former santa clara all-purpose landfill city place santa

POST-CLOSURE LAND USE PLAN Former Santa Clara All-Purpose Landfill

City Place Santa Clara

5500 Lafayette Street

Santa Clara, California

Prepared For:

Related Santa Clara, LLC

333 South Grand Avenue, Suite 3550

Los Angeles, California 90071

Prepared By:

Langan Treadwell Rollo

555 Montgomery Street, Suite 1300

San Francisco, California 94111

DJ Hodson, PE

Principal

Jeffrey F. Ludlow, PG

Principal

September 2015

Langan Project No. 770611601

Post-Closure Land Use Plan

Former Santa Clara All-Purpose Landfill




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TABLE OF CONTENTS

1.0 INTRODUCTION AND BACKGROUND ......................................................................... 1 1.2 Site Description.................................................................................................. 2 1.3 Site Background ................................................................................................. 3 1.4 Project Description ............................................................................................ 4 1.5 Previous Investigations ..................................................................................... 5

1.5.1 Solid Waste Assessment Test ............................................................... 5 1.5.2 Ongoing Semi-Annual Monitoring ........................................................ 5 1.5.3 Recent Soil, Groundwater, and Landfill Gas Investigations ................ 6 1.5.4 Human Health Risk Assessment ........................................................... 7

1.6 Feasibility Study of Groundwater Alternatives ............................................. 10

2.0 GEOLOGY AND HYDROGEOLOGICAL INFORMATION ............................................. 14 2.1 Subsurface Conditions .................................................................................... 15 2.2 Hydrological Information ................................................................................ 19

3.0 SOIL AND WASTE MANAGEMENT ............................................................................ 22 3.1 Waste Management During Construction ..................................................... 22 3.2 Nuisance Control Measures ............................................................................ 24

3.2.1 Dust, Litter, and Vectors ...................................................................... 24 3.2.2 Traffic Control ....................................................................................... 25

3.3 Health and Safety Program ............................................................................. 25

4.0 SITE DEMOLITION AND PREPARATION .................................................................... 26

5.0 CONCEPTUAL FOUNDATION ..................................................................................... 27 5.1 Structures ......................................................................................................... 27 5.2 Site Settlement Evaluation ............................................................................. 27 5.3 Seismic Hazards Analysis ................................................................................ 29

5.3.1 Liquefaction .......................................................................................... 29 5.3.2 Seismic Densification ........................................................................... 30 5.3.3 Lateral Spreading ................................................................................. 30 5.3.4 Surface Faulting ................................................................................... 30 5.3.5 Tsunami ................................................................................................ 30

5.4 Proposed Foundation Options ........................................................................ 31 5.4.1 Spread Footings on DDCs .................................................................... 31 5.4.2 Auger Cast In Place Piles ..................................................................... 32 5.4.3 Load Tests and Construction Issues ................................................... 33

6.0 FINAL COVER ............................................................................................................... 34 6.1 Final Cover Design ........................................................................................... 34

6.1.1 General Earthwork Recommendations ............................................... 35 6.1.2 Foundation Layer ................................................................................. 35 6.1.3 Low Permeability Layer ....................................................................... 36 6.1.4 Fill above Low Permeability Layer ...................................................... 37 6.1.5 Utility Trenches .................................................................................... 38






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TABLE OF CONTENTS

(Continued)

6.2 Existing Topography ....................................................................................... 38 6.3 Preliminary Grading ......................................................................................... 40 6.4 Preliminary Stormwater Management .......................................................... 41

7.0 IRRIGATION AND LANDSCAPING .............................................................................. 44

8.0 UTILITIES ..................................................................................................................... 44

9.0 ENHANCED LANDFILL GAS COLLECTION AND REMEDIATION SYSTEM ............... 46 9.1 Existing LFG Collection System ...................................................................... 46 9.2 Proposed LFG Collection System ................................................................... 47

9.2.1 Proposed LFG Collection Wells ........................................................... 48 9.2.2 Potential Off-Site LFG Migration Monitoring and Mitigation ........... 51 9.2.3 Proposed LFG Collection System Manifold ........................................ 52 9.2.4 Process Equipment............................................................................... 53 9.2.5 Settlement Considerations .................................................................. 54 9.2.6 Other LFG Collection System Design Considerations ....................... 55

9.3 Proposed LFG Collection System Remedial Benefits .................................... 56 9.4 Conceptual Field Implementation Plan .......................................................... 57 9.5 LFG Collection System Monitoring Plan ........................................................ 61

10.0 LANDFILL GAS CONTROL ........................................................................................... 62 10.1 Vapor Barrier Membrane ................................................................................. 62

10.1.1 Platform Structure Area ....................................................................... 62 10.1.2 Non-Platform Structure Area .............................................................. 63

10.2 Passive Vapor Collection and Venting System .............................................. 63 10.2.1 Platform Structure Area ....................................................................... 63 10.2.2 Areas Outside the Platform Structure ................................................ 64

10.3 Exterior Grade Beam Inlet Vents .................................................................... 64 10.4 Contingency Active Blower System ............................................................... 64 10.5 Automatic Methane Sensor Network ............................................................ 66 10.6 Construction Quality Assurance Manual ........................................................ 67

11.0 LEACHATE COLLECTION AND REMOVAL SYSTEM ................................................. 68 11.1 Existing LCR System ....................................................................................... 68 11.2 Proposed LCR System ..................................................................................... 68 11.3 Considerations for LCR System at the Site .................................................... 72 11.4 Conceptual Field Implementation Plan .......................................................... 72 11.5 LCR System Monitoring Plan .......................................................................... 73

12.0 GROUNDWATER AND SURFACE WATER MONITORING ......................................... 74

13.0 EMERGENCY RESPONSE ............................................................................................ 74 13.1 High Methane at Buildings .............................................................................. 74 13.2 Other Emergency Situation............................................................................. 76






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TABLE OF CONTENTS

(Continued)

14.0 OPERATION AND MAINTENANCE PLAN ................................................................... 77 14.1 Final Cover Inspection and Maintenance ....................................................... 77 14.2 Drainage Features Inspection and Maintenance ........................................... 79 14.3 LFG System Inspection and Maintenance ...................................................... 79 14.4 LFGMS Inspection and Maintenance .............................................................. 79 14.5 LCR System Inspection and Maintenance ...................................................... 80 14.6 Groundwater Monitoring System Inspection and Maintenance .................. 80 14.7 Reporting .......................................................................................................... 80 14.8 Planned or Emergency Subsurface Activities ................................................ 81

15.0 SATISFACTION OF POST-CLOSURE LAND USE REQUIREMENTS .......................... 81

16.0 REFERENCES ............................................................................................................... 83

TABLES

FIGURES

APPENDICES






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LIST OF TABLES

Table 1 Current Development Program

Table 2 Summary of Thickness of Cover Soil, Low Permeability Layer, and

Refuse

Table 3 Summary of Depth to Groundwater

Table 4 Compliance Requirements – Methane Action Levels

Table 5 Compliance Requirements – Final Landfill Cover Maintenance

LIST OF FIGURES

Figure 1 Site Location Map

Figure 2 Site Map






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LIST OF APPENDICES

Appendix A Existing Systems

Existing Landfill Gas Collection System

• 8190-P, Santa Clara Landfill, Landfill Gas Recovery System, Real

Environmental Products, 28 April 2011

• Figures 1 through 6, Plans and Details, Santa Clara Landfills, Landfill Gas

Recovery System, Emcon Associates, April 1985

Existing Leachate Recovery System

• Drawings 1 through 4, Parcel 1 Northwest All Purpose Landfill Company,

Inc., Emcon Associates, 30 May 1990

• Drawings 1 through 6, Parcel 3/6 All Purpose Landfill Company, Inc.,

Emcon Associates, 30 May 1990

Existing Groundwater Monitoring Network

• Figure 2, Piezometric Surface Contour Map, February 24, 2014, Golder

Associates, 3 June 2014

Appendix B Phasing Concept Map (Elkus Manfredi Architects, 16 July 2014)

Appendix C Preliminary Architectural Drawings (Pending Preparation)

Building Plans

Exterior Elevations

Building Sections

Appendix D Preliminary Design Drawings

Figure GI1.01, Title Sheet

Figures VT2.01-VT2.04, Topographic Map

Figures CC2.01-CC2.04, Site Constraints Map

Figures CD2.01-CD2.04, Demolition Plan

Figures CS2.01-CS2.04, Site Plan

Figures CG2.01-CG2.04, Preliminary Grading Plan

Figures CG3.01-CG3.05, Grading Profiles Figure BF1.01, Conceptual

Foundation Plan

Figures CSS2.01-CSS2.04, Preliminary Sanitary Sewer Plan

Figures CSD2.01-CSD2.04, Preliminary Storm Drain Plan

Figures SDW2.01-SDW2.04, Preliminary Water Plan






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Figures CE2.01-CE2.04, Soil Erosion and Sediment Control Plan

Figures CT2.01-CT2.04, Preliminary Stormwater Management Plan

Figure BF5.01, Conceptual Foundation Sections

Figure BF5.02, Conceptual Foundation Details

Figures CU5.01-CU5.07, Utility Details

Figure CE5.01, Soil Erosion and Sediment Control Details

Appendix E Previous Environmental Investigation Results (figures and tables from Draft Site

Investigation and Environmental Risk Assessment Report, City Place Santa

Clara, Langan Treadwell Rollo, 23 December 2014)

Figure 3, Site Plan with Groundwater Sample Locations

Figure 4, Site Plan with Soil Sample Locations

Figure 5, Site Plan with Landfill Gas Sample Locations

Figure 6a, Benzene in Landfill Gas (Collected from LFG Extraction Wells)

Figure 6b, Benzene in Landfill Gas (Collected from Temporary Probes)

Figure 6c, Benzene Exceedances in Landfill Gas

Figure 7a, Ethylbenzene in Landfill Gas (Collected from LFG Extraction

Wells)

Figure 7b, Ethylbenzene in Landfill Gas (Collected from Temporary

Probes)

Figure 7c, Ethylbenzene Exceedances in Landfill Gas

Figure 8a, Vinyl Chloride in Landfill Gas (Collected from LFG Extraction

Wells)

Figure 8b, Vinyl Chloride in Landfill Gas (Collected from Temporary

Probes)

Figure 8c, Vinyl Chloride Exceedances in Landfill Gas

Figure 9, Conceptual Site Model

Figure 10, Illustrated Conceptual Site Model

Table 1, Historical Groundwater Analytical Results

Table 2, Soil Analytical Results – VOCs

Table 3, Soil Analytical Results – Other Non Metals

Table 4, Soil Analytical Results – Metals

Table 5, Grab Groundwater Analytical Results

Table 6, Landfill Gas Analytical Results

Table 7, Summary of Thickness of Cover Soil, Clay Cap, and Refuse and

Depth to Groundwater

Table 8 , Groundskeeper Hazard and Risk Summary






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Table 9 , Calculations of Blood Lead Concentrations (PbBs) and

Preliminary Remediation Goal (PRG), Groundskeeper Table 10, Construction Worker Hazard and Risk Summary Table 11, Calculations of Blood Lead Concentrations (PbBs) and

Preliminary Remediation Goal (PRG)

Table 12, J&E Soil Gas Model Summary by Parcel

Table 13, J&E Site-Wide Groundwater Model Summary

Appendix F Existing Permits

Waste Discharge Requirements R2-2002-0008, California Regional Water

Quality Control Board, 23 January 2002

Permit to Operate, Bay Area Air Quality Management District, 23 October

2014

Appendix G Boring Logs and Cross Sections

Boring Logs

Figure 1, Site Plan depicting Cross Sections

Figure 2, Idealized Subsurface Profile A-A’

Figure 3, Idealized Subsurface Profile B-B’

Appendix H Waste Management Plan

Appendix I Odor Management Plan

Appendix J Conceptual Foundation Plan and Details and Draft Landfill Cover Investigation

Report

Figure BF1.01, Conceptual Foundation Plan

Figure BF5.01, Conceptual Foundation Sections

Figure BF5.02, Conceptual Foundation Details

Figure 1, Building Edge with Wall

Figure 2, Building Edge with Lightweight Concrete Wall

Figures 7 and 8 from Draft Preliminary Geotechnical Investigation, City

Place Santa Clara, Langan Treadwell Rollo, 22 August 2014.

Draft Landfill Cover Investigation report, Langan Treadwell Rollo,

19 December 2014






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Appendix K Proposed Landfill Gas Collection and Remediation System Concept Plans

(figures from Draft Technical Memorandum, Enhanced Landfill Gas Collection

and Remediation System Reconstruction Concept Plans, City Place Santa Clara,

30 January 2015)

Figure 9, Proposed Conceptual Landfill Gas Collection System Well and

Manifold Layout

Figure 9A, Proposed Conceptual Landfill Gas Collection System Well and

Manifold Layout, Parcel 1

Figure 9B, Proposed Conceptual Landfill Gas Collection System Well and


Figure 9C, Proposed Conceptual Landfill Gas Collection System Well and

Manifold Layout, Parcel 3/6

Figure 9D, Proposed Conceptual Landfill Gas Collection System Well and


Figure 9E, Proposed Conceptual Landfill Gas Collection System Well and

Manifold Layout, Proposed Contingent Horizontal Wells – Parcel 4

Figure 10A, Proposed Landfill Gas Collection System Conceptual Details

Figure 10B , Proposed Landfill Gas Collection System Conceptual Details

Figure 11, Proposed Conceptual All Parcels Manifold Schematic

Figure 12, Proposed Condensate Collection System Layout

Figure 13, Existing Process Equipment and Proposed Modifications

Figure 14, Interim Measures for Grading and Development – Phase 1

Figure 15, Interim Measures for Excavation at Parcel 3/6

Figure 16, Existing Landfill Gas Collection System Isolation and

Abandonment Phase-Out Plan

Figure 17, Conceptual Schematic of Potential Void Space Under

Structural Slab

Appendix L Conceptual Landfill Gas Mitigation System Design Drawings (figures from Draft

Gas Building Mitigation System Basis of Design and Conceptual Plans, City Place

Santa Clara, 23 December 2014)

Figure MT 1.01, Landfill Gas Building Mitigation System Project Plan

Figure MT 1.02, Phase 1-2 Development Area Conceptual Landfill Gas

Building Mitigation Plan






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Figure MT 1.03, Phase 3 Development Area Conceptual Landfill Gas










Figure MT 2.01, Conceptual Landfill Gas Building Mitigation Plan Details

Figure MT 2.02, Conceptual Landfill Gas Building Mitigation Plan Details

Figure MT 3.01, Conceptual Methane Gas Building Monitoring System

Appendix M Leachate Collection and Removal System Concept Plan (figure from Draft

Technical Memorandum, Leachate Collection and Removal System Concept

Plans, City Place Santa Clara, 6 February 2015)

Figure 9, Layout of Existing/Proposed Leachate Recovery System






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POST-CLOSURE LAND USE PLAN





1.0 INTRODUCTION AND BACKGROUND

The City of Santa Clara ( the ‚City‛), as owner and operator of the former Santa Clara All-

Purpose Landfill (Landfill), presents this Post-Closure Land Use Plan (the ‚Plan‛) for the

redevelopment and repurposing of the Landfill. The City proposes to lease City-owned

property, which includes the former Landfill, to Related Santa Clara, LLC (Related) for purposes

of developing City Place Santa Clara (Project), a new multi-building mixed-use development.

The Project will include demolishing existing above-ground improvements and constructing

new buildings and site improvements. Some of the in-ground landfill gas extraction system

(LFG system), leachate collection and removal systems (LCR systems), and landfill cover will be

abandoned, modified and enhanced. The final design and construction of the Project will be

reviewed by the Santa Clara County Department of Environmental Health Local Enforcement

Agency (LEA), the California Department of Resources, Recycling, and Recovery (CalRecycle),

the San Francisco Bay Regional Water Quality Control Board (RWQCB), the Bay Area Air Quality

Management District (BAAQMD), and the City of Santa Clara Planning Department.

Structural improvements developed on landfills must comply with specific construction

standards set forth in California Code of Regulations (CCR), Title 27, §21190. The Plan is being

developed in general accordance with these requirements. The final Plan will be presented for

regulatory agency approval and will provide the basis for preparing a Revised Corrective Action

Plan and Revised Post-Closure Maintenance Plan based on Design and Construction

Documents for the development.

The Plan is organized as follows:

Section 1.0 – Introduction and Background

Section 2.0 – Geology and Hydrogeological Information

Section 3.0 – Waste Management

Section 4.0 – Site Demolition and Preparation

Section 5.0 – Conceptual Foundation






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Section 6.0 – Final Cover

Section 7.0 – Irrigation and Landscaping

Section 8.0 – Utilities

Section 9.0 – Enhanced Landfill Gas Collection and Remediation System

Section 10.0 – Landfill Gas Control

Section 11.0 – Leachate Collection and Removal System

Section 12.0 – Groundwater and Surface Monitoring

Section 13.0 – Emergency Response

Section 14.0 – Operation and Maintenance

Section 15.0 – Satisfaction of Post-Closure Land Use Requirements

Section 16.0 – References

1.2 Site Description

The overall project site (the ‚Site‛) totals 240 acres and includes four areas designated as

Landfill Parcels 1/1NW, 2, 3/6 and 4 (see Figures 1 and 2) and an area south of and outside the

landfill designated as Parcel 5. Landfill Parcel (‚Parcel‛) designations at the Site are based on

available historical documents, including the Solid Waste Assessment Tests (SWATs) prepared

for the Site (Kenneth D. Schmidt and Associates [KSA], 1988 and Emcon Associates [Emcon],

1988).

The Site boundaries include Lafayette Street, Great America Parkway, Stars and Stripes Drive,

Centennial Boulevard, Tasman Drive the Guadalupe River, and the San Tomas Aquino Creek.

The Site, owned by the City, is currently occupied by the Santa Clara Golf and Tennis Club on

Parcels 2, 3/6, and 4, the Santa Clara Police Action League BMX course on Parcel 1/1N/W, a

City of Santa Clara firehouse on Parcel 4 and paved parking lots on Parcel 5. Associated

addresses include 5451 Lafayette Street, 5500 Lafayette Street, and 5155 Stars and Stripes

Drive. The surrounding land uses generally include commercial and industrial uses to the north

(including the Gateway Development to the northwest and a stormwater retention basin to the

northeast), residential communities to the east, general commercial uses to the south

(including buildings associated with the golf course, a football stadium, and a large commercial

park), and commercial uses to the west (remaining portions of the Gateway Development,

other commercial parks, and the Santa Clara Convention Center).






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1.3 Site Background

Portions of the Site (approximately 136 acres) were reported in regulatory documents to be

used for landfill operations between 1934 and 1993 (RWQCB, 2002); however, review of

historical aerial photographs and topographic maps show that landfill operations began only in

the late 1960s, taking place on Parcel 4 from sometime in the 1960s through at least 1977, on

Parcel 2 between approximately 1977 and 1984, on Parcel 1 between approximately 1982 and

1986, and on Parcel 3/6 between approximately 1986 and 1991. Landfill operations resumed

on the Parcel 1NW area (the northwest corner of Parcel 1) in 1991 and continued until the last

refuse was accepted in 1993 (Golder Associates [Golder], 2014b). The Site has been used as

the current golf course and BMX facility since about 1993. The south eastern portion of the

Site is occupied by the City of Santa Clara Fire Station; however, this facility is not underlain by

refuse.

Refuse accepted at Parcels 1/1NW and 2 reportedly included rubbish and residential,

commercial, and industrial garbage and refuse (KSA, 1988). Refuse accepted at Parcel 3/6

reportedly included non-hazardous solid waste. Parcel 4 was reportedly used initially as an

open burning dump and later accepted only dry material, construction debris, yard refuse, and

non-garbage items. Recent investigations at the Site have encountered mixed refuse items

including wood, paper, plastic, ceramics, glass, metals, and cloth in the refuse units. The total

mass of refuse placed is estimated to be 5.5 million tons (Air Science Technologies, Inc., 2012).

The Landfill is no longer active and the Final Closure and Post Closure Maintenance Plan for all

parcels (Emcon, 1992) was approved by the California Integrated Waste Management Board

(CIWMB) in December 1992 and amended multiple times, most recently in December 2013

(Golder, 2013). The CIWMB approved the Landfill Closure Certification Report for the Site in

November 1994.

All parcels include a LFG system consisting of 75 active vertical landfill gas (LFG) extraction

wells connected by horizontal laterals to a landfill gas-to-energy flare system operated by

Ameresco (Golder, 2014a), a private company under contract with the City of Santa Clara.

Parcel 1NW and Parcel 3/6 were developed with a LCR system consisting of a central sump,

laterals, risers and pumps. Additionally, a groundwater monitoring well system and a LFG

monitoring probe network are present at the Site (Golder, 2014b). The City is currently

responsible for all monitoring and reporting programs related to the LFG system, LCR system,

and groundwater well network per applicable regulations (see Appendix A for existing system






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and monitoring well network). Further information on these existing systems is provided in

Sections 9.1, 11.1, and 12.0, respectively.

1.4 Project Description

Related proposes to fully redevelop the Site. Parcel 4 is planned for redevelopment as mixed-

use including retail/entertainment, hotel and office and residential. Residential apartment units

would be constructed above a podium garage structure or above at least one floor of retail

space. The planned future uses for the remaining Parcels included office, rental, and hotel.

Enclosed basement construction will be prohibited.

The Site is zoned ‚B‛ in the City of Santa Clara 2010-2035 General Plan, which is the Public,

Quasi-Public and Public Park or Recreation Zoning District and a portion of Parcel 5 is zoned

‚CP‛ Commercial Park. The City is currently preparing an Environmental Impact Report

reviewing a proposal to approve an amendment to the General Plan and Zoning Ordinance to

change the zoning to a new designation to be called ‚Urban Center/Entertainment District.‛ At

the same time, the City will consider a proposal to approve a Master Community Plan for the

Site. The Project (Related, March 2014) includes up to 9,164,400 gross square feet (gsf) with

associated parking and Site improvements. The current breakdown by Parcel is as follows:

Table 1

Current Development Program

Parcel Parcel Area

(acres)

Potential Development Area

(gsf)

1/1NW 49.6 1,200,000

2 60.9 2,160,000

3/6 34.9 720,000

4 86.6 4,259,400

5 8.0 825,000

The proposed development will occur in phases (see Phasing Strategy in Appendix B) with the

development on Parcel 4 and 5 likely proceeding in the first four phases. The conceptual Site

layout is depicted in the conceptual architectural renderings included in Appendix C (pending

preparation) and the preliminary design drawings included in Appendix D. Since it is outside of

the landfill property, development plans at Parcel 5 are not subject to PCLUP requirements.






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1.5 Previous Investigations

Previous investigations at the Site include the Solid Waste Assessment Test (SWAT) Reports

prepared prior to the Landfill closure (KSA, 1988 and Emcon, 1988), semi-annual monitoring

conducted by several consultants on behalf of the City from 1985 to the present, and recent

soil, groundwater, and LFG investigations by Langan Treadwell Rollo (Langan, 2014e). Figures

and tables summarizing the results of the recent soil, groundwater, and LFG investigations are

included in Appendix E.

1.5.1 Solid Waste Assessment Test

In June 1987, the City received correspondence from the RWQCB that a SWAT for the Site

was required. The Water Part of the SWAT was prepared for the Site in 1988 (KSA, 1988).

Based on the findings of the Water Part of the SWAT, elevated concentrations of volatile

organic compounds (VOCs) were encountered in groundwater beneath portions of Parcel 4 and

Parcel 3/6.

The Air Quality SWAT was prepared for the Site in 1988 (Emcon, 1988). At the time of the Air

Quality SWAT, LFG at the Site was generally comprised of methane, carbon dioxide and some

VOCs, including benzene, methylene chloride, tetrachloroethene (PCE), trichloroethene (TCE),

vinyl chloride, and 1,1,1-trichloroethane (1,1,1-TCA).

1.5.2 Ongoing Semi-Annual Monitoring

As part of the Waste Discharge Requirements (WDRs) issued by the RWQCB to the City for

the Site, Golder (on behalf of the City) continues to monitor groundwater, leachate, and surface

water at the Site and near vicinity; the WDRs for the Site are included in Appendix F. Based on

the most recent data (Golder, 2014b), the primary VOCs in groundwater include 1,1-

dichloroethene (1,1-DCE), cis-1,2-DCE, trans-1,2-DCE, TCE, and vinyl chloride. Several other

VOCs, including carbon disulfide, methyl tert butyl ether (MTBE), and chloroform, have been

detected at trace levels intermittently during continued groundwater monitoring at the Site.

Groundwater monitoring results confirm the presence of elevated VOC concentrations in a

limited area at the northeastern portion of Parcel 4 and southeastern portion of Parcel 3/6 (see

Figure 3 in Appendix E). The distribution of the VOCs has not changed significantly since the

1988 SWAT (more than 25 years).

As part of the BAAQMD requirements for the Site, Golder regularly conducts surface emissions

testing for methane; monitors LFG at extraction wellheads for methane, carbon dioxide, and






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oxygen; and analyzes LFG at the flare for several compounds, including selected VOCs,

methane, and hydrogen sulfide. The BAAQMD permit to operate (PTO) for the Site is included

in Appendix F. Based on the most recent data (Golder, 2014a), typical constituents of LFG such

as hydrogen sulfide, methane, and several VOCs, including benzene, chlorobenzene,

chloroethane, 1,1-dichloroethane (1,1-DCA), ethanol, ethylbenzene, hexane, 2-butanone (MEK),

4-methyl-2-pentanone (MIBK), toluene, vinyl chloride, and xylenes continue to be detected in

LFG at the flare. Additionally, methane is regularly detected at the extraction wellheads during

the wellhead performance monitoring. Surface emissions testing along designated walking

routes throughout the Site did not detect methane above the 500 parts per million by volume

(ppmv) screening level during the 2013 screening events (Golder, 2014a). Furthermore, based

on monitoring by Golder, surface emission monitoring has never detected methane above

500 ppmv.

1.5.3 Recent Soil, Groundwater, and Landfill Gas Investigations

The summary of existing environmental conditions as described above is based on information

obtained from the SWATs prepared for the Site (KSA, 1988 and Emcon, 1988) and ongoing air,

groundwater, and LFG monitoring by Golder (Golder, 2014a and 2014b). As part of its

consideration of certain environmental aspects of the Project, the RWQCB in 2013 requested a

comprehensive soil, groundwater, and LFG investigation at the Site. The scope was developed

in coordination and with concurrence from the RWQCB (Langan, 2014a, 2014b, and 2014d;

RWQCB, 2014a, 2014b, and 2014c). As a result, several soil, groundwater, and LFG

investigations were conducted at the Site between April 2014 and October 2014. The

investigations included:

Drilling 38 soil borings to depths between 5 and 200 feet below grade for the collection

of soil within the cap layer (hereafter referred to as cap samples, for brevity), soil within

the refuse unit (hereafter referred to as refuse samples, for brevity), native soil, and

groundwater samples throughout the Site (see Figures 3 and 4 in Appendix E);

Collecting LFG samples from 32 selected existing landfill extraction wells throughout

the Site while the LFG system was in operation (see Figures 6a, 7a, and 8a in Appendix

E); and

Installing 14 temporary LFG probes for the collection of LFG samples throughout the

Site (see Figures 6b, 7b, and 8b in Appendix E).






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The laboratory analytical results from the conducted investigations generally indicated:

The cap is comprised of a low permeability layer and cover soil above the refuse;

In groundwater samples, concentrations of total petroleum hydrocarbons in the gasoline

range (TPHg), diesel range (TPHd), and motor oil range (TPHmo), and several VOCs,

including benzene, tert butyl alcohol (TBA), cis-1,2-DCE, naphthalene, TCE, and vinyl

chloride are above groundwater Environmental Screening Levels (ESLs) in Parcels 3/6

and 4 of the Site;

In LFG samples, concentrations of several VOCs, including benzene, ethylbenzene,

PCE, and vinyl chloride, are at or above residential and/or commercial/industrial ESLs at

the Site; and

Methane and hydrogen sulfide were also detected in LFG at significant concentrations.

1.5.4 Human Health Risk Assessment

Based on the laboratory analytical results obtained from the investigations conducted by

Langan, a human health risk assessment was prepared (Langan, 2014e). The technical

approach for the risk assessment consisted of the following basic steps: data analysis and

identification of contaminants of potential concern (COPCs), exposure assessment, toxicity

assessment, and risk characterization, which included an assessment of the uncertainty

associated with each stage of the risk assessment process. The risk assessment used

reasonable maximum exposure point soil and LFG concentrations of COPCs to derive

exposures and risks to potentially exposed human populations for all complete or potentially

complete exposure pathways. The risk assessment found that a complete or potentially

complete pathway for direct groundwater exposure to potential receptors did not exist at the

Site. Incomplete pathways are not relevant to human health risks and were therefore excluded

from the risk assessment.

The potential receptor populations and potential exposure pathways identified during the

evaluation included:

Groundskeepers – Potential exposure pathways include incidental ingestion of soil,

dermal exposure to soil, and inhalation of ambient vapor and fugitive dust.






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Construction Workers - Proper personal protective equipment (PPE) would preclude

exposure of construction workers; however, an evaluation based on potential

construction worker exposures to soil was nonetheless conducted.

Future Residents – Potential exposure pathways include exposure to volatile vapors

from subsurface media that infiltrate the hypothetical buildings into the interior space

through cracks in the slab foundation.

Indoor Commercial Workers – Potential exposure pathways include exposure to volatile

vapors from subsurface media that infiltrate the hypothetical buildings into the interior

space through cracks in the slab foundation.

Shoppers and Other Visitors – Potential exposure pathways include exposure to volatile

vapors from subsurface media that infiltrate the hypothetical buildings into the interior

space through cracks in the slab foundation. Though shoppers and other visitors may

be present on-site on a variable basis, variable or intermittent exposure scenarios were

not quantitatively evaluated because the evaluation of the indoor commercial worker

scenario is protective of these receptors.

The results of the human health risk assessment indicate that:

Under baseline conditions and without active soil vapor/LFG controls, no unacceptable

cancer and non-cancer risks are posed to the groundskeepers, indoor commercial

workers, and construction workers;

Under baseline conditions and without active soil vapor/LFG controls, inhalation of

volatile COPCs from groundwater for the commercial worker scenario results in

incremental human health risks (1E-06 to 6E-07) that were well within the government-

accepted human risk management range risks (i.e. 1E-06 to 1E-04) for such workers.

The hazard index (HI) was below the threshold level of 1, and TCE concentrations in

indoor air are below the short term action level for residential exposure.

For future residents, inhalation of volatile constituents in the interior space of a future

apartment complex without a sub-slab vapor intrusion mitigation including a vapor

barrier also results in carcinogenic risk (5E-06) within the government-accepted risk

management range, but the carcinogenic risks were higher than those for the

commercial workers. The HI for the apartment resident scenario was below the target






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HI of 1, indicating that adverse non-cancer effects are not anticipated. Modeled TCE

concentrations in indoor air are below the short term action level for residential

exposure.

Though the risk assessment indicates that no active soil gas/LFG remediation is required to

mitigate unacceptable risks to the groundskeeper, indoor commercial worker, or construction

worker in any of the parcels, active measures would be advisable to reduce the human health

risks for apartment residents in Parcel 4. To be consistent in providing protection in all parcels

and to add further protective measures for all receptors, Langan recommended the following

remediation and mitigation measures for all parcels in the proposed development to reduce

potential health risks to construction workers and future Site occupants (including

groundskeepers, indoor commercial workers, and residents):

Replacement and enhancement of the existing LFG system at the Site to provide a

more robust remediation system to actively extract LFG from the Site to the existing

gas-to-energy plant for beneficial reuse and reverse the flux of LFG away from building

underslab areas and towards the LFG extraction wells. Construction of a landfill gas

mitigation system (LFGMS) will also address methane and hydrogen sulfide in LFG by

actively removing the LFG from the refuse beneath the development and thermally

destroying the LFG. While odor is not a human health risk issue, it poses the possibility

of unacceptable impacts to human receptors;

Construction of building control systems for LFG (i.e., LFGMS), which will further

mitigate the potential for vapor intrusion by providing a preferential horizontal pathway

to mitigate LFG that may otherwise accumulate at sub-slab areas, in addition to a vapor

barrier membrane (VBM) that would further limit the intrusion of LFG into building

interiors.

Limiting residential construction land uses to areas located above open-air podium level

garages or above at least one level of enclosed retail space; and

Implementation of institutional controls (i.e., deed restrictions) at the Site, restricting the

use of on-site groundwater (i.e., prohibiting the use of on-site groundwater for potable

purposes).






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1.6 Feasibility Study of Groundwater Alternatives

The RWQCB, in a letter dated 23 February 2015, requested preparation of a feasibility study

(FS) of groundwater remediation alternatives to address VOCs in groundwater. The RWQCB

specifically requested that the FS focus on the potential risks from intrusion of groundwater

contaminants from within the VOC Plume into indoor spaces within the future development.

Langan submitted the Feasibility Study of Groundwater Remedial Alternatives (Langan, 2015d),

and the RWQCB concurred with the FS in a letter dated 23 July 2015.

The FS included preparation of a groundwater conceptual site model to describe the history,

source, fate, and potential transport of VOCs within the VOC Plume and to support the

establishment of remedial goals for the VOC Plume. The FS noted that the VOC Plume has

been limited to the northeastern portion of Parcel 4 and southwestern portion of Parcel 3/6

since groundwater data collection began in 1988 and that the extent of the plume has been

stable for at least the past 27 years (Langan, 2015d). As described in the FS, the primary source

of VOCs in the VOC Plume is likely groundwater contact with the refuse beneath the Parcel 4

area. Within Parcel 4, the groundwater table elevation is between approximately 5 and 15 feet

above the bottom of the refuse layer resulting in groundwater contact with refuse. The FS

noted geochemical conditions (low dissolved oxygen and low nitrate concentrations) are

conducive to naturally-occurring anaerobic biodegradation via the reductive dechlorination

pathway. Elevated chemical oxidant demand (COD), which appears to be a result of contact

between refuse and groundwater, appears to provide a long-term source of degradable organic

carbon in the groundwater sufficient to sustain reductive dechlorination. VOC constituents and

concentration trends within the VOC Plume are indicative of an active reductive dechlorination

pathway, including the presence of TCE and daughter products of TCE, including cis-1,2-DCE

and vinyl chloride (Langan, 2015d).

The FS proposed the establishment of groundwater remediation goals based on human health

risk from potential intrusion of VOCs from groundwater into future indoor spaces within Parcel

4 and Parcel 3/6 above the VOC Plume. Risk-based goals, rather than drinking water standards

(i.e., Maximum Contaminant Levels or MCLs) were determined to be appropriate because the

groundwater at the Site is not a potential source of drinking water based on elevated total

dissolved solids (TDS) concentrations exceeding the TDS criterion established in California that

defines a potential source of drinking water (TDS greater than 3,000 milligrams per liter).

Additionally, the Site location near the Bay-margin would likely induce saltwater intrusion from






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the Bay and further increase groundwater salinity (i.e., TDS) if pumping of groundwater for

water supply were to occur. The Johnson and Ettinger (J&E) infinite source groundwater

advanced (GW-ADV) model (Version 3.1, February 2004) was used to evaluate human health

risks associated with groundwater potential vapor intrusion of VOCs from groundwater to

potential residential receptors. The model was used to estimate risk-based groundwater

concentrations based on a residential cancer risk of 1E-06 or systemic risk corresponding to a

hazard quotient (HQ) of 1.

Based on the human health risk assessment, as described in Section 1.5, TCE and vinyl

chloride were the two compounds considered in the risk evaluation. The GW-ADV model

assumed a depth to groundwater based on the median depth to water measured at wells

within Parcel 4 (25.25 feet). The model assumed a landfill cover/cap thickness based on the

current median cover/cap thickness observed in borings within Parcel 4 (9 feet). The model

assumed the subsurface material beneath the landfill cover/cap and the top of the groundwater

table is refuse. Based on site-specific boring log and test pit reports, the GW-ADV model

assumed the following soil types in the risk model:

Refuse Layer = Silty Clay Loam (SICL)

Landfill Cover/Cap = Silty Clay (SIC)

These soils represent reasonably conservative estimates of the total effective rate of diffusion

of VOCs vapors through the vadose zone. The GW-ADV model applied the same building

parameter inputs as presented for the baseline human health risk assessment presented in the

Draft SI/ERA and described in Section 1.5. The default RWQCB exposure parameters for

residential exposures were applied in the GW-ADV model, as presented in the Draft SI/ERA.

Toxicity factors used were consistent with the ESLs for each compound, as presented in the

Draft SI/ERA (Langan, 2014e).

In addition to modeling diffusion of vapors through the vadose zone, the GW-ADV model used

to establish groundwater remediation objectives considered two additional site-specific factors.

First, the GW-ADV model considered the mitigation effect of the proposed vapor barrier

membrane (VBM), which is a component of the LFGMS described in Section 1.5. The VBM

was modeled as a 60-mil (0.15 cm) layer using chemical permeability data provided by CETCO,

the manufacturer of Liquid Boot. Second, the GW-ADV model result was calibrated based on

actual soil gas concentrations (i.e. concentrations present within the landfill gas) present above

the VOC groundwater plume. The FS describes an evaluation of concentrations of TCE and






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vinyl chloride in groundwater samples collected from groundwater wells within the footprint of

the VOC Plume and comparison of the concentrations with soil gas concentrations from soil

gas probes within the footprint of the VOC Plume. Langan predicted soil gas concentrations

based on equilibrium partitioning (Henry’s Law) between soil gas and groundwater, using 2014

concentrations of TCE and vinyl chloride in groundwater and soil gas.

Based on the methodology described above, the GW-ADV model was performed for TCE and

vinyl chloride under residential exposure conditions. The result was a calculation of TCE and

vinyl chloride concentrations in groundwater corresponding to the more restrictive of either a

1E-06 cancer risk or HQ of 1 for residential land use. The modeled target values included the

following:

TCE: 59,600 micrograms per liter (g/L)

Vinyl Chloride: 442g/L

The FS noted that the modeled target values were significantly higher than actual

concentrations on TCE and vinyl chloride in the VOC Plume. For TCE, the risk-based target

concentration was several orders of magnitude greater than actual concentrations found in

groundwater and was well above a concentration that can be reasonably expected to exist

within the VOC Plume. For this reason, the FS did not establish a remedial goal for TCE. For

vinyl chloride, the FS established the risk-based target concentration as the remedial goal. The

FS established the following remedial goals for the VOC Plume:

1. Maintain or reduce vinyl chloride concentration in groundwater at or below 442 µg/L;

and

2. Demonstrate long-term stability or decreasing trend in TCE and vinyl chloride

concentrations at wells G-10, G-18, and G-19.

A range of remedial technologies was considered in the FS for reduction of groundwater vinyl

chloride concentrations within Parcel 3/6 and Parcel 4, consistent with the remedial goals.

Technologies that were screened included: No Action, Monitored Natural Attenuation (MNA),

Chemical Oxidation, Bioaugmentation, Bioaugmentation with Electron Donor, Zero Valent Iron

(ZVI) with Electron Donor, Air Sparging with Soil Vapor Extraction, and Vacuum Enhanced

Pumping. These remedial technologies were evaluated based on the following criteria:






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technical effectiveness, implementability, remedial time frame and relative cost range. These

criteria were ranked as ‘low’, ‘medium’, and ‘high’, as presented in the FS. As part of this

evaluation, a 600 foot long, 60 foot wide treatment area was assumed with a target depth of 15

feet in the saturated zone. The treatment area consisted of areas with elevated or increasing

vinyl chloride concentrations and included the area between monitoring wells G-19 and G-18.

As a result of the alternative screening, the FS eliminated the following alternatives from

further consideration: No Action, Chemical Oxidation, and Air Sparging with Soil Vapor

Extraction. The FS included a detailed evaluation of the remaining remediation technologies:

MNA

Bioaugmentation

Bioaugmentation with Electron Donor

ZVI with Electron Donor

Vacuum Enhanced Pumping

The FS noted that all five of the evaluated remediation technologies were expected to meet the

established remedial goals and could be implemented in a way that was not expected to

interfere with planned development. Based on the remedial alternative evaluation presented in

the FS, MNA was selected to be the preferred remedial alternative for implementation of VOC

Plume remediation. The FS noted several factors that supported the selection of MNA,

including:

1. MNA is already meeting groundwater remedial goals and is expected to continue to meet

these remedial goals in the future;

2. The size of the VOC Plume is stable and has been stable for 27 years;

3. Reductive dechlorination is occurring in the groundwater;

4. Groundwater field and laboratory analytical geochemical parameters conducive to reductive

dechlorination were detected within the VOC Plume;

5. Refuse appears to act as a source of electron donor and thus can continue to sustain

reductive dechlorination of the groundwater VOC plume;






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6. The Proposed LFG System, described in Section 1.5, would result in continued decreases in

VOC concentrations in soil gas within the refuse and will therefore help to mitigate

groundwater VOC impacts; and

7. Aspects of site development will serve to reduce infiltration rates into the landfill, further

reducing leachate production from current low levels. Although leachate is not considered

to be the primary source of VOCs in the VOC Plume, the above items would reduce

potential impacts of leachate on the groundwater.

The FS established the approach for implementation of the MNA alternative, including

monitoring to be performed quarterly for the first two years once the on-site construction has

started, then semiannually for next three years, and annually thereafter. Monitoring parameters

established in the FS included field groundwater monitoring parameters, VOC concentrations,

dissolved gases including concentration, ethene and ethane, geochemical data, total organic

carbon (TOC), and Dehalococcoides (DHC) cell density.

The FS included an iterative contingency approach to be taken to further evaluate, and if

necessary, take action should any increasing VOC concentrations occur during implementation

of the MNA alternative. The steps included review of sampling methodology, confirmation

groundwater monitoring, review of the groundwater conceptual site model, review of the risk

model, and an evaluation of whether MNA remains the appropriate remedial measure for the

VOC Plume. As described in the FS, should MNA not remain the appropriate remedial

alternative, consideration would be given to: 1) an active remediation alternative evaluated in

the FS, and/or 2) adjustment/optimization of existing mitigation systems or selection of

additional mitigation measures.

2.0 GEOLOGY AND HYDROGEOLOGICAL INFORMATION

This section presents a description of the Site geology and hydrogeology based on the results

of multiple phases of investigations and periodic monitoring completed by Langan and others.

Furthermore, the existing soil cover over the refuse was evaluated for suitability to continue to

serve as the final landfill cover per applicable environmental regulations.

Current California Code of Regulations Title 27 regulations require a "prescriptive" cover design,

one that is established by regulation and intended for use in the closure of landfills regulated

under Title 27. The prescriptive cover, as outlined in Title 27, §21090(a)(1-3), contains:






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A foundation layer of not less than 2 feet of appropriate materials. However, Title 27

Section 21090 allows for a lesser thickness, if the ultimate land use will not affect the

structural integrity of the final soil cover. The foundation layer materials may be soil,

contaminated soil, incinerator ash, or other waste materials, provided that such

materials have appropriate engineering properties to be used for a foundation layer.

Low permeability layer not less than 1 foot thick and of hydraulic conductivity not more

than 1E-6 centimeters per second (cm/sec).

Erosion resistant layer (cover soil) not less than 1 foot thick capable of sustaining

vegetation and resistant to wind, raindrop impact, or runoff or mechanically resistant.

The landfill cover, refuse and subsurface conditions beneath the landfill are discussed in the

following subsections.

2.1 Subsurface Conditions

The Site is underlain by varying thicknesses (3 to 35 feet) of cover soil, an artificial fill which

consists of mixed sand, gravel, clay and silt layers (Langan, 2014c and 2014e). Within the cover

soil, a clay soil layer with varying amounts of sand and gravel content was encountered in most

of the borings and test pits. This material, which varies in thickness up to 7 feet throughout the

Site, consists of dark brown stiff clay and was likely used as the low permeability layer of the

previously constructed final cover. The bottom of the low permeability layer generally marks the

top of the refuse layer, which consists of mixed refuse items, including wood, paper, plastic,

ceramics, glass, metals, and cloth in a matrix of soil. The lower one foot of the clay layer (where

it is at least two feet thick) and upper one foot of the refuse layer was likely the foundation

layer during original final cover construction. As discussed above, Title 27 allows for foundation

layer materials to be soil, contaminated soil, incinerator ash, or other waste materials, provided

that such materials have appropriate engineering properties to be used for a foundation layer.

The upper few feet of the refuse unit is generally mixed in with significant soil and likely was

stable and non-yielding to allow for compaction of the clay material above the refuse.

Our estimate of the depth and thickness, based on Langan investigations, of the soil cover, low

permeability and foundation layers are presented in Table 2. In some locations, Borings B-16,

B-23, B-37, B-38 and B-39, the low permeability layer was not observed in the borings; it may

be that the layer is present but not sampled. Additionally, other areas such as near test pit TP-






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1, sufficient cover soil over the low permeability layer was not observed. The presence or lack

of the low permeability layer and cover soil layer in these locations will be further evaluated as

part of a future final geotechnical investigation. Additionally, in areas where proposed utilities

or roadway excavations need to extend below the existing low permeability layer, the landfill

cover including low permeability layer will be designed and repaired to accommodate these

construction details and provide a continuous landfill cover across the Site.

Table 2

Summary of Thickness of Cover Soil, Low Permeability Layer, and Refuse

Boring

No.

Parcel

Number

Approx

thickness

of cover

soil (feet)

Approx

thickness of

low

permeability

layer (feet)

Approx

thickness of

foundation

layer (feet)

Approx

thickness

of refuse

(feet)

Comments

1 2 2 1 2 30

2A 1 4.5 1 2 59.5

4 4 4 1.5 2 31.5 Top of refuse layer

likely used as

foundation layer

5 4 3 1 2 10.5

6 4 10 1 2 19 Top of refuse layer

likely used as

foundation layer

7 4 5.5 1 2 24

8 3 29 1 5 >10

9 3 7 1 2 >1

10 3 18 1 2 >5

11 3 18 1 2 >4

12 3 27 1 2 >6

13 3 34 1 2 >5 Top of refuse layer

likely used as

foundation layer

14 3 7.5 1 2 >0.5

15 3 28 1 2 >5

16 4 4.5 0 2 >30.5 Low Permeability

Layer not

observed

17 4 4 1 2 >24

18 4 4 1 2 >20


likely used as

foundation layer

20 4 4 1 2 >29






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Boring

No.

Parcel

Number

Approx

thickness

of cover

soil (feet)

Approx

thickness of

low

permeability

layer (feet)

Approx

thickness of

foundation

layer (feet)

Approx

thickness

of refuse

(feet)

Comments


likely used as

foundation layer

22 4 5 1 2 >28

23 4 4 0 2 >32.5 Low Permeability

Layer not

observed over

refuse and top of

refuse layer likely

used as foundation

layer

24 4 12 1 2 >1


likely used as

foundation layer


likely used as

foundation layer

27 1 15 1 2 >6

28 1 6.5 1 2 >4.5

29 1 7.5 1 2 >5.5

30 1 13 1 2 >5

31 1 15 1 2 >6

32 1 2.5 1 2 >8.5

33 2 3.5 1 2 >4 Top of refuse layer

likely used as

foundation layer

34 2 5 1 2 >3

35 2 5 1.5 2 >2.5 Top of refuse layer

likely used as

foundation layer

36 2 6 1 2 >2

37 2 10 0.5 2 >4 0.5 foot thick Low

Permeability Layer

observed over

refuse and top of

refuse layer likely

used as foundation

layer

38 2 6 0 2 >4 Low Permeability

Layer not

observed over

refuse






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Boring

No.

Parcel

Number

Approx

thickness

of cover

soil (feet)

Approx

thickness of

low

permeability

layer (feet)

Approx

thickness of

foundation

layer (feet)

Approx

thickness

of refuse

(feet)

Comments

39 2 7 0.5 2 >2.5 0.5 foot thick Low

Permeability Layer

observed over

refuse and top of

refuse layer likely

used as foundation

layer

Beneath the soil cover unit discussed above is the refuse unit, which varies between

approximately 10 and 60 feet thick. The refuse is underlain by alluvial deposits consisting

predominately of clay and sandy clay layers with occasional interbedded layers of sand and silt.

These sand layers extend over much of the Site; however, they are laterally and vertically

discontinuous which is typical for alluvial deposits. The boring logs and cross sections illustrate

the discontinuous nature of the sand lenses. The soil stratigraphy beneath the refuse will be

further evaluated as part of future geotechnical investigations. Boring logs and idealized

subsurface cross-sections based on our investigations and others are provided in Appendix G.

Groundwater has been observed between approximately 18.5 and 52 feet bgs at the Site

during drilling, corresponding to between elevation (el.) -10 and el. 7 (North American Datum of

1983 [NAD83]/ North American Vertical Datum 1988 [NAVD 88]). Approximate depths to

groundwater and elevations are as follows:

Table 3

Summary of Depth to Groundwater

Parcel Approximate Depth to

Groundwater (feet)1

Approximate Groundwater

Elevation (feet)2

Parcel 1/1NW 52 0

Parcel 2 40 -8

Parcel 3/6 50 to 65 (estimated) 0 (estimated)

Parcel 4 18.5 to 32 -10 to 7

Approximate depth to groundwater recorded during drilling and may not represent stabilized levels.

All elevations reference NAD83/NAVD88.






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Groundwater elevations recorded in our investigations (Langan, 2014c and 2014e) are generally

consistent with the historically measured groundwater elevations. Groundwater monitoring

conducted by Golder Associates in February 2014 measured the groundwater level at the Site

between about el. -4 to el. 43 (Golder, 2014b). The direction of groundwater flow is to the north-

northeast. A groundwater elevation contour map for the Site, based on 24 February 2014

groundwater monitoring data by Golder, is provided in Appendix A, on Figure 2 - Piezometric

Surface Contour Map.

Based on the available groundwater data from previous monitoring at the Site, the groundwater

elevations are generally in or within 10 feet of the bottom portion of the refuse unit. This

suggests that a distinct leachate layer within the refuse unit does not likely exist at a higher

elevation than the regional groundwater elevation. Furthermore, given the apparent lack of

hydraulic head between leachate and groundwater, it is unlikely that contaminants in the first-

encountered groundwater level will migrate vertically to impact underlying aquifers. The

geologic cross sections in Appendix G illustrate similar groundwater elevations from wells

monitored by Golder from July 2013 as those measured in soil borings drilled in the waste

units, which supports an apparent lack of hydraulic head between leachate and groundwater

beneath the Site.

2.2 Hydrological Information

The Site is tributary to the San Tomas Aquino Creek and the Guadalupe River. A brief

description of each waterway and its watershed, as provided by the Santa Clara Valley Urban

Runoff Pollution Protection Program (SCVURPPP), is as follows:

San Tomas Aquino Creek - The San Tomas Aquino Creek watershed covers an area of

approximately 45 square miles. The Creek originates in the forested foothills of the

Santa Cruz Mountains flowing in a northern direction through the cities of Campbell and

Santa Clara, into the Guadalupe Slough, and finally into the Lower South San Francisco

Bay. The major tributaries to San Tomas Aquino Creek include Saratoga, Wildcat, Smith

and Vasona Creeks. Most of the San Tomas Aquino watershed is developed as high-

density residential neighborhoods, with additional areas developed for commercial and

industrial uses. The majority of the San Tomas Aquino Creek channel has been

Golder report references elevation in feet mean sea level (MSL), assumed to be National Geodetic

Vertical Datum of 1929 (NGVD29). Elevations provided herein reference NAD83/NAVD 88.






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modified and lined with concrete (from the Smith Creek confluence in the upper

reaches downstream to Highway 101).

Guadalupe River - The Guadalupe River watershed covers an area of approximately 171

square miles. The headwaters drain from the eastern Santa Cruz Mountains near the

summit of Loma Prieta in heavily forested unincorporated county land with pockets of

low-density residential developments. The Guadalupe River actually begins on the valley

floor at the confluence of Alamitos Creek and Guadalupe Creek, just downstream of

Coleman Road in San Jose. From here it flows north, approximately 14 miles until it

flows into the Lower South San Francisco Bay via Alviso Slough. The upper watershed

is characterized by heavily forested areas with pockets of scattered residential areas.

Residential density gradually increases to high density on the valley floor. Commercial

development is focused along major surface streets. Industrial developments are

located closer to the Bay, primarily downstream of the El Camino Real crossing. Six

major reservoirs exist in the watershed: Calero Reservoir on Calero Creek, Guadalupe

Reservoir on Guadalupe Creek, Almaden Reservoir on Alamitos Creek, Vasona

Reservoir, Lexington Reservoir, and Lake Elsman on Los Gatos Creek.

The climate of the City of Santa Clara is characterized as dry-summer subtropical (often referred

to as Mediterranean), with cool wet winters and relatively warmer dry summers. The mean

annual precipitation in the vicinity of Santa Clara is approximately 15 inches (95 percent [%] of

which falls between October and April) per the 2007 Santa Clara County Drainage Manual

(SCCDM). This value is typical of Santa Clara County east of the coastal range, however, the

Site can experience a wide range of annual precipitation.

Due to the nature of the existing topography and drainage infrastructure, the four parcels along

with the tributary off-site areas have been divided into four distinct sub-watersheds referenced

herein as the San Tomas, East Basin, Eastside Channel and Basin Direct. Note that the East

Basin, Eastside Channel and Basin Direct are tributary to the Guadalupe River via the Eastside

Retention Basin and Pump Station.

San Tomas – The San Tomas sub-watershed includes the areas from Parcel 4 that drain

directly to the San Tomas Aquino Creek via existing outfalls. The Golf Course Pump

Station also conveys runoff to the Creek from areas of Parcel 4 and off-site areas from

Stars and Stripes Drive.






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East Basin – The East Basin sub-watershed includes areas from Parcels 1/NW, 2, 3/6

and 4 along with the off-site areas that drain to the west ditch/channel and ultimately to

the Eastside Retention Basin.

Eastside Channel – The East Side Channel sub-watershed includes areas from Parcels 1

and 2 along with the off-site areas that drain to the Eastside Retention Basin via the

existing Eastside Drainage Channel.

Basin Direct – The Basin Direct sub-watershed includes areas that surface flow directly

to the Eastside Retention Basin.

Within these sub-watersheds, the existing drainage characteristics for each of the Parcels are

as follows:

Parcel 1/1NW – The 49.6 acre Parcel 1/1NW includes open space, a BMX facility, a LFG

recovery facility, access roads, the Eastside Retention Basin, and City operated pump

stations for sanitary sewer and stormwater. The existing surface cover consists of

shrub land, gravel, pavement and open water. The surface water hydrology includes

overland flow and piped conveyance with surface runoff tributary to the Eastside

Retention Basin/Guadalupe River.

Parcel 2 – The 60.9 acre Parcel 2 includes golf course open space, golf cart paths and

access roads. The existing surface cover consists of golf course features (grass, sand

traps, paved golf cart paths), shrub land, gravel and pavement. The surface water

hydrology includes overland flow and piped conveyance systems with surface runoff

tributary to the Eastside Retention Basin/Guadalupe River.

Parcel 3/6 – The 34.9 acre Parcel 3/6 includes golf course open space, golf cart paths

and access roads. Additional fill was placed over the landfill cover creating an elevated

ridge within the center of the site. The existing surface cover consists of golf course

features (grass, sand traps, paved golf cart paths), shrub land, gravel and pavement.

The surface water hydrology includes overland flow and piped conveyance systems

with surface runoff tributary to the Eastside Retention Basin/Guadalupe River. There is

an open depressed area along the toe of the southern slope of the landfill that collects

surface water runoff from both Parcel 3/6 and Parcel 4. This area is utilized as a utility

corridor for the City’s recycled water and sanitary sewer systems.






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Parcel 4 – The 86.6 acre Parcel 4 includes golf course open space, golf cart paths, the

golf course driving range, several buildings, access roads, parking lots and a

maintenance area. The existing surface cover consists of golf course features (grass,

sand traps, paved golf cart paths), shrub land, open water ponds, gravel, paved areas

and building structures. The northern portion of the site drains to the open depressed

area along the toe of the northern slope of the landfill on Parcel 3/6 and the piped

conveyance system within the adjacent property to the north, the eastern portion of the

site drains to a ditch along the adjacent railroad right-of-way (located adjacent to

Lafayette Street), the western portion of the site drains directly to the San Tomas Creek

gravity outfalls and the southern portion of the site drains to the piped conveyance

system in Stars and Stripes Drive. In addition, there is a lined open water pond located

within Parcel 4.

Parcel 5 – The 8.0 acre Parcel 5 includes parking lots and some open space areas. The

existing surface cover consists of pavement and vegetated landscape. The site drains to

on-site catch basins that are connected to the existing storm drainage system in Stars

and Stripes Drive. This storm drain system is tributary to the Golf Course Club House

Pump Station.

3.0 SOIL AND WASTE MANAGEMENT

Site development will require excavating, grading, and conditioning (i.e., soil improvement) of

native material, cover material, and, to a very limited extent, landfill debris within the refuse

unit. The quantity of waste to be handled will be the minimum necessary to construct the

infrastructure, buildings, site improvements, etc. and achieve final grades to support the

Project. A final waste management plan will be developed for the Project to outline proper soil

and landfill debris handling procedures and health and safety requirements (Appendix H). This

waste management plan will help minimize worker and public exposure to toxic materials

during construction. An overview of waste management during construction, nuisance control

measures, and health and safety considerations, are included in the Sections below.

3.1 Waste Management During Construction

Waste management during construction will include waste segregation and characterization,

dust monitoring and control, air monitoring, equipment decontamination, storm water pollution

control, and implementation of a health and safety program. Construction activities that may






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require waste management include grading, excavation for utilities, and possibly pile

installation. An environmental technician who is a Certified Hazardous Waste Worker (per 29

CFR 1910.120) will monitor construction activities to facilitate and document compliance with

the specified waste management procedures, identify potentially contaminated soil and landfill

debris, oversee soil and landfill debris segregation, monitor dust and vapor conditions, and

sample soil for characterization as necessary for off-site landfill disposal profiling (see Appendix

H). Waste handling will be performed in accordance with a Site-specific Health and Safety Plan

(HASP), to be prepared by a certified industrial hygienist (CIH) that represents the general

contractor. General health and safety requirements are discussed in Section 3.3.

The total estimated quantity of waste (including cover soil and, to a very limited extent, the low

permeability layer and refuse) to be excavated will be established as part of final design of the

Project. Based on the preliminary design, the estimated quantity of refuse, as part of the

overall waste generation for the Project, is approximately 100,000 CY. To construct the

trenches for portions of the gravity utilities, excavations are expected to extend into the waste

unit; piping that extends beneath the cap will be water/gas tight to limit leakage into the landfill

refuse and LFG entering into the piping. The design intent is to leave the low permeability layer

and refuse in place to the greatest extent possible and to only disturb it in locations requiring a

deeper excavation, such as main utility trenches.

The cover soil, low permeability layer and refuse will need to be handled and disposed of

properly. Excavated refuse will be monitored for the presence of hazardous or other

unacceptable materials. Refuse will most likely be excavated using conventional earth-moving

equipment such as loaders, backhoes, excavators, or bulldozers. Refuse will be loaded into

trucks and hauled to a staging area to be located on-site for profiling and eventual on-site or off-

site disposal. If any excavated refuse is re-disposed on-site, the disposal of such refuse will

conform to Title 27 requirements and additional applicable regulatory requirements. These

materials will be separated and cordoned off to prevent unauthorized access. A licensed

contractor will be hired to handle the material, including containerization, if necessary, and

transport to an appropriately permitted disposal facility.






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3.2 Nuisance Control Measures

3.2.1 Dust, Litter, and Vectors

Excavating refuse has the potential to create nuisances, such as dust, litter, vectors (as defined

by CCR, Title 27, §20164), and odors. These nuisances could impact adjacent properties. In

addition, toxic materials may be encountered during excavation, which have the potential to

result in worker exposure. LFG could be released or collect in excavations, creating potentially

harmful or explosive conditions. The following project elements address potential nuisances,

hazardous materials, and LFG:

Excavation of refuse will be performed in accordance with a Health and Safety Program

designed to minimize impacts from dust, odor, and other nuisances, and assure the

refuse is handled in a safe and environmentally responsible manner. A site-specific

HASP, to be completed by a CIH on behalf of the general contractor, will address

procedures for monitoring LFG and handling hazardous materials.

During refuse excavation and relocation, the worksite will be monitored for dust, odor,

or other nuisances in accordance with general landfill construction practices and the

HASP. Dust will be controlled by application of a water spray. The amount of water

applied will be the minimum amount required to control dust without creating run-off.

At the end of the working day, exposed refuse will be covered with soil or an alternative

material, such as a geosynthetic blanket, (i.e., interim cover). Covering the refuse at the

end of the working day will control odors, litter, and other potential nuisances. Areas at

final grade will have final cover placed over them.

Odors, should they occur, will be controlled by application of a deodorant, masking

agent, neutralizing agent, or lime, and an interim landfill cover at the end of each

working day. An odor management plan is included in Appendix I.

A "Project Contact" will be designated who will be responsible for responding to local

complaints about dust, odors, or other nuisances associated with the refuse excavation

and re-grading operations. The telephone number of the Project Contact will be posted

at the construction Site and included in the information distributed as part of the

project's outreach program. The Project Contact will determine the source of project-

related nuisances and will coordinate reasonable measures to alleviate the nuisance.






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As discussed in Section 1.4, the Landfill has potential for LFG generation. During

excavation activities, excavation areas will be monitored using a hand-held instrument

calibrated to measure combustible gases (including methane), oxygen, hydrogen sulfide,

and VOCs. Smoking and open flames will be prohibited in excavation areas. Workers

will not be allowed to enter excavated areas, where LFG may accumulate, without prior

monitoring for LFG. If LFG is present, workers will be required to wear appropriate

safety equipment, including respirators if necessary.

3.2.2 Traffic Control

To minimize traffic disruptions during the work, traffic flow into, on, and out of the Site shall be

managed by the general contractor and controlled to minimize the following:

Interference and safety problems with traffic on adjacent public streets or roads,

On-site safety hazards, and

Interference with Site operations.

3.3 Health and Safety Program

During construction of the proposed development, there may be the potential for workers at

the Site, nearby residents, and/or pedestrians, to be exposed to on-site soil or contaminants.

The routes of potential exposure to the Site contaminants (TPH, VOC, and/or metals) could be

through three pathways: (1) dermal (skin) contact with the soil, (2) inhalation of ambient vapor

and fugitive dust, and (3) incidental ingestion of the soil. The highest potential for human

exposure to the contaminants in the soil will be during waste handling operations. Because on-

site materials may contain contaminants in excess of the regulatory guidelines, proper health

and safety procedures, and warning requirements will be implemented during construction.

The potential health risk to on-site construction workers and the public will be minimized by

developing a comprehensive Health and Safety Program. The general contractor shall be

responsible for health and safety conditions related to the work to be performed. Contractor

employees, subcontractor employees, and others who enter the Site must adhere to the

provisions of the contractor Health and Safety Program. All applicable federal, state, and local

regulations and codes relating to health and safety shall be adhered to by the contractor

employees, subcontractor employees, and others who enter the Site.






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The Health and Safety Program will include development of a HASP, including an Air Monitoring

Plan and a Dust Management Plan. These plans will be prepared by a CIH that represents the

general contractor. The general contractor will be responsible for establishing and maintaining

proper health and safety procedures to minimize worker and public exposure to Site

contaminants during construction. The HASP will describe the health and safety training

requirements (i.e., training in accordance with Section 1910.120 of 29 Code of Federal

Regulations [HAZWOPER training]), specific personal hygiene requirements, and monitoring

equipment that will be used during construction. These requirements will protect and verify

the health and safety of the construction workers and the general public; as such, the HASP

will include provisions for Site security and signage. The HASP will also include an emergency

notification list.

A Site Health and Safety Officer (HSO), employed by the general contractor, will be on-site

during construction activities that may require waste management (grading, soil segregation,

soil compaction, excavation for utilities, soil improvement, foundation installation, paving, and

landscaping) to facilitate and document that all health and safety measures are maintained. The

HSO will have authority to direct and stop (if necessary) all construction activities in accordance

with the HASP.

4.0 SITE DEMOLITION AND PREPARATION

Site demolition and preparation will include removal of all existing structures, foundations,

slabs, pavements, and underground utilities within the footprint of the planned development

(see Appendix D for the preliminary design drawings). Existing pavement and foundations will

be removed to expose underlying aggregate base. Underground utilities will be removed to the

service connections and properly capped or plugged. Where existing, inactive, utilities will not

interfere with the planned construction they may be abandoned in-place. All existing utilities

abandoned in place will be filled with lean concrete or cement grout to the limits of the project.

Voids resulting from demolition activities and subgrade preparation above the low permeability

layer will be properly backfilled. All demolition waste materials that cannot be reused or

recycled on-site will be removed from the Site following demolition.

It is anticipated that some components of the existing LFG and LCR systems will be impacted

and that interim measures will be necessary to promote continued effectiveness during

construction (see Appendix A for existing system locations). Additional information on the






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proposed abandonment and replacement of these systems are included in Sections 9.0 and

11.0, respectively. Existing groundwater monitoring wells and LFG monitoring probes shall be

protected during the Site demolition activities (see Appendix A for well locations).

5.0 CONCEPTUAL FOUNDATION

5.1 Structures

A majority of City Center (Phase 1 and Phase 2) portion of the Project within Parcel 4, inclusive

of all buildings, parking garages, plazas and streets, will be a continuous structural slab that is

structurally supported on a deep foundation or ground improvement system that extends

through the cover soil and refuse. For the remainder of the development, the buildings and

parking structures will be supported on a similar deep foundation or ground improvement

system, and the streets, plazas and open space/landscaped areas will be supported on grade.

The structural system for the buildings will include an interstitial space between the first floor

slab and the structural slab. The grading of the streets and plaza areas will be coordinated with

the first floor elevations of the retail, office and parking structures. Residential will be located

above podium parking or first floor retail, thus will not be located on the first floor. Typical

conceptual sections depicting the likely configuration of the foundation system for the various

building types are included in Appendix J.

5.2 Site Settlement Evaluation

As indicated, the Site is underlain by a significant thickness of compressible refuse that will

continue to settle at highly variable rates. Preliminary settlement estimates were estimated

using a model developed by Gibson and Lo (Edil et al., 1990 and Gibson, 1961), which includes

parameters for primary and secondary compression in refuse. The refuse generally consists of

silty clay soil/municipal solid waste, combined with construction debris with high percentages

of wood. Primary compression generally includes the bending, crushing, and reorientation of

landfill material and the movement of finer grained materials into large voids. Settlement

associated with primary compression typically occurs between 1 and 5 years after the initial

application of the load. Secondary compression is associated with landfill settlements that

occur gradually over time. Secondary compression is generally attributable to the physical-

chemical change of the landfill materials, such as corrosion and oxidation, and the biochemical

decomposition of the organic landfill material through anaerobic fermentation and decay. The

majority of secondary compression is typically completed within 50 years after the initial






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application of the load (Sharma and Lewis, 1994). These landfills were closed approximately 20

to 40 years ago; so much of the primary and secondary compression is complete. However,

due to the increased loading from the proposed development, Langan anticipates some future

primary and secondary compression will occur. A detailed settlement analysis will be

performed as part of a final geotechnical investigation for each parcel. Langan preliminarily

estimated refuse settlements for Parcels 1/1NW and 3/6 assuming refuse thicknesses ranging

from 40 to 60 feet. For Parcels 2 and 4, Langan assumed refuse thicknesses ranging from 10

to 40 feet. For all parcels, Langan also estimated refuse settlements which will result from the

addition of 1 foot and 5 feet of new fill. The results of our settlement evaluation are depicted in

Figures 7 and 8 of our Preliminary Geotechnical Investigation Report (Langan, 2014c), which are

included in Appendix J. Because of the heterogeneity of the refuse, it is difficult to accurately

predict the amount of settlement over a given period of time. These estimates will be used as

a guide and may vary significantly. A detailed settlement analysis will be performed as part of a

final geotechnical investigation for each parcel.

On the basis of the currently available data Langan estimate up to about 2 feet of settlement

may occur in Parcels 2 and 4 over the next 30 years. Larger settlements may occur at Parcels

1 and 3/6 due to the thicker and generally younger waste, but will depend on the grading. Piles,

hinged slabs, and settlement vaults would need to be designed to accommodate the estimated

settlement.

Because piles (for lateral capacity) and underground utilities will be designed to accommodate a

set amount of settlement plus a factor of safety, ground surface settlement will be monitored

periodically as part of an overall Site Operation, Monitoring and Maintenance (OM&M) Plan

during the life of the development, and per Title 27 requirements, so mitigation measures can

be implemented if the actual settlement is larger than predicted. Settlement mitigation

measures may include adding fill to restore the lateral capacity of the foundation, and functional

site access. Pumping a light weight material such as Cell-Crete beneath the buildings could be

an alternative to placing fill. Lightweight Cell-Crete can have a unit weight of about 40 to 70

pcf, which is less than typical soil materials and therefore result in less additional settlement

associated with the additional load. Furthermore, Cell-Crete is flowable and self-leveling and

could easily be pumped beneath the building to fill voids and replace the lateral support.

Periodic adjustments to perimeter hinged slabs and other settlement mitigation elements will

also be necessary.






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5.3 Seismic Hazards Analysis

During a major earthquake, strong to violent ground shaking is expected to occur at the project

Site (Langan, 2014c). Strong ground shaking during an earthquake can result in ground failure

such as that associated with soil liquefaction,4 lateral spreading,5 cyclic densification,6

landsliding, or can cause a tsunami. Each of these conditions has been preliminarily evaluated

based on our literature review, field investigation, and analysis, and are discussed below.

5.3.1 Liquefaction

The Site is located within a zone designated with the potential for liquefaction, as identified by

the California Geologic Survey (formerly the California Division of Mines and Geology) in a map

titled, State of California Seismic Hazard Zones, Milpitas Quadrangle, Official Map prepared by

the California Geologic Survey, dated 19 October 2004. Specifically, the map shows the Site is

in an area ‚where historic occurrence of liquefaction, or local geological, geotechnical and

groundwater conditions indicate a potential for permanent ground displacements such that

mitigation as defined in Public Resources Code Section 2693 (c) would be required.‛

We performed our liquefaction analysis in accordance with the State of California Special

Publication 117A, Guidelines for Evaluation and Mitigation of Seismic Hazards in California and

following the procedures presented in the 1996 NCEER and the 1998 NCEER/NSF workshops

on the Evaluation of Liquefaction Resistance of Soils (Youd and Idriss, 2001). The NCEER

methods are updates of the simplified procedures developed by Seed et al. (1971).

To estimate volumetric strain and associated liquefaction-induced settlement, Langan used the

procedure developed by Tokimatsu and Seed (1987).

Saturated layers of loose to medium dense sand with varying amounts of clay and silt and non-

plastic silt were encountered within and just below the refuse unit in one boring (B-4; see

Appendix G). Our analysis indicates these layers could potentially liquefy and result in

4 Liquefaction is a transformation of soil from a solid to a liquefied state during which saturated soil

temporarily loses strength resulting from the buildup of excess pore water pressure, especially

during earthquake-induced cyclic loading. Soil susceptible to liquefaction includes loose to medium

dense sand and gravel, low-plasticity silt, and some low-plasticity clay deposits. 5 Lateral spreading is a phenomenon in which surficial soil displaces along a shear zone that has

formed within an underlying liquefied layer. Upon reaching mobilization, the surficial blocks are

transported downslope or in the direction of a free face by earthquake and gravitational forces. 6 Cyclic densification is a phenomenon in which non-saturated, cohesionless soil is densified by

earthquake vibrations, causing ground-surface settlement.






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seismically induced settlement on the order of 4-inches. However, potentially liquefiable soil

was not encountered in the other borings. Therefore, Langan conclude the potential for soil

liquefaction is likely during a major earthquake. However, it appears that the potential for

liquefaction will be limited to isolated areas and should not be a widespread concern.

5.3.2 Seismic Densification

Seismic densification of non-saturated, cohesionless soil following a major earthquake was

analyzed using the procedure outlined by Tokimatsu and Seed (1987), titled ‚Simplified

Procedure for the Evaluation of Settlements in Clean Sand‛. The borings indicate the sand

deposits above the design groundwater level are generally sufficiently dense and/or clayey such

that seismic densification is unlikely except in the vicinity of boring B-4. We estimate

settlements associated with seismic densification at boring B-4 could be on the order of 1 to 1-

½ inches.

5.3.3 Lateral Spreading

As discussed in Section 5.3.1, the potential for liquefaction appears to be isolated. Because

there does not appear to be a continuous potentially liquefiable layer near the slope faces of the

former Landfill, Langan conclude the potential for lateral spreading is low.

5.3.4 Surface Faulting

We evaluated the risk of surface faulting at the Site associated with active or potentially active

fault traces. Historically, ground surface displacements closely follow the traces of geologically

young faults. Based on our study, Langan conclude the site is not within an Earthquake Fault

Zone, as defined by the Alquist-Priolo Earthquake Fault Zoning Act, and no known active or

potentially active faults exist on the Site. In a seismically active area, the remote possibility

exists for future faulting in areas where no faults previously existed; however, Langan conclude

the risk of surface faulting and consequent secondary ground failure is low.

5.3.5 Tsunami

Recent published maps (California Emergency Agency, 2009) indicate the site is not within the

tsunami inundation zone; therefore, Langan conclude the potential risk of inundation from

tsunami to be low for the site.






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5.4 Proposed Foundation Options

We anticipate the Site will undergo significant settlement caused by the decomposition,

consolidation, and compression of the landfill material due to the weight of landfill refuse,

existing cover soil, and new fill and/or structural loads associated with the proposed

development. These processes will result in differential settlement of the ground surface and

the site improvements. To reduce the potential for settlement of proposed buildings, utility

corridors and surface improvements, Langan anticipate the proposed structures can be

supported on spread footings (isolated or continuous) bearing on drill displacement columns

(DDCs) or on deep foundations consisting of drilled auger cast in place (ACIP) piles. These

foundation options will be designed to address the potential for landfill disturbance and

preserve the integrity of the landfill components and the structures built as part of the proposed

development in a manner that is protective of public health and safety and the environment.

These foundation options are discussed in detail in our Preliminary Geotechnical Investigation

Report and summarized in the following subsections.

5.4.1 Spread Footings on DDCs

In areas with relatively thin refuse (40 feet thick or less) and where relatively lightweight

structures are planned, the proposed buildings and surface improvements can be supported on

shallow foundations bearing DDCs. The DDCs will transfer building loads to stronger native soil

below the landfill refuse. This approach would allow for the use of shallow spread footings at

building column locations rather than deep pile foundations.

DDCs are constructed by using a displacement auger to drill a shaft cased to the desired depth.

The soil, refuse, and leachate, if present, would be displaced laterally (up to about 18-inches

depending on the auger diameter) but not vertically. Controlled low strength material (CLSM),

grout or concrete is injected continuously under pressure as the augers are slowly withdrawn,

replacing the soil or refuse displaced by the drilling operation. The CLSM, grout or concrete is

injected from the tip of the auger before the auger is raised to prevent voids from forming.

DDCs vary from 18 to 36 inches in diameter; the selected diameter is based on building loads

and the number of columns per bearing location. For preliminary planning purposes, Langan

conclude DDCs would need to extend through the entire refuse thickness and approximately 5

to 10 feet into the underlying native soil. Some medium stiff clay was encountered at these

depths. Because DDCs displace the soil laterally, it may help increase the strength of any






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medium stiff clay. The embedment length into native soil will be evaluated as part of a final

geotechnical report and pile load test program.

DDCs are designed and installed by specialty design build contractors. The vertical and lateral

capacities of the DDCs, including the effects of downdrag and settlement on the capacities and

the amount of reinforcing steel necessary to resist lateral loads and resulting bending

moments, will be developed by the design build contractor and reviewed by the geotechnical

engineer of record.

A section view of a typical DDC that would support a shallow foundation is provided in

Appendix J. Because the CLSM grout is injected under pressure during installation of the

DDCs, Langan anticipate the interface between the DDC and the adjacent soil and refuse layers

will be effectively sealed. In addition, the DDCs should not need to extend significantly

beneath the refuse and into the underlying clay unit. For these reasons, Langan conclude that

the potential for introducing leachate or shallow groundwater into underlying aquifers should be

very low both during and after construction. In addition, installation of DDCs should produce

minimal soil and refuse cuttings because the soil and refuse would be displaced laterally during

drilling. Furthermore, because the DDC is installed with an auger that displaces soil laterally,

contamination transport to deeper layers at the tip of the pile while advancing the auger is also

not likely to occur.

5.4.2 Auger Cast In Place Piles

Non-displacement or displacement Auger Cast in Place (ACIP) pile may be used to support the

proposed buildings in areas where the refuse thickness is greater than 40 feet or the building

loads are relatively large. ACIP piles are proprietary piles and are installed by drilling to the

required depth with a hollow-stem, continuous-flight auger. When the auger reaches the

required depth, cement grout or concrete is injected through the bottom port of the hollow

stem auger. Grout or concrete is injected continuously under pressure as the augers, still

rotating in a forward direction, are slowly withdrawn, replacing the soil removed by the drilling

operation. While the grout is still fluid, a steel reinforcing cage is inserted into the shaft. ACIP

piles can range in diameter; however, 16- and 24-inch-diameter ACIP piles are typical. We

preliminarily estimate that ACIP piles would extend at least 50 feet or more into the native soil

below the refuse.






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Displacement ACIP piles are similar in type and installation method to the non-displacement

ACIP piles except that they have a reverse tread on the auger which results in lateral

displacement and densification of the surrounding soil. Drilling of displacement ACIP piles

results in the generation of fewer spoils than that of non-displacement ACIP piles, thus

reducing the need for managing refuse cuttings.

Similar to the DDCs previously discussed, because the grout or concrete for the ACIP pile is

injected under pressure, Langan anticipate the grout would penetrate into the voids in the

refuse and soil surrounding the pile, thereby effectively sealing the interface between the pile

and the adjacent soil and refuse and reducing the potential for introducing leachate or

groundwater into underlying aquifers both during and after construction. This process helps

eliminate the potential for a preferential seepage path along the pile/soil contact. After the grout

is injected, reinforcing steel can be lowered into the pile. A section view of a typical ACIP piles

is provided in Appendix J.

5.4.3 Load Tests and Construction Issues

We are currently developing a pile load test and indicator program to evaluate the vertical

and/or lateral load deformation characteristics for both DDCs and ACIP piles, including potential

issues with installation within the landfill waste. The number of piles, type of load test (tension

and/or compression), strain gauges and locations are currently being developed in conjunction

with the design building contractors. The intent of the load test program is to evaluate the

capacities of both proposed foundation types and provide data that can be used to efficiently

design the deep foundation system for the proposed structures.

Because obstructions may be encountered in the refuse that may prevent the DDCs or ACIP

piles from getting through the refuse, it may be necessary to predrill through the refuse. If an

obstruction is encountered at a shallow depth, it may be possible to remove the obstruction.

However, if it is not practical to remove the obstruction then the pile will need to be relocated.

The structural engineer will design and specify an allowance for relocation of DDCs or ACIP

piles. The potential for buried obstructions will also be evaluated as part of a load test and

indicator program.






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6.0 FINAL COVER

6.1 Final Cover Design

Current California Code of Regulations Title 27 regulations require a "prescriptive" cover design,

one that is established by regulation and intended for use in the closure of all landfills. The

prescriptive cover, as outlined in Title 27, §21090(a)(1-3), shall contain:

A foundation layer of not less than 2 feet of appropriate materials. However, Title 27

Section 21090 allows for a lesser thickness, if the ultimate land use will not affect the

structural integrity of the final soil cover. The foundation layer materials may be soil,

contaminated soil, incinerator ash, or other waste materials, provided that such

materials have appropriate engineering properties to be used for a foundation layer.

Low permeability layer not less than 1 foot thick and of hydraulic conductivity not more

than 1E-6 centimeters per second (cm/sec).

Erosion resistant layer not less than 1 foot thick capable of sustaining vegetation and

resistant to wind, raindrop impact, or runoff or mechanically resistant.

Langan prepared a Draft Landfill Cover Investigation report, dated 13 February 2015 (Langan,

2015c). This report describes background information and the results of several phases of

investigation to evaluate the existing landfill cover for use as the final cover. A full copy of this

draft report is included in Appendix J. The existing data indicates that Parcels 1/1NW, 2 and 3/6

currently have a suitable soil cover which includes the three prescribed layers (foundation, low

permeability and erosion) (Langan, 2014c). Based on the results of the borings and test pits

performed in Parcel 4 the existing clay cover consists predominately of clay with a permeability

of 1x10-6 cm/sec or less. The clay cover varies in thickness from approximately 1 foot to 5.5

feet. Areas where the low permeability soil layer were not observed, i.e. around borings B-16,

B-23, B-37, B-38 and B-39, will be further evaluated as part of a final geotechnical investigation

and final cover design. Assuming the refuse acts as the foundation layer, as it contains a mix of

soil and refuse causing it to be firm and non-yielding, the upper 12 inches of the soil above the

refuse meets the criteria for the low permeability layer. Most of Parcel 4 has sufficient cover

over the low permeability layer. However, there is insufficient cover soil (i.e. the erosion

resistant layer) at some locations, which does not meet the current regulations. This condition

will be further evaluated as part of a final geotechnical investigation and final cover design.






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The subgrade elevation for the development is planned to be about 4 feet above the clay cover.

The earthwork activities will include cutting and filling with both on-site and off-site material to

achieve the subgrade. Over the subgrade, the final cover will include buildings, structural slabs,

paved streets, plazas and landscaped open areas. In areas where the cover will be disturbed,

the cover soil layer will include a concrete structural slab or aggregate base, which are both

suitable as an erosion resistant layer. The final thickness of the cover soil layer will be

evaluated based on final grades, but will be included consistently throughout the Project in

accordance with the final cover requirements.

Penetrations made in the low permeability layer will need to be repaired. In street areas where

a utility corridor extends beneath the low permeability layer it may be necessary to lower and

replace the low permeability layer as described in Sections 6.1.2 and 6.1.5.

The ground surface is expected to settle significantly during and after development; however,

adjacent to pile caps soil may ‚hang up‛ because of adhesion between the soil and the pile.

This may cause differential settlement over a short distance where cracks in the low

permeability layer could develop. Along the perimeter of the structurally supported areas of the

site, the structural slab will minimize water migration into the waste, while a perimeter hinge

slab of pavement will provide a barrier to minimize surface water migration into the waste.

Where a perimeter hinge slab or adjacent pavement will not exist along the perimeter, an

additional barrier or drainage layer will be installed to minimize potential for surface water

migration into the waste.

The following subsections present recommendations for earthwork.

6.1.1 General Earthwork Recommendations

The fill material for the foundation layer and low permeability layer should meet the

requirements of Title 27, §21090(a). General fill and backfill requirements should specify that

material be compacted in lifts of 8 inches or less using mechanical equipment. All materials to

be used as fill, including on-site soil, should be free of organic material (including wood), contain

no rocks, lumps, or rubble larger than 6 inches in greatest dimension.

6.1.2 Foundation Layer

If the low permeability layer is lowered, it is likely the bottom of the excavation would be within

the refuse layer. The foundation layer should form a stable layer on which to place the low






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permeability layer and should be non-yielding. The refuse may be used as the foundation layer

provided the bottom of the excavation is firm and non-yielding. If the refuse layer is used as

the foundation layer, Langan recommend that it be compacted with a smooth drum roller to

provide a firm and non-yielding surface without specified compaction criteria.

If the refuse is pumping and yielding under the weight of the compaction equipment, it may be

necessary to overexcavate the refuse and replace it with more stable granular material such as

baserock and geotextile reinforcement. Typically the foundation layer is at least 2 feet thick;

however, Title 27, §21090 allows for a lesser thickness, if the ultimate land use will not affect

the structural integrity of the final soil cover. In areas where the low permeability layer is

lowered, the overburden pressure will be reduced, which will reduce the expected total and

differentially settlements. This should help maintain the structural integrity of the soil cover.

Therefore, Langan recommend that the thickness of the foundation layer using granular

material necessary to provide a firm and non-yielding subgrade be evaluated in the field during

construction. Our experience indicates that two feet of granular fill above a geotextile or

geogrid will bridge above the refuse and provide a stable foundation layer. If possible, Langan

recommend the thickness be reduced from two feet to minimize the amount of refuse that

would need to be moved; the amount by which the granular fill can be reduced and still provide

a stable subgrade to compact the soil cover will be evaluated in the field on a case by case

basis.

If granular material is used to construct a foundation layer, the exposed refuse subgrade should

be rolled with a smooth drum roller. A geotextile such as Mirafi 500x or geogrid such as Tensar

1200 BX can then be placed on top of the refuse. The foundation layer should then be

constructed by placing granular material in lifts not exceeding 8 inches in final thickness and

compacted to at least 90% relative compaction7.

6.1.3 Low Permeability Layer

If the low permeability layer is removed in areas where utility corridors may need to be

lowered, it will need to be replaced. The on-site clay above the refuse meets the permeability

requirements where tested and would minimize infiltration of water into the refuse unit. If

imported soil is to be used for the new low permeability layer it will be cohesive and tested

7 Relative compaction refers to the in-place dry density of soil expressed as a percentage of the

maximum dry density of the same material, as determined by the ASTM D1557 laboratory

compaction procedure.






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prior to being approved for use. Samples will need to be submitted to a laboratory, remolded to

simulate field conditions and compacted in the laboratory to at least 90% relative compaction

and tested to check the minimum hydraulic conductivity can be achieved.

The new low permeability layer should be at least 12 inches thick (final compacted thickness),

moisture conditioned to about 2% to 6% over optimum moisture content and compacted to at

least 90% relative compaction. The low permeability should have an in-place permeability of 1E-

6 cm/sec or less and a plasticity index of at least 10 or greater. To avoid cracking and

desiccation of the low permeability, it should be kept moist and covered within 1 to 2 days after

being placed. Where the new low permeability layer ties into the existing low permeability

layer, it should horizontally overlap the existing low permeability layer by at least 2 feet.

Where a new low permeability layer is installed in-situ permeability tests should be performed

to check the permeability. One test per 2,500 cubic yards of low permeability layer placed or a

minimum of two tests per new section should be performed. If the tests fail then the layer

should need to be either reworked or replaced.

6.1.4 Fill above Low Permeability Layer

All areas to receive improvements should be stripped of vegetation and organic topsoil. The

surface exposed by excavation/stripping should be scarified to a depth of at least 6 inches,

moisture-conditioned to near optimum moisture content, and compacted to at least 90%

relative compaction. The exposed ground surface should be kept moist during subgrade

preparation.

All fill (excluding landscaping soil) above the low permeability layer, should be placed in

horizontal layers not exceeding 8 inches in loose thickness, moisture-conditioned to near the

optimum moisture content, and compacted to at least 90% relative compaction. The upper 6

inches of the soil subgrade in pavement areas should be compacted to at least 95% relative

compaction. Fill deeper than 5 feet should also be compacted to at least 95% relative

compaction. Fill above the low permeability layer should have a low expansion potential

(defined by a liquid limit of less than 40 and a plasticity index lower than 12). During

construction the on-site and proposed import material should be checked for suitability for use

as fill.






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6.1.5 Utility Trenches

Backfill for utility trenches should comply with the general requirements for fill. The pipe should

be embedded in granular fill and compacted to 95% relative compaction. The granular fill should

extend at least 6 inches above the pipe. To avoid damaging pipes, a light vibratory plate should

be used to compact the granular fill around the pipe. An impermeable plug consisting of clay or

lean concrete will be placed periodically along utility trenches to limit LFG migration along the

trench.

Where the utility trench excavation penetrates into the low permeability layer, the low

permeability layer will have to be replaced. The bottom and sides of the trench should be lined

with a geomembrane, such as 40 mil High Density Polyethylene (HDPE), to the bottom of the

existing low permeability layer (in the trench). The membrane should be keyed into the low

permeability layer and protected (via a protective fabric) within the trench prior to backfill. The

low permeability layer that was excavated within the trench should be replaced at the same

elevation as before with at least a 12 inch thick layer of clay and be compacted to the

recommendations presented herein.

6.2 Existing Topography

The existing topography of the Site was provided by the City of Santa Clara in an AutoCAD file

of an aerial photogrammetric survey performed on November 15, 2013. All elevations noted

herein are in the NAVD 88. The existing topography is shown on the preliminary design

drawings in Appendix D.

Parcel 1/1NW – The existing elevations around the perimeter of Parcel 1/1NW vary

between elevation (el.) 5 and el. 8. The elevation high points are within the central

portion of the parcel at about el. 60 and at the northwest corner at about el. 70. The

grades fall from the high points to the edge of the refuse mound to about el. 40 to the

east and northeast and to about el. 55 to the west and south. From the top of edge of

the Landfill the side slopes down to the perimeter elevations vary from 3H:1V to 5H:1V.

Based on City records and previous investigations performed to date, it is anticipated

that the top of the refuse layer varies between el. 47 and el. 37. The surface grades

vary between 5 feet and 15 feet higher than the refuse.






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There is an existing driveway access to Lafayette Street in the southwest corner of the

Parcel at about el. 8. The paved driveway slopes up into the Parcel at about an 8%

grade to provide access to the existing BMX facility and for golf course maintenance.

There is also a City drainage conveyance ditch along the entire eastern edge of the

Parcel at el. 0 and a levee for the Guadalupe River with the top of berm at el. 25.

Parcel 2 – The existing elevations around the perimeter of Parcel 2 vary between el. 5

and el. 8. The elevation high point is within the north central portion of the Parcel at

about el. 52. The grades fall from the high point to the edge of the refuse mound to

about el. 35 to the east, el. 25 to the south and el. 20 to the west. From the top of edge

of the Landfill the side slopes down to the perimeter elevations vary from 2H:1V to

3H:1V. Based on City records and previous investigations performed to date, it is

anticipated that the top of the refuse layer varies between el. 19 and el. 40. The surface

grades vary between 7 feet and 10 feet higher than the refuse.

There is an existing golf cart bridge over Lafayette Street from Parcel 4 that connects to

Parcel 2 at about el. 25. The bridge span reaches high point of about el. 39. There is

also a City drainage conveyance ditch along the entire eastern edge of the Parcel at el. 0

and a levee for the Guadalupe River with the top of berm at el. 25.

Parcel 3/6 – The existing elevations around the perimeter of Parcel 3/6 vary between el.

9 and el. 11. The elevation high point is within the central portion of the parcel at about

el. 82. The grades fall from the high point to the edge of the refuse mound to between

el. 53 to el. 56 around the majority of the edge and el. 68 in the southwest corner.

From the top of edge of the Landfill the side slopes down to the perimeter elevations

are at about 3H:1V. Based on City records and previous investigations performed to

date, it is anticipated that the top of the refuse layer varies between el. 31 and el. 54.

The surface grades vary between 10 feet and 35 feet higher than the refuse.

There is an existing paved golf cart access path in the southeast corner from Parcel 4

that slopes up to Parcel 3/6 from el. 12 to el. 54 at about a 10% slope. There is also an

access location in the northeast corner of the Parcel from the adjacent property to the

north from el. 10 to el. 30. The Union Pacific railroad tracks are located along the entire

eastern edge of Parcel 3/6 at about el. 9.






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Parcel 4 – The existing elevations around the perimeter of Parcel 4 vary between el. 10

and el. 20. The elevation high points are located throughout the Parcel up to about el.

34. The grades around the edge of the refuse mound are el. 20. There is an area within

the Parcel where no refuse exists and existing grades drop to as low as el. 7 (within a

portion of the existing driving range and lined pond). Based on City records and

previous investigations performed to date, it is anticipated that the top of the refuse

layer varies between el. 18 and el. 27. The surface grades vary between 3 feet and 7

feet higher than the refuse.

The elevation of Great America Parkway along the approximate 340 foot frontage is

between el. 15 and el. 22. Stars and Stripes drive along the majority of the southern

boundary of the Parcel is between el. 13 and el. 19. The Union Pacific railroad tracks are

located along the entire eastern edge of Parcel 4 at about el. 10 to el. 13.

6.3 Preliminary Grading

The goals for the proposed grading include:

Minimizing disturbance of existing refuse;

Phasing of earthwork to efficiently replace, relocate, operate and maintain the landfill

collection systems;

Satisfying and maintaining Americans with Disabilities Act (ADA) slope and access

guidelines recommendations for buildings, site and access to public areas;

Strategically designing site to accommodate future settlement of Landfill; and

Site aesthetics.

The preliminary site design maintains the first floor elevation (for the Parcel 4 structural slab and

other buildings and parking garage structures) a minimum of 10 feet above the anticipated

refuse elevations. Mass earthwork will include grading each parcel to a subgrade level about 5

feet above the top of refuse. This will allow for the protection of the existing low permeability

layer during earthwork, provide a working pad for the installation of the LFG collection system

and deep foundations, maintenance of the leachate recovery system risers, and provide vertical






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clearance above the refuse to minimize refuse disturbance during earthwork, pile cap, utility

corridor, and building slab construction.

The final design for the on-grade streets, plazas and open space/landscape areas will be

designed with a combination of hinged slabs, adjustable footings and other ‚situation specific‛

elements such as lightweight fill. Because of the heterogeneity of the refuse, it is difficult to

accurately predict the amount and location of settlement over a given period of time. As such,

a critical aspect of the site design will be to determine where the settlement will manifest. The

final site and grading plans will be designed for the ultimate grade after site settlement.

Building entrances, plazas, and access pathways will be designed to maintain compliance with

the requirements of the California Building Code, California Disabled Accessibility Guidebook

(CALDAG) and ADA Standards. Within the transition areas (from structural support to at-grade

support), the hinged slabs, adjustable footings, and other measures to address the settlement

will be aesthetically designed. The settlement vaults for the storm drain, sanitary sewer and

water utilities are conceptually shown on the preliminary design drawings. There final locations

will be based on a final design. A robust periodic monitoring and maintenance program will be

implemented to maintain compliance and site aesthetics within the transitions and incorporated

into the overall Project Operations, Monitoring and Maintenance (OM&M) plan.

6.4 Preliminary Stormwater Management

The development is subject to federal, state, county and local municipality regulations. The

regulations provide requirements for stormwater system design, stormwater quality and base

flood elevation. The amended Clean Water Act of 1987 required stormwater discharges to be

in compliance with a National Pollution Discharge Elimination System (NPDES) Permit. In

California this permit is issued through the Regional Water Quality Control Board for the San

Francisco Bay Region RWQCB. The San Francisco Bay Board adopted Municipal Regional

Stormwater NPDES Permit Order R2-2009-0074 NPDES Permit No. CAS612008 (Adopted 10-

14-2009 and amended by Order No. R2-2011-0083 on 11-28-2011), aka the Bay Area Municipal

Regional Stormwater Permit (MRP).

In Santa Clara County, the cities of Campbell, Cupertino, Los Altos, Milpitas, Monte Sereno,

Mountain View, Palo Alto, San Jose, Santa Clara, Saratoga, and Sunnyvale, the towns of Los

Altos Hills and Los Gatos, the Santa Clara Valley Water District, and the County of Santa Clara

(Co-permittees) have joined together to form the Santa Clara Valley Urban Runoff Pollution






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Prevention Program (SCVURPPP). These entities share a common permit to discharge

stormwater to South San Francisco Bay with a mission to assist in the protection of beneficial

uses of receiving waters by preventing pollutants generated from activities in urban service

areas from entering runoff to the maximum extent practicable.

The SCVURPPP Permit Provision C.3 contains requirements for controlling the potential

impacts of land development on stormwater quality and flow. In 2006, the C.3 requirements

became effective for projects that create or replace 10,000 square feet or more of impervious

surface. To meet the C.3 requirements, projects must include appropriate site design

measures, pollutant source controls and treatment control measures. Projects that produce

increases in runoff peak flows, volumes and durations that may cause erosion in downstream

receiving water must also include hydromodification control measures. The SRVURPPP

prepared a C.3 Stormwater Handbook dated April 2012 to assist projects in designing

appropriate post-construction stormwater controls to meet local jurisdictional requirements and

the requirements of the MRP. The Project will include stormwater treatment measures as

preliminarily shown on the design drawings in Appendix D. Hydromodification control

measures are not required as the Site is outside of the mapped hydromodification zones.

The Santa Clara Valley Water District (SCVWD) has jurisdiction over the San Tomas Aquino

Creek and Guadalupe River, their existing levees and the conveyance of stormwater to these

waterways. Since the existing levees adjacent to the Site are certified by the Federal

Emergency Management Agency (FEMA), impacts to or proposed modifications of the levee

will require SCVWD review and approval, and may require a submission to FEMA for levee re-

certification. Furthermore, the SCVWD requires that no increase to the 100 yr. peak flood

elevation within these waterways is permissible without levee recertification.

The Project will disturb one or more acres of soil and is required to obtain coverage under the

General Permit for Discharges of Stormwater Associated with Construction Activity

(Construction General Permit, 2009-0009-DWQ). Construction activity subject to this permit

includes clearing, grading and disturbances to the ground (e.g., stockpiling or excavation). The

Construction General Permit requires the development and implementation of a Stormwater

Pollution Prevention Plan (SWPPP). The SWPPP will contain a site map(s) which shows the

construction site perimeter, existing and proposed buildings, lots, roadways, stormwater

collection and discharge points, general topography (both before and after construction) and

drainage patterns across the project. The SWPPP will list Best Management Practices (BMPs)

http://www.scvurppp-w2k.com/site_design.shtml

http://www.scvurppp-w2k.com/site_design.shtml

http://www.scvurppp-w2k.com/source_control.shtml

http://www.scvurppp-w2k.com/treatment_control.shtml

http://www.scvurppp-w2k.com/hmp.shtml

http://www.swrcb.ca.gov/water_issues/programs/stormwater/construction.shtml






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that will be used to protect stormwater runoff and the placement of those BMPs. In addition,

the SWPPP will contain a visual monitoring program; a chemical monitoring program for ‚non-

visible‛ pollutants to be implemented if there is a failure of BMPs; and a sediment monitoring

plan. Erosion control measures will be installed prior to site activities that disturb soil and

maintained throughout the Project. Storm water controls will be based on practices described

in the "Blueprint for a Clean Bay, Best Management Practices for the Construction Industry,‛

provided as part of the Santa Clara Valley Nonpoint Source Pollution Control Program. Storm

water controls comprise the on-site sediment and erosion controls to limit soil and sediment

discharges to off-site drainage channels and storm drains (discharging to the San Tomas

Aquinos Creek and Guadalupe River). These controls may include the placement of straw bale

barriers across runoff channels on the Site, straw bale barriers around storm drains and

catchment basins (once constructed), and covering soil stockpiles with secured tarps or plastic

sheeting. The preliminary erosion and sediment control plans are provided in Appendix D.

The stormwater runoff from Parcel 4 and Parcel 5 will discharge to the San Tomas Aquino

Creek via new stormwater outfalls. The invert of the outfalls will be set above the bottom of

the Creek, at a final elevation to be coordinated with the SCVWD to place the invert above

sediment levels within the Creek. The existing Golf Course Pump Station will remain, or

depending on the Parcel 5 development be reconfigured or abandoned.

The stormwater runoff from Parcels 1, 2 and 3 will discharge to the Eastside Retention Basin

and be pumped to the Guadalupe River via the existing Eastside Pump Station. From Parcels 1

and 2 there will be several new outfalls from the Site to the existing Eastside Drainage

Channel. From Parcel 3, the existing drainage infrastructure located north of the Parcel and

west of the railroad will be utilized. The preliminary evaluation identified that a portion of the

existing off-site system may need to be upsized to accommodate Parcel 3. However, these

upgrades may not be required if enough of the stormwater on Parcel 3 is collected and re-used.

The goal for the final stormwater management design will be to treat the stormwater runoff to

protect water quality through the incorporation of on-site sustainable low-impact development

(LID) stormwater measures. Infiltration is not a feasible strategy for the management of the

stormwater and is not recommended. As such, all stormwater treatment measure over the

landfill will be lined with an impermeable liner and include a perforated underdrain connected to

the storm drainage system. During final design the extent and type of the stormwater






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management measures (such as stormwater treatment, harvesting and re-use) to be

implemented within the Project will be determined.

7.0 IRRIGATION AND LANDSCAPING

Proposed irrigation and landscaping at the development will meet the requirements of CCR

Title 27, §21090(a)(3)(A).

Only shallow rooted vegetation will be utilized in landscaped areas that overlie landfill refuse.

The landscape areas adjacent to the proposed buildings, the rooting depths will be designed to

extend to within 1 foot above the low permeability layer. This will be accomplished through

identifying the depth of the refuse, plant selection and the use of impermeable liners and

perforated underdrains connected to the storm drainage system. Where this is not feasible,

trees must be contained within lined planter boxes.

The use of water-intensive landscaping around the perimeter of the buildings will be avoided to

reduce the amount of water introduced to the landfill. In addition, irrigation of landscaping

around the building will be limited to drip or bubbler-type systems. The Project will be served

by the City’s reclaimed water main and a new reclaimed water network will be incorporated

into the design of the development so that the irrigation needs can be met by this system.

8.0 UTILITIES

The installation of new utilities will be required for the proposed development. The preliminary

design drawings are provided in Appendix D. Existing on-site utilities are limited and will be

replaced and expanded. Utilities installed above the refuse will be designed and maintained in

general accordance with CCR Title 27 §21190. Utilities will be constructed to mitigate the

effects of differential settlement and the utility connections will be designed with flexible

connections and settlement vaults. Utilities to be installed include:

Storm Drainage – The existing storm drain system includes existing river outfalls and a

City owned and operated drainage system inclusive of pump stations, retention basins,

open drainage channels, underground conveyance piping and appurtenant drainage

structures. The storm drainage system for the Project will include an underground

gravity network of pipes, catch basin, manholes, water quality LID treatment measures

and other appurtenances. The building drainage will be via internal systems piped






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directly to the storm drains. The final system will be designed to convey the 10 yr.

event peak flows within the underground piped conveyance system and safely convey

the 100 yr. event peak flows from the Site via a combination of the piped system and

surface conveyance.

Sanitary Sewer – The existing sanitary sewers are located in Lafayette Street and

between Parcels 3/6 and 4. The new sanitary sewers for the Project will connect to the

existing infrastructure at new manholes. The on-site sewer for each parcel will be

designed as a redundant system in accordance with the City of Santa Clara

requirements.

Water – The existing City owned and operated water main system is located in

Lafayette Street, Great America Parkway and Stars and Stripes Drive. The new water

service will be connected to the existing water main distribution system and will be

constructed of steel and HDPE Pipe in accordance with the City of Santa Clara and its

Water District’s requirements.

Gas – The existing Pacific Gas and Electric (PG&E) gas system is located Lafayette

Street, Great America Parkway and Stars and Stripes Drive. The new gas service for

the Project will be extended from the existing service in Lafayette Street.

Electrical and Telecommunication Services – Electrical and telecommunications services

lines are to be installed in a joint trench in and around each parcel. The systems will

connect to the existing system that will be extended to the Site from nearby service

locations.

Most of the on-site utility systems will be located above the refuse unit, and it is anticipated

that a small portion of the utility corridors will disrupt the refuse unit at multiple locations. At

these locations, trenches will be constructed as described in Section 6.1.5.

Where utility trenches enter the building pads and at periodic intervals, an impermeable plug

consisting of bentonite clay will be installed. Furthermore, where trenches cross planter areas

and pass below asphalt or concrete pavements, a similar plug will be placed at the edge of the

pavement. The plugs will extend from the bottom of the trench to the subgrade elevation. The

purpose of these recommendations is to reduce the potential for water to become trapped in






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trenches beneath the building or pavements and limit the migration of methane within utility

trenches.

Due to the potential for methane accumulation in the subsurface some of the underground

utility manholes and vaults will be labeled ‚Confined Space – Hazardous Area, Contact Building

Maintenance Supervisor Prior to Entry, Entry by Authorized Personnel Only‛ to promote the

safety of maintenance personnel. Following completion of the proposed development, periodic

methane gas monitoring will be conducted inside underground utilities in general accordance

with §20933 of Article 6, of Subchapter 4 of CCR Title 27.

A settlement study for gravity flowing utilities will be performed during final design to address

the anticipated settlement. Preliminary design options include steeper pipe slopes, additional

manholes, interim settlement vaults, and inclusion of the monitoring of gravity flowing utilities

in the Project’s OM&M plan.

9.0 ENHANCED LANDFILL GAS COLLECTION AND REMEDIATION SYSTEM

9.1 Existing LFG Collection System

The layout of the existing LFG collection wells and headers and the subsurface details on each

of the Site parcels are included in Appendix A. A total of 88 LFG extraction wells are identified

on the LFG well layout drawings (Real Environmental Products, 2011). As reported in the most

recent LFG collection system monitoring report (Golder, 2014a), the LFG collection system

currently consists of 75 functional LFG extraction wells connected to respective lines,

subheaders, and the main header. The remaining 13 LFG extraction wells (wells E3, C4, A4, H1,

J1, K3, K5, L1, L3, L4, M3, M4, and N3) have been decommissioned because of low methane

levels and high oxygen levels detection (likely due to the damaged well casing below the

ground surface) or due to the presence of excessive water in the well casing. Reportedly, the

decommissioned wells were abandoned by disconnecting them from the gas header system,

the well head vault was removed, the well casing was cut off to about 3 feet below grade, and

the void was filled with soil and bentonite, following procedures in the Post-Closure

Maintenance Plan for the Site (Golder, 2015).

The main header that extends through each parcel is connected to the inlet of a 25 Horsepower

(HP) centrifugal blower/air compressor housed in a fenced area on Parcel 1. Main isolation

valves for repair, shut-down, and vacuum adjustment are installed at each junction of the main






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header and respective subheaders/lines. In addition to the LFG collection wells, multiple

condensate traps are present in each parcel at low points to gravity drain the collected

condensate back into the refuse away from the LFG collection wells through recirculating P-

traps (see Appendix A).

9.2 Proposed LFG Collection System

Replacement and enhancement of the existing LFG collection system is proposed as part of

development at the Site (Langan, 2015a). The proposed LFG collection system is designed to

be consistent with the following state and local regulations:

CCR Title 27, Chapter 3, Subchapter 5, Article 2, §21090 – §21200 – Closure and post-

closure maintenance standards for disposal sites and landfills.

CCR Title 27, Chapter 3, Subchapter 5, Article 2, §21190 – Post-closure land use.

CCR Title 27, Chapter 3, Subchapter 4, Article 6, §20917 – §20937 – Gas monitoring and

control at active and closed disposal sites.

BAAQMD Regulation Rule 8-34.

The proposed plans for LFG collection include installation of vertical LFG extraction wells,

horizontal LFG extraction wells (contingent wells), condensate knock-out pots, and below-grade

horizontal conveyance piping, and manifold connecting the LFG collection wells and condensate

knock-out pots to the process equipment. Considering that detailed Site development plans and

foundation concepts are not yet developed, the proposed concept plans for the LFG collection

system would be modified as the development planning for the parcels progresses. The

concept plans for the proposed LFG collection system are primarily based on concept sections

provided for Parcel 4 (see Appendix K). The well layout and cross sectional details of the

proposed LFG collection system are provided in Appendix K.

These proposed LFG collection and remediation system concept plans presented herein are

based on evaluation of the existing LFG collection well layout, reported radius of influence

(ROI), monitoring reports, and our preliminary pneumatic MDFITTM modeling software results

(Appendix K). MDFITTM is a two-dimensional (2D) analytical model which simulates the air flow

rate in an unsaturated zone and determines the correlation between applied vacuum and air

flow at test well and resultant vacuum, air flow rate, and pore volume exchanges at varying






September 2015

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distances from the test well. In addition, the conceptual plans were also based on

considerations including but not limited to the estimated LFG and condensate generation rates,

potential refuse settlement, potential seismic activity hazards, potential fire hazard, corrosive

impacts of LFG and design life (durability) of the future LFG collection system. A

comprehensive evaluation of these factors will be performed during the Design Document

Phase.

Although our preliminary modeling results agree with the current system vacuum, air flow

rates, and ROI, a pilot test will be performed during Design Document Phase for the

development to verify the design ROI, air flow rates, and vacuum for the proposed LFG

collection wells at each parcel, considering the critical nature of the system design parameters.

Further, it is anticipated that the number and spacing of pile foundations and columns

particularly beneath the Parcel 4 platform structure could alter the flow of LFG to the vertical

LFG collection wells and may affect their effective ROI. To evaluate this issue, pilot test results

and pile foundation plans would be incorporated into a three-dimensional (3D) pneumatic model

(i.e., AIR-3DTM) to predict the influence of these features on the proposed layout of the vertical

LFG collection wells. Therefore, the results of the proposed pilot test, 3D pneumatic modeling,

the final building locations, and corresponding pile foundation and displacement column

locations for each phase of development will be the basis for determining the final locations of

the proposed LFG collection wells.

The major components of the proposed LFG collection system are described below.

9.2.1 Proposed LFG Collection Wells

The proposed LFG collection system will consist of a total of 86 vertical collection wells spread

over the Site. The proposed LFG collection wells on each parcel are estimated to have an

approximately 200 feet ROI, to be verified based on the results of a proposed field pilot test

and 3D pneumatic modeling. The proposed LFG collection wells would be placed approximately

300 feet on center to provide adequate ROI overlap and would be placed outside of the building

footprints, preferably in roadways, landscaped areas, exterior parking lots, or sidewalks. No LFG

collection wells and condensate knock-out pots will be installed within the proposed building

footprints. Overall, four types of LFG collection wells (Type 1 through Type 4) would be

installed:






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Vertical LFG Collection Well Type 1 – Vertical LFG wells located outside the structural

platform would be constructed of Schedule (SCH) 80 polyvinyl chloride (PVC) (or

equivalent) casing and screen or perforated pipe materials. These wells would be

completed at the finished grade with a precast vault with lockable watertight lid to

provide direct wellhead access for operational adjustments, monitoring, and

maintenance. These wells would be telescoping type with slip joints connecting the

well casings with the screens to allow flexibility and expansion of the well screen

vertically downward. The flexibility of vertical expansion of well screens will prevent

potential damage to the well due to refuse settlement. Wellhead connections to the

system below-grade horizontal conveyance piping will be made using a flexible hose

(i.e., Kanaflex™ or LANDTEC™ or equivalent) with adequate slack to prevent potential

damage to the wellhead or conveyance piping due to refuse settlement.

Vertical LFG Collection Well Type 2 – The vertical LFG wells located within the structural

platform in the roadways, landscaped areas, or exterior parking lots would be anchored

(via dowels) and supported by the structural platform slab to prevent potential

settlement of the well due to refuse settlement. These wells would be telescoping type

with slip joints connecting the well casings with the screens to allow flexibility and

expansion of the well screen vertically downward. The flexibility of vertical expansion of

well screens will prevent potential damage to the well due to refuse settlement. These

wells would be constructed of SCH 80 PVC material (or equivalent). These wells would

be completed at the finished grade with a precast vault with lockable watertight lid to

provide direct wellhead access for operational adjustments, monitoring and

maintenance. Wellhead connections to the system below grade horizontal conveyance

piping will be made using a flexible hose (i.e., Kanaflex™ or LANDTEC™ or equivalent)

with adequate slack to prevent potential damage to the wellhead due to refuse

settlement.

Vertical LFG Collection Well Type 3 – Similar to Well Type 1 and Type 2, the vertical LFG

wells located within the structural platform on the sidewalk would be constructed of

SCH 80 PVC material (or equivalent). These wells would be completed below the

sidewalk finished grade and underneath the structural platform slab to eliminate the

potential for LFG leaks into the buildings interstitial space from the well. A precast vault

with lockable watertight lid for direct wellhead access to these wells would be

constructed adjacent to the sidewalk and outside the extent of the building interstitial






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space. These wells would also be telescoping type with slip joints connecting the well

casings with the screens to allow flexibility and expansion of the well screen vertically

downward. The well riser connection to the vault will be made using below-grade

horizontal conveyance piping anchored to the structural slab with pipe hangers. Manifold

connections will be made using a flexible hose (i.e., Kanaflex™ or LANDTEC™ or

equivalent) with adequate slack to prevent potential damage to the wellhead or

conveyance piping due to the refuse settlement. The preliminary configuration and

construction details of the vertical LFG extraction well Type 3 as presented herein are

conceptual only and will be finalized during the Design Document Phase.

Horizontal LFG Collection Well Type 4 (Contingent) – The need for these contingent

horizontal LFG collection wells will be determined during the Design Document Phase

based on the 3D pneumatic modeling results, final building layout plans, and the final

configuration and layout of the proposed piles. If horizontal LFG collection wells located

inside and outside the structural platform are required, they would also be constructed

of SCH 80 PVC (or HDPE) casing and screen or perforated pipe material. The horizontal

wells would be installed in the upper portion of the waste unit and would be connected

to the vertical well system manifold. Overall, three types of contingent horizontal LFG

collection wells may be installed:

Contingent Horizontal LFG Well Type 1 - Wells in the vicinity of areas with proposed

piles. These wells will be installed if the 3D pneumatic modeling results indicate

influence of cement column piles on the LFG flow into the vertical LFG collection

wells, or on their respective ROI and vacuum propagation.

Contingent Horizontal LFG Well Type 2 - Wells underneath the pads of buildings or

underneath the parking garages with larger footprint (e.g., proposed parking garage

in the western portion of Parcel 4) where vertical LFG wells cannot be installed.

These wells will be installed if the 3D pneumatic modeling results indicate that the

LFG in such areas with larger building footprints cannot be adequately mitigated by

the exterior vertical LFG collection wells.

Contingent Horizontal LFG Well Type 3 - Wells in exterior areas (i.e., roadways,

parking lots, landscaped areas, etc.) outside the structural platform (e.g., western

portion of Parcel 4) with no structural slabs/buildings, building LFG protection






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systems or VBM). These wells may be installed to increase the efficiency of LFG

capture at exterior locations and to eliminate the potential for landfill fire and/or

odors.

The proposed number, location, and type of the above described LFG collection wells are

preliminary and are subject to change during the Design Document phase based on the results

of the proposed pilot testing, subsequent 3D pneumatic modeling, the final building locations,

and corresponding pile foundation and displacement column locations. The proposed well

locations and well types have been designed to address site-specific complexities and

constraints (i.e., non-refuse areas and proposed roadways, sidewalks, and buildings). The

proposed vertical LFG collection wells have been preliminarily positioned to avoid interference

with the planned site development constraints (i.e., wells are to be located only within the

proposed roadways and/or outside of the proposed building footprints) and to minimize the

volume of air extracted from non-refuse areas while still providing sufficient coverage within

the refuse areas. The proposed LFG collection system design also includes contingent

elements such as contingent horizontal LFG collection well Types 1, 2 and 3, as well as a

relatively denser network of perimeter vertical LFG collection wells, need of which, will be

confirmed based on the results of the proposed pilot testing and 3D pneumatic modeling

activities.

9.2.2 Potential Off-Site LFG Migration Monitoring and Mitigation

All existing perimeter LFG probes (approximately 44) will be preserved to the extent possible

and will be used to monitor the potential off-site migration of LFG. The integrity and

functionality of these existing perimeter LFG probes will be evaluated as required during the

Design Document Phase. Installation of approximately 30 additional perimeter LFG probes is

proposed (Figure 9, Appendix K). The proposed additional LFG probes will be located at the

perimeter of all parcels outside the refuse limit and within the site property boundary. The

proposed additional LFG probes will be spaced approximately 1,000 feet from each other and

will be constructed of multi-nested well screens (two to three well screens in one borehole)

depending on the nearby refuse thickness. The proposed location and number of the additional

perimeter LFG probes are preliminary and will be evaluated and finalized during the Design

Document Phase, consistent with CCR Title 27, Chapter 3, Subchapter 4, Article 6, §20921,

20923, 20925, 20931, 20932, 20934, 20937, and 20939 requirements. While the location of

these proposed additional LFG probes will be confined geographically by the existing site






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property boundary, the select point locations will take into consideration the location of nearby

LFG collection wells (i.e., the perimeter LFG probes will be located at or outside the LFG

collection ROI to the extent possible).

In addition, a dense network of LFG collection wells along the landfill perimeter is proposed to

mitigate the potential off-site LFG migration. The effective ROI and spacing of the perimeter

LFG collection wells will be determined based on the proposed pilot testing and 3D pneumatic

modeling results. The proposed conceptual LFG collection well network, as depicted on Figures

9 through 9E (Appendix K), currently does not factor in the denser network of LFG collection

wells along the landfill perimeter. Therefore, the proposed number of new LFG collection wells

(86) is likely subject to increase during the Design Document phase based on the proposed

pilot testing and 3D pneumatic modeling results.

In case elevated methane concentrations are measured at the perimeter wells during Site

development activities or during the future use of the developed property, response steps will

be taken to mitigate the off-site LFG migration to ensure compliance with the regulatory

requirements. The response plan may include optimizing and increasing the flow rate/vacuum

at the perimeter LFG collection wells to more effectively capture LFG before it reaches the

landfill perimeter.

9.2.3 Proposed LFG Collection System Manifold

The LFG collection system below-grade horizontal conveyance piping and manifold will consist

of branch lines (laterals), subheader lines, and main header conveyance pipelines. Each LFG

collection well will first be connected to a branch line, then to a subheader line, and finally to a

main header line. The main header from each parcel will be independently connected to the

existing LFG process equipment. Main header lines will be located in the roadways or

landscaped areas with or without the structural slab support. All branch lines, with the

exception of the LFG collection wells located on the edge of the side walk (LFG extraction well

Type 3), will be sloped towards their respective subheader lines to prevent condensate

accumulation within the piping network. Branch lines associated with LFG collection wells

located on the edge of the side walk (LFG extraction well Type 3) will be sloped towards their

respective collection wells. Similarly, each subheader line will be sloped towards the main

header line. Condensate knockout pots will be located at low points along the branch lines,

subheader lines, and main header lines approximately every 300 to 400 feet of pipe run within

structural platform areas and approximately 1,000 feet of pipe run outside the structural






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platform areas. Condensate knockout pots will also be installed where the proposed piping

makes a right angle turn or any other local low spot within the piping network.

All piping within the structural platform will be placed within the proposed 2 foot crushed stone

fill material of the proposed building methane vapor protection system. To overcome depth

restrictions and still facilitate drainage of condensate via gravity (i.e., sloped piping) in the

knockout pots within the structural platform, all piping will have a slope of approximately 0.5%,

condensate knockout pots will be installed approximately every 300 to 400 feet of pipe run, and

all piping diameters will be approximately 20 to 30%larger than normally required.

All piping in the area outside the structural platform will have a minimum of 1 to 2% slope to

facilitate collection of condensate via gravity into the knockout pots, spaced approximately

1,000 feet of pipe run. All knockout pots will be equipped with a submersible pump and an

associated water level sensor to initiate the transfer of the condensate. Condensate will be

transferred to a holding tank, which is to be installed within the existing process equipment

enclosure on Parcel 1, and further discharged into a sanitary sewer system, pending sewer

discharge permit approval. The layout of condensate knockout pots, collection subheader lines

and the collected condensate holding tank are provided in Appendix K. The proposed number

and location of the condensate knockout pots are preliminary and are subject to change during

the Design Document phase.

9.2.4 Process Equipment

The existing process equipment will continue to be used for future collection of LFG with some

modifications/additions for collection, potential treatment, and disposal of condensate. It is also

proposed that the existing flare be serviced for future use or the process equipment be

upgraded with a new flare. Currently, the flare is used as a standby unit only when the existing

microturbines that are used to generate electricity from captured methane gas are down for

maintenance. The existing process equipment is currently housed outside the old equipment

enclosure (i.e., shed) in a fenced area in Parcel 1. An emergency electrical power backup

generator will be provided to run the entire LFG collection system process equipment (i.e.,

blowers, compressors, motors, flare, and microturbines, etc.) in case of electrical power

interruption due to unforeseen conditions.






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9.2.5 Settlement Considerations

To minimize the effect of differential landfill refuse settlement on the proposed LFG collection

wells and manifold system, high burial pressure and vacuum rated flexible hoses (i.e.,

Kanaflex™ or LANDTEC™ or equivalent) will be used at right angle connection manifold joints

(i.e., branch line to subheader line connections, and subheader line to main header line

connections). The flex hose will be made of flexible material, reinforced with non-corrosive

stainless steel wire helix (or equivalent), capable of withstanding relatively high temperatures.

The flexible hose will have a 3 inch soft scuff at each end of the hose and will be connected to

the branch lines, subheader lines, and main header lines with power lock clamps that will be

tighten to the manufacturer’s recommended torque. In addition, for a more secure connection,

a collar will be welded or glued to the pipe to form a ridge. The collar will be positioned prior to

the installation of the power lock clamps to provide additional support and prevent the flexible

hose connection from slipping. The flexible hose will remain flexible at least at 20% extension.

Other equivalent methods of flexible hose connections will be considered during the Design

Document phase.

The proposed LFG extraction wells will be constructed of a SCH 80 PVC material (or equivalent)

telescoping casing and slip coupling assembly to permit the increase in well casing length due

to potential landfill refuse settlement. Estimations of refuse settlement will be derived and

applied to determine the required increase in length of the telescoping casing. Based on landfill

gas field monitoring log reports previously prepared by Golder, the average temperature of the

landfill gas ranges from 66oF of 104oF and currently does not exceed 120oF. The maximum

operating temperature for SCH 80 PVC is 140oF, which is in far excess of the existing normal

LFG system operating conditions of 90oF to 120oF. It is proposed that the LFG collection wells

will be constructed of SCH 80 PVC (or equivalent); however, if during the proposed pilot testing

activities the LFG temperatures are observed to be in excesses of 140oF, the cause of the

elevated temperatures will be investigated, and the LFG extraction well design will consider the

use of HDPE (or equivalent) material with relatively higher temperature rating. To minimize the

effect of potential refuse settlement, HDPE, which is flexible and absorbs differential

settlement better than SCH 80 PVC, will be used for the majority of main header, subheader,

and branch line construction.

The potential settlement of refuse over time, following the construction of the structural

platform/ slabs, has the potential to create a void space beneath the slab. Figure 17 (Appendix






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K) presents a conceptual schematic of the potential void space under structural platform/slabs

that may be developed due to the potential settlement of refuse over time. The influence of the

potential void space on the performance of the LFG wells is anticipated to be minimal because

the vertical and contingent horizontal LFG extraction wells are designed to be screened

approximately 5 feet and 2.5 feet below the top of refuse, respectively, to hinder the effect of

potential short-circuiting from the void space. The LFG extraction telescoping vertical well

casings are designed to expand vertically downward as the refuse settles, thereby maintaining

the 5 feet interval between the well screen and the top of refuse. The confining clay cap and fill

material above the refuse, the vertical telescoping LFG extraction wells, the contingent

horizontal LFG extraction wells, and all associated piping are also anticipated to settle with the

refuse, thereby maintaining the integrity and functionality of the methane mitigation system.

The development of void spaces under structural platform/slabs may pose a risk of ambient air

intrusion into the LFG extraction well screens. Therefore, the LFG extraction wells are designed

to operate in a balanced way using the wellhead controls and gate valves to prevent ambient air

intrusion from the potential void spaces into the LFG system. The influence of the potential

void space beneath the structural platform/slabs on the LFG system capture zones (ROI) and

performance will be further evaluated using 3D pneumatic modeling during the Design

Document phase.

9.2.6 Other LFG Collection System Design Considerations

In order to ensure protection of human health, public safety, and the environment, potential

seismic hazard, fire hazard, and corrosive impacts will be considered and evaluated during the

Design Document Phase:

Seismic Hazard Considerations – The Site is located within an area where strong to

violent ground shaking could occur, which can potentially cause damage to the

proposed LFG collection system due to potential liquefaction settlement and seismic

densification during an earthquake. A seismic hazard analysis will be conducted during

the Design Document Phase to evaluate seismic effects on the proposed LFG collection

system. Based on the results of the seismic study, the components of the LFG

collection system will be designed to accommodate the anticipated seismically induced

settlements. In addition, a post-construction seismic monitoring and inspection plan will

be developed and implemented as part of the routine OM&M of the system.






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Fire Hazard Considerations – Surface and sub-surface fires can occur during

construction activities at the landfill Site. The primary threat of landfill fires results from

careless on-site smoking, welding or other hot work, improper equipment maintenance,

and improper LFG control system operations. As part of the Design Document Phase, a

fire safety measures and emergency response plan would be developed for general

construction activities, as well as for the construction activities related to the LFG

collection system.

Corrosive Impact Considerations – Decomposition of waste in landfills generates

corrosive gasses (i.e. sulfur-based gas such as hydrogen sulfide) which can be

microbially converted to sulfuric acid (H2SO4), thus producing low pH environments..

Both LFG and fluids can cause corrosion of landfill infrastructure (LFG collection system)

and building infrastructure (slabs and piles). To minimize the impact of corrosion on LFG

collection system, critical units and parts would be fabricated from corrosion resistant

materials, including HDPE, PVC, corrosion-resistant stainless steel, and other materials

with corrosion resistant coatings.

9.3 Proposed LFG Collection System Remedial Benefits

The proposed LFG collection and remediation approach has been developed to improve the

effectiveness of the existing LFG collection system through enhanced subsurface gas flow

characteristics (due to increased borehole and LFG extraction well diameters), increased

capture zone (due to the proposed structural platform/slabs that will act as a low permeability

upper confining layer over the landfill refuse), and better moisture control of the refuse. The

proposed Site development and the LFG remediation efforts are anticipated to reduce the

amount of LFG and leachate generated from the landfill refuse, which in turn will improve the

Site groundwater quality. Key elements of the Site development and the proposed LFG

collection system that will result in remedial benefits include the proposed structural

platform/slabs, building horizontal LFG protection system and VBM, storm water management

system, collection and removal of condensate water, and increased capture zone (ROI) of the

LFG collection well network.

The addition of the proposed structural platforms/slabs and VBM, stormwater

management system, and removal of condensate water will reduce the moisture

content of the refuse over time. Decrease in the refuse moisture content will hinder the






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microbial activity and anaerobic degradation rates of the refuse. This will subsequently

reduce the amount of LFG and leachate generated from the landfill refuse which in turn

will improve the Site groundwater quality.

The increased number of the proposed LFG collection wells as compared to the existing

number of wells will result in an increased capture and removal rate of the LFG.

The addition of the proposed structural platform/slabs and VBM will also act as a low

permeability upper confining layer over the landfill refuse and is anticipated to further

increase the LFG system capture zones (ROI). The proposed pilot testing data and 3D

pneumatic modeling will be used to verify that the proposed increased number of LFG

collection wells and installation of the structural slab (i.e., upper confining layer) will

result in an improved LFG capture and removal rate of the new system.

The improved capture and removal rate of the LFG, including VOCs, resulting from the

operation of the new system will facilitate the mass transfer of VOCs from adsorbed

and dissolved phases to the vapor phase due to concentration gradients that in turn will

result in VOC source remediation.

Continued decreases in the LFG flow rates are expected in the future due to the ongoing

natural refuse degradation processes. The proposed LFG collection and remediation system’s

operation and the expected reduction in refuse moisture content due to the Site development

strategy (i.e., construction of structural platforms/slabs and VBM, stormwater management

system, and removal of condensate water, etc.) are anticipated to further reduce the

subsurface concentrations of LFG in the future.

9.4 Conceptual Field Implementation Plan

The LFG control and monitoring program will continue pursuant to CCR Title 27 §20921 through

§20939, and BAAQMD Regulation 8 Rule 34, but interim measures may be necessary to

facilitate continued effectiveness during construction and reinstallation. The field

implementation for the LFG collection system installation would be primarily dependent on

compliance with BAAQMD Regulations, health and safety issues, and coordination with the

other on-site work. These issues will be addressed as follows:






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Compliance with BAAQMD Regulations - The implementation of proposed LFG

collection system would require compliance with BAAQMD Regulation 8-34. To comply

with the BAAQMD regulations 8-34-117.4, 8-34-117.5, and 8-34-113.2, the LFG

collection system shut down of individual wells would be limited by isolating and

abandoning a group of select LFG collection wells (up to five wells at a time) and

associated lateral manifold in accordance with the BAAQMD. A petition for variance to

allow temporary shutdown and/or abandonment of more than five wells at a time may

be made to the regulatory agencies during the Design Document Phase to allow for a

more expedited Site redevelopment schedule while ensuring protection of public health

and safety and the environment. The remaining LFG collection system would remain

fully operational to continue to mitigate LFG. A temporary above-ground manifold would

be installed and connected to the existing wells and the vacuum source for isolation and

abandonment of existing wells.

Health and Safety Requirements:

Health and safety measures will be needed for construction activities related to

abandonment and replacement of the LFG collection system. Specific HASPs will

be developed as part of the design phase. Health and safety measures will include,

but would not be limited to: weather monitoring stations, air monitoring for

methane, hydrogen sulfide, carbon monoxide, and VOCs, setting action levels for

each monitoring parameter, and specifications for PPE. Procedures to be followed

in case of emergency would also be identified. Temporary industrial fans will also be

used to supply dilution air for active work zones and to limit an increase in methane

levels in ambient air within the construction work zones. Methane monitoring will be

performed to limit the ambient methane concentration to less than 5% of LEL. If

methane concentrations reach 5% of LEL, aggressive venting measures would be

implemented. If the ambient methane concentrations reach 20% of LEL, then the

work area would be evacuated, until the methane concentration decreases below

20% of LEL.

Surface monitoring of methane emissions will be performed routinely. To comply

with the BAAQMD regulation 8-34-303, at no point on the landfill surface will the

methane concentration exceed 500 ppmv, expressed as methane above

background, other than non-repeatable, momentary readings. In case an increase in






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the surface emissions of methane is noted, the temporarily shut down wells will be

immediately connected to the existing process equipment using above-ground semi-

permanent piping and subsequently reactivated for LFG collection.

The health and safety measures related to the construction activities of the LFG

collection system will include use of interim measures for subsurface methane

collection in areas where existing LFG collection system will be shut down or

abandoned. The interim measures will include installation of the proposed full scale

permanent LFG extraction wells in the active work zone to provide continuous

methane extraction in the subsurface, because the existing LFG extraction wells

within the zone would be abandoned during the construction work. As an interim

measure, the proposed LFG extraction well heads would be modified for a

temporary connection to above-ground hoses (further connected to the process

equipment) to make the wells functional.

Coordination with the On-site Construction Work – The installation, mechanical and

electrical connections, startup, and testing of the proposed LFG collection system will

be coordinated with the Site development activities.

The field implementation plan will be executed by the following steps:

Modification at the Existing Process Equipment – A proposed LFG collection system

header manifold to connect to proposed main headers from each parcel will be installed

at the process equipment prior to construction activities.

Excavation at Parcel 3/6 – During excavation, the existing wells on Parcel 3/6 will be first

isolated using a proposed above-ground semi-permanent manifold connected to the

existing process equipment. Prior to the excavation, up to five wells in the excavation

area on Parcel 3/6 will be shutdown at a time (consistent with the BAAQMD regulation

8-34-117.4). During excavation activities, well risers of the shutdown wells will be cut

every 5 feet until proposed final grade is reached and then finished to the required grade

and will be connected to the above-ground semi-permanent piping and process

equipment. At the end of the excavation work, proposed above-grade semi-permanent

piping and manifold will be converted to the below-ground permanent piping and

manifold and the shut-off LFG collection wells will then be reactivated.






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Parcel Development - The following steps will be repeated in each parcel as the parcel

development begins and progresses:

Isolation of Existing LFG Collection Wells: Prior to construction in a parcel, all

existing LFG collection wells in that parcel will be isolated to ensure that

abandonment of the wells does not shut off the LFG equipment connection to the

rest of the LFG collection wells that are operational. Isolation will be limited to one

parcel at a given time and would require temporary system shutoff, installation of

proposed temporary above-ground manifold in each parcel, reconnection of groups

of existing wells to the temporary manifold, and turning on the process equipment.

Interim Measures for Grading and Development: Before the existing LFG collection

wells in an active work area are abandoned, proposed permanent LFG wells will be

installed. The wells will be temporarily connected to the existing LFG process

equipment using temporary above-ground hoses and manifold.

Abandonment of Existing LFG Collection Wells: Abandonment of existing LFG

collection wells will be limited to five wells at a time, consistent with BAAQMD

regulation 8-34-117.4. A petition for variance to allow temporary shutdown and/or

abandonment of more than five wells at a time may be made to the regulatory

agencies during the Design Document Phase. Well layout and manifold connections

that will be used for abandonment and the proposed preliminary sequence of well

abandonment are presented in Appendix K.

Installation of Proposed Condensate Knockout Pots and Piping: The proposed

condensate knockout pots and piping would be installed after grading, piles, and pile

caps installation as per the proposed layouts shown in Appendix K. The installation

of condensate knockout pots and piping will be coordinated with the installation of

the slab, as needed.

Permanent Connection to Existing Process Equipment: The proposed LFG and

condensate collection wells will be finished to the proposed grade. The LFG wells

and condensate knockout pots will be reconnected to the process equipment and

activated using hoses and manifold.






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Installation of proposed LFG collection system will be continued in all the parcels by repeating

the aforementioned steps. Once portions of the new LFG collection system have been

reconnected to the process equipment, system inspection, shakedown, and startup will be

performed. The proposed field implementation details are provided in Appendix K. Details of

the new LFG collection system, shakedown, and startup will be prepared during design phase

for review and authorization by the regulatory agencies prior to implementation.

9.5 LFG Collection System Monitoring Plan

As required by BAAQMB Regulation 8, Rule 34, CCR Title 27, and Synthetic Minor Operating

Permit (SMOP) condition 2935, Part 14:

Monthly monitoring of LFG collection well heads and LFG monitoring wells for vacuum,

temperature, and concentrations of methane, oxygen, carbon dioxide, nitrogen, and

VOCs.

Monthly monitoring of LFG collection system process equipment for vacuum, air flow

velocity, and methane (% Volume and % LEL).

Monthly monitoring of collection and control devices.

Quarterly component leak testing.

Quarterly hydrogen sulfide monitoring at system inlet.

Quarterly LFG migration monitoring.

Quarterly methane surface emission monitoring.

Continuous monitoring of flare temperature and gas flow at the flare and the

microturbines.

Annual flare and microturbines performance test, which will include monitoring for

sulfur, non-methane organic compounds, methane, oxides of nitrogen, carbon

monoxide, and VOCs.

Results of the above will be compiled and included in an annual report. System and individual

wellhead operation and downtime will also be recorded in the report.






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10.0 LANDFILL GAS CONTROL

Potential risk to inhabitants of the proposed development may be present related to intrusion of

LFG into the proposed new structures. As such, a LFGMS will be installed in general

accordance with CCR Title 27 §20937. The purpose of the LFGMS is to mitigate the potential

building occupants’ exposure to harmful compounds from the subsurface.

The LFGMS will consist of a VBM, combined with a horizontal vapor collection and venting

system installed below the VBM so that any soil vapors can migrate, and vent, to the

atmosphere, outside the building. The horizontal vapor collection system will be primarily

passively-driven, but will include a contingency active extraction component that may

supplement the passive system based on automated methane monitoring. Below-grade utility

conduits entering the building will be sealed to mitigate LFG from migrating along the conduits

from outside the building and into the sub-slab space beneath the building. These features are

described in greater detail in the following sections. The LFGMS design drawings are

presented in Appendix L.

10.1 Vapor Barrier Membrane

10.1.1 Platform Structure Area

A platform structure that is supported by pile foundations will be constructed for a majority of

the Parcel 4 development. Above the platform structure will be an interstitial space of

approximately 5 feet. Above the interstitial space will be the building first floor slab,

landscaping, or pavement, depending on the location. A minimum of 12 inches of crushed rock

will be placed on top of the structural slab within the interstitial space. A VBM will be installed

on top of the 12 inches of crushed rock. Depending of the type of VBM used, a carrier fabric

may be placed just beneath the VBM and/or the VBM may be covered by a protection course

layer (e.g. fabric), so that the VBM is not damaged during the subsequent construction of the

interstitial space. VBM will also be placed to seal the interstitial space at the perimeter of each

building. Vertical penetrations through the VBM are not expected because utilities are

expected to be placed within the interstitial space above the VBM. However, utilities crossing

the perimeter of the building footprints will penetrate the VBM and proper sealing of these

VBM penetrations are essential to maintaining the integrity of the VBM.






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10.1.2 Non-Platform Structure Area

A VBM will also be installed as described in Section 10.1.1 at specified locations throughout the

remainder of the development. Within parking structures outside of the platform structure

area, the VBM design is essentially the same as described above, except there will be no

interstitial space between the VBM and overlying parking surface. Re-evaluation of the need for

a VBM beneath parking structures may be considered based on the design of these structures.

For example, open-air parking structures may require VBM only installed beneath a portion of

the garage with enclosed areas on the first floor, based on an evaluation of fresh air exchange

within the open-air portions of the garage. Within other structures outside of the platform

structure area, the VBM design is essentially the same as described above for the platform

structure.

While penetrations of the VBM are not expected beneath buildings (because utilities are

expected to be placed within the interstitial space), slab penetrations may be necessary within

the parking structures. Proper sealing of slab penetrations is essential to maintaining the

integrity of the VBM.

10.2 Passive Vapor Collection and Venting System

10.2.1 Platform Structure Area

A passive, horizontal collection and venting system will be installed within the crushed rock

layer beneath the VBM, described in Section 10.1.1, throughout the entire footprint of the

platform structure. This system will collect potential LFG passing through the structural slab

and into the interstitial space, and vent those gases to atmosphere at the roof-level of buildings.

The system will include an interconnected network of 4-inch perforated SCH 40 PVC piping

embedded in the upper half of a 12-inch ‚blanket‛ of crushed rock. The piping network will be

connected to vertical riser pipes, constructed of cast iron or ductile iron pipe, which will trend

vertically to above the roof level, where they will each be capped with a wind turbine that will

generate a vacuum on the piping network to enhance collection and venting of the vapors. The

precise location of the collection and venting system is dependent on the foundation design

and below-grade utility line locations, and will require close coordination with other members of

the design team.

In general, sub-slab vapor collection piping will be spaced no further than 50 feet apart, and one

riser will be installed per 10,000 square feet of the building footprint. Each vertical riser will






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include a test port above the roof or near the bottom of the riser to allow for LFGMS

performance monitoring, if required. The exact location of the test port will be specified during

the Design Document phase based in part on accessibility to the riser pipes and monitoring

requirements. The collection piping spacing and riser frequency stated above should be

considered conceptual, with final determination at the discretion of the design engineer at the

time of design. This portion of the LFGMS is intended to operate entirely passively, with air

movement induced mainly by convection (‚chimney effect‛).

10.2.2 Areas Outside the Platform Structure

A passive, horizontal collection and venting system will be installed with the crushed rock layer

beneath the VBM under buildings and parking structures throughout the remainder of the

development. For those building and parking structures outside the platform structure, sub-

slab vapor collection piping will be spaced no further than 50 feet apart, and one riser will be

installed per 10,000 square feet of the building footprint. The collection piping spacing and riser

frequency stated above should be considered conceptual, with final determination at the

discretion of the design engineer at the time of design. Each vertical riser will include a test

port above the roof to allow for LFGMS performance monitoring, if required.

10.3 Exterior Grade Beam Inlet Vents

The purpose of the exterior grade beam inlet vents is to facilitate convective airflow up the

vertical riser pipe of the collection and venting system, by allowing fresh air to enter the vapor

collection layer beneath the VBM. The vent is constructed of solid PVC or cast iron pipe, and is

placed through the formwork prior to pouring the concrete. The use of check-valves or back-

flow preventers on the inlet vents to mitigate the possible release of landfill gas will be

evaluated during the Design Document phase based in part on the design of the interstitial

space and/or building slabs below which the LFGMS will be installed. The precise location of

the exterior grade beam vents, and the details of how they will be incorporated into the exterior

walls, or surrounding landscaping, will require close coordination with other members of the

design team, particularly the structural engineer and architect. The frequency of inlet vents will

be determined during final design.

10.4 Contingency Active Blower System

Due to potentially high concentrations of methane and VOCs in LFG, a contingency active

extraction system will be installed to supplement the passive collection system. Like the






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passive collection system, the active, blower-assisted collection system will be installed within

the 12-inch thick crushed rock layer above the entire platform slab and above the structural

slabs beneath buildings and parking structures throughout the remainder of the Site. The

purpose of this system is to force subsurface methane gas and vapors to the atmosphere

through the blowers located at roof level. The active system will function if methane levels are

detected at specified concentrations in the methane sensors as described in Section 10.5. The

blower will also be scheduled for routine (monthly) operation to prevent moisture buildup.

The contingency active collection network consists of solid and perforated PVC pipe that

provide a flow pathway for the collected vapors towards a cast iron pipe vertical riser which

transmits the gases collected from inside the gravel layer to the atmosphere above the roof

level. The perforated collection pipes will be sleeved with a geotextile fabric to prevent

accumulation of fines within the piping system. The riser pipe leads to a blower above the

building roofline. While activated, methane and vapors are collected mechanically.

The required blower vacuum ratings, which are presented on the design drawings in

Appendix L, were calculated considering the following vacuum parameters:

Calculated building-specific pressure losses through the piping network due to friction,

which is dependent on flow rate.

Maintaining a minimum of 10 inches of water of vacuum to pull vapors up to the blower

at roof level.

It is assumed the underlying LFG Collection System will not produce a vacuum within

the LFGMS venting layer, due to the presence of the structural slab between the two

systems.

Contingency blower collection piping will be placed in between the passive collection and vent

piping or at a spacing of 50 feet. The blower flow ratings are designed to flush one pore volume

of air through the 12-inch crushed rock layer every 40 minutes under occupied buildings, and

every 90 minutes under parking structures. The lower flushing rate under parking structures is

because these structures are considered a lower risk for vapor intrusion, due to the lower

duration of human occupancy and garage-space ventilation requirements. These frequencies of

pore volume flushing should be considered conceptual, with final determination at the






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discretion of the design engineer at the time of design. Large flow rate requirements greater

than 400 standard cubic feet per minute (scfm) should be accommodated by multiple blowers.

A backup power source will be provided to power the contingency active blower system in the

event of an outage or failure of the primary building power system.

10.5 Automatic Methane Sensor Network

A continuously operating, automatic methane sensor network will be installed within the

interstitial space of the platform slab and in the first floor of buildings throughout the Site. A

minimum of one methane sensor will be placed within enclosed spaces and the frequency of

sensors is presented on the drawings in Appendix L. Final sensor design locations will be based

in part on the room and HVAC configurations and area coverage. In addition, one methane

sensor will also be placed at the top and/or bottom (depending on Design Document details) of

each stairwell, elevator shaft or other vertical open area that originates at ground level. The

locations and frequencies of the methane sensors in the building are illustrated in the design

drawings (Appendix L). A backup power source will be provided to power methane sensors and

alarms in the event of an outage or failure of the primary building power system.

The methane sensor network shall include low level and fault alarms. An audible horn alarm

will sound during high alarm activation. The automatic methane sensor network will trigger the

following emergency alarms:

The low alarm activation will occur at 10% of the LEL of methane gas. The alarm

signal(s) will be sent to the rooftop controller to activate operation of the contingency

active blower system.

Fault alarm activation will occur at loss of sensor signal, loss of controller power, and/or

loss of sample draw on sensors using remote sampling technology. Upon fault alarm, a

signal will be sent to the building engineer to inspect/repair the system.

High alarm activation will occur at 25% of the LEL of methane gas and signals will be

sent to the fire alarm control panel (FACP). The FACP will activate building horn/strobes

at the Facility Engineering Office, and send an alarm to a 24-hour monitoring company

indicating a ‚25% LEL methane gas alarm.‛






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The methane trigger levels for the alarms described above should be considered conceptual,

with final determination at the discretion of the design engineer at the time of design. Methane

sensors located within the interstitial space may alarm at higher methane levels than for

methane sensors located in interior spaces.

Low alarm activation will result in the activation of the contingency active blower system,

which will mechanically clear methane gas that may have accumulated within the collection

layer of the LFGMS. The gases will be vented directly to the atmosphere above roof level. It is

assumed that the Santa Clara County Fire Department (SCCFD) will be present to observe the

start-up functions of the automatic methane monitoring system.

Automatic monitoring will not be installed for other constituents in landfill gas. Methane will

serve as an indicator compound for other non-methane organic compounds (NMOCs), such as

VOCs. For purposes of the automatic monitoring system and for that reason the NMOC need

not be separately automatically monitored. Manual VOC monitoring may be considered in the

event that elevated methane concentrations indicate that the LFGMS may not be operating

effectively. Manual VOC monitoring may also be considered in the event that VOC

concentrations exceed the risk-based concentrations goals established in the Feasibility Study

of Groundwater Remediation Alternatives (Langan, 2015d).

10.6 Construction Quality Assurance Manual

A Construction Quality Assurance (CQA) Manual for the LFGMS will be prepared prior to

installation as part of the Design Documents. The CQA Manual will outline measures required

for quality assurance testing of LFGMS components and for protection of the VBM during

installation and during subsequent activities performed prior to covering of the VBM. The CQA

Manual will address the following:

The frequency of construction administration performed by the design engineer to

observe and document that installation is being performed in accordance with the

design and specifications;

Coupon testing of the VBM during installation to verify the design membrane thickness;

Smoke testing of the VBM during installation to verify continuity of the VBM;

Placement of a protection course fabric onto the VBM for protection of the VBM;






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Measures for protection of the surface of the VBM during subsequent construction

activities and placement of utilities within the interstitial space.

11.0 LEACHATE COLLECTION AND REMOVAL SYSTEM

11.1 Existing LCR System

The existing LCR system is present only in Parcel 1NW and Parcel 3/6. The leachate recovery

systems in the two parcels are independent. The LCR system in each of these two parcels

consists of a network of parallel leachate collection drains set at the bottom of the refuse and

leachate collection sumps for leachate drainage. Parcel 3/6 also has a perimeter leachate

collection drain. The collection drains are perforated pipes set either in a trench or set above

subgrade. Both types of collection drains are covered with gravel or drain rock. The trenched

collection drains are covered with a drainage layer and the collection drains set above the

subgrade are set within the drainage layer. The leachate can be collected from the sumps using

leachate risers: LR-6, LR-7, LR-8, and LR-9 on Parcel 1NW, and LR-1, LR-3, and LR-4 on Parcel

3/6. In addition to these risers, six piezometers are spread over Parcels 1, 2, and 4. These

piezometers have very slow recharge rate and cannot be used to effectively recover leachate.

Currently, the leachate/groundwater is recovered only from LR-1 using an automated pump.

Approximately 150,000 gallons of leachate were collected from LR-1 in 2013 and discharged

directly into the sanitary sewer. Notable amounts of leachate have been historically recovered

from LR-3 and LR-4 on Parcel 3/6. Leachate has not been recovered from the risers at Parcel

1NW since 1998. The layout of the existing LCR drains, sumps, wells or risers, and additional

subsurface details are provided in Appendix A.

11.2 Proposed LCR System

The proposed plan for LCR system includes preserving and maintaining the operation of riser

LR-1 and LR-4 in Parcel 3/6. Similar to the existing LCR riser LR-1, a submersible LCR pump

and associated float switches (i.e., pressure transducers) will be installed at the bottom of LR-4

for automated leachate recovery. If during construction, LR-1 and/or LR-4 are damaged, repairs

and modification will be performed as needed. Similar to the existing LR-1 LCR system, the

leachate recovered from the future operational leachate risers (LR-1 and LR-4) will be

discharged to a sanitary sewer (pending permit approval).






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Existing groundwater wells will be monitored according to the monitoring program that will be

developed consistent with the RWQCB monitoring requirements. The support and anchoring of

LR-1 and LR-4, to prevent potential settlement would be developed once the Site plans and

foundation plans for Parcel 3/6 are finalized.

For Parcel 1NW, the existing system will not be preserved since leachate has not been

collected from the system since 1998 and groundwater quality beneath and adjacent to Parcel

1NW has not been significantly impacted.

The proposed LCR concept plan is based on the following evaluation and considerations:

Current leachate recovery rates;

Leachate and groundwater elevation comparison;

Groundwater and leachate chemistry data;

LCR system settlement analysis;

Potential impact of deep foundations on existing LCR system;

Anticipated leachate production rates;

Seismic hazards;

Corrosion impacts; and

State and local regulations.

Current Leachate Recovery Rates - Review of the January 2014 and July 2014 water quality

monitoring reports indicates that leachate is currently recovered only from one leachate riser,

LR-1 using an automated LCR system, while LCR from other leachate risers has been sporadic.

Last noted in 1998, leachate was recovered from LR-4 and in the January 2015 Site visit by

Langan, leachate was observed to be present in LR-4 and LR-1.

Leachate and Groundwater Elevation Comparison - Based on our preliminary review of the

leachate and surrounding groundwater elevation data (Appendix M), no notable difference

between the leachate and surrounding groundwater elevations is observed. Groundwater






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monitoring conducted by Golder Associates (February 2014) measured the groundwater table

at the Site between about Elevation -4 feet to 4 feet. Based on the available groundwater data

from previous reports, the groundwater table elevations are generally in or within 10 feet of the

bottom portion of the waste unit. This suggests that a distinct leachate layer within the waste

unit does not likely exist at a higher elevation than the regional groundwater elevation.

Groundwater and Leachate Chemistry Data - The groundwater and leachate chemistry data

comparison presented in Appendix M indicates that the chemistry of leachate extracted from

LR-1 is distinct and less impacted than the groundwater where the VOC plume has been

identified near Parcel 3/6 and Parcel 4. Furthermore, based on the February – March 2014

groundwater data collected at monitoring wells G-4R, G-5, H-7 and G-21, which are farther

downgradient of LR-1 (Parcel 3/6) and downgradient of Parcel 1NW, these wells show no

exceedances above ESLs for metals or VOCs. Thus, it is likely that leachate does not have a

significant impact on the groundwater at the Site.

Leachate Recovery System Settlement Analysis - The measured 1997 and 2003 elevations

of the leachate risers on Parcel 1NW and Parcel 3/6 were compared to estimate potential

settlement of the leachate risers (Appendix M). As expected, the leachate risers, which are

located in the landfill berm did not indicate significant settlement at the top or bottom of the

casing elevations.

In addition, preliminary settlement calculations were performed by Langan for Parcel 3/6 to

estimate the possible settlement in the underlying clay/native soil that could have resulted over

time due to the load of overlying refuse, soil cover, and soil stockpile. The results of the

settlement calculations are provided in Appendix M. A settlement of approximately 10 inches

was estimated in the center of the Parcel 3/6, while a settlement of approximately 3 inches

was estimated at the edges of the Parcel 3/6. Based on these settlement estimates, a

comparison evaluation was performed between the design (pre-construction) elevations of the

bottom of LCR risers and elevations after estimated settlement (Appendix M). The evaluation

shows that even after the estimated settlement at the center of Parcel 3/6, the relative

positions of the sump to riser connection and the bottom of risers LR-1, 3 and 4 would have not

been changed significantly, although the slope of the pipe laterals connecting the risers with

the sump might have been reduced. Given that the construction material used for the LCR

risers and pipe laterals at Parcel 3/6 was SCH 40 PVC (which is relatively more brittle and less






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flexible than HDPE), the deflection of pipe laterals might have caused damage to pipe, pipe

joints, or some of the riser connecting joints with pipe laterals.

Potential Impact of Deep Foundations on Existing LCR System - Construction of deep

foundations (e.g., advancing piles into the native soil underlying the refuse) may damage

potions of the existing LCR drains set at the bottom of refuse and associated sumps for

leachate drainage. Given that the leachate layer within the waste is consistent with the regional

groundwater elevation (i.e. leachate is not mounded within the waste) and the possibility that

the LCR pipe laterals at Parcel 3/6 might have already been damaged from the past differential

settlement of the subsurface soils, the existing LCR system may be collecting groundwater

along with leachate. It is anticipated that the potential future damage of the existing LCR

subsurface infrastructure (LCR drains and sumps) due to deep foundations construction

activities will not impact the effectiveness and performance of the LCR system. Therefore, a

significant effort for preserving, repairing, or rebuilding the LCR subsurface infrastructure is not

needed, rather, efforts to preserve the existing operable components of the LCR system in

Parcel 3/6 (leachate risers LR-1 and LR-4) are proposed.

Potential impacts of deep foundations on the proposed LCR system effectiveness and

performance will be further evaluated during the Design Document Phase.

Anticipated Leachate Production Rates - Leachate production in the developed parcels is

anticipated to be substantially reduced due to the proposed post-construction stormwater

management in combination with the proposed above ground impervious surface construction

(i.e., structural building pads, asphalt roadways, buildings, etc.), which would limit infiltration of

water into the refuse. In addition, the reduction in irrigation along with the proposed automated

condensate recovery and removal system for the new LFG collection system would also

reduce the amount of water infiltration into the refuse and consequently will reduce the amount

of leachate produced.

The proposed LCR system, presented in Appendix M, will meet the following state and local

regulations:

CCR Title 27, Chapter 3, Subchapter 5, Article 2, §21160 – Landfill gas control and

leachate contact.






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CCR Title 27, Chapter 3, Subchapter 2, Article 2, §20200(d) – Management of liquids at

landfills and waste piles.

CCR Title 27, Chapter 3, Subchapter 2, Article 4, §20340– Leachate collection and

removal systems.

RWQCB Waste Discharge Requirements (WDRs), as revised for the proposed

development.

11.3 Considerations for LCR System at the Site

The potential seismic hazards and potential corrosion impacts to the future LCR system will be

considered and evaluated during the Design Document Phase:

Seismic Hazards – A seismic hazard analysis will be conducted during the Design

Document Phase to evaluate potential seismic impacts on the LCR system. Based on

the results of the seismic analysis, the components of the LCR system (i.e., LR-1, LR-4

and associated manifold) will be modified to accommodate the anticipated seismically

induced settlements to the extent practical.

Corrosion Impacts – Both LFG and fluids can potentially cause corrosion of landfill

infrastructure (LFG collection and LCR system) and building infrastructure (slabs and

piles). To minimize the impact of corrosion on the new LCR system components (i.e.,

LR-1, LR-4 and associated submersible LCR pumps and manifold), critical units and

parts would be fabricated from corrosion resistant materials, including HDPE, PVC,

corrosion-resistant stainless steel, and other materials with corrosion resistant coatings.

11.4 Conceptual Field Implementation Plan

The preservation of the existing LCR risers LR-1 and LR-4 would be coordinated with the on-

site construction work. Health and safety measures would be needed for general construction

activities, including those related to the existing LCR system.

Health and Safety Measures - Specific health and safety plans would be developed as

part of the design phase. These health and safety measures would include, but would

not be limited to: weather monitoring stations, air monitoring for methane, hydrogen






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sulfide, carbon monoxide, and VOCs, setting action levels for each monitoring

parameter, and specifications for PPE.

Coordination with on-site Construction Work - The installation, mechanical and electrical

connections, startup, and testing of the proposed LCR system will be coordinated with

the Site development activities.

During excavation of soil stockpile materials overlying Parcel 3/6, the LCR risers LR-1

and LR-4 in Parcel 3/6 would be identified, flagged, cut and capped (secured) as the

excavation progresses and would be finished to the proposed grade at the end of the

excavation.

During the construction phase of Parcel development, the existing LCR risers LR-1 and

LR-4 in Parcel 3/6 would be protected and preserved during construction by flagging the

well heads location, extending the risers, and installing a bollard around each riser.

The preserved LCR risers LR-1 and LR-4 would be completed at the proposed finished

grade. A new submersible LCR pump and associated float switches (i.e., pressure

transducers) will be installed at the bottom of LR-4 for automated LCR. The existing

submersible LCR pump at LR-1 and associated controls will be tested and serviced, as

needed. The LCR risers LR-1 and LR-4 would be routed to the proposed double

contained leachate storage tank that is to be housed in the central process equipment

enclosure on Parcel 1NW from where it will be conveyed ultimately to a single manhole

location sanitary sewer by a transfer pump and associated piping.

11.5 LCR System Monitoring Plan

The LCR system will be checked as scheduled or required for potential damages from seismic

activities, corrosion, etc. The leachate will be extracted and discharged to the sanitary sewer

(pending permit approval).

The LCR system monitoring will be continued as per the monitoring plan issued by the RWQCB

in WDRs Order No. R2-2002-0008 for the Site (Adopted 23 January 2002), which will be revised

to consider the proposed development and modifications to the landfill systems. Leachate

extracted from LCR risers LR-1 and LR-4 will be sampled on a semi-annual basis and analyzed

for VOCs; select metals (i.e., arsenic, chromium, copper, iron, lead, nickel, and zinc); and the






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routine water quality parameters (i.e., chloride, nitrate plus nitrite as nitrogen, pH, electric

conductivity, unionized ammonia as nitrogen, and chemical oxygen demand). Prior to the

sampling activities, the field parameters temperature, electric conductivity, pH, dissolved

oxygen, turbidity, and oxidation reduction potential will be collected. Results of the sampling

will be compiled and included in a semi-annual report submitted to the RWQCB along with

documentation of the volume of leachate removed and method of disposal.

12.0 GROUNDWATER AND SURFACE WATER MONITORING

As required by the WDRs for the Site, groundwater and surface waters at and adjacent to the

Site will be monitored on a semi-annual basis:

Groundwater elevations will be measured from the 22 groundwater monitoring wells

and piezometers associated with the Site.

Groundwater from the 22 groundwater monitoring wells and piezometers associated

with the Site will be sampled and analyzed for VOCs; the metals arsenic, chromium,

copper, iron, lead, nickel, and zinc; and the routine water quality parameters chloride,

nitrate plus nitrate as nitrogen, pH, electric conductivity, unionized ammonia as nitrogen,

and chemical oxygen demand.

Surface waters from four selected surface water sampling locations along San Tomas

Creek and the eastern perimeter drainage ditch will also be analyzed for the above listed

parameters.

Prior to the sampling activities, the field parameters temperature, electric conductivity,

pH, dissolved oxygen, turbidity, and oxidation reduction potential will also be collected.

Results of the sampling will be compiled and included in a semi-annual report.

13.0 EMERGENCY RESPONSE

13.1 High Methane at Buildings

The automatic methane monitoring system within the first floor of the buildings is set with

these levels of alarm as described below:






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The low alarm activation shall occur at 10% of the LEL of methane gas. The alarm

signal(s) will be sent to the rooftop controller to activate operation of the contingency

active blower system.

Fault alarm activation shall occur at loss of sensor signal, loss of controller power, and/or

loss of sample draw on sensors using remote sampling technology. Upon fault alarm, a

signal will be sent to the Building Engineer to inspect/repair the system.

High alarm activation shall occur at 25% of the LEL of methane gas and signals will be

sent to the FACP, which will activate building horn/strobes at the Facility Engineering

Office, and send an alarm to a 24-hour monitoring company indicating a ‚25% LEL

methane gas alarm.‛

Table 4

Compliance Requirements - Methane Action Levels

Compliance Requirement

Percentage of Methane in

Air

LEL 5%

High Alarm Level - 25% LEL 1.25%

Low Alarm Level - 10% LEL 0.5%

In the event of an emergency, such that methane sensors indicate concentrations of methane

in excess of the high alarm level of 25% of the LEL specified in Table 4, the Building

Engineering Manager shall coordinate with the Santa Clara Fire Department approximate

actions and steps necessary to protect public health and safety and the environment. The

Building Engineering Manager will immediately notify the LEA by telephone or electronic

means.

Within one week following a LFG sensor alarm, the Building Manager will:

Verify validity of the alarm by reviewing sensor readings and possible interferences.

Record a description of and submit a letter to the LEA that describes:

The levels of methane and trace gas detected;






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A brief description of the nature and extent of the problem based on information

currently available;

The steps the operator has taken to protect public health and safety and the

environment; and

A brief description of further corrective actions that the operator or others need to

take to adequately protect public health and safety and the environment.

During an evacuation, the building will not be reoccupied until it has been confirmed and

approved by the Santa Clara Fire Department that: (1) concentrations of methane meet the

applicable compliance requirements; and that (2) the LFGMS system is operating in a manner

that ensures adequate control of methane/vapor intrusion.

13.2 Other Emergency Situation

Emergency services (i.e. 911) should be contacted in the event of an emergency such as a fire

or earthquake. During an evacuation, the buildings will not be reoccupied until it has been

confirmed and approved by the Santa Clara Fire Department that: (1) concentrations of

methane meet the applicable compliance requirements; and that (2) the LFGMS systems are

operating in a manner that ensures adequate control of methane/vapor intrusion.

After the risk of immediate danger has subsided:

Site-wide systems such as the landfill cover, LFG system, LFGMS, LCR system, and

groundwater monitoring work shall be inspected for damage and evaluated for

necessary repair; and

A designated Responsible Party will immediately notify the LEA by telephone or

electronic means.

After the damages, if any, have been assessed, the designated Responsible Party will record a

description of and submit a letter to the LEA that describes:

A brief description of the nature and extent of the problem based on information

currently available;






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The steps the operator has taken to protect public health and safety and the

environment; and

A brief description of further corrective actions that the operator or others need to take

to adequately protect public health and safety and the environment.

14.0 OPERATION AND MAINTENANCE PLAN

Ongoing Site maintenance is required following the construction of the proposed development

to maintain Site features (pavement, foundation, and landscaping) which compose the landfill

cap, drainage and storm water management features, LFG system, the LFGMS, and the LCR

system.

14.1 Final Cover Inspection and Maintenance

Post-construction maintenance activities to maintain Site features (pavement, foundation,

landscaping) which compose the landfill cap, will include inspection of landfill cover integrity

and landfill cover repairs as needed. Indications of a loss of integrity include, but are not limited

to: signs of erosion such as channels or rutting, presence of animal burrows, and cracking or

fissuring of pavement or foundations. A list of inspection items and frequency is provided in

Table 5.

Table 5

Compliance Requirements - Final Landfill Cover Maintenance

Inspection Item Frequency of Inspection

Landfill Cover Integrity

Signs of erosion such as channels or rutting

Perform quarterly Site

inspections; monthly

inspections during the wet-

weather season; subsequent to

an emergency event;

subsequent to any intrusive

work and/or repairs.

Presence of animal burrows

Presence of cracking or fissuring of pavement or

foundations that could cause a landfill gas odor release

Irregular condition of vegetation (irregular color or growth

deficiency)

Signs of settlement (depressions, ponded water)






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Drainage Features

Evidence of degradation of drainage features Perform quarterly Site

inspections; monthly

inspections during the wet-

weather season; subsequent to

an emergency event;

subsequent to any repairs..

Evidence of ponding or backup

Irregular condition of storm water (irregular color, odor,

clarity or turbidity, floating solids, settled solids,

suspended solids, foam, oil sheen, and other indications of

stormwater pollution)

Repairs necessary to restore the integrity of the final cover will be executed by the Site

personnel or an independent contractor as described below. Erosion damage which breaches

the cover layer will be repaired with suitable clean soil material. Temporary berms, ditches, and

straw mulch will be used to prevent further erosion damage to repaired areas until Site

conditions permit re-establishment of final cover and subsequent revegetation, as applicable.

Minor erosion and cracks will be repaired with bentonite. Minor erosion and cracks will be

widened, if necessary, to facilitate placing bentonite. The bentonite will be compacted using a

hand tamper or other appropriate equipment. Significant erosion, cracks, or areas with exposed

refuse will be repaired using clean, appropriate soil material which will be placed and

compacted to meet original final cover soil specifications. Repaired areas will be reseeded to

establish vegetation, as applicable. In paved areas, surfaces will be properly sealed.

In landscaped areas, the condition of vegetation will be monitored quarterly and monthly during

wet-weather season by the Site personnel or an independent contractor. Inspections will

identify areas of irregular color or growth deficiency. During future inspections, the spread of

these conditions will be noted. If an area greater than 500 square feet is noted to provide less

than 80% vegetative cover, the area will be hand seeded and fertilized to reestablish plant

growth.

Excessive LFG migration through the final cover could result in loss of vegetation. If noticeable

reoccurring vegetative loss is observed, a LFG detector will be utilized to determine the extent

of potential LFG migration. Screening with a LFG detector should be conducted on a wind-free

day. If necessary, repairs to the LFG system will be performed (see Section 14.3).

Areas that have ponded water or have settled will be filled to reestablish the proper grade.

These areas will be filled with clean soil, free of deleterious material. After filling and regrading,






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the areas will be reseeded. Should a slope failure occur, the area will be closed off to prevent

damage to equipment or harm to individuals. The Site's engineering consultant will be notified

to assess the failure and recommend appropriate corrective action. Specific corrective action

will be dependent on the extent, nature, and location of the failure. A record of final cover

maintenance activities will be kept by Site personnel or an independent contractor. The record

will include the date, location, and extent and nature of the maintenance activity. Regulatory

agencies will be notified if required by the Site's permits and approvals. The Site personnel or

an independent contractor will perform Site inspections.

14.2 Drainage Features Inspection and Maintenance

The Site will be inspected quarterly and monthly during the wet-weather season by the Site

personnel or an independent contractor for evidence of ponding or degradation of the Site's

drainage control system. Ponding on the lower portions of the Site will be remedied by either

backfilling the area to provide positive drainage, or providing an acceptable downstream slope

to an appropriate discharge point. The property perimeter will be inspected for failure. If

necessary, temporary repairs will be made until permanent repairs can be scheduled. Repairs

to drainage facilities will be completed by the Site personnel or a licensed general contractor.

14.3 LFG System Inspection and Maintenance

An examination of accessible portions of LFG system piping for potential system failures such

as leaks or breaks will be conducted on a monthly basis. Detection of a system failure which

would reduce system efficiency and/or effectiveness will be addressed within 24 hours of

detection. Preventative maintenance will be performed at manufacturer recommended

intervals. A LFG system operation and maintenance (O&M) manual will be prepared following

construction of the system and completion of record drawings. The LFG system O&M manual

will include a schedule of maintenance checks of accessible LFG system components (i.e.,

wellhead vaults, wellhead instrumentation and controls, condensate knockout pots, knockout

pot submersible pumps, process equipment, etc.).

14.4 LFGMS Inspection and Maintenance

Ongoing operation and maintenance of the LFGMS is required. The LFGMS must be

maintained by trained personnel who are familiar with the system’s operations. The system

components will be repaired or replaced for operational reliability as needed during routine






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maintenance periods. If building improvement plans (e.g., tenant improvements) impact

LFGMS components, portions of the LFGMS will be properly repaired. For such work, proper

safety measures will be implemented (including gas and vapor monitoring and control). Agency

Notification and reporting to the applicable agencies (i.e. LEA and RWQCB) is required. A

LFGMS O&M manual will be prepared following construction of the LFGMS and completion of

record drawings. The LFGMS O&M manual will include a schedule of maintenance checks of

above-ground LFGMS components, including testing and calibration of the methane sensor

network. The LFGMS O&M manual will also include provisions for protection of the VBM

during future utility maintenance work.

14.5 LCR System Inspection and Maintenance

Ongoing operation and maintenance of the LCR system is required. Inspections of the system

will be conducted by the Site personnel or an independent contractor whenever leachate is

sampled. A LCR system O&M manual will be prepared following construction of the LCR

system and completion of record drawings. The LCR system O&M manual will include a

schedule of maintenance checks of all above-ground and accessible LCR system components

(i.e., LCR risers LR-1 and LR-4, and associated submersible pumps and float switches, etc.).

14.6 Groundwater Monitoring System Inspection and Maintenance

Groundwater monitoring wells will be inspected for signs of failure or deterioration during each

sampling event. If damage is discovered, the well will be replaced or repaired as determined

by a California-registered geologist or certified engineering geologist. Possible repairs include

redevelopment, chemical treatment, partial casing replacement, resealing the annulus, or

pumping and testing. If a well is replaced, the existing, damaged well will be appropriately

decommissioned according to the California Well Standards guidelines for well destruction.

New wells will also be installed in accordance with California Well Standards guidelines.

14.7 Reporting

Results of monthly inspections, quarterly inspections, and a summary of maintenance

performed to the systems discussed in Sections 14.1 through 14.6 will be compiled and

included in quarterly monitoring reports.






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14.8 Planned or Emergency Subsurface Activities

Waste management is required for future, planned or emergency, subsurface activities.

Because the entire Site is anticipated to be capped, exposure pathways to Site tenants and the

public from material that may remain in the subsurface will have been mitigated. Responsible

parties will be required to inspect and maintain the integrity of the cap and provide notification

of activities that disturb the cap and measures performed to mitigate the disturbance. Post-

construction activities which could threaten the integrity of the cap include construction of new

buildings, installation of underground utilities or tanks, excavation below the cap, and

emergency activities, such as repair of broken underground utilities. Post-construction waste

management for subsurface activities may include restoration of the cap, dust and vapor

monitoring and control, and agency notification and reporting.

15.0 SATISFACTION OF POST-CLOSURE LAND USE REQUIREMENTS

The information set forth in this PCLUP above satisfies each of the specific requirements of 27

CCR 21190, and supports the agency findings required by that Section. As such, the proposed

post-closure land uses shall be designed and maintained to:

Protect public health and safety and prevent damage to structures, roads, utilities, and

gas monitoring and control systems (see Section 1.5.4 – Human Health Risk

Assessment and Section 3.3 – Health and Safety Program);

Prevent public contact with waste, LFG and leachate (see Section 6.0 – Final Cover,

Section 10.0 Landfill Gas Control, and Section 11.0 – Leachate Collection and Removal

System

Prevent LFG explosions (see Section 9.0 - Enhanced Landfill Gas Collection and

Remediation System); and

Maintain the integrity of the final cover, drainage and erosion control systems, and gas

monitoring and control systems (see Section 14.0 – Operation and Maintenance Plan).






September 2015

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Page 82

Construction of structural improvements at the Landfill will meet the following conditions:

Automatic methane gas sensors, designed to trigger an audible alarm when methane

concentrations are detected, will be installed in all buildings (see Section 10.0 - Landfill

Gas Control);

Enclosed basement construction will be prohibited (see Section 1.4 – Project

Description);

Buildings will be constructed to mitigate the effects of gas accumulation, which may

include an active gas collection or passive vent systems (see Section 10.0 - Landfill Gas

Control);

Buildings and utilities will be constructed to mitigate the effects of differential

settlement. All utility connections will be designed with flexible connections and utility

collars (see Section 5.0 – Conceptual Foundation and Section 8.0 – Utilities);

Utilities will not be installed in or below any low permeability layer of final cover (see

Section 5.0 – Conceptual Foundation and Section 8.0 – Utilities);

Pilings will not be installed in or through any bottom liner unless approved by the

RWQCB, or if pilings are installed in or through the low permeability layer of final cover,

then the low permeability layer will be replaced or repaired (see Section 5.0 –

Conceptual Foundation); and

Periodic methane gas monitoring will be conducted inside all buildings and underground

utilities (see Section 10.5 - Automatic Methane Sensor Network).

The City of Santa Clara is the lead agency preparing a Draft Environmental Impact Report (EIR)

on the Project in accordance with the California Environmental Quality Act (CEQA). A Notice of

Preparation for this EIR was published on July 30, 2014. The City is expected to complete the

Final EIR in late 2015. After the final EIR is certified, the LEA and RWQCB will consider

approval of this PCLUP in reliance on the CEQA analysis in the Final EIR.






September 2015

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Page 83

16.0 REFERENCES

Air Science Technologies, Inc., 2012. 2012 Source Test Report. Source Test of a Landfill Gas

Flare and Landfill Gas Characterization. Santa Clara All Purpose Landfill, Santa Clara, California.

Facility Number A3464. 20 July.

California Emergency Agency. 2009. Tsunami Inundation Map for Emergency Planning, State of

California, County of Santa Clara, Milpitas Quadrangle.

Edil, T.B., et al., 1990. Settlement of Municipal Refuse, Geotechnics of Waste Fills – Theory

and Practice, ASTM STP 1070, Philadelphia.

Emcon Associates (Emcon), 1988. Air Quality Solid Waste Assessment Test Report, City of

Santa Clara Landfill, Santa Clara County, California. December

Emcon, 1992. Final Closure and Postclosure Maintenance Plan, City of Santa Clara, All Purpose

Sanitary Landfill, Revision 2. 2 December.

Gibson, R.E., and Lo, K.Y., 1961. A Theory of Soils Exhibiting Secondary Compression, Acta

Polytechnica Scandinavica.

Golder Associates (Golder), 2013. Postclosure Maintenance Plan Update, City of Santa Clara,

All Purpose Landfill, SWIS No. 43-AO-0001, Waste Discharge Requirements Order, No. R2-

2002-0008. 23 August.

Golder, 2014a. BAAQMD Annual 8-34 Report, City of Santa Clara All Purpose Landfill, July 1,

2013 through June 30, 2014. 24 July.

Golder, 2014b. City of Santa Clara All Purpose Landfill, First Semiannual 2014 Self-Monitoring

Program Report. July.

Golder, 2015. Telephone communication with Steve Nguyen. 24 March.

Kenneth D. Schmidt and Associates (KSA), 1988. Results of the Water Part of the Solid Waste

Assessment Test at the City of Santa Clara Landfill. 29 June.

Langan, 2014a. Draft Work Plan for Landfill Gas Characterization, Related Santa, Santa Clara,

California. 13 February.






September 2015

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Page 84

Langan, 2014b. Work Plan, Geotechnical Field Investigation, Santa Clara All-Purpose Landfill,

Santa Clara, California. 5 March.

Langan, 2014c. Preliminary Geotechnical Investigation, City Place Santa Clara, Santa Clara,

California. 22 August.

Langan, 201d. Work Plan for Targeted Site Characterization, Santa Clara All Purpose Landfill,

Santa Clara, California. 26 September.

Langan, 2014e. Draft Site Investigation and Environmental Risk Assessment, City Place Santa

Clara, Santa Clara, California. 23 December.

Langan, 2015a. Draft Technical Memorandum, Enhanced Landfill Gas Collection and

Remediation System Reconstruction Concept Plans, City Place Santa Clara. 30 January.

Langan, 2015b. Draft Technical Memorandum, Leachate Collection and Removal System

Concept Plans, City Place Santa Clara. 6 February.

Langan, 2015c. Landfill Cover Investigation, City Place Santa Clara, Santa Clara, California. 13

February.

Langan, 2015d. Feasibility Study of Groundwater Remediation Alternatives, City Place Santa

Clara/Santa Clara All Purpose Landfill Site, Santa Clara, California. 21 July.

Real Environmental Products, 2011. Santa Clara Landfill, Landfill Gas Recovery System. Santa

Clara, California. 28 April.

Related, in conjunction with Elkus Manfredi Architects and RTKL, 2014. Conceptual Land Use

Plans and Programs. March.

Regional Water Quality Control Board San Francisco Bay Region (RWQCB), 2002. Order No.

R2-2002-0008 Updated Waste Discharge Requirements and Rescission of Order No. 94-050

for: City Of Santa Clara Santa Clara All Purpose Landfill Santa Clara, Santa Clara County. 23

January.

RWQCB, 2013. Cover Memo, User’s Guide: Derivation and Application of Environmental

Screening Levels, and Lookup Tables. December.






September 2015

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Page 85

RWQCB, 2014a. Response Letter to the Draft Work Plan for Landfill Gas Characterization for

City of Santa Clara - All Purpose Landfill. 21 March.

RWQCB, 2014b. Concurrence Letter for the Work Plan for the Geotechnical Field Investigation

Work Plan, City of Santa Clara - All Purpose Landfill. 10 July.

RWQCB, 2014c. Concurrence Letter for the Work Plan for Targeted Site Characterization for

City of Santa Clara - All Purpose Landfill. 1 October.

Sharma, H.D., and Lewis, S.P., 1994. Waste Containment Systems, Waste Stabilization, and

Landfills, Design and Evaluation. John Wiley & Sons, Inc.

Tokimatsu and Seed, 1987. Simplified Procedure for the Evaluation of Settlements in Clean

Sand.

FIGURES

APPENDIX A

EXISTING SYSTEMS

APPENDIX B

PHASING CONCEPT MAP (ELKUS MANFREDI ARCHITECTS

16 JULY 2014)

APPENDIX C

PRELIMINARY ARCHITECTURAL DRAWINGS

(PENDING PREPARATION)

APPENDIX D

PRELIMINARY DESIGN DRAWINGS

APPENDIX E

PREVIOUS ENVIRONMENTAL INVESTIGATION RESULTS (FIGURES

AND TABLES FROM DRAFT SITE INVESTIGATION AND

ENVIRONMENTAL RISK ASSESSMENT REPORT, CITY PLACE SANTA

CLARA, LANGAN TREADWELL ROLLO, 23 DECEMBER 2014)

APPENDIX F

EXISTING PERMITS

APPENDIX G

BORING LOGS AND CROSS SECTIONS

APPENDIX H

WASTE MANAGEMENT PLAN

APPENDIX I

ODOR MANAGEMENT PLAN

APPENDIX J

CONCEPTUAL FOUNDATION PLAN AND DETAILS AND DRAFT

LANDFILL COVER INVESTIGATION REPORT

APPENDIX K

PROPOSED LANDFILL GAS COLLECTION AND REMEDIATION

SYSTEM CONCEPT PLANS (FIGURES FROM DRAFT TECHNICAL

MEMORANDUM, ENHANCED LANDFILL GAS COLLECTION AND

REMEDIATION SYSTEM RECONSTRUCTION CONCEPT PLANS, CITY

PLACE SANTA CLARA, 30 JANUARY 2015)

APPENDIX L

CONCEPTUAL LANDFILL GAS MITIGATION SYSTEM DESIGN

APPENDIX M

LEACHATE COLLECTION AND REMOVAL SYSTEM CONCEPT PLAN

(FIGURE FROM DRAFT TECHNICAL MEMORANDUM, LEACHATE

COLLECTION AND REMOVAL SYSTEM CONCEPT PLANS, CITY PLACE

SANTA CLARA, 6 FEBRUARY 2015)

City PlaceSanta ClaraCity Place

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Project Drawing Title

SANTA CLARA CALIFORNIA

SITE MAP

Project No.

Date

Scale

Drawn By

Submission Date

Figure770611601

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CSS

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4030 Moorpark Avenue, Suite 210San Jose, CA 95117-1849

T: 408.551.6700 F: 408.551.0344 www.langan.com

CITY PLACESANTA CLARA

SANTA CLARA

2Langan Engineering & Environmental Services, Inc.Langan Engineering, Environmental, Surveying and

Landscape Architecture, D.P.C.Langan International LLC

Collectively known as Langan

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