big lake wastewater treatment facility expansion environmental

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ENVIRONMENTAL ASSESSMENT WORKSHEET Note to reviewers: The Environmental Assessment Worksheet (EAW) provides information about a project that may have the potential for significant environmental effects. This EAW was prepared by the Minnesota Pollution Control Agency (MPCA), acting as the Responsible Governmental Unit (RGU), to determine whether an Environmental Impact Statement (EIS) should be prepared. The project proposer supplied reasonably accessible data for, but did not complete the final worksheet. Comments on the EAW must be submitted to the MPCA during the 30-day comment period which begins with notice of the availability of the EAW in the Minnesota Environmental Quality Board (EQB) Monitor. Comments on the EAW should address the accuracy and completeness of information, potential impacts that are reasonably expected to occur that warrant further investigation, and the need for an EIS. A copy of the EAW may be obtained from the MPCA by calling (651) 297-8510. An electronic version of the completed EAW is available at the MPCA Web site http://www.pca.state.mn.us/news/eaw/index.html#open-eaw. 1. Project Title: Big Lake Wastewater Treatment Facility Expansion 2. Proposer: City of Big Lake 3. RGU: Minnesota Pollution Control Agency Contact Person Brad DeWolf Contact Person Debra Moynihan and Title City Engineer and Title Project Manager Address 160 Lake Street North Address 520 Lafayette Road North Big Lake, Minnesota 55309 St. Paul, Minnesota 55155 Phone (612) 756-1032 Phone (651) 296-8420 Fax (763) 263-0133 Fax (651) 297-2343 4. Reason for EAW Preparation:

EIS Scoping

Mandatory EAW

X

Citizen Petition

RGU Discretion

Proposer Volunteered

If EAW or EIS is mandatory give EQB rule category subpart number and name: Minn. R. 4410.4300,

subp. 18B 5. Project Location: County Sherburne City/Twp Big Lake Township SE 1/4 SW 1/4 Section 31 Township T33N Range R27W

Figures, and Appendices attached to the EAW: Figure 1 - County map showing the general location of the project; Figure 2 - United States Geological Survey (USGS) 7.5 minute, 1:24,000 scale map indicating project boundaries; Figure 3 - Site plan showing existing and proposed treatment units; Appendix 1 – Minnesota Department of Natural Resources (DNR) Natural Heritage and Nongame Research Program Response Letter; and Appendix 2 – Minnesota Historical Society State Historic Preservation Office (SHPO) Response Letter and

Summary of the Archeological Reconnaissance Survey.

http://www.pca.state.mn.us/news/eaw/index.html#open-eaw

Big Lake Wastewater Treatment Facility Expansion Environmental Assessment Big Lake, Minnesota 2 Worksheet

6. Description:

a. Provide a project summary of 50 words or less to be published in the EQB Monitor. The city of Big Lake (City) is proposing an expansion of their existing wastewater treatment facility (WWTF) to treat an average wet weather (AWW) design flow of 2.19 million gallons per day (mgd). The expansion will occur on the site of the existing WWTF and continue to discharge to the Mississippi River. Currently, the facility has an AWW design flow of 0.840 mgd.

b. Give a complete description of the proposed project and related new construction. Attach additional sheets as necessary. Emphasize construction, operation methods and features that will cause physical manipulation of the environment or will produce wastes. Include modifications to existing equipment or industrial processes and significant demolition, removal or remodeling of existing structures. Indicate the timing and duration of construction activities. Background The existing WWTF consists of a lift station with a fine screen, parallel eight-inch and 12-inch force mains approximately 7,900 feet long, a selector tank, two oxidation ditches, three final clarifiers, an ultraviolet (UV) disinfection system, and an outfall pipe. The facility also has solids handling units consisting of two sludge thickeners, an aerobic digester, and a biosolids storage tank. The design flows for the existing facility are 0.840 mgd for the AWW flow and 0.709 mgd for the average dry weather (ADW) flow. The treated effluent discharges to the Mississippi River in a portion of the river that was designated an Outstanding Resource Value Water (ORVW) on November 5, 1984. Improvements to the WWTF were made in 1996 and 1999. The 1996 improvements consisted if upgrading the biosolids handling facility. The existing biosolids holding tanks were modified into gravity biosolids thickeners and the heated aerobic digester and a 500,000-gallon biosolids storage tank were added. The 1999 improvements consisted of adding additional pumps and a fine screen to the main lift station, adding a new force main, adding a new selector tank ahead of the oxidation ditches, one new oxidation ditch, three new clarifiers, additional biosolids pumps, and new UV disinfection. The existing WWTF has been performing well; however, it does not have the capacity to handle the projected increase in flows and loadings. In addition, the existing WWTF will not be able to meet the more stringent discharge limits that will be required in the future. Proposed Expansion The City proposes to expand the existing WWTF to an AWW design flow capacity of 2.19 mgd, and an ADW flow capacity of 1.96 mgd. The existing facilities will continue to be used to treat wastewater during construction and after the expansion is complete. Construction will include new preliminary treatment facilities, biological phosphorus removal selector basins, two oxidation ditches, two new final clarifiers, expansion of the UV disinfection facility, new tertiary filters and new Class A biosolids treatment and storage facilities. The site of the existing WWTF has room for the proposed improvements. It is expected that site construction will be completed on approximately 8.0 acres of land. Since the WWTF’s discharge is to an ORVW, the City has opted to have the facility designed to freeze the mass loadings of pollutants to that of the November 5, 1984, discharge levels. Each of the major improvements is further described as follows:


Preliminary Treatment Facilities The new preliminary treatment facilities would consist of mechanical screening equipment and a controlled velocity grit removal system. The wastewater flow would be measured and 24-hour composite influent flow samples taken at the preliminary treatment facility. Selector Basin – Biological Phosphorus Removal After preliminary treatment, the wastewater would be split into the existing selector basin and a new selector basin. The selector basin provides the environment to grow certain micro-organisms and will be used for biological phosphorus removal. Each basin would have a mechanical mixer, baffle walls, and process piping. A chemical feed system will also be installed for back-up phosphorus removal in the final clarifier. Oxidation ditches The flow from the existing selector basin would be directed into the two existing oxidation ditches. Two new oxidation ditches would be constructed and receive flow from the new selector basin. Similar brush aeration rotor equipment would be supplied for the new ditches. Clarifiers The flow from the existing oxidation ditches would continue to go to the three existing clarifiers. The flow from the new oxidation ditches would be directed into two new clarifiers. Since the existing clarifiers have been designed to add a fourth clarifier, this clarifier would be added to allow for reliability and flexibility in the use of all the clarifiers with the existing and new oxidation ditches. Filtration The City is planning on using membrane filters to remove very fine particles from the wastewater. Membrane technology uses pressure to drive water through very small (approximately 0.1 micron) openings. By using this filtration technology, the City shall maintain the existing mass loading limits to the Mississippi River. Disinfection The existing UV disinfection system would be expanded to handle the increase in flow volume. Biosolids The City has decided to treat the solids removed from the wastewater to meet the Class A “Exceptional Quality Sewage Sludge” standards. The biosolids would be stored from the clarifiers, then dewatered prior to entering a drying process, producing a “dry” product which is approximately 50 percent solids. After treatment, the biosolids would be stored for final disposal.

c. Explain the project purpose; if the project will be carried out by a governmental unit, explain the need for the project and identify its beneficiaries.

The population served by the WWTF is expected to grow in the next ten years, and the existing WWTF will be quickly approaching design capacity. The purpose of the project is to provide a reliable means to treat wastewater generated by the City today and in the future. The expanded WWTF would be capable of meeting the City’s growing needs, while protecting the Mississippi River, which is dedicated as an ORVW by the state of Minnesota. The City intends to protect this valuable resource by meeting the strict discharge limits and adopting MPCA recommended ordinances to limit nonpoint sources of pollution from stormwater. The beneficiaries of this project would be the current and future residents of the City, and the current and future commercial users located in the City.


d. Are future stages of this development including development on any outlots planned or likely to happen?

Yes No If yes, briefly describe future stages, relationship to present project, timeline and plans for environmental review.

e. Is this project a subsequent stage of an earlier project? Yes No If yes, briefly describe the past development, timeline and any past environmental review.

Environmental review was conducted during the summer of 1997 for the 1999 expansion of the WWTF. The MPCA was the RGU for the project and issued a negative declaration on the need for an EIS on September 30, 1997.

7. Project Magnitude Data Total Project Area (acres) 8.0 or Length (miles) Number of Residential Units: Unattached N/A Attached maximum units per building Commercial/Industrial/Institutional Building Area (gross floor space): total square feet Indicate area of specific uses (in square feet): Office N/A Manufacturing N/A Retail N/A Other Industrial N/A Warehouse N/A Institutional N/A Light Industrial N/A Agricultural N/A Other Commercial (WWTP) 348,480 Building height 20’ (max) If over 2 stories, compare to heights of nearby buildings 8. Permits and approvals required. List all known local, state and federal permits, approvals and financial

assistance for the project. Include modifications of any existing permits, governmental review of plans, and all direct and indirect forms of public financial assistance including bond guarantees, Tax Increment Financing and infrastructure.

Unit of Government Type of Application Status MPCA Facility Plan Approval Submitted MPCA Nondegradation to an ORVW Review Submitted MPCA National Pollutant Discharge Elimination

System (NPDES)/State Disposal System (SDS) Surface Water Discharge Permit

Submitted

MPCA Plans/Specifications Approval To be submitted MPCA NPDES General Stormwater Permit for

Construction Activity To be submitted

Public Facilities Authority Funding Application Submitted Sherburne County Conditional Use Permit To be submitted

9. Land use. Describe current and recent past land use and development on the site and on adjacent lands. Discuss project compatibility with adjacent and nearby land uses. Indicate whether any potential conflicts involve environmental matters. Identify any potential environmental hazards due to past site uses, such as soil contamination or abandoned storage tanks, or proximity to nearby hazardous liquid or gas pipelines. The site of the existing Big Lake WWTF has room for the proposed improvements. The improvements will expand the fenced area of the WWTF. The City has purchased the adjacent property to facilitate this


expansion. Expansion of the plant is proposed to occur to the east. Current land use is open field and farmland. The proposed site is currently zoned by Sherburne County as agricultural. The surrounding area to the north and east is primarily agricultural. Approximately 1,000 feet to the west of the existing site is a demolition landfill, and to the south is the Mississippi River, located approximately 250 feet away. The closest residential building is approximately 750 feet away and southwest of the existing site. There is residential development located east of the WWTF site that is just under one-half mile away, and another residential development located southwest on the river a little over one-half mile from the WWTF. The odors associated with this WWTF would not increase as a result of the expansion. The addition of Class A sludge treatment facilities should help to reduce the overall odors generated at the site. Current zoning of the area is for agricultural land; however, as the City grows, the zoning of the area could change to commercial or residential. Due to the layout of the WWTP property, new homes and businesses will not be closer than 750 feet to existing or future processes. There are no indications of soil contamination, storage tanks, or environmental hazards due to past site use in the area of the WWTF.

10. Cover Types. Estimate the acreage of the site with each of the following cover types before and after development:

Before After Before After Types 1-8 wetlands 0.1 0.1 Lawn/landscaping 2.8 4.1 Wooded/forest Impervious Surfaces 0.1 0.3 Brush/grassland Other (describe) 0.5* 1.5* Cropland 4.5 2.0 TOTAL 8.0 8.0

*Two new oxidation ditches. 11. Fish, Wildlife, and Ecologically Sensitive Resources. a. Identify fish and wildlife resources and habitats on or near the site and describe how they would be

affected by the project. Describe any measures to be taken to minimize or avoid impacts.

Since the expansion of the WWTF would occur on and adjacent to the site of the existing facility, the proposed project is not expected to cause significant impacts to wildlife in the area. Areas beyond the construction zone should not be significantly affected by the project. Construction of the improvements will take approximately 540 days to complete. Since the existing outfall structure would be used, there would be no adverse impacts to the receiving water resulting from construction activities on the outfall. The expanded WWTF would continue to discharge to the Mississippi River, designated as an ORVW. The City has opted to accept more stringent effluent limits and freeze the pollutant mass loadings to the receiving water. The WWTF would continue to use UV disinfection, eliminating any concerns about chlorine toxicity. The proposed expansion will place the Big Lake WWTF into the classification of a “major” discharger under the NPDES/SDS Permit Program. As a major discharger, the City will be required to conduct aquatic life toxicity evaluations of the effluent as a condition of their NPDES Permit.


The Mississippi River reach between the Clearwater River and the Elk River is on the 2004 MPCA (Clean Water Act Section 303d) Total Maximum Daily Load (TMDL) List of Impaired Waters for fecal coliform, impaired biota, and mercury (fish consumption advisory). See section 18 for further discussion on impacts to the receiving water.

b. Are any state (endangered or threatened) species, rare plant communities or other sensitive ecological resources such as native prairie habitat, colonial water bird nesting colonies or regionally rare plant communities on or near the site? Yes No

If yes, describe the resource and how it would be affected by the project. Indicate if a site survey of the resources has been conducted and describe the results. If the DNR Natural Heritage and Nongame

Research program has been contacted give the correspondence reference number. ERDB 19970414-0004

Describe measures to minimize or avoid adverse impacts. The DNR Natural Heritage and Nongame Research program was contacted to determine if any rare plant or animal species or other significant natural features are known to occur within an approximate one-mile radius of the project. The review found documentation of a Bald Eagle nest site a little over a quarter-mile east of the project site. However, the DNR letter states that staff do not expect the project to affect any known occurrences of rare features due to the nature and location of the proposed facility expansion. A copy of the DNR response letter is provided as Appendix 1.

12. Physical Impacts on Water Resources. Will the project involve the physical or hydrologic alteration

(dredging, filling, stream diversion, outfall structure, diking, and impoundment) of any surface waters such as a lake, pond, wetland, stream or drainage ditch? Yes No If yes, identify water resource affected. Describe alternatives considered and proposed mitigation measures to minimize impacts. Give the DNR Protected Waters Inventory (PWI) number(s) if the water resources affected are on the PWI. A small (0.1-acre) wetland is located within a deep depression near the driveway entering the WWTF site on the west side. The location of the wetland is such that it will not be disturbed by construction of the improvements to the WWTF. The NPDES General Stormwater Permit for Construction Activity will require the implementation of Best Management Practices (BMPs) to protect any water resources near the project from adverse impacts due to construction activities. There will be no need for improvements to the existing outfall structure.

13. Water Use. Will the project involve installation or abandonment of any water wells, connection to or changes in any public water supply or appropriation of any ground or surface water (including dewatering)? Yes No If yes, as applicable, give location and purpose of any new wells; public supply affected, changes to be made, and water quantities to be used; the source, duration, quantity and purpose of any appropriations; and unique well numbers and DNR appropriation permit numbers, if known. Identify any existing and new wells on the site map. If there are no wells known on site, explain methodology used to determine.

14. Water-related land use management districts. Does any part of the project involve a shoreland zoning district, a delineated 100-year flood plain, or a state or federally designated wild or scenic river land use district? Yes No If yes, identify the district and discuss project compatibility with district land use restrictions. The site is located on high ground, approximately 20-25 feet above the 100-year flood plain.

15. Water Surface Use. Will the project change the number or type of watercraft on any water body?


Yes No If yes, indicate the current and projected watercraft usage and discuss any potential overcrowding or conflicts with other uses.

16. Erosion and Sedimentation. Give the acreage to be graded or excavated and the cubic yards of soil to be moved: 5.7 acres; ~ 30,000 cubic yards. Describe any steep slopes or highly erodible soils and identify them on the site map. Describe any erosion and sedimentation control measures to be used during and after project construction.

Soil borings will be done and a topographical survey was done on the site to determine soil type and bearing capacity, as well as preliminary layout of the process structures. No steep slopes or highly erodible soils were identified on the site. All soils excavated during construction of the facilities will be redistributed on the site. It is expected that site construction will be completed on approximately 8.0 acres of land.

The City will be required to obtain an NPDES General Stormwater Permit for Construction Activity from the MPCA to control erosion and runoff during construction. This permit must be obtained prior to commencing any land-disturbing activities (i.e., clearing, grading, filling, and excavating) at the site. The permit specifically requires implementation of BMPs. Erosion control measures will be used during and after construction to prevent sedimentation off the proposed site. Bale checks, silt fences, and ground mats will be used to slow runoff. Erosion control measures will be in place until turf is re-established on graded slopes and areas. Runoff controls will be considered in the design. Slopes would be graded at a maximum ratio of 3:1, with turf to prevent long-term erosion. Buffer strips will be maintained between drainage swales and impervious surfaces to prevent high velocity runoff situations.

17. Water Quality – Surface-water Runoff. a. Compare the quantity and quality of site runoff before and after the project. Describe permanent

controls to manage or treat runoff. Describe any storm-water pollution prevention plans.

There will be little change in the quantity and quality of runoff from the site due to the expansion. After completion of construction of the improvements, the impervious surfaces on the site will increase approximately 0.2 acres for a total of 0.3 acres. The addition of impervious surfaces will be building roofs and additional paved roads. Buffer strips will be maintained between the new landscaped area and where the runoff leaves the property. The NPDES General Stormwater Permit for Construction Activity has specific requirements for the treatment and overall management of stormwater discharged from the site. The permit requires the development of BMPs and a Stormwater Pollution Prevention Plan (SWPPP) to manage pollutants in stormwater runoff from the site that would occur during construction and after construction is complete. SWPPP and BMP implementation strategies must be prepared prior to submitting the permit application form.


b. Identify routes and receiving water bodies for runoff from the site; include major downstream water

bodies as well as the immediate receiving waters. Estimate impact runoff on the quality of receiving waters.

Runoff from the site could potentially enter the Mississippi River via overland flow similar to the current flow pattern for the site. Permanent buffer strips will be used to control the quantity and quality of the runoff water as it flows towards the river. The down-sloped area between the site of the WWTF and the Mississippi River has been left as natural woodland and brush cover, which serves to further buffer the river from stormwater runoff. No impact to the Mississippi River is expected due to the runoff from the site.

18. Water Quality – Wastewater. a. Describe sources, composition and quantities of all sanitary, municipal and industrial wastewater

produced or treated at the site.

The proposed WWTF will receive domestic and commercial/light industrial wastewater. The wastewater strength is anticipated to be similar to residential wastewater. No significant industrial users are associated with this WWTF. It is anticipated that residential uses would continue to be the primary source of wastewater to this facility. If a significant industrial user moves into the community, the industry would be required to provide pretreatment prior to discharge to the WWTF. Wastewater from the industrial pretreatment facilities shall be similar in strength to domestic wastewater. The following table shows the composition and quantity of the influent wastewater to be treated by the expanded WWTF:

Parameter Design Value

ADW Flow 1.96 mgd AWW Flow 2.19 mgd Peak Hourly Flow 4.21 mgd Peak Instantaneous Flow 4.42 mgd Carbonaceous Biochemical Oxygen Demand (CBOD) 5,468 pounds/day Total Suspended Solids (TSS) 6,051 pounds/day Total Kjeldahl Nitrogen 1,076 pounds/day Phosphorus 158 pounds/day

b. Describe waste treatment methods or pollution prevention efforts and give estimates of composition

after treatment. Identify receiving waters, including major downstream water bodies, and estimate the discharge impact on the quality of receiving waters. If the project involves on-site sewage systems, discuss the suitability of site conditions for such systems.

The existing treatment facility has an NPDES Permit (MN0024538) for a discharge to the Mississippi River. The discharge location is shown on Figure 2. The proposed upgrade and expansion will include the following treatment units: Pretreatment Pretreatment removes inorganic material from the wastewater, such as sand, gravel, and rags. This material is removed by screening and settlement. The organic material stays in suspension for treatment in the next unit process.


Oxidation Ditch/Final Clarifier Process The new WWTF would be designed as an extended aeration activated sludge process. The major benefit with an extended aeration process is that the long retention time allows for effective and efficient operation even though flows and strengths may vary widely. Additionally, extended aeration facilitates can be designed for biological nutrient removal, specifically nitrogen and phosphorous. Conditions in the oxidation ditches are maintained for optimal growth of organisms that consume organic constituents in the wastewater. The organisms are given adequate time to interact with the wastewater stream (18 hours at high flows) to consume a majority of the organic content. Separation of the organisms or biomass from the water is done in the final clarifier. The water is slowed down enough to allow the organisms to settle to the bottom of the tank, while the treated water goes on to tertiary filters and then to disinfection. The activated sludge process promotes growth of organisms that attach to each other and form a sludge blanket in the final clarifier. Solids are removed from the final clarifier. Some are recycled to maintain the proper balance of biomass and influent load and some are wasted to biosolids treatment. Final clarifiers are capable of removing a majority of the solids and contaminants in the wastewater flow; however, the strict effluent limits associated with this plant requires additional treatment to insure the effluent standards are maintained Filtration Three tertiary (membrane) filter trains will be used to further treat the clarifier effluent. These filters will be designed to reject as much particulate matter, solids, and CBOD as possible. The practical limit for this technology is two milligrams per liter (mg/L) five-day CBOD (CBOD5) and two mg/L TSS. The filters will serve as an additional barrier to capture solids, such as organics, phosphorus, and mercury before the effluent is discharged to the Mississippi River (OVRW). Disinfection The disinfection system will be upgraded to handle the increase in flow due to the expansion. Specifically, disinfection kills remaining organisms and viruses in the water. UV disinfection will be used at this WWTF. The light inactivates bacteria and effectively protects the receiving stream from disease-causing organisms. River Designation and Standards The Mississippi River from St. Cloud to Anoka was added to the Minnesota Wild and Scenic Rivers System by the DNR in 1976. On November 5, 1984, the river was designated an ORVW under MPCA water quality rules. This reach of the Mississippi River is provided special protection under Minn. R. 7050.0180, Nondegradation for Outstanding Resource Value Waters, in recognition of its status as a state-designated scenic or recreational river segment. For such waters identified under subpart 6 of this nondegradation rule, new or expanding discharges are not allowed unless there is no prudent and feasible alternative to a discharge as proposed. If so allowed, a new or expanded discharge must then be restricted “to the extent necessary to preserve the existing high quality, or to preserve the wilderness, scientific, recreational, or other special characteristics that make the water an outstanding resource value water.” The Mississippi River is assigned use classifications of 1C, 2Bd, 3B, 3C, 4A, 4B, 5 and 6 under MPCA rules. These multiple classifications include consideration for domestic consumption, aquatic life and recreation, industrial consumption, agriculture and wildlife, aesthetic enjoyment and navigation, and other beneficial uses not specifically listed. Nondegradation discussion for the proposed expansion


The Big Lake WWTF was first constructed in 1982 with a direct discharge to the Mississippi River at a permitted design flow of 0.363 mgd. For purposes of applying nondegradation requirements, this original design establishes the pollutant loading limitations allowed by the MPCA on the effective date of ORVW designation for the Mississippi River in 1984. The applicable permitted mass loading for CBOD5 was 34.3 kilograms per day (kg/day) and 41.2 kg/day for TSS. The WWTF was subsequently expanded in 1999 to treat an AWW design flow of 0.840 mgd. Because the WWTF continued to be permitted at the established nondegradation mass load limitations for CBOD5 and TSS, that hydraulic expansion did not meet the definition of “expanded discharge” under Minn. R. 7050.0180, subp. 2. Therefore, nondegradation considerations were satisfied at the time of the 1999 expansion. Due to continued population growth within and around the City, expansion of the WWTF needs to be addressed again. The City’s proposal is to expand wastewater treatment capacity to an AWW design flow of 2.19 mgd, representing a 20-year planning period. To hold CBOD5 at the currently permitted mass load limit of 34.3 kg/day at the AWW design flow would require an effluent concentration not exceeding 4.1 mg/L as a monthly average. Similarly, an effluent concentration not exceeding 5.0 mg/L as a monthly average is required to hold the TSS mass load limit at 41.2 kg/day. These levels are achievable with membrane tertiary treatment technology. The City has decided to construct the membrane tertiary treatment facilities to meet the mass loading effluent limits permitted at the time of the 1984 ORVW designation. Therefore, the currently proposed Big Lake project does not meet the definition of an “expanded” discharge under Minn. R. 7050.0180 regarding nondegradation for ORVW waters and does not trigger nondegradation review because the City will provide additional treatment so that there is no increase in the permitted mass loading. The NPDES/SDS permit will include mass limits for CBOD5 and TSS that reflect a “freeze” in the mass loading based on the AWW design flow as of November 5, 1984. The table below summarizes the current and proposed effluent limits for the Big Lake WWTF for a discharge to the Mississippi River. ADW Design Flow: 0.709 mgd (current), 1.96 mgd (proposed 20-yr design) AWW Design Flow: 0.840 mgd (current), 2.19 mgd (proposed 20-yr design)

Current Proposed Parameter Concentration

Limitation or Range

Mass Limitation Concentration Limitation or

Range

Mass Limitation

CBOD5 25 mg/L 34.3 kg/day (a) 25 mg/L 34.3 kg/day (b)

TSS 30 mg/L 41.2 kg/day (a) 30 mg/L 41.2 kg/day (b)

Fecal Coliform 200 org./100 ml (c) NA 200 org./100 ml (c) NA

pH Range – Standard Units

6.0 - 9.0 NA 6.0 - 9.0 NA

Total Residual Chlorine

0.038 mg/L NA NA (d) NA

Total Phosphorus NA NA (e) 1.0 mg/L (f) 8.3 kg/d (f)


a. Mass limit permitted at time of 1984 ORVW designation. b. At the 20-year design flow of 2.19 mgd, this mass limit requires effluent concentrations not

exceeding 4.1 mg/L as a monthly average for CBOD5 and 5.0 mg/L for TSS. c. Applicable April 1 through October 31. d. Disinfection by UV light proposed instead of chlorine. e. Estimated wet weather load is 13.1 kg/day at sampled effluent phosphorus concentration,

averaging 4.11 mg/L (1999-2003) and 0.84 mgd. f. An annual, rather than a monthly, average limit can be applied if the treatment facility includes

biological phosphorus removal or treatment alternatives that offer environmental, financial, or other benefits.

Phosphorus Issues MPCA policy for NPDES permits calls for assigning a phosphorus limit to new or expanded discharges to an ORVW. The facility design includes provisions for biological phosphorus removal with chemical addition as a backup control to meet the recommended effluent limit of 1.0 mg/L total phosphorus as an annual average. The City would be the first municipal discharger to this reach of the Mississippi River to have a phosphorus effluent limitation in their discharge permit. The new 1.0 mg/L limit and maximum allowable discharge rate of 8.3 kg/day that is calculated at the proposed wet weather design flow of 2.19 mgd will result in a significant reduction in phosphorus loading to the river. Recent data results in a calculated mass loading of 13.1 kg/day using the average phosphorus concentration of 4.11 mg/L and wet weather design flow of 0.84 mgd. Impaired Water Issues The Mississippi River reach between the Clearwater River and the Elk River is on the 2004 MPCA (Clean Water Act Section 303d) TMDL List of Impaired Waters for fecal coliform, impaired biota, and mercury (fish consumption advisory). For such waters that are not meeting water quality standards, the MPCA is required under the federal Clean Water Act to conduct a TMDL study that includes specific plans to bring the water back into compliance and restore its beneficial uses. To address the fecal coliform and biota impairments, the current schedule targets the TMDL development process in 2007 for this reach of the Mississippi River. Since all municipal WWTFs are required by rule to disinfect to a level that meets the water quality standard for fecal coliform bacteria, the proposed expansion would not cause or contribute to the violation of this water quality standard. With respect to impaired aquatic biota, the cause(s) of the impairment has not been identified at this time. If the future TMDL studies establish a linkage between point source discharges of wastewater to biota impairments in this reach of the Mississippi River, then the discharge permits may be modified to include additional controls, as needed, to address specific parameters contributing to the impairment. The Mississippi River near Big Lake was first listed as an impaired water in 1998 because of fish consumption advice for mercury. Development of a state-wide mercury TMDL is currently under way. Mercury that is present in wastewater is strongly associated with the suspended solids. For the proposed expansion, if TSS is held at the currently permitted mass load, then mercury nondegradation requirements are not triggered and a limit is not required. However, as a “major” discharger, the City will be required to monitor for low-level mercury in the effluent on a quarterly basis. Therefore, the MPCA is proposing to use the strategy of freezing the permitted TSS mass loading on expanding dischargers to prevent increased mercury loading to a mercury-impaired receiving water.


The new phosphorus control for the Big Lake WWTF is also consistent with new internal MPCA guidance for issuing permits to insure that impaired waters are not further degraded before a TMDL is complete. The impaired water of concern is Lake Pepin, located downstream from the Big Lake discharge on the Mississippi River. Under this new permitting guidance, all expanding wastewater facilities upstream of this phosphorus-impaired water are capped at their existing phosphorus mass and must meet a 1.0 mg/L effluent limitation if they exceed a de minimus mass of 1,800 pounds per year (816 kg/yr).

Stormwater Control Secondary development will be enabled by the WWTF expansion and result in additional stormwater runoff. The nondegradation rule for ORVWs includes a policy statement: “To preserve the value of these special waters, the agency will prohibit or stringently control new or expanded discharges from either point or nonpoint sources to outstanding resource value waters.” Effective management of urban stormwater in a growing community can greatly reduce the nonpoint source loading attributable to surface runoff. The City has several ordinances in place to address stormwater relating to new development. Erosion control plans must be in place prior to beginning construction of a new development, and stabilization of the soil is necessary as soon as practical of any disturbed soil. Runoff velocities and volumes are subject to approval by the City Engineer and shall not exceed the level of undeveloped flow velocity and rate. The City is also protecting wetlands from stormwater runoff by requiring a minimum 30-foot monumented buffer to prevent erosion, while filtering sediment, chemicals, and nutrients, before stormwater discharges into wetlands and subsequent receiving streams. The City or an agent of the City does enforcement monitoring by performing weekly and post-rain event inspections of the erosion control measures. The City Building Inspector will also not perform any inspections on new construction until erosion control around each unit is in place.

c. If wastes will be discharged into a publicly owned treatment facility, identify the facility, describe any pretreatment provisions and discuss the facility’s ability to handle the volume and composition of wastes, identifying any improvements necessary. Not applicable.

d. If the project requires disposal of liquid animal manure, describe disposal technique and location and discuss capacity to handle the volume and composition of manure. Identify any improvements necessary. Describe any required setbacks for land disposal systems. Not applicable.

19. Geologic hazards and soil conditions. a. Approximate depth (in feet) to Ground water: 60 minimum; 60 average. Bedrock: +80 minimum; +80 average. Describe any of the following geologic site hazards to ground water and also identify them on the site

map: sinkholes, shallow limestone formations or karst conditions. Describe measures to avoid or minimize environmental problems due to any of these hazards. Geological information based on well logs of residences around the WWTP site. Local soil borings will be completed prior to design. No geologic hazards are known on the site.


b. Describe the soils on the site, giving SCS classifications, if known. Discuss soil granularity and

potential for ground-water contamination from wastes or chemicals spread or spilled onto the soils. Discuss any mitigation measures to prevent such contamination.

A complete geologic analysis of the area will be completed prior to construction of this project. The USGS Soil Survey for Sherburne County indicates sandy loam soils that are extremely well drained. These soils do not pose any limitations for construction of the facility improvements. The potential for ground water contamination would be minimal, as wastewater would be contained in process tanks and never come in contact with the soil. All new process tanks and piping would be leak tested to insure that they are water tight before actual use.

20. Solid Wastes, Hazardous Wastes, Storage Tanks. a. Describe types, amounts and compositions of solid or hazardous wastes, including solid animal

manure, sludge and ash, produced during construction and operation. Identify method and location of disposal. For projects generating municipal solid waste, indicate if there is a source separation plan; describe how the project will be modified for recycling. If hazardous waste is generated, indicate if there is a hazardous waste minimization plan and routine hazardous waste reduction assessments. A byproduct of activated sludge wastewater treatment facilities is excess biosolids. These biosolids need to be removed from the activated sludge process for final disposal. The methods of treatment and disposal range from storage and land application to treatment, bagging, and sale. The City is proposing a treatment process that yields a Class “A - Exceptional Quality Sewage Sludge” biosolids product. In other words, the treatment of the biosolids is such that the City can apply to MPCA to be regulated to a lesser degree. The City is proposing a drying process that will destroy pathogens and achieve vector reduction to classify the biosolids as Class “A.” At the 20-year design, the plant will produce approximately 3,000 pounds per day of dry solids. These solids can be land applied on local fields or may be distributed as fertilizer. The stabilized biosolids are an excellent source of nitrogen and phosphorous and even capable of adjusting the pH of alkaline soils. The City currently applies biosolids to one approved site. The site is a 30-acre parcel located in the SW ¼ of Section 25, T33N, R28W. This site is approximately two miles from the WWTF.

b. Identify any toxic or hazardous materials to be used or present at the site and identify measures to be used to prevent them from contaminating ground water. If the use of toxic or hazardous materials will lead to a regulated waste, discharge or emission, discuss any alternatives considered to minimize or eliminate the waste, discharge or emission. None.

c. Indicate the number, location, size and use of any above or below ground tanks to store petroleum products or other materials, except water. Describe any emergency response containment plans. Aluminum Sulfate (Alum) will be used as a chemical back up for phosphorus removal. Alum is a settling agent which improves solids removal and captures excess phosphorus. Alum would be added prior to the final clarifier and is stored in above-ground tanks that are required to have secondary containment.


21. Traffic. Parking spaces added: 0 Existing spaces (if project involves expansion): 5 Estimated total average daily traffic generated: Estimated maximum peak hour traffic generated (if known) and its timing: Provide an estimate of the impact on traffic congestion affected roads and describe any traffic improvements necessary. If the project is within the

Twin Cities metropolitan area, discuss its impact on the regional transportation system. The site will provide parking for the maximum number of City employees on site and a likely number of visitors to the site at any given time. The project will not generate any increase in traffic to the site.

22. Vehicle-related Air Emissions. Estimate the effect of the project’s traffic generation on air quality, including carbon monoxide levels. Discuss the effect of traffic improvements or other mitigation measures on air quality impacts. Note: If the project involves 500 or more parking spaces, consult EAW Guidelines about whether a detailed air quality analysis is needed. During construction, there would be a temporary increase in exhaust emissions from heavy-duty construction equipment. These emissions should not cause a significant adverse impact on air quality

23. Stationary Source Air Emissions. Describe the type, sources, quantities and compositions of any emissions from stationary sources of air emissions such as boilers, exhaust stacks or fugitive dust sources. Include any hazardous air pollutants (consult EAW Guidelines for a listing), any greenhouse gases (such as carbon dioxide, methane, and nitrous oxides), and ozone-depleting chemicals (chlorofluorocarbons, hydrofluorocarbons, perfluorocarbons or sulfur hexafluoride). Also describe any proposed pollution prevention techniques and proposed air pollution control devices. Describe the impacts on air quality. The only source of stationary source air emissions from the WWTF site would be a 1,000-kilowatt emergency back-up generator. Air emissions from the emergency generator would be infrequent and minor in nature.

24. Odors, noise and dust. Will the project generate odors, noise or dust during construction or during operation? Yes No

If yes, describe sources, characteristics, duration, quantities or intensity and any proposed measures to mitigate adverse impacts. Also identify locations of nearby sensitive receptors and estimate impacts on them. Discuss potential impacts on human health or quality of life. (Note: fugitive dust generated by operations may be discussed at item 23 instead of here.) During construction, dust emissions will increase temporarily. Adverse impacts are not anticipated. Water would be used to suppress dust before it becomes airborne. The dust should not impact residents significantly due to their distances from the project site. There will be a temporary increase in noise generated by heavy machinery during construction of the WWTF expansion. Hours of construction will be limited to 7:00 a.m. to 7:00 p.m. to minimize the impact on the surrounding area. The WWTF itself is not expected to be the source of significant noise during operation. It is possible that the WWTF may produce odors; however, odors associated with the WWTF will not increase as a result of the expansion. Design considerations, including the extended aeration treatment method and Class A biosolids treatment, will minimize odors caused by the site. Typical odors are described as earthy/musty smells associated with aerobic treatment of biomass. Currently, complaints from residents concerning odors from the WWTF are very rare, and the City expects to continue working well with the surrounding residents and businesses.

25. Nearby resources. Are any of the following resources on or in proximity to the site?


a. Archaeological, historical, or architectural resources? Yes No b. Prime or unique farmlands or land within an agricultural preserve? Yes No c. Designated parks, recreation areas, or trails? Yes No d. Scenic views and vistas? Yes No e. Other unique resources? Yes No If yes, describe the resource and identify any project-related impacts on the resources. Describe any

measures to minimize or avoid adverse impacts. The SHPO was contacted regarding the proposed expansion. The SHPO’s review of the project site identified one recorded archaeological site in the project area, recommending that a survey of the area be completed. The City hired a consultant to perform the survey recommended by the SHPO. An archaeological reconnaissance survey was conducted on April 12, 2005. The results of the survey found that there will be no historic properties affected by the proposed expansion project. A copy of the SHPO letter and archaeological reconnaissance survey is attached as Appendix 2.

26. Visual impacts. Will the project create adverse visual impacts during construction or operation? Such as

glare from intense lights, lights visible in wilderness areas and large visible plumes from cooling towers or exhaust stacks? Yes No If yes, explain. The expansion of the WWTF will not significantly alter the existing visual impacts. Few exterior lights will be added. No visible plumes will be coming from the site. The WWTF is located on a steep bank, buffered by trees, so it is not visible from the river. The WWTF is not visible from any residences in the area.

27. Compatibility with plans and land use regulations. Is the project subject to an adopted local comprehensive plan, land use plan or regulation, or other applicable land use, water, or resource management plan of a local, regional, state or federal agency? Yes No

If yes, describe the plan, discuss its compatibility with the project and explain how any conflicts will be resolved. If no, explain. The City completed a Comprehensive Plan Update of its Concept Land Use Plan in April 2000. The wastewater service area for the WWTF expansion has been based on the areas identified in the Comprehensive Plan Update. The proposed site is located in an agricultural zone as zoned by Sherburne County. A wastewater facility meets the zoning requirements. A conditional user permit will be sought from Sherburne County prior to expansion of the Big Lake WWTF. The Mississippi River from St. Cloud to Anoka was added to the Minnesota Wild and Scenic Rivers Program in 1976. The specific reach between Clearwater and Anoka was classified by the DNR as an outstanding recreational river, deemed to provide excellent fishing, canoeing, and boating opportunities. In addition, the Mississippi River is a designated state canoe and boating route. Proposed land use zoning and planning activities for this river corridor are contained in a draft Mississippi Scenic Riverway Management Plan, prepared by the DNR’s Division of Waters, dated January 2003. Since the proposed project is an expansion of an existing WWTF, and the City will design the expanded facility to maintain recommended permitted mass limitations for discharged pollutants, the project is compatible with the draft Mississippi Scenic Riverway Management Plan.

28. Impact on infrastructure and public services. Will new or expanded utilities, roads, other infrastructure


or public services be required to serve the project? Yes No If yes, describe the new or additional infrastructure or services needed. (Note: any infrastructure that is a connected action with respect to the project must be assessed in the EAW; see EAW Guidelines for details.) Since the expansion would take place at the site of the existing WWTF, the project would not require additional public utilities or road improvements, and there would be no changes to the existing force main.

29. Cumulative impacts. Minn. R. 4410.1700, subp. 7, item B requires that the RGU consider the “cumulative potential effects of related or anticipated future projects” when determining the need for an environmental impact statement. Identify any past, present or reasonably foreseeable future projects that may interact with the project described in this EAW in such a way as to cause cumulative impacts. Describe the nature of the cumulative impacts and summarize any other available information relevant to determining whether there is potential for significant environmental effects due to cumulative impacts (or discuss each cumulative impact under appropriate item(s) elsewhere on this form). The proposed improvements are designed to meet wastewater needs for the City through the design year 2023, and an average wet weather flow of 2.19 mgd. The treated effluent will be discharged on a continuous basis to the Mississippi River (ORVW). Additional treatment units will be added to the expanded facility to meet the more restrictive mass-based effluent limits. Several alternatives were evaluated by the City during the facility planning and nondegradation review processes.

The expanded facility will increase the capacity of the WWTF and, therefore, allow for new development in the service area. Increased development will also result in increased traffic, air pollution, stormwater runoff, and the generation of solid waste. As residential and commercial areas expand, the amount of farmland, open space and wildlife habitat in the area will decrease. Growth in and around the City is a result of the expansion of the Twin Cities Metropolitan area. The City is taking a proactive stance to improve necessary infrastructure such as stormwater, water supply, wastewater, and transportation to protect the environment and serve the growing population. Infrastructure improvements should be able to keep up with this pace of growth and protect the environment during and after the construction process. The City’s Comprehensive Land Use Plan, dated April 2000, proposes to protect environmentally-sensitive areas such as natural habitat, wetlands, tree canopy, drainage ways, and excessive slopes. The plan proposes to establish guidelines to insure that development is carefully integrated with the natural environment. The City minimizes the impact of nonpoint source pollution related to growth and urban development by implementing a stormwater control and inspection program (see Section 18.b.).

30. Other Potential Environmental Impacts. If the project may cause any adverse environmental impacts not addressed by items 1 to 28, identify and discuss them here, along with any proposed mitigation. None known at this time.


31. Summary of issues. List any impacts and issues identified above that may require further investigation

before the project is begun. Discuss any alternatives or mitigative measures that have been or may be considered for these impacts and issues, including those that have been or may be ordered as permit conditions.

During the nondegradation review process, several alternatives were analyzed to minimize the impact to the environment as a whole, and especially the Mississippi River, which was designated an OVRW by the state of Minnesota. This special designation limits the mass loading of CBOD5 and TSS from the wastewater plant to levels established in 1984. Since the City is experiencing tremendous growth, and the existing WWTF will quickly approach capacity, the “no action” alternative is not feasible for the planning area. In order to insure adequate wastewater treatment facilities for the City in the future, the City has taken a proactive approach to facilities planning. The following alternatives were considered during the nondegradation analysis: 1. Holding tanks with transport to a permitted treatment system. 2. Pipeline conveyance to a permitted treatment system. The corridor between St. Cloud and the

Twin Cities is a high-growth area. All communities in this area are growing or are planning to grow at a rate similar to the City. It is likely that all area facilities will be pushed to the limits of conventional treatment and will not have excess capacity. Given the growth in the area, hauling or pumping to another permitted treatment system is not a practical alternative.

3. Land application systems. In order to not exceed the currently permitted mass load limits for

discharge to the Mississippi River, the City evaluated land application alternatives (spray irrigation and rapid infiltration basins) that would accommodate about 500,000 gpd of the expanded plant capacity. These alternatives offer environmental and treatment advantages, including final disposal to an area not affecting the ORVW and effluent limits that are generally less stringent. General disadvantages are land usage, storage needs, additional pumping, potential ground water contamination, the need for ground water monitoring, and potential aesthetic impacts in high-growth areas.

Based on expected effluent quality and disposal criteria not exceeding 50 pounds of nitrogen per acre

per year, the consultant for the City determined that the minimum land requirement for spray irrigation is 320 acres (including set backs and siting criteria). Currently, land is selling for $20,000 to $40,000 per acre in the area where a spray irrigation field or rapid infiltration basin would be sited. Additional equipment and capital investment for land application includes a 500,000-gallon holding tank, lift station, force main, site (grading as required), distribution system, and monitoring wells. The estimated capital investment for a land discharge alternative to handle 500,000 gpd ranges from $10 to $14 million, depending on land prices at the time of purchase. The planned rerouting of U.S. Highway 10 around the south side of the City to within one mile north of the existing wastewater treatment facility will conceivably drive up land prices and the capital costs associated with land application.

Although the sandy loam soils in this area are hydraulically suitable for land application of

wastewater, impacts to ground water quality must be carefully considered for this disposal alternative. Private drinking water wells located in close proximity to any planned land application site must be closely monitored.


4. Alternative receiving waters not designated as ORVWs. The existing WWTF site is only several hundred yards from the Mississippi River, with a gravity outfall line to the river. Discharging into any alternative receiving water would require construction of a holding tank, lift station, and force main to the alternate location. The nearest alternative receiving water is a small, unnamed intermittent stream located about one mile east of the facility; however, since this intermittent stream drains directly to the Mississippi River, there would be no practical benefit to the ORVW from a change to this discharge location.

The existing facility lies within a minor watershed that drains directly to the Mississippi River. The

nearest non-ORVW receiving water outside of this watershed is the Elk River, about four miles to the north. However, a new discharge to the Elk River from the Big Lake WWTF was not considered to be a prudent alternative for a number of reasons, including: low dilution capacity of the Elk River would require advanced secondary wastewater treatment including ammonia removal; this reach of the Elk River already has aquatic life impairments due to low dissolved oxygen and has been included on the draft 2004 TMDL List; and a new discharge would add to the nutrient over-enrichment of downstream Orono Lake.

5. Trading reserve capacity with existing permitted system in the same impact area. (See the discussion

in the summary for alternatives 1 and 2, above.) 6. Evaluation of treatment plant upgrades so the mass loading rates in the existing permit are not

exceeded. The City evaluated WWTF upgrades that included: a 20-year design horizon with discharge to the ORVW (selected alternative); a 20-year design horizon with primary discharge to the ORVW and partial discharge via land application; and a ten-year design horizon with discharge to the ORVW.

Through the nondegradation review process, the City decided to provide the necessary treatment in

order to maintain existing mass loading limits. For a plant upgrade to the 2.19 mgd AWW design flow, representing a 20-year design horizon, the City would need to design to meet a stringent CBOD5 of 4.1 mg/L and a TSS concentration of 5.0 mg/L as a monthly average. The mass loading for CBOD and TSS would be maintained at 1984 OVRW levels. Estimated capital cost is $15,230,000.

A discharge alternative that provides the 20-year design capacity of 2.19 mgd and uses conventional treatment technology, while maintaining currently permitted mass limits (assuming effluent concentrations of 5 mg/L) for CBOD5 and TSS discharged to the ORVW, would require on-land disposal of up to 500,000 gpd by spray irrigation, rapid infiltration basins, or a combination of both. The additional equipment and disposal site for land applied effluent would add approximately $10 to $14 million in capital cost to the project.

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