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

Transcription

1 National Pollutant Discharge Elimination System (NPDES)/State Disposal System (SDS) Permit Program Fact Sheet Permittee: City of Litchfield Facility Name: Litchfield WWTF Permit Number: MN N Marshall Ave 1350 N Armstrong Ave Litchfield, MN Litchfield, MN Current Permit Expiration: January 31, 2013 Public Comment Period Begins: January 30, 2014 Period Ends: March 3, 2014 Receiving Water: Jewitt s Creek Proposed Action: Reissuance Permitting Contact Ashley Wahl 504 Fairgrounds Road, Suite 200 Marshall, Minnesota Phone: Fax:

2 Table of Contents Purpose and Participation... 3 Applicable Statutes... 3 Fact Sheet Purpose... 3 Public Participation... 3 Facility Description... 4 Facility Outfall and Location... 4 Map of Permitted Facility... 5 Components and Treatment Technology... 6 Significant Industrial Users... 6 Recent Compliance History... 6 Recent Monitoring History... 8 Receiving Water... 9 Use Classification... 9 Impairments... 9 Existing Permit Effluent Limits State Discharge Restrictions Technology Based Effluent Limits Water Quality Based Effluent Limits Proposed Permit Effluent Limits State Discharge Restrictions Technology Based Effluent Limits Water Quality Based Effluent Limits Additional Requirements Mercury Minimization Plan Compliance Schedules Salty Discharge Monitoring Additional Nitrogen Monitoring Biosolids Total Facility Requirements Nondegradation and Anti-Backsliding

3 Purpose and Participation Applicable Statutes This fact sheet has been prepared according to Title 40, Federal Code of Regulations (CFR) and and Minn R , subp. 3, in regards to a draft National Pollutant Discharge Elimination System (NPDES) / State Disposal System (SDS) 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; and 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 items 1 through 3 identified above and 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 the 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 3

4 MPCA s Citizens Board (Board) for final decision. You may participate in the activities of the Board as provided in Minn. R Comments, petitions, and/or requests must be submitted by the last day of the public comment period to: Ashley Wahl Minnesota Pollution Control Agency 504 Fairgrounds Road, Suite 200 Marshall, Minnesota 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 Facility and Outfall Location The Litchfield Wastewater Treatment Facility (Facility) is located in the SW ¼ of Section 1, Township 119 North, Range 31 West, Litchfield, Meeker County, Minnesota. This is a Class A facility. The Facility has a continuous discharge with one outfall (SD001). The outfall is located next to the Facility as described above. The location of the Facility and SD001 are shown in Figure 1. 4

5 Map of Permitted Facility Figure 1. Location of Permitted Facility and Discharge Station 5

6 Components and Treatment Technology Current Information The existing Facility is designed to treat an average wet weather (AWW) flow of 3.10 million gallons per day (mgd) with an influent five-day carbonaceous biochemical oxygen demand (CBOD 5 ) of 15,800 pounds per day. The Facility includes influent pumping (three centrifugal pumps) and flow monitoring (Parshall flume), a fine screen, grit removal, pre-aeration, three primary clarifiers, two trickling filters, two intermediate clarifiers, three aeration basins, two final clarifiers, six gravity media filters, chlorination and dechlorination, effluent aeration and flow measurement. Chemical addition (ferric chloride) is provided for phosphorus removal and partial influent equalization and ph control is provided. Biosolids facilities include a dissolved air flotation thickener, anaerobic digestion and biosolids storage. Changes to Facility or Operation Proposed Facility additions include: two 0.5-million gallon equalization tanks with jet mixing/aeration and an influent control building to house blowers, pumps, ph adjustment chemicals and odor control equipment. The existing Facility was designed and constructed to treat a biochemical oxygen demand loading of 15,800 pounds per day. This loading correlates to an AWW design flow of 3.1 mgd. The increase in design flow was not evaluated with respect to permit limits during the upgrade that occurred in a previous permit. This draft Permit now contains an AWW design flow of 3.1 mgd. Five-day biochemical oxygen demand (CBOD 5 ) and un-ionized ammonia limits have been recalculated using the expanded flow. Significant Industrial Users (SIUs) The Facility is currently accepting wastewater from one SIU. First District Association, a dairy processor, intermittently sends 470,000 GDP of process wastewater to the Facility for treatment. The SIU is subject to local limits. Recent Compliance History A Compliance Evaluation Inspection (CEI) was conducted on the Facility on December 13, 2011, by the MPCA staff to determine the Facility's compliance with the terms and conditions of its NPDES/SDS Permit. A violation list was reviewed for the period of May 2010 through October During this time, the City of Litchfield (City) reported the following effluent violations: Date Parameter Limit Type Limit Reported Value May 2011 CBOD MaxCalWkAvg 108 kg/day 123 kg/day May 2011 CBOD MaxCalWkAvg 15 mg/l 21 mg/l May 2011 Ammonia CalMoAvg 4.3 mg/l 4.7 mg/l April 2011 Fecal coliform CalMoGeoMean 200/100 ml 211/100 ml December 2010 CBOD MaxCalWkAvg 15 mg/l 17 mg/l June 2010 Chlorine, TRC Daily Max mg/l 0.11 mg/l These violations were discussed in detail during the inspection. The possible cause of the May 2011 violations was likely a result of one of the trickling filters taken out of service for a rehabilitation project. 6

7 Actions were taken to prevent effluent violations during this period, including increased recycle ratio to the operating trickling filter and increasing mixed liquor suspended solids concentration in the aeration basin. Additional filter media has been added to the trickling filter which will increase CBOD and ammonia treatment capabilities, and hopefully prevent this violation in the future. The City submitted a report in addition to the Discharge Monitoring Reports (DMRs) detailing the violation, possible causes, and actions taken by the City. The April 2011 violation was likely caused by a new chlorine and dechlorination system which required proper adjustment. The City discovered air leaks in the system which allowed air from the atmosphere to be injected instead of chlorine. The City has reviewed the control programming of this system and recalibrated the chlorine meters to prevent this violation in the future. The City submitted a report in addition to the DMRs, which explained this violation and the actions to address and prevent future violations of this type. The cause of the December 2010 violation has not yet been determined. The June 2010 violation of the chlorine limit may have been the result of a valve being partially shut on the booster pump. The City staff made adjustments to the system upon discovery of a high chlorine residual and took several repeat samples in an attempt to meet the limit. This equipment has since been replaced. The City submitted a report in addition to the DMRs which described the violation, potential causes, and actions taken. The City also submitted a Total Residual Chlorine Corrective Action Report. The City has already taken several steps to prevent these types of effluent violations in the future. The City was instructed to take all necessary action to ensure compliance with effluent limits in the future. These violations were discussed at the inspection and no further correspondence was required. 7

8 Recent Monitoring History Table 1: Discharge Monitoring Report Results July 2012 Through June

9 Receiving Water Use Classification The Facility has a continuous discharge, SD001, to Jewett s Creek. The water is classified as a 2C, 3C, 4A, 4B, 5, 6 water. This classification indicates that the body of water is capable of sustaining the propagation and maintenance of a healthy community of indigenous fish and associated aquatic life, and their habitats. The classification also indicates that these waters shall be suitable for boating and other forms of aquatic recreation for which the waters may be usable. More information on the classification of waters can be found in Minn. R Impairments Table 2. Impairments of the Receiving Waters AUID or Lake ID # AUID description or Lake name Assessment Category & Subcategory Jewitts Creek (County Ditch 19, 5A 18, 17) : Headwaters (Lk Ripley ) to N Fk Crow R Jewitts Creek (County Ditch 19, 5A 18, 17) : Headwaters (Lk Ripley ) to N Fk Crow R Jewitts Creek (County Ditch 19, 5A 18, 17) : Headwaters (Lk Ripley ) to N Fk Crow R Jewitts Creek (County Ditch 19, 5A 18, 17) : Headwaters (Lk Ripley ) to N Fk Crow R Pollutants or Impairment Ammonia (Un-ionized), Dissolved Oxygen Fish bioassessments Aquatic Macroinvertebrate bioassessments Chloride, Escherichia Coli Draft Jewitts Creek Total Maximum Daily Load (TMDL): The draft Jewitts Creek Low dissolved oxygen (DO) TMDL is based on the River and Stream Water Quality Model (QUAL2K), a public domain model that is widely used and supported by the U.S. Environmental Protection Agency (EPA) for TMDL development. This model represents the stream as a well-mixed channel and is intended to be applied to steady-state flow conditions. Historic DO monitoring indicates that summer base-flow is the critical condition for DO making this an appropriate model for analyzing DO violations. Data from a summer low-flow synoptic survey was used to build and calibrate one event specific QUAL2K model for the impaired stream. For DO TMDLs, the loading capacity is the maximum allowable oxygen demand, (CBOD+ nitrogenous biochemical oxyen demand (NBOD)+ sediment oxygen demand (SOD)) the stream can withstand and still meet water quality standards. To determine this number, SOD rates and pollutant loading from headwaters, wastewater treatment facilities and/or tributary/diffuse sources were adjusted until it was clear model-predicted minimum daily DO in each reach never dropped below the 5.0 mg/l standard. 9

10 This permit action rerates the WWTP s AWW design flow from 2.37 mgd to 3.1 mgd but also reduces the effluent CBOD 5 permit limit from 72 kilograms (kg) per day to 58.6 kg/day. Increasing the permitted flow will not exacerbate the DO impairment because the permit s 5 mg/l CBOD 5 and 2.1 mg/l Ammonia-N effluent limits are sufficiently restrictive to ensure that discharge from the Litchfield WWTP will not cause or contribute to violations of the 5 mg/l DO water quality standard, regardless of the Total Oxygen Demand load discharged. Successive QUAL2K model runs illustrated below demonstrate that increasing the volume of flow discharged from the Litchfield WWTP, while maintaining effluent concentrations at permitted levels, helps increase aeration and decreases travel time in Jewitts Creek, and therefore decreases the probability of future water quality standard violations. This analysis demonstrates that the current rerating of the facility s AWW design flow and potential future facility expansions will be protective of the Jewitts Creek 5 mg/l DO water quality standard as long as effluent CBOD 5 and Ammonia-N effluent concentration limits remain in effect. The figures below represent the following QUAL2K model run scenarios: 1. TMDL Model Run: Litchfield WWTP Flow = 2.37 mgd; Ammonia = 2.1 mg/l; CBOD 5 = 5 mg/l. 2. Scenario #1: Litchfield WWTP Flow = 3.0 mgd; Ammonia = 2.1 mg/l; CBOD 5 = 5 mg/l. 3. Scenario #2: Litchfield WWTP Flow = 5.0 mgd; Ammonia = 2.1 mg/l; CBOD 5 = 5 mg/l. Figure 2. TMDL Model Run. 10

11 Figure 3. Scenario #1 Figure 4. Scenario #2 11

12 Existing Permit Effluent Limits The limits and monitoring requirements in the current Permit are presented in Tables 3 and 4. These tables list both water quality and technology-based limits. Table 3. Existing Discharge Limits for Station SD001 (continued on page 13) 12

13 Table 4. Existing Discharge Limits for Station SD001 (continued from page 12) State Discharge Restrictions (SDRs) Fecal Coliform: The limit for fecal coliform has been developed to meet state discharge restrictions specified under Minn. R Phosphorus: The 1.0 mg/l total phosphorus (TP) limit is required by Minn. R The concentration limit is considered a state discharge restriction analogous to a technology based limit. Technology Based Effluent Limits (TBELs) The Total Suspended Solids (TSS), and ph, are technology-based limits developed for achieving secondary treatment standards. These limits are specified in 40 CFR and in Minn. R Water Quality Based Effluent Limits (WQBELs) 5-Day Carbonaceous Biochemical Oxygen Demand (CBOD 5 ): The 5 mg/l CBOD 5 concentration limit is a WQBEL based upon Minn. R At this concentration, the Facility will not contribute to the receiving water DO impairment. Un-ionized Ammonia: The un-ionized ammonia effluent limits are WQBELs based on the designated use classification of the receiving water and a stream to effluent dilution ration under low flow conditions less than 20:1. The seasonal ammonia limits are calculated using the 30Q10 as the stream flow. Total Residual Chlorine (TRC): The TRC limit is the final acute value for chlorine found in Minn. R This limit is determined to be necessary to protect the use classification of the receiving water. Total Suspended Solids (TSS): The TSS mass load limit is frozen at 215 kg/day. This limit caps the mass discharge of mercury which is contained in the Facility s TSS. Proposed Permit Effluent Limits The limits and monitoring requirements for the draft reissued Permit are presented in Tables 5 and 6. These tables list both water quality and technology-based effluent limits. 13

14 Table 5. Proposed Effluent Limits for Draft Reissued Permit MN

15 Table 6.Proposed Effluent Limits for Draft Reissued Permit MN (continued from page 14) 15

16 State Discharge Restrictions (SDRs) The limit for fecal coliform has been developed to meet state discharge restrictions specified under Minn. R Technology Based Effluent Limits The Total Suspended Solids (TSS), and ph, are technology-based limits developed for achieving secondary treatment standards. These limits are specified in 40 CFR and in Minn. R Water Quality Based Limits Background The discharge is located on Jewitt s Creek. Jewitt s Creek is a Class 2C water. The discharger has submitted three chronic WET tests and three priority pollutant scans since The average dry weather (ADW) design flow is used to calculate water quality-based effluent limits under critical low flow stream conditions. The ADW for this facility is 2.5 mgd. The low flow condition is defined by the once-in-ten-year weekly average flow (7Q 10 ), which is determined to be mgd (0.01 cfs). The dilution ratio is :1, river low flow to effluent flow at the ADW. The analysis below is based on data submitted to date. Reasonable Potential for Chemical Specific Pollutants (40CFR122.44(d)(1)) Federal regulations require the 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. The priority pollutant scan information of the effluent was evaluated using reasonable potential procedures. All of the organic priority pollutants were below the level of detection, except for di-2- ethylhexylphalate (DEPH). Total nickel and total zinc were the only two metals detected in these priority pollutant scans. No reasonable potential to cause or contribute to an exceedence of a WQS was found for nickel or zinc. However, reasonable potential to cause or contribute to an exceedence of a WQS was found for DEPH. This exceedence is based on one positive detection of DEPH. DEPH is often a result of lab contamination during the cleaning of laboratory equipment. Environmental Analysis and Outcomes (EAO) staff recommend sampling 2x/yr for DEPH to determine if there is a real need for a WQBEL for DEPH. During the past permit cycle, however, this facility did routinely monitor for total copper, total selenium, and total silver in their effluent. In addition, positive concentration of total nickel, total zinc, and DEPH were found in the three priority pollutant scans. An evaluation was performed determine if there was reasonable potential to cause or contribute to a water quality standards for total copper, total selenium total silver, total nickel, total zinc, and DEPH at this facility. 16

17 From the table below, total copper and total selenium indicated no reasonable potential to cause or contribute to an excursion above the applicable water quality standard. Reasonable potential to cause or contribute to an excursion above the applicable water quality standard, however, was found for total silver at this facility. The following table contains the inputs to the reasonable potential analysis for total copper, total silver, and total selenium. 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. 17

18 Table 7. Inputs to the Reasonable Potential Analysis Parameter Cu (ug/l) Ag (ug/l) Se (ug/l) Ni (ug/l) Zn (ug/l) DEPH (ug/l) Max Measured Value # data points PEQ Plant flow ADW (mgd) Rec. water flow, 7Q10(mgd) Background Conc Continuous Std (cs) ppm hard Maximum Std (ms) none 400 ppm hard Final Acute Value (FAV) none 364 ppm hard Mass Balance -cs Mass Balance -ms #VALUE! Coeff of Variation (CV) Long Term Avg-cs Long Term Avg-ms #VALUE! Preliminary Effl limits: Daily Max Monthly Ave (2x/month) Reasonable Potential PEQ>Daily max FALSE TRUE FALSE FALSE FALSE TRUE PEQ>Montky Ave TRUE TRUE TRUE FALSE FALSE TRUE PEQ> FAV FALSE FALSE FALSE FALSE FALSE FALSE Final Reasonable Potential Yes Yes Yes No No Yes Notes Three of the four WET tests have been submitted. All three WET tests have <1.0 Tuc for all species tested- No Reasonable Potential Background conc set to 0 ppb, because there is no background monitoring station Di-2-ethylhexylphthalate (DEPH) had one positive result, most likely due to lab contamination recommend monitoring Reasonable Potential Conclusions Total Silver: Reasonable potential to cause or contribute to the excursion above a water quality standard has been indicated for silver. The MPCA is proposing to include a daily maximum limit of

19 micrograms per liter (ug/l) total silver and a monthly average limit of 0.95 ug/l total silver. This limit is a new limit based on new available data from the Facility s effluent monitoring. Total Copper: The MPCA is proposing to include a WQBEL for copper. Effluent limits were derived from water quality standards pursuant to 40 CFR (d)(1)(vii)(a). The proposed limits include a daily maximum 38 ug/l and a monthly average of 22 ug/l. Total Selenium: The MPCA is proposing to include a WQBEL for selenium. Effluent limits were derived from water quality standards pursuant to 40 CFR (d)(1)(vii)(a). The MPCA is proposing to include a daily maximum limit of 8.23 ug/l and a monthly average limit of 4.75 ug/l. Reasonable Potential Conclusions for Di-2-ethyhexykphthalate (DEPH): Reasonable potential to cause or contribute to the excursion above a water quality standard has been indicated for DEPH. This exceedence is based on one positive detection of DEPH. DEPH is often a result of lab contamination during the cleaning of laboratory equipment. Environmental Analysis and Outcomes (EAO) staff recommend sampling two times per year for DEPH to determine if there is a real need for a WQBEL for DEPH. Mercury: This facility has had an existing 6.9 nanogram per liter (ng/l) 12 month rolling monthly average total mercury limit. Because of an agreement reached with U.S. EPA Region 5 in 2012, all NPDES Permits which have shown reasonable potential to cause or contribute to the exceedence of a chemical specific limit must have a daily maximum WQBEL and a monthly average WQBEL. As such, the 6.9 ng/l 12 month rolling average total mercury limit must be replaced. Environmental Analysis and Outcomes (EAO) staff did a new reasonable potential analysis to establish a daily maximum and a monthly average limit. Because the majority of the individual mercury data was below analytical detection limit, EAO staff used a default coefficient of variation (CV) of 0.6 to develop the new mercury WQBELs for this facility. Based on this analysis, EAO staff recommends the following updated mercury WQBELs for this facility: Daily maximum = 16.8 ng/l Monthly average = 9.7 ng/l 5-Day Biochemical Oxygen Demand (CBOD 5 ): The 5 mg/l CBOD 5 concentration limit is a water WQBEL based upon Minn. R At this concentration, the Facility will not contribute to the receiving water DO impairment. Un-ionized Ammonia: The un-ionized ammonia effluent limits are WQBELs. They are based on the designated use classification of the receiving water and a stream to effluent dilution ration under low flow conditions less than 20:1. The seasonal ammonia limit is calculated using the 30Q10 as the stream flow. Total Residual Chlorine (TRC): The limit for TRC is a WQBEL. The TRC limit is the final acute value for chlorine found in Minn. R This limit is determined to be necessary to protect the use classification of the receiving water. 19

20 Annual Total Phosphorus (TP) Limit: In 2004, the Litchfield WWTF (Facility) received a 1.0 milligram per liter (mg/l) TP limit as required by Minn.R The concentration limit is considered a state discharge restriction analogous to a technology based limit. During a recent review it was determined that the Facility has reasonable potential to cause or contribute to the excess nutrient impairment in Lake Pepin and is therefore required to have an additional water quality based effluent limit (WQBEL). The recommended TP effluent limit (2,619 kg per year) in the draft Permit is a WQBEL which was derived from the draft waste load allocation which in turn is derived from the water quality standard that the receiving water must meet to support designated uses. State nondegradation rules (Minn.R , subp.4) require that the agency determine if additional control measures be taken when new or expanded significant discharges are proposed. An expanded significant discharge of a pollutant is defined as one that expands by more than 0.2 mgd, to any water other than a class 7 limited resource value water, over its nondegradation baseline flow such that its load of pollutants also increases. Litchfield s nondegradation design flow is estimated to be 1.73 mgd. The oldest phosphorus data on record, prior to the implementation of their 1.0 mg/l TP limit, is mg/l ( ). This equates to a maximum potential load of 25,170 kg/yr. Despite the request for an expanded and re-rated flow, the recommended limit (2,619 kg/yr) is a fraction of the nondegradation load. Therefore, re-rating does not constitute an expanded significant discharge and a nondegradation review of TP is not justified at this time. Whole Effluent Toxicity Testing: The permittee has chronic Whole Effluent Toxicity (WET) monitoring as a requirement. The permittee has chronic WET testing because the ratio of the 7Q10 low flow of the receiving water compared to the facility s ADW Flow is less than or equal to 20:1. A reasonable potential evaluation was done on the chronic WET tests to determine if there was cause to exceed the WET monitoring threshold value of 1.0 Toxic Unit chronic (TUc). Three of the four WET test associated with the current permit have been submitted. For each of the three WET tests, each species had <1.0 TUc. As such, no reasonable potential was found to exceed the monitoring threshold of 1.01 TUc. Because no reasonable potential has been found, a monitoring threshold value of 1.0 TUc has been established. The 1.0 TUc is a monitoring threshold value, not a WET limit. The following monitoring is included in the draft permit: Annual WET testing done once per year. If the permit exceeded five years, there will be an additional WET test for each year that exceeds the five year permit cycle. If the monitoring threshold value of 1.0 TUc is exceeded for any one WET test, the facility will perform two WET retests to determine if a Toxicity Reduction Evaluationis needed. Additional Requirements Mercury Minimization Plan (MMP): The Limits and Monitoring section of this draft Permit contains requirements for influent and effluent mercury monitoring and for submittal of an MMP. These requirements were added in response to the U.S. EPA s approval of the Minnesota statewide mercury TMDL plan. In addition to the sampling required in the Limits and Monitoring section of this draft Permit, the City is required to sample effluent quarterly for dissolved mercury with a concurrent TSS grab sample. The data will be recorded on a custom supplemental form provided by the MPCA and must be submitted with the DMR for the last month of each quarter. The specific language regarding this additional sampling is located in Chapter 2: Mercury Pollutant Minimization Plan of this draft reissued Permit. 20

21 Compliance Schedules The Facility is currently in compliance with its current NPDES/SDS Permit. This draft reissued Permit does not contain any compliance schedules since none are needed at this time. Salty Discharge Monitoring: In recent years, the MPCA staff became aware of issues associated with salty discharges from industrial and municipal discharges. As a result, the MPCA staff began to request additional monitoring for these facilities and also began assigning effluent limits to facilities that already have data which shows a reasonable potential to exceed a water quality standard. All industrial and municipal facilities with continuous, periodic/seasonal, or intermittent waste flows where the receiving water stream flow to effluent design flow dilution ratio under low flow conditions is less than 5:1 will be required to monitor effluent for the following parameters: chloride, Ca and Mg hardness as CaCO3, specific conductance, total dissolved solids, sulfates as SO4, bicarbonates (HCO3), sodium, calcium, magnesium, and potassium. Since the Facility s receiving water stream flow to effluent design flow is less than 5:1, this draft Permit contains the above-mentioned monitoring requirements. These parameters shall be sampled once a month. The data will be recorded on a Salty Discharge Supplemental Form provided by the MPCA, and the form must be submitted with the monthly DMR. Please refer to the Limits and Monitoring section and Chapter 4, Surface Discharge Stations, of the draft Permit for additional information. Additional Nitrogen Monitoring: The draft Permit requires additional monitoring for Nitrite plus Nitrate- Nitrogen and Total Kjeldahl at a frequency of two times per year for the five-year term of the Permit. This monitoring is being added to all reissued NPDES/SDS-permitted municipal facilities that have an annual wet weather design flow of 100,000 gallons per day (gpd) or greater. Biosolids This draft reissued permit authorizes the City to store and land apply domestic wastewater treatment biosolids in accordance with the provisions of Chapter 8 of this draft Permit and Minn. R. ch Total Facility Requirements (TFR) All NPDES permits issued in 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 outlined in Title 40, Code of Federal Regulations These conditions are listed in the Total Facility Requirements chapter of an NPDES permit. These requirements cover a wide range of areas including recordkeeping, sampling, equipment calibration, equipment maintenance, reporting, facility upsets, bypass, solids handling, changes in operation, facility inspections, and permit reissuance. Nondegradation and Anti-Backsliding In accordance with the MPCA s rules regarding nondegradation for all waters that are not ORVW, nondegradation review is required for any new or expanded significant discharge (Minn. R ). A significant discharge is: 1. A new discharge (not in existence before January 1, 1988) that is greater than 200,000 gpd to any water other than a Class 7 water; 2. An expanded discharge that expands by greater than 200,000 gpd that discharges to any water other than a Class 7 water; or 21

22 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. The flow rate used to determine significance is the design AWW flow. The January 1, 1988, design AWW flow for this Facility is 1.73 mgd. This Permit also complies with Minn. R regarding anti-backsliding. Any point source discharger of sewage, industrial, or other wastes for which an NPDES permit has been issued by the Agency that contains effluent limits more stringent than those that would be established by Minn. R 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) (2) (A) of the Clean Water Act, United States Code, title 33, section The rerating of the Litchfield WWTF that resulted in the increase of the capacity of the treatment facility from an AWW design flow of 2.37 mgd to 3.1 mgd is considered as an expansion of the WWTF. As per the MPCA rules anti-backsliding is not an issue with this permit because a new set of effluent limitations would be calculated and assigned to the expanded facility. However, the expansion triggers the nondegradation (anti-degradation) of all waters provision of the MPCA rules. The issue was analyzed and was determined that the expansion would not cause or contribute to the violation of the water quality standards in the receiving stream. The newly developed effluent limitations for the expanded facility required a CBOD 5 concentration limit of 5 mg/l and a summer ammonia effluent concentration limit of 2.1 mg/l. The expansion also resulted in a reduction of the effluent CBOD 5 permitted mass limit from 72 kg/day to 58.6 kg/day. This is consistent with Minn. R Also, according to a draft North Fork Crow and Lower Crow Bacteria, Turbidity and Low DOTMDL Assessment Report (April 2012) prepared by Wenck Associates, Inc., the River and Stream Water Quality Model (QUAL2K) a public domain model that is widely used and supported by EPA for TMDL development predicted that at the assigned concentration limits for CBOD 5 and ammonia, the discharge from the expanded Litchfield WWTF would not cause or contribute to the violations of the water quality standard for DO in the stream (Jewitts Creek). Based on the above assertion, it was determined that the nondegradation requirements of Minn. R have been satisfied. 22