National Pollutant Discharge Elimination System /State Disposal System (NPDES/SDS) Permit Program Fact Sheet

Transcription

1 National Pollutant Discharge Elimination System /State Disposal System (NPDES/SDS) Permit Program Fact Sheet Page 1 of 18 Permittee Facility Name Permit Number City of Detroit Lakes Detroit Lakes Wastewater P.O. Box 647 Treatment Facility Detroit Lakes, MN Willow Street West Detroit Lakes, MN Current Permit Expiration: March 31, 2012 Public Comment Period Begins: October 16, 2013 Period Ends: November 15, 2013 Receiving Water: Unnamed Wetland (Class 2D, 3D, 4C, 5 and 6 Water) to St. Clair Lake (Class 2B, 3C, 4A, 4B, 5 and 6 Water) Proposed Action: Permit Reissuance Permitting Contact Holly Christensen Minnesota Pollution Control Agency 714 Lake Avenue, Suite 220 Detroit Lakes, MN Phone: Fax:

2 Table of Contents Page 2 of 18 Purpose and Participation... 3 Applicable Statutes... 3 Purpose... 3 Public Participation... 3 Facility Description... 4 Background Information... 4 Facility Location Legal Description... 4 Outfall Location Legal Description... 4 Map of Permitted Facility... 5 Components and Treatment Technology... 6 Current Information... 6 Flow Schematic... 7 Changes to Facility or Operation... 8 Significant Industrial Users... 8 Recent Compliance History... 8 Recent Monitoring History... 8 Receiving Waters... 9 Use Classification... 9 Impairments Existing Permit Effluent Limits Technology Based Effluent Limits Water Quality Based Effluent Limits Proposed Permit Effluent Limits Technology Based Effluent Limits Water Quality Based Effluent Limits Phosphorus Priority Pollutants Mercury Monitoring Copper Whole Effluent Toxicity Testing Additional Requirements Biosolids Mercury Minimization Plan Compliance Schedules Variances Total Facility Requirements Non degradation and Anti backsliding... 17

3 Purpose and Participation Page 3 of 18 Applicable Statutes This fact sheet has been prepared according to the Title 40 Federal Code of Regulations (CFR) and and Minn R , Subp. 3 in regards to a draft NPDES/SDS permit to construct and/or operate wastewater treatment facilities and to discharge into waters of the State of Minnesota. Purpose This fact sheet outlines the principal issues related to the preparation of this draft permit and documents the decisions that were made in the determination of the effluent limitations and conditions of this permit. Public Participation You may submit written comments on the terms of the draft permit or on the Commissioner s preliminary determination. Your written comments must include the following: 1. A statement of your interest in the permit application or the draft permit. 2. A statement of the action you wish the Minnesota Pollution Control Agency (MPCA) to take, including specific references to sections of the draft permit that you believe should be changed. 3. The reasons supporting your position, stated with sufficient specificity as to allow the Commissioner to investigate the merits of your position. You may also request that the MPCA Commissioner hold a public informational meeting. A public informational meeting is an informal meeting which the MPCA may hold to help clarify and resolve issues. In accordance with Minn. R and Minn. R , your petition requesting a public informational meeting must identify the matter of concern and must include the following: items 1 through 3 identified above; a statement of the reasons the MPCA should hold the meeting; and the issues you would like the MPCA to address at the meeting. In addition, you may submit a petition for a contested case hearing. A contested case hearing is a formal hearing before an administrative law judge. Your petition requesting a contested case hearing must include a statement of reasons or proposed findings supporting the MPCA decision to hold a contested case hearing pursuant to the criteria identified in Minn. R , subp. 1 and a statement of the issues proposed to be addressed by a contested case hearing and the specific relief requested. To the extent known, your petition should include a proposed list of witnesses to be presented at the hearing, a proposed list of publications, references or studies to be introduced at the hearing, and an estimate of time required for you to present the matter at hearing. You must submit all comments, requests, and petitions during the public comment period identified on page 1 of this notice. All written comments, requests, and petitions received during the public comment period will be considered in the final decisions regarding the permit. If the MPCA does not receive any written comments, requests, or petitions during the public comment period, the Commissioner or other MPCA staff as authorized by the Commissioner will make the final decision concerning the draft permit. During the public comment period, however, you may request that the draft permit be presented to the MPCA s Citizens Board (Board) for final decision. You may participate in the activities of the Board as provided in Minn. R

4 Page 4 of 18 Comments, petitions, and/or requests must be submitted by the last day of the public comment period to: Holly Christensen Minnesota Pollution Control Agency 714 Lake Avenue, Suite 220 Detroit Lakes, MN The permit will be reissued if the MPCA determines that the proposed Permittee will, with respect to the facility or activity to be permitted, comply or undertake a schedule to achieve compliance with all applicable state and federal pollution control statutes and rules administered by the MPCA and the conditions of the permit and that all applicable requirements of Minn. Stat. ch. 116D and the rules promulgated thereunder have been fulfilled. More detail on all requirements placed on the facility may be found in the Permit document. Facility Description Background Information Facility Location The Detroit Lakes Wastewater Treatment Facility (Facility) is located at NW 1/4 of NE 1/4 of NW 1/4 of SW 1/4 of Section 33, Township 139 North, Range 41 West, Detroit Township, Becker County, Minnesota. The Facility is located on the west side of the city of Detroit Lakes. Outfall Location The outfall (Station SD002) is located at the SW/4 of the NW/4, Section 33, Township 139 North, Range 41 West, Detroit Township, Becker County, Minnesota. The discharge is a 450 foot dispersion ditch that is located to the south of the 25 acre stabilization pond and north of St. Clair Lake in a peat bog.

5 Page 5 of 18 Map of Permitted Facility

6 Page 6 of 18 Components and Treatment Technology Current Information The Facility consists of 9.08 miles of force main, 50 lift stations, an influent pumping station, a bar screen, aerated grit removal, a primary settling tank, two 40 foot diameter primary clarifiers, one 51 foot diameter trickling filter, one 97 foot diameter trickling filter, a secondary settling tank, a chlorine contact tank, a 3 acre polishing pond (4.75 day detention time), a 25 acre polishing pond (18 day detention time), an effluent pumping station, a chemical precipitation plant, a chlorination unit, two dual media filters, 19 rapid infiltration basins totaling acres, four spray irrigation sites totaling 54 acres with solid set programmable irrigation equipment, a 450 foot long effluent dispersion ditch, one primary sludge digester, one secondary sludge digester, two lime sludge concentration tanks, three lime sludge lagoons, three sludge storage tanks with a total capacity of 326,486 gallons, and a stand by generator. Fourteen ground water monitoring wells are installed at the Facility for monitoring the irrigation and rapid infiltration sites (GW008 was abandoned). The surface water discharge (SD002) is to the 450 foot long dispersion ditch that discharges to a peat bog and then to St. Clair Lake. The Facility is designed to treat an average annual influent flow of 1.64 million gallons per day (mgd) and an average wet weather flow of 2.02 mgd with a 5 day carbonaceous biochemical oxygen demand (CBOD 5 ) strength of 320 milligrams per liter (mg/l). From approximately April 15 to December 31, the treated effluent may be applied to the rapid infiltration basins (RIBs). The RIBs are operated by filling the basins up to three inches deep. The RIBs are then rested until they are dry. Excessive ground water had been collected in an underdrain system that discharged to the dispersion ditch (SD003), but those underdrains were permanently capped and sealed in From approximately May 15 to October 31, the treated effluent is applied to the four spray irrigation fields. RIBs may be used concurrently with the spray irrigation system.

7 Flow Schematic Page 7 of 18

8 Changes to Facility or Operation No changes to the Facility or Operation have occurred since the last permit issuance. Page 8 of 18 Significant Industrial Users (SIUs) No significant industrial users are identified for this facility. Recent Compliance History The Facility overall has been in compliance with the current permit. However, the most recent Whole Effluent Toxicity Tests failed. The Facility is currently in a Toxicity Identification Evaluation (TIE) and a Toxicity Reduction Evaluation (TRE). The 25 acre pond is currently 50 years old and has some structural issues with the dikes and the clay liner also leaks above the 3500 gallons per acre per day standard. There have also been issues with inadequate dissolved oxygen at times in the pond. There have been no significant reporting violations and no effluent violations over the past year. Recent Monitoring History Although the Facility has 14 groundwater monitoring wells and many internal waste stream monitoring points, only the influent and effluent data is presented here. Table 1: Waste Stream Station WS002 (Influent Waste Stream) Parameter Limit Type Limit Units 9/11 10/11 11/11 12/11 1/12 2/12 3/12 4/12 5/12 6/12 7/12 8/12 BOD, Carbonaceous 05 Day (20 Deg C) CalMoAvg mg/l BOD, Carbonaceous 05 Day (20 Deg C) CalMoMax mg/l Flow CalMoTot MG Flow CalMoAvg mgd Flow CalMoMax mgd Mercury, Total (as Hg) CalMoAvg ng/l ph CalMoMax SU ph CalMoMin SU Phosphorus, Total (as P) CalMoAvg mg/l Precipitation CalMoTot in Solids, Total Suspended (TSS) CalMoAvg mg/l Solids, Total Suspended (TSS) CalMoMax mg/l

9 Table 2: Surface Discharge Station SD002 (Surface Discharge) Water chemistry is also monitored on the flow to the RIBs and irrigation fields. Receiving Waters Page 9 of 18 Parameter Limit Type Limit Units 9/11 10/11 11/11 12/11 1/12 2/12 3/12 4/12 5/12 6/12 7/12 8/12 BOD, Carbonaceous 05 Day (20 Deg C) % Removal MnCalMoAvg 85 % NoDis NoDis NoDis NoDis NoDis NoDis NoDis BOD, Carbonaceous 05 Day (20 Deg C) CalMoAvg 227 kg/day NoDis NoDis NoDis NoDis NoDis NoDis NoDis BOD, Carbonaceous 05 Day (20 Deg C) MxCalWkAvg 340 kg/day NoDis NoDis NoDis NoDis NoDis NoDis NoDis BOD, Carbonaceous 05 Day (20 Deg C) CalMoAvg 20 mg/l NoDis NoDis NoDis NoDis NoDis NoDis NoDis BOD, Carbonaceous 05 Day (20 Deg C) MxCalWkAvg 30 mg/l NoDis NoDis NoDis NoDis NoDis NoDis NoDis Chloride, Total CalMoAvg mg/l NoDis NoDis NoDis NoDis NoDis NoDis NoDis Chlorine, Total Residual DailyMax mg/l NoDis NoDis NoDis NoDis NoDis NoDis NoDis Copper, Total (as Cu) SingleVal ug/l NoDis NoDis NoDis NoDis NoDis NoDis NoDis Fecal Coliform, MPN or Membrane Filter 44.5C CalMoGeoMn 200 #100ml NoDis NoDis NoDis NoDis NoDis NoDis NoDis Flow CalMoTot MG NoDis NoDis NoDis NoDis NoDis NoDis NoDis Flow CalMoAvg mgd NoDis NoDis NoDis NoDis NoDis NoDis NoDis Mercury, Dissolved (as Hg) CalMoAvg ng/l NoDis NoDis Mercury, Total (as Hg) CalMoAvg ng/l NoDis NoDis Nitrogen, Ammonia, Total (as N) CalMoAvg mg/l NoDis NoDis NoDis NoDis NoDis NoDis NoDis Oxygen, Dissolved CalMoMin mg/l NoDis NoDis NoDis NoDis NoDis NoDis NoDis ph CalMoMax 9 SU NoDis NoDis NoDis NoDis NoDis NoDis NoDis ph CalMoMin 6 SU NoDis NoDis NoDis NoDis NoDis NoDis NoDis Phosphorus, Total (as P) CalMoAvg 11.4 kg/day NoDis NoDis NoDis NoDis NoDis NoDis NoDis Phosphorus, Total (as P) CalMoAvg 1 mg/l NoDis NoDis NoDis NoDis NoDis NoDis NoDis Solids, Total Suspended (TSS) % Removal MnCalMoAvg 85 % NoDis NoDis NoDis NoDis NoDis NoDis NoDis Solids, Total Suspended (TSS) CalMoAvg 227 kg/day NoDis NoDis NoDis NoDis NoDis NoDis NoDis Solids, Total Suspended (TSS) MxCalWkAvg 340 kg/day NoDis NoDis NoDis NoDis NoDis NoDis NoDis Solids, Total Suspended (TSS) CalMoAvg 20 mg/l NoDis NoDis NoDis NoDis NoDis NoDis NoDis Solids, Total Suspended (TSS) MxCalWkAvg 30 mg/l NoDis NoDis NoDis NoDis NoDis NoDis NoDis Use Classification The immediate receiving water is a peat bog that is classified as a 2D, 3D, 4C, 5 and 6 water. The peat bog is connected to St. Clair Lake which is classified as a 2B, 3C, 4A, 4B, 5 and 6 water. Minnesota Rules Subp. 4. Class 2B waters. The quality of Class 2B surface waters shall be such as to permit the propagation and maintenance of a healthy community of cool or warm water sport or commercial fish and associated aquatic life, and their habitats. These waters shall be suitable for aquatic recreation of all kinds, including bathing, for which the waters may be usable. This class of surface water is not protected as a source of drinking water. Subp. 6. Class 2D waters; wetlands. The quality of Class 2D wetlands shall be such as to permit the propagation and maintenance of a healthy community of aquatic and terrestrial species indigenous to wetlands, and their habitats. Wetlands also add to the biological diversity of the landscape. These waters shall be suitable for boating and other forms of aquatic recreation for which the wetland may be usable. Minnesota Rules Subp. 4. Class 3C waters. The quality of Class 3C waters of the state shall be such as to permit their use for industrial cooling and materials transport without a high degree of treatment being necessary to avoid severe fouling, corrosion, scaling, or other unsatisfactory conditions. Subp. 5. Class 3D waters; wetlands. The quality of Class 3D wetlands shall be such as to permit their use for general industrial purposes, except for food processing, with only a moderate degree of treatment. Minnesota Rules

10 Page 10 of 18 Subp. 2. Class 4A waters. The quality of Class 4A waters of the state shall be such as to permit their use for irrigation without significant damage or adverse effects upon any crops or vegetation usually grown in the waters or area, including truck garden crops. Subp. 3. Class 4B waters. The quality of Class 4B waters of the state shall be such as to permit their use by livestock and wildlife without inhibition or injurious effects. Subp. 4. Class 4C waters; wetlands. The quality of Class 4C wetlands shall be such as to permit their use for irrigation and by wildlife and livestock without inhibition or injurious effects and be suitable for erosion control, groundwater recharge, low flow augmentation, stormwater retention, and stream sedimentation. Minnesota Rules Subp. 2. Class 5 waters; aesthetic enjoyment and navigation. The quality of Class 5 waters of the state shall be such as to be suitable for aesthetic enjoyment of scenery, to avoid any interference with navigation or damaging effects on property. Minnesota Rules Subp. 2. Class 6 waters; other uses. The uses to be protected in Class 6 waters may be under other jurisdictions and in other areas to which the waters of the state are tributary, and may include any or all of the uses listed in parts to , plus any other possible beneficial uses. Impairments Lake St. Clair was placed on the 2008 MPCA Clean Water Act Section 303 (d) list of impaired waters due to excess nutrients which impede designated uses such as recreation on the lake. St Clair Lake is exceeding standards when compared to numeric eutrophication standards for shallow lakes in the North Central Hardwood Forest Ecoregion. Therefore, a Total Maximum Daily Load (TMDL) Study was initiated for St. Clair Lake in 2012, and is currently underway. Existing Permit Effluent Limits The effluent limits and monitoring requirements in the current permit are presented in Table 3 at the end of this section. This table lists water quality based effluent limits (WQBELs) and technology based effluent limits (TBELs) and state discharge restrictions (SDRs). WQBELs are established based on an analysis of downstream water quality. In contrast, TBELs represent an anticipated pollutant removal efficiency that can be reasonably expected based on the type of treatment technology used. Alternatively, SDRs are established based on requirements within state rule, and these limits are neither based on a water quality analysis nor do they have a relationship to the type of treatment technology used. Technology Based Effluent Limits (TBELs) The 5 day Carbonaceous Biochemical Oxygen Demand (CBOD 5 ), Total Suspended Solids (TSS), and ph are TBELs developed for achieving secondary treatment standards. These limits are specified in 40 CFR and Minn. R and Minn. R , Subp. 1. Water Quality Based Effluent Limits (WQBELs) The Total Residual Chlorine (TRC) limit is a WQBEL and is the final acute value for chlorine found in Minn. R This limit was determined to be necessary to protect the use classification for the receiving water. The total phosphorus limit is also a WQBEL based on Minn. R

11 Page 11 of 18 The WBELS were used to make reasonable potential determinations, as established under 40 CFR (d). Cadmium, chromium, and lead were all below detectable levels, and reasonable potential determinations could not be completed for them. Reasonable potential was not indicated for nickel, zinc, and mercury. Reasonable potential was indicated for copper. However, that conclusion was based on three data points and the assumption that total metals equals dissolved. The water quality standards for metals in Minn. R are expressed as dissolved metal to address the actual toxic component of a metal. The toxicity of copper is affected by hardness and other effluent constituents. Effluent quality was protected statistically on the basis of three data points and just exceeded the daily maximum WQBEL. The permit included an annual monitoring requirement for total copper in the effluent in addition to priority pollutant monitoring. Table 3: Current Surface Water Station SD002 Limits and Monitoring Requirements

12 Proposed Permit Effluent Limits Page 12 of 18 The effluent limits and monitoring requirements in the proposed permit are presented in Table 9 at the end of this section. Technology Based Effluent Limits The 5 day Carbonaceous Biochemical Oxygen Demand (CBOD 5 ), Total Suspended Solids (TSS), and ph are TBELs developed for achieving secondary treatment standards. These limits are specified in 40 CFR and Minn. R and Minn. R , Subp. 1. Water Quality Based Limits The Total Residual Chlorine (TRC) limit is a WQBEL and is the final acute value for chlorine found in Minn. R This limit was determined to be necessary to protect the use classification for the receiving water. The total phosphorus limit is also a WQBEL. Phosphorus A reasonable potential analysis for total phosphorus (TP) discharged by the Facility to St. Clair Lake was conducted. Although the Facility average wet weather design flow (AWWDF) is 2.02 mgd, actual effluent flow discharged to surface water only occurs from November through April due to utilization of the rapid infiltration basins and irrigation acreage in the summer. St. Clair Lake (Lake ID # ) was placed on the Federal 303(d) list of impaired waters in 2008 for eutrophication due to excess phosphorus. Federal law [40 CFR (d)] restricts mass increases upstream of impaired waters and states that all NPDES dischargers that have the reasonable potential (RP) to cause or contribute to downstream impaired waters are required to have a water quality based effluent limit (WQBEL). Permittees are found to have RP if all of the following conditions exist: 1) they discharge upstream of a nutrient impaired waterbody, 2) they discharge at a TP concentration greater than the ambient target, and 3) there is no geographical barrier capable of trapping a significant mass of nutrients between the outfall and the impairment. For all three reasons, this Facility is found to have RP. A water quality model was developed for Saint Clair Lake and the contributing watershed to 1) characterize the existing phosphorus load to Saint Clair Lake and 2) determine the reductions necessary to meet water quality standards. Reductions in point and nonpoint source loading were then evaluated through several scenarios which resulted in a recommended total phosphorus effluent limit of 198 kg/yr for the Facility. It is recommended that this limit be expressed as a 12 month moving average. Additional details regarding this model and the recommended phosphorus limit are reported in a memo 1 which can be provided upon request. Priority Pollutants Federal regulations require MPCA to evaluate the discharge to determine whether the discharge has the reasonable potential to cause or contribute to a violation of water quality standards. The Agency must use acceptable technical procedures, accounting for variability (coefficient of variation, or CV), when determining whether the effluent causes, has the reasonable potential to cause, or contribute to an excursion of an applicable water quality standard. Projected effluent quality (PEQ) derived from effluent monitoring data is compared to Preliminary Effluent Limits (PELs) determined from mass balance inputs. Both determinations account for effluent variability. Where PEQ exceeds the PEL, there is reasonable potential to cause or contribute to a water quality standards excursion. When Reasonable Potential is indicated the permit must contain a water quality based effluent limit (WQBEL) for that pollutant. 1 Total Phosphorus Water Quality Based Effluent Limit Analysis: City of Detroit Lakes WWTP to Saint Clair Lake, 06/07/2012, memo from MCPA Scientist Steven Weiss

13 Page 13 of 18 The priority pollutant scan information of the effluent was evaluated using reasonable potential procedures. All but Toluene and Di 2 ethylhexylphthalate (DEPH) of the organic priority pollutants were below the level of detection. Since these pollutants were at low enough levels not to be detected, reasonable potential to cause or contribute to a water quality standards excursion is not indicated. Toluene and DEPH were detectable, although the DEPH samples are likely the result of lab contamination. Total arsenic, total copper, total selenium, and total zinc were also found in the priority pollutant scan. Total copper and total mercury were also routinely monitored during the last permit cycle. From the table below arsenic, copper, selenium, toluene, and zinc indicated no reasonable potential to cause or contribute to an excursion above the applicable water quality standard. No effluent limits are needed for the five previously mentioned contaminates. However, reasonable potential to cause or contribute to an exceedence of a WQS has been found with DEPH. This is discussed below. Mercury Monitoring results of the effluent included seventeen data points at a calculated CV of Projected effluent quality (PEQ) is derived as an upper bound value from the highest value measured (2.7 nanograms per liter (ng/l), and the determined variability (CV = ) and number of data points (17). The preliminary effluent limit (PEL) calculation assumes that the background mercury concentration is at the water quality standard (6.9 ng/l) when the listed stream impairment is for fish consumption advice, and no local river water column analytical data exist. To assure that the discharge does not cause or contribute to a water quality standards excursion for mercury impaired waters, the numeric water quality standard (6.9) is applied at the point of discharge for the mass balance equation for the subsequent preliminary effluent limit calculations. Where PEQ exceeds the PEL, there is reasonable potential to cause or contribute to a water quality standards excursion. Since PEQ does not exceed the PEL in this case, reasonable potential to cause or contribute to an excursion above water quality standards is not indicated. A water quality based effluent limit (WQBEL) is not needed. The following table contains the inputs to the reasonable potential analysis for arsenic copper, selenium, DEPH, toluene, zinc, and mercury. The analysis is made with effluent data that is expressed as total metal. These pollutants were evaluated on the basis of analytical measurements that made evident the need for a full determination. Where Projected Effluent Quality (PEQs) exceed Preliminary Effluent Limitations (PELs), a WQBEL is needed.

14 Table 4: Reasonable Potential Parameter (ug/l) As Cu Se DEPH Toluene Zn Hg (ng/l) Max Measured Value # data points PEQ Plant flow ADW (mgd) Rec. water flow, 7Q10(mgd) Background Conc. (none) * Continuous Std (cs) ppm hard Maximum Std (ms) NA ppm hard Final Acute Value (FAV) NA ppm hard Mass Balance cs Mass Balance ms Coeff of Variation (CV) Long Term Avg cs Long Term Avg ms Preliminary Effl limits: Daily Max Monthly Ave (2x/month) Reasonable Potential PEQ>PEL No No No Yes** No No No (Dmax/FAV) Notes No background info on wetland *Mercury background set to chronic std because of statewide TMDL No chronic WET RP done, DL is in the middle of a TRE. **DEPH reasonable potential probably due to lab contamination. Page 14 of 18 Reasonable potential to cause or contribute to the excursion above a water quality standard has been indicated for Di 2 ethylhexylphthalate (DEPH). However, this is based off of limited sampling and DEPH is often a result of lab contamination. As such MPCA staff do not recommend a WQBEL for DEPH at this Facility at this time. Instead, MPCA staff recommend once per month monitoring (during discharge events) of DEPH. Mercury Monitoring This Facility indicated no reasonable potential to cause or contribute to the exceedance of the water quality standard (WQS) of 6.9 ng/l for total mercury. Following the Permitting Strategy for Addressing Mercury in Municipal and Industrial Wastewater Permits (Water Quality/ Wastewater Permit No March 2009), existing municipal facilities with an average wet weather design flow greater than 1.0 mgd which don t have reasonable potential to cause or contribute to the exceedance of the mercury WQS must: Monitor quarterly for total and dissolved mercury at the influent and effluent throughout the five year permit life cycle. The influent and effluent total mercury samples will be taken at the same time. A grab total suspended solids sample will also be taken at the influent and effluent locations at the same time.

15 Page 15 of 18 Copper The Permittee must continue to monitor once per month (during discharge events) for total copper since the PEQ was very close in relation to the chronic WQS. The following EPA Inorganic Analytical Methods (EPA 600/ ) and EPA Organic Analytical Methods (40 CFR 136; Oct. 26, 1984) apply: Table 5: Monitoring Requirements Pollutant Monitoring Frequency EPA Method Method Detection Level DEPH 1/month during discharge 625 MDL = 2.9 ug/l Total/Dissolved 1/quarter (influent & effluent) 1631 & ng/l Mercury Total Copper 1/month during discharge ug/l Priority pollutant scans will continue to be required three times during the five year permit cycle. Whole Effluent Toxicity Testing This Facility is in the middle of a Toxicity Reduction Evaluation (TRE) and a Toxicity Identification Evaluation (TIE). Corrective actions will be taken as a result of the TRE. Corrective actions and upgrades will also be made to the Facility because of on going low dissolved oxygen issues and other issues associated with the Permittee s stabilization ponds. Because of the changes due to the TRE and the stabilization pond issues, MPCA staff did not perform a reasonable potential analysis for chronic WET testing related to this Facility. Because this Facility is in a TRE, MPCA staff will require a chronic WET limit of 1.0 TUc (Toxic Units chronic). MPCA staff also recommends that after the TRE has been completed and the upgrades/changes to the Facility have been made according to the TRE findings, the Permittee will do quarterly chronic WET monitoring for the first year after the TRE and the TRE changes have been completed. Annual chronic WET test will be required after the fourth quarterly test has been completed for the life of the permit.

16 Table 6: Surface Discharge Station SD002 Proposed Limits Page 16 of 18

17 Additional Requirements Page 17 of 18 Biosolids This permit requires biosolids to be treated to meet specific standards and specifies monitoring, recordkeeping, reporting and general requirements for biosolids which are generated by this Facility and applied to the land. Unless they are Exceptional Quality Biosolids, sites to which biosolids are applied are approved by the MPCA by the procedures found in Minn. R Mercury Minimization Plan This permit contains requirements for mercury monitoring and for submittal of a Mercury Minimization Plan (MMP) or updated MMP within 180 days of permit reissuance. The purpose of the MMP is to evaluate collection and treatment systems to determine possible sources of mercury, as well as potential mercury reduction options, in an effort to reduce mercury in the Facility s discharge. These requirements are consistent with the MPCA s mercury strategy for addressing mercury in municipal and industrial wastewater permits and the TMDL implementation plan that is the result of the U.S. EPA s approval of the Minnesota State Wide Mercury TMDL Study. Compliance Schedules This permit contains a compliance schedule for submittals related to: the TIE and TRE addressing the cause of the toxicity in the wastewater, the structural integrity of the treatment system, excessive leakage of the 25 acre stabilization pond, and the more stringent phosphorus limit placed in this permit as a result of the impaired water status of the receiving water. The Permittee will be required to complete a Comprehensive Study/Integrated Plan (Study) and submit a final report for MPCA review and approval. The Study will include, but not be limited to, addressing the following: leaking ponds, toxicity treatment, wastewater treatment facility (WWTF) structural and age issues, total phosphorus reduction, different or additional discharge location, WWTF service coverage expansion to include unsewered and/or undersewered residences (improve lake quality issues), the effect the airport expansion has on WWTF, and potential stormwater issues at WWTF existing or future locations. Variances This Facility does not have any variances to TBELs or WQBELs. Total Facility Requirements All NPDES/SDS permits issued by the State of Minnesota contain certain conditions that remain the same, regardless of the size, location, or type of discharge. The standard conditions satisfy the requirements that are outlined in 40 CFR , Minn. R , and These conditions are listed in the Total Facility Requirements chapter of the NPDES/SDS permit. These requirements cover a wider range of areas, including recordkeeping, sampling, equipment calibration, equipment maintenance, reporting, facility upsets, bypasses, solids handling, changes in operation, facility inspections, and permit modification and reissuance. Non degradation and Anti Backsliding In accordance with Minnesota Pollution Control Agency rules regarding non degradation for all waters (that are not Outstanding Resource Value Waters), non degradation review is required for any new or expanded significant discharge (Minn. R ). A significant discharge is 1) a new discharge (not

18 Page 18 of 18 in existence before January 1, 1988) that is greater than 200,000 gallons per day or 2) an expanded discharge that expands by greater than 200,000 gallons per day that discharges to any non ORVW water other than a Class 7 water or 3) a new or expanded discharge containing any toxic pollutant at a mass loading rate likely to increase the concentration of the toxicant in the receiving water by greater than one percent over the baseline quality. This Permit also complies with Minn. R regarding anti backsliding. Any point source discharger of sewage, industrial, or other wastes for which a national pollutant discharge elimination system permit has been issued by the agency that contains effluent limits more stringent than those that would be established by parts to shall continue to meet the effluent limits established by the permit, unless the permittee establishes that less stringent effluent limits are allowable pursuant to federal law, under section 402(o) of the Clean Water Act, United States Code, title 33, section 1342.