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

Transcription

1 National Pollutant Discharge Elimination System (NPDES)/ State Disposal System (SDS) Permit Program Fact Sheet Permit Reissuance Permittee: City of Little Falls 900 Hilton Rd Little Falls, Minnesota PO Box 244 Little Falls, Minnesota Facility name: Little Falls Wastewater Treatment Facility 900 Hilton Rd Little Falls, Minnesota Current permit expiration date: December 31, 2012 Public comment period begins: August 16, 2016 Public comment period ends: September 15, 2016 Receiving water: Permitting contact: Mississippi River Class 1C, 2Bd, 3C, 4A, 4B, 5, 6 Water Robin Novotny 7678 College Road, Suite 105 Baxter, Minnesota robin.novotny@state.mn.us

2 Table of Contents Page Purpose and participation... 4 Applicable statutes... 4 Purpose... 4 Public participation... 4 Facility description... 5 Background information... 5 Facility location... 5 Outfall location... 5 Map of permitted facility... 5 Components and treatment technology... 6 Flow schematic... 7 Changes to facility or operation... 8 Significant industrial users (SIUs)... 8 Recent compliance history... 8 Table 1 Recent monitoring history March 2015 to February Receiving water(s)... 9 Use classification... 9 Table 2 Impairments... 9 Maximum Daily Load (TMDL)... 9 Existing permit effluent limits Technology based effluent limits (TBELs) Water quality based effluent limits (WQBELs) State Discharge Restriction Limits (SDRs) Table 3 Existing Permit Effluent Limits & Monitoring Proposed permit effluent limits Technology based effluent limits Water quality based limits State Discharge Restriction Limits (SDRs) Table 4 Proposed Permit Effluent Limits & Monitoring Proposed Phosphorus Limit Whole Effluent Toxicity and Reasonable Potential Reasonable Potential for Chemical Specific Pollutants(40 CFR (d)(1))... 15

3 Table 5 Reasonable Potential Analysis Additional requirements Mercury Minimization Plans (MMP) Compliance schedules Nitrogen Monitoring Requirements Salty Monitoring Requirements Industrial Stormwater Biosolids facility requirements (TFR) Nondegredation and anti backsliding... 19

4 Permit Reissuance Page 4 of 19 Purpose and participation Applicable statutes This fact sheet has been prepared according to the 40 CFR and and Minn R , subp. 3 in regards to a draft National Pollutant Discharge Elimination System (NPDES)/State Disposal System (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 one through three 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 one 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. Comments, petitions, and/or requests must be submitted by the last day of the public comment period to: Robin Novotny Minnesota Pollution Control Agency 7678 College Road, Suite 105 Baxter, MN 56425

5 Permit Reissuance Page 5 of 19 The permit will be reissued if the MPCA determines that the proposed Permittee or Permittees 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 Little Falls Wastewater Treatment Facility (Facility) is located in the NE ¼ of the NE ¼, Section 18, Township 40 North, Range 32 West. Outfall location The Facility outfall location (SD004) is located in the NE ¼ of the NE ¼, Section 18, Township 40 North, Range 32 West. Map of permitted facility

6 Permit Reissuance Page 6 of 19 Components and treatment technology Current information Major Components: 1 Equalization Tank (aerated wet weather tank) 1 Influent Flow Meter ( Parshall flume) 1 Bar Screen Manual 1 Bar Screen Mechanical 1 Aerated Grit Removal Tank 2 Primary Clarifiers 1 ABF Tower (Activated Biofilter Facility) 2 Intermediate Clarifiers 1 Activated Sludge contact stabilization, conventional, step feed (two tanks) 2 Final Clarifiers 2 Chlorine Contact Tanks (one follows EQ tank) 1 Dechlorination 1 Postaeration (cascading aeration) 1 Gravity Thickening 2 Aerated Sludge Holding Tanks 1 Centrifuge 1 Lime/Heat Stabilization Sludge Treatment Unit 1 Covered De Watered Biosolids Storage Area 1 Land Application of Biosolids 1 Odor Control Unit (Ammonia scrubber with a hydrochloric acid feed system and a biofilter) The Facility discharges continuously (SD004) to the Mississippi River (Class 1C, 2Bd, 3B, 3C, 4A, 4B, 5, 6 water). The Facility is designed to treat an average wet weather (AWW) flow of 2.4 million gallons per day (mgd), an average annual flow of 1.9 mgd, and an average dry weather (ADW) flow of 1.1 mgd, with a five day carbonaceous biochemical oxygen demand (CBOD5) strength of 177 milligrams per Liter (). Southeast Lift Station Bypass and West Lift Station Bypass are capable of discharging untreated wastewater to the Mississippi River. Treatment Facility Bypass/Overflow is a bypass point from the wet weather holding basin to the outfall pipe. Should the wet weather holding basin overflow, the wastewater is discharged to a wet weather chlorine contact chamber for disinfection before discharge to the Mississippi River. This permit includes a new phosphorus effluent limit and a compliance schedule to achieve compliance. The construction schedule includes two different tracks for meeting the proposed total phosphorus effluent limit. Track One covers construction within the existing Facility footprint. Track Two takes in to consideration the additional time needed, if during the planning and design process, it is determined that existing site constraints require a new Facility location to accommodate all the proposed changes. Historically, the city of Little Falls owned and operated the pretreatment facility for Central Minnesota Ethanol Cooperative. The Wastewater Treatment Facility (WWTF) accepted wastewater from the ethanol facility which was first processed through the pretreatment facility. The ethanol facility has taken over operation and ownership of the pretreatment facility. The ethanol facility has installed a closed loop water reuse system and has disconnected the pipe between the WWTF and the ethanol plant which eliminates the pretreatment facility discharge to the WWTF. With this pipe disconnection, a major portion of the ethanol plant flow discharging to the WWTF was eliminated. However, the ethanol plant will still be discharging its domestic wastewater, ion exchange softener regeneration water, cooling tower bleed and boiler blowdown to the city s sanitary sewer.

7 Permit Reissuance Page 7 of 19 Those portions of the Mississippi River from Lake Itasca to the southerly boundary of Morrison County that are included in the Mississippi Headwaters Board comprehensive plan dated February 12, 1981, were designated as Outstanding Resource Value Waters (ORVW) on November 5, This discharge is located between designated ORVW reaches. The calculated design AWW flow of this Facility on the date of ORVW designation was 2.4 mgd. In accordance with the MPCA 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 gallons per day (gpd) to any water other than a Class 7 water or 2) an expanded discharge that expands by greater than 200,000 gpd that discharges to any 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. The flow rate used to determine significance is the design AWW flow. The January 1, 1988, design AWW flow for this Facility is 2.4 mgd. Flow schematic

8 Permit Reissuance Page 8 of 19 Changes to facility or operation Facility improvements or modifications are required to accommodate phosphorus removal. The Facility shall complete the actions and submit information for these improvements under the terms of the Compliance Schedule under section of the reissued permit. The Significant Industrial Users (SIU), Central Minnesota Ethanol Cooperative has taken over operation and ownership of the pretreatment facility. The ethanol facility has installed a closed loop water reuse system and has disconnected the pipe between the City s WWTF and the ethanol plant which eliminates the pretreatment facility discharge to the City s WWTF. A major portion of the ethanol plant flow discharging to the WWTF was eliminated. However, the ethanol plant is still discharging from an additional discharge point, domestic wastewater, ion exchange softener regeneration water, cooling tower bleed and boiler blowdown to the city's WWTF. Significant industrial users (SIUs) There are two SIU that contribute process wastewater to the Facility. Anderson Custom Process is a drying process company and contributes 25,000 gallons per day (gpd) of process wastewater. The principle product or raw materials are starches and carbohydrates. The company has a pretreatment agreement with the Facility which includes local limits. Central Minnesota Ethanol Cooperative discharges domestic wastewater, ion exchange softener regeneration water, cooling tower bleed and boiler blowdown to the Facility. The contribution to the Facility is 20,000 to 25,000 gpd. The company has a pretreatment agreement with the Facility which includes local limits. Recent compliance history The most recent MPCA inspection of the Facility occurred on May 5, According to the May 15, 2015, inspection report, there were no violations of the NPDES/SDS Permit No.. The report indicates that the Facility appears to be in good working condition and is well maintained and cared for. Table 1 Recent monitoring history March 2015 to February 2016 Parameter Limit Type Limit Units Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb CBOD5 CalMoAvg CBOD5 CalMoAvg 227 kg/d CBOD5 MxCalWkAvg CBOD5 MxCalWkAvg 363 kg/d CBOD5 % MnCalMoAvg 85 % Removal Chlorine, DailyMax Residual Fecal CalMoGeoMn 200 #/100ml Coliform Mercury, CalQtrMax ng/l Nitrogen, CalMoAvg Ammonia Oxygen, CalMoMin Dissolved ph 9 SU ph CalMoMin 6 SU Phosphorus CalMoAvg kg/d Phosphorus CalMoAvg TSS CalMoAvg TSS CalMoAvg 272 kg/d TSS MxCalWkAvg TSS MxCalWkAvg 408 kg/d TSS % Removal MnCalMoAvg 85 %

9 Permit Reissuance Page 9 of 19 Receiving water(s) Use classification The receiving water is the Mississippi River a Class 1C, 2Bd, 3C, 4A, 4B, 5, 6 Water. Minn. R , Water Use Classifications for Waters of the State Subp. 2. Class 1 waters, domestic consumption. Domestic consumption includes all waters of the state which are or may be used as a source of supply for drinking, culinary or food processing use of other domestic purposes, and for which quality control is or may be necessary to protect the public health, safety, or welfare. Subp. 3. Class 2 waters, aquatic life and recreation. Aquatic life and recreation includes all waters of the state which do or may support fish, other aquatic life, bathing boating or other recreational purposes, and where quality control is or may be necessary to protect aquatic or terrestrial life or their habitats, or the public health, safety, or welfare. Subp. 4. Class 3 waters, industrial consumption. Industrial consumption includes all waters of the state which are or may be used as a source of supply for industrial process or cooling water, or any other industrial or commercial purposes, and for which quality control is or may be necessary to protect the public health, safety, or welfare. Subp. 5. Class 4 waters, agriculture and wildlife. Agriculture and wildlife includes all waters of the state which are or may be used for any agriculture purposes, including stock watering and irrigation, or by waterfowl or other wildlife, and for which quality control is or may be necessary to protect terrestrial life and its habitat or the public health, safety, or welfare. Subp. 6. Class 5 waters, aesthetic enjoyment and navigation. Aesthetic enjoyment and navigation includes all waters of the state which are or may be used for any form of water transportation or navigation, or fire prevention, and for which quality control is or may be necessary to protect the public health, safety, or welfare. Subp. 7. Class 6 waters, other uses. Other uses includes all waters of the state which are or may serve the above listed uses or any other beneficial uses not listed herein, including without limitation any such uses in this or any other state, province, or nation of any waters flowing through or originating in this state, and for which quality control is or may be necessary for the above declared purposes, or to conform with the requirements of the legally constituted state or national agencies having jurisdiction over such waters, or any other considerations the agency may deem proper. Table 2 Impairments AUID REACH_NAME REACH_DESC USE_CLASS CAT APPRVD Mississippi River Little Falls Dam to Swan R 1C, 2Bd, 3C 4A HgF Mississippi River End HUC (below Swan R) to Two R 1C, 2Bd, 3C 4A HgF Maximum Daily Load (TMDL) Mercury The statewide mercury Maximum Daily Load (TMDL) was approved March 27, 2007, with the implementation plan approved in For more information on the Mercury TMDL and implementation plan, refer to wwprm1 16. pdf.

10 Permit Reissuance Page 10 of 19 Lake Pepin TMDL Effluent from the Facility is discharged to the Mississippi River upstream of Lake Pepin, a reservoir on the Mississippi River. In 2002, Lake Pepin was placed on the Federal Clean Water Act Section 303(d) list of impaired waters due to excess nutrients. A TMDL study is currently being developed and a significant portion of the modeling analysis has been completed. Information regarding the proposed total phosphorus Water Quality Based Effluent Limits (WQBEL) that are included in the draft permit is included below under the heading Proposed Phosphorus Effluent Limit below. Existing permit effluent limits The limits and monitoring requirements in the current permit are presented in Table 3 and list WQBEL; technology based effluent limits and state discharge restriction limits. Technology Based Effluent Limits (TBELs) The CBOD 5, total suspended solids (TSS), potential for Hydrogen (ph), and percent removal limits are technology based limits developed for achieving secondary treatment standards. These limits are specified in 40 CFR , Minn. R and Minn. R Water quality based effluent limits (WQBELs) The total residual chlorine limit is a water quality based effluent limit. This limit is based on the designated use classification of the receiving water. The total residual chlorine limit 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. State discharge restriction limits (SDRs) The fecal coliform bacteria limit is a state discharge limit specified under Minn. R , subp. 1. Table 3 Existing Permit Effluent Limits and Monitoring Parameter Limit Units Limit Type Effective Period Sample Type Frequency Notes SD004: Surface Discharge Station CBOD5 227 kg/day CalMoAvg 3 x Week CBOD5 25 CalMoAvg 3 x Week CBOD5 363 kg/day MxCalWkAvg 3 x Week CBOD5 40 MxCalWkAvg 3 x Week CBOD5 % Removal 85 % MnCalMoAvg Calculation 3 x Week Chlorine Residual Daily Grab 1 x Day 4 Maximum Fecal Coliform 200 #100ml CalMoGeoMn Apr Oct Grab 3 x Week Mercury, Nitrogen, Ammonia Monitor Only Monitor Only ng/l CalQrtMax Grab 1 x Quarter 3 CalMoAvg 1 x Month

11 Permit Reissuance Page 11 of 19 Oxygen, Dissolved Monitor CalMoMn Grab 1 x Day 1 Only ph 9 SU Grab 1 x Day 1 ph 6 SU CalMoMn Grab 1 x Day 1 Phosphorus, Monitor kg/day CalMoAvg 1 x Week Only Phosphorus, Monitor CalMoAvg 1 x Week Only TSS 272 kg/day CalMoAvg 3 x Week TSS 30 CalMoAvg 3 x Week TSS 408 kg/day MxCalWkAvg 3 x Week TSS 45 MxCalWkAvg 3 x Week TSS % Removal 85 % MnCalMoAvg Calculation 3 x Week Proposed permit effluent limits The limits and monitoring requirements for Station SD004 for the draft reissued Permit are presented in Table 4. This table lists water quality based effluent limits; technology based effluent limits, and state discharge restriction limits. In addition, the Facility will be monitoring for the salty parameters. Technology Based Effluent Limits (TBEL) The CBOD 5, TSS, ph, and percent removal limits are technology based effluent limits developed for achieving secondary treatment standards. These limits are specified in 40 CFR , Minn. R and Minn. R Water Quality Based Limits (WQBEL) The total phosphorus and total residual chlorine limits are WQBEL. The total residual chlorine limit is the final acute value for chlorine found in Minn. R The proposed phosphorus limit is based on Minn. R , subp. 8, and Minn. R to protect downstream waters from eutrophication. State Discharge Restriction Limits (SDRs) The fecal coliform bacteria limit is a state discharge limit as specified in Minn. R , subp. 1. Table 4 Proposed Permit Effluent Limits & Monitoring Discharge limitations Monitoring requirements Parameter /Loading avg. /Loading max. /Loading Quality units /Conc. min. Quality /Conc. avg. Quality /Conc. max. Quality/ Conc. units Frequency Sample type Effective period Bicarbonates

12 Permit Reissuance Page 12 of 19 Discharge limitations Monitoring requirements Parameter /Loading avg. /Loading max. /Loading Quality units /Conc. min. Quality /Conc. avg. Quality /Conc. max. Quality/ Conc. units Frequency Sample type Effective period CBOD kg/day 25 CalMoAvg MaxCalWkAvg CalMoAvg 40 MaxCalWkAvg 3 times per week CBOD5 % Removal 85 MnCalMoAvg percent 3 times per week Calculation Calcium, Chloride, Chlorine Residual daily maximum day Fecal Coliform 200 CalMoGeoM organisms per 100 milliliter 3 times per week Grab Apr Oct Flow CalMoTot MG Monitor only. CalMoAvg MGD day Measurement, Continuous Hardness, Calcium & Magnesium Magnesium, CalYrMax Mercury, Dissolved ng/l Grab May, Sep Mercury, ng/l Grab May, Sep Nitrite Plus Nitrate Monitor only. CalMoAvg Nitrogen, Ammonia Monitor only. CalMoAvg

13 Permit Reissuance Page 13 of 19 Discharge limitations Monitoring requirements Parameter /Loading avg. /Loading max. /Loading Quality units /Conc. min. Quality /Conc. avg. Quality /Conc. max. Quality/ Conc. units Frequency Sample type Effective period Nitrogen, Kjeldahl Monitor only. CalMoAvg Nitrogen, Monitor only. CalMoAvg Oxygen, Dissolved CalMoMn day Grab ph 6.0 CalMoMn 9.0 SU day Grab Phosphorus, CalMoTot kg/mo Monitor only. CalMoAvg week Potassium, Sodium, TDS TSS kg/day 30 CalMoAvg MaxCalWkAvg CalMoAvg 45 MaxCalWkAvg 3 times per week TSS) % Removal 85 MnCalMoAvg percent 3 times per week Calculation TSS grab (Mercury) Grab May, Sep Specific Conductance micromhos per cm

14 Permit Reissuance Page 14 of 19 Discharge limitations Monitoring requirements Parameter /Loading avg. /Loading max. /Loading Quality units /Conc. min. Quality /Conc. avg. Quality /Conc. max. Quality/ Conc. units Frequency Sample type Effective period Sulfate, Proposed Phosphorus Effluent Limit The Facility has an AWW design flow of 2.4 mgd. The current permit does not include a total phosphorus limit. This area of the Mississippi is located in the north river nutrient region, and therefore, has TP and Chlorophyll a (Chl a) criteria of 50 micrograms per liter (µg/l) and 7 µg/l, respectively. Water samples used for water quality eutrophication assessments consist of TP and Chl a samples (n 12 TP and Chl a, each) collected during June September, representing at least two years of data within the last 10 years. Water quality impairments result when both TP and Chl a exceed their respective criteria concentrations. For this assessment, samples used were collected approximately 12 miles downstream of Little Falls WWTF, along the Mississippi River. Water quality suggest nutrient data are meeting eutrophication criteria. TP and Chl a concentrations were 53 µg/l (n = 64) and 3 µg/l (n = 12), respectively. Even though TP is slightly over the nutrient criteria, it is not considered impaired because only one nutrient parameter is elevated. Under low flow conditions, point sources are typically the dominant source of nutrient loading. The 80 th percent flow exceedence low flow condition and associated TP loading was used to identify point source impacts on the receiving water. The United States Geological Survey (USGS) gage ( ) and surface monitoring station (S ) data, located on the Mississippi River near Royalton, MN (approximately 12 miles downstream from Little Falls WWTF), were used. The data demonstrates that under low flow conditions, when point sources are the most significant contributor, the receiving water is meeting its nutrient criteria. Given that the current actual load is greater than the proposed effluent limit, it is reasonable to conclude that the recommended limit will result in a decrease in ambient TP, thereby not causing or contributing to an exceedance of the pending river eutrophication standards in the immediate receiving water. As such, more restrictive TP limits protective of the immediate receiving water in the Mississippi River are not necessary. In 2002, Lake Pepin was placed on the federal Clean Water Act Section 303(d) list of impaired waters due to excess nutrients. A Maximum Daily Load (TMDL) study is currently being developed and a significant portion of the modeling analysis has been completed. Phosphorus is the primary nutrient responsible for excess algal growth in Lake Pepin. 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 WQBEL. When determining RP, the Code of Federal Regulations also states that the MPCA shall use procedures which account for existing controls on point and nonpoint sources of pollution. Permittees are found to have RP for TP if: 1) they discharge upstream of a nutrient impaired waterbody, 2) they discharge at TP concentrations 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 reasons listed above, Little Falls is found to have RP for TP upstream of Lake Pepin. Therefore, Little Falls is required to have a TP WQBEL. It is recommended that the city of Little Falls receive a 2,653 kg/yr TP WQBEL which was derived from a draft TMDL waste load allocation (WLA) as described below. Draft WLAs in combination with other point and nonpoint reductions are sufficient to meet draft criteria in Lake Pepin designed to support the designated uses of this water resource.

15 Permit Reissuance Page 15 of 19 A computer water quality model for Lake Pepin was developed by MPCA modeling consultant, LimnoTech, to evaluate site specific eutrophication criteria and the reductions necessary to achieve these criteria (LimnoTech, 2009). The standards for Lake Pepin were determined to be TP and Chl a (Heiskary and Wasley, 2012). These standards were adopted in Minnesota Rule Within the model, all major sources of TP upstream of Lake Pepin were considered, and 21 separate scenarios were developed. Scenario 21 achieved compliance with the criteria and predicted that the following TP reductions from tributaries would be necessary: HSPF modeled reductions from the Minnesota River, 50% from the Cannon River, 20% from the Mississippi River upstream of Lock and Dam 1 and 20% from the St. Croix River. During the modeling process, MPCA staff simultaneously developed draft WLAs, compatible with reductions in scenario 21 for all NPDES dischargers within the contributing basin of Lake Pepin. All simulations represented point sources on a 12 basis. Categorical WQBELs using AWWDF or Maximum Daily Flow were developed for NPDES WWTFs in the Lake Pepin Basin using the general formula below: General Formula: MM WLA = (AWWDF x 0.8 TP x L/gal x 365 days/yr) City of Little Falls WWTP WLA: 2,653 kg/yr TP = (2.4 mgd x 0.8 x L/gal x 365 days/yr) These values are then implemented in permits as 12 rolling total kg/day mass values. Limits are evaluated on a ly basis to ensure compliance. This analysis demonstrates the facility does not have the potential to cause or contribute to river eutrophication impairment in the Mississippi River Brainerd Watershed, under permitted effluent conditions. Existing limits are sufficient for the immediate and downstream waters to meet RES. Nonetheless, it was determined that the facility has RP to cause or contribute to the excess nutrient impairment in Lake Pepin and is therefore required to have a WQBEL. The recommended TP effluent limit (2,653 kg/yr) in the draft permit is a WQBEL derived from the draft WLA which in turn is derived from the water quality standard that the receiving water must meet to support designated uses. Whole Effluent Toxicity and Reasonable Potential The discharge is located on the Mississippi River within a reach not designated as an ORVW. The ADW design flow is used to calculate WQBEL under critical low flow stream conditions. The ADW for this Facility is 1.1 mgd. The low flow condition is defined by the once in 10 year weekly average flow (7Q 10 ), which is determined to be mgd (685 cubic feet per second [cfs]). The dilution ratio is 402.5:1 river low flow to effluent flow at the ADW flow. The discharger has submitted four whole effluent toxicity (WET) test batteries and three priority pollutant scans since The analysis below is based on data submitted to date. Reasonable Potential for Chemical Specific Pollutants (40 CFR (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 WQBEL limit for that pollutant.

16 Permit Reissuance Page 16 of 19 The Facility submitted three priority pollutant scans during the past permit cycle. 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. 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. The priority pollutant scans did find concentrations of total copper (Cu), total arsenic (As) and total zinc (Zn) above reporting level concentrations. Reasonable Potential evaluations were done for total copper, total arsenic and total zinc based on priority pollutant scan data. Reasonable potential evaluations were also performed on total mercury (Hg) based on past quarterly sampling of total mercury of the Facility s effluent. From the table below total arsenic, total copper, total zinc and total mercury indicated no reasonable potential to cause or contribute to an excursion above the applicable water quality standard. No effluent limits are needed. Table 5. Reasonable Potential Analyses Parameter As(ug/L) Cu (ug/l) Zn (ug/l) Hg (ng/l) Max Measured Value Maximum Measured Value # data points PEQ Plant flow ADW (mgd) Receiving. water flow, 7Q10(mgd) Background Concentration Continuous Standard (cs) 176 Parts per million (ppm) hardness Maximum Standard (ms) 176 ppm hardness Final Acute Value (FAV) 148 ppm hardness Mass Balance ms Coeff of Variation (CV) Long Term Avg cs Long Term Avg ms Preliminary Effl limits: Daily Max Monthly Ave (2x/)

17 Permit Reissuance Page 17 of 19 Reasonable Potential PEQ>Daily maximum FALSE FALSE FALSE FALSE PEQ> FAV FALSE FALSE FALSE FALSE Final Reasonable Potential No No No No Notes: Background concentrations for copper and zinc taken from Gary Kimball's 2007 review. Mercury background set to chronic standard because of statewide TMDL No background for arsenic could be found Mercury Monitoring results of the effluent include 20 data points at a calculated coefficient of variable (CV) of Projected effluent quality is derived as an upper bound value from the highest value measured (5.8 nanograms per liter [ng/l]), and the determined variability (CV = ) and number of data points (20). The 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 ng/l) is applied at the point of discharge for the mass balance equation for the subsequent preliminary effluent limit calculations. Metals Table 5 contains the inputs to the reasonable potential analysis for total arsenic, total copper, total zinc and total 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 PEQs exceed PELs, a WQBEL is needed. Reasonable potential to cause or contribute to the exceedence of a water quality standard was not found for total arsenic, total copper and total zinc at this Facility. Whole Effluent Toxicity (WET) Minn. R , subp. 1 Minimum secondary treatment for municipal point source and other point source dischargers of sewage, specifies that the discharge shall not be acutely toxic or exceed the final acute value, unless the effluent satisfies acute whole effluent toxicity test conditions (i.e. less than 50 percent mortality for a sensitive organism). A discharge that exceeds mortality requirements of the rule requires a permit limit for WET. The Facility has submitted four acute WET tests since The acute toxicity (TUa) units determined for each of the tests were all less than TUa. Therefore, no RP for acute toxicity is indicated pursuant to Minn. R , subp. 1 and no effluent limit is needed. The recommendation for the permit is to include annual WET monitoring requirements. Additional Requirements Mercury Minimization Plans (MMP) The draft permit contains requirements for mercury monitoring and for submittal of a Mercury Minimization Plan (MMP) or updated MMP. These requirements were added in response to the U. S. Environmental Protection Agency s (EPA) approval of the Minnesota statewide Mercury TMDL plan. Specific mercury monitoring requirements are found in the Surface Discharge Station Chapters of this permit. These requirements include sampling for TSS via a grab sample taken at the same time as the mercury grab samples are taken.

18 Permit Reissuance Page 18 of 19 Compliance Schedules This Facility has been assigned a new WQBEL for TP (2,653 kg/yr). Because this Facility is not capable of achieving this limit at permit issuance, this draft permit contains a compliance schedule to allow the time needed to secure funding, evaluate the design, and build for advance nutrient removal technology. This permit contains a schedule to attain compliance with the final mass limit the schedule can be found in section The Facility will be required to attain compliance with the WQBEL no later than August 31, Nitrogen Monitoring Requirements The draft Permit includes influent and effluent monitoring for Ammonia Nitrogen, Nitrite plus Nitrate Nitrogen, Kjeldahl Nitrogen, and Nitrogen at a frequency of one time per for the five year term of the Permit. There is no nitrogen limit in the Permit. 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 have data showing 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 has a SIU which meets this criteria the draft permit contains the above mentioned monitoring requirements. These parameters shall be sampled once a. Please refer to the Limits and Monitoring section and Chapter 3, Surface Discharge Stations, of the draft Permit for additional information. Industrial Stormwater On April 5, 2015, the Industrial Stormwater General Permit (MNR050000) was issued. This permit addresses stormwater discharges associated with industrial activity for facilities that discharge stormwater to waters of the state, including Municipal Separate Storm Sewer Systems. The General Permit also addressed stormwater discharges associated with industrial activities at facilities that provide on site infiltration of industrial stormwater discharges associated with the Facility. For both industrial and municipal wastewater facilities, in lieu of obtaining coverage under both the General Permit and the individual NPDES permit, the MPCA has added the necessary industrial stormwater requirements language and limits and monitoring to this permit so that coverage under this NPDES permit alone will cover both permits. This Facility has applied for and obtained a Certification of No Exposure; therefore, this permit includes language regarding the No Exposure exclusion. Biosolids This draft reissued Permit authorizes the Permittee to store and land applies domestic wastewater treatment biosolids in accordance with the provisions in this draft permit and Minn. R. ch Facility Requirements (TFR) 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 outlines in 40 CFR , Minn. R and These conditions are listed in the Facility Requirements chapter of the NPDES/SDS Permit. These requirements cover a wide range of areas, including recordkeeping, sampling, equipment

19 Permit Reissuance Page 19 of 19 calibration, equipment maintenance, reporting, Facility upsets, bypasses, solids handling, changes in operation, Facility inspections, and permit modification and reissuance. Nondegredation and Anti Backsliding Those portions of the Mississippi River from Lake Itasca to the southerly boundary of Morrison County that are included in the Mississippi Headwaters Board comprehensive plan dated February 12, 1981 were designated as Outstanding Resource Value Waters (ORVW) on November 5, The discharge is located between designated ORVW reaches. In accordance with MPCA rules regarding nondegradation for ORVWs, nondegradation review is required for any new or expanded discharge where any change results in an increased mass loading of one or more pollutants (Minn. R ). The calculated design average wet weather flow of this facility as of November 5, 1984, and associated mass loading are the baseline design flow and mass loading. This baseline flow and mass loading will be used to determine whether nondegradation review is required for any change in the discharge. The discharge may also be subject to nondegradation review in accordance with Minn. R , Nondegradation for all waters. The calculated design AWW flow of this Facility on the date of ORVW designation was 2.4 mgd. This Permit also complies with Minn. R regarding anti backsliding. Any point source discharger of sewage, industrial, or other wastes for which a NPDES permit has been issued by the MPCA 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.