF CONTENTS

I. PROJECT DESCRIPTION............................................................................................... 1

Introduction ........................................................................................................................... 1

II. EQUIPMENT DESCRIPTION AND OPERATION DESCRIPTION ....................... 3

III. PROCESS DESCRIPTION ............................................................................................ 4

Landfill Capacity .................................................................................................................. 4

Landfill Creation ................................................................................................................... 4

Landfill Operation ................................................................................................................. 4

Road Construction ............................................................................................................ 5

Emission Sources .................................................................................................................. 5

General .............................................................................................................................. 5

Landfill Gas (LFG) ........................................................................................................... 6

Flare Emissions ................................................................................................................. 7

Fugitive Dust ..................................................................................................................... 7

Capacity, Operation, and Throughput Limits on Potential Emissions.................................. 7

Summary of Limits on Emissions ..................................................................................... 8

IV. EMISSION ESTIMATES ............................................................................................. 11

Landfill Gas Emissions ....................................................................................................... 11

General ............................................................................................................................ 11

Methane and Landfill Gas (LFG) Emission Calculation Methodology.......................... 11

Fugitive Landfill Gas Constituent Emission Factors .......................................................... 20

Fugitive Landfill Gas Constitent Emission Factors—General ....................................... 20

Correction of Measured Concentrations for Air Infiltration. .......................................... 20

Correction of VOC Emissions for Molecular Weight and Method Measurement Bias . 21

VOC Emission Factor ..................................................................................................... 22

Toxic Air Contaminants Emission Factors—District Supplemental Analysis ............... 23

Carbon Monoxide. .......................................................................................................... 27

NOx, PM10, PM2.5, SOx. .............................................................................................. 27

Greenhouse Gas Emission Factors. ................................................................................. 27

Summary of Fugitive Landfill Gas Emission Factors..................................................... 28

Landfill Gas Flare Emission Factors (EFs) ......................................................................... 31

Criteria Pollutants. .......................................................................................................... 31

Land Fill Gas Constituent Emission Factors .................................................................. 31

Combustion-by-Product Emission Factors ..................................................................... 31

Greenhouse Gases. .......................................................................................................... 36

Potential to Emit—Fugitive Landfill Gas Constituents ...................................................... 36

Introduction ..................................................................................................................... 36

Maximum Landfill Waste Capacity ................................................................................ 36

Landfill Gas Collection Efficiency ................................................................................. 37

Emissions from Fugitive Landfill Gas ............................................................................ 39

Landfill Gas Maximum Estimated Emissions Summary During Normal Operations .... 39

Startup Emissions............................................................................................................ 40

Flare Emissions ................................................................................................................... 41

Total Maximum Fugitive Landfill Gas Constituent and Flare Emissions .......................... 42

Road Fugitive Particulate Emissions .................................................................................. 42

Introduction ..................................................................................................................... 42

Basic Equations ............................................................................................................... 43

Road Silt Contents .......................................................................................................... 46

Waste Haul Vehicle Characteristics ................................................................................ 47

Rock and Soil Haul Vehicle Characteristics ................................................................... 54

Haul Road Emission Control Factors ............................................................................. 55

Earthmoving and MSW Handling Particulate Emission Factors ........................................ 58

Bulldozer, Scraper Loading, Compactor, and Road Grader Scarification Emission Factors ............................................................................................................................. 58

Scraper and Truck Unloading Earthmoving and MSW Handling Emission Factors ..... 60

Road Grader Emssions .................................................................................................... 61

Earthmoving and MSW Handling Emission Factor Parameters..................................... 62

Earthmoving Travel Emission Control Factors .............................................................. 62

Earthmoving Emission Factor Summary ........................................................................ 63

Earthmoving and MSW Handling Particulate Matter Potential To Emit ........................... 64

PGM Particulate Emissions ................................................................................................ 65

Blasting ............................................................................................................................... 65

Emission Estimation Method .......................................................................................... 65

Blasting Potential to Emit ............................................................................................... 66

Blasting and NO2 ............................................................................................................ 67

Blasting and PM10 .......................................................................................................... 67

Wind-Blown Dust ............................................................................................................... 67

Wind-Blown Dust Emission Factors .............................................................................. 67

Wind Erosion Potential to Emit ...................................................................................... 68

Drilling and Rock Crushing ................................................................................................ 68

Miscellaneous Emission Sources ........................................................................................ 69

Leachate Collection and Disposal System ...................................................................... 69

Fueling Station ................................................................................................................ 69

Chemical Stabilizer VOC Emissions .............................................................................. 69

PM2.5 Emissions ................................................................................................................ 69

Toxic Emission factors for Particulate Matter .................................................................... 69

Overall Project Emission and Potential to Emit ................................................................. 70

Applicant Calculated Emissions ..................................................................................... 70

V. RULES ANALYSIS ........................................................................................................ 72

District and Federal NSR and PSD Regulations ................................................................. 72

Rule 20.1(c)(35)—Major Stationary Source................................................................... 72

Rule 20.1(c)(58)—Prevention of Significant Deterioration (PSD) Stationary Source and 40 CFR 52.21—Criteria Pollutants ................................................................................. 73

Rule 20.1( c)(16) Contemporaneous Emission Increase ................................................ 74

Rule 20.2(d)(1)- Best Available Control Technology(BACT) ....................................... 74

Rule 20.2 (d)(2)—Air Quality Impact Analysis (AQIA)................................................ 75

Rule 20.2 (d)(3)-Prevention of Significant Deterioration (PSD) .................................... 79

Rule 20.2 (d)(4)—Public Notice and Comment ............................................................. 79

District Prohibitory Rules ................................................................................................... 79

Rule 50—Visible Emissions ........................................................................................... 79

Rule 51—Nuisance ......................................................................................................... 79

Rule 53—Specific Air Contaminants ............................................................................. 80

Rule 54 –Dust and Fumes ............................................................................................... 80

Rule 55 – Fugitive Dust Control ..................................................................................... 80

Rule 59—Control of Waste Disposal Site Emissions ..................................................... 81

Rule 68 –Oxides of Nitrogen from Fuel Burning Equipment......................................... 82

Rule 1200—Toxic Air Contaminants ............................................................................. 82

Regulation XIV—Title V Operating Permits ................................................................. 83

State Regulations Implemented by the District .................................................................. 83

Health and Safety Code §42301.6 .................................................................................. 83

Title 17 of the California Codes of Regulations (CCR) §95460 to 95476 —Methane Emissions from Municipal Solid Waste Landfills .......................................................... 84

National Emissions Standards for Hazardous Air Pollutants (NESHAPS) ........................ 84

40 CFR Part 63 Subpart AAAA— National Emission Standards for Hazardous Air Pollutants: Municipal Solid Waste Landfills ................................................................. 84

New Source Performance Standards (NSPS) ..................................................................... 84

40 CFR Part 60- Subpart WWW- Standards of Performance for Municipal SolidWaste Landfills. ......................................................................................................................... 84

VI. CONCLUSIONS AND RECOMMENDATIONS ...................................................... 84

VII REFERENCES .............................................................................................................. 86

APPENDIX A .......................................................................................................................... 1

I. BASIS OF FUGITIVE LANDFILL GAS MONITORING ........................................ 2

Fugitive Methane Emission Calculation Methodology ........................................................ 2

II. REFERENCE LANDFILL AND MONITORING EQUATION ............................... 4

APPENDIX B .......................................................................................................................... 0

I. INTRODUCTION........................................................................................................... 1

II. MAJOR MODELING ISSUES ..................................................................................... 2

Impacts at the South End of the Landfill .............................................................................. 3

24-Hour Impacts ............................................................................................................... 3

Annual Impacts ................................................................................................................. 3

Modeling Scenarios .............................................................................................................. 3

Year -2—24-Hour ............................................................................................................. 3

Year -2—Annual ............................................................................................................... 3

Years 1, 17, and 22, BAB—24-Hour ................................................................................ 4

Year 22 Working Face Location ....................................................................................... 4

Scraper Speed at End-of-Road .............................................................................................. 5

Liner Installation ................................................................................................................... 6

Landfill Earthen Fill Operations ........................................................................................... 6

Earthmoving Amounts .......................................................................................................... 6

Daily Earthmoving Volumes ............................................................................................ 6

Annual Earthmoving Volumes ......................................................................................... 7

Year 1 Potential Cover Material Use .................................................................................... 7

BAB Road Operations .......................................................................................................... 7

Road Grades, Length, and Elevation, Modeling Parameters ................................................ 8

BAB Road Elevation......................................................................................................... 8

Internal Haul Roads Grades and Lengths ......................................................................... 8

Paved Main Access Road Grade ....................................................................................... 8

Paved Main Access Road Location. ................................................................................. 9

Paved Main Access Road Lateral Dispersion Parameters ................................................ 9

Volume Source Spacing for Roads ................................................................................... 9

Waste Haul Road Elevation .............................................................................................. 9

MSW Operation Emissions................................................................................................... 9

Road Fugitive Dust Emission Control from Precipitation .................................................. 10

Potential Cover Transport from an Intermediate Storage Pile ............................................ 10

Liner and Liner Protective Layer Transport ....................................................................... 10

Year 1 Direct Cover Road Air Quality Impacts.................................................................. 11

Year 1 BAB Road ........................................................................................................... 11

Rock Crushing Emissions ................................................................................................... 12

Landfill Footprint Rock Crushing Off-Road Travel ....................................................... 12

BAB Off-Road Travel..................................................................................................... 12

Blast Size ............................................................................................................................ 12

Alternative Cover Handling ................................................................................................ 12

Road Grading Emissions..................................................................................................... 13

Volume Source Dimensions for Earthmoving and Waste Handling .................................. 13

Borrow Area Receptor Grid Locations ............................................................................... 13

BAA ................................................................................................................................ 13

BAB and Southern End of Landfill ................................................................................ 13

III. ADJUSTED PM10 AIR QUALITY IMPACTS AND EMISSIONS ..................... 14

Annual PM10 Impacts and Emissions ................................................................................ 14

24-Hour PM10 Impacts and Emissions .............................................................................. 16

IV. AIR QUALITY FACTORS GENERAL CALCULATION PROCEDURE ........ 20

General ................................................................................................................................ 20

Regulatory Compliance ...................................................................................................... 22

Selecting Modeled Day For Monitoring 24-Hour Impacts ................................................. 24

V. AIR QUALITY IMPACT FACTORS FOR MONITORING .................................. 29

Road Air Quality Impact Factors ....................................................................................... 29

Calculation Procedure ..................................................................................................... 29

Material Handling Air Quality Impact Factors ................................................................... 31

Calculation Procedure ..................................................................................................... 31

VI. ANNUAL AIR QUALITY IMPACT FACTORS ................................................... 32

Annual Road Air Quality Impact Factors for Monitoring .................................................. 32

Annual Material Handling Operation Air Quality Impact Factors for Monitoring ............ 35

Annual Unmonitored Air Quality Impacts ......................................................................... 39

VII. DAILY AIR QUALITY IMPACT FACTORS ....................................................... 40

Daily Road Air Quality Impact Factors for Monitoring ..................................................... 40

DAily Material Handling Operation Air Quality Impact Factors for Monitoring .............. 41

Daily Unmonitored Air Quality Impacts and Background for Monitoring ........................ 42

VIII. ANNUAL MONITORING EMISSION FACTORS ........................................... 44

Emission Factor Calculation Procedure .............................................................................. 44

Annual Road Emission Factors for Monitoring .................................................................. 44

Annual Material Handling Operation Emission Factors for Monitoring ............................ 47

Annual Unmonitored Emissions ......................................................................................... 51

IX. MONITORING EXCAVATION AMOUNTS ........................................................ 52

X. MONITORING AREA FOR SOUTHERN LANDFILL 24-HOUR AMBIENT AIR QUALITY IMPACTS .......................................................................................................... 56

XI. SLOPING TERRAIN ................................................................................................ 56

APPENDICES

Appendix A—Fugitive Methane Monitoring

Appendix B—PM10 Ambient Air Quality Impact and Emission Monitoring

Engineering Evaluation Page 1 of 98 August 5, 2013

Applications No APCD2007-APP-985364

I. PROJECT DESCRIPTION

INTRODUCTION Gregory Canyon Landfill is a proposed Class III municipal solid waste (MSW) disposal facility located at 9708 Pala Road, Pala, California 92059, on property owned by Gregory Canyon, Ltd., the project applicant. The site is located in northern San Diego County approximately three miles east of Interstate 15 (I-15) and two miles southwest of the community of Pala. SR 76 and the San Luis Rey River run east-west through the landfill property. The proposed landfill footprint itself is located approximately in the center of the property south of SR 76 and the San Luis Rey River in Gregory Canyon. The total site area is 1,770 acres. Of that area, 308 acres are permitted for use for landfill activities. The proposed landfill footprint, where waste will be deposited, has an area of 183 acres. The applicant estimates that

Approximately 87 acres of borrow/stockpile areas are proposed in two locations and are to be used primarily to provide soil to cover the deposited waste and crushed rock to be mixed with soil to provide cover material for the waste or used for other landfill operations such as road construction. Borrow/Stockpile Area A (BAA), which is about 22 acres in size, will be located west of the landfill footprint about 50 feet from the western property boundary. Borrow/Stockpile Area B (BAB), which is about 65 acres in size, will be located immediately to the west of the southern portion of the landfill footprint 130 to 500 feet from the southern property boundary. Material excavated from the landfill footprint during initial construction for use in landfill operations will be stored for future use in BAA and BAB. After the material excavated from the landfill footprint has been used, the borrow areas will be excavated to provide additional material for landfill operations. Material rock or soil excavated from the landfill or borrow areas, including material stored in the borrow areas, potentially could be exported from the landfill for commercial or other purposes.

There are also two desilting basins. The eastern basin has an area of 1.8 acres and the western basin an area of 3.7 acres.

The facility is also proposed to have a paved main entrance road, unpaved internal waste haul roads, unpaved roads from BAA and BAB to the landill footprint, and numerous other unpaved roads to access various parts o the facility. In addition a paved ancillary facilities area will be constructed on bordering the northern edge of the landfill footprint.

Figure I-1 shows the proposed layout of the Gregory Canyon Landfill and some major features of the landfill as they are expected to exist when the landfill reaches its maximum capacity. Except for the portion of the BAA road between BAA and the landfill footprint, the locations of the unpaved roads are only approximate.



II. EQUIPMENT DESCRIPTION AND OPERATION DESCRIPTION

The Applicant has proposed to construct and operate the following equipment at this facility under Application No. APCD2007-APP-985364:

• One (1) landfill gas collection system consisting of: TBD number of vertical landfill gas collections wells, TBD linear feet of horizontal gas wells, and associated piping to collect landfill gas generated by the deposited waste and convey the gas to the flare.

• One (1) enclosed flare manufactured by TBD, Model No. TBD, Serial No. TBD, with a stack not more than 7'-7"inches in internal diameter and not less than 40'-0" high, rated at a maximum of 1500 scfm inlet landfill gas fuel inlet capacity and a maximum heat input rate of 45.5 MMbtu per hour to control landfill gas emissions.

• One (1) blower with a TBD hp electric motor, manufactured by TBD, Model No. TBD, Serial No. TBD, providing TBD amount of vacuum to the gas collection system and supplying landfill gas to the flare.

• One (1) backup blower with a TBD hp electric motor, manufactured by TBD, Model No. TBD, Serial No. TBD, providing TBD amount of vacuum to the gas collection system and supplying landfill gas to the flare

• One (1) landfill leachate collection system consisting of the collection system with associated pumps and piping and two (2) 10,000 gallon leachate storage tanks.

• One (1) condensate collection system consisting of associated pumps and piping and one (1) 3,000 gallon condensate storage tank.

• One (1) flare station where the enclosed flare will be installed along with any additional flares if they have received an approved Authority to Construct (A/C)from the District.

• The following main haul roads: a paved main entrance road traveling from the facility entrance to the landfill footprint; one or more internal waste haul roads to be used to haul solid waste to a working face within the landfill footprint; a Borrow Area A Haul Road used haul material to or from BAA; a Borrow Area B Haul Road used haul material to or from BAB; one or more cover haul roads used to haul cover materials from storage piles within the landfill footprint to the point to cover waste.

• Other internal roads as necessary to access areas of the facility.

The applicant has also proposed additional equipment to be permitted, as required, at a later date including additional enclosed flares, rock crushing and screening equipment and any associated engines, drilling equipment for blasting and any associated engines, and an on-site fueling station. The potential emissions from this equipment are addressed in the analysis for this A/C to fully evaluate the potential air quality impacts. However, except for certain conditions to ensure that the evaluated emission impacts from this equipment remain valid and that certain requirements are not circumvented by allowing later permitting, this equipment is not within the scope of this evaluation.



III. PROCESS DESCRIPTION

LANDFILL CAPACITY The proposed landfill is permitted as a Class III municipal solid waste landfill under Solid Waste Facility Permit No. 37-AA-0032 issued by the Local Enforcement Agency (LEA, 2011) (LEA 2011) with an approved net air space (capacity) of 57,000,000 cubic yards, a permitted waste disposal area of 183 acres (the landfill footprint), a permitted site area of 308 acres, a permitted maximum height above mean sea level (MSL) of 1100 feet, and a permitted maximum depth of 380 (MSL). Under the approved solid waste facility permit the landfill may accept solid nonhazardous waste including municipal solid waste (MSW) and potentially decontaminated bio-hazardous wastes, dead animals, altered waste tires, agricultural wastes, industrial waste, sewage sludge, and construction/demolition and inert debris.

LANDFILL CREATION The proposed landfill development will include the excavation of approximately 7.9 million cubic yards (MMcy) within the landfill footprint, of which approximately 4.9 MMcy consists of topsoil, alluvium/colluvium, weathered bedrock and rippable hard rock that would be suitable for covering deposited waste, as required by state law, in some cases after crushing and screening. A rock crushing operation is proposed for this purpose. Some of the excavated material will also be used as fill for the ancillary facility area and to shape the canyon surface to facilitate the installation of a clay liner that underlies the landfill footprint.

The material excavated from the landfill footprint that is suitable for use as cover material will either be stored for future use inside the landfill footprint or transported to either BAA or BAB for storage. The applicant proposes to transport rock not suitable for cover only to BAB.

Overall development of the landfill also includes excavation of soil from BAA and BAB once the stored material from the landfill footprint excavation is exhausted. BAA is proposed to be excavated to depths ranging between 10 and 65 feet below existing ground surface, to extract approximately 1.3 MMcy of soil. BAB is proposed for an excavation that will reach depths ranging from 70 to 150 feet below ground surface and extract approximately 3.2 MMcy of soil.

LANDFILL OPERATION During operation of the landfill, waste haul vehicles enter the landfill via the paved main entrance road and transport the waste over the main entrance road and internal waste haul road to the point where it is deposited in the landfill, known as the working face. The size of the daily working face will vary depending on the actual waste inflow rate and the conditions pertaining to the unloading of the waste during the operational day. At the working face, the waste is typically placed in lifts up to approximately 20 feet high and anywhere from 100 to 200 feet in length. Generally, successive lifts are constructed to create a series of adjoining cells.



Waste placed during the day will be compacted by using a bulldozer or compactor and then covered with six inches of compacted soil or alternative daily cover (ADC) material at the end of the working day. Areas where no additional waste is deposited for more than 180 days must be covered with intermediate cover consisting of twelve inches of soil or ADC, if approved under the Solid Waste Facility Permit.

On-site haul and earthmoving vehicles proposed include scrapers to transport cover soil to the working face, bulldozers and/or compactors to spread and compact the waste deposited and cover materials and participate in construction and excavation activities, and road graders to maintain the facility roads.

As currently proposed by the applicant and approved in the Solid Waste Facility Permit geosynthetic blankets, which are placed over the waste at the end of the working day and then removed for the next day’s operations, and processed green material (PGM) will be used as ADC at the facility. Other materials such as foam products, sludge and sludge-derived materials, ash and cement kiln dust materials, treated auto shredder waste, contaminated sediment, dredge spoils, foundry bonds, energy resource, exploration and production wastes, compost materials, construction and demolition wastes, and shredded tires, could be used if approval is granted under the Solid Waste Facility Permit. No processing of green material (green waste) or compositing on-site is proposed for the facility.

Road Construction Numerous internal haul roads must be constructed and reconstructed over the life of the landfill including the internal waste haul roads, BAA and BAB haul roads, and other cover haul roads. The location of haul roads inside the landfill footprint will be continuously varying as they are covered by waste or the location of the working face changes.

EMISSION SOURCES

General The project has various operational phases each with its own emission profile for emissions of volatile organic compounds (VOCs), toxic air contaminants (TACs), particulate matter less than or equal to 10 microns in diameter (PM10) and less than or less than or equal to 2.5 microns in diameter (PM2.5), oxides of nitrogen (NOx), oxides of sulfur (SOx), carbon monoxide (CO). The expected operations occurring during each phase determine the emission profile for that phase. The broad classifications of the operational phases are:

• Initial Construction—anticipated to occur for two years prior to the first receipt of waste. Large amounts of material are excavated from the landfill footprint and stored in the borrow areas during this phase.

• Startup Operations—during which MSW is received, deposited, and covered in the portion of the lower canyon that has been prepared for the receipt of waste (by installation of a clay liner) while construction continues and additional large amounts of material are excavated from other areas of the landfill footprint and stored in the



borrow areas. This is expected to occur in the first two years following the first receipt of MSW. During all or part of this period, depending on the waste receipt rate, there is no operation of a landfill gas collection and control system.

• Normal Operation—during which MSW is routinely received, deposited, and covered. There may be additional excavation of the canyon footprint during this period but relatively much smaller than the excavation in the earlier phases. The landfill gas collection and control system is operational during this phase.

• Closure—during which a final cover is placed on the landfill which will require approximately one year to complete.

• Post-Closure Maintenance—maintenance of final cover and vegetation, and continued operation of the landfill gas collection and control system.

This engineering evaluation covers the first four stages above. For the post-closure phase, the proposed permit conditions will remain in force after closure (emissions of PM10 and PM2.5 are much reduced and emissions of all other pollutants gradually decline over time during this phase) until the District determines that the landfill gas (LFG) emissions have reached insignificant levels. The District notes that it currently requires operation of a landfill gas collection and control system for a landfill that had received about 2,000,000 tons of waste during its lifetime 55 years after its closure in 1958 since there are still significant amounts of landfill gas being generated.

Regarding the initial construction phase, it should be noted that the District does not typically evaluate or regulate through permit conditions construction activities. However, the District is doing so in this case because the District has determined that the construction phase is actually producing a product—a Class III municipal solid waste landfill. Emissions from certain activities, for example construction of the paved main entrance road and bridge over the San Luis Rey River entering the facility, most of the construction on the paved portion of the ancillary facilities, construction of the relocated local serving utility power pole pads, demolition activities that occur outside of the landfill footprint, and mitigation of biological impacts in accordance with the EIR that occur outside the landfill footprint, are excluded from the evaluation because such activities would potentially be common to any facility being constructed.

Landfill Gas (LFG) Once the waste is deposited in the landfill an anaerobic environment is generally created within the waste within a short period of time. In this environment, microbes in the waste anaerobically decompose the waste ultimately producing methane and carbon dioxide, which raises the pressure inside the landfill. If uncontrolled, the generated gas escapes from the surface of the landfill as fugitive landfill gas or migrates underground carrying with it VOCs and TACs. To mitigate the air quality impacts from this gas, an active landfill gas collection and control system (LFGCCS) is required which consists of either vertical or horizontal wells placed in the buried waste to collect the generated gas by applying a vacuum to the waste and then route the collected gas to a control system, in this case a flare. However, no gas collection system is perfect. The applicant has proposed designing a landfill gas collection



system that will collect a minimum of 90% of the gas produced from waste that has been buried for more than six months. The reminder of the gas will escape as fugitive LFG emissions.

Flare Emissions The emissions of pollutants contained in the landfill gas that has been collected by the LFGCCS are controlled by combusting the collected gas in a flare. This combustion process generates additional pollutants (NOx, CO, SOx, TACs, PM10, and PM2.5) that were not present in the landfill gas (there are small amounts of CO in landfill gas). Additional emissions occur because the VOCs and TACs that are constituents of the LFG are not completely destroyed in the flare.

Fugitive Dust Landfills are also the source fugitive dust emissions. Landfill dust generating activities include, but are not limited to, the following activities:

• Transport of materials over paved and unpaved haul roads. • Wind-driven fugitive dust from disturbed areas, including, but not limited to, borrow

areas, silt basins, and the landfill footprint; • Earthmoving operations; • Rock crushing; • Transport, stacking, loading, and unloading of bulk materials, solid waste, alternative

cover materials, beneficial reuse materials, or landfill construction material; • Landfill construction; • Construction of landfill monitoring wells of any type; • Construction of landfill gas collection wells; • Borrow area operations; • Silt basin operations; • Drilling; and • Blasting.

The dust contains PM10 and PM2.5 and TACs, toxic metals and silica.

CAPACITY, OPERATION, AND THROUGHPUT LIMITS ON POTENTIAL EMISSIONS The Authority to Construct proposed conditions impose various capacity and throughput limits. These limits are imposed to limit the amount of toxic air contaminants, VOCs, and other pollutants emitted from fugitive landfill gas and combustion of the collected landfill gas in the flare to levels consistent with the Health Risk Assessment (HRA), Air Quality Impact Assessment (AQIA), and the evaluation of applicability of other District rule requirements. Although some of these limits are the same as that in the Solid Waste Facility Permit., It should be noted that changing limits in the Authority to Construct is a separate process from changes to the Solid Waste Facility Permit. Hence, changes to the Solid Waste Facility Permit would not automatically reflected in the Authority to Construct.



Summary of Limits on Emissions Table III-1 summarizes the various factors limiting the facilities potential to emit.



Table III-1. Summary of Factors Limiting Emissions

Item Limita Units Limit Typeb Landfill Net Air Space 57,000,000 cubic yards PTE limitc Excavation 2,604,000 cubic yards/year PTE limitd Waste Accepted 1,000,000 tons per year PTE limitc,e Waste Accepted 5000 tons per day PTE limite Organic ADC Accepted 90,565 tons per year PTE limitc,e Organic ADC Accepted 295 tons per day PTE limite Waste Accepted before LFGCCS Operateskk 1,300,000 tons PTE limitc,f VOCs 49.5 tons per year PTE limitg Operations, Time of Day various N/A PTE limith Flare Station Fuel Flow 7250 wscfm PTE limiti Flare Station Heat Input 150 MMBtu/hr PTE limitj Flare

NMOC 20 ppmvd exhaust NSPS WWWk,f NMOC 99% reduction unitless TBACTl,f Methane 99% reduction unitless AB32 LFm NOx 0.025 lb/MMBtu BACTn,o,q CO 0.06 lb/MMBtu TBACTp,n,o,q VOC 0.006 lb/MMBtu TBACTn,q PM10 6 lb/MMwscf fuel TBACTq TRSr as H2S 150 ppmvd fuel BACTs,q

Vehicle Speed 15 mph TBACTt,f Paved Main Entrance Road, Silt Loading 0.4 g/m2 TBACTu Main Entrance Road, PMEIv 1 unitless PTE limitw Unpaved Haul Roads, PMEIv 1 unitless PTE limitw Chemically Stabilization Haul Roads Quarterlyx N/A PTE limitw,y Unstabilized Haul Roads, Watering Visibly moist N/A TBACTt,w,z Unpaved, Unstabilized Haul Road Lengths

Internal Waste 700 feet PTE limitw Fill Area Road 600 feet PTE limitw Daily Cover Road 400 feet PTE limitw BAA Road 400 feet PTE limitw BAB Road 400 feet PTE limitw BAB Road (Rock only) 200 feet PTE limitw Final Cover Road 400 feet PTE limitw

Unpaved travel areas, other vehicles 20% opacity unitless TBACTt,f Landfill dust generating activitiesaa,bb 10% opacity unitless TBACTt,f Disturbed areasdd Stabilized Variousee TBACTq,ff,gg High-wind eventhh 20% opacityii unitless Rule 50f Rock Crushing 760,000 tons per year PTE limitw Blasting

Frequency One per day per day PTE limitw Annual Frequency, Construction Phase 65 per year PTE limitw Annual Frequency, Normal Operations 22 per year PTE limitw BAA Not allowed N/A PTE limitw Location various feet PTE limitw,jj



Opacity 20% opacityii Unitless Rule 50f aIncludes work practices. bPotential to emit (PTE) limits, by themselves or in conjunction with other limits are to limit the project’s emissions, or location of emissions, of NOx, CO, VOCs, PM10/PM2.5, SOx, and TACs. Best Availble Control Technology (BACT) and Toxic Best Availble Control Technology (TBACT) are equipment or process specific limits applicable to criteria pollutants and TACs, respectively. Limits referencing specific rules address those rule requirements and may also serve as BACT or TBACT in some cases. cLimits landfill gas emissions and associated TACs. dLimit taken to avoid PSD applicability. eLimits fugitive dust from waste acceptance operations. fAlso TBACT. gLimit taken to avoid major source nonattainment NSR applicability. hLimit taken for AQIA fugitive dust purposes also limits HRA impacts from fugitive dust. Specific times are specified in the A/C. iLimits flare emissions of PM10, PM2.5, and SOx, TACs. jLimits flare emissions of NOx, CO, VOCs, and TACs formed in the flare. kPossibly most stringent VOC limit at very low methane concentration in fuel. lPossibly most stringent VOC limit at very low VOC concentration in fuel. mPursuant to state law 17 CCR §95460 to §95476—Methane Emissions from Municipal Solid Waste Landfills (AB32 LF). nBased on SCAQMD LAER/BACT. oGuaranteed by at least one manufacturer. pLimits combustion-by-product TAC formation in flare. qAchieved in practice in SCAQMD. rTotal reduced sulfur compounds (TRS). sBased on SCAQMD Rule 431.1. tAchieved in practice. uBased on PSD limits for haul roads with vehicles carrying materials for biofuel manufacturing. vParticulate Matter Emission Index (PMEI) calculated for individual haul roads based on road type and relative to the number of vehicles, vehicle weight, and number of wheels (when applicable) that was used to estimate maximum road emissions for the AQIA.. wLimit taken for AQIA fugitive dust purposes also limits HRA impacts from fugitive dust. xMore frequent application is required if recommended by manufacturer. Amount applied is maximum recommended by manufacturer for maintenance of road unless a lesser amount is authorized by the District. yTo achieve 97% control efficiency before consideration of vehicle speed limits. zTo achieve 97% control efficiency before consideration of vehicle speed limits. aaDust generating activities associated with landfill operations except for travel on roads and other surfaces. bbBlasting and wind driven-dust from disturbed areas are excluded. ccReserved. ddDisturbed areas are particularly subject to wind-blown dust. eeThere are several criteria for stabilization specified in the Authority.to Construct. ffApplies to wind-blown dust. ggBased on Maricopa County Rule 310, Fugitive Dust from Dust-Generating Operations and SCAQMD Rule 403, Fugitive Dust. hhDefined in the A/C. iiThree minutes out of every 60 minutes are excluded from this opacity standard. jjTheclosest distance for any blast to the Western, Northern, and Southern facility property boundaries, depending on the blast size, is specified in the A/C. kkLandfill gas collection and control system (LFGCCS)



IV. EMISSION ESTIMATES

LANDFILL GAS EMISSIONS

General Anaerobic decomposition of landfill waste generates large amounts of landfill gas composed primarily of methane and carbon dioxide and some nitrogen and hydrogen. The amounts of nitrogen and hydrogen are usually small but may be significant under certain conditions. The gas also potentially contains a wide variety of minor constituents some of which are toxic air pollutants (for example, benzene, vinyl chloride, arsenic compounds, and hydrogen sulfide). Although the concentrations of the minor constituents are generally small ranging from below detection levels, in the range of 0.1 part per million by volume (ppmv), up to a few 100’s of ppmv (e.g., hydrogen sulfide in some cases) the potential toxic health risks may be significant.

The quantity of landfill gas generated by anaerobic decomposition is primarily dependent upon the amount of waste deposited, the anaerobically degradable organic carbon (ANDOC) content of the waste and the waste age, pH, temperature, microbial populations, and moisture content. While several methods have been developed to estimate landfill gas generation rates, the most common method for regulatory purposes is the first-order-decay model (EPA 2005a and CARB 2009a).

Methane and Landfill Gas (LFG) Emission Calculation Methodology Methane Generation Rate. The estimate of uncontrolled methane emissions for this project is based on a modified first-order-decay model for methane generation. First-order-decay models assume that the amount of methane generation from the deposited waste decays exponentially with time after the waste is deposited with the possibility of a delay in the beginning of methane generation. If it is assumed there is no delay time for the beginning of gas generation, which gives a conservatively high estimate of the rate of gas generation for newly deposited waste, an approximate solution to this model on an annual basis for the rate of methane generation is:

𝑄𝐶𝐻4,𝑛 = 𝑘𝐿0�𝑀𝑖𝑒−𝑘(𝑛−𝑖+1)𝑛

𝑖=1

(1)

Where:

𝑄𝐶𝐻4,𝑛 is the annual volume of methane generated in the nth year (yr) after waste is first deposited from all the waste deposited since the beginning of waste deposition at District standard conditions of 68 ºF and 1.0 atmoshpere of pressure, in standard cubic feet (scf);

𝐿0 is the landfill gas generation potential, standard cubic feet of landfill gas generated per ton of waste, in standard cubic feet per ton (scf/ton);



𝑀𝑖 is the the annual waste deposition rate in the i’th year on a wet basis, in tons per year (tpy);

𝑘 is the landfill gas generation rate constant, yr-1;

𝑛 is the number of years since initial waste placement, yr

A more accurate equation that accounts for a potential delay before methane is generated and is based on monthly waste deposition is:

𝑄𝐶𝐻4,𝑛 = (𝑘/12)𝐿0�𝑈(𝑛 − 𝑖 − 𝑡𝑎𝑑) 𝑀𝑖𝑒−(𝑘/12)(𝑛−𝑖+0.5)

𝑛

𝑖=1

𝑈(𝑛 − 𝑖 − 𝑡𝑎𝑑) = 1; for 𝑛 − 𝑖 − 𝑡𝑎𝑑 ≥ 0 𝑈(𝑛 − 𝑖 − 𝑡𝑎𝑑) = 0; for 𝑛 − 𝑖 − 𝑡𝑎𝑑 < 0

(2)

Where:

𝑄𝐶𝐻4,𝑛 is the total volume of methane generated in the n’th month after waste is first received from all the waste deposited since the beginning of waste deposition, in scf;

𝑀𝑖 is the the monthly waste deposition rate in the i’th month on a wet basis, in tons per month (tons/mo);

𝑛 is the number of months since initial waste placement;

𝑡𝑎𝑑 is the the time delay until anerobic decomposition begins, months.

In the above equation, the waste for each month is assumed to be deposited in the middle of the month to minimize errors (the District estimates the error to be less than 0.1% versus an exact calculation with continuous waste deposition). The monthly calculation procedure is convenient for including the effects of delay in anerobic decomposition after waste deposition and the delay in effective landfill gas collection (see below), which are conveniently expressed in months.

Fugitive Methane Emission Rate. The fugitive methane emissions are those emissions that are not captured by the landfill gas collection and control system. The fugitive emissions can be calculated as:

𝑄𝐶𝐻4,𝑓𝑢𝑔,𝑛 = �[1 − 𝜂𝑈(𝑛 − 𝑖 − 𝑡𝑐𝑑)]𝑄𝐶𝐻4,𝑖

𝑛

𝑖=1

𝑈(𝑛 − 𝑖 − 𝑡𝑐𝑑) = 1; for 𝑛 − 𝑖 − 𝑡𝑐𝑑 ≥ 0 𝑈(𝑛 − 𝑖 − 𝑡𝑐𝑑) = 0; for 𝑛 − 𝑖 − 𝑡𝑐𝑑 < 0

(3)



Where: 𝑄𝐶𝐻4,𝑖 = (𝑘/12)𝐿0𝑈(𝑛 − 𝑖 − 𝑡𝑎𝑑)𝑀𝑖𝑒−(𝑘/12)(𝑛−𝑖+0.5) (4)

And:

𝑄𝐶𝐻4,𝑓𝑢𝑔,𝑛 is the total volume of fugitive methane emitted in the n’th month from all the waste deposited since the beginning of waste deposition, in scf;

𝜂 is the fractional gas collection system efficiency for the waste effectively subject to gas collection; and

𝑡𝑐𝑑 is the time delay before landfill gas generated by anaerobic decomposition is subject to effective capture by the gas collection and control system, months.

The annual, daily, and hourly fugitive methane emission rates are given by the following equations:

𝑄𝐶𝐻4,𝑓𝑢𝑔,𝑎 = � 𝑄𝐶𝐻4,𝑓𝑢𝑔,𝑖

𝑛

𝑖=𝑛−11

(4a)

𝑄𝐶𝐻4,𝑓𝑢𝑔,𝑑 = 𝑄𝐶𝐻4,𝑓𝑢𝑔,𝑛 30.417⁄ (4b) 𝑄𝐶𝐻4,𝑓𝑢𝑔,ℎ = 𝑄𝐶𝐻4,𝑓𝑢𝑔,𝑑 24⁄ (4c)

Where:

𝑄𝐶𝐻4,𝑓𝑢𝑔,𝑎 is the fugitive methane emission rate in the 12-month period ending in the n’th month, in scf/yr.

𝑄𝐶𝐻4,𝑓𝑢𝑔,𝑑 is the fugitive methane emission rate each day in the in the n’th month based on an average month of 30.417 days,in standard cubic feet per day (scf/dy).

𝑄𝐶𝐻4,𝑓𝑢𝑔,ℎ is the fugitive methane emission rate each hour in the in the n’th month, in standard cubic feet per hour (scf/hr).

Methane Collection Rate. The amount of methane collected by the landfill gas collection and control system is:

𝑄𝐶𝐻4,𝑐𝑜𝑙,𝑛 = 𝑄𝐶𝐻4,𝑛 − 𝑄𝐶𝐻4,𝑓𝑢𝑔,𝑛 (5)

Where:



𝑄𝐶𝐻4,𝑐𝑜𝑙,𝑛 is the amount of methane collected and sent to the flare or other landfill gas control device in the n’th month, in scf

The annual, daily, and hourly methane collection rates are given by the following equations:

𝑄𝐶𝐻4,𝑐𝑜𝑙,𝑎 = � 𝑄𝐶𝐻4,𝑐𝑜𝑙,𝑖

𝑛

𝑖=𝑛−11

(5a)

𝑄𝐶𝐻4,𝑐𝑜𝑙,𝑑 = 𝑄𝐶𝐻4,𝑐𝑜𝑙,𝑛 30.417⁄ (5b) 𝑄𝐶𝐻4,𝑐𝑜𝑙,ℎ = 𝑄𝐶𝐻4,𝑐𝑜𝑙,𝑑 24⁄ (5c)

Where:

𝑄𝐶𝐻4,𝑐𝑜𝑙,𝑎 is the collected methane in the 12-month period ending in the n’th month, in scf/yr.

𝑄𝐶𝐻4,𝑐𝑜𝑙,𝑑 is the collected methane each day in the in the n’th month, in scf/dy.

𝑄𝐶𝐻4,𝑐𝑜𝑙,ℎ is the collected methane each hour in the in the n’th month, in scf/dy.

Flare Heat Input Rate. The annual, daily, and hourly heat inputs rate can be calculated from the following equations

𝐻𝑓𝑙𝑎𝑟𝑒,𝑛 = 10−6ℎ𝐻𝐻𝑉 �459.7 + 60459.7 + 68

�𝑄𝐶𝐻4,𝑐𝑜𝑙,𝑛 (6)

𝐻𝑓𝑙𝑎𝑟𝑒,𝑎 = � 𝐻𝑓𝑙𝑎𝑟𝑒,𝑖

𝑛

𝑖=𝑛−11

(6a)

𝐻𝑓𝑙𝑎𝑟𝑒,𝑑 = 𝐻𝑓𝑙𝑎𝑟𝑒,𝑛 30.417⁄ (6b) 𝐻𝑓𝑙𝑎𝑟𝑒,ℎ = 𝐻𝑓𝑙𝑎𝑟𝑒,𝑑 24⁄ (6c)

Where:

𝐻𝑓𝑙𝑎𝑟𝑒,𝑛 is the total heat input to the flare in the n’th month, million British thermal units per month (MMBtu/mo);

ℎ𝐻𝐻𝑉 is the higher heating volume of methane at 60 F and 1 atmosphere, in Btu/scf, which is equal to 1010;



𝐻𝑓𝑙𝑎𝑟𝑒,𝑎 is the total heat input to the flare in the 12-month period ending in the n’th month, MMBtu/yr;

𝐻𝑓𝑙𝑎𝑟𝑒,𝑑 is the total heat input to the flare each day in the in the n’th month, MMBtu/dy; and

𝐻𝑓𝑙𝑎𝑟𝑒,ℎ is the total heat input to the flare each hour in the in the n’th month, MMBtu/hr.

Fugitive Landfill Gas Emissions and Collected Landfill Gas. Monthly, annual, daily and hourly fugitive landfill gas emission rates and the landfill gas collection rate, excluding air infiltration from the collection process, can be calculated from the fugitive methane emissions and the amount of methane collected by dividing the corresponding monthly, annual, daily and hourly fugitive methane emission rate or methane collection rate by the concentration of methane in the fugitive landfill gas. For example,

𝑄𝐿𝐹𝐺,𝑓𝑢𝑔,𝑛 =100𝑄𝐶𝐻4,𝑓𝑢𝑔,𝑛

𝐶𝐶𝐻4,𝑛 (7)

𝑄𝐿𝐹𝐺,𝑐𝑜𝑙,𝑛 =100𝑄𝐶𝐻4,𝑐𝑜𝑙,𝑛

𝐶𝐶𝐻4,𝑛 (8)

Where:

𝑄𝐿𝐹𝐺,𝑓𝑢𝑔,𝑛 and is the total volume of fugitive landfill gas emission rate in the n’th month after waste is first received, in scf/mo;

𝑄𝐿𝐹𝐺,𝑐𝑜𝑙,𝑛 is the total volume of landfill gas collected in the n’th month after waste is first received, excluding air infiltration from the collection process, in scf/mo

𝐶𝐶𝐻4,𝑛 is the methane concentration in the fugitive landfill gas expressed, in percent;

Emission Calculation Procedure. Annual, daily, and hourly emissions of VOCs and toxic air pollutants in the landfill gas are calculated by multiplying an emission factor expressed in pounds per million standard cubic feet times the applicable fugitive landfill gas emission rate. For example:

𝐸𝐿𝐹𝐺,𝑓𝑢𝑔,𝑎,𝑖 = 10−6𝐸𝐹𝐿𝐹𝐺,𝑎,𝑖𝑄𝐿𝐹𝐺,𝑓𝑢𝑔,𝑎 (9)

Where:

𝐸𝐿𝐹𝐺,𝑓𝑢𝑔,𝑎,𝑖 is the annual emission rate of the i’th landfill gas species in pounds per year (lb/yr);



𝐸𝐹𝐿𝐹𝐺,𝑎,𝑖 is the emission factor for the i’th landfill gas species for purposes of estimating annual emissions, in pounds per million standard cubic feet (lb/MMscf); and

𝑄𝐿𝐹𝐺,𝑓𝑢𝑔,𝑎 is the emission rate of fugitive landfill gas, in scf/yr

Methane and Landfill Gas Emission Estimation Parameters—Normal Operations. The parameters used to estimate methane and landfill gas emissions after the landfill gas system is operational are listed in Table IV-1 and discussed further below.

Table IV-1. Normal Operation Methane and Landfill Gas Emission Estimation Parameters

Parameter Value Basis

𝑘, yr-1 0.02 Standard value for areas with less than 20 inches of rain per year.

𝐿0, scf/ton 2377 Derived from ARB default for CA landfill gas emission calculation

𝑡𝑎𝑑, months 0 No delay provides a conservative upper estimate of emissions.

𝑡𝑐𝑑, months 6 Landfill Gas Collection System Design Requirement

𝜂 0.9 Landfill Gas Collection System Design Requirement

𝐶𝐶𝐻4,𝑛, % 54.5 Analysis of District and SCAQMD landfill gas sample source test reports

𝑀𝑖, tons/month 90,880 Permit limits

Methane Generation Potential. Table IV-2 shows the methane generation potential from various regulatory sources. The District has concluded that the most representative value for estimating the future methane generation is that derived from the California Air Resources Board’s (CARB’s) value for California’s waste composition in CARB’s latest greenhouse gas emission inventory tool (CARB 2011a), which is based on a recent analysis of the California MSW stream composition carried out by the California Integrated Waste Management Board (now CalRecycle). This predicts significantly lower fugitive LFG emission rates than the those in the application, which was submitted in 2007, prior to CARB’s promulgation of its greenhouse gas regulation to control methane emissions from LFG. The reason for the lower value is that since the late 1990’s the amount of anaerobically degradable organic carbon (ANDOC) in California MSW has declined significantly, particularly ANDOC from paper, because of California’s aggressive recycling program and is now significantly different than the national average has shown in Table IV-3.



Table IV-2. Methane and Landfill Gas Generation Potential, Default Parametersd

Source L0, scff

CH4/ton

Default CH4,

%

Default Balance Gasesa,

% 𝒕𝒂𝒅,

months LFG,

scf/ton This Engineering Evaluation, Normal Operations

2377d 54.5 45.5c 0 4360

ARB, 2011 2418 50 50 6 4835 District Emission Inventory, 1998 4005 50 50 0 8009

Proposed AP-42, EPA, 2008 4095 50 50 0 8190

Gregory Canyon Application, 2007 3524 44 N/A 0 8009

AP-42, EPA, 1993 3938 50 50 0 7875 AP-42, EPA, 1998 3150 55 45b 0 5727 LandGem Model, EPA, 2005

NSPS Subpart WWW Purposes 5355 50 50 0 10710

Emission Inventory Purposes 3150 50 50 0 6300

District Emission Inventory, 1998 4005 50 50 0 8009 aExcept as noted all balance gases are CO2. bBalance gases are 40% CO2 and 5% nitrogen. cBalance gases are about 42.5% CO2 and 3% nitrogen. dBased on CARB’s anaerobically degradable organic carbon fractions for MSW and green waste assuming 91.7% MSW and 8.3% green waste as alternative daily cover (ADC) for the facility based on the proposed A/C limits. eBased on CARB’s anaerobically degradable organic carbon fractions for MSW only—ARB procedure calculates methane generation from ADC separately.

fStandard conditions are 68 ºF and 1.0 atmosphere, all L0 values have been corrected to those conditions (ARB uses 60 ºF and EPA 77 ºF as standard conditions for methane generation).



Table IV-3. Anaerobically Degradable Organic Carbon Portion of MSW

Year California EPA 1960

10.45%

1970

10.44% 1980

10.34%

1990

11.02% 1995

11.62%

1999 (CA), 2000 (EPA) 8.42% 11.39% 2004 7.45% 10.92% 2008 7.52% 10.41%

Methane Concentration in Fugitive Landfill Gas. The usual assumption that the anerobically generated landfill gas is composed of equal amounts of methane and carbon dioxide is based on the overall chemical reaction for theoretical anaerobic decomposition of a pure carbohydrate such as glucose:

C6H12O6 → 3CH4 + 3CO2

However, for LFG, the methane concentration is usually greater than the carbon dioxide concentration because some of the carbon dioxide is dissolved in the landfill leachate or condensate (Freed et al. 2006). Hence, the above assumption likely overestimates LFG generation relative to methane. The District estimates that the methane concentration in fugitive landfill gas in Southern California is about 54.5% based on an analysis of reported landfill gas methane concentrations from landfill gas collection systems from numerous measurements in SCAQMD and San Diego County corrected for air infiltration using argon as a surrogate for air. This indicates that the usual assumption overestimates fugitive landfill gas emissions by about 10%.

Monthly Waste Acceptance Rate. The District considers any organic material used as alternative daily cover (ADC) also subject to anaerobic decomposition. Therefore, any organic alternative daily cover, typically green waste (grass, leaves, branches) as PGM, is included in the waste deposited when estimating emissions. Based on the most recent MSW composition reported in CARB’s greenhouse gas calculation tool and CARB’s assumed composition of green waste used for ADC (50% grass, 25% leaves, and 25% branches) the anaerobically degradable organic carbon content of MSW is about 7.5% and that of green waste used for ADC about 6.2%. The ANDOC for another common ADC in San Diego, dewatered municipal sewage sludge, is about 5%. The emissions from the ADC are implicitly included in the methane generation rate in these calculations since the L0 used assumes that 8.3% of the material deposited in the landfill is green waste as ADC based on the proposed A/C limits on the annual amount of waste that can be deposited.



Time Delay Until Anaerobic Methane Generation. The generally accepted basic phases of waste degradation in a landfill are an initial aerobic phase in which the oxygen in the waste is consumed and carbon dioxide produced; an anaerobic acidgenosis phase in which organic acids, alcohols, carbon dioxide, and hydrogen are produced; followed by an anaerobic methane generation stage in which methane and carbon dioxide are produced. In practice these phases overlap in the waste and, in an active landfill, different phases are dominant throughout different regions of the deposited waste depending on the age and micro-environment of the waste.

The delay until anaerobic methane generation varies greatly depending on the waste conditions, six months is the commonly accept average time delay used in their greenhouse gas calculation methodologies (ARB 2009a and EPA 2008). However, under ideal laboratory conditions, methane generation can start in less than 30 days (Staley et al. 2006, Sponza and Agdag 2004). Moreover, in the aerobic phase and acidgenosis phase, gases are produced that can carry VOCs even if no methane is produced. In a recent laboratory study of decomposition of municipal solid waste in which methane and VOC emissions were tracked from the start of waste deposition (Staley et al. 2006), VOC emissions began earlier than methane emissions. In order to estimate the potential early release of VOC before methane generation during the aerobic and acidgenosis phases, the time delay to methane generation, and hence landfill gas generation, is set to zero.

Methane and Landfill Gas Emission Estimation Parameters—Startup. The startup period is the period before the initial landfill gas collection and control system becomes operational. The parameters used to estimate methane and landfill gas emissions before the landfill gas system is operational are listed in Table IV-4 and discussed below.

Table IV-4. Startup Methane and Landfill Gas Emission Estimation Parameters

Parameter Value Basis

𝑘, yr-1 0.02 Standard value for areas with less than 20 inches of rain per year.

𝐿0, scf/ton 2377 Derived from ARB default for CA landfill gas emission calculation.

𝑡𝑎𝑑, months 0 Lower limit. 𝑡𝑐𝑑, months N/A No control system operating. 𝜂 0 No control system operating.

𝐶𝐶𝐻4,𝑛 % 54.5 Analysis of District and SCAQMD landfill gas sample source test reports.

𝑀𝑖, tons/month 90,880 Permit limits.



FUGITIVE LANDFILL GAS CONSTITUENT EMISSION FACTORS

Fugitive Landfill Gas Constitent Emission Factors—General The concentration of VOC and toxic emissions in landfill gas, depends on, among other things, the composition of the waste stream and climatic factors which influence the internal temperature, moisture, etc. of the landfill. A general source of average landfill gas component concentrations on a national basis is EPA’s AP-42. However, the landfill emission factors in the approved version of AP-42 (EPA 1998) are based on source test information for landfill gas composition dating from the early 1990s and before. EPA has proposed a revision to these factors for facilities accepting waste after 1992 (EPA, 2008). However, these emission factors mostly come from source tests in the late 1990s. In California, there has been a large change in the general waste stream composition (as noted above) since the late 1990s. Also, since the 1990s, California state and local environmental regulations have resulted in a large decrease in the use of toxic materials, especially chlorinated solvents, that are potentially disposed of in landfills. In addition, the climate of Southern California is obviously more representative of the climate in San Diego than the climates in other parts of the county. For these reasons, District has concluded that the most representative emission factors for VOCs and toxic air contaminants are those based on relatively recent tests of landfill gas composition for Southern California landfills (those in the South Coast Air Quality Management District and San Diego County) when a sufficiently robust data set exists or it is the only information available.

The emission factor for VOCs and toxic air contaminants in landfill gas is calculated as follows:

𝐸𝐹𝐿𝐹𝐺,𝑖 =𝑀𝑊𝑖𝐶𝑖385.24

(10)

Where:

𝑀𝑊𝑖 is the molecular weight of the i’th species, pounds per pound mole (lb/lb mole); and

𝐶𝑖 is the concentration i’th species in the fugitive landfill gas, parts per million by volume, dry (ppmvd);

For purposes of estimating annual emissions for this application the concentrations used in equation 10 above are based on mean concentrations derived from the data corrected for air infiltration (see below). For purposes of estimating hourly emissions for this application, the concentrations used in the equation above are based on maximum concentrations in the data set most applicable to Southern California, corrected for air infiltration, unless the District was not able to find information for a specific compound.

Correction of Measured Concentrations for Air Infiltration. Fugitive landfill gas from anaerobic decomposition is assumed to contain no air since it originates from an anaerobic environment. However, samples of landfill gas are typically



drawn from active landfill collection systems, which operate under a vacuum and, hence, can draw in air through the landfill surface or through leaks in the portions of the gas collection system under negative pressure. Thus, the concentrations of species measured from landfill gas collection must be corrected for the presence of air in the sample to provide a representative emission factor for fugitive landfill gas, which is emitted through the surface of the landfill.

Correction methods for air infiltration are presented in AP-42 and in EPA Method 25C. In addition, a correction method based on the amount of argon in the sample can be derived similar to the one in EPA Method 25C. Of the potential correction methods, the District believes that the correction method provided in AP-42 underestimates the amount of air present in many cases. Therefore, all fugitive landfill gas concentration measurements, except those provided in AP-42, were corrected by the procedure in EPA Method 25C, which is based on the concentration of nitrogen in the sample, or, preferably in the District’s view, by a method that is based on the concentration of argon in the sample. Argon is an ideal indicator for air since it should not be produced in the landfill by microbial action, unlike nitrogen, and it is completely inert. For average or maximum concentrations reported in the proposed AP-42 revision that were used in the analysis, the concentrations were not corrected since they had already been corrected by the AP-42 method. The landfill gas concentrations from Southern California were corrected for air infiltration by argon, when available, and by the Method 25C procedure otherwise. Measurements without sufficient information to make an air infiltration correction were not used in the analysis.

Correction of VOC Emissions for Molecular Weight and Method Measurement Bias

There are two methods commonly used to measure the VOC concentration in landfill gas. One is are EPA Method 25C—Determination of Nonmethane Organic Compounds (NMOC) In Landfill Gases—which is used for federal regulatory purposes. In method 25C, the nonmethane organic compound (NMOC) concentration of the gas is determined by injecting a portion of the gas into a gas chromatographic column to separate the NMOC from carbon monoxide (CO), carbon dioxide (CO2), and methane (CH4); the NMOC are oxidized to CO2, reduced to CH4, and measured by a flame ionization detector (FID). In this manner, the variable response of the FID associated with different types of organics is eliminated. Another method is ASTM D 1945, which is used to determine the heat content of fuel by separating the fuel components on a gas chromatograph and measuring the concentration of compounds that elute in various carbon number ranges assuming the compounds are hydrocarbons (i.e., all compounds eluting before ethane are assumed to have two carbon atoms (C2), those eluting after ethane and before propane are considered to be C3, etc.) typically using a FID.

Both methods essentially measure the total number of carbon atoms in the fuel that are associated with NMOCs. In order to estimate the VOC mass emissions, the molecular weight associated with each carbon atom must be known and the contribution of exempt compounds such as acetone, which are not VOCs, must be subtracted. A commonly used assumption is that the molecular weight associated with each carbon atom corresponds to that for hexane, i.e., about 14.33 lb/(lb mole). The concentration of VOC is then reported “as



hexane.” Based on an analysis of two samples of landfill gas from San Diego landfills, the District estimates that the actual molecular weight may be as high as about 18 lb/(lb mole) because of the large amount of oxygenated compounds present, for example methanol and ethanol. In addition, the ASTM method underestimates the concentrations because the FID detector is not as sensitive to oxygenated species.

The table below shows the estimated correction factors based on an analysis of two samples of landfill gas from San Diego landfills by gas chromatography for exempt compounds and oxygenates (and some sulfur compounds). The compounds were identified by retention time and the concentrations either measured by calibration of the FID response for the compounds or based on the effect of the number of oxygen atoms in a compound on the FID response. The correction factors below represent the correction for molecular weight per carbon atom for Method 25C and the molecular weight and uncalibrated FID response for ASTM D 1945. The District also estimated the effect of oxygenated compounds not identified in analysis.

Table IV-5. Estimated Correction Factors for VOC Measurements

Sycamore, 7/24/12

Miramar, 8/9/12

Average

Estimated from Identified Compounds Method 25C 1.240996 1.153841 1.197418 ASTM D 1945 1.641222 1.428663 1.534943

Estimated Upper Limit Method 25C 1.255027 1.17489 1.214958 ASTM D 1945 1.679943 1.479448 1.579695

Method 25C Estimated Upper Limit/Estimated 1.011307 1.018242 1.014774

ASTM D 1945 Estimated Upper Limit/Determined 1.023592 1.035547 1.02957

Based on this analysis, the proposed A/C conditions require monitoring a sufficient number of species to provide a reliable estimate of the mass of VOC emissions. The District estimates that the species monitored capture about 98% of the total potential correction for Method 25C, the currently proposed overall VOC test method for landfill gas in the A/C. The VOC calculation procedure for monitoring VOC emissions includes a factor of 1.02 to correct for the potential underestimate.

VOC Emission Factor The applicant has proposed a VOC concentration of 595 ppmvd, as hexane, based on the currently approved version of AP-42 emission factors for landfills. However, the District finds that this emission factor likely underestimates potential emissions from Southern California landfills. The District analyzed the VOC concentrations reported in recent test (2007-2010) data from selected Southern California landfills and available VOC concentration measurements in San Diego. A summary is shown the table below.



Table IV-6. Southern California Landfills, VOC Concentrations in Landfill Gas

Landfill

Average VOC Concentration Corrrected for

Air Infiltration, ppmvd as

hexane

Average VOC Concentration Provisionally Corrected for Test Method

Bias, ppmvd as hexane

No. Data Points

Bradley 1696 2604 16 Calabasas 734 1127 4 Chiquita Cyn 1574 2417 2 Colton 1214 1864 2 El Sobrante 2665 4091 3 Olinda Alpha 239 367 16 Puente Hills 831 1276 5 Sunshine Cyn 1398 2146 16 Miramar 322 460 2 Otay 797 1223 4 Sycamore 1369 2214 10 Average of Individual Landfill Averages 1167 1799 11 Southern California Average 1167 1805 78 Only data with sufficient information provided to correct for air infiltration were included in the analysis. The concentrations were also corrected for potential test method bias based on the estimated correction for individual landfills when site-specific information was available (Sycamore and Miramar) and using the average correction factor for identified compounds from Table IV-5 above for other landfills. When the test method was unknown (most of the SCAQMD landfills measurements) the correction factor applicable to ASTM D 1945 was used to provide a conservative upper estimate of the VOC concentration.

Based on this analysis, a VOC concentration of 1800 ppmvd as hexane was determined to be the most representative concentration to use for estimating the potential to emit. The District is still investigating the appropriate correction factor for the test methods and the correction factors may be revised based on additional information or a refined analysis.

Toxic Air Contaminants Emission Factors—District Supplemental Analysis Organic Toxic Air Contaminants. The District Emission Inventory Default values for organic TAC constituents of LFG are from AP-42 which was most recently updated in September, 1997, and are based on data collected by EPA in the early 1990s. A t t h e t i m e , local test results support the EPA values. However, these emission factors are now out of date. Therefore, annual and maximum hourly emission factors in the District’s supplemental HRA analysis for toxic organic toxic air contaminants are based on averages or



maximums of proposed revised AP-42 emission factors and/or the average of emission factors from an analysis of recent test (2007-2010) data from selected Southern California landfills.

For the annual emission factors, if there was a significant difference between the average of the Southern California data and proposed revised AP-42 data, the Southern California data was preferentially used since the District believes it is more representative of landfills in Southern California. If there was no significant difference, the Southern California data and the proposed revised AP-42 data were averaged together to provide the annual emission factor. It should be noted that the Southern California data was corrected for air intrusion by the more conservative nitrogen/argon method than the AP-42 data.

For maximum hourly emissions, the maximum emission factor from the Southern California data was used preferentially if available. Otherwise the maximum emission factor from the proposed revision to AP-42 was used. It should be noted that for HRA purposes, using the maximum value for all the species is generally overly conservative since it is very unlikely that all the species will be at their maximum value at the same time. However, in this case, the acute risk, which is based on maximum hourly TAC emissions, from the landfill gas is almost entirely due to one compound—hydrogen sulfide—with some additional contribution from arsine. Using the overly conservative maximum values for the other TACs, which was done for simplicity, does not affect the result significantly.

Some specific issues with the organic toxic air contaminant emission factors are discussed below:

Epichlorohydrin. This compound is not usually considered to be a significant constituent of landfill gas. A test at one San Diego landfill in 2001 indicated about 10 ppmv of this compound in the landfill gas. Analysis of gas chromatograms of landfill gas fuel from two landfills (one of which was the same landfill as tested in 2001) in 2012 did not rule out or confirm the presence of epichlorohydrin. The compound, which is very reactive, did not give a signal on the District’s gas chromatograph and elutes very close to other peaks (ethyl propionate and propyl acetate) in an independent laboratory’s chromatograph. Preliminarily, for the purposes of this proposed Authority to Construct, the District has retained epichlorohydrin in the supplemental HRA using an average of the 2001 source test result and an estimate from the recent gas chromatograph results. However, epichorohydrin was reported as not detected using EPA Method TO-15 and gas chromatography with mass spectrometric detection in the preliminary results from another recent source test of the same landfill where the results indicated it was present in 2001. The District may revise this emission factor as additional information becomes available.

Benzene, Toluene, Xylene, and Ethylbenzene. The benzene average for Southern California was significantly impacted by the a series of very high benzene measurements in fuel analysis of landfill gas being combusted in turbines and reciprocating engines (up to about 50 ppmv) at two San Diego landfills in 2011-2012. The benzene levels have since returned to levels more consistent with the Southern California average. Additionally, the levels of toluene, xylene, and ethylbenzene were also elevated above expected levels. Preliminarily,



this data has been retained in the data set used to determine the emission factors. However, the District believes the abnormally high levels may have been the result of inadvertent use of gasoline contaminated imported soil used as cover material (the concentration of 2,2,4-trimethylpentane, a gasoline surrogate, was also elevated when measured), which may not be representative of normal operations. The District may revise these emission factors as additional information becomes available.

Hydrogen Sulfide. The annual hydrogen sulfide emissions were based on the average of the recent source test (2007-2010) data from selected Southern California landfills. For the maximum hourly emissions, the value was based on an analysis of two landfills that had the highest hydrogen sulfide emission factors (after correction for air intrusion) in the Southern California test data set. An examination of two-years of quarterly measurements from four landfill gas collection system header lines at each landfill showed that, at each landfill, two of the header lines had consistently much higher values than the other two lines. Since the flow rates in each of the lines are not known by the District, to form conservatively high landfill-wide average, the two highest values at each landfill for each quarter were averaged. The highest of these eight landfill-wide averages was used as the maximum hourly emission factor.

Ammonia. The ammonia emission factor was calculated by assuming all the NOx emitted in the flare was from ammonia in the landfill gas based on a NOx emission factor of 0.025 lb/MMBtu, the BACT limit.

Volatile Metal and Metalloid Emission Factors. Mercury is volatile as the elemental metal at room temperature and is a known constituent of landfill gas (EPA 2008) although reduction of its use in consumer products and restrictions on its disposal in landfills is likely reducing its emissions. Other potentially toxic metals are known to be emitted as volatile metal compounds in the natural environment such as hydrothermal pools and soil—especially under anaerobic conditions such as those that exist in a landfill (Mestrot et al. 2011, Meyer et al. 2007, Planer-Friedrich and Merkel 2006, Feldmann 2003). In fact, many volatile metals have been directly detected and measured in landfill gas including arsenic (DTSC 2009a, Pinel-Raffaitin et a. 2007, Feldmann 2003, Suwannee 2002); nickel and lead (DTSC 2009a, Feldmann 2003); phosphorous (DTSC 2009a, Roels and Verstraete 2004)and cadmium, chromium, copper, manganese, selenium, and vanadium (DTSC 2009a). In addition, toxic metals have been measured in the exhaust of external combustion devices (DTSC 2009b, EPA 2007) burning landfill gas. A major mechanism for the volatilization of metals is alkylation and hydridization of metals under anaerobic conditions (Mason 2011, Meyer et al. 2007, Craig and Jenkins 2004, Michalke et al. 2000) by micro-organisms.

Although there has been direct measurement of metals in the landfill gas of a Southern California landfill (DTSC 2009a), this was not used in determining emission factors because the source test report indicated that the test method used, which was developed for measuring metals in combustion equipment exhaust, likely was biased low when measuring metals in landfill gas. Instead, the concentration of metals in the landfill gas was derived from measurements of metals in the exhaust of external combustion devices (boilers and flares) using landfill gas as a fuel (DTSC 2009b, EPA 2007) one of which was from a source test at



the same landfill where direct measurements of metals in the landfill gas occurred (DTSC 2009a). In the case of mercury, these results were averaged with the propsed revised AP-42 emission factor for total mercury (i.e., speciation of mercury into elemental and alkyl mercury compounds was not considered).

Some specific issues with the metal and metalloid emission factors and their use in the HRA are discussed below.

Arsenic. The only likely volatile form of arsenic with approve health risk values is arsine. In the landfill gas, arsine and alkyl arsines (Feldmann 2003, Michalke et al. 2000) have been detected. The alkyl arsines do not have any health risk values and would not be considered in the HRA. There seems to be limited data on the quantitative speciation of the various potential volatile arsenic species. The only arsenic species observed was trimethyl arsine (Khoury et al. 2008) in an analysis of landfill gas from a Southern Californa landfill. In an analysis of volatile arsenic species emitted from anaerobic digestion of sewage sludge (Michalke et al. 2000), arsine was found to be about 15% of the volatile arsenic species (the rest were alkyl arsines, primarily trimethyl arsine). An analysis of landfill gas from a landfill in British Columbia found about 5% of the volatile arsenic species were arsine in both directly sampled landfill gas and landfill gas that had bubbled through a wetland, the rest being alkyl arsines (Feldmann 2003). However, much higher proportions of arsine in volatile arsenic emissions have been measured from soil incubation studies under anaerobic conditions (Mestrot et al. 2011, Meyer et al. 2007), Preliminarily, based on the above, all of the arsenic in the landfill gas was assumed to be arsine to provide a conservatively high estimate of health risk pending further investigation.

Cadmium and Lead. Cadmium and lead are assumed present in landfill gas as volatile alkyl compounds (Feldmann, 2003). However, because the standard HRA procedures only consider inorganic lead, lead is not considered present in the fugitive landfill gas for purposes of the HRA. However, since standard HRA procedures do not provide for separating inorganic and organic cadmium, all cadmium in the LFG was considered with same health risk values as elemental cadmium in the HRA.

Copper. Volatile copper compounds have been detected in large amounts from natural sources (Friedrich and Merkel 2006). To the District’s knowledge, the volatile species have not been identified. However, since standard HRA procedures do not provide for separating inorganic and organic copper, all copper was considered with the same health risk values as elemental copper in the HRA.

Nickel, Manganese, and Vanadium. These metals are all known to for stable, volatile carbonyl compounds. Nickel carbonyl and other transition metal carbonyls (tungsten carbonyl and molybdenum carbonyl) have been observed in LFG (Feldmann, 2003). Hence, these metals are all assumed to be inorganic compounds for purposes of the HRA and evaluated accordingly.

Chromium. Chromium forms a stable, volatile carbonyl, Cr(CO)6. In this compound chromium is in the zero valence state. This is assumed to be the volatile species in landfill gas by analogy with other transition state metals such as nickel. Hexavalent chromium is



highly toxic. However, there are no approved health risk values for other forms of chromium. Because chromium is in the zero valence state in Cr(CO)6, the chromium in LFG does not contribute to the health risk assessment. However, a portion of the chromium in the landfill gas is assumed to be converted to hexavalent chromium during combustion and emitted from the flare (see below)

Selenium. To provide a conservatively high estimate of the health impacts, the selenium in the landfill gas is assumed to be both in a form subject chronic HRA (selenium and compounds) and also in the form subject to acute HRA (hydrogen selenide). Selenium is essentially being doubled counted for the purposes of the chronic and acute portions of the HRA.

Phosphorus. The District is only aware of one measurement of phosphine (as opposed to phosphorous, which has no HRA implications) in landfill gas (Roels and Verstraete 2004). It is unclear if other forms of volatile phosphorous compounds are present. Hence, all phosphorous in landfill gas was assumed to be phosphine to provide a conservatively high estimate of the health risk. The District notes that the measured levels of phosphine in the study from individual landfill wells at a French landfill were equivalent to about 5.6 x 10-4 lb/MMscf on average with a maximum of 2 x 10-3, which is in the same range as the emission factor used for phosphine in the HRA, 1.6 x 10-3.

Mercury. For purposes of this HRA, to provide a conservatively high estimate of health risk, all mercury in the landfill gas was assumed to be elemental mercury. Current HRA procedures do not consider alkyl mercury compounds in the risk assessment. Source tests (EPA 2008) indicate alkyl mercury may constitute a large part of the total mercury measured in landfill gas. The emission factor was based on an average of the proposed revised AP-42 emission factor and the values derived from external combustion equipment source tests used for the other metals.

Carbon Monoxide. The carbon monoxide emission factor from proposed revised AP-42 was used to estimate carbon monoxide emissions in fugitive landfill gas.

NOx, PM10, PM2.5, SOx. None or insignificant amounts of these criteria pollutants are expected in fugitive landfill gas.

Greenhouse Gas Emission Factors. For purposes of state law implemented by the District, 17 CCR §95460 to §95476—Methane Emissions from Municipal Solid Waste Landfills (AB32 LF), the only regulated substance is methane, which is calculated as above except that for purposes of implementation of AB32 LF the methane content of LFG is assumed to be 50% and there is assumed to be a six month delay time before methane generation begins. For estimating actual emissions the methane concentration is assumed to be the same as the default used for estimating landfill gas



emissions (see Table IV-4). A GHG warming potential of 21 was used to covert methane to CO2e.

Summary of Fugitive Landfill Gas Emission Factors Table IV-7 show a summary of the TAC and VOC emission factors(EFs) used in the District’s supplemental analysis.



Table IV-7. Fugitive Landfill Gas Emission Factors

Chemical Annuala EF,

lb/MMscf Basisb,c,d,e Hourlyf EF, lb/MMscf Basisb,c,d

Arsenic 0.00E+00 EPA&DTSC 0.00E+00 EPA&DTSC Beryllium 0.00E+00 EPA&DTSC 0.00E+00 EPA&DTSC Cadmium 4.61E-04 EPA&DTSC 1.00E-03 EPA&DTSC Chromium (Hexavalent) 0.00E+00 EPA&DTSC 0.00E+00 EPA&DTSC Copper 3.57E-03 EPA&DTSC 3.57E-03 EPA&DTSC Lead 0.00E+00 EPA&DTSC 0.00E+00 EPA&DTSC Manganese 6.01E-03 EPA&DTSC 1.09E-02 EPA&DTSC Nickel 1.21E-02 EPA&DTSC 3.94E-02 EPA&DTSC Selenium 6.26E-04 EPA&DTSC 6.26E-04 EPA&DTSC Vanadium 3.08E-05 EPA&DTSC 3.08E-05 EPA&DTSC Arsine 3.79E-03 EPA&DTSC 6.34E-03 EPA&DTSC Phosphine 1.63E-03 EPA&DTSC 1.63E-03 EPA&DTSC Hydrogen Selenide 6.41E-04 EPA&DTSC 6.41E-04 EPA&DTSC Acetaldehyde 0.257 AP-42&SoCal 1.753 SoCal Acrolein 0.000 N/A 0.000 N/A Acrylonitrile 0.006 AP-42&SoCal 0.023 SoCal Allyl Chloride 0.007 SoCal 0.007 SoCal Ammonia 5.078 Specialg 5.078 Specialg Benzene 0.730 AP-42&SoCal 11.692 SoCal Benzyl Chloride 0.050 SoCal 0.280 SoCal Butadiene, 1,3- 0.017 AP-42&SoCal 0.016 SoCal Carbon Disulfide 0.030 AP-42&SoCal 0.164 SoCal Carbon Tetrachloride 0.011 SoCal 0.073 SoCal Chlorobenzene 0.292 AP-42&SoCal 7.353 SoCal Chlorodifluoromethane 0.179 AP-42 0.312 AP-42 Chloroform 0.009 SoCal 0.057 SoCal p-Dichlorobenzene 0.345 AP-42&SoCal 0.299 SoCal 1,2-Dichloroethane 0.054 AP-42&SoCal 0.758 SoCal 1,1-Dichloroethane 0.046 SoCal 0.405 SoCal 1,4-Dioxane 0.034 SoCal 0.053 SoCal Epichlorohydrin 1.764 SoCal 3.519 SoCal Ethyl Benzene 2.277 AP-42&SoCal 17.105 SoCal Ethyl Chloride 0.451 AP-42&SoCal 0.063 SoCal 1,2-Ethylene Dibromide 0.020 SoCal 0.103 SoCal Formaldehyde 0.001 AP-42 0.002 AP-42 Hexane-N 0.654 AP-42&SoCal 0.653 SoCal Hydrogen Sulfide 7.899 SoCal 22.247 SoCal



Isopropyl Alcohol 11.420 SoCal 17.159 SoCal Mercury And Compounds (Inorganic) 9.17E-05

AP-42& EPA&DTSC 2.03E-04 AP-42

Methanol 7.712 SoCal 14.958 SoCal Methyl Bromide 0.007 AP-42&SoCal 0.014 SoCal Methyl Chloroform 0.013 SoCal 0.064 SoCal Methyl Ethyl Ketone 4.971 SoCal 7.015 SoCal Methyl Tert-Butyl Ether 0.076 SoCal 0.184 SoCal Methylene Chloride 0.214 SoCal 2.342 SoCal Naphthalene 0.036 AP-42 0.088 AP-42 Perchloroethylene 0.276 SoCal 1.367 SoCal Propylene 0.362 AP-42 0.524 AP-42 Styrene 0.252 SoCal 0.309 SoCal 1,1,2,2-Tetrachloroethane 0.090 AP-42&SoCal 0.030 SoCal Toluene 4.654 SoCal 45.638 SoCal 1,1,1-Trichloroethane 0.013 SoCal 0.064 SoCal 1,1,2-Trichloroethane 0.027 AP-42&SoCal 0.020 SoCal Trichloroethylene 0.503 AP-42&SoCal 61.985 SoCal Vinyl Acetate 0.048 AP-42&SoCal 0.007 SoCal Vinyl Chloride 0.106 SoCal 0.804 SoCal 1.1-Dichloroethylene 0.017 SoCal 0.373 SoCal Xylenes 4.542 SoCal 48.706 SoCal TOTAL TACs 55.6 AP-42&SoCal 274 SoCal CO 1.773 AP-42 5.676 AP-42 VOCs 402.65 SoCal 402.65 SoCal Methane 22635 SoCal 22635 SoCal

aBased on mean values. bEPA & DTSC indicates that the value is based on an average of source test results for external combustion devices (DTSC 2009b, EPA 2007). cSoCal indicates that the value is based on average source test results landfill gas in the SCAQMD and San Diego. dAP-42 indicates that the value is based on EPA’s proposed revision to AP-42 for landfills (EPA 2008). eAP-42 & SoCal indicates that the value is based on an average of source test results. fBased on maximum values. gBased on maximum NOx emissions allowed by flare assuming all NOx converted to ammonia.



LANDFILL GAS FLARE EMISSION FACTORS (EFS)

Criteria Pollutants. The emissions of NOx, CO, VOC, PM10, and SOx are calculated based on the applicable TBACT or BACT limits (see Table III-1). For SOx, the emissions were calculated based on the total reduced sulfur (TRS) as H2S allowed in the inlet fuel:

𝐸𝐹𝑆𝑂𝑥 =(64)(150)

385.24= 24.92 lb/MMscf (11)

Land Fill Gas Constituent Emission Factors Organic Landfill Gas Constituents. Emission factors for organic landfill gas constituents were calculated assuming a 99% destruction efficiency, the minimum allowed destruction efficiency in the permit. In cases, where the landfill gas constituent is also a combustion by product (for example, benzene) the emissions from the landfill gas after the 99% reduction were added to the combustion-by-product emissions.

Organometallic and Inorganic Landfill Gas Consituents. All organometallic compounds were considered to be converted to their inorganic form in the flare and are discussed under the combustion-by-product section below. A 99% control factor was assumed for all other inorganic landfill gas constituents.

Combustion-by-Product Emission Factors Combustion-by-product pollutants from combustion are those pollutants that are not necessarily in the fuel but are formed in the combustion process.

Organic Combustion-By-Product Emission Factors. Except for dioxins (see below), emission factors for organic toxic air contaminants potentially formed in the combustion process are based on the default values of the SCAQMD supplemental emission factors for landfill-gas-fired flares for the state AB2588 (SCAQMD 2010) risk assessment process. The SCAQMD factors are expressed as lb/MMscf. For purposes of estimating emissions for the HRA for this project, they are expressed as lb/MMBtu by assuming a landfill gas methane content of 39%. The methane content is based on the average methane content by landfill (i.e. it is the average of the average value at each landfill) for the SCAQMD landfills in the 2007-2010 data for landfill gas composition. The average by landfill rather than the overall average for all the data combined, about 37% methane, which is used elsewhere in the analysis, was used because the data set appears to be over weighted by a large number of data points from two landfills with low methane content in the landfill gas and so the overall average is likely not representative of SCAQMD landfills in general. Because these are default factors, they were used to estimate both the annual and maximum hourly emissions.



Some key emission factors are further discussed further below:

Polycyclic Aromatic Hydrocarbons (PAHs). The applicant proposed using an unspeciated PAH emission factor, excluding naphthalene, of 0.0012 lb/MMscf. As noted above, the District has evaluated the application based on the SCAQMD default AB2588 EFs applicable to landfill gas fired flares, which has an emission factor, excluding naphthalene, of 0.003 lb/MMscf for unspeciated PAHs excluding naphthalene. This emission factor was recently used to evaluate a new landfill gas flare in SCAQMD (SCAQMD 2012). Because PAHs from the flares contribute a significant portion of the overall cancer risk the proposed permit conditions require periodic source testing to measure PAH emissions. Based on inspection of recent source tests for flares in the SCAQMD, it is likely this emission factor is conservatively high.

Polychlorinated-p-Dibenzodioxins (PCDD) and Polychlorinated Dibenzofurans (PCDF). The applicant proposed using 1.19 x 10-20 lb/MMscf as the emission factor for PCDD and PCDF. However, proposed AP-42 lists an emission factor of 4.2x10-7 lb/(MMscf of CH4) as unspeciated PCDD and PCDF compounds. Following standard HRA procedures, where all unspeciated PCDD and PCDFs are assumed to be 2,3,7,8-tetrachloro-p-dioxin, which has the highest cancer potency among the PCDD and PCDF, this value would significantly increase the cancer risk for the facility. However, the original landfill flare source test report upon which the proposed AP-42 value is based (EPA 2005b) did quantify the PCDD and PCDF congeners known to be toxic individually from the remaining PCDD and PCDF congeners, which were quantified as groups of congeners with the same number of chlorine atoms excluding the toxic congeners. Therefore, the District based the emission factor used in its supplemental HRA on the Toxic Equivalent Quantity (TEQ) of 4.2 x 10-9 lb/MMscf, for those individually quantified (many were not detected and conservatively quantified at the detection level) congeners with toxic risk values, or, equivalently, 4.16 x x 10-12 lb/MMBtu based on the heat input rate during the source test.

Metals and Metalloids. Metals and metalloid emissions from the flare are classified combustion by products in this analysis because they are assumed to be converted from an organic to an inorganic form in the flare. Exceptions such as nickel, which may already be in an inorganic form in the landfill gas are classified a combustion by product for convenience. As discussed above for landfill gas, metal emission factors were derived from source tests of external combustion devices burning landfill gas and expressed in the form of lb/MMBtu. All the metals and metalloids in the landfill gas were assumed to be converted to and emitted in an inorganic form for purposes of the HRA. There was no control factor assumed for the flare for metals and metalloids (see below for arsine and hydrogen selenide).

Chromium, Hexavalent. In accordance with standard District HRA policy, 5% of the chromium in the landfill gas was assumed to be converted to the toxic hexavalent form. The District policy is supported by equilibrium studies and measurements of chromium species in combustion (Linak and Wendt 1998, Linak and Wendt 1999).

Arsine. As discussed above under the fugitive landfill gas emission factors section, all arsenic in the landfill gas is assumed to be in the form of arsine for purposes of the HRA. As



with other metals and metalloids, all arsenic in ths form is considered to be converted to an inorganic form in the flare. However, some arsine emissions were also included in the HRA assuming a 99% reduction of the arsine by the flare. To the extent that this double counts the impacts from the various forms of arsenic, it provides a conservative overestimate of the health impacts.

Hyrdrogen Selenide. Hydrogen selenide was treated as arsine in that the HRA assumed all the selenium in the LFG was converted to the inorganic form but an additional impact from hydrogen selenide was included assuming 99% reduction in the flare.

Summary of Combustion-by-Product Emission Factors. Table IV-7 summarizes the combustion-by-product emission factors used in the evaluation.



Table IV-7. Flare Emission Factors forTAC Combustion-by-Products

Chemical Annuala EF, lb/MMBtu Basisb,c,d

Hourlye EF,

lb/MMBtu Basisb,c,d Arsenic 6.73E-06 EPA&DTSC 1.12E-05 EPA&DTSC Beryllium 2.73E-08 EPA&DTSC 2.73E-08 EPA&DTSC Cadmium 8.50E-07 EPA&DTSC 1.85E-06 EPA&DTSC Chromium (Hexavalent) 3.75E-07 EPA&DTSC 8.23E-07 EPA&DTSC Copper 6.58E-06 EPA&DTSC 6.58E-06 EPA&DTSC Lead 3.61E-06 EPA&DTSC 8.90E-06 EPA&DTSC Manganese 1.11E-05 EPA&DTSC 2.01E-05 EPA&DTSC Nickel 2.23E-05 EPA&DTSC 7.27E-05 EPA&DTSC Selenium 1.15E-06 EPA&DTSC 1.15E-06 EPA&DTSC Vanadium 5.68E-08 EPA&DTSC 5.68E-08 EPA&DTSC Arsine Phosphine Hydrogen Selenide Acetaldehyde 1.08E-04 SCAQMD 1.08E-04 SCAQMD Acrolein 2.52E-05 SCAQMD 2.52E-05 SCAQMD Acrylonitrile Allyl Chloride Ammonia Benzene 4.00E-04 SCAQMD 4.00E-04 SCAQMD Benzyl Chloride Butadiene, 1,3- Carbon Disulfide Carbon Tetrachloride Chlorobenzene Chlorodifluoromethane Chloroform p-Dichlorobenzene 1,2-Dichloroethane 1,1-Dichloroethane 1,4-Dioxane Epichlorohydrin Ethyl Benzene 3.64E-03 SCAQMD 3.64E-03 SCAQMD Ethyl Chloride 1,2-Ethylene Dibromide Formaldehyde 2.94E-03 SCAQMD 2.94E-03 SCAQMD Hexane-N 7.30E-05 SCAQMD 7.30E-05 SCAQMD



Hydrogen Sulfide Isopropyl Alcohol Mercury And Compounds (Inorganic) f 2.36E-7

AP-42& EPA&DTSC 5.24E-7

AP-42& EPA&DTSC

Methanol Methyl Bromide Methyl Chloroform Methyl Ethyl Ketone Methyl Tert-Butyl Ether Methylene Chloride Naphthalene 2.77E-05 SCAQMD 2.77E-05 SCAQMD Perchloroethylene Propylene Styrene 1,1,2,2-Tetrachloroethane Toluene 1.46E-04 SCAQMD 1.46E-04 SCAQMD 1,1,1-Trichloroethane 1,1,2-Trichloroethane Trichloroethylene Vinyl Acetate Vinyl Chloride 1.1-Dichloroethylene Xylenes 7.30E-05 SCAQMD 7.30E-05 SCAQMD PAH 7.56E-06 SCAQMD 7.56E-06 SCAQMD PCDD and PCDF 4.16E-12 EPA 2005 4.16E-12 EPA TOTAL TACs AP-42&SoCal 274 SoCal

aBased on mean values for metals and SCAQMD default factors for other compounds except PCDD and PCDF, which are based on the EPA source test. bEPA & DTSC indicates that the value is based on an average of source test results for external combustion devices (DTSC 2009b, EPA 2007). cSCAQMD indicates that the value is based on SCAQMD default emission factors (SCAQMD 2010). dEPA 2005 indicates that the value is based on the EPA source test of a landfill gas flare (EPA 2005b). eBased on maximum values for metals and SCAQMD default factors for other compounds except PCDD and PCDF, which are based on an EPA source test. fBecause the landfill gas constituent mercury emission factor is an average of the value for landfill gas value in proposed AP-42 and the external combustion device emission factors, the combustion-by-product emission factor was derived from the landfill gas constituent emission factor assuming 39% methane in the landfill gas. This was done because the methane flow rate and composition associated with the AP-42 values were not readily available. In the actual calculations the landfill gas constituent emission factor was used with a zero control efficiency assumed for the flare, which is equivalent.



Greenhouse Gases.

For purposes of state law implemented by the District, 17 CCR §95460 to §95476—Methane Emissions from Municipal Solid Waste Landfills (AB32 LF), the only regulated substance is methane. The methane destruction efficiency is assumed to be 99% as required by 17 CCR §95460 et seq. Standard greenhouse gas emission methodology was used to calculate the CO2e emissions from the flare, i.e., N2O as a combustion-by-product was included and the standard GHG warming potential factors used.

POTENTIAL TO EMIT—FUGITIVE LANDFILL GAS CONSTITUENTS

Introduction The emissions of the pollutants of concern in the fugitive landfill gas are directly proportional to the amount of fugitive landfill gas emitted. The maximum amount of fugitive landfill gas generated by anaerobic decomposition depends on the total amount of waste deposited in the landfill, the timing of the waste deposition, the parameters determining the amount of methane generation, and the amount of landfill gas generated that is collected and routed to the flare. The parameters for methane generation have been discussed above. The total potential amount of waste in the landfill is limited by the net air space available and the waste density, which in this case is 57,000,000 cubic yards (cy). The maximum landfill gas generation occurs at the fastest deposition rate. Slower rates of deposition result in lower emissions since waste deposited in the early years of operation has more time to decompose and less is available for decomposition in the peak year of gas emissions, which typically occurs in the last year of operation. Finally, the amount of fugitive landfill gas is directly proportional to one minus the control efficiency (expressed as a fraction).

Maximum Landfill Waste Capacity Air Utilization Factor (AUF). The amount of waste that can be placed in the landfill is ultimately limited by the available net air space and the density of the waste in the landfill. The applicant identified an expected waste-in-place density of 1350 (lb waste)/(cy of waste) in the JTD for the facility (JTD 2011a). To calculate the total cover material that would accompany the waste, the applicant assumed a 4:1 waste to cover ratio, by volume, to estimate the volume consumed by the cover. This combined with the waste density results in a maximum total volume of waste that could be placed in the landfill of 45,600,000 cy (JTD 2011a) or about 30.8 million tons of waste at the assumed 1350 lb/cy density, which was the estimate provided with the application. This estimate likely provides a conservatively low estimate of the life of landfill and the amount of trash received for purposes of solid waste permitting. However, it does not provide a reasonably conservative estimate for the potential to emit landfill gas, VOCs, and TACs.

The applicant anticipates actually achieving at least a 7.5:1 cover ratio (JTD 2011a), which would increase the amount of waste that could be placed in the landfill to about 34 million



tons. More significantly, although the applicant has identified the potential for up to 30% settlement of the landfill waste (JTD 2011a), which occurs from anaerobic decomposition and compression of the waste by the overlying waste mass, this was not accounted for in the potential amount of waste that could be received and placed in the landfill. To help evaluate the potential for settlement increasing the amount of waste in the landfill, the District requested and received from the applicant an estimate based on an air utilization factor (AUF) of 1700 lb/(cy of net air space). Note that this is measure of how much waste can be placed in each cubic yard of net air space over the life of the landfill and differs from an in-place waste density which is the density of the waste when it is initially placed in the landfill.

Offsetting to some extent the potential underestimate of landfill waste capacity, the applicant used landfill gas generation parameters, which at the time of application submittal the District recommended, that the District has now concluded likely overestimate future landfill gas emissions (see above) based on more recent evidence. In addition, the District has concluded that an air utilization factor of 1700 lb/(cy of net air space) also likely overestimates the amount waste that can be placed in the landfill over the life of the landfill. A reasonably conservatively estimate the future maximum potential to emit landfill gas, emissions in this evaluation are calculated based on an average AUF of 1500 (lb waste)/(cy of net air space). This is in turn is based on a 5-year average of the AUF calculated from aerial surveys of an active San Diego landfill and a record of the waste accepted at that landfill (Sycamore Landfill JTD 2011). Although higher annual AUFs have been reported by Southern California landfills [up to about 1700 (lb waste)/(cy of net air space)], the District finds that a 5-year average is most representative of the AUF over the life of this landfill.

Based on these conclusions, the total amount of waste the facility can accept as currently proposed is about 43 million tons. This results in an estimated landfill lifetime of about 43 years at the maximum permitted waste acceptance rate of one million tons per year.

Rate of Waste Acceptance. The annual rate of waste acceptance and organic ADC acceptance was assumed to be the maximum allowed by the proposed Authority to Contruct Conditions, 1,000,000 and 90,565 tons per year, respectively.

Landfill Gas Collection Efficiency The proposed A/C requires the applicant to provide a design for an active landfill gas collection and control system that will achieve a 90% collection efficiency for the landfill gas from waste that has been in place for six months or more. At this collection efficiency only 10% of the gas emitted from the waste subject to control is emitted. The A/C also requires that the system be operational on or before 120 days after the date that the cumulative waste accepted is 1,300,000 tons. At the maximum waste and green waste for ADC acceptance rate, this would require the system to be operational about 19 months from the date waste is first accepted.

Achievable Collection Efficieny. For active landfill gas collection systems, the overall collection efficiency of the landfill gas collection and control system (LFGCCS), depends on the density of landfill gas wells, applied vacuum in those wells, the depth and roperties of the waste, the thickness and properties of the cover material, the location of the wells relative to



side slopes, the properties of the liner, and number, size, and location of cracks or holes in the cover material (Wang and Achari 2012). The amount of vacuum that can be applied is limited by the potential for air intrusion into the waste, which can result in excessive temperatures from oxidation of the waste disrupting methane generation and potentially resulting in landfill fires.

Based on a preliminary analysis of surface methane concentration measurements for monitoring VOC emissions, the District estimates the following control efficiencies at active San Diego landfills summarized in Table IV-8.

Table IV-8. Estimated Collection Efficiency of San Diego Landfills

Landfill Estimated Collection Efficiency Sycamore 81% Otay 90% Miramar Phase II 56%

Based on this estimate, the District finds that 90% control, as proposed by the applicant, is achievable with the proper combination of factors such as well density and placement, vacuum applied, etc. Appendix A discusses the basis for these estimates and the monitoring fugitive methane emissions from which fugitive VOC emissions can also be monitored.

Delay in Installation and Operation of the LFGCCS. The LFCCS cannot begin operating until the system is installed and sufficient methane is generated to allow operation of the flare on a continuous or intermittent basis. If the LFGCCS was not installed for three years, the daily or hourly fugitive emissions would be nearly the same as at closure because 100% of landfill gas generated would be emitted instead of the approximately 12% at closure. Moreover, the same amount of emissions in the early period of operation may have increased health impacts since, in that period, the landfill gas emissions are focused in a much smaller area of the landfill (about 22 acres at the northern end of the landfill in the first year) than emissions in later years that are spread out over the entire 183 acre landfill.

The Authority to Construct requires the LFGCCS be operated by the time 1,500,000 tons of waste have been accepted to prevent excessive emissions in the early years of the landfill operation (see the Rule 1200 evaluation below).

Delay in Controlling Waste Deposited. The lag time in active collection being applied to waste that is already in place can have a significant effect on emissions because there is zero control efficiency for this portion of the waste. Even if the collection system achieves 90% collection efficiency for the portions of waste where the system is fully effective, the overall effective collection efficiency is less than 90% throughout the life of the landfill. For example, with the assumptions used in this evaluation for landfill gas generation (no delay in the beginning of landfill gas generation and a six month delay in collection for waste deposited) the overall collection efficiency on a monthly basis rises from about 61% immediately after the LFGCCS begins operating at 18 months to about 88% at closure. A 90% overall collection efficiency would be achieved six months after closure. If the control



system was only required to control waste that had been in place five years or longer the maximum allowed by federal regulations (40 CFR Part 60 Subpart WWW) the overall collection efficiency would only be about 75% at closure even if a 90% collection efficiency was achieved for the remainder of the waste.

Post Closure. The installation of the final cover on the landfill would likely result in a higher control efficiency after the installation is complete. EPA’s default control efficiency for closed landfills with a cover meeting standard regulatory requirements is 95% (EPA 40 CFR Part 98 Subpart HH, Table HH-3). But, the peak emissions still occur when the last waste is received.

Emissions from Fugitive Landfill Gas Table IV-9. Summarizes the parameters used to estimate the potential to emit fugitive landfill gas.

Table IV-9. Parameters Used to Estimate LFG Emissions

Parameter Value Waste acceptance rate, tpy 1,000,000 Other anaerobically decomposable material acceptance rate, tpy 90,595 Anaerobically decomposable material acceptance rate, tpy 1,090,595 Airspace Utilization Factor, lb waste buried/yd3 airspace consumed 1,500 Net airspace available, yd3 57,000,000 Number of operating years 42.75 Total waste received, tons 42,750,000 Methane generation decay constant, yr-1 0.02 Methane generation lag time, months 6 L0, ft3 CH4 per ton of waste @ 68 °F& 1 atm 2377 Methane concentration in fugitive LFG,% 54.5 Methane concentration in collected LFG,% 37 Expected LFG collection efficiency,% 90 Delay after waste deposition before LFG generated is collected, months 6 Delay before LFG collection system is installed, months 18

Landfill Gas Maximum Estimated Emissions Summary During Normal Operations The estimated amounts of fugitive and collected landfill gas (LFG) and methane (CH4) and the maximum estimated fugitive pollutant emissions during normal operations when the LFGCCS is operating are shown in Tables IV-10 and IV-11, respectively. Annual estimates are based on the maximum in any 12-month period and daily and hourly estimates are based on the maximum monthly emissions assuming continuous, constant generation and emission rates during the month. Each month is assumed to be 30.417 days long for purposes of calculating the daily and hourly emissions. More details on the toxic emissions on a species-by-species basis are presented in the HRA report.



Table IV-10. Estimated Maximums for Landfill Gas and Methane

Material 12-Month, MMscf/yr

Daily, MMscf/dy

Hourly, MMscf/hr

Flare Flows, scfm

CH4 Generation @68 °F 1483.4 4.081 1.701E-01 2834.3 LFG Generation w/o air @68 °F 2721.8 7.489 3.120E-01 5200.5 Fugitive CH4 @68 °F 171.2 0.472 1.966E-02 327.6 Fugitive LFG w/o air @68 °F 314.1 0.866 3.607E-02 601.1 Collected CH4 @68 °F 1321.8 3.637 1.515E-01 2525.5 Collected CH4, @ 60 °F 1301.7 3.582 1.492E-01 2487.2 Collected LFG w/o air @68 °F 2425.3 6.673 2.780E-01 4633.9 Collected LFG & air, @ 60 °F 3518.2 9.680 4.033E-01 6722.2 Collected LFG & air, wet @ 60 °F 3795.4 10.442 4.351E-01 7251.7

Flare Heat Input Annual, MMBtu/yr

Daily, MMBtu/dy

Hourly, MMBtu/hr

1,315,000 3,617 151

Table IV-11. Estimated Maximums for Fugitive Landfill Gas Constituents

Pollutant 12-Month,

tons/yr Daily, lb/day Hourly, lb/hr VOC 63.2 348.5 14.52 CO 0.3 4.913 0.20 TAC 8.7 236.9 9.870 GHG (CO2e) 74,843

Startup Emissions The estimated amounts of fugitive and collected landfill gas (LFG) and methane (CH4) and the maximum estimated fugitive pollutant emissions during startup operations before the LFGCCS is operating are shown in Tables IV-12 and IV-13, respectively. Obviously, there is no landfill gas collected during this period. However, the District estimates that when the flare system does begin operation at the end of startup period there will be about 5.62 MMBtu/hr of heat input to the flare, which is adequate to allow at least one manufacturer’s flare to operate and still meet the emission limits of the A/C.



Table IV-. Estimated Maximums Prior to Operation of the LFGCCS for Landfill Gas and Methane

Material 12-Month, MMscf/yr

Daily, MMscf/dy

Hourly, MMscf/hr

Flare Flows, scfm

CH4 Generation @68 °F 53.4 0.210 0.009 N/A LFG Generation w/o air @68 °F 98.0 0.385 0.016 N/A Fugitive CH4 @68 °F 53.4 0.210 0.009 N/A Fugitive LFG w/o air @68 °F 98.0 0.385 0.016 N/A

Table IV-13. Estimated Maximums Prior to Operation of the LFGCCS for Landfill Gas Constituents

Pollutant 12-Month,

tons/yr Daily, lb/day Hourly, lb/hr VOC 19.73 155.1 6.5 CO 0.09 2.2 0.1 TAC 2.72 105.4 4.4 GHG (CO2e) 23,350

It should be noted that, although the estimated maximum amount of landfill gas generated prior to operation of the LFGCCS is only about 3.5% of the estimated normal operation maximum, the estimated maximum pollutant emissions are about 30% and 45% of the normal operation maximums on an annual and daily (or hourly) basis, respectively, because there is no landfill gas collection or control.

FLARE EMISSIONS The estimated maximum flare emissions are shown in Table IV-14 below. To establish the project’s potential to emit, the maximum emissions are based on the lifetime maximum collected landfill gas being flared in an estimated 5–6 flares although this A/C is only for one flare. More details on the toxic emissions on a species-by-species basis are presented in the HRA report.



Table IV-14. Estimated Maximum Flare Emissions.

Pollutant Annual, tons/yr Daily, lb/day Hourly, lb/hr VOC 3.9 21.7 0.9 NOx 16.4 90.4 3.8 CO 39.4 217.0 9.0 PM10 11.4 62.7 2.6 SOx 43.8 241.2 10.1 TAC 5.9 32.5 1.4 GHG (CO2e) 8,124

TOTAL MAXIMUM FUGITIVE LANDFILL GAS CONSTITUENT AND FLARE EMISSIONS The estimated maximum emissions from fugitive landfill gas and the flare are shown in Table IV-15. As in the previous tables related to landfill gas, annual estimates are based on the maximum 12-month period and daily and hourly estimates are based on the maximum monthly emissions assuming continuous, constant generation and emission rates. Each month is assumed to be 30.417 days long for purposes of calculating the daily and hourly emissions. More details on the toxic emissions on a species-by-species basis are presented in the HRA report. Greenhouse gas emissions are only calculated on an annual basis since that is the only relevant period for regulatory purposes.

Table IV-15. Estimated Maximum Landfill Gas Associated Emissions

Pollutant Annual, tons/yr Daily, lb/day Hourly, lb/hr VOC 67.1 370.1 15.4 NOx 16.4 90.4 3.8 CO 39.7 218.4 9.1 PM10 11.4 62.7 2.6 SOx 43.8 241.2 10.1 TAC 14.6 395.8 16.5 GHG (CO2e) 82,885

ROAD FUGITIVE PARTICULATE EMISSIONS

Introduction On-site vehicle traffic on haul roads can produce a significant amount of particulate emissions by entrainment of dust from the surface of the roads that are being traveled. The dust is entrained by the forces generated by the tires of the vehicle and aerodynamic forces from the vehicle’s passage. An additional source of dust for open-topped vehicles is material blown from the load by a combination of the relative wind speed generated by the



vehicle’s speed and the ambient wind. The District uses Sections 13.2.1 (10/97 edition) and 13. 2.2 (1/95 edition) of AP-42 to estimate overall haul road particulate emissions from paved and unpaved surfaces, respectively. In general, the particulate emissions are expected to be directly related to the number of vehicle miles traveled, road surface silt conditions, vehicle speed, vehicle weight, and the number of wheels per vehicle. In addition, the road dust that is generated will contain trace amounts of several metals and minerals that are TACs. Although present at only low levels in the dust, the trace constituents can potentially have significant health impacts.

Basic Equations The basic equation used to estimate paved road fugitive dust emissions is:

𝐸(𝑃𝑀)𝑝𝑎𝑣 = 𝑘𝑝𝑎𝑣𝑁𝐿 �𝑠𝐿2�0.65

�𝑆

32.5� �𝑊3�1.5

�1 − 𝜂𝑝𝑎𝑣� (12)

This is the same as the District’s standard emission factor equation used for emission inventory estimates except for the inclusion of a factor to account for vehicle speed.

The equation used to estimate annual unpaved road fugitive dust emissions is the same as the District’s standard emission factor equation used for emission inventory estimates. The basic equation used to estimate annual emissions for unpaved roads is:

𝐸(𝑃𝑀)𝑢𝑛𝑝,𝑎𝑛 = 5.9𝑘𝑢𝑛𝑝𝑁𝐿 �𝑠

12� �

𝑆30� �𝑊3�0.7

�𝑤4�0.5�

365 − 𝑝365

� �1 − 𝜂𝑢𝑛𝑝� (13)

The basic equation used to estimate potential hourly and daily fugitive dust emissions for unpaved roads is the same as the annual equation except the factor that estimates the reduction in emissions from annual precipitation was excluded. The equation is:

𝐸(𝑃𝑀)𝑢𝑛𝑝,ℎ𝑑 = 5.9𝑘𝑢𝑛𝑝𝑁𝐿 �𝑠

12� �

𝑆30� �𝑊3�0.7

�𝑤4�0.5�1 − 𝜂𝑢𝑛𝑝� (14)

Where:

𝐸(𝑃𝑀)𝑝𝑎𝑣, 𝐸(𝑃𝑀)𝑢𝑛𝑝,𝑎𝑛, and 𝐸(𝑃𝑀)𝑢𝑛𝑝,ℎ𝑑 are the fugitive dust emissions for the applicable time period (annual, daily, hourly) for paved roads, unpaved road annual emissions, and unpaved road hourly or daily emissions, respectively, in pounds;

𝑘𝑝𝑎𝑣 and 𝑘𝑢𝑛𝑝 are particle size multipliers for paved and unpaved roads, respectively, and are given in Table IV-1 below;

𝑁 is the number of vehicles traveling the road in the given time period;



𝐿 is the length of the road in, miles;

𝑠𝐿 is road silt loading, in g/m2;

𝑆 is the mean vehicle speed of all the vehicles traveling the road in the given time period;

𝑊 is the mean vehicle weight of all the vehicles traveling the road in the given time period;

𝑤 is the mean number of wheels of all the vehicles traveling the road in the given time period;

𝑠 is the silt content of the road surface, in %;

𝑝 is the number of days per year with more than 0.01 inch of precipitation, which is assumed to be 40 for San Diego except for heavily watered areas, in which case, 𝑝 is assumed to be zero; and

𝜂𝑝𝑎𝑣 and 𝜂𝑢𝑛𝑝 are control efficiencies for paved and unpaved roads, respectively.

As a result of the District’s engineering evaluation, the District has concluded that use of the precipitation correction ((365 − 𝑝)/365) in equation 13 for heavily watered areas is not warranted since the addition of more water through precipitation is unlikely to significantly change the control efficiency. This would include areas required to be maintained visibly moist by the permit. The equation is still applicable to other roads where particulate emissions are controlled by other means such as chemical stabilization. For heavily watered areas, 𝑝 is set to zero in equation 13.

The basis for the parameters that are used in equations 13 and 14 in the analysis are further discussed below.

Table IV-16. Road Particle Size Multipliers

Road Type PM10 PM2.5 Unpaved 0.36 0.095 Paved 0.016

District vs. AP-42. It should be noted that the District continues to use these emission factor equations for roads even though EPA has published revisions to both the paved and unpaved road emission factors (EPA 2011, Section 13.2.1; EPA 2006, Section 13.2.2). Not including the vehicle speed factor for unpaved roads, the District emission factor equations are considerably more conservative in general than the revised EPA emission factors in most cases for both paved and unpaved roads (by about a factor of six for the largest waste haul vehicles expected at this facility (an exception is small vehicles on paved roads with high silt loading, which is not relevant for this evaluation).



Although the District is investigating this matter, the District believes the equations above are also more representative because they account for important parameters in estimating emissions from industrial haul roads such as vehicle speed. For heavy vehicles, one recent study (Gillies et al. 2005) found that EPA’s most recent emission factor correlation may significantly underestimate uncontrolled emissions for heavy vehicles (greater than about five tons) at higher vehicle speeds (greater than about 7 and 12 miles per hour for 4% and 7% silt content, respectively) and overestimated emissions below those speeds. The study found that EPA’s correlation under-predicted heavy vehicle emissions by a factor of six at about 50 miles per hour. The same study found the correlation that the District uses also under-predicted emissions by about 30%, which may be due to the extremely low moisture content (less than 0.5%) for the roadway tested. One confounding factor in EPA’s correlation of data based on many different source tests is that vehicle speed is highly correlated with vehicle weight in the data (MRI 1998). Although a correlation that does not include vehicle speed may be appropriate from a statistical viewpoint for the data set used for EPA’s emission factor development, it would not be expected to provide any predictive information on the effect on emissions of reducing speed for vehicles of a given weight.

Correlation with Vehicle Speed—Unpaved Haul Roads. The current version of AP-42 (EPA 2006; AP-42 Section 13.2.2) does not include speed as a factor in the emission factor correlation for fugitive dust from unpaved haul roads (i.e., roads where the majority of the traffic is heavy vehicles) although it is included in the correlation for public roads. The District finds there is ample evidence that speed is a significant factor in fugitive dust emissions from unpaved roads including haul roads—besides the fact that the emissions are obviously zero when the vehicle is not moving—and emissions correlate approximately linearly with vehicle speed for wheeled vehicles (Kuhns et al. 2010, Gillies et al. 2010, Kim et al. 2010, Gillies et al. 2005, Kuhns et al. 2005, Etyemezian et al. 2003a, Thompson and Visser 2001, Flocchini and Cahill, 1994). Although there is some evidence that the emissions variation may be greater than linear with speed—especially at higher speeds—(Goosens and Buck 2009), based on the information it has reviewed the District considers a linear relationship the most likely in the speed range of vehicles at this facility, which is limited to a maximum of 15 miles per hour. For tracked vehicles, (Kuhn et al. 2010, Kim et al. 2010) a correlation with vehicle speed is also apparent although the variation may be less than linear.

Correlation with Vehicle Speed—Paved Haul Roads. The applicant has proposed a linear correlation with speed (see equation 12) for estimating potential particulate emissions from paved roads. The current version of AP-42 (EPA 2011, Section 13.2.1) does not include speed as a factor in the correlation for particulate emissions from paved roads nor does the District’s standard emission inventory calculation procedure, which is based on an earlier version of AP-42.

One confounding factor in determining the effect of speed on paved road emissions is that the silt loading on paved roads rapidly reaches an equilibrium level that depends on the average vehicle speed over the road (EPA 2011, Section 13.2.1; Etyemezian et al. 2003b). Roads with higher average vehicle speeds have much lower silt loadings than those with lower speeds, all else being equal (EPA 2011, Section 13.2.1). This obscures the effect of



the vehicle speed on emissions when averaging data sets for roads with different average speeds. However, in situations where the silt loading is controlled, or relatively constant, particulate emissions from paved roads have been found to correlate with vehicle speed (Langston et al. 2008, Kuhns et al. 2004, Hussein et al., 2003, Etyemezian et al. 2003a, Fitz 2001). Based on review of this information, for purposes of estimating potential particulate emissions prospectively with an assumed constant silt loading level, or in the case of this facility a maximum silt loading level established by the A/C conditions and supported by monitoring, the District finds that there is sufficient evidence to support an approximately linear correlation of particulate emissions with vehicle speeds and accepts the applicant’s proposal for estimating paved road emissions.

Road Silt Contents Table IV-17(EPA 2011, Section 13.2.1) shows the silt contents used in the analysis of unpaved road emissions. For unpaved roads, the District’s default silt content of 15% was used. This silt content is based on silt content measurements for mineral industry roads in San Diego by the District. The default value was used since it is a well known phenomena that the silt content of unpaved roads normally is lower than the silt content of the native material from which they are constructed (EPA 2006, AP-42 Section 13.2.2) because smaller particles are preferentially removed by the vehicle transits. In general, the silt and smaller particles (particles less than 75 μ in diameter) are preferentially removed through air emissions until an equilibrium level of silt is achieve where the amount removed matches the amount created from the passage of vehicles. However, for other travel areas where the surface is not exposed to continuous traffic because the traffic spreads out over a wide area or the area is continuously changing (for example, the last 200 feet of waste haul vehicle travel to the active face on the landfill deck or the ends of the borrow area and cover roads), the estimated silt content of the native material forming the road surface was used since it is assumed that there are insufficient vehicle passes in this situation to significantly change the native silt content. The native material silt content was based on an analysis by the applicant of existing silt content measurements in the landfill footprint and the borrow areas that was reviewed and accepted by the District.



Table IV-17. Silt Content

Travel Area Silt Content, % Basis Unpaved roads 15 District default for industrial

haul roads. Landfill footprint native material

20.7 Analysis of site silt content.

Landfill deck on landfill footprint native material


Landfill deck on excavated BAA on BAB native material

33 Analysis of site silt content.

BAA and BAB on landfill footprint excavated native material


BAA and BAB native material

33 Analysis of site silt content.

Waste Haul Vehicle Characteristics The vehicle characteristics used to estimate the maximum expected emissions from the main entrance road and the waste haul roads are shown in Tables IV-18 and IV-19. The waste vehicle tare weights, payloads, and number of wheels were based on an analysis of vehicle traffic at existing San Diego landfills except for truck and trailer combinations carrying sealed waste containers (pods), which were based on information provided by an Orange County Landfill.



Table IV-18. MSW Haul Vehicle Characteristicsa

Vehicle Number

in Sample Average

Tare, tons

Average Payload,

tons

Average No.

Wheelsb,c,e

Average Vehicle Weight,

tons Transfer trailers 493 17.55 22.15 18.00 28.63 Small vehicles 180 3.26 0.53 4.61 3.52 Other vehiclesd 137 7.10 2.31 7.67 8.26 Refuse collection vehicles 549 17.06 6.96 10.54 20.54

Frontloaders 319 17.91 8.72 10.79 22.26 Sideloaders 0 0.00 0.00 0.00 0.00 Rearloaders 0 0.00 0.00 0.00 0.00 Roll-Offs 230 15.89 4.52 10.20 18.15

Total or average 1359 14.41 11.15 12.17 19.98 Total or average excluding transfer trailers 866 12.62 4.89 8.86 15.06 Total or average excluding transfer trailers and small vehicles 686 15.07 6.03 9.97 18.09 Truck and trailers carrying sealed waste containers (pods)f. N/A 21.27 13.10 18 27.82 aIncludes construction and demolition debris, which was only a small portion of the sample. bIncludes trailer wheels. cVehicles with a GVW greater than 50,000 pounds were assumed to have lift axles with two wheels, which were deployed when entering the landfill and raised on the return trip. dIncludes dump trucks etc. eOther vehicles with a GVW greater than 68,000 pounds were assumed to have 18 wheels. fBased on information provided by Prima Deshecha Landfill in Orange County on Waste Mangagement pod deliveries from Oceanside.



Table IV-19. Green Waste Haul Vehicle Characteristics

Vehicle Number

in Sample

Average Tare

(Empty Weight),

tons

Average Payload,

tons

Average No.

Wheelsa,b,d

Average Vehicle Weight,

tons Transfer trailers 26 16.78 22.31 18.00 27.94 Small vehicles 64 3.42 0.61 4.69 3.73 Other vehiclesc 99 6.64 1.66 7.11 7.47 Refuse collection vehicles 156 16.01 6.32 10.27 19.17

Frontloaders 77 16.89 7.24 10.39 20.51 Sideloaders 14 16.42 7.90 10.50 20.37 Rearloaders 0 0.00 0.00 0.00 0.00 Roll-Offs 65 14.87 4.90 10.08 17.32

Total or average 345 11.04 5.13 8.91 13.61 Total or average excluding transfer trailers 319 10.57 3.73 8.17 12.44 Total or average excluding transfer trailers and small vehicles 255 12.37 4.51 9.04 14.63 aIncludes trailer wheels. bVehicles with a GVW greater than 50,000 pounds were assumed to have lift axles with two wheels, which were deployed when entering the landfill and raised on the return trip. cIncludes dump trucks etc. dOther vehicles with a GVW greater than 68,000 pounds were assumed to have 18 wheels.

The number and type of vehicles (vehicle mix) delivering material to the facility determines the overall average vehicle characteristics used to estimate the haul road emissions. A key component of the vehicle mix is the amount of waste being delivered in transfer trailers, which, although they have higher emissions per vehicle, have lower emissions per ton of material delivered because of their higher payload to empty weight ratio.

The District estimated the vehicle mix based on the potential sources of waste (and ADC) in Northern San Diego County (North County) for the facility: the cities of Carlsbad, Del Mar, Oceanside, Solana Beach, Escondido, Poway, San Marcos, Vista, and associated unincorporated county areas and inland cities and unincorporated county areas north of these areas. Except for special situations, it is likely that waste generated south of these areas would go to existing San Diego Landfills. Waste from Southern Riverside County was not considered as most of this is under long-term contract to be delivered to Riverside County landfills.

How the waste would likely be delivered to Gregory Canyon landfill (i.e., transfer trailer or waste collection vehicle) is an economic decision by the waste haulers based on the



availability and cost of using a transfer station and the additional costs of operating a transfer trailer fleet compared to the costs in time and money of directly delivering the waste to the landfill. In general, beyond a certain distance to a landfill, it is cheaper to transport waste to a transfer station, offload it into transfer trailers, and then transport the waste to the landfill in transfer trailers.

There are two main waste haulers in Northern San Diego County (North County), EDCO and Waste Management (WM), neither of which own a landfill in San Diego County (Republic Services owns the Sycamore and Otay landfills and the Miramar Landfill is operated by the City of San Diego on land leased from the Navy). Both waste haulers have contracts with various cities in North County to pickup MSW. The waste stream from the area in North County served by EDCO largely goes through two transfer stations, one in Escondido the other in Fallbrook and is delivered to San Diego landfills. Waste Management does not have any transfer stations in North County and waste from its service area is delivered to landfills by standard collections vehicles (front loaders, side loaders, and roll-offs) or in the case of Oceanside, sealed waste containers on flatbed trucks (pods). Waste Management currently sends of its collected San Diego waste to El Sobrante Landfill in Riverside County.

Based on publicly available cost estimates, the District estimates that all the waste collected in the Waste Management area would be transported to Gregory Canyon Landfill in collection vehicles or pods, waste from EDCO’s Escondido transfer station would be delivered in transfer trailers (an additional 10,000 tons of waste from the EDCO Escondido area was also assumed to use transfer trailers), and waste now going through EDCO’s Fallbrook transfer station would be transported directly to Gregory Canyon Landfill in collection vehicles. Table IV-20 summarizes the waste streams and Table IV-21summarizes the resulting estimated waste delivery vehicle mix for the calculation details). Based on this analysis, the estimated average vehicle characteristics for waste haul vehicles delivering waste (including green waste used as ADC) are shown in Tables IV-22 and IV-23. The estimated waste haul road particulate emissions used in the additional AQIA modeling requested by the District is based on these vehicle characteristics.



Table IV-20. Summary of Expected Waste Stream for Gregory Canyon Landfilla

Area/Haul Vehicle Disposed, tons ADC, tons w/ADC, tons Total Waste Management (WM) Areab 260,716 32,362 293,078

Total Transported in podsc 81,700 0 81,700 Total Transported in waste collection vehicles 179,016 32,262 211,378

Escondido Transfer Station (EDCO)d 467,948 16,770 484,718 Total EDCO Escondido Area 467,948 26,847e 494,795 Fallbrook Transfer Station (EDCO) 61,864 12,398 74,263 Total EDCO Area 529,812 39,245 569,057 Total WM and EDCO & Others, N. County 790,528 71,607 862,136 Projected Waste to GCL

Total N. County to GCLi 1,000,000 90,582g 1,090,582 WM Area waste to GCLj 329,800 40,938 370,737 EDCO Areaf waste to GCL 670,200 49,644 719,844 Escondido area waste to GCL 591,943 21,213 613,157 Fallbrook (EDCO) waste to GCL 78,257 15,684 93,941 WM Area waste using pod transport 103,349 0 103,349

Transfer trailer transporth 591,943 21,213 613,157 Pod transportc 103,349 0 103,349 Standard waste collection vehicle transport

EDCO Areaf 78,257 28,431 106,688 WM N. County area 226,451 40,938 267,388 Total standard waste collection vehicle 304,708 69,368 374,076

Fraction in transfer trailers 0.592 0.234 0.562 Fraction in pods 0.103 0.000 0.095 Fraction in standard waste collection vehicles 0.305 0.766 0.343 Daily average amount in transfer trailers, tons per day 1,928 69 1,997 Daily average amount in pods, tons per day 337 - 337 Daily average amount in waste collection vehicles, tons per day 993 226 1,218 Total 3,257 295 3,552 Green waste, ton/ton 0.091 1 0.083 aUnless otherwise noted all waste and ADC amounts are from San Diego Department of Public Works Reports for 2010. bWaste from the Waste Management (WM) area of North County includes waste from the the cities served by WM, Carlsbad, Del Mar, Oceanside, and Solana Beach, and associated unincorporated areas of the county and includes waste picked up by independent haulers in those areas. Camp Pendleton is excluded since it has its own landfill. All waste from this area is assumed to be transported in standard waste collection vehicles, except for the amount transported by WM from Oceanside in pods. cThe pod transportation of waste by WM may have ceased. If this is the case, it would likely increase the amount of waste carried in standard waste collection vehicles if it is sent to the



proposed Gregory Canyon landfill. Another option would be shipment to El Sobrante landfill which is owned by WM. dWaste from the EDCO’s Escondido transfer station includes all the waste in the cities served by EDCO in North County outside the Fallbrook area: Escondido, Poway, San Marcos, Vista, and associated unincorporated county areas. It also includes any waste brought to the transfer station by independent haulers from these areas. eIncludes about 10,000 tons as reported by individual cities and for unicorporated areas that are not included in the Escondido transfer station total. fEDCO area includes all waste from the EDCO transfer station, the Fallbrook transfer station, any other waste from the areas served by EDCO. gBecause it so close to Gregory Canyon, it is expected that all the Fallbrook transfer station waste would be transported directly to Gregory Canyon in standard waste collection vehicles. hAll the Escondido area waste is assumed to go to Gregory Canyon through the Escondido transfer station. iTotal N. County waste stream is assumed to increase by 26% to reach the 1,000,000 ton per year permitted limit at Gregory Canyon. jGreenwaste was assumed to grow at 26% to correspond with the MSW growth.

Table IV-21. Distribution of Waste by Vehicle Type

Fraction or Amount MSW Green Waste as ADC Total Waste Fraction in transfer trailers 0.592 0.234 0.562 Fraction in pods 0.103 0.000 0.095 Fraction in standard waste collection vehicles 0.305 0.766 0.343 Daily average amount in transfer trailers, tons per day 1,928 69 1,997 Daily average amount in pods, tons per day 337 - 337 Daily average amount in waste collection vehicles, tons per day 993 226 1,218 Total 3,257 295 3,552 Green waste, ton/ton 0.091 1 0.083

Based on the above waste stream analysis, the estimated average characteristics for the waste haul vehicles are shown in Tables IV-22 and IV-23. The annual values differ from the daily values because the amount of green waste delivered and small internal vehicle traffic is assumed constant on each day of operation while the amount of MSW received increases from 3,257 tpd on an annual average day to 5,000 tpd on a maximum day.



Table IV-22. Characteristics of Waste Vehicles—Maximum Daily Waste Receipta Vehicle and Material Category Hauled

Payload, tons

Loaded Weight,

tons

Tare Weight,

tons

Average Weightb,

tons No.

Wheels

Fraction of Waste Category,

%

Daily Material,

tons Vehicles per day

MSW in transfer semitrailers 22.15 39.7 17.55 28.625 18 59.2% 2959.7 134 MSW in pods 13.1 34.37 21.27 27.82 18 10.3% 516.7 39 MSW in refuse collection vehicles 4.89 17.51 12.62 15.065 8.86 30.5% 1523.5 312 PGM for ADC in transfer trailers 22.31 39.09 16.78 27.935 18 23.4% 69.1 3 PGM for ADC in refuse vehicles 3.73 14.3 10.57 12.435 8.17 76.6% 225.9 61 Internal light duty vehicles NA 3 3 3 4 0% 0.0 25 Waste vehicle average or total

18.4 11.4

5295 574

a5000 tons per day of MSW and 295 tons per day of PGM as ADC. bThe average of the loaded and unloaded (tare) weight.

Table IV-23. Characteristics of Waste Vehicles —Maximum Annual Waste Receipt. Vehicle and Material Category Hauled

Payload, tons

Loaded Weight,

tons

Tare Weight,

tons

Average Weightb,

tons No.

Wheels

Fraction of Waste Category,

%

Daily Material,

tons Vehicles per day

MSW in transfer semitrailers 22.15 39.7 17.55 28.625 18 59.2% 591,943 26724 MSW in pods 13.1 34.37 21.27 27.82 18 10.3% 103,349 7889 MSW in general refuse vehicles 4.89 17.51 12.62 15.065 8.86 30.5% 304,708 62312 PGM for ADC in transfer trailers 22.31 39.09 16.78 27.935 18 23.4% 21,210 951 PGM for ADC in refuse vehicles 3.73 14.3 10.57 12.435 8.17 76.6% 69,356 18594 Internal light duty vehicles NA 3 3 3 4 0% 0.0 7675 Waste vehicle average or total

17.8 11.1

1,090,565 124,145

a1,000,000 tons per year of MSW and 90,565 tons per year of PGM as ADC. bThe average of the loaded and unloaded (tare) weight. The proposed A/C conditions contain limits on the amount of annual daily traffic on the waste haul roads in the form of particular matter emission indexes (PMEIs) that are proportional to the number of vehicle trips and account for variation in average vehicle characteristics. The District expects the applicant to be able to comply with these limits based on the above calculations.



Rock and Soil Haul Vehicle Characteristics Vehicle Characteristics. Except for rock or soil considered MSW, for all rock and soil, the expected on-site haul vehicles for soil and rock are scrapers. For purposes, of estimating the emissions, the scraper is assumed to be a late-model Caterpillar 637G. The 4-wheel scraper average load was assumed to be 20.3 banked cubic yards (BCY) of soil or 16.3 cubic yards of rock resulting in an average vehicle weight of 76 tons.

Annual Average Number of Cover Soil Scrapers Trips. To calculate the annual number of vehicles hauling cover material from the borrow areas the applicant assumed that 324,900 banked cubic yards (BCY) of soil was required per year for 1,000,000 tons of waste per year, except for the first year of operation in the Startup Phase when only about 211,61 BCY was assumed. For a waste density of 1350 pounds per cubic yard and 1,000,000 tons of waste per year a maximum of about 1,480,000 cubic yards (CY) of waste is received. Thus, the annual cover ratio is about 4.6 BCY of soil per cy of waste, a 4.6/1 cover ratio for 324,900 BCY of cover soil. Based on other landfills operating in San Diego, the District concludes this is a conservatively low cover ratio for a landfill using ADC of green waste and tarps and expects the applicant to be able achieve this or a higher cover ratio (i.e., less soil required). A conservatively high number of scrapers trips per year is 324,900/20.3 equal to about 16,000. The applicant added a 10% margin to this number in the actual emission calculations (17,600 trips per year).

The proposed A/C conditions contain limits on the amount of annual traffic on the BAA and BAB haul roads in the form of PMEIs that are proportional to the number of vehicle trips and account for variation in average vehicle characteristics. The District expects the applicant to be able to comply with these limits based on the above calculations. The PMEI is adjusted for the lower amount of cover assumed by the applicant in the Startup Phase. In addition, the amount of soil cover used on an annual basis in the Startup Phase is limited to 211,614 BCY.

Maximum Number of Daily Cover Soil Scrapers Trips. To estimate the maximum number scraper trips per day an industry standard cover ratio of 4/1, applicable when there is no ADC, was used. The the maximum allowed waste receipt rate of 5000 tpd (7407 cy per day). This results in 1852 BCY of soil being required. A reasonable estimate of the number of scrapers trips per day 1852/20.3 equal to about 91. The applicant added a 9 vehicle margin to this number in the actual emission calculations (100 trips per day).

The proposed A/C conditions contain limits on the amount of daily traffic on the cover, BAA, and BAB haul roads in the form of PMEIs that are proportional to the number of vehicle trips and account for variation in average vehicle characteristics. The District expects the applicant to be able to comply with these limits based on the above calculations.

Annual Average and Daily Number Scrapers Trips During Construction. The number of scraper trips during the Initial Construction Phase and Startup Phase, in addition to any



trips required for waste cover soil, was calculated by the applicant based on the proposed amount of material excavated from the landfill footprint during this phase. The details are in the applicant’s emission calculation spreadsheet.

The proposed A/C conditions contain limits on the amount of daily traffic on the BAA and BAB haul roads during construction in the form of PMEIs that are proportional to the number of vehicle trips and account for variation in average vehicle characteristics. The District expects the applicant to be able to comply with these limits.

Haul Road Emission Control Factors Unpaved Haul Roads and Other Travel Areas. The applicant has proposed that except for the last 700 feet of the internal waste haul roads leading to the active face and 200 feet at each end of the cover, BAA, and BAB haul roads all haul roads will be chemically stabilized (an exception is the fill haul road that is only projected to be used during the Initial Construction and Startup Phases). The proposed A/C conditions limit the lengths of these haul roads that are not chemically stabilized because the applicant has proposed a higher control efficiency for chemically stabilized portions of these roads. The control efficiencies are discussed below.

Chemically Stabilized Haul Roads. The applicant has proposed a control efficiency of 97% to control emissions of fugitive dust from most of the length of unpaved haul roads by use of polymer emulsions to chemically stabilize the road surface by binding the surface particulate matter together. The proposed control efficiency is relative to the uncontrolled emissions predicted by equations 13 and 14. The District was able to identify only a limited amount information that quantifies the control efficiencies of chemical dust suppressants such as those expected to be used at the facility using the standard exposure profiling method, which samples dust emission throughout the height or the vehicle dust plume and the background dust concentrations (or studies calibrated with this method). The District reviewed and analyzed one report (Muleski and Cowherd 1987) that quantified emissions from a haul road carrying vehicles with average weights of 10 tons or more using a chemical stabilizer similar to the one expected to be used at the facility (a polymer emulsion) to control fugitive dust. The analysis indicates that control efficiencies of 97% relative to equation 14 or more are achievable by application of such a chemical dust suppressant.

However, the analysis also indicated that the control efficiency drops to 95% within about 1200 vehicle passes over about five days (giving an average control efficiency of about 97.5% over that time period). The polymer emulsion performed significantly better than other products tested in this regard. The method of application of the dust suppressant was not specified in the report, although it was likely a topical application as no description of it being admixed with the soil is provided. The District would expect significantly better long-term performance for chemical stabilizers admixed with the soil since topical application may form a relatively thin crust that is more easily fragmented by vehicle traffic exposing unstabilized material (Rushing et al. 2005).

Based on the above analysis and an analysis of additional data of use of chemical dust suppressants on roads traveled by small vehicles (Rushing et al. 2005, Gillies 1999, Watson



et al 1996), the District finds that instantaneous control efficiencies in excess of 97% are achievable by chemical stabilization of the road surface and expects the applicant to be able to achieve this control efficiency on average. However, the District also finds that the control efficiency significantly decreases over time at a rate that likely depends on the frequency, speed, and weight of the vehicles traversing the surface as well as ambient conditions and the nature of the road construction and surface. In this regard, the proposed landfill could have a 1000 large vehicle (average weight about 18 tons) passes in two days or less on the internal waste haul roads. The borrow area roads could have about 100 vehicles per day during normal operation, albeit with heavier vehicles (about 76 tons).

To partially address the potentially perishable nature of the control efficiency from chemical stabilization, the A/C conditions require that any chemical stabilizer (chemical dust suppressant) be applied at least quarterly, regardless of the manufacturer’s instructions. Furthermore, since the District has been unable to find any robust supporting information as to how frequently reapplication of the chemical stabilizer is required for high-use industrial haul roads to achieve 97% control, aside from the one study cited above, the proposed A/C requires that there be daily monitoring of the visible dust from haul roads with a limit of no visible emissions from a vehicle traveling on a chemically stabilized road at eight feet or more above the roadway except for momentary and nonrepeatable readings. (see Opacity Monitoring below).

Unpaved Travel Areas that Are Not Chemically Stabilized to Achieve 97% Control. The applicant has proposed 95% control for the other areas traversed by haul vehicles including the portions of the unpaved roads not chemically stabilized to achieve 97% control. The applicant has proposed achieving this level of control by watering and potentially other dust control methods.

The District examined two sets of data where PM10 emission control efficiency versus moisture content for scrapers on unpaved roads were reported (Muleski and Cowherd 2001, MRI 1999). The indicated control efficiencies relative equation 14 exceeded 95% provided the surface moisture content is high enough. The average vehicle weights in the two studies were about 28 tons in one study and 81 tons in the other, and the average vehicle speed was about 13 mph in both studies, which is comparable to the vehicle weights and speeds that are expected at Gregory Canyon Landfill. It should be noted that in one of the studies (Muleski and Cowherd 2001), the initial PM10 measurements were made about a half hour after water application in most of the test runs, so higher instantaneous control efficiencies were likely immediately after water application.

The control efficiency follows the same general relationships as emission control for PM15 from a coal yard haul road with a rapid rise in control efficiency at low moisture contents that levels off at higer levels (MRI 1985). It is not clear from the data if average control efficiencies greater than 95% are possible on a routine basis even for short periods. In addition, chemical stabilization is likely not technically feasible for unpaved travel areas with silt content greater than 20% to 25% (Kissell 2003), which may be the case for many unpaved travel areas at Gregory Canyon Landfill.



Based on review of this information, the District has determined that an instantaneous 95% control of dust emissions from these areas is technically feasible. Therefore, the District considers that this level of control is achieved in practice and expects the applicant to be able to achieve it.

However, maintaining an average control efficiency of 95% requires continual reapplication of water at a frequency that depends on various factors such as the amount of water applied, meteorological conditions, surface conditions, and traffic characteristics and volume. The time required for the average control efficiency to decline to 95% (assuming 100% control immediately after water application can range from a half hour or less to more than two hours depending on the ambient conditions (Muleski and Cowherd 2001). For the mineral industry, the District standard emission calculation methods for haul road emissions provide for a 95% emission control factor when calculating emissions provided that roads are watered every two hours and appropriate opacity limits are taken for the fugitive particulate matter. However, the A/C does not specify a watering frequency because specifying a fixed frequency is likely to be wasteful of water in some cases and not require watering often enough in other cases considering the wide variability in the required watering frequency. Instead, the proposed A/C relies on conditions limiting the opacity in particulate plume behind vehicles to no visible emissions, except for momentary and nonrepeatable events, eight feet above the surface.

Paved Haul Roads. The District has determined that a silt loading limit of 0.4 gm/m2 is BACT for paved roads. Based on the District’s default silt loading value for paved haul roads of 13.6 gm/m2 and the emission factor correlation, this limit controls the emissions from the paved road by about 90%. No additional emission control is credited for sweeping or washing because that is accounted for in the reduced silt loading.

Vehicle Speed Limitations. Vehicle speed is limited to 15 miles per hour throughout the facility to reduce particulate emissions from all vehicles.

Other Haul Road Control Measures. One additional factor that is important in limiting emissions on haul roads is the amount of material spillage on to the road surface. Chemically stabilized roads using polymers or other products to bind the particles on the road surface together are especially susceptible to having the control efficiency of those products degraded by spillage of fine material on the surface. Watered roads and roads using hygroscopic salts are less susceptible since there may be some transference of the moisture to the spilled material (Kissell 2003). The proposed A/C contain conditions that limit the amount of spillage of material that is imported or exported from the facility. In addition, opacity limits and monitoring are used to assure that proposed control levels are being achieved.

Overall Road Fugitive Emission Control for Haul Vehicles. The overall emission control including the reduction in vehicle speeds from the default values is given in Table IV-24.



Table IV-24. Overall Haul Road Emission Control Efficiency

Vehicle Speed Emission Control Factor

Road Surface Control Factor

Overall Control Factor

Haul Vehicles on Paved Roads 54% 90% 95.4% Haul Vehicles on Unpaved Chemically Stabilized Roads 50% 97% 98.5% Haul Vehicles on Other Unpaved Surfaces 50% 95% 97.5%

EARTHMOVING AND MSW HANDLING PARTICULATE EMISSION FACTORS The District emission factor for general construction emission is derived loading and unloading operations of gravel storage piles and not generally applicable to most earthmoving operations. Instead, process specific emission factors were developed by the District for this project as described below.

Bulldozer, Scraper Loading, Compactor, and Road Grader Scarification Emission Factors Earthmoving and Material Handling Emissions. For earthmoving and material handling operations using bulldozers and scrapers, the District followed the Mojave Desert Air Quality Management (MDAQMD 2000) emission inventory procedure for operations with this equipment and based emission factors on the AP-42 bulldozer emission factor.

𝐸(𝑃𝑀10)𝑒𝑚𝑤ℎ,𝑏𝑑 = 0.75𝑠1.5𝑀−1.4 (15a)

Where:

𝐸(𝑃𝑀10)𝑒𝑚𝑤ℎ,𝑏𝑑 is the PM10 emissions from bulldozer operations, lb/hr;

𝑠 is the silt content, %;

𝑀 is the moisture content, %

For compactor operations, the District used the following equation (Wood et al. 2010) for rolling, an agricultural tilling operation that is representative of compacting operations:

𝐸(𝑃𝑀10)𝑒𝑚𝑤ℎ,𝑐𝑜𝑚 = 0.813(𝑠 100⁄ )0.6[−86.5𝑙𝑛(𝑀 100⁄ ) − 95.159] (15b)

Where:

𝐸(𝑃𝑀10)𝑒𝑚𝑤ℎ,𝑐𝑜𝑚 is the PM10 emissions from compactor operations, in mg/m2.



The District reduced the lead coefficient in equation 15b to account for vehicle travel the contributed emissions to this emission factor (estimated as about 25% of total emissions was based on a 4-wheel John Deere tractor). This avoids double counting emissions since, as discussed below, compactor travel emissions were included in this analysis’s estimate of overall emissions from compaction operations based on estimated compactor vehicle characteristics.

For potential scarification of clay liner lifts by a road grader before compaction, the District used the following equation (Wood et al. 2010) for ripping, an agricultural tilling operation, which involves shallow ripping of the soil, that is representative of scarification (the potential scarification of liner lifts is done to ensure adhesion between lifts and is only 1–2 inches deep):

𝐸(𝑃𝑀10)𝑒𝑚𝑤ℎ,𝑠𝑐𝑎𝑟 = 3.15(𝑠 100⁄ )0.6[−86.5𝑙𝑛(𝑀 100⁄ ) − 95.159] (15c)

Where:

𝐸(𝑃𝑀10)𝑒𝑚𝑤ℎ,𝑠𝑐𝑎𝑟 is the PM10 emissions from road grader scarification operations, in mg/m2.

In this case, the District did not adjust the emission factor to account for vehicle travel that contributed emissions to this emission factor as it is likely the contribution was relatively small. However, like compaction operations, road grader travel emissions were included in the analysis’s estimate of overall emissions from scarification operations based on estimated road grader vehicle characteristics.

The bulldozer earthmoving emission factor accounts for material silt and moisture content and gives PM10 emissions on a pounds per hour basis as a result of earthmoving. For vehicles other than bulldozers this emission factor only accounts for emissions resulting from earthmoving and potentially underestimates travel emissions to the extent they are greater than a bulldozer’s travel emissions during earthmoving. Therefore, for scrapers the emission factor was adjusted by adding emission estimates for vehicle travel during the earthmoving operations using the District’s default unpaved road emission factor correlation to ensure that emissions were not less than those that would occur from the vehicles travel alone without any earthmoving. This potentially overestimates emissions for vehicles other than bulldozers to the extent that travel contributed to the bulldozer operations. However, there is some evidence that tracked vehicle travel emissions are significantly less than wheeled vehicle emissions. No vehicle travel emission factor was included for bulldozers since that was implicitly included in the original measurements of fugitive dust emissions from bulldozers.

The compaction and scarification emission factor also account for material silt and moisture content and gives emissions on a per area basis. These emission factors were also adjusted



for vehicle travel during the operation as described below because the vehicle emissions from expected compactors and road graders are likely much greater than from the farm tractors used in the emission factor measurements.

For bulldozers, the earthmoving emission factor was converted to an emission factor in units of pounds per banked cubic yard (lb/BCY), pounds per compacted cubic yard (lb/CCY), and, for MSW, lb/ton by use of standard reference productivity estimates for bulldozers. For scraper loading, the emission factor was converted to the same units by an estimated loading time for a scraper. For compaction and scarification, the emission factor was also converted to units of lb/CCY and, for MSW, lb/ton based on estimated lift thicknesses and compactor and road grader operational characteristics.

Scraper Loading and Unloading, Compactor, and Scarification Travel Adjustment. The emission factor for scraper loading and unloading was adjusted by adding travel emissions, based on a Caterpillar 637G scraper, to the earthmoving emissions based on equations 13 and 14 for an estimated travel distance during loading, a 180 degree turn, and an equivalent return trip. These emissions were converted to an emission factor in units of lb/BCY and lb/CCY based on the estimated scraper maximum load. The emissions for this part of a scrapers operational trip are in addition to the scraper emissions from travel on roads and other unpaved surfaces (e.g., off-road travel to reach the loading point). The average speed used in the unpaved road emission equations for the scraper over the overall distance is based on a distance weighted average of the estimated speed during the loading distance and the allowed speed per the proposed A/C conditions for the rest of the distance. Average vehicle weights were calculated assuming the scraper is empty at the start of the loading process and full at the start of the unloading process and carried their maximum rated load by weight.

For compactors, the travel emissions were also calculated in a similar manner from the unpaved road emission factor equations, based on a Caterpillar 825G for fill and clay liner and a Caterpillar 836G for solid waste and landfill cover material, using either the minimum of the expected speed of the compactor based on the material being compacted or the allowed speed per the proposed A/C conditions and lift thickness. No turns were include in the compactor travel emission estimate. The factors were converted to lb/CCY or lb/ton based on compactor productivity estimates.

For road graders engaged in scarification, the travel emissions were estimated based on an Caterpillar 160M road grader following the procedure for the compactor travel adjustment to estimate emissions. The road grader’s speed was assumed to be 15 mph during the scarification operations.

Scraper and Truck Unloading Earthmoving and MSW Handling Emission Factors For unloading operations the following AP-42 equation for batch drops was used to estimate emissions from the unloading process itself exclusive of any associated travel emissions:



𝐸(𝑃𝑀10)𝑢𝑛𝑙𝑜𝑎𝑑 = 0.00112𝑠𝑎𝑑𝑗 �𝑈5�1.3

�𝑀2�−1.4

(16)

Where:

𝐸(𝑃𝑀10)𝑢𝑛𝑙𝑜𝑎𝑑 is the PM10 emissions, lb/ton;

𝑠𝑎𝑑𝑗 is a adjustment factor for silt content outside of the range of silt contents used to develop the emission factor;

𝑈 is the weighted mean annual wind speed, mph; and


The wind speed in the equation was an appropriately weighted (i.e., averaged considering exponent in equation 16). This was assumed to apply at all times (i.e., the emissions were not adjusted hourly based on wind speed). For scrapers, the emission factor was adjusted for travel by the procedure used to adjust the scraper loading emission factor. For trucks unloading MSW, the truck was assumed to be stationary when unloading waste and the travel distance prior to unloading is already accounted for in the applicant’s AQIA modeling, which includes 700 feet of travel on an unpaved road and unpaved landfill surface for all vehicles entering the facility prior to unloading. However, for trucks carrying clay liner material, there was assumed to be an additional 200 feet of travel on clay liner surface prior to unloading.

For materials with silt contents less than or equal to 19.6%, the silt adjustment factor is equal to one. For materials with silt contents greater than 19.6 the silt adjustment factor is given by:

𝑠𝑎𝑑𝑗 = �𝑠

19.6� (17)

Where:

𝑠 is the silt content, %

Road Grader Emssions Although the Mojave Desert procedure also estimates road grading emissions using the bulldozer earthmoving emission factor, the applicant proposed and the District has accepted using the road grader emission factor in AP-42, Section 11.9, which provides road grader emission factors in units of lb/VMT based solely on the grader’s speed, for road maintenance. The applicant adjusted this emission factor upwards in some cases to account for the presence of loose soil. Because of the likely high moisture content on road and unpaved surface areas routinely traveled from road watering, the District accepted this



emission factor as a conservatively high estimate of road maintenance grading emissions. The road grading emissions were estimated based on a maximum expected grader speed of 7.5 mph for road maintenance activity.

However, for scarification of liner lifts, the District used the earthmoving emission factor for bulldozers discussed above that was adjusted for additional estimated travel emissions

for a road grader (Caterpillar 160M) following the procedure for the compactor travel adjustment to estimate emissions. The road grader’s speed was assumed to be 15 mph during the scarification operations (the potential scarification of liner lifts is done to ensure adhesion between lifts and is only 1–2 inches deep).

Earthmoving and MSW Handling Emission Factor Parameters Table IV-25 shows the parameters used to estimate earthmoving and MSW handling emissions. Note that since the effect of moisture is already included in the emission factors no additional control efficiency for the earthmoving portion of the emissions (i.e., nontravel emissions) based on watering is appropriate.

Table IV-25. Earthmoving Emission Factor Parameters

Material Silt Content, % Controlled Moisture Content, %

Storage Pile Soila 20.7 8.5c Borrow Area Soilb 33 8.5c Landfill Soil 20.7 8.5c Shot Rock 4 4 Engineered Fill Soil 20.7 12d Liner Clay 95e 18f MSW 12.7 19.6 aLandfill soil that is stored for use as cover in the borrow areas. bSoil excavated from the borrow areas. cCorresponds to 95% emission control using the bulldozer earthmoving emission factor equation or the batch-drop unloading earthmoving emission factor relative to a uncontrolled moisture content of 1%. The proposed A/C conditions limit opacity from fugitive dust emissions that are not haul vehicles traveling on unpaved surfaces to 10%. For haul road travel, this corresponds to 95% control if sufficient watering is used. This was assumed to apply to fugitive emissions for the earthmoving operations. dTypical minimum optimum moisture content for soil compaction. eTypical of California clay liners. fTypical minimum optimum moisture density for clay compaction to achieve low hydraulic permeability.

Earthmoving Travel Emission Control Factors For vehicle travel during earthmoving operations the control factors in Table IV-26 were used. For materials with expected high moisture contents, a control efficiency calculated



from the following equation was used in lieu of that the proposed A/C conditions if the control efficiency was greater than the control efficiency derived from the conditions or proposed by the applicant:

𝜂𝑡𝑟𝑎𝑣 = 1 −𝑀−1.07 (17)

𝜂𝑡𝑟𝑎𝑣 is the emission control factor for travel during earthmoving operations; and


The equation is based on a District fit of the control efficiency indicated by scraper emission factors (Muleski and Cowherd 2001, MRI 1999) relative the District’s unpaved emission factor.

Table IV-26. Earthmoving Emission Factor Parameters

Material Control efficiency, % Basis

General unpaved surface travel 95 No visible emissions per proposed A/C

conditions. General travel during unloading, loading, or compaction

90 Maximum of 10% opacity per proposed A/C conditions.

Travel on engineered fill soil 95 No visible emissions per proposed A/C conditions.

Travel on clay liner 95.5 Based on expected moisture content. Travel on MSW 95.9 Based on expected moisture content.

Earthmoving Emission Factor Summary Table IV-27 shows the District’s calculated composite earthmoving and waste handling emission factors for the project except for road grading maintenance emissions for various overall earthmoving operations. Each emission factor is the sum of the emission factors for the various earthmoving activities that comprise the overall operation.



Table IV-27. Earthmoving and Material Handling Emission Factor Summary

Operation EF, lb/1000 BCY

EF, lb/1000 CCY EF, lb/1000 ton

Unloading landfill soila in BAA 2.447441 2.62098 1.488861 Unloading landfill soila in BAB 2.447441 2.62098 1.488861 Unloading landfill rock in BAB 1.005401 0.876023 0.437131 Loading landfill soila in BAA 5.778614 6.336065 3.134296 Loading landfill soila in BAB 5.778614 6.336065 3.134296 Excavating and loading borrow area soil in BAA 17.71685 19.05315 9.609547 Excavating and loading borrow area soil in BAB 21.66624 23.2104 11.75168 Fille 18.66991 20.40504 10.28786 Landfill footprint excavation in Phase I 16.97072 18.54226 9.204851 Landfill footprint excavation in Phase II 21.48348 23.55644 11.65255 Rock crushing in the landfill footprint

2.97925

Rock crushing in BAB

5.94125 Clay liner installationb,c,d 55.87291 61.56161 29.88124 Rock loading Phase I 2.054543 1.674884 0.893279 Rock loading Phase II 2.557275 2.061602 1.111859 Landfill operations, waste deposition

2.827437

Landfill operations, soil cover application using landfill soil 8.703787 9.206607 4.882277 Landfill operations, soil cover application using borrow area soil 12.82717 13.57359 7.214677 aAlso applies to loading or unloading soil in other storage piles. bDoes not include installation of gravel base. cIncludes unloading, spreading, compacting, and scarification and installation of soil working surface of equivalent volume over the liner. dAssumes that clay is delivered directly to liner installation area in 18-wheel dump trucks with a tare weight of 15 tons and a loaded weight of 40 tons. eIncludes unloading, spreading, and compacting.

EARTHMOVING AND MSW HANDLING PARTICULATE MATTER POTENTIAL TO EMIT The applicant requested and the District provided a spreadsheet with a preliminary set of earthmoving emission factors to estimate emissions in 2009. The applicant indicated that the preliminary emissions factors were used to estimate the earthmoving emissions. The applicant made some changes to the emission factors including an additional 90% control



efficiency based on the high moisture content of clay liner that was not appropriate since the moisture content was already accounted for in the emission factors. The applicant also failed to revise the emission factors for the most recent particulate matter modeling submittals to account for the increase in allowed vehicle speed from 7.5 mph, originally proposed by the applicant to 15 mph, an allowed speed the applicant was willing to accept as a permit condition and was used for other vehicles in the supplemental AQIAs requested by the District. Furthermore, it is not clear if the applicant included all the activities associated with a given overall operation. As part of the engineering evaluation, the District has also reevaluated and revised some of the preliminary emission factors based on additional analysis. For example, the MSW handling emission factor was increased based on a better estimate of compactor productivity when handling MSW. As a result, the District’s earthmoving PM10 (and correspondingly, PM2.5) emission estimates differ significantly from the applicants PM10 estimates from earthmoving that were used in the AQIA. Consequently, the proposed A/C conditions contain conditions to limit the emissions to a level consistent with the AQIA. The District’s estimate of annual earthmoving emissions compared to the applicant’s most recent AQIA submittal for some key years is shown in Table IV-28.

Table IV-28. Estimated Annual Earthmoving Emissions

AQIA Modeling Year District Emission

Estimate, tons Applicant Emission

Estimate, tons Net Increase, tons Year -2 37.63 24.43 13.20 Year 1 42.45 19.37 23.08 Year 17 9.20 6.77 2.43

PGM PARTICULATE EMISSIONS The applicant did not provide any estimate of emissions from use of processed green material as alternative daily cover. The District assumes that the emissions are the same as those from soil excavated from the borrow areas. The proposed A/C conditions limit the emissions from cover use to the levels that were modeled for the AQIA by the applicant.

BLASTING Blasting is source of NOx, CO, PM10, PM2.5, and SOx emissions. During the Initial Construction Phase and the Startup Phase blasting will be used to loosen hard rock, which may be about 40% of the total material excavated from the landfill footprint. It will also likely be used in BAB. No blasting is proposed for BAA.

Emission Estimation Method The applicant proposed estimating fugitive dust emissions from blasting using the District’s emission inventory emission estimation procedure for blasting, which is based on an emission estimation method for total suspended particulate matter (TSP) provided in AP-42.



A PM10 fraction of 52 percent is assumed for blasting TSP emissions by the District. The applicant also noted that that EPA has updated the quantification method as it was determined that there was a typographic error in the TSP blasting emission factor. The applicant proposed a corrected District method:

𝐸𝑃𝑀𝑏𝑙𝑎𝑠𝑡 = 0.000014𝑘𝐴1.5 (18)

Where: 𝐸𝑃𝑀𝑏𝑙𝑎𝑠𝑡 is the emissions of particulate mattter per blasting event, lbs

𝐴 is the horizontal surface blasting area, ft2

𝑘 is a scaling factor for portion of PM10 or PM2.5 in particulate matter;

The District has reviewed and concurs with this method.

The applicant also proposed using the standard AP-42 method to estimate NOx, CO, and SOx from blasting based on ammonium nitrate fuel oil explosives (ANFO) and proposed that the NO2 portion of the NOx was 19%. The District has reviewed and concurs with this approach.

Blasting Potential to Emit The proposed A/C conditions limit blasting events to one per day and no more than 65 blast events per year during the Initial Construction Phase. After the first receipt of waste, blasting is limited to no more than one blast event per day and no more than 22 blast events per year. Potentially all hard rock may need to be blasted. The District finds that the applicant has underestimated the annual and 24-hour potential to emit for blasting emissions in some cases. For example, although the applicant’s soil balance indicates about 1,200,000 CY of rock may be excavated in the first year that MSW is received, the applicant modeled only 24,200 CY of rock to be blasted (a single 30-feet deep, ½ acre blast using eight tons of ANFO). The District notes that, based on the applicants modeling submittals, the first year that MSW is received has the maximum annual PM10 impact due to the combination of landfill construction and receiving MSW. In the first year of construction when he applicant’s soil balance also indicates about 1,200,000 CY of rock may be excavated, the applicant modeled 65 blasts totaling only about 532,400 CY of rock—the largest blast modeled was ¼ acre although up to ½ acre blasts are proposed. The applicant may also have underestimated the amount of explosives required. Although blasting requirements are very site specific, according to the Standard Handbook for Civil Engineers (Sain and Quinby 2004), 1 to 1.5 pounds of explosive are required for every cubic yard of granite blasted. A 30-foot deep, ½ acre blast has a blast volume of approximately 24,200 yd3, which would imply about 12–18 tons of explosives, which is more than the eight tons modeled by the applicant for that size of blast. Consequently, to maintain consistency with the emissions used in the AQIA and HRA



modeling submitted by the applicant, the proposed A/C conditions limit the amount of explosives and the amount of material blasted on a daily and annual basis, as necessary.

Blasting and NO2 The proposed blasting events occurring in the landfill footprint and in BAB are both limited in location relative to the Northern, Southern, and Western property lines depending on their magnitude by the proposed A/C conditions based on a sufficient distance to prevent exceeding the ambient air quality standards for NO2.

Blasting and PM10 Location limits relative to the Northern, Southern, and Western property lines in the proposed A/C conditions were established based on NO2 and do not necessarily ensure by themselves that there will be no exceedamce of a PM10 ambient air quality standard (AAQS) when blasting emissions are combined with other PM10 emissions occurring at the facility. The ambient air quality modeling submitted by the applicant assessing the impacts of particulate matter, as supplemented by the District, is the basis for the determination that the AAQSs for PM10 are not exceeded.

WIND-BLOWN DUST

Wind-Blown Dust Emission Factors The District preliminarily recommended to the applicant that annual wind-blown dust (PM10 and PM2.5) emissions be calculated by a method based on agricultural wind erosion estimation methods in the National Agronomy Manual (USDA 2002) for the September 14, 2010 emission estimates and AQIA and HRA submittal. To estimate the windblown dust on an hourly basis, the applicant proposed that wind-blown dust only occurs when the hourly average wind speed exceeds 12 miles per hour when measured at the standard 10 meter height and that the annual emissions be divided equally among those hours. Although possible in the modeling software there was no adjustment made for higher rates of particulate matter emissions at higher wind speeds. The District preliminarily concurred with this approach and this approach was followed in supplemental AQIA’s requested by the District.

Subsequently, as part of the engineering evaluation the District reviewed the Maricopa County, Arizona, method of estimating dust emissions on an annual an hourly basis (Maricopa County 2011) and additional reference materials on wind-blown dust. Also, subsequently to the submitted AQIAs by the applicant, proposed A/C conditions were developed to limit wind-blown dust, based largely on Maricopa Rule 310. These conditions substantially increase the estimated control efficiency for areas under control from 30% to 80%.

Based on a review this material and analysis based on the Gregory Canyon meteorological data used in the AQIA modeling and the enhanced wind-blown dust control efficiency provided by the proposed A/C conditions, the District finds the following:



• The use of a 12 mile per hour threshold wind velocity is supported by the Maricopa method.

• Wind-blown dust can occur when the wind speed exceeds 12 miles per hour on a minute-by-minute basis even though the hourly average wind speed is less than 12 miles per hour. However, this does not change the annual emissions based on the NAM method although they would be distributed over more hours with less emissions in each hour (only hourly average wind speed data is available in the Gregory Canyon modeling files).

• The emission rate of wind-blown dust rises rapidly as the wind speed exceeds the threshold velocity (proportional to the wind speed over the threshold raised to the 3rd or 4th power).

• Based on the available meteorological data, the National Agronomy Manual (NAM) based method provides a conservative estimate of annual emissions on a per acre basis in comparison to the Maricopa method.

• Based on the available meteorological data and using the higher control efficiency resulting from the proposed A/C conditions, the NAM-based method underestimates daily particulate emissions relative to the Maricopa method on two days in the two-year meteorological data period. The NAM-based method provides an equal or higher estimate of daily emissions on 234 days in the period on a per acre basis. If the preliminary control efficiency is used, the NAM-based method provides a higher emission estimate on all 236 days when the hourly average wind speed was 12 mph or greater.

Based on consideration of the above information and considering the fact that the particulate air quality impacts from other sources are smallest when the impacts from wind-blown dust are highest due to the enhanced dispersion at high wind speeds, the District concludes that the NAM-based method used to estimate wind-blown dust provides a reasonable estimate of wind-blown dust and the possibility of occasional higher daily emissions does not significantly impact the AQIA results.

Wind Erosion Potential to Emit The potential to emit relative to a natural state depends on the amount of disturbed area that is not controlled and the amount of disturbed area that is controlled. The applicant proposed various areas as disturbed (not controlled) and undisturbed (disturbed but controlled). The District estimates that the amount of disturbed and undisturbed areas may be underestimated by the applicant but this is partially offset by the enhanced control efficiencies for the undisturbed areas provided by the proposed A/C conditions (80%) relative to the control efficiencies used by the applicant as preliminarily recommended by the District (30%).

DRILLING AND ROCK CRUSHING Drilling and rock crushing are a source of particulate matter emissions. The engines powering the equipment are also a potential source of emissions of all criteria pollutants and TACs including diesel particulate. However, the applicant has proposed only using electric engines as motive power. The proposed A/C conditions do not allow the use of nonelectric



engines without undergoing a full AQIA and HRA including all the landfill emissions and TBACT is applied. Hence, only emissions of particulate matter are considered from this equipment.

The applicant used standard District estimation methods and appropriate control efficiencies to estimate drilling and rock crushing emissions. The District has reviewed and concurs with these methods. However, the potential emissions for drilling are underestimated in some cases because they are based on the amount of blasting. The proposed A/C conditions that limit blasting serve to limit drilling emissions also.

MISCELLANEOUS EMISSION SOURCES

Leachate Collection and Disposal System The proposed A/C conditions require all vents from the leachate collection and disposal system be ducted to the landfill gas collection and control system. In addition, the conditions prohibit burning of leachate in the flare. Based on this, the District finds that air emissions from this source are insignificant.

Fueling Station The applicant as proposed a fueling station on-site. The proposed A/C conditions limit such a station to dispensing diesel fuel unless a full of evaluation of the toxic impacts in conjunction with the potential to emit of all other sources on the landfill is performed and TBACT is applied. The emissions of a diesel fueling station are considered insignificant.

Chemical Stabilizer VOC Emissions The applicant provided an analysis of potential VOC emissions from application of a chemical stabilizer. The District has reviewed those emissions and concluded they are insignificant in comparison to VOC emissions from landfill gas.

PM2.5 EMISSIONS The applicant estimated PM2.5 emissions based on a fraction of PM10 or TSP emissions. The District has reviewed and concurs with the proposed fractions.

TOXIC EMISSION FACTORS FOR PARTICULATE MATTER Default trace metal concentrations for San Diego County have been developed by the District from analyzing multiple haul road silt samples taken from several mineral products industry sites and are shown in Table IV-29. These emission factors were used to estimate toxic emissions by multiplying PM10 emissions by the weight fraction of toxic compounds.



Table IV-29. Haul Road Dust Trace Metal and Mineral Concentrations Trace Metals Range Detected in

SD County (ppmw) Default Value

Arsenic 1 to 50 20 Beryllium 0.5 to 2 1 Cadmium 1 to 1.5 1 Chromium (total) 5 to 60 50 Copper 20 to 650 100 Lead 5 to 120 50 Manganese 200 to 1200 500 Mercury 0 to 10 5 Nickel 3 to 25 20 Selenium 3 to 5 5 Silica (crystalline) 10% to 75% 10% Zinc 30 to 300 200 Asbestos Not Detected 0

OVERALL PROJECT EMISSION AND POTENTIAL TO EMIT

Applicant Calculated Emissions

Criteria pollutant emissions and total toxic emissions for each of the years assessed are shown in Table IV-30 as provided by the applicant from the Application Volume VII submittal on September 14, 2010. The applicant included diesel particulate emissions from off-road equipment in the emission estimates, which the District does not regulate. The off-road equipment diesel particulate contribute about 0.6 tons per year during normal operations and up to about 2.5 tons per year during construction to the PM10 and PM2.5 totals below.

Table IV-30. Applicant Annual Emission Estimates, September 14, 2010, tpy

Pollutant Modeling Year -2

Modeling Year 1

Modeling Year 8

Modeling Year 17

Modeling Year 22

Modeling Year 23

PM10 68.16 82.45 55.01 58.50 37.36 62.70 PM2.5 15.28 21.04 16.81 20.11 16.34 20.41 CO 5.90 0.27 1.30 3.47 3.42 3.55 NOx 1.50 0.07 9.57 20.25 25.12 26.08 SOx 0.18 0.01 5.32 11.18 13.97 14.50 VOC -- -- 12.65 26.52 33.21 34.47 TAC 8.67 11.9 14.9 24.6 18.90 30.8



As requested by the District, to better evaluate potential particulate matter impacts, the applicant provided additional estimates submitted on December 29, 2011, with the corresponding supplemental AQIA. The new emission estimates reflect more realistic operating conditions including a 15 mph vehicle speed limit (instead of 7.5 mph which the applicant was unwilling to accept), a more representative mix of waste vehicles, reducing road grades to levels consistent with standard engineering practice (and thereby increased road length), increased areas subject to wind-blown dust, and a reduction in the annual amount of waste received to 1,000,000 tons per year. This estimate is shown in Table IV-31.

Table IV-31. Applicant Annual Emission Estimates, December 29, 2011, tpy

Pollutant Modeling Year -2 a

Modeling Year 1

Modeling Year 8a

Modeling Year 17

Modeling Year 22

Modeling Year 23a

PM10 113.18 97.07 N/A 70.91 40.86 N/A PM2.5 27.08 24.17 N/A 23.47 17.52 N/A CO 5.90 0.27 N/A 3.47 3.42 N/A NOx 1.50 0.07 N/A 20.25 25.12 N/A SOx 0.18 0.01 N/A 11.18 13.97 N/A VOC 0 0 N/A 26.52 33.21 N/A TAC 12.91 12.20 N/A 14.23 19.09 N/A aThe District did not request revised modeling or emission estimates for Years 8 and 23 on the basis they were not a likely worst case for potential particulate matter impacts on an annual or 24-hour basis and also did not request an annual revised modeling scenario for Year -2 on the same basis. However, the District performed an analysis of Year -2 emissions and impacts when it became apparent that they may have been underestimated in the applicant modeling (see section on AQIA).The December 29, 2011, annual estimates are a more representative estimate of projects annual potential to emit than the previous applicant submittals. However, as noted above, the District has concluded that some emissions have been underestimated, especially particulate matter emissions. The same is true for hourly and daily emissions. However, also as noted above, the District has incorporated conditions, as necessary, in the proposed A/C to ensure that the project’s potential to emit for all pollutants remain below levels that have been demonstrated not cause a violation of an ambient air quality standard or pose a significant health risk.



V. RULES ANALYSIS

DISTRICT AND FEDERAL NSR AND PSD REGULATIONS

Rule 20.1(c)(35)—Major Stationary Source Major stationary source means any emission unit or stationary source which has, or will have after issuance of a permit, an aggregate potential to emit one or more air contaminants, including fugitive emissions, in amounts equal to or greater than any of following emission rates:

Table V-1. Major Source Thresholds

Air Pollutant Major Source Potential to Emit Threshold PM10 100 NOx 50 VOCs 50 SOx 100 CO 100 Lead (Pb) 100

A source that is major for one pollutant is evaluated under Rule 20.3 for purposes of nonattainment NSR and PSD. For nonattainment NSR, major source status is only relevant for pollutants for which the District does not attain an applicable national air quality standard. Since the District attains all national ambient air quality standards with the exception of ozone, nonattainment NSR major source status is only relevant for NOx and VOCs, both of which are ozone precursors.

The applicant has accepted the permit limits in Table V-2 that limit the project’s potential to emit to less than the major source thresholds.

Table V-2. Conditions Limiting Potential to Emit

Pollutant or Process Variable Limit Units Flare Station Fuel Flow 7250 wscfm Flare Station Heat Input 150 MMBtu/hr NOx 0.025 lb/MMBtu VOCs 49.5 tons per year CO 0.06 lb/MMBtu PM10 97 tons per year TRS as H2S 150 ppmvd fuel

Table V-3 shows the maximum potential to emit based on the permit limits above. As can be seen the project is not a major source (estimated lead emissions are far below 100 tpy, see the



HRA report). Hence, the project is evaluated under Rule 20.2 for nonattainment NSR and PSD.

Table V-3. Potential to Emit as Limited by Permit Conditons

Pollutant Annual Emissions, tons NOx 16.4 VOCs 49 CO 39.4 PM10 97 SOx 43.8

Rule 20.1(c)(58)—Prevention of Significant Deterioration (PSD) Stationary Source and 40 CFR 52.21—Criteria Pollutants For a landfill, the PSD Stationary Source status for a new PSD source is defined by an aggregate potential to emit one or more air contaminants in amounts equal to or greater than any of the following emission rates under District rules and under federal rules:

Table V-4. PSD Major Source Thresholds

Air Pollutant Major Source Potential to Emit Threshold PM10 250 NOx 250 VOCs 250 SOx 250 CO 250 Lead (Pb) 250

(Note that District Rule 20.1 does not explicitly address PM2.5 nor does it address TSP. However, PM2.5 is addressed as subset of PM10).

As discussed above, the project does not exceed the major source threshold for any pollutant and, therefore, does not exceed the PSD major source threshold under District rules.

As of July 1, 2011, federal PSD requirements apply to a new stationary source that emits more than 100,000 ton per year of greenhouse gases (GHGs). Gregory Canyon Landfill expected GHG emissions do not exceed the federal PSD stationary source threshold for GHGs based on methane emissions (see Table IV-15). EPA has temporarily exempted biogenic CO2 emissions from determining the potential to emit.

The District is currently not delegated to implement federal PSD by EPA nor does it have a PSD rule that has been approved by EPA. Hence, PSD permitting for federal PSD is solely the responsibility of EPA at the current time. The District’s New Source Review (NSR) rules do contain provisions for PSD that the District implements locally. The proposed project’s



compliance with these provisions is evaluated in accordance with District Rules and Regulations. It is worth noting that, although the District PSD provisions reflect many elements of federal PSD, there are some differences. In particular, the District currently has no authority in its Rules and Regulations to address greenhouse gases (GHGs).

While the District may seek federal delegation of the PSD permitting program in the future, at this time the federal PSD permit remains a separate matter under federal jurisdiction and permitting by the EPA. Thus, EPA would currently be the agency to issue a PSD permit, with no effect on the validity of the District’s issuance of an Authority to Construct.

Rule 20.1( c)(16) Contemporaneous Emission Increase Contemporaneous emission increase is defined in Rule 20.1 (c)(16) as the sum of emission increases from new or modified emission units occurring at a stationary source within the calendar year in which the subject emission units is expected to “commence operation” and the preceding four calendar years, including all other emission units with complete applications under District review and which are expected to commence operation within such calendar year. Since the project is a new stationary source, the Contemporaneous Emission Increase for the GCL stationary source is the same as the project potential to emit.

Rule 20.2(d)(1)- Best Available Control Technology(BACT) Subsection 20.2(d)(1)(i) of the rule requires that Best Available Control Technology (BACT) be installed on a new or modified emission unit on a pollutant-specific and equipment specific basis if emissions exceed 10 lbs/day or more of PM10, NOx, VOCs, or SOx. However, operations at this project are also subject to TBACT for toxic air contaminants (see Rule 1200 below), which is equivalent to LAER a more stringent standard than BACT. BACT was only considered for the flare. Although other operations or equipment proposed for the project might be subject to BACT, their emissions are also subject to TBACT, which satisfies BACT.

For the flare, BACT applies for NOx, SOx, PM10, and PM2.5 as a subset of PM10, emissions because the emissions of those pollutants are more than 10 pounds per day. VOCs are not subject to BACT because the TBACT emission limit reduces the flare’s potential to emit below 10 pounds per day. The District notes that the type of flare used to achieve the TBACT limit is a flare using lean-premix technology that can also meet the NOx BACT limit below. PM10 is subject to TBACT and that limit satisfies BACT. For NOx and SOx, the District has determined that the limits in Table V-5 are BACT for the flare.

Table V-5. Conditions Limiting Potential to Emit Pollutant Limit Basis NOx 0.025 lb/MMBtu Demonstrated in the field TRS as H2S 150 ppmv TRS as H2S in LFG fuel SCAQMD SIP Rule 431.1



Rule 20.2 (d)(2)—Air Quality Impact Analysis (AQIA) This subsection of Rule 20.2 requires that a project resulting in an emission increase equal to or greater than the AQIA thresholds demonstrate through an AQIA that the project will not cause or contribute to a violation of a state or national ambient air quality standard. For the the project, the AQIA thresholds are exceeded for NOx, CO, VOCs, SOx, PM10 and PM2.5. However, the District does not require an AQIA for VOCs pursuant to 20.2 (d)(2)(iv).

For NOx, CO, PM10 and PM2.5, the applicant submitted an emission estimate and an initial analysis of the air quality impacts as Volume VII of the application titled “Updated Air Quality Impact Analysis and Health Risk Assessment for the Proposed Gregory Canyon Landfill” dated September 14, 2010. For purposes of that analysis, it was assumed that 5,000 tons per day of waste were received on each day of operations (i.e., 307 days per year). Based on this assumption, the landfill would reach capacity at the end of the 22nd year after first receipt of waste. The following operating scenarios were analyzed in this submittal:

• Year -2. The first year of construction and projected by the applicant to have the maximum amount of excavation during the Construction Phase.

• Year 1. This is the first year of the Startup Phase and the first year in which MSW is received and placed in the landfill. As projected by the applicant, Year 1 MSW operations are at the northern end close to the northern and eastern boundaries. In addition, during Year 1 there will be continuing construction activities along with the MSW disposal operations. Limited construction is forecast by the applicant to potentially Year 7.

• Year 8. This is potentially the first year without construction. Cover soil in this year is projected to come from stored landfill soil in BAB. The applicant also modeled the longest waste haul road for this year although it could occur in other years.

• Year 17. Cover in this year is projected to be excavated from BAB by the applicant, which results in higher particulate emissions.

• Year 22. This is the final year of operation. The applicant forecasts that cover soil will be excavated from both BAA and BAB in this year.

• Year 23. This is the first year of closure when half the final cover is placed on the landfill (projected by the applicant to be excavated from BAA) and landfill gas generation is likely to be the greatest. After closure, there are no more on-site activities other than cover maintenance and operations and maintenance of the LFGCCS.

Note that the location of MSW operations was modeled at different locations in Years 1 through 22.

Subsequent to the 2010 AQIA submittal, the receipt of MSW was limited to 1,000,000 tons per year, which would extend the life of the landfill to more than 30 years based on the applicant’s estimates. The District estimates a potentially longer lifetime at the the maximum annual waste receipt rate. The actual lifetime will depend on the actual amount of waste received. For convenience, the Model Year nomenclature above was retained in subsequent



modeling and should be looked at as only defining operational scenarios not an actual year in the life of the landfill.

Upon review of the initial submittal, the District determined that the initial applicant modeling submittal failed to fully address the scope of potential ambient air quality impacts and health risks. As a result, the District requested that the applicant conducted a number of supplemental analyses to evaluate other potential scenarios to more fully assess potential ambient impacts that could be greater than those initially analyzed. The ambient air quality analyses included evaluating the potential ambient air quality impact of the following:

• Increased density of waste in place such that the landfill could accept additional waste mass in the same volume, in which case potential landfill gas emissions are greater.

• Increase in vehicle speed to the 15 mph speed limit that the applicant was willing to accept as a permit condition from the 7.5 mph used in the Volume VII modeling.

• More representative vehicle mixes to assess unpaved and paved road emissions.

• More representative location for some sources to better assess emission impacts.

• Operations at Borrow/Stockpile A and B closer to the property boundary than initially evaluated.

• Different internal road configurations and widths and road grades consistent with good engineering practice resulting in longer roads.

• For wind-blown dust (wind erosion) emissions, larger disturbed areas.

• Relocation of the flare station location to that indicated in the JTD.

The District requested the following additional data and supplemental analyses to refine the AQIA. Those additional data submittals are summarized below.

• The District requested additional analysis of wind erosion assumptions, conversion of NO to NO2 from blasting operations and internal road configuration. A response to this request for supplemental information was submitted on January 27, 2011

• The District requested analysis of the potential ambient air quality impacts of on-road vehicles that will be used on-site. A response to this request was submitted on April 11, 2011.

• The District requested additional analysis of the potential fugitive dust emissions from vehicle travel incorporating revised payload and tare weights of the vehicles used to bring refuse into the landfill. A response to this request was submitted on November 4, 2011.

• The District requested additional analysis to refine assumptions concerning vehicle speed, road grades, road widths, material handling at the borrow areas, clay delivery for the landfill liner, revised waste disposal rates and waste density, and additional



disturbed area subject to wind erosion. A response to this request was submitted on December 29, 2011.

• The District requested additional analysis of air quality impacts on additional days during year 22, landfill gas generation rate including use of green waste for daily cover and use of trucks to transport soil instead of scrapers. A response to this request was submitted on January 23, 2012.

• The District requested additional information concerning the timing of the landfill gas collection system installation and start-up. A response to this request was submitted on March 2, 2012.

• The District requested additional information concerning the amount of decomposable waste disposed, the landfill gas generation rate, landfill gas methane content and the landfill gas non-methane organic compound concentration. A response to this request was submitted on March 23, 2012.

• The District requested additional analysis of the air quality impacts of emissions from the flare station including analysis of a flare location consistent with the JTD and revised flare emissions factors. A response to this request was submitted on May 2, 2012.

The District’s initial preliminary evaluation of the Air Quality Impact Analysis involved review of the initial submittal and the additional requested supplemental submittals along with its own analyses including the impacts of SO2, impacts in Class I areas, day-by-day 24-hour PM10 impacts, and impacts of operating after hours. Based on that review and its additional analyses, the district has determined that the landfill will result in no violation of any national or state ambient air quality standard. A summary of the AQIA results is presented below in Table V-6.



Table V-6. Ambient Air Quality Impacts.

Pollutant Back- ground

Maximum Modeled Impact

AERMOD

Total Impact

Operational Year

Meteorological Year

California Standard

Federal Standard

NO2

1-hour 1st High 152 69.8 221.8 Year -2 2002 339 --

1-hour 7th High1 118 69.8 187.8 Year -2 2002 -- 188

Annual 34 1.0 35.0 Year 23 2002 57 100

CO 1-hour 6,743 94 6,837 Year 23 2003 23,000 40,000 8-hour 4,114 22 4,136 Year 23 2003 10,000 10,000

SO2 1-hour 110 106 216 Year 23 2003 655 -- SO2 3-hour 1105 59 169 Year 23 2003 -- 1300

SO2 24-hour 24 12 36 Year 23 2003 105 --

SO2 Federal 1-hour 1105 816 191 Year 23 2003 -- 196

PM10 24-hour 36.9 12.9 49.8 Year 22 October 24,

2003 50 150

However, subsequent to the initial preliminary review, further review of the applicant’s model indicated that there were a substantial number of issues involving operational parameters, emission factors, and modeling scenarios, which are further discussed in Appendix B, that may have resulted in an underestimate of potential emissions and emission impacts for PM10. Because of these issues, the District performed additional modeling and engineering analysis based on the modeling results to identify the maximum potential impacts and emissions. The analysis indicated that both the 24-hour and annual California Ambient Air Quality Standards for PM10 might be violated under some expected potential emission scenarios. Therefore, the analysis results were used to generate parameters (see Appendix B) for the monitoring of potential PM10 emissions emission impacts to ensure compliance with District Rules and Regulations and the California Ambient Air Quality Standards for PM10. Although, PM2.5 emissions and impacts are also affected, the District focused on PM10 because of the small margins between the impacts predicted by the applicant’s monitoring and the 24-hour and annual California Ambient Air Quality Standards for PM10.

The proposed A/C permit conditions, including the PM10 emission and impact monitoring mentioned above, contain hourly, daily and annual emission limits that are applicable at all times to ensure that the project will not cause or contribute to a violation of any National Ambient Air Quality Standard or California Ambient Air Quality Standard. Specifically, 24-hour PM10 impact cannot exceed 50 μg/m3, including a factor to account for background PM10, and the annual impact cannot exceed 2.4 μg/m3.



Rule 20.2 (d)(3)-Prevention of Significant Deterioration (PSD) This provision only applies if the project causes a significant impact in a Class I area as defined in Rule 20.1 (c)(65). As part of its AQIA analysis, the District performed an assessment of the projects potential air quality impacts in the nearest Class I area, Aqua Tibia Wilderness Area, and determined there was no significant impact for any pollutant.

Rule 20.2 (d)(4)—Public Notice and Comment For any project that is subject to the AQIA requirements of Rule 20.2(d)(2), these provisions require that the District publish a notice of the proposed action in at least one newspaper of general circulation in San Diego County as well as send notices and specified documents to the EPA and ARB. Because the project is not subject to Rule 20.2(d)(3) the additional notification requirements of Rule 20.2(d)(3)(iii) are not applicable. Notice of proposed A/C for the Gregory Canyon Landfill will be published in the San Diego Daily Transcript and mailed to EPA and ARB air districts for a 30-day comment period in accordance with Rule 20.2(d)(4).

Rule 20.2(d)(4)(i) requires that the District consider all comments received. The District will consider all comments received before taking final action.

DISTRICT PROHIBITORY RULES

Rule 50—Visible Emissions This rule limits air contaminants emissions into the atmosphere of a shade darker than Ringlemann 1 (20% opacity) to not more than an aggregate of three minutes in any consecutive sixty-minute period.

All operations at the facility are required to meet this minimum requirement and most dust generating operations and equipment are subject to more stringent opacity requirements that have been determined technically feasible by the District. Enclosed flares burning landfill gas are not expected to have visible emissions when operating properly.

The facility is expected to comply with this requirement,

Rule 51—Nuisance This rule prohibits the discharge of air contaminants that cause or have a tendency to cause injury, nuisance, annoyance to people and/or the public or damage to any business or property. Although odors are expected from a landfill, the A/C conditions limiting VOC emissions will minimize their impact. The A/C conditions require an odor control plan, if necessary, to control odors. Based on the above, the facility is expected to comply with this rule.



Rule 53—Specific Air Contaminants This rule limits emissions of sulfur compounds (calculated as SO2) to less than or equal to 0.05% (500 ppm) by volume, on a dry basis from combustion sources and. The rule also limits particulate matter emissions from gaseous fuel combustion to less than or equal 0.1 grains per dry standard cubic foot of exhaust calculated at 12% CO2.

Sulfur Compounds. The proposed A/C conditions limit the total reduced sulfur content of the landfill gas fuel to 150 ppmv or less. Assuming an F-Factor of 9500 standard cubic feet of exhaust gas per million Btu of heat input for landfill gas combustion at 0% O2 in the exhaust, a landfill gas fuel higher heating value (HHV) of 37.37 MMBtu/MMscf (37% methane with a HHV of 1010 Btu/scf), 10% O2 in the exhaust (typical for enclosed flare exhaust), and that all the sulfur in the fuel is converted into SO2, the SO2 emission factor is:

EF(SO2) = 150(64)/385 = 24.9 lb/MMscf

And the concentration of SO2 in the exhaust is:

C(SO2) = (106)[(24.9)/(37.37)](1/9500)(1/64)(385)[(20.95 -10)/20.95] = 220 ppmv

This is well below the Rule 53 limit of 500 ppm SO2 by volume. Therefore, the project is expected to comply with this rule based on the permit condition limiting TRS in the landfill gas fuel, which has been achieved in practice.

Particulates. Assuming a landfill gas composition of 50% methane and 50% carbon dioxide (CO2), dry, and 2% moisture, there is 8.16 dry standard cubic feet of exhaust (dscf) per wet standard cubic foot (wscf) of of landfill gas @ 12% CO2. The particulate matter emission rate is limited to 6 lb/MMwscf of fuel, a standard that has been achieved in practice. Therefore, the grain loading is:

Grain loading = [(10-6 MMwscf/wscf)(6 lbs/MMwscf)(1/8.16) wscf/dscf) (7,000 gr/lb)] / [= 0.005 gr/dscf

This is well below the Rule 53 emission limit of 0.1 gr/dscf @ 12% CO2. Therefore, the flare is expected comply with this rule.

Rule 54 –Dust and Fumes The District has determined that this rule does not apply to landfill operations.

Rule 55 – Fugitive Dust Control This rule does not apply to permitted operations and only applies to the nonlandfill associated operations on the property.



Rule 59—Control of Waste Disposal Site Emissions Rule 59(d)(1)(i). The landfill is equipped with a landfill gas control system using the best available control technology as determined by the Air Pollution Control Officer.

Based on the proposed A/C conditions, the proposed landfill gas collection system and flare is considered TBACT and, hence, satisfy BACT.

Rule 59(d)(2). Every landfill gas control system shall be designed, modified, and extended, when necessary, to prevent underground off site gas migration and to maintain compliance with this rule. Each extension or modification shall be done in accordance with plans and specifications previously submitted to and approved by the Air Pollution Control Officer. Each extension shall be designed to maintain and achieve the level of emissions control required by Rule 59(d)(1)

Based on the proposed A/C conditions, the proposed project is expected to comply with this rule provision.

Rule 59(d)(3). There shall be no landfill gas leaks from the gas wells, piping, flanges, valves, blowers, flame arrestors, pipe fittings, sampling ports, or any other connections or fittings along the landfill gas transfer path of any landfill gas collection, energy recovery, gas purification and/or disposal system which result in concentrations of 500 ppmv or more measured as propane or 1375 ppmv or more measured as methane at a distance of 1.3 centimeters (1/2 inches) from the transfer path, other than non-repeatable, momentary readings.


Rule 59(d)(6). Any gas collection system used in conjunction with a landfill gas control system shall be designed and operated to draw gas toward the gas collection device or devices without overdraw that could cause fires or damage to the landfill gas disposal system.


Rule 59(d)(7). Flares used to control the emissions of landfill gases shall be equipped with automatic shutoff mechanisms designed to immediately stop the flow of landfill gases when a flame-out occurs. During restart or startup, there shall be sufficient flow of propane or commercial natural gas to the burners to ensure that unburned landfill gases are not emitted to the atmosphere.

Based on the proposed A/C conditions, the proposed flare is expected to comply with this rule provision.



Rule 59(d)(8). No person owning or operating a landfill shall allow leachate and/or condensate from the landfill to reach any surface where odors, toxic air contaminants or reactive organic compounds can be evaporated into the atmosphere.

Based on the proposed A/C condtions, the proposed project is expected to comply with this rule provision.

Rule 59(d)(9). Whenever landfill material is to be brought to the surface during the installa-tion or preparation of wells, piping, or other equipment, or when landfill waste is to be excavated and moved, the owner/operator shall first obtain and then follow mitigation measures approved in writing by the Air Pollution Control Officer to prevent public nuisance and to minimize the release of non-methane organic compounds.

Based on the proposed A/C conditions, the proposed project is expected to comply with this Rule.

Rule 68 –Oxides of Nitrogen from Fuel Burning Equipment This rule limits NOx emissions from any fuel combustion equipment that has a maximum heat input rating of 50 MMBtu or more. Permit conditions limit the heat input rating of the flare to less than 50 MMBtu, so this rule is not applicable.

Rule 1200—Toxic Air Contaminants Rule 1200, New Source Review for Toxic Air Contaminants, requires that a Health Risk Assessment (HRA) be performed if the potential to emit toxic air contaminants will increase. A detailed HRA is necessary if toxics emissions exceed District de minimis levels. Toxic Best Available Control Technology (TBACT) must be installed if the HRA shows a cancer risk greater than one in a million at a receptor where a person could be reasonably anticipated to be exposed. The cancer risk is based on a 70-year exposure for a residence and a shorter exposure time for occupational workers. Additional requirements apply if the cancer risk is expected to exceed ten in a million.

The applicant provided two HRAs to the District. The District reviewed these HRAs and concluded they did not provide a representative evaluation of the potential health impacts from the source. As discussed above and in the HRA report, the District performed a supplemental HRA using more representative emission factors and expected emission rates for toxic air contaminant emissions from the project. The HRA performed shows that the maximum incremental cancer risk is 9.1 in a million for the maximum exposed individual resident (MEIR). The acute and chronic incremental health impacts measured by the Health Hazard Index (HHI) are also all less than 1.0 at the point of maximum impact (0.31, 0.13, and 0.9 for the chronic, 8-hour, and acute HHIs, respectively). Because the maximum cancer risk exceeds one in a million, to meet Rule 1200 requirements, TBACT is required on all equipment and processes that contribute to the cancer risk. The TBACT determinations are presented below and the health risk assessment of this project is further discussed in the HRA report.



TBACT. The District has made the TBACT determinations listed in Table V-7.

Table V-7. Summary of Factors Limiting Emissions

Item Limita Units Waste Accepted before LFGCCS Operates 1,500,000 tons Flare NMOC 99% reduction unitless Flare CO 0.06 lb/MMBtu Flare VOC 0.006 lb/MMBtu Flare PM10 6 lb/MMwscf fuel Vehicle Speed 15 mph Paved Main Entrance Road, Silt Loading 0.4 g/m2 Chemically Stabilization Haul Roads Quarterly N/A Unstabilized Haul Roads, Watering Visibly moist N/A Unpaved travel areas, other vehicles 20% opacity unitless Landfill dust generating activities 10% opacity unitless Disturbed areas Stabilized Variousee Leachate and Condensate Collection Vents Connected to LFGCCS

Work practice N/A

No disposal of leachate in the flare Work practice N/A Methane surface concentration 6.0 with background

included, or 4.2 above the local

ambient background

ppmv

Regulation XIV—Title V Operating Permits The Applicant will submit an application for a Title V Operating Permit for this project. The application is due no later than 12 months after the facility begins operation or a shorter period of time if specified by the District.

STATE REGULATIONS IMPLEMENTED BY THE DISTRICT

Health and Safety Code §42301.6 This section of the state Health and Safety Code requires the District to notify parents of students at a school if a new source of air pollution is within a 1000 feet of the boundary of that school. The District has determined that the Gregory Canyon Landfill is not within 1000 feet of any school boundary.



Title 17 of the California Codes of Regulations (CCR) §95460 to 95476 —Methane Emissions from Municipal Solid Waste Landfills This rule is applicable to landfills with 450,000 tons or more waste in place unless they are exempt. This rule will be applicable to Gregory Canyon Landfill. The proposed A/C conditions address the requirements of this rule and the applicant is expected to be able to comply.

NATIONAL EMISSIONS STANDARDS FOR HAZARDOUS AIR POLLUTANTS (NESHAPS)

40 CFR Part 63 Subpart AAAA— National Emission Standards for Hazardous Air Pollutants: Municipal Solid Waste Landfills This subpart establishes national emission limitations and operating limitations for hazardous air pollutants (HAP) emissions from landfills. The proposed A/C conditions address the requirements of this rule and the applicant is expected to be able to comply.

NEW SOURCE PERFORMANCE STANDARDS (NSPS)

40 CFR Part 60- Subpart WWW- Standards of Performance for Municipal SolidWaste Landfills. This rule is applicable to an MSW landfill having a design capacity equal to or greater than 2.5 million megagrams (Mg) and 2.5 million cubic meters and is applicable to Gregory Canyon Landfill. The proposed A/C conditions address the requirements of this rule and the applicant is expected to be able to comply.

VI. CONCLUSIONS AND RECOMMENDATIONS

If operated in accordance with the conditions recommended in the proposed Authority to Construct, this equipment is expected to operate in compliance with all Rules and Regulations of the San Diego County Air Pollution Control District.

Signed by ________

Project Engineer Date



Signed by

Senior Engineer Approval Date



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http://geotracker.waterboards.ca.gov/esi/uploads/geo_report/1085937440/L10009474974.PDF




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http://aqmd.gov/rules/reg/reg04_tofc.html

http://www.aqmd.gov/aer/Updates/SuppInstruforAB2588Facilities.pdf

http://www.aqmd.gov/aer/Updates/SuppInstruforAB2588Facilities.pdf

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Sponza, Delia Teresa & Osman Nuri Ağdağ (2004). “Impact of leachate recirculation and recirculation volume on stabilization of municipal solid wastes in simulated anaerobic bioreactors”, Process Biochemistry, Vol. 39, Issue 12, October 29, 2004, pp.2157-2165. http://www.sciencedirect.com/science/journal/13595113.

Staley, Bryan, Fangxiang Xu, et al (2006). “Release of Trace Organic Compounds during the Decomposition of Municipal Solid Waste Components”, Environmental Science & Technology, Vol. 410, No. 19, pp. 5984-5991. http://pubs.acs.org/journal/esthag.

Tassi, Franco, Giordano Montegross, et al (2009). “Degradation of C2-C15 volatile organic compounds in a landfill cover soil”; ELSEVIR-Science of the Total Environment, July 2009, Vol. 407, Issue 15, pp. 4513-2525. http://www.sciencedirect.com/science/journal/00489697.

Wang, Chien-Kai and Gopal Achari (2012). “A Comparison of Performance of Landfill Gas Collection Wells with Varying Configurations”, The Open Waste Management Journal, November 16, 2012, Vol. 5, pp. 40-48. http://www.benthamscience.com/open/towmj/openaccess2.htm.

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Watson, Dr. John G, Dr. C. Fred Rogers, Dr. Judith C. Chow et al (1996). Effectiveness Demonstration of Fugitive Dust Control Methods for Public Unpaved Roads and Unpaved Shoulders on Paved Roads, Final Report, dated December 31, 1996, Desert Research Institute (DRI) Document No. 685-25200.F1 prepared for California Regional Particulate Air Quality Study (CRPAQS), CARB, Sacramento, CA.

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APPENDIX A

FUGITIVE METHANE EMISSION MONITORING

Eng. Eval. Appendix A Page 2 August 5, 2013


I. BASIS OF FUGITIVE LANDFILL GAS MONITORING

FUGITIVE METHANE EMISSION CALCULATION METHODOLOGY Assuming a simple one-dimensional model, the surface flux of methane from the landfill surface can be expressed as:

𝜖�̇� = ℎ�(𝐶�̅� − 𝐶𝑏) (1)

Where:

𝜖�̇� is the average surface flux of methane over the landfill surface during a specified time period, in tons/acre-hour

ℎ� is the average mass transfer coefficient, in tons/acre-hr-ppm

𝐶�̅� is the average surface methane concentration at some reference height above the surface, in ppm

𝐶𝑏 is the background concentration of methane in the atmosphere, in ppm

Using equation 1, the surface flux from a reference landfill is given by:

𝜖�̇�,𝑟𝑒𝑓 = ℎ�𝑟𝑒𝑓��̅�𝑠,𝑟𝑒𝑓 − 𝐶𝑏� (2)

Where:

𝜖�̇�,𝑟𝑒𝑓 is the average surface flux of methane over the landfill surface during a specified time period for the reference landfill, in tons/acre-hour;

ℎ�𝑟𝑒𝑓is the average mass transfer coefficient for the reference landfill, in tons/acre-hr-ppm; and

𝐶�̅�,𝑟𝑒𝑓 is the average surface methane concentration at some reference height above the surface for the reference landfill, in ppm.

The average mass transfer coefficient depends on the meteorological conditions between the reference height and elevation where the background methane concentration is reached. For landfills located in a similar climate and using the ARB procedure to measure background the long-term average mass transfer coefficient variation between landfills is likely minimized for local landfills because:

• The ARB method restricts meteorological conditions under which the measurements



may be made. • Monitoring in San Diego is nearly always done in the morning after sunrise. • Modeling shows that there is less range in surface concentrations for a given methane

flux under convective conditions, which become dominant after sunrise. • The measurement height is restricted by the ARB method and remains relatively

constant. • The surface concentration measurements are made on several days over a year so on

an annual average basis a differences in mass transfer coefficient will be minimized.

Thus, assuming that the average mass transfer coefficient is constant, dividing equation 1 by equation 2, and rearranging gives:

𝜖�̇� =(𝐶�̅� − 𝐶𝑏)

�𝐶�̅�,𝑟𝑒𝑓 − 𝐶𝑏�𝜖�̇�,𝑟𝑒𝑓 (3)

The average surface concentration emission flux at the reference landfill can be expressed as:

𝜖�̇�,𝑟𝑒𝑓 =�1 − 𝜂𝑟𝑒𝑓�

𝜂𝑟𝑒𝑓��̇�𝑐𝑜𝑙,𝑟𝑒𝑓𝐴𝑟𝑒𝑓

� 𝜖�̇�,𝑟𝑒𝑓 (4)

Where:

𝜂𝑟𝑒𝑓 is the average fractional collection efficiency of the reference landfill during a specified time period;

�̇�𝑐𝑜𝑙,𝑟𝑒𝑓 is the average collection rate of during the specified time period, in tons/hour

𝐴𝑟𝑒𝑓 is the area of the reference landfill over which surface emissions occur, in acres.

Substituting equation 4 into equation 3 gives equation 5:

𝜖�̇� =(𝐶�̅� − 𝐶𝑏)

�𝐶�̅�,𝑟𝑒𝑓 − 𝐶𝑏��1 − 𝜂𝑟𝑒𝑓�


� 𝜖�̇�,𝑟𝑒𝑓� (5)

Equation 5 allows calculation of the surface flux at a given landfill based on the reference landfill parameters and the measured surface concentrations at the given landfill. The total fugitive methane emissions in a calendar quarter for the landfill can be calculated from the surface flux by:



𝐸𝑠,𝑞 = 𝐴𝑠𝑡𝑞(𝐶�̅� − 𝐶𝑏)

�𝐶�̅�,𝑟𝑒𝑓 − 𝐶𝑏��1 − 𝜂𝑟𝑒𝑓�


� 𝜖�̇�,𝑟𝑒𝑓� (6)

Where:

𝐸𝑠,𝑞 is the fugitive methane emissions in the quarter, in tons;

𝐴𝑠 is the area of the landfill emitting fugitive emissions, in acres; and

𝑡𝑞 is the total number of hours in the quarter.

The above methodology can also be used to calculate a collection efficiency from the amount of gas collected at a landfill based on the reference landfill paramters. Preliminary calculations give reasonable results for other landfills in San Diego county, as shown in Table I-1, based on data for the 3rd quarter of 2011 through the 2nd quarter of 2012 for the existing landfills and the reference landfill parameters given in Section II.

Table I-1. Preliminary Estimated Existing Landfill Collection Efficiencies

Landfill Collection Efficieny Sycamore 81% Otay 90% Miramar Phase I (closed) 95% Miramar Phase II 56%

II. REFERENCE LANDFILL AND MONITORING EQUATION

The San Marcos Landfill was chosen as the reference landfill. The reference control efficiency was chosen to be 0.95 (95% control) since the San Marcos Landfill has been closed for several years and has a final cover that complies with regulatory standards. In addition, the average surface methane readings for surface measurements conducted in accordance with the ARB Landfill Rule monitoring procedure are very low for the San Marcos Landfill.

The reference values for the right-hand-side of equation 6 were calculated as annual averages based on data supplied by the facility in the ARB monitoring reports for the 3rd quarter of 2011 through the 2nd quarter of 2012. The values used in the calculation are shown in Table II-1 below.



Table II-1. Reference Landfill Parameters

Parameter Value

Average surface methane concentration, ppmv 3.657 Collection efficiency 0.95 Methane collected, tons 7302 Methane average collection rate, tons/hr 0.831 Area, acres 103.8

Substituting the values in the table into equation 6 and using a background methane concentration of 1.8 ppmv, gives the final monitoring equation:

𝐸𝑠,𝑞 = 4.226 × 10−4𝐴𝑠𝑡𝑞(𝐶�̅� − 𝐶𝑏)

1.857 (1)

Where:

𝐶�̅� is the average surface methane concentration from measurements conducted in accordance with the ARB monitoring protocol over the landfill surface during the quarter.

APPENDIX B

PM10 AIR QUALITY IMPACT AND EMISSION MONITORING

Eng. Eval. Appendix B Page 1 August 5, 2013


I. INTRODUCTION

As discussed below, the District identified a number of issues with the modeling submitted by the applicant on December 29, 2011, and January 23, 2012, (Applicant Supplementary PM10 Modeling). The modeling was requested by the District to address PM10 air quality impact issues that the District determined were not sufficiently addressed in the applicant’s modeling submittal on September 14, 2010 (Volume VII) and reflect changes in the operational parameters (for example, an increase in vehicle speed from 7.5 mph to 15 mph). In reviewing the Applicant Supplementary PM10 Modeling the District identified several issues with the emission factors, operational parameters, and modeling assumptions, which resulted in the modeling not addressing the full extent of PM10 24-hour and annual impacts and an underestimate of the potential to emit for the facility. To address these issues and construct appropriate permit conditions to limit potential emissions and air quality impacts, the District adjusted the emission calculation and model impact to reflect appropriate emission factors and operational parameters. The following general procedure, which is discussed in detail below, was used:

• Identify modeling issues that potentially underestimate emissions or air quality impacts. • Construct new source groups to attribute the emissions and air quality impacts to sources

in sufficient detail to facilitate adjustments. • Rerun the applicable applicant’s model run with the new source groups and identify the

point of maximum impact (PMI). In general, to minimize the time required the applicant’s models were only changed when the District determined that there was no other feasible way to address the modeling issue.

• Rerun the applicant’s model with only the PMI receptor to identify the contribution of each source group to the impact at the PMI.

• Calculate the air quality impact per pound of emissions modeled for each source group (χ/Q) at the PMI. In some cases, where the District concluded that the location of the source in the applicant’s modeling was not representative and significantly underestimated the source’s impacts at the PMI or a source did not exist in the applicant’s model, a suitable surrogate χ/Q was used to provide a representative or conservatively high estimate of the air quality impacts.

• Using the modeled or surrogate χ/Q for each source group, adjust the impact as necessary based on the District’s analysis of emission factors and operational parameters. The District assumed that the PMI did not change for this calculation.

• Calculate an air quality impact factor for each group that is expressed in μg/m3 per some conveniently monitored operational parameter.

• Calculate the overall air quality impacts before limitation by permit conditions based on the representative emission factors and representative operational parameters.

• Use a representative PM10 emission factor for each operation expressed in pounds PM10 emitted per some per some conveniently monitored operational parameter.

• Calculate the overall potential to emit (PTE) before limitation by permit conditions based on the representative emission factors and representative operational parameters.



• Based on the air quality impact factors and emission factors for each group construct permit conditions to limit air quality impacts and emissions to level that assure compliance with District Rules and Regulations including compliance with the state PM10 ambient air quality standards.

In some cases, where the above procedure could not address an issue, the modeling issues was addressed by other permit conditions.

The procedure was used for both annual and 24-hour PM10 air quality impacts. As a general note the PMIs for annual impacts identified in the Applicant Supplementary PM10 Modeling are located on the northern property line nearest the ancillary facilities and the PMIs for 24-hour impacts are located on the western property line for BAA and southern property line for BAB and the Landfill Footprint.

To the minimize the amount of model development required, the above procedure was focused on the Applicant Supplementary PM10 Modeling because the applicant’s Volume VII modeling had a large number of modeling issues that could only be adequately addressed by changing the modeling parameters such as (road locations, source locations, and volume source dimensions). With some exceptions, these issues were addressed in the Applicant Supplementary PM10 Modeling. However, when necessary, the District did revise the Applicant Supplementary PM10 Modeling where necessary to adequately estimate the worst case impacts. In addition, the remodeling was limited to using the 2003 meteorological data set, which had been identified as the data set producing the worst case annual and 24-hour PM10 air quality impacts.

The proposed A/C conditions resulting from the analysis require monitoring of PM10 ambient air quality impacts from PM10 based on parameters for the impact from each source of PM10 emissions. The proposed A/C conditions also limit PM10 ambient air quality impacts to levels that comply with the state annual and 24-hour ambient air quality standards for PM10. Although not explicitly addressed, the proposed permit limits would also effectively limit PM2.5 impacts to levels in compliance with the applicable standards. The propose A/C conditions also limit total emissions of PM10 to less than 95 tons per year and require monitoring based on emission factors as described below to ensure compliance.

II. MAJOR MODELING ISSUES

The major modeling issues addressed are discussed below. The Years referred to below are Modeling Years.



IMPACTS AT THE SOUTH END OF THE LANDFILL Because the Applicant Supplementary PM10 Modeling scenarios did not appear to adequately address impacts at the south end of the landfill, the District constructed modeling scenarios that were based on modified versions of Year 17 (Run Nos. S29 and S31) Applicant Supplementary PM10 Modeling scenarios. The District estimates that in Modeling Year 17 the landfill waste level will be at about 900 feet elevation.

24-Hour Impacts The District’s modeling indicated that when landfill operations occurred at the southern-most end of the landfill there were potentially very high 24-hour PM10 air quality impacts. However, the impacts rapidly decrease with distance from the PMI. The District estimates that the impacts would be compliant with the 24-hour PM10 ambient air quality standard for operations greater than 400 feet from the southern property line. Therefore, the proposed A/C conditions require monitoring of 24-hour impacts from landfill operations to assure the ambient air quality standard is not exceeded for operations within 400 feet of the southern property line.

Annual Impacts The District also modeled a scenario designed to find maximum annual PM10 air quality impacts at the southern end of the landfill during normal operations. The District found that the impacts there were significantly less than at the northern end of the landfill, which remains the location of the highest annual impacts.

MODELING SCENARIOS

Year -2—24-Hour Based on a preliminary assessment of worst-case air quality impacts, the District only requested that the applicant submit a scenario that analyzed 24-hour impacts for PM10 for Year -2 (Applicant Supplementary PM10 Modeling, Model Run S25) for emissions when unloading occurred in the Southwest corner of BAA with the BAA haul road running approximately along the western border of BAA. Based on a subsequent examination of the air quality impacts for Year 22, where air quality impacts were evaluated for both the southwest and northwest corner of BAA for excavation of BAA soil, it was determined that the impacts for operations in the northwest corner are greater than the southwest corner. Therefore, the District used Model Run S33B for Year 22 as a surrogate for air quality impacts from BAA operations (soil unloading and transport of material on the BAA road) in Year -2—adjusting the impacts for the difference in emission factors and amounts of material handled.

Year -2—Annual Based on Volume VII results, the District did not request that the applicant submit a scenario that analyzed annual impacts for PM10 for Year -2. Because of concerns that arose during the detailed review of the Applicant Supplementary PM10 Modeling, the District evaluated the



annual air quality impacts using an annualized version of the 24-hour modeling submitted (Model Run S25) adjusting the impacts for the difference in emission factors and amounts of material handled.

Years 1, 17, and 22, BAB—24-Hour As part of its assessment of air quality impacts at the south end of the landfill, the District assessed impacts near BAB using a modified version of Model Run S31 for Year 17 for air quality impacts in the southeast corner of the borrow area. Based on the applicant’s modeling (Applicant Supplementary PM10 Modeling, Run Nos. S30 and S31), the impacts from operations in the southeast corner of the borrow area are higher than in southwest corner. The modified version had source elevations designed to provide worst-case emissions impacts for any operation in the borrow area (the District estimates that the applicant’s modeling did not) but also used a modified receptor grid that adjusted the applicant’s grid so that there were no receptors inside the facility property line, which are not relevant to regulatory decisions, and refining the borrow area operations volume source by modeling it as a six volume road source instead of a single volume source. This run was used as a surrogate to estimate emissions and air quality impacts from transport and unloading of material from BAB in Year 1 (Run No. S28)—adjusting the impacts for the difference in emissions and amounts of material handled.

Year 22 Working Face Location The location of the working face for the Year 22 applicant modeling is not consistent with the JTD. The working face is located at the 450 foot waste level and is only about 150 feet south of the ancillary facilities area. The JTD figures indicate that this area is filled in Phase I in the first few years of the landfill’s life (in modeling Year 22 the landfill would be over 95% filled). This modeling scenario may be a worst case for assessing annual PM10 air quality impacts near the northern property line and 24-hour impacts in BAA but may not adequately assess emissions impacts in the southern part of the landfill.

In the District’s estimation, the actual working face is much more likely to be located at a waste level of 1000 feet or higher in the southern part of the landfill. BAA is proposed to be used as a source of cover material at this point in the landfills operation along with BAB although the permit conditions would allow for all of the cover material to come from BAA. For cover material from BAA, the cover would have to be transported from the northern edge of the landfill to the working face.

As a surrogate that likely provides a conservatively high estimate of emissions and emissions impacts for cover transport from BAA to the southern part of the landfill, the District evaluation assumes that, for any working face farther south in Year 22 than that modeled by the applicant, the cover transport would utilize the essentially the same route as the that proposed by the applicant for cover transport from BAB Year 22 to the northern working face modeled by the applicant, which follows the proposed JTD main internal waste haul road for much of its length. The District analysis also assumes that this would be a parallel road to the main waste haul road because otherwise any vehicles hauling cover, assumed to be scrapers, following this route to a



working face in the southern part of the landfill would share the road with highway vehicles delivering waste, which may not be a desirable situation. In addition, as a worst-case for emission estimates all the cover material is assumed to come from BAA.

To estimate emissions and air quality impacts for transport of all the cover from BAA, the BAA road transport emissions and impacts were added to the BAB road transport emissions and impacts to assure that the estimate was conservatively high for any working face south of the working face modeled in Year 22. The estimate of additional impacts was based on: (1) the BAB road modeled in Year 22 begins to follow the route of the main waste haul road at about the 900 foot waste level, (2) there is about 8100 feet of BAB road inside the landfill footprint from the Y22 working face to the entrance of BAB, (3) there is an additional approximately 1400 feet of BAB road inside the borrow area, (4) the maximum additional length of the main waste internal haul to the 1100 foot waste level is about 9000 feet from the Year 22 working face; and (5) an estimated additional 200 feet of road would be necessary to connect the BAA road with the main internal waste haul road. Based on this, the BAB road length exceeds the required additional length required to move material from the modeled Year 22 working face to a more plausible working face at the top of the landfill by about 300 feet (8100 + 1400 - 9000 – 200 = 300) and so provides a conservatively high estimate of emissions. Although air quality impacts depend on source location as well as source emissions, the District believes this estimate also provides an adequate estimate of air quality impacts for the transport of cover to the top of the landfill.

SCRAPER SPEED AT END-OF-ROAD The District has requested that all unpaved roads (or travel routes) contain at least a 200 foot section at the operational end with travel on the native surface to account for off-road travel by vehicles to reach their operational area. This is also referred to as end-of-road travel in this evaluation. The travel speed on these surfaces is assumed to be the same as the speed limit of 15 mph applicable to all vehicle travel on the landfill for purposes of estimating the potential to emit. The speed during actual operations (i.e., loading, unloading, compacting, etc.) is estimated to be slower due to operational constraints and is incorporated in earthmoving emission factors.

For the most part the speed used in the Applicant Supplementary PM10 Modeling reflects this. However, the scraper travel speed on the unpaved surface for the last 200 feet at the end of the Borrow Area A (BAA) road in BAA (this road is referred to as the Stock Pile A (SPA) Road in the Year -2 modeling was set at 6 mph. This section of the BAA road contributes significantly to the 24-hour impacts next to BAA. The District notes that the 6 mph used is lower than the 7.5 mph used in Volume VII.

The applicant based the 6 mph speed on the assumption that a scraper would take the 200 feet to reach 15 mph after loading or unloading with the average speed being 6 mph over those 200 feet and would also take 200 feet to slow down before loading or unloading with the same average speed. However, the District notes the following: (1) the District’s draft emission factors provided to the applicant and refined earthmoving emission factors used by the District in this analysis for the subsequent scraper loading and unloading operations that occur after the 200 foot



end-of-road travel already account for a reduced speed as the scraper accelerates from its loading or unloading operations (scrapers are assumed to load or unload and make a 75 foot radius turn—about 225 feet of travel— while accelerating to 15 mph, and then return along the same path followed to load or unload, around 200–350 feet depending on the operation, at 15 mph before beginning travel on the end-of-road surface at 15 mph; (2) scrapers do not typically stop when loading and unloading; (3) an analysis based on available torque for a fully loaded Caterpillar 637G scraper indicates that a fully loaded scraper on level ground can accelerate from an estimated operating speed of 2.5 mph to 15 mph in about 190 feet with an average speed over 200 feet of about 12 mph; and (4) even with a moderate deacceleration rate of 0.1 g a scraper can deaccelerate from 15 to 2.5 mph in about 50 feet with an average speed over 200 feet of about 13.3 mph. Therefore, the District concludes that 15 mph is a reasonably conservatively high estimate for estimating the potential to emit PM10 for scraper end-of-road travel and has adjusted the applicants emission estimates accordingly in the analysis.

LINER INSTALLATION The applicants EF for estimating PM10 emissions from liner installation included an additional control factor of 90% for the bulldozer-based EF based on high water content. However, this overestimates the control efficiency because the bulldozer EF equation already includes a control factor for water content . Also, the applicant’s modeling emission calculations do not appear to include liner unloading, potential scarification of the liner lifts, and all the operations associated with installation of the soil protective working surface. Based on the District’s preliminary refined estimate resulting from the engineering evaluation, which incorporates control efficiencies to address the high moisture content of the clay liner on installation, the emission factor for clay liner installation is underestimated by about a factor of five. The District adjusted these emissions accordingly (Years -2, and 1—Model Runs S25, S26, S27, and S28).

LANDFILL EARTHEN FILL OPERATIONS The applicant’s emission factor for earthen fill to shape the landfill footprint only includes unloading emissions from a scraper and does not include subsequent operations such as bulldozer spreading and compaction. The District adjusted these emissions accordingly

EARTHMOVING AMOUNTS

Daily Earthmoving Volumes The District believes that the potential maximum daily earthmoving volumes are likely significantly underestimated in some cases. For example, in Year -2, the daily modeled maximum volume of excavated material transported to BAA was 5000 banked cubic yards (BCY) per day (the District assumes that all excavation volume proposed by the applicant are expressed as BCY, which is customary). However, the daily average amount of material sent to BAA in Year -2 is about 4400 BCY while the total maximum daily soil excavation proposed by the applicant in Year -2 was 10,000 BCY—all of which could be sent to BAA on any given day.



In addition, the applicant’s proposed daily maximum soil excavation only represents the daily average excavation rate (soil plus rock) for Year -2. The amount of material excavated depends on the mix of equipment employed and the cycle time for the excavation, loading, and transport of the excavated material and could easily be significantly larger than the daily average. The District adjusted the amounts of material excavated and transported in the construction years modeled (Year -2 and Year 1) to estimated reasonable maximum rates including 10,000 BCY per day transported over the BAA road in Year -2.

Annual Earthmoving Volumes The District preliminarily accepts the applicant’s proposed annual earthmoving volumes as providing a reasonable estimate of potential annual emissions and air quality impacts.

YEAR 1 POTENTIAL COVER MATERIAL USE Although receipt of 1,000,000 tons of waste per year were modeled to assess the maximum annual impacts, only 211,614 cubic yards (cy) of soil cover was assumed to be used to model emissions from cover operations compared to 324,868 cy of cover in other years for the same amount of waste. For purposes of estimating potential to emit, it is assumed that an approximate 4/1 cover ratio will be required, including soil and PGM (or other alternative cover) for all years. Therefore, the same amount of cover will be required in Year 1 as in other years. The District assumed that 324,868 banked cubic yards (BCY) of soil cover was used in its analysis.

Similarly, although 5,000 tons of waste received per day was modeled to assess the maximum 24-hour PM10 air quality impacts, only 1204 BCY of soil cover was assumed to be used as compared to 1852 BCY of soil cover for other modeling years to assess the maximum 24-hour impacts. The District incorporated this assumption in its analysis. The District assumed that 1852 BCY of soil cover was used in its analysis.

BAB ROAD OPERATIONS A major portion of the potential emissions and 24-hour air quality impacts from Borrow Area B (BAB) road in Years -2 and 1 were not accounted for in the modeling based on the applicant’s argument that blasting was the worst case and no blasted rock would be transported on the BAB road on a day when there was blasting (in Year 1 only a portion of the BAB road was excluded). Thus, the modeling only accounted for road grading emissions, which are much smaller than other road emissions. However, the maximum daily PM10 emissions from the blasting modeled is much smaller that the BAB road emissions (for example, in Year -2 the estimated blasting emissions are 8.27 pounds per day while daily average BAB emissions are greater than 280 pounds). More importantly, the impacts on the days when the maximum 24-hour impacts occurred from blasting are zero while impacts from BAB road emissions are not (the blasting impact can be zero when impacts from other sources located nearby are not because blasting is limited to a smaller portion of the day than other operations and, if the wind is not in the right direction during those hours there is no impact). To address this issue, the District estimated impacts and monitoring parameters from full potential use of the road from the modeling based



on proportionally scaling up the road grading air quality impacts and calculated potential emissions based on full use of the BAB road. (Years -2, and 1—Model Runs S25, S26, S27, and S28)

ROAD GRADES, LENGTH, AND ELEVATION, MODELING PARAMETERS

BAB Road Elevation Based on the elevations of the existing and excavated terrain, the BAB road route within the landfill footprint used in the applicant’s Year -2 modeling appears to follow the elevation of the landfill waste surface after the landfill has been filled rather than the excavated or existing terrain representative of Year -2. Because the elevation of a source relative to receptors can have a significant effect on air quality impacts, Year -2 was remodeled with the volume sources’ elevations representing the BAB haul road adjusted to lie on the existing or excavated terrain, as applicable, to assess maximum potential air quality impacts from the BAB road in Year -2. The route of the road was not changed although a shorter road on the excavated or existing terrain appears feasible for Year -2.

Internal Haul Roads Grades and Lengths Based on good engineering practice and also consistent with the JTD, the District recommended a maximum of 15% road grades for internal haul roads with the exception of the main waste haul road where 7% is more appropriate for commercial traffic. An examination of haul road gradients on either existing, excavated, or waste filled terrain, as applicable, indicated that several sections of the internal haul roads had gradients exceeding 15%. As previously discussed with the applicant, the District does not view such grades as reasonable on haul roads. Several states limit sustained grades for mine roads to 15%. A more typical grade is 8–10%. This issue was addressed by proportionally increasing the total road lengths to correct for portions of the road with greater than a 15% gradient and multiplying potential emissions and air quality impacts accordingly. For example, the District estimates that the road length and hence emissions from the BAB Haul road in Year -2 would increase by about 40% if all grades were reduced to 15% or less and the same general route is followed.

Paved Main Access Road Grade One short section of the waste haul road, about 100 feet from where it enters the landfill footprint and joins the chemically stabilized portion of the main unpaved waste haul road (or main haul road in Year -2), appears to have a grade significantly exceeding 7% (about 15%). The applicant’s model input file indicates an elevation of 113 m for the first volume source for the chemically stabilized unpaved road in Year 1 while the JTD fill plan figures indicates it is approximately 122 m, near the center of the volume source. This issue was not addressed since it appears feasible that the applicant could address it without lengthening the road (a ramp for example).



Paved Main Access Road Location. As modeled in the paved road does not pass through the weigh station (it is about 100 feet south) and cuts off the northeast corner of this road as laid out in the JTD. This is significant since the northeast corner is closer to the PMI for the annual PM10 air quality impacts at the northern end of the landfill. The proposed A/C permit conditions contain a condition to constrain the location of the Main Access Road to the location modeled.

Paved Main Access Road Lateral Dispersion Parameters Instead of using the initial lateral dimension and dispersion representative of the road from the end of the bridge to the ancillary facility entrance as recommended by the District and EPA guidance, the applicant located four volume sources with those dimensions within the ancillary facility itself and left the volume sources from the bridge to the ancillary facility entrance the same as all other volume sources on the paved road. Neither is representative. However, preliminarily, District modeling that examined the impacts for other sources in the applicant modeling using different initial lateral dispersion parameters showed the initial lateral dispersion made very little difference in the results. This likely depends on the distance of the source to the PMI. The District has preliminarily concluded that the initial lateral dimensions used for the paved road do not significantly affect the modeling results.

Volume Source Spacing for Roads In many cases, the spacing of the separated volume sources representing haul roads does not strictly correspond to EPA modeling guidance in the Applicant Supplementary PM10 Modeling. However, EPA guidance for the Industrial Source Complex Model indicates that, if the PMI is more than three times the volume source separation distance from the volume sources, the spacing makes little difference. The applicant’s modeling did appropriately space the sources when the impacts were potentially close to the road (i.e., for 24-hour impacts in the borrow areas). Preliminarily, the District has concluded that the spacing of volume sources is adequate to model the PM10 air quality impacts.

Waste Haul Road Elevation In Year 17, the waste haul road elevations appear to be about 50 feet too low for much of its length based on the JTD. The District did not correct for this discrepancy. Annual air quality impacts at the northern end of the landfill and southern end of the landfill would likely be slightly decreased and slightly increased, respectively, if the road elevation was adjusted upward. There would be little effect on the 24-hour air quality impacts in Borrow Area B.

MSW OPERATION EMISSIONS Based on the District’s preliminary refined estimate resulting from the engineering evaluation, the Emission Factor (EF) for PM10 emissions from unloading, spreading, and compacting waste



is potentially greater than the 1.37 lb/1000 tons used in the modeling. The emissions were adjusted appropriately based on the District emission factor. (Years 1, 17, and 22—Model Runs S26, S27, S28, S29, S30, S31, S32, S33, S34, S33A, S34A, S33B, S34B,)

ROAD FUGITIVE DUST EMISSION CONTROL FROM PRECIPITATION As previously discussed with the applicant, the additional emission control factor for unpaved roads for days of precipitation is not applicable for purposes of estimating potential emissions on an hourly or 24-hour basis. However, it appears to have been included for all unpaved roads in the 24-hour modeling for Year -2. As noted in the engineering evaluation, the District has preliminarily determined that this control factor is also not applicable on an annual basis for areas that are already heavily watered such as all portions of unpaved haul roads that are not chemically stabilized. Emissions and modeled air quality impacts were adjusted to address this issue for all years modeled.

POTENTIAL COVER TRANSPORT FROM AN INTERMEDIATE STORAGE PILE The applicant’s modeling does not explicitly address the potential for cover to be stored at an intermediate storage pile in the landfill footprint before being transported to the working face, which is likely to be more extensive for soil cover when the landfill footprint is still being excavated. The District assumes that direct cover haul road modeled in Year 1 is a suitable surrogate to estimate emissions and air quality impacts for such transport. This is expected to provide conservatively high estimates for future years as the working face moves toward the south end of the landfill the main unpaved, stabilized road would be extended farther south with a likely reduction in the length of the road necessary to move cover from an intermediate storage pile to the working face. The proposed A/C conditions include conditions to monitor the emissions from such road travel. The District included a source using in Year 1 modeling using a surrogate χ/Q for the possibility of intermediate storage pile operations.

LINER AND LINER PROTECTIVE LAYER TRANSPORT The applicant expects that all clay liner material will be imported and must be transported to its point of installation. In addition, the soil for the protective cover must be transported from its point of excavation to the point where it is installed over the liner. In Year -2, the transport of the liner to its point of installation is implicitly accounted for by transport of any material over the main entrance road, and the main unpaved haul road within the landfill footprint. However, the transport of the protective soil layer (or other material associated with the liner such LCRS gravel layer) are not accounted for in the modeling. To address this issue, the proposed A/C permit conditions require any material other than material for an engineered fill that travels over an internal material haul road be monitored in addition to material travelling over the main internal haul road. For purposes of estimating emission s and air quality impacts, the emission factors for the main internal haul road were used as a conservatively high surrogate for these roads.



For Year 1, potential emissions for the transport of liner material over the main entrance road, and the main unpaved haul road within the landfill footprint up to the landfill working face are accounted for in the modeling. However, further transport to the center of area where the liner is being installed does not appear to be accounted in the modeling since the center of the liner installation as proposed by the applicant is about 3000 feet by road from the working face. To address this for Year 1, it was assumed that travel on the cover haul road that runs from near the center of excavation proposed by the applicant was a suitable surrogate for liner related transport and that the fill haul road modeled was a suitable surrogate for the soil transport for the liner protective cover. The proposed A/C permit conditions require monitoring of transport of any bulk material within the landfill footprint using the emission and air quality impact factors for cover road as a surrogate in all years of landfill operations.

YEAR 1 DIRECT COVER ROAD AIR QUALITY IMPACTS The two sources, DC1 and DC2, representing travel on the off-road travel on the landfill surface after the end of the Direct Cover Road (bringing cover material directly from landfill excavation to the working face) modeled are inserted between DC6 and DC3 rather than at the end of the road by the working face. This underestimates the impact of these higher emitting sources for the annual air quality impacts since they are farther from the annual PMI. The end of the road is comprised of the sources DC3, DC4, and DC5. The District used the χ/Q for the landfill working face operations as a conservatively high surrogate to estimate the air quality impact from these sources.

Year 1 BAB Road Rock Road Traffic. The Year 1 modeling contains a BAB road (labeled SPBRD in the Year 1 modeling) that carries both rock and soil and an extension for transporting rock only (BAB rock road—this is labeled RKRD in the modeling). However, BAB road does not appear to be near the center of mass of the excavation area. Hence, the District assumes that vehicles handling soil will also use the BAB rock road or another road to reach the start of the BAB road. To account this, the District assumed all material both rock and soil traveled over the combined BAB road and the applicant’s BAB rock road in its analysis.

Number of Volume Sources. Although the emissions per volume source for the chemically stabilized portion of the BAB road were calculated based on 37 volume sources, it appears that only 32 volume sources with this calculated emission rate per volume source were actually included in the model input file. Volume sources SPB20–SPB24 are missing. However, the Ditrict estimates that the actual chemically stabilized BAB road length is only about 2100 feet rather than the 2400 feet modeled so the emissions per volume source are adequately represented. The District retained the 2400 feet length in its calculation as a conservatively high estimate of emissions.

Off-Road End-of-Road Travel. Although included in the applicant’s emission spreadsheet and input parameter spreadsheet, for the annual Year 1 model run there are no sources in the model input file sources representing off-road travel on the borrow area (storage pile) unpaved surface



at the end of the BAB Road. The District had requested a default of at least 200 feet be used for such off-road travel at the end of roads. The District adjusted emissions and air quality impacts to account for this in its analysis.

ROCK CRUSHING EMISSIONS It appears that rock unloading and loading in scrapers for subsequent transport to a borrow area or other location was not accounted for in the rock crushing emissions. The District adjusted the emission factors for rock crushing in the construction phase and the rock crushing in later years in BAB to account for this.

Landfill Footprint Rock Crushing Off-Road Travel The District included 200 feet of off-road travel at the end of both the BAB rock road and the BAB road where they join to account for potential off-road transport of rock to the rock crushing operation and the transport of crushed rock to BAB. Two volume sources at the end of the BAB rock road where it joins the BAB road and three sources at that point for the BAB road were used as surrogates for this transport (the rock crushing operation is nearby the point the roads join). The length of the BAB and BAB rock road were proportionally increased to account for the missing volume sources in estimating the emissions and air quality impacts from the BAB road and the BAB rock road.

BAB Off-Road Travel The rock was assumed to be unloaded and loaded with scrapers. In BAB, emissions for an additional 200 feet of travel over the borrow area surface was added to account for transport of rock to the rock crushing location was included in the rock crushing emission factor for BAB. (Years -2, 1, and 17—Model Runs S25, S26, S27, S28, S29, S30, and S31)

BLAST SIZE For Year -2 only a quarter acre blasts were modeled while half acre blasts are contemplated. The proposed A/C permit conditions limit the amount explosive use each day to address this issue.

ALTERNATIVE COVER HANDLING The facility is permitted to receive 90,565 tons of Processed Green Material (PGM) per year and 295 tons per day as alternative cover material. It appears that the handling of this material or other alternative cover is not explicitly accounted for in the modeling. However, the District has concluded that the handling of soil is an adequate surrogate for the unloading, spreading, and compacting of PGM (or other alternative cover) at the working face since it is likely silt contents



of the alternative cover are less than the contents used for the landfill soil (20.7%) or borrow area soil (33%).

The emissions from the potential for PGM to be unloaded at an intermediate storage pile (see below) and then loaded there for transport to the working face are not accounted for in the modeling. However, the unloading emissions and their associated impacts are not likely to be significant at the annual PMIs at the northern end of the landfill or the 24-hour PMIs near the borrow area boundary lines. For loading of PGM at an intermediate storage pile, the emissions displace loading emissions of soil for use as cover either from within the landfill footprint or one of the borrow area. Therefore, the District has concluded that exclusion of these emissions are not significant.

ROAD GRADING EMISSIONS The District corrected road grading overestimates and underestimates from apparent calculation errors in the applicant’s emission calculation spreadsheet. Road grading emissions are not a significant contributor to overall emissions.

VOLUME SOURCE DIMENSIONS FOR EARTHMOVING AND WASTE HANDLING Volume source dimensions used to model some loading and unloading operations in the Applicant Supplementary PM10 Modeling may be too large. The emissions from these operations occur during vehicle travel. Using a road representation of multiple volume sources with internal haul road dimensions and associated lateral dispersion parameters would be more representative, However, based on a preliminary assessment by the District, the volume sources used in the modeling are likely adequate for sources located relatively far from the PMI, which is the case for annual impacts.

BORROW AREA RECEPTOR GRID LOCATIONS

BAA Based on County parcel data and the receptor grid locations, the first row of receptors is not located on the BAA western property line, which underestimates impacts there. The District remodeled impacts for the worst case 24-hour scenario (Year 22, S33B) with a new receptor grid that adequately assesses impacts on the property line.

BAB and Southern End of Landfill The first rows of receptors are located inside the southern property line nearest BAB and the southern tip of the landfill footprint. This likely significantly overestimates the 24-hour PM10 air quality impacts for BAB and the southern end of the landfill. In its modeling of 24-hour PM10 and annual impacts at the southern end of the landfill the District adjusted the applicant’s grid and inserted new receptors, as warranted, to assess the air quality impacts.



III. ADJUSTED PM10 AIR QUALITY IMPACTS AND EMISSIONS

ANNUAL PM10 IMPACTS AND EMISSIONS The annual PM10 air quality impacts and emissions are shown in Table III-1 for the Applicant Supplementary PM10 Modeling, as adjusted or remodeled by the District. The values shown do not consider the proposed A/C conditions that require monitoring annual air quality impacts and limit annual PM10 air quality impacts to 2.4 μg/m3 or less to ensure compliance with the state ambient air quality standard of 20 μg/m3 when added to the 2003 PM10 background of 17.6 μg/m3. As can be seen, without the limit the air quality impacts could potentially result in an exceedance of the standard for several modeled scenarios. The proposed conditions also limit annual PM10 emissions to 95 tons per year. It should be noted that all PMIs occur on or near the northern property line closest to the ancillary facility’s area.

Table III-1. Adjusted Annual Air Quality Impacts and Emissions

Model

Year Model Run as Adjusted by

District

Total Potentia

l Air Quality Impact at PMI, μg/m3

Total Unmonitored Potential Air Quality Impact at

PMI, μg/m3

Total Potential

PM10 Emissions, tons/year

Total Unmonitored Potential

PM10 Emissions, tons/year

-2 S25 Annual Surrogatea 4.196 0.1421 137.94 6.13 1 S26b 3.886 0.0678 125.81 10.92

17 S29c 2.496 0.0001 79.25 5.46 17 S29 SouthEndd 2.422 0.0002 78.37 5.46 22 S32e 2.250 0.0008 47.14 5.86

22 S32 Nearly Full Landfill Surrogatef 3.158 0.0012 99.77 4.91

aA District annualized version of the applicant’s Run S25, which assessed 24-hour impacts, with the emissions adjusted appropriately to estimate maximum potential annual impacts during Phase I construction. bTo represent Phase II construction, when waste is received along with tconstruction. cTo represent operations when landfill is about 80% full. The District estimates that the waste will have reached an elevation of about 900 feet at this time. dDistrict modified version of S29 designed to assess potential impacts at the southern end of the landfill. eTo represent operations when the landfill is 95% or more filled. Working face was located by the applicant near the northern end of the landfill at an elevation 450 feet, which in the District’s estimate is not likely. fThis scenario is the District’s estimated impact and emissions if the working face is located at the southern end of the landfill at an elevation of 900 feet or more (i.e., landfill is about 80% or



more filled) and all the cover material is transported from BAA to the working face along a route paralleling the internal waste haul road a variation of S22.



24-HOUR PM10 IMPACTS AND EMISSIONS Table III-2 shows the scenarios considered in determining compliance with the state 24-hour air quality standard which the District believes represent likely worst-case impacts for various landfill configurations and operational states. The 24-hour PM10 air quality impacts and emissions are shown in Table III-3 and III-4, respectively, for the Applicant Supplementary PM10 Modeling, as adjusted or remodeled by the District. The values shown do not consider the proposed A/C conditions that require monitoring 24-hour air quality impacts and limit 24-hour PM10 air quality impacts plus background to 50 μg/m3 or less to ensure compliance with the state ambient air quality standard. As can be seen, without the limit the air quality impacts could potentially result in an exceedance of the standard.

Table III-2. Adjusted 24-Hour Model Runs

Year

Model Run as Adjusted by

District

Source Location

Most Affecting

Impact Scenario PMI Date

-2 S25 BAAa

BAA unloading in SW corner of BAA (Similar to S34 location for excavation and loading) 10/24/2003

-2 S25 BAA BAA unloading in NW corner, S33B χ/Q used for BAA sources. 10/24/2003

1 S27 BAB

BAB unloading in SW corner of BAB (Similar to S30 location for excavation and loading) 10/24/2003

1 S28 BAB

BAB unloading in SE corner of BAB, S31S.End X/Q used as surrogate BAB operations (except BAB road). 10/24/2003

17 S31 BAB BAB excavation and loading SE corner of BAB 10/24/2003

17 S31 SouthEnd BAB

BAB excavation and loading SE corner of BAB, assessed at PMI nearest BAB 10/24/2003

17 S31 SouthEnd

Landfill operations near southern property line

Landfill operations at southern most part of landfill, assessed at PMI nearest landfill operations 3/4/2003

22 S33BNewGrid BAA BAA excavatiion and loading in 10/24/2003



NW corner. aSource emissions for BAB were not adequately modeled for 24-hour impacts in Year -2. However, Year 1 is a likely worst case. Table III-3. Adjusted 24-Hour Air Quality Impacts

Year

Model Run as Adjusted by District

Source Location Most Affecting Impact

Total Potential Impact at

PMI, μg/m3

Background, μg/m3

Potential Impact +

Backgrounda, μg/m3

Total Unmonit

ored Potential Impact, μg/m3

-2 S25 BAA 35.66b 36.9 72.56 4.62 -2 S25 BAA 32.65 36.9 69.55 3.39 1 S27 BAB 13.35 36.9 50.25 3.76 1 S28 BAB 15.58 36.9 52.48 0.55

17 S31 BAB 7.79 36.9 44.69 0.73 17 S31 SouthEnd BAB 13.08 36.9 49.98 1.71

17 S31 SouthEnd

Landfill operations near southern property line 96.71 9 105.71 0.23

22 S33BNewGrid BAA 20.07 36.9 56.97 0.80 aThe state standard is 50 μg/m3. bAlthough the modeled impact for this scenario is higher than the unloading scenario in the northwest corner (S33BNewGrid surrogate), the District believes the northwest corner scenario is the worst case because S33BNewGrid includes a 145 setback, per proposed A/C conditons, for sources from the property line. The southwest scenario impacts would be significantly reduced with an 145 foot set back.



Table III-4. Adjusted 24-Hour Emissions

Year Model Run as Adjusted by District

Source Location Most Affecting Impact

Total Daily Emissions Including All Sources Except Wind Erosionb,

lb/day -2 S25 BAA 2581.91 -2 S25 BAA 2325.07 1 S27 BAB 1594.29 1 S28 BAB 1537.72 17 S31 BAB 784.93 17 S31 SouthEnd BAB 877.41

17 S31 SouthEnd Landfill operations near southern property line 877.41

22 S33BNewGrid BAA 376.92a aThese are the emissions are for a working face location near the northern end of the landfill at a waste elevation of 450 feet as in the applicant’s annual scenario for Run S32. bWind erosion is not included because it did not contribute to the worst-case 24-hour impacts.

For a southern a working face location in Year 22, when the landfill is almost full, the emissions would likely be much greater than the S33B scenario in the table above. . For a working face at or above 900 feet, as the District estimates is more likely, the District estimates the maximum potential emissions would be about 1000 pounds per day based on the District’s annual estimated emissions for S32 (see above). Although the District has not assessed effect of these additional emissions on the 24-hour impact near BAA, they are unlikely to be significant because of the distance of the sources from PMI. It should be noted that, for the low-level fugitive emission releases from the main PM10 sources, the 24-hour air quality impacts drop off rapidly with distance. For example, figure 1 shows air quality impacts as a function of distance from the BAA property line for RunS33BNewGrid.



Figure III-1. 24-Hour PM10 Air Quality Impacts Near BAA Measured from PMI on Property Line for S33BNEWGRID Model Run.



IV. AIR QUALITY FACTORS GENERAL CALCULATION PROCEDURE

The air quality impact factors are based on an applicable emission factor for the parameter chosen as the monitoring parameter and an atmospheric dispersion factor derived from the ambient air quality modeling results, often referred to as χ/Q. The general procedure below was used to calculate monitoring air quality impact monitoring parameters from the various air quality modeling runs.

GENERAL The modeled pollutant concentration (air quality impact) at a receptor from a source is given by:

𝜒𝑚,𝑖𝑗 = 𝑄𝑚,𝑖𝐷𝑖𝑗 (1)

Where:

𝜒𝑚,𝑖𝑗 is the modeled pollutant concentration at the j’th receptor resulting from the i’th source’s modeled emissions averaged over a specified time period, in μg/m3;

𝑄𝑚,𝑖 is the modeled pollutant emission rate from the i’th source for the specified time period, in appropriate units (e.g., lbs/day or lbs/year); and

𝐷𝑖𝑗 is the atmospheric dispersion factor at the j’th receptor for the i’th source’s emissions averaged over a specified time period, in appropriate units (e.g., (μg/m3)/(lbs/day) or (μg/m3)/(lbs/year)

The atmospheric dispersion factor is then given by:

𝐷 𝑖𝑗 = 𝜒𝑚,𝑖𝑗 𝑄𝑚,𝑖⁄ (2)

For a different source emission rate the pollutant concentration is given by:



𝜒𝑖𝑗 = 𝑄𝑖𝐷𝑖𝑗 (3)

𝑄𝑖 = 𝑃𝑖𝐹𝑝,𝑖 (4)

or

𝜒𝑖𝑗 = 𝑃𝑖𝐹𝑝,𝑖𝐷𝑖𝑗 (5)

Where:

𝜒 𝑖𝑗 is the pollutant concentration at the j’th receptor resulting from the i’th source’s emissions averaged over a specified time period, in μg/m3;

𝑄𝑖 is the pollutant emission rate from the i’th source for the specified time period, in appropriate units (e.g., lbs/day or lbs/year);

𝑃𝑖 is a parameter to monitor the emissions from the i’th source for the specified time period, in appropriate units (e.g., tons of material); and

𝐹𝑝,𝑖 is an emission factor for the i’th source expressed in units appropriate to the monitoring parameter for the specified time period, in appropriate units (e.g., lbs/ton);

The total impact at a receptor is given by:

𝜒𝑗 = �𝑃𝑖𝐹𝑝,𝑖𝐷𝑖𝑗

𝑛

𝑖=1

(6)

Or,

𝜒𝑗 = �𝑃𝑖𝐼𝑝,𝑖𝑗

𝑛

𝑖=1

(7)

Where:

𝐼𝑝,𝑖𝑗 = 𝐹𝑝,𝑖𝐷𝑖𝑗 (8)

And where:



𝜒𝑗 is the total pollutant concentration at the j’th receptor resulting from all the sources’ emissions averaged over a specified time period, in μg/m3;

𝑛 is the total number of sources; and

𝐼𝑝,𝑖𝑗 is an air quality impact factor for the i’th source over the specified time period, in appropriate units for the monitoring parameter [e.g., (μg/m3)/ton if the monitoring parameter was tons of material handled].

REGULATORY COMPLIANCE To comply with the ambient air quality standards the total pollutant concentration must be less than the standard at all locations under all operating conditions and source configurations, which can be written as:

𝜒𝑗(𝑃𝑀𝐼) + 𝐵 ≤ 𝜒𝑠 (9)

𝜒𝑗(𝑃𝑀𝐼) = �𝑃𝑖𝐼𝑝,𝑖𝑗(𝑃𝑀𝐼)

𝑛

𝑖=1

(10)

Or,

𝐵 + �𝑃𝑖𝐼𝑝,𝑖𝑗(𝑃𝑀𝐼)

𝑛

𝑖=1

≤ 𝜒𝑠 (11)

Alternatively,

�𝑃𝑖𝐼𝑝,𝑖𝑗(𝑃𝑀𝐼)

𝑛

𝑖=1

≤ 𝜒𝑠 − 𝐵 (12)

Where:



𝜒𝑗(𝑃𝑀𝐼) is the total pollutant concentration at the receptor located at the point of maximum impact (PMI) averaged over a specified time period, in μg/m3;

𝐵 is the applicable background pollutant concentration for the specified time period, in μg/m3;

𝜒𝑠 is the ambient air quality standard, in μg/m3;

𝐼𝑝,𝑖𝑗(𝑃𝑀𝐼) is the air quality impact factor at the receptor located at the point of maximum impact resulting from the i’th source emissions averaged over the specified time period, in appropriate units.

If some of the sources’ emissions are not monitored, equations 9 and 10 can be rewritten as:


𝑚

𝑖=1

+ 𝜒𝑃𝑇𝐸 + 𝐵 ≤ 𝜒𝑠 (13)

And,


𝑚

𝑖=1

+ 𝜒𝑃𝑇𝐸 ≤ 𝜒𝑠 − 𝐵 (14)

Where:

𝜒𝑢𝑚(𝑃𝑇𝐸) = � 𝑄𝑃𝑇𝐸,𝑖𝐷𝑖𝑗(𝑃𝑀𝐼)

𝑛

𝑖=𝑛−𝑚

(15)

And where:

𝜒𝑢𝑚(𝑃𝑇𝐸) is the pollutant concentration resulting from the emissions of all the unmonitored sources (unmonitored air quality impact) operating at their potential to emit during the specified time period; in μg/m3;

𝑚 is the total number of monitored sources; and

𝑄𝑃𝑇𝐸,𝑖 is the maximum potential to emit of the i’th nonmonitored source; in appropriate units.

Equations 8 and 15 were used to determine applicable air quality impact factors and unmonitored air quality impacts to monitor emissions. Equations 13 and 14 were used to construct permit limits based on the monitored air quality impacts for the state daily and annual PM10 air quality standards, respectively.



Because there are several potentially relevant background concentrations during the year, equation 13 was used to construct the permit limits for the state 24-hour PM10 ambient air quality standard of of 50 μg/m3. The background concentration on the day on which compliance was most sensitive to emission increases and decreases (see below) was in constructing the air quality impact monitoring conditions for each location sensitive to 24-hour PM10 air quality impacts. Because of standard round-off procedures the compliance would actually be demonstrated for an air quality impact plus background of less than 50.5 μg/m3. The built-in margin depends on the background on the day that is the basis of the monitoring, but would be less than 5%. However, the District notes that the maximum 24-hour impacts only occur when operations are close to one of the property boundaries and would not occur on most days.

For the state annual PM10 ambient air quality standard of 20 μg/m3, equation 14 was used to construct the permit limit using the background PM10 concentration for 2003 of 17.6 μg/m3. This results in a limit of 2.4 μg/m3. Because of standard round-off procedures the compliance would actually be demonstrated for an air quality impact of less than 2.9 μg/m3, so the limit has a built-in margin of about 20%.

SELECTING MODELED DAY FOR MONITORING 24-HOUR IMPACTS Because this facilities 24-hour maximum potential air quality impacts are relatively large compared to the state daily ambient air quality standard of 50 μg/m3, there are several days during the year when the standard could potentially be exceeded when added to the background for that day. To select one day on which to base air quality impact factors and use for ambient background the following equations were used:

𝜒𝑚(𝑚𝑜𝑑),𝑘 = �𝑄𝑃𝑇𝐸,𝑖𝐷𝑖𝑗(𝑃𝑀𝐼),𝑘

𝑚

𝑖=1

(16)

𝑟𝑘 =𝜒𝑠 − 𝐵𝑘𝜒𝑚(𝑚𝑜𝑑),𝑘

(17)

Where:

𝜒𝑚(𝑚𝑜𝑑),𝑘 is the air quality impact at the modeled emission rates for all monitored sources at the PMI on the k’th day in the modeling year with measured background values, in μg/m3;

𝑟𝑘 is the compliance ratio of the emissions from monitored sources on the k’th day when the when the air quality impact equals the ambient air quality standard; and



𝐵𝑘 is the background on the k’th day in the modeling year with measured background values, in μg/m3

The above equations are exact if all sources are monitored and are approximate if the impacts from unmonitored sources are small. This is generally true for, 24-hour air quality impacts from the near-ground level emission PM10 releases which drop rapidly with distance from the PMI.

Assuming all the sources’ emissions are increased proportionally, the compliance ratio, 𝑟𝑘 , represents the emission increase relative to emissions that were modeled to equal the standard on the k’th day during the year. For the sources contributing the vast majority to the 24-hour air quality impacts, it is likely that the emissions of all the sources will increase and decrease in proportion. For example, the impacts near each of the borrow area depend almost exclusively on the amount of material added or removed from the borrow area and the travel on the borrow area road, which is proportional to the amount of material added or removed for the same mix of vehicles. Similarly, for landfill operations the amount of travel on the landfill road amount of cover required and travel on the road transporting the cover is proportional to the amount of waste deposited.

Values of 𝑟𝑘 greater than one indicate that the modeled emissions that are monitored result in modeled air quality impacts are less than the standard and emissions would have to increase to reach the standard. Values 𝑟𝑘 less than one indicate that the modeled emissions result in modeled air quality impacts that are greater than the standard and emissions must decrease to reach the standard. If all the values for the year are greater than one it indicates that compliance is expected for the modeled scenario. In this case, the minimum value of the parameter 𝑟𝑘 indicates the day when the smallest increase in modeled emissions, potentially from a different operational scenario, would cause an exceedance of the standard. Similarly, if some values are less than one, it indicates that the facility would not be expected to comply at the modeled emission rate. In this case, the minimum value of the parameter 𝑟𝑘 indicates the day when the greatest reduction from the modeled emissions is required to achieve compliance. Therefore, the District used the day with the minimum 𝑟𝑘 as the basis for the daily monitoring paramters.

Tables A-I-1 through A-I-3 show the maximum modeled air quality impact and the compliance ratio at the PMI for all the days with measured background in 2003 for Runs S33B for BAA, S31SouthEnd for BAB, and S31SouthEnd for the southern landfill property boundary—these three modeled operating scenarios were identified as having the maximum 24-hour air quality impacts. The minimum relative emission increase is shown in bold for each run.



Table IV-1. Compliance Ratio at PMI near BAA—Run S33B.

Date

Average Concentration,

μg/m3

PM10 Background,

μg/m3

Impact + Background,

μg/m3

Relative Emission

Increase to Reach Standard

01/09/2003 37.0935 9.7 46.7935 1.086443717 02/02/2003 (a) 0.01215 32.6 32.61215 1432.098765 02/08/2003 25.13039 13.5 38.63039 1.452424734 02/15/2003 13.60809 10.1 23.70809 2.932079373 02/20/2003 21.58171 13 34.58171 1.714414659 02/26/2003 11.99591 10.3 22.29591 3.309461308 03/04/2003 29.83154 7 36.83154 1.441427429 03/10/2003 2.91997 19.3 22.21997 10.51380665 03/16/2003 (a) 0.00083 13.2 13.20083 44337.3494 03/22/2003 (b) 0.00073 17.7 17.70073 44246.57534 03/28/2003 25.80332 15.2 41.00332 1.34866366 04/03/2003 (b) 0.0008 9.2 9.2008 51000 04/09/2003 21.79862 19.7 41.49862 1.389996247 04/15/2003 27.57521 8.5 36.07521 1.504974939 04/23/2003 14.85556 13.1 27.95556 2.483918479 04/27/2003 (a) 0.00053 13 13.00053 69811.32075 05/09/2003 8.59709 16.8 25.39709 3.861771832 05/15/2003 15.44762 17.7 33.14762 2.090936986 05/21/2003 11.59905 31.3 42.89905 1.612200999 05/27/2003 5.4038 23.5 28.9038 4.903956475 06/02/2003 (b) 0.00001 23.1 23.10001 2690000 06/08/2003 (a) 0.00121 11.6 11.60121 31735.53719 06/14/2003 (b) 0.00002 24.2 24.20002 1290000 06/20/2003 11.3738 17.8 29.1738 2.831067893 06/26/2003 4.05089 28.8 32.85089 5.233417842 07/02/2003 7.95021 30.4 38.35021 2.465343683 07/08/2003 6.08312 26.7 32.78312 3.830271308 07/14/2003 3.42451 29.9 33.32451 5.869452856 07/20/2003 (a) 0.00469 22.1 22.10469 5948.827292 07/26/2003 3.98499 22.6 26.58499 6.875801445 08/01/2003 5.24994 16.2 21.44994 6.438168817 08/07/2003 9.80769 22 31.80769 2.854902633 08/13/2003 15.18358 32.9 48.08358 1.12621661 08/25/2003 6.47684 22.5 28.97684 4.245897691 08/31/2003 (a) 0.00259 26 26.00259 9266.409266 09/06/2003 4.26438 36.8 41.06438 3.095408946 09/12/2003 1.2388 28.8 30.0388 17.11333549 09/18/2003 11.83264 32.1 43.93264 1.512764692 09/24/2003 4.85351 33 37.85351 3.502619754 10/06/2003 8.47858 35.1 43.57858 1.757369748 10/12/2003 (a) 0.013 26.8 26.813 1784.615385 10/18/2003 13.34552 30.5 43.84552 1.461164496 10/24/2003 19.69844 36.9 56.59844 0.665027281 10/30/2003 1.1476 17 18.1476 28.75566399 11/05/2003 32.53143 16.5 49.03143 1.029773361 11/11/2003 22.58325 21.6 44.18325 1.257569216 11/17/2003 43.82163 9.6 53.42163 0.921919153 11/23/2003 (a) 0.00181 14.7 14.70181 19502.76243 11/29/2003 18.54594 16.3 34.84594 1.817109297 12/11/2003 37.48206 11.5 48.98206 1.027158059 12/17/2003 42.54346 16.9 59.44346 0.778027927 aSundays. The applicant did not model emissions on Sunday for landfill operations except flares and wind erosion. bAir quality impacts were not calculated for most daytime hours because of missing meteorological data. Air quality impacts for daytime emissions (most landfilling operations) are underestimated.



Table IV-2. Compliance Ratio at PMI near BAB—Run S31SouthEnd.

Date


μg/m3

PM10 Background,

μg/m3


μg/m3

Relative Emission


01/09/2003 27.05977 9.7 36.75977 1.489295733 02/02/2003 (a) 0.07531 32.6 32.67531 231.0450139 02/08/2003 8.93959 13.5 22.43959 4.082961299 02/15/2003 8.45979 10.1 18.55979 4.716429131 02/20/2003 16.90455 13 29.90455 2.188759831 02/26/2003 9.61322 10.3 19.91322 4.129729685 03/04/2003 37.80325 7 44.80325 1.137468339 03/10/2003 1.96239 19.3 21.26239 15.64418897 03/16/2003 (a) 0.0557 13.2 13.2557 660.6822262 03/22/2003 (b) 0.06725 17.7 17.76725 480.2973978 03/28/2003 19.56382 15.2 34.76382 1.778793712 04/03/2003 (b) 0.03911 9.2 9.23911 1043.211455 04/09/2003 6.69116 19.7 26.39116 4.528362795 04/15/2003 12.00312 8.5 20.50312 3.4574344 04/23/2003 10.15516 13.1 23.25516 3.633620741 04/27/2003 (a) 0.04289 13 13.04289 862.6719515 05/09/2003 6.41591 16.8 23.21591 5.174636178 05/15/2003 6.23544 17.7 23.93544 5.180067485 05/21/2003 5.85746 31.3 37.15746 3.192510064 05/27/2003 3.81977 23.5 27.31977 6.937590483 06/02/2003 (b) 0.00022 23.1 23.10022 122272.7273 06/08/2003 (a) 0.03867 11.6 11.63867 993.0178433 06/14/2003 (b) 0.00212 24.2 24.20212 12169.81132 06/20/2003 9.84107 17.8 27.64107 3.272001927 06/26/2003 3.86798 28.8 32.66798 5.480897006 07/02/2003 6.42877 30.4 36.82877 3.048794715 07/08/2003 5.36755 26.7 32.06755 4.340900411 07/14/2003 3.19878 29.9 33.09878 6.28364564 07/20/2003 (a) 0.09018 22.1 22.19018 309.3812375 07/26/2003 3.58769 22.6 26.18769 7.637226182 08/01/2003 4.56226 16.2 20.76226 7.408608891 08/07/2003 4.54937 22 26.54937 6.154698343 08/13/2003 6.06383 32.9 38.96383 2.819999901 08/25/2003 4.63392 22.5 27.13392 5.93450038 08/31/2003 (a) 0.04736 26 26.04736 506.7567568 09/06/2003 3.73922 36.8 40.53922 3.530147999 09/12/2003 0.836 28.8 29.636 25.35885167 09/18/2003 7.46671 32.1 39.56671 2.397307516 09/24/2003 4.19509 33 37.19509 4.052356445 10/06/2003 8.18034 35.1 43.28034 1.821440185 10/12/2003 (a) 0.19289 26.8 26.99289 120.2758049 10/18/2003 7.03178 30.5 37.53178 2.773124301 10/24/2003 12.92119 36.9 49.82119 1.013838509 10/30/2003 0.76929 17 17.76929 42.89669695 11/05/2003 17.47925 16.5 33.97925 1.916558205 11/11/2003 15.8822 21.6 37.4822 1.788165368 11/17/2003 22.61043 9.6 32.21043 1.78678601 11/23/2003 (a) 0.03755 14.7 14.73755 940.0798935 11/29/2003 12.35893 16.3 28.65893 2.726773272 12/11/2003 29.45332 11.5 40.95332 1.307153149 12/17/2003 31.21828 16.9 48.11828 1.060276223 aSundays. The applicant did not model emissions on Sunday for landfill operations except flares and wind erosion. bAir quality impacts were not calculated for most daytime hours because of missing meteorological data. Air quality impacts for daytime emissions (most landfilling operations) are underestimated.



Table IV-3. Compliance Ratio at South End of Landfill—Run S31SouthEnd.

Date


μg/m3

PM10 Background,

μg/m3


μg/m3

Relative Emission


01/09/2003 29.99459 9.7 39.69459 1.3435756 02/02/2003 (a) 0.16581 32.6 32.76581 104.93939 02/08/2003 17.48152 13.5 30.98152 2.0879191 02/15/2003 19.60393 10.1 29.70393 2.0353062 02/20/2003 35.82201 13 48.82201 1.0328845 02/26/2003 22.61485 10.3 32.91485 1.7554837 03/04/2003 96.54471 7 103.5447 0.4453895 03/10/2003 2.24395 19.3 21.54395 13.681232 03/16/2003 (a) 0.13286 13.2 13.33286 276.98329 03/22/2003 (b) 0.27535 17.7 17.97535 117.30525 03/28/2003 49.08789 15.2 64.28789 0.7089325 04/03/2003 (b) 0.13948 9.2 9.33948 292.51506 04/09/2003 11.32969 19.7 31.02969 2.6743891 04/15/2003 29.39674 8.5 37.89674 1.4117212 04/23/2003 25.71139 13.1 38.81139 1.4351616 04/27/2003 (a) 0.20837 13 13.20837 177.56875 05/09/2003 13.75258 16.8 30.55258 2.4140925 05/15/2003 13.00197 17.7 30.70197 2.4842389 05/21/2003 10.63192 31.3 41.93192 1.7588545 05/27/2003 6.87754 23.5 30.37754 3.8531219 06/02/2003 (b) 0.24891 23.1 23.34891 108.07119 06/08/2003 (a) 0.45603 11.6 12.05603 84.204987 06/14/2003 (b) 0.0751 24.2 24.2751 343.54194 06/20/2003 19.94792 17.8 37.74792 1.6142034 06/26/2003 7.72848 28.8 36.52848 2.7431008 07/02/2003 15.79424 30.4 46.19424 1.2409587 07/08/2003 10.66259 26.7 37.36259 2.1852102 07/14/2003 6.01022 29.9 35.91022 3.3443035 07/20/2003 (a) 0.41354 22.1 22.51354 67.466267 07/26/2003 7.18778 22.6 29.78778 3.8120254 08/01/2003 10.49377 16.2 26.69377 3.2209587 08/07/2003 8.99209 22 30.99209 3.1138478 08/13/2003 12.02366 32.9 44.92366 1.4221959 08/25/2003 8.79345 22.5 31.29345 3.1273277 08/31/2003 (a) 0.29725 26 26.29725 80.740118 09/06/2003 7.97932 36.8 44.77932 1.6542763 09/12/2003 1.23223 28.8 30.03223 17.20458 09/18/2003 16.67803 32.1 48.77803 1.0732682 09/24/2003 8.01209 33 41.01209 2.1217934 10/06/2003 21.70142 35.1 56.80142 0.686591 10/12/2003 (a) 0.39681 26.8 27.19681 58.466268 10/18/2003 15.04199 30.5 45.54199 1.296371 10/24/2003 22.40959 36.9 59.30959 0.5845712 10/30/2003 1.56055 17 18.56055 21.146391 11/05/2003 25.88767 16.5 42.38767 1.2940523 11/11/2003 36.1978 21.6 57.7978 0.7845781 11/17/2003 36.1235 9.6 45.7235 1.1183855 11/23/2003 (a) 0.32149 14.7 15.02149 109.80124 11/29/2003 17.37974 16.3 33.67974 1.9390394 12/11/2003 41.74637 11.5 53.24637 0.9222359 12/17/2003 45.69245 16.9 62.59245 0.7244085 aSundays. The applicant did not model emissions on Sunday for landfill operations except flares and wind erosion. bAir quality impacts were not calculated for most daytime hours because of missing meteorological data. Air quality impacts for daytime emissions (most landfilling operations) are underestimated.



V. AIR QUALITY IMPACT FACTORS FOR MONITORING

ROAD AIR QUALITY IMPACT FACTORS

Calculation Procedure For roads the monitoring parameter chosen was a “vehicle factor” (see below), which is based on the number and average characteristics of the vehicles traveling a given road. The air quality impact factors were calculated by the following procedure.

The general emission factors for unpaved and unpaved roads are:

𝐸(𝑃𝑀10)𝑝𝑎𝑣 = 𝑘𝑝𝑎𝑣𝑁𝐿 �𝑠𝐿2�0.65

�𝑆

32.5� �𝑊3�1.5

�1 − 𝜂𝑝𝑎𝑣� (1)

And

𝐸(𝑃𝑀10)𝑢𝑛𝑝 = 5.9𝑘𝑢𝑛𝑝𝑁𝐿 �𝑠

12� �

𝑆30� �𝑊3�0.7

�𝑤4�0.5�

365 − 𝑝365

� �1 − 𝜂𝑢𝑛𝑝� (2)

𝐸(𝑃𝑀10)𝑝𝑎𝑣 and 𝐸(𝑃𝑀10)𝑢𝑛𝑝 are the fugitive dust emissions for the applicable time period (annual, daily, hourly) for paved roads and unpaved road hourly or daily emissions, respectively, in pounds;

𝑘𝑝𝑎𝑣 and 𝑘𝑢𝑛𝑝 are particle size multipliers for paved and unpaved roads, respectively (see Table IV-1 in the engineering evaluation);

𝑁 is the number of vehicles traveling the road in the given time period;

𝐿 is the length of the road in, miles;

𝑠𝐿 is road silt loading, in g/m2;

𝑆 is the mean vehicle speed of all the vehicles traveling the road in the given time period;

𝑊 is the mean vehicle weight of all the vehicles traveling the road in the given time period;

𝑤 is the mean number of wheels of all the vehicles traveling the road in the given time period;

𝑠 is the silt content of the road surface, in %;



𝑝 is the number of days per year with more than 0.01 inch of precipitation, which is assumed to zero for calculating daily emissions and be 40 for San Diego for calculation of annual emissions except for heavily watered areas, in which case, 𝑝 is assumed to be zero for annual emissions.

𝜂𝑝𝑎𝑣 and 𝜂𝑢𝑛𝑝 are control efficiencies for paved and unpaved roads, respectively.

The above paved-road emission factor can be expressed as:

𝐸(𝑃𝑀)𝑝𝑎𝑣 = 2.2871 × 10−8𝐹𝑣,𝑝𝑎𝑣𝐹𝑟,𝑝𝑎𝑣 (3)

With:

𝐹𝑣,𝑝𝑎𝑣 = 𝑁(𝑊)1.5 (4)

And with:

𝐹𝑟,𝑝𝑎𝑣 = 𝐿(𝑠𝐿)0.65(𝑆)�1 − 𝜂𝑝𝑎𝑣� (5)

Similarly, the unpaved-road emission factor can be expressed as:

𝐸(𝑃𝑀)𝑢𝑛𝑝 = 5.1788 × 10−7𝐹𝑣,𝑢𝑛𝑝𝐹𝑟,𝑢𝑛𝑝 (6)

With:

𝐹𝑣,𝑢𝑛𝑝 = 𝑁(𝑊)0.7(𝑤)0.5 (7)

And with:

𝐹𝑟,𝑢𝑛𝑝 = 𝐿(𝑠)(𝑆) �365 − 𝑝

365� �1 − 𝜂𝑢𝑛𝑝� (8)

Where:

𝐹𝑣,𝑝𝑎𝑣 is the paved-road vehicle factor that is only a function of vehicle characteristics, in ton1.5

𝐹𝑟,𝑝𝑎𝑣 is the paved-road road factor that is only a function of road characteristics, in miles-(g/m2)0.65-mph



𝐹𝑣,𝑢𝑛𝑝 is the unpaved-road vehicle factor that is only a function of vehicle characteristics, in ton0.7

𝐹𝑟,𝑢𝑛𝑝 is the unpaved-road road factor that is only a function of road characteristics, in miles-mph

The air quality impact factors for paved and unpaved roads using the vehicle factor as the monitoring parameter is given by:

𝐼𝑝,𝑝𝑎𝑣,𝑖𝑗 = 2.2871 × 10−8𝐹𝑟,𝑝𝑎𝑣,𝑖𝐷𝑝𝑎𝑣,𝑖𝑗 (9)

And:

𝐼𝑝,𝑢𝑛𝑝,𝑖𝑗 = 5.1788 × 10−7𝐹𝑟,𝑢𝑛𝑝,𝑖𝐷𝑢𝑛𝑝,𝑖𝑗 (10)

Where:

𝐼𝑝,𝑝𝑎𝑣,𝑖𝑗 and 𝐼𝑝,𝑢𝑛𝑝,𝑖𝑗 are the average air quality impact factors for the i’th paved and unpaved road at the j’th receptor for the specified time period, respectively, in (μg/m3)/(vehicle factor);

𝐹𝑟,𝑝𝑎𝑣,𝑖 and 𝐹𝑟,𝑢𝑛𝑝,𝑖 are the road emission factors for the i’th paved and unpaved road for the specified time period, respectively, in in miles-(g/m2)0.65-mph and miles-mph, respectively;

𝐷𝑝𝑎𝑣,𝑖𝑗 and 𝐷𝑢𝑛𝑝,𝑖𝑗 are the average atmospheric dispersion factors for the i’th paved and unpaved road emissions at the j’th receptor, respectively, in (μg/m3)/(lb).

MATERIAL HANDLING AIR QUALITY IMPACT FACTORS

Calculation Procedure For material handling the monitoring parameter is the weight of material handled and air quality impact factors simply calculated by multiplying the material handling emission factor time the applicable atmospheric dispersion factor:

𝐼𝑝,𝑚𝑜𝑝,𝑖𝑗 = 𝐹𝑚𝑜𝑝,𝑖𝐷𝑚𝑜𝑝,𝑖𝑗 (11)

𝐼𝑝,𝑚𝑜𝑝,𝑖𝑗 is the average air quality impact factor for the i’th material handling operation at the j’th receptor for the specified time period, in (μg/m3)/ton; and

𝐹𝑚𝑜𝑝,𝑖 is the material handling emission factor for the i’th material handling operation for the specified time period, in lb/ton; and



𝐷𝑚𝑜𝑝,𝑖𝑗 is the average atmospheric dispersion factor for the i’th material handling operation emissions at the j’th receptor for the specified time period, in (μg/m3)/lb.

VI. ANNUAL AIR QUALITY IMPACT FACTORS

ANNUAL ROAD AIR QUALITY IMPACT FACTORS FOR MONITORING Table VI-2 shows the air quality impact factors calculated from the modeling results for air quality impacts from haul vehicle travel on roads. Table VI-3 shows the air quality impact factors used for monitoring the air quality impacts from haul vehicle impacts for various operational states of the landfill. The Y in the tables below and in subsequent sections below refers to the NAD27 UTM Northing coordinate, in meters, of the working face. Y1, Y17 and Y22 refer to the NAD27 UTM Northing coordinates of the working face assumed by the applicant for annual modeling for Years 1, 17 and 22, respectively, and are listed in Table VI-1.

Table VI-1. Modeled Working Face NAD27 UTMa Coordinates

UTM Easting Coordinate (X) UTM Northing Coordinate (Y)

Y1 489943.9 3689281.2 Y17 490275 3688715 Y22 489807 3689214.9 aNAD27 UTM stands for North American Datum of 1927 Universal Transverse Mercator. San Diego is in Zone 11, North.

Road grading emissions are not included and in the air quality impact factor calculations. Their impacts are included in unmonitored air quality impacts. Also, unmonitored is travel of vehicles on haul roads delivering fill material are not included although the fill operations themselves are monitored as annual material handling air quality impacts.



Table VI-2. Annual Calculated Road Air Quality Impact Factors for Vehicle Factor Monitoring Parameter, (μg/m3)/ton0.7

Model Year -2 1 17 17 22 22

Model Run As Adjusted or Modified by the District

S25 Annualized S26 S29

S29 SouthEnd S32

S32 Working Face Above

900 Feet Haul Road

Main Entrance (paved) 2.51598E-08 3.591E-08 3.24E-08 3.2375E-08 3.50164E-08 3.50164E-08 Internal Wastea 1.92916E-07 3.831E-07 6.51E-07 6.5026E-07 3.87852E-07 6.87493E-07 Borrow Area A 2.40528E-07

3.82294E-07 7.22069E-07

Borrow Area B 3.13321E-07 9.586E-08 6.86E-08 5.3319E-08 4.03159E-07 Cover and material handling

8.427E-07

Fill 9.0824E-08 3.373E-08

aIn modeling Year -2 this is a material haul road since no waste is being received.



Table VI-3. Annual Road Air Quality Impact Factors for Monitoring

Haul Road Operational Status Vehicle Impact Factor,

(μg/m3)/ton0.7 Basis Main Entrance Prior to initial receipt of waste 2.51598E-08 Yr -2 S25 Main Entrance After initial receipt of waste 3.59088E-08 Yr 1 S26. Maximum of Yrs 1, 17, and 22. Internal material Prior to initial receipt of waste 1.92916E-07 Yr -2 S25. Not applicable other years. Internal waste Ya ≤ Y17

b 6.50967E-07 Yr 17 S29. Maximum of Yrs 1, 17, and 22. Internal waste Y > Y17 6.87493E-07 S32 working face at 900 feet surrogate.

Cover and material All times 8.42724E-07

Year 1 S26. Length assume same in all years. Year 1 is likely worst case since in other years expected to be located farther south.

Borrow Area A Prior to initial receipt of waste 2.40528E-07 Yr -2 S25

Borrow Area A After initial receipt of waste and Y ≤ Y22

b 3.82294E-07 Yr 22 S32

Borrow Area A After initial receipt of waste and Y > Y22 and Y ≤ Y17 7.22069E-07 S32 working face at 900 feet surrogate.

Borrow Area A After initial receipt of waste Y > Y17 7.22069E-07 S32 working face at 900 feet surrogate.

Borrow Area A After closure of the landfill to receipt of solid waste 7.22069E-07 S32 working face at 900 feet surrogate.

Borrow Area B Prior to initial receipt of waste 3.13321E-07 Yr 22 S32

Borrow Area B After initial receipt of waste and Y ≤ Y17 4.03159E-07 Yr 22 S32. Maximum of Yr 1, 17, and 22.

Borrow Area B After initial receipt of waste and Y > Y17 9.58565E-08

Yr 1 S26. BAB road is approximately at north-south location of Y17 in Year 1. Assumes little additional impact for road length north of Y17.

Borrow Area B After closure of the landfill to receipt of solid waste 4.03159E-07 Yr 22 S32. Maximum of Yr 1, 17, and 22.

aY is the NAD27 UTM Northing coordinate of the working face. bY17 and Y22 are the modeled NAD27 UTM Northing coordinate of the working face in years 17 and 22, respectively.



ANNUAL MATERIAL HANDLING OPERATION AIR QUALITY IMPACT FACTORS FOR MONITORING Table VI-4 shows the air quality impact factors calculated from the modeling for material handling operations at the landfill. The PMI for all the annual impacts modeled was on or near the northern property border closest to the ancillary facility’s area. Blasting air quality impacts were not quantified on a per ton basis and they are unmonitored along with wind erosion and road grading emissions. They are included as unmonitored air quality impacts at their estimated maximum potential to emit as part of the monitoring calculations.

Table VI-5 shows the air quality impact factors derived from the calculated values used for monitoring the air quality impacts for various operational states of the landfill. Besides the area of operation, the criteria used to determine the landfill states were the amount of material excavated from the landfill footprint in a month, cumulative excavation in the landfill footprint, and location of the working face. It was assumed that, if more than 50,000 tons of excavation is occurred in a month and the landfill was receiving waste, that cover requirements for the waste received would be met from the landfill footprint excavation. The total cumulative weight of landfill footprint excavation was used to separate Phase I and Phase II of the construction. Phase I was assumed to end after 6,845,000 tons of excavation.



Table VI-4. Material Handling Air Quality Impact Factors Calculated from Modeling Results, (μg/m3)/ton

Description -2 1 17 17 South End 22 22



S29 SouthEnd S32

S32 Working Face Above 900 Feet

Borrow Area A operations 2.51598E-08 3.591E-08 3.24E-08 3.2375E-08 3.50164E-08 3.50164E-08 Borrow Area B operations, soil

6.388E-09 4.09E-08 3.9118E-08 4.82543E-08

Borrow Area A operations, rock 6.65413E-09 6.416E-09 Landfill operations, waste deposition

1.505E-07 1.89E-08 1.3234E-08 1.08819E-07 1.32343E-08

Landfill operations, cover application

2.598E-07 4.81E-08 3.377E-08 2.7767E-07 3.37695E-08 Rock crushing 9.24688E-08 2.546E-08 8.7E-10 2.6457E-09

Landfill footprint excavation 2.53733E-07 7.222E-08 Clay liner installation 1.35867E-06 2.014E-07 Fill operations 3.51871E-07 8.178E-08 Loading rock in landfill footprint 2.77253E-08 6.295E-09 Drilling holes for blasting 2.48301E-09 6.838E-11

1.5409E-13 Blasting N/A N/A

N/A

Storing of material in landfill footprint storage pilesa (the χ/Q for landfill foot print excavation was used as a surrogate since this operation was not modeled by the applicant)

2.459E-08



Table VI-5. Annual Material Handling Operation Air Quality Impact Factors for Monitoring Annual Air Quality Impacts

Operation Type or Area State

Air Quality Impact Factor,

(μg/m3)/ton Basis

Borrow Area A Prior to initial receipt of solid waste 5.98786E-09

Year -2 S25, annualized daily emissions.

Borrow Area A After initial receipt of solid waste, more than 50,000 tons of landfill footprint excavation per month, and no borrow area excavation. 5.98786E-09

Year -2 S25. Expected reasonable worst case unloading.

Borrow Area A After initial receipt of solid waste, less than or equal to 50,000 tons of landfill footprint excavation per month, and no borrow area excavation.

6.57546E-08

Year 22 S32. Expected reasonable worst case excavation and/or loading.

Borrow Area A After initial receipt of solid waste, less than or equal to 50,000 tons of landfill footprint excavation per month, and borrow area excavation.

6.57546E-08 Year 22 S32. Excavation in Year 22.

Borrow Area B Prior to initial receipt of solid waste 6.65413E-09 Year 1 S26. Expected reasonable worst case unloading (BAB rock).

Borrow Area B After initial receipt of solid waste, more than 50,000 tons of landfill footprint excavation per month, and no borrow area excavation. 6.41624E-09

Year 1 S26. Expected reasonable worst case unloading evaluated (BAB rock).

Borrow Area B After initial receipt of solid waste, less than or equal to 50,000 tons of landfill footprint excavation per month, and no borrow Area excavation. 4.82543E-08

Year 22 S32. Worst case excavation and loading.

Borrow Area B After initial receipt of solid waste, less than or equal to 50,000 tons of landfill footprint excavation per month, and borrow area excavation. 4.82543E-08 Year 22 S32. Excavation in Year 22.

Landfill, MSW Y ≤ Y17 1.50484E-07 Year 1 S26. Expected reasonable worst case.

Landfill s, MSW Y > Y17 1.88545E-08 Year 17 S29. Expected reasonable worst case.

Landfill, cover Y ≤ Y17 and no borrow area excavation has occurred 2.59849E-07 Year 1 S26. Expected reasonable worst case.

Landfill, cover Y > Y17 4.81104E-08 Year 17 S29. Expected reasonable worst case.

Landfill, cover Y ≤ Y17 and borrow area excavation has occurred 2.7767E-07 Year 22 S32. Expected reasonable worst case.



Landfill excavation, soil Cumulative landfill footprint excavation less than or equal to 6,845,000 tons 2.53733E-07

Year -2 S25. Expected reasonable worst case.

Landfill excavation, soil Cumulative landfill footprint excavation more than 6,845,000 tons 7.2223E-08

Year 1 S26. Expected reasonable worst case.

Landfill excavation, rock Cumulative landfill footprint excavation less than or equal to 6,845,000 tons 2.77253E-08


Landfill excavation, rock Cumulative landfill footprint excavation more than 6,845,000 tons 6.29469E-09


Liner insallation Cumulative landfill footprint excavation less than or equal to 6,845,000 tons 1.35867E-06 Year -2 S25. Expected reasonable worst case.

Liner insallation Cumulative landfill footprint excavation more than 6,845,000 tons 2.01419E-07 Year 1 S26. Expected reasonable worst case.

Fill Cumulative landfill footprint excavation less than or equal to 6,845,000 tons 3.51871E-07 Year -2 S25. Expected reasonable worst case.

Fill Cumulative landfill footprint excavation more than 6,845,000 tons 8.17781E-08 Year 1 S26. Expected reasonable worst case.

Final cover installation North of Y17 1.35867E-06

Year 1 S26. Clay liner installation used as conservatively high estimate.

Final cover installation South of Y17 2.01419E-07

Year 1 S26. Clay liner installation used as conservatively high estimate.

Rock crushing in the landfill footprint Cumulative landfill footprint excavation less than or equal to 6,845,000 tons 9.24688E-08


Rock crushing in the landfill footprint Cumulative landfill footprint excavation more than 6,845,000 tons 2.54638E-08


Rock crushing in BAB All times 8.69733E-10

Yr 17 S29. Expected reasonable worst case.

Intermediate storage pile All times 2.45923E-08




ANNUAL UNMONITORED AIR QUALITY IMPACTS Table VI-6 shows the unmonitored annual air quality impacts. The impacts in Table VI-6 are based on the estimated maximum potential to emit of the sources that are unmonitored. The unmonitored sources include road grading emissions, travel on fill haul roads (Years -2 and 1), drilling, blasting, and wind erosion. Table VI-7 shows the unmonitored annual air quality impacts used in the monitoring. The end of the Phase II construction period is assumed to be when a cumulative total of 13,690,000 tons have been excavated from the landfill footprint.

Table VI-6. Calculated Unmonitored Annual Air Quality Impacts, μg/m3

Year -2 1 17 17 South End 22 Model Run As Adjusted or Modified by the District

S25 Annualized S26 S29 S29 SouthEnd S32

Source All unmonitored 0.142091335 0.0677602 9.72E-05 0.000154038 0.000810015 Wind erosion 0.007805597 0.0038559

0.00015397 0.000810015

Table VI-7. Unmonitored Annual Air Quality Impacts for Monitoring

Operational State Impact, μg/m3 Basis

Cumulative landfill footprint excavation less than or equal to 6,845,000 tons 0.1421 S25 Annualized Cumulative landfill footprint excavation more than 6,845,000 tons but less than or equal to 13,690,000 tons 0.0678 S26 Cumulative landfill footprint excavation more than 13,690,000 tons 0.0008 S32 Final cover installation after closure of the landfill to receipt of solid waste 0.0118

Sum of wind erosion for S25 Annualized, S1, and S29 SouthEnda

aAreas added because entire landfill area will potentially be subject to wind erosion during final cover installation. This likely overestimates impact because of some overlap in areas and the higher elevation of the wind erosion areas compared to Year -2 and Year 1.



VII. DAILY AIR QUALITY IMPACT FACTORS

Because the 24-hour PM10 impacts are extremely localized, impact factors and monitoring on a daily basis is only proposed for activities in the immediate vicinity of the PMI. These include transport of and loading and unloading materials in the borrow areas or near the southern property line (within about 400 feet) in the landfill footprint. The impacts from the entire length of all roads on which material is transported to or from the main impact areas are accounted for in the impact factors although nearly all the impact results from operations near the PMI. Rock crushing in Borrow Area B is not monitored but included in the unmonitored impacts. The southernmost rock crushing location is limited by the proposed A/C permit conditions to a location consistent with the modeling. The PMIs are located on the southern property line for operations in Borrow Area B and in the southern area of the landfill and are located on the western property line for Borrow Area A.

DAILY ROAD AIR QUALITY IMPACT FACTORS FOR MONITORING The 24-hour air quality impact factors for monitoring of vehicle travel on haul roads are shown in Table VII-1. The impact factors were calculated from the modeling results, as adjusted or modified by the District, as listed as the basis for the factors. Surrogates are used when the District believed the applicant’s modeled scenarios were not sufficient to address the air quality impacts.



VII-1. Daily Road Air Quality Impact Factors for Monitoring

Haul Road and Monitored Area State

Impact Factor, (μg/m3)/ton0.7 Basis

Borrow Area A (BAA) Unloading landfill soil 8.67779E-04

Year -2 S25 with S33BNewGrid surrogatea.

Borrow Area A Loading stored landfill soil 8.67779E-04 Year 22 S33BNewGridb.

Borrow Area A Excavating and loading borrow area soil 1.24486E-03 Year 22 S33BNewGrid.

Borrow Area B (BAB) Unloading landfill soil 2.74280E-04

Year 1 S28 with S31 SouthEnd surrogatec

Borrow Area B Loading stored landfill soil 2.74280E-04 Year 1 S28 with S31 SouthEnd surrogated

Borrow Area B Excavating and loading borrow area soil 3.10588E-04 Year 17 S31 SouthEnd

Waste Haul Road travel

Working face south of NAD27 Northing coordinate 3688155e 1.34425E-03 Year 17 S31 SouthEnd

BAA Road, BAB Road, cover and material handling roads in landfill footprint


aχ/Q surrogate for unloading with emission factors adjusted for unloading. bEmission factors adjusted for loading. cχ/Q surrogate for unloading and BAB end of road. dχ/Q surrogate for unloading and BAB end of road and emission factors adjusted for loading. eWithin about 400 feet of the southern property boundary.

DAILY MATERIAL HANDLING OPERATION AIR QUALITY IMPACT FACTORS FOR MONITORING Table VII-2 shows the daily material handling air quality impact factors used for monitoring. They are based 24-hour modeling results, as adjusted or modified by the District, as shown in the right-most column.



VII-2. Daily Material Handling Air Quality Impact Factors for Monitoring

Operation and Operation Location State

Impact Factor, (μg/m3)/ton0.7 Basis

Borrow Area A (BAA) Unloading landfill soil 6.31461E-04

Year -2 S25 with S33BNewGrid surrogatea.

Borrow Area A Loading stored landfill soil 1.32933E-03 Year 22 S33BNewGridb.

Borrow Area A Excavating and loading borrow area soil 4.07564E-03 Year 22 S33BNewGrid.

Borrow Area B (BAB) Unloading landfill soil 3.71478E-04

Year 1 S28 with S31 SouthEnd surrogatec

Borrow Area B Loading stored landfill soil 6.02424E-04 Year 1 S28 with S31 SouthEnd surrogated

Borrow Area B Excavating and loading borrow area soil 2.93210E-03 Year 17 S31 SouthEnd

Waste deposition operations, landfill footprint


Waste cover operations, landfill footprint


aχ/Q surrogate with emission factor adjusted for unloading. bEmission factors adjusted for loading. cχ/Q surrogate for unloading. dχ/Q surrogate for unloading with emission factors adjusted for loading. eWithin about 400 feet of the southern property boundary.

DAILY UNMONITORED AIR QUALITY IMPACTS AND BACKGROUND FOR MONITORING The values for the unmonitored air quality impact factors on a daily basis, applicable background concentrations, and their totals are shown in Table VII-3. The total value in this table is added to the air quality impact calculated from the air quality impact factors and the monitored parameters to determine compliance with the permit conditions on a daily basis. The unmonitored factors are based on the estimated maximum potential to emit for the unmonitored sources.



Table VII-3. Daily Unmonitored Air Quality Impacts

Monitored Area State

Unmonitored Impact, μg/m3

Background, μg/m3

Total, μg/m3 Basis

BAA Cumulative landfill footprint excavation ≤ 6,845,000 tons 3.39 36.9 40.29

All externala source impacts Year -2 S25 at S33B PMIb 10/24/03.

BAA

Cumulative landfill footprint excavation > 6,845,000 tons but ≤ 13,690,000 tons 2.59 36.9 39.49

All externala sources Year 1 S28 at S33B PMIb 10/24/03.

BAA Cumulative landfill footprint excavation > 13,690,000 tons 0.80 36.9 37.70 Year 22 S33BNewGridb

BAA After closure of the landfill to receipt of solid waste 0.80 36.9 37.70 Year 22 S33BNewGridc.

BAB Cumulative landfill footprint excavation ≤ 6,845,000 tons 0.40 36.9 37.30

All external sources for Year -2, S25 at Year 1 S28 PMI.

BAB

Cumulative landfill footprint excavation > 6,845,000 tons but ≤ 13,690,000 tons 0.55 36.9 37.45

All external sources for Year 1 S28 PMI 10/24/03, except BAA not modeled--expected to be small.

BAB Cumulative landfill footprint excavation > 13,690,000 tons 1.71 36.9 38.61

All externala sources and rock crushingd in BAB, Year 17 S31SouthEnd PMI 10/24/03.

BAB After closure of the landfill to receipt of solid waste 1.71 36.9 38.61

All externala sources and rock crushingd in BAB, Year 17 S31SouthEnd PMI 10/24/03.

Landfill Less than about 400 feet from the southern border 0.23 7 7.23

Based on other sources S31S.End S31 PMI 03/04/03.

aExternal sources are all sources not in monitored area except the borrow area road. bS33B PMI is surrogate since the worst-case scenario was not modeled in Year -2. cFlare impact difference between modeled and JTD location assumed not significant. dSurrogate χ/Q for 10/24/03 for rock crushing from Year 17 S31 in BAB.



VIII. ANNUAL MONITORING EMISSION FACTORS

EMISSION FACTOR CALCULATION PROCEDURE For monitoring road emissions, the road vehicle emission factor is given by:

𝐸𝐹𝑣,𝑝𝑎𝑣,𝑖 = 2.2871 × 10−8𝐹𝑟,𝑝𝑎𝑣,𝑖 (1)

And:

𝐸𝐹𝑣,𝑢𝑛𝑝,𝑖 = 5.1788 × 10−7𝐹𝑟,𝑢𝑛𝑝,𝑖 (2)

Where:

𝐸𝐹𝑣,𝑝𝑎𝑣,𝑖 and 𝐸𝐹𝑣,𝑢𝑛𝑝,𝑖 are the emission factors for the i’th paved or unpaved road, respectively, in lb/ton0.7; and

𝐹𝑟,𝑝𝑎𝑣,𝑖 and 𝐹𝑟,𝑢𝑛𝑝,𝑖 are the road emission factors for the i’th paved or unpaved road for the specified time period, respectively, in in miles-(g/m2)0.65-mph and miles-mph, respectively;

For monitoring material handling emissions, the emission factor is the District emission factor expressed in lb/ton.

ANNUAL ROAD EMISSION FACTORS FOR MONITORING Table VIII-1 shows the emission factors calculated from the modeling results for emissions from haul vehicle travel on roads. Table VIII-2 shows the emission factors used for monitoring the emissions from haul vehicles for various operational states of the landfill. The Y in the tables below and in subsequent sections below refers to the NAD27 UTM Northing coordinate, in meters, of the working face. Y1, Y17 and Y22 refer to the NAD27 UTM Northing coordinates of the working face assumed by the applicant for annual modeling for Years 1, 17, and 22, respectively, and are listed in Table VI-1.

Road grading emissions are not included and in the emission factor calculations. Their emissions are included in unmonitored emissions. Also, unmonitored travel of vehicles on haul roads delivering fill material is not included, although the fill operations themselves are monitored as annual material handling emissions.



Table VIII-1. Annual Calculated Road Emission Factors for Vehicle Factor Monitoring Parameter, lb/ton0.7

Model Year -2 1 17 17 22 22



S29 SouthEnd S32

S32 Working Face Above

900 Feet Haul Road

Main Entrance (paved) 6.99702E-04 6.99702E-04 6.99702E-04 6.99702E-04 6.99702E-04 6.99702E-04 Internal Wastea 4.23533E-03 7.63376E-03 3.06889E-02 3.05924E-02 6.09916E-03 3.52334E-02 Borrow Area A 2.15806E-02

2.16240E-02 5.60098E-02

Borrow Area B 4.00696E-02 2.08066E-02 1.48063E-02 1.28153E-02 3.31407E-02 Cover and material handling

1.50690E-02

Fill 3.21606E-03 4.82410E-03

aIn modeling Year -2 this is a material haul road since no waste is being received.



Table VIII-2. Annual Road Emission Factors for Monitoring

Haul Road Operational Status Vehicle Emission Factor, lb/ton0.7 Basis

Main Entrance Prior to initial receipt of waste 6.99702E-04 Year -2 S25. Main Entrance After initial receipt of waste 6.99702E-04 Year 1 S26. Constant length—emission factor does not change. Internal material Prior to initial receipt of waste 4.23533E-03 Year -2 S25. Internal waste Ya ≤ Y17

b 3.06889E-02 Year 17 S29. Maximum of Years 1, 17, and 22. Internal waste Y > Y17 3.52334E-02 Based on S32 Maximum Elevation Surrogate Cover and material All times 1.50690E-02 Year 1 S26. Length assumed same in all years. Borrow Area A Prior to initial receipt of waste 2.15806E-02 Year -2 S25 Borrow Area A After initial receipt of waste and Y ≤ Y22

b 2.16240E-02 Year 22 S32

Borrow Area A After initial receipt of waste and Y > Y22 and Y ≤ Y17 5.60098E-02 S32 working face at 900 feet surrogate.

Borrow Area A After initial receipt of waste Y > Y17 5.60098E-02 S32 working face at 900 feet surrogate.

Borrow Area A After closure of the landfill to receipt of solid waste 5.60098E-02 S32 working face at 900 feet surrogate.

Borrow Area B Prior to initial receipt of waste 4.00696E-02 Year 22 S32 Borrow Area B After initial receipt of waste and Y ≤ Y17 3.31407E-02 Year 22 S32. Maximum of Year 1, 17, and 22.

Borrow Area B After initial receipt of waste and Y > Y17 3.31407E-02

Year 1 S26. BAB road is approximately at north-south location of Y17 in Year 1 and includes rock road to about center of landfill. Assume length is sufficient to reach all areas north of Y17.

Borrow Area B After closure of the landfill to receipt of solid waste 3.31407E-02

Year 1 S26. BAB road is approximately at north-south location of Y17 in Year 1 and includes rock road to about center of landfill. Assume length is sufficient to reach all areas north of Y17.

aY is the NAD27 UTM Northing coordinate of the working face. bY17 and Y22 are the modeled NAD27 UTM Northing coordinate of the working face in years 17 and 22, respectively.



ANNUAL MATERIAL HANDLING OPERATION EMISSION FACTORS FOR MONITORING Table VIII-3 shows the emission factors calculated from the modeling for material handling operations at the landfill. Blasting emissions were not quantified on a per ton basis and they are unmonitored along with wind erosion and road grading emissions. They are included as unmonitored emission at their estimated maximum potential to emit as part of the monitoring calculations.

Table VIII-4 shows the emission factors derived from the calculated values for various operational states of the landfill. Besides the area of operation, the criteria used to determine the landfill states were the amount of material excavated from the landfill footprint in a month, cumulative excavation in the landfill footprint, and location of the working face. It was assumed that, if more than 50,000 tons of excavation occurred in a month and the landfill was receiving waste, that cover requirements for the waste received would be met from the landfill footprint excavation. The total cumulative weight of landfill footprint excavation was used to separate Phase I and Phase II of the construction. Phase I was assumed to end after 6,845,000 tons of excavation.



Table VIII-3. Material Handling Emission Factors Calculated from Modeling Results, lb/ton

Description -2 1 17 17 South End 22 22

Model Run As Adjusted or Modified by the District S25 Annualized S26 S29 S29 SouthEnd S32

S32 Working Face Above 900 Feet

Borrow Area A operations 1.48886E-03 1.48886E-03 9.60955E-03 9.60955E-03 9.60955E-03 9.60955E-03 Borrow Area B operations, soil 1.48886E-03 1.48886E-03 1.17517E-02 1.17517E-02 1.17517E-02 1.17517E-02 Borrow Area A operations, rock 1.48886E-03 4.37131E-04

Landfill operations, waste deposition

2.82744E-03 2.82744E-03 2.82744E-03 2.82744E-03 2.82744E-03 Landfill operations, cover application

4.88228E-03 7.21468E-03 7.21468E-03 7.21468E-03 7.21468E-03

Rock crushing 2.97925E-03 2.97925E-03 5.94125E-03 5.94125E-03 Landfill footprint excavation 9.20485E-03 9.20485E-03

Clay liner installation 2.98812E-02 2.98812E-02 Fill operations 1.02879E-02 1.02879E-02 Loading rock in landfill footprint 8.93279E-04 8.93279E-04 Drilling holes for blasting 8.00000E-05 8.00000E-05 8.00000E-05

Blasting N/A N/A N/A Storing of material in landfill footprint storage

piles

3.13430E-03



Table VIII-4. Annual Material Handling Operation Emission Factors for Monitoring Annual Emissions

Operation Type or Area State

Emission Factor, lb/ton Basis

Borrow Area A Prior to initial receipt of solid waste 1.48886E-03 Year -2 S25 annualized daily emissions.

Borrow Area A After initial receipt of solid waste, more than 50,000 tons of landfill footprint excavation per month, and no borrow area excavation. 1.48886E-03

Year -2 S25 annualized daily emissions.

Borrow Area A After initial receipt of solid waste, less than or equal to 50,000 tons of landfill footprint excavation per month, and no borrow area excavation. 9.60955E-03

Year 22 S32. For excavation and loading, a worst case. Loading only would be significantly less.

Borrow Area A After initial receipt of solid waste, less than or equal to 50,000 tons of landfill footprint excavation per month, and borrow area excavation. 9.60955E-03

Year 22 S32. For excavation and loading.

Borrow Area B Prior to initial receipt of solid waste 1.48886E-03 Year -2 S25 annualized daily emissions.

Borrow Area B After initial receipt of solid waste, more than 50,000 tons of landfill footprint excavation per month, and no borrow area excavation. 1.48886E-03

Year 1 S26. Worst case unloading (BAB soil, i.e all unloading is assumed to be soil).

Borrow Area B After initial receipt of solid waste, less than or equal to 50,000 tons of landfill footprint excavation per month, and no borrow Area excavation. 1.17517E-02

Year 22 S32. For excavation and loading, a worst case. Loading only would be significantly less.

Borrow Area B After initial receipt of solid waste, less than or equal to 50,000 tons of landfill footprint excavation per month, and borrow area excavation. 1.17517E-02

Year 22 S32. For excavation and loading.

Landfill, MSW Y ≤ Y17 2.82744E-03 Expected emission factor. Landfill s, MSW Y > Y17 2.82744E-03 Expected emission factor.

Landfill, cover Y ≤ Y17 and no borrow area excavation has occurred 4.88228E-03 Expected emission factor when using landfill soil.

Landfill, cover Y > Y17 7.21468E-03

Expected emission factor when using excavated borrow area soil. If Y is greater than Y17, excavated borrow area soil is assumed to be used.

Landfill, cover Y ≤ Y17 and borrow area excavation has occurred 7.21468E-03 Expected emission factor when using excavated borrow area soil.



Landfill excavation, soil Cumulative landfill footprint excavation less than or equal to 6,845,000 tons 9.20485E-03 Expected emission factor. Landfill excavation, soil Cumulative landfill footprint excavation more than 6,845,000 tons 9.20485E-03 Expected emission factor. Landfill excavation, rock Cumulative landfill footprint excavation less than or equal to 6,845,000 tons 8.93279E-04 Expected emission factor. Landfill excavation, rock Cumulative landfill footprint excavation more than 6,845,000 tons 8.93279E-04 Expected emission factor. Liner insallation Cumulative landfill footprint excavation less than or equal to 6,845,000 tons 2.98812E-02 Expected emission factor. Liner insallation Cumulative landfill footprint excavation more than 6,845,000 tons 2.98812E-02 Expected emission factor. Fill Cumulative landfill footprint excavation less than or equal to 6,845,000 tons 1.02879E-02 Expected emission factor. Fill Cumulative landfill footprint excavation more than 6,845,000 tons 1.02879E-02 Expected emission factor.

Final cover installation North of Y17 2.98812E-02

Assumed same as clay liner installation. Although a final cover without a clay layer is proposed by the JTD, the JTD still contemplates potential alternatives.

Final cover installation South of Y17 2.98812E-02

Assumed same as clay liner installation. Although a final cover without a clay layer is proposed by the JTD, the JTD still contemplates potential alternatives.

Rock crushing in the landfill footprint Cumulative landfill footprint excavation less than or equal to 6,845,000 tons 2.97925E-03 Expected emission factor. Rock crushing in the landfill footprint Cumulative landfill footprint excavation more than 6,845,000 tons 2.97925E-03 Expected emission factor.

Rock crushing in BAB All times 5.94125E-03

Yr 17 S29. Expected emission factor. Includes scraper loading and unloading and 200 feet of transport of rock to rock crusher.

Intermediate storage pile All times 3.13430E-03

Year 1 S26. Expected emission factor.



ANNUAL UNMONITORED EMISSIONS Table VIII-5 shows the unmonitored annual emissions. The emissions in Table VIII-6 are based on the estimated maximum potential to emit of the sources that are unmonitored. The unmonitored sources include road grading emissions, travel on fill haul roads (Years -2 and 1), drilling, blasting, and wind erosion. Table VIII-6 shows the unmonitored annual emissions used in the monitoring. The end of the Phase II construction period is assumed to be when a cumulative total of 13,690,000 tons have been excavated from the landfill footprint.

Table VIII-5. Calculated Unmonitored Annual Emissions, tons

Year -2 1 17 17 South

End 22 23 Model Run As Adjusted or Modified by the District


S29 South End S32 N/A

Source All unmonitored 6.13 10.92 5.46 5.49 5.86 Wind erosion 3.39 5.83

4.94

14.16

Table VIII-6. Unmonitored Annual Emissions for Monitoring

Operational State Emissions, tons Basis

Cumulative landfill footprint excavation less than or equal to 6,845,000 tons 6.13 S25 Annualized Cumulative landfill footprint excavation more than 6,845,000 tons but less than or equal to 13,690,000 tons 10.92 S26 Cumulative landfill footprint excavation more than 13,690,000 tons 5.86 S32

Final cover installation after closure of the landfill to receipt of solid waste 14.16

Sum of wind erosion for S25 Annualized, S1, and S29 SouthEnda

aAreas added because entire landfill area will potentially be subject to wind erosion during final cover installation. This likely overestimates impact because of some overlap in areas and the higher elevation of the wind erosion areas compared to Year -2 and Year 1.



IX. MONITORING EXCAVATION AMOUNTS

To monitor emissions during excavation, it is necessary to estimate the amount and type of material excavated in the landfill footprint and its eventual use. For monitoring 24-hour impacts, the amount of excavation can be based on an estimated maximum potential to emit because the contribution at the PMI near the borrow areas is small near. However, for monitoring annual impacts the amount of soil and rock excavated and their destination—i.e., transported to a borrow area, exported from the facility, used as cover material, or used as fill—need to be monitored on a monthly basis. Since it is not clear if the total amount of excavation can be reliably and feasibly tracked on this time scale and also because it is difficult to monitor “rock” versus “soil” excavation, the monitoring procedure for monitoring excavation amounts is based on the following procedure that relies on monitoring the amount of material transported to BAA and BAB, exported from the facility, or used as cover on a monthly basis and estimating the amount of soil and rock excavated and amount of material used for fill in the landfill footprint from these values.

For any time period, the total weight of material excavated is given by:

𝑊𝐸𝑥𝑐𝑎𝑣,𝑡𝑜𝑡𝑎𝑙 = 𝑊𝐸𝑥𝑐𝑎𝑣,𝑠𝑜𝑖𝑙 + 𝑊𝐸𝑥𝑐𝑎𝑣,𝑟𝑜𝑐𝑘 (1)

Where:

𝑊𝐸𝑥𝑐𝑎𝑣,𝑡𝑜𝑡𝑎𝑙 is the total weight of material excavated, in tons; and

𝑊𝐸𝑥𝑐𝑎𝑣,𝑠𝑜𝑖𝑙 is the total weight of soil excavated, in tons; and 𝑊𝐸𝑥𝑐𝑎𝑣,𝑟𝑜𝑐𝑘 is the total weight of rock excavated, in tons.

Therefore, the weight fraction of rock to soil excavated is given by:

𝑓𝑟𝑜𝑐𝑘 =𝑊𝐸𝑥𝑐𝑎𝑣,𝑟𝑜𝑐𝑘

𝑊𝐸𝑥𝑐𝑎𝑣,𝑠𝑜𝑖𝑙 + 𝑊𝐸𝑥𝑐𝑎𝑣,𝑟𝑜𝑐𝑘 (2)

Or rearranging:

𝑊𝐸𝑥𝑐𝑎𝑣,𝑟𝑜𝑐𝑘 = �𝑓𝑟𝑜𝑐𝑘

1 − 𝑓𝑟𝑜𝑐𝑘�𝑊𝐸𝑥𝑐𝑎𝑣,𝑠𝑜𝑖𝑙 (3)



Where:

𝑓𝑟𝑜𝑐𝑘 is the weight fraction of rock in the excavated material.

Using equation 3 and rearranging equation (1) gives:

𝑊𝐸𝑥𝑐𝑎𝑣,𝑡𝑜𝑡𝑎𝑙 = 𝑊𝐸𝑥𝑐𝑎𝑣,𝑠𝑜𝑖𝑙 �1 + �𝑓𝑟𝑜𝑐𝑘

1 − 𝑓𝑟𝑜𝑐𝑘�𝑊𝐸𝑥𝑐𝑎𝑣,𝑠𝑜𝑖𝑙� (4)

The weight fraction of material used for fill is:

𝑓𝐹𝑖𝑙𝑙 =𝑊𝐹𝑖𝑙𝑙

𝑊𝐸𝑥𝑐𝑎𝑣,𝑠𝑜𝑖𝑙 + 𝑊𝐸𝑥𝑐𝑎𝑣,𝑟𝑜𝑐𝑘 (5)

Where:

𝑓𝐹𝑖𝑙𝑙 is the weight fraction of material used as fill in the landfill footprint in the total amount of material excavated and

𝑊𝐹𝑖𝑙𝑙 is the total weight of material used for fill, in tons

Substituting for 𝑊𝐸𝑥𝑐𝑎𝑣,𝑟𝑜𝑐𝑘and rearranging gives:

𝑊𝐹𝑖𝑙𝑙 = 𝑓𝑓𝑖𝑙𝑙𝑊𝐸𝑥𝑐𝑎𝑣,𝑠𝑜𝑖𝑙 �1 + 𝑓𝑟𝑜𝑐𝑘

1 − 𝑓𝑟𝑜𝑐𝑘� (6)

A mass balance on the amount of excavation transported:

𝑊𝐸𝑥𝑐𝑎𝑣,𝑡𝑜𝑡𝑎𝑙 = 𝑊𝐵𝐴𝐴 + 𝑊𝐵𝐴𝐵 + 𝑊𝐹𝑖𝑙𝑙 + 𝑊𝐶𝑜𝑣 + 𝑊𝐸𝑥𝑝𝑜𝑟𝑡 (7)

Substituting for 𝑊𝐸𝑥𝑐𝑎𝑣,𝑡𝑜𝑡𝑎𝑙and 𝑊𝐹𝑖𝑙𝑙 and rearranging gives:



𝑊𝐸𝑥𝑐𝑎𝑣,𝑠𝑜𝑖𝑙 =𝑊𝐵𝐴𝐴 + 𝑊𝐵𝐴𝐵 + 𝑊𝐶𝑜𝑣 + 𝑊𝐸𝑥𝑝𝑜𝑟𝑡

�1 − 𝑓𝑓𝑖𝑙𝑙� �1 + 𝑓𝑟𝑜𝑐𝑘1 − 𝑓𝑟𝑜𝑐𝑘

� (8)

Where:

𝑊𝐵𝐴𝐴,𝑈𝑛𝐿𝑑 is the total weight of material from the Landfill Footprint delivered to BAA , in tons; 𝑊𝐵𝐴𝐵,𝑈𝑛𝐿𝑑 is the total weight of material from the Landfill Footprint delivered to BAB , in tons; 𝑊𝐸𝑥𝑝𝑜𝑟𝑡 is the total weight of material from the Landfill Footprint exported offsite from the Landfill Footprint , in tons; and

𝑊𝐶𝑜𝑣 is the weight of cover material that is delivered to the working face that was excavated from the Landfill Footprint and not stored in Borrow Area A or Borrow Area B at any time.

If the weight fractions of fill and rock are known, then the weight of soil excavated can be calculated by equation 8 from the monitored values of the transported material and then the weight of rock and material used as fill can be calculated from equations 3 and 5, repectively. above.

The average weight fraction of rock and fill for Phase I and Phase II of landfill construction were calculated from the total excavation, rock excavation, and fill volumes indicated on the figure “Gregory Canyon Landfill Excavation Over 50 Feet Deep,” Bryan A. Stirrat & Associates, 5-2004. The District notes that some of the amounts of soil and rock per parcel appear to be inconsistent in this figure—but the total amounts of material excavated are consistent with other documents in the JTD and provided in the application. The weight fraction of rock indicated on this document is relatively small compared to other material balances submitted by the applicant which assume a much higher fraction of rock. This provides a conservatively high estimate of the amount of soil excavated, which has a much higher excavation emission factor compared to rock. . The amount of rock indicated on the figure approximately corresponds to the amount blasted in the landfill phases.

Volumes of material were converted to weights by using a densities of 3700 and 4600 lb/BCY for soil and rock, respectively. All fill was assumed to be soil. These weight fractions for Phase I and Phase II of the landfill construction are used to monitor the amount of soil and rock excavated and the amount of material used as fill on a calendar monthly basis.

Although Phase I and Phase II might each last 2 years or longer, it is assumed the average weight fractions are reasonably representative on a monthly basis. Phases III and Phase IV



were not addressed because they involve much less excavation than Phases I and II and the excavation takes place at the south end of the landfill farther from the annual PMI at the northern end

The amounts of material and calculated weight fractions are shown in Table IX-1. Substituting these values into the equations above gives the following sets of monitoring equations:

Table IX-1 Excavation Weight Calculation Parameters

Parameter Phase I Phase II Total excavation, bcy 3,807,879 3,204,971 Rock excavation, bcy 640,322 36,600 Fill, bcy 822,828 860,241 Soil density, lb/bcy 3,700 3,700 Rock density, lb/bcy 4,600 4,600 Weight of soil excavated, tons 5,859,980 5,861,486

Weight of rock excavated, tons 1,472,741 84,180

Weight of fill (assume soil), tons 1,522,232 1,591,446

Weight fraction rock, 0.201 0.014 Weight fraction fill, 0.208 0.268 Soil coefficient 1.009 1.346 Rock coefficient 0.253 0.019 Fill coefficient 0.262 0.365

For Phase I (there are no landfill cover operations in Phase I),

𝑊𝐸𝑥𝑐𝑎𝑣,𝑠𝑜𝑖𝑙 = 1.009�𝑊𝐵𝐴𝐴,𝑈𝑛𝐿𝑑 + 𝑊𝐵𝐴𝐵,𝑈𝑛𝐿𝑑 + 𝑊𝐸𝑥𝑝𝑜𝑟𝑡 �

𝑊𝐸𝑥𝑐𝑎𝑣,𝑟𝑜𝑐𝑘 = 0.253�𝑊𝐵𝐴𝐴,𝑈𝑛𝐿𝑑 + 𝑊𝐵𝐴𝐵,𝑈𝑛𝐿𝑑 + 𝑊𝐸𝑥𝑝𝑜𝑟𝑡�

𝑊𝐹𝑖𝑙𝑙 = 0.262�𝑊𝐵𝐴𝐴,𝑈𝑛𝐿𝑑 + 𝑊𝐵𝐴𝐵,𝑈𝑛𝐿𝑑 + 𝑊𝐸𝑥𝑝𝑜𝑟𝑡�

And for Phase II,

𝑊𝐸𝑥𝑐𝑎𝑣,𝑠𝑜𝑖𝑙 = 1.346�𝑊𝐵𝐴𝐴,𝑈𝑛𝐿𝑑 + 𝑊𝐵𝐴𝐵,𝑈𝑛𝐿𝑑 + 𝑊𝐸𝑥𝑝𝑜𝑟𝑡 + 𝑊𝐶𝑜𝑣�

𝑊𝐸𝑥𝑐𝑎𝑣,𝑟𝑜𝑐𝑘 = 0.019�𝑊𝐵𝐴𝐴,𝑈𝑛𝐿𝑑 + 𝑊𝐵𝐴𝐵,𝑈𝑛𝐿𝑑 + 𝑊𝐸𝑥𝑝𝑜𝑟𝑡 + 𝑊𝐶𝑜𝑣�



𝑊𝐹𝑖𝑙𝑙 = 0.365�𝑊𝐵𝐴𝐴,𝑈𝑛𝐿𝑑 + 𝑊𝐵𝐴𝐵,𝑈𝑛𝐿𝑑 + 𝑊𝐸𝑥𝑝𝑜𝑟𝑡 + 𝑊𝐶𝑜𝑣�

X. MONITORING AREA FOR SOUTHERN LANDFILL 24-HOUR AMBIENT AIR QUALITY IMPACTS

Because the 24-hour impacts drop off rapidly with distance monitoring of ambient air quality impacts is only required within a certain distance of the southern property boundary. The District estimates that the maximum impact would be reduced by about a factor of four if landfill operations are more than 400 feet from the southern property line, which is sufficient for compliance with the 24-hour ambient air quality standard.

XI. SLOPING TERRAIN

The regulatory default option for AERMOD was used in the modeling done to support the application both by the applicant and the District. The default option includes the effects of complex terrain. Although this is usually the most accurate approach, the AERMOD implementation guidance (EPA 2009) indicates that AERMOD may sometimes underestimate impacts on gently sloping terrain for downslope winds (e.g. gravity driven flows, which typically occur due to nocturnal surface cooling) for receptors at lower elevation than the source. This is also true for upslope winds for nonbuoyant low-level plumes for receptors at higher elevations than the source. The modeling guidance suggests that the flat terrain option be used (i.e., without accounting the effects of terrain) when expert opinion is that these effects may be important. However, discussions with EPA indicated there is little, if any, actual data to support one modeling approach over another in these situations.

Terrain following downslope flows for receptors near the property line at the northern end of the canyon could occur where annual emissions are important. 24-hour impacts may occur near BAA and BAB for downslope winds and near the southern property line for upslope winds. However, the maximum 24-hour impacts are less likely to be significantly affected because those impacts are largely the result of sources very close to, and near the same elevation, as the PMI receptor

Gravity driven flows would impact receptors on the northern property line where the PMIs for annual impacts are located (the long axis of the canyon and landfill is roughly oriented along a north-south axis with the southern end being approximately 700 feet higher than the northern end). The effect of such flows on PM10 emissions in Gregory Canyon would be limited since the landfill operations are limited to the hours of 7 AM to 6 PM on most days (a limited amount of operations are allowed for one additional hour in the evening on 66 day per year). Another situation would be southerly winds flows which would have the same potential impact on the northern annual PMI.



One indicator that nongravity driven terrain following flows would occur is if the flow over a hill does not separate from the surface. A preliminary evaluation based on criteria for the critical slope needed to cause separation (Wood 1995) indicates that within the landfill footprint, for an along axis southerly wind, the maximum slope for the waste surface (estimated 3:1 horizontal to vertical for 20 foot wide benches every 40 feet in elevation) would be right at the critical slope for separation for a neutral turbulent flow assuming a hill half-width of about 1700 m for the overall landfill waste slope and for a surface roughness height of 0.3 m. This is approximately the surface roughness predicted by the AERMOD modeling package for modeling this facility. However, several parameters are known to affect the critical slope necessary for separation (Wood 1995, Jiang et al. 2007, Ayotte and Hughs 2003, Brown et al. 2001, Finnigan and Belcher 2004). Surface heating increases the critical slope and would make terrain following more likely. Surface cooling, increased surface roughness, canyon walls, and a vegetation canopy—likely over much of the sloped waste surface at the facility—would be expected to decrease the critical slope and make terrain following less likely.

Although the District is continuing to investigate this issue, the District has decided, based on the above, that the regulatory default option is adequate to assess the PM10 and other emissions for this project.

final draft engineering evaluation gregory …...• one (1) blower with a tbd hp electric motor,...

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