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

Transcription

1 National Pollutant Elimination System (NPDES)/ State Disposal System (SDS) Permit Program Fact Sheet Permit Reissuance Permittee: Facility name: City of Windom th Street PO Box 38 Windom, MN Windom Wastewater Treatment Facility 400 Drake Avenue South Windom, MN Current permit expiration date: August 31, 2015 Public comment period begins: April 25, 2018 Public comment period ends: June 25, 2018 Receiving water: Permitting contact: Des Moines River, West Fork Class 2B, 3C, 4A, 4B, 5, 6 water Amanda Wilkens 7678 College Road, Suite 105 Baxter, MN amanda.wilkens@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... 6 Components and treatment technology... 7 Flow schematic of existing facility... 7 Changes to facility or operation... 8 Flow schematic of proposed facility... 9 Significant industrial user (SIU)... 9 Recent compliance history Recent monitoring history Receiving water(s) Use classification Impairments Total Maximum Daily Load (TMDL) Expanded Bacteria and Total Suspended Solids Wasteload Allocations Justification Existing permit effluent limits Technology based effluent limits (TBELs) Water quality based effluent limits (WQBELs) State Restrictions (SDR) Proposed permit effluent limits Technology based effluent limits (TBELs) Water quality based effluent limits (WQBEL) State Restrictions (SDRs) Proposed Total Phosphorus Effluent Limit Proposed Five-Day Carbonaceous Biochemical Oxygen Demand (CBOD 5) Limit Reasonable potential analysis Requirements Associated with the Minnesota Antidegradation State Rule Chemical Specific... 24

3 Mercury Copper Salty Parameters Additional requirements Mercury Minimization Plan (MMP) Toxicity Reduction Evaluation (TRE) Whole Effluent Toxicity (WET) Testing Requirements Nitrogen ing Requirements Compliance Schedules Industrial Stormwater No Exposure Biosolids Variances Total facility requirements (TFR) Antidegradation and anti-backsliding... 30

4 Permit Reissuance Page 4 of 30 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 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: Amanda Wilkens Minnesota Pollution Control Agency 7678 College Road, Suite 105 Baxter, MN 56425

5 Permit Reissuance Page 5 of 30 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 The Windom Wastewater Treatment Facility (Facility) is located in the NW ¼ of the NE ¼, Section 36, Township 105 North, Range 36 West, Great Bend Township, Cottonwood County, Minnesota (latitude: N, longitude: W). The address for the Facility is 400 South Drake Avenue, Windom, Minnesota Outfall location The Facility outfall location () is located next to the Facility as described above. The outfall is a continuous discharge to the Des Moines River. Latitude and longitude of the outfall is N and W, respectively.

6 Permit Reissuance Page 6 of 30 Map of permitted facility

7 Permit Reissuance Page 7 of 30 Components and treatment technology The existing Class B Facility (Phase 1) consists of the following components: Collection System Gravity and/or pressure Preliminary Treatment Mechanical and manual screening Preliminary Treatment Grit separator, grit cyclone, grit dewatering Secondary Treatment Extended aeration activated sludge process with four aeration basins Secondary Treatment Final clarifiers (two) Tertiary Treatment Media filtration Disinfection Chlorine contact with dechlorination Solids Handling Sludge thickening, heated aerobic digester, sludge storage tanks (three) Solids Disposal Land application The Facility has a continuous discharge to the Des Moines River (Class 2B, 3C, 4A, 4B, 5, and 6 water), and is designed to treat an wet weather (AWW) flow of 1.83 million gallons per day (mgd), and an dry weather (ADW) flow of 1.13 mgd. The Facility has an influent five-day carbonaceous biochemical oxygen demand (CBOD 5) strength of 98 (mg/l) based on AWW design flow. Flow schematic of existing facility

8 Permit Reissuance Page 8 of 30 Changes to facility or operation The permit application indicates the existing Facility will undergo an improvement project. The proposed Facility (Phase 2) will have the following major components post-construction: Collection System Gravity and/or pressure Preliminary Treatment Mechanical fine screens (two) Preliminary Treatment Grit separator, grit cyclone, grit dewatering Secondary Treatment/Advanced Treatment Biological phosphorus removal; aeration basins (three) with anaerobic (one) and anoxic selector (one) tanks Secondary Treatment Final clarifiers (two) Tertiary Treatment Chemical addition for phosphorus precipitation Tertiary Treatment Cloth disc filers (two) Disinfection Chlorination contact basin with dechlorination and reaeration basin Solids Handling Heated aerobic digester Solids Handling Biosolids storage tanks (three) Solids Disposal Land application Following the completion of the improvement project, the Windom WWTF will be reclassified as a Class A Facility. The modified Facility will continue to utilize the continuous discharge () to the Des Moines River (Class 2B, 3C, 4A, 4B, 5, and 6 water). The modified Facility will include a design flow expansion from an AWW flow of 1.83 mgd to 1.93 mgd, and an expansion of ADW flow from 1.13 mgd to mgd. The Facility is designed to treat an daily load of 1,094 pounds per day (lb/day CBOD 5, 1,184 lb/day Total Suspended Solids (TSS), and 365 lb/day Total Kjeldahl Nitrogen (TKN).

9 Permit Reissuance Page 9 of 30 Flow schematic of proposed facility Significant industrial user (SIU) There are three SIUs that contribute wastewater to the Facility. Prime Pork is a meat processing facility and contributes a total flow of 1.0 mgd of wastewater to the Facility. The principle product or raw materials are pork processing. The company has a pretreatment agreement with the Facility which includes local limits. Windom Wash is a livestock truck wash and contributes a total flow of mgd of wastewater to the Facility. The company has a pretreatment agreement with the Facility which includes local limits. The Toro Company is manufacturing company that does a small amount of metal manufacturing and contributes a total flow of 10,000 gallons per day (gpd) of wastewater to the Facility. The principle product or raw materials are small equipment such as lawn mowers, snow blowers, golf mowers, and some contractor equipment. The company has a pretreatment agreement with the MPCA and the Facility. They currently do not have a control mechanism or local limits with the Facility.

10 Permit Reissuance Page 10 of 30 Recent compliance history The most recent MPCA inspection of the Facility occurred on February 2, 2017, by Brad Gillingham of the MPCA. The CEI consisted of a visual inspection of the Facility and a discussion with Facility staff. In addition, there was a review of the ly ing Reports (DMRs) for the time period from January 2014 through December The Facility s biosolids land application sites were not inspected due to snow cover. Based on the results of the CEI, one effluent violation of the terms and conditions set forth in the NPDES/SDS Permit No. was noted as follows: Alleged Violations 1. NPDES/SDS Permit, Limits and ing Requirements, : The City reported one effluent limit violation with the conditions of the NPDES/SDS Permit during the review period. Date Parameter Reported Value Limit Limit Type March 2016 CBOD 12 mg/l 10 mg/l Maximum Calendar Week Average Corrective Actions 1. The City shall continue to take actions to avoid effluent violations in the future. The MPCA discussed the violation and the corrective action with the City. No further correspondence is required at this time The February 2, 2017 report also indicated the Facility has failed Whole Effluent Toxicity (WET) testing for Ceriodaphnia dubia along with subsequent re-testing. The Facility was and continues to be under a Toxic Reduction Evaluation (TRE) plan with the MPCA and the MPCA Environmental Analysis and Outcomes (EAO) Division had approved the TRE. It was determined that high Nitrate levels are the contributing factor. At the time, the City was planning to complete a Facility upgrade by May The reissued Facility permit will include a Total Nitrogen limit and Total Phosphorus limit. WET testing will resume at the Facility when final limits come into effect in the reissued Facility permit.

11 Permit Reissuance Page 11 of 30 Recent monitoring history Table 1: Surface Station ing Report Summary from January 2017 through December 2017 Parameter Limit Units Limit Type Jan-17 Feb-17 Mar-17 Apr-17 May-17 Jun-17 Jul-17 Aug-17 Sep-17 Oct-17 Nov-17 Dec-17 Bicarbonates (HCO3) mg/l CalMoMax CBOD 5 5 mg/l CalMoAvg CBOD 5 25 mg/l CalMoAvg CBOD 5 34 kg/d CalMoAvg CBOD kg/d CalMoAvg CBOD 5 10 mg/l MxCalWkAvg CBOD 5 40 mg/l MxCalWkAvg CBOD 5 69 kg/d MxCalWkAvg CBOD kg/d MxCalWkAvg CBOD 5 % Removal 85 % MnCalMoAvg Calcium, Total (as Ca) mg/l CalMoMax Chloride, Total mg/l CalMoMax Chlorine, Total Residual mg/l DailyMax Copper, Dissolved (as Cu) ug/l CalQtrMax Copper, Total (as Cu) ug/l CalQtrMax Fecal Coliform 200 #/100ml CalMoGeoMn Flow mgd CalMoAvg Flow mgd CalMoMax Flow Mgal CalMoTot Hardness, Calcium & Magnesium, Calculated (as CaCO3) mg/l CalMoMax Magnesium, Total (as Mg) mg/l CalMoMax Mercury, Total (as Hg) ng/l CalQtrMax Nitrite Plus Nitrate, Total (as N) mg/l CalMoAvg Nitrogen, Ammonia, Total (as N) 1 mg/l CalMoAvg Nitrogen, Ammonia, Total (as N) 3.3 mg/l CalMoAvg

12 Permit Reissuance Page 12 of 30 Nitrogen, Ammonia, Total (as N) 7 kg/d CalMoAvg Nitrogen, Ammonia, Total (as N) 7.2 mg/l CalMoAvg Nitrogen, Ammonia, Total (as N) 8.2 mg/l CalMoAvg Nitrogen, Ammonia, Total (as N) 23 kg/d CalMoAvg Nitrogen, Ammonia, Total (as N) 50 kg/d CalMoAvg Nitrogen, Ammonia, Total (as N) 57 kg/d CalMoAvg Nitrogen, Kjeldahl, Total mg/l CalMoAvg Oxygen, Dissolved 6 mg/l CalMoMin Oxygen, Dissolved 10 mg/l CalMoMin ph 9 SU CalMoMax ph 6 SU CalMoMin Phosphorus, Total (as P) kg/d CalMoAvg Phosphorus, Total (as P) mg/l CalMoAvg Potassium, Total (as K) mg/l CalMoMax Sodium, Total (as Na) mg/l CalMoMax Solids, Total Dissolved (TDS) mg/l CalMoMax Solids, Total Suspended (TSS) 30 mg/l CalMoAvg Solids, Total Suspended (TSS) 208 kg/d CalMoAvg Solids, Total Suspended (TSS) 45 mg/l MxCalWkAvg Solids, Total Suspended (TSS) 311 kg/d MxCalWkAvg Solids, Total Suspended (TSS) Percent Removal 85 % MnCalMoAvg Specific Conductance umhos/cm CalMoMax Sulfate, Total (as SO4) mg/l CalMoMax

13 Permit Reissuance Page 13 of 30 Receiving water(s) Use classification The Facility has a continuous discharge via surface discharge station to the West Fork of the Des Moines River. This water is classified as a Class 2B, 3C, 4A, 4B, 5, 6 water. Class 2 waters, aquatic life and recreation. Aquatic life and recreation includes all waters of the state that support or may support fish, other aquatic life, bathing, boating, or other recreational purposes, and for which quality control is or may be necessary to protect aquatic or terrestrial life or their habitats or the public health, safety, or welfare. Class 3 water, industrial consumption. Industrial consumption includes all waters of the state that 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. Class 4 waters, agriculture and wildlife. Agriculture and wildlife includes all waters of the state that 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. Class 5 waters, aesthetic enjoyment and navigation. Aesthetic enjoyment and navigation includes all waters of the state that 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. Class 6 waters, other uses and protection of border wars. Other uses includes all waters of the state that serve or may serve that uses in subparts 2 to 6 or any other beneficial uses not listed in this part, 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 declared purposes in this part, to conform with the requirements of the legally constituted state of national agencies having jurisdiction over such waters, or for any other considerations the agency may deem proper. More information on the classification of waters can be found in Minn. R Impairments The following table lists the current impairments for the receiving water. AUID or Lake ID# Waterbody Assessment Category & Subcategory Pollutants or Impairments Des Moines River : Windom Dam to Jackson Dam 5 Ammonia, unionized Des Moines River : Windom Dam to Jackson Dam 5 Dissolved oxygen Des Moines River : Windom Dam to Jackson Dam 5 Nutrient/eutrophication biological indicators Des Moines River : Windom Dam to Jackson Dam 4A Turbidity, Fecal Coliform

14 Permit Reissuance Page 14 of 30 Total Maximum Daily Load (TMDL) The following TMDL studies were used: Fecal Coliform and Total Suspended Solids West Fork Des Moines River Watershed Multiple Impairments TMDL was approved on December 18, 2008, by the U.S. EPA. Mercury Minnesota Mercury TMDL was approved on March 27, Expanded Bacteria and Total Suspended Solids Wasteload Allocations Justification The Windom WWTF is a continuous discharging mechanical system that has an AWW design flow of 1.83 mgd and includes one discharge monitoring point () that discharges to the West Fork Des Moines River. The permitted fecal coliform limit at is 200 organisms per 100mL (April through October). The permitted TSS limit at is 30 mg/l. The City of Windom is proposing to construct at the Windom WWTF, adding new components to the mechanical system and increasing the AWW design flow from 1.83 mgd to 1.93 mgd. This proposed expansion will require an expansion to the wasteload allocations (WLAs) for both bacteria and TSS in the West Fork Des Moines River Watershed Multiple Impairments TMDL. On December 18, 2008, the West Fork Des Moines River Watershed Multiple Impairments TMDL was approved by the U.S. Environmental Protection Agency (EPA). For WWTFs, the WLAs were calculated by multiplying AWW design flow for continuously discharging WWTFs, or the permitted discharge rate for controlled discharge pond facilities by the 126 organisms per 100 ml water quality standard. The Facility s fecal coliform effluent limit is intended to ensure complete effluent disinfection; therefore, as long as the WWTF s discharge is at or below this permit limit, the discharge will not contribute to violations of the water quality standard regardless of their fecal coliform load. An analysis of the effects of expanded WLAs, prepared by Tetratech for the Zumbro River Turbidity TMDL (Cleland 2011), demonstrates that current discharges can be expanded and new NPDES discharges can be added while maintaining water quality standards; provided the permitted NPDES/SDS effluent concentrations remain at or below the in-stream concentration targets. Fecal Coliform/E. coli The West Fork Des Moines River Watershed Multiple Impairments TMDL used an AWW design flow of 1.83 mgd to set the WLA at 14 billion organisms per day (b-org/day). The calculation for the proposed expansion will use an AWW design flow of 1.93 mgd. This is a difference of 0.10 mgd. Using the AWW design flow of 1.93 mgd, the WLA would be b-org/day mgd = cubic feet per second (cfs) 1.93 mgd = cfs cfs cfs = cfs This NPDES/SDS Permit authorizes the expansion of the WLA for the WWTF. Expansion of the WLA will not contribute to the E. coli impairment in the Des Moines River because the NPDES/SDS Permit s fecal coliform permitted discharge limit of 200 organisms per 100 ml is consistent with the water quality standard. As mentioned above, the difference between the design flows is 0.10 mgd, which is equal to cfs. This means an increase of cfs of flow from the WWTF to the Des Moines River, which in turn expands the E. coli loading capacity by 0.61 b-org/day. The discharge will not result in a decrease in the Des Moines River s water quality because fecal coliform bacteria loading capacity will increase as a result of the increased stream flow resulting from the discharge.

15 Permit Reissuance Page 15 of 30 Approved Wasteload Allocation Flow Increase E. coli Load Increase Modified Wasteload Allocation Windom WWTF WLA Expansion 14 b-org/day cfs 0.61 b-org/day b-org/day Des Moines River (AUID ) Loading Capacity Expansion cfs 0.61 b-org/day Total Suspended Solids The West Fork Des Moines River Watershed Multiple Impairments TMDL used an AWW design flow of 1.83 mgd to set the WLA at 208 kilograms per day (kg/day). The calculation for the proposed expansion will use an AWW design of 1.93 mgd. This is a difference of 0.10 mgd. Using the AWW design flow of 1.93 mgd, the WLA would be Conversion: 30 mg/l X 1.93 mgd X = kg/day 1.83 mgd = cubic feet per second (cfs) 1.93 mgd = cfs cfs cfs = cfs This NPDES/SDS Permit authorizes the expansion of the WLA for the WWTF. Expansion of the WLA will not contribute to the TSS impairments in the Des Moines River Headwaters Watershed because the NPDES/SDS Permit s 30 mg/l TSS discharge limit will ensure that the discharge does not have reasonable potential to cause or contribute to an exceedance of the applicable 65 mg/l TSS water quality standard. As mentioned above, the difference between the design flows is 0.10 mgd, which is equal to cfs. This means an increase of cfs of flow from the WWTF to the Des Moines River, which in turn expands the TSS loading capacity by kg/day. The discharge will not result in a decrease in the Des Moines River s water quality because TSS loading capacity will increase as a result of the increased stream flow resulting from the discharge. Approved Wasteload Allocation Flow Increase TSS Loading Capacity Increase Modified Wasteload Allocation Windom WWTF s WLA Addition 208 kg/day cfs kg/day kg/day Des Moines River Loading Capacity Expansion cfs kg/day Existing permit effluent limits The effluent limits and monitoring requirements in the existing permit are presented in Table 2 at the end of this section. This Table lists water quality based effluent limits, technology based effluent limits, and state discharge restrictions. Technology based effluent limits (TBELs) The CBOD 5, CBOD 5 percent removal, TSS, TSS percent removal, and potential for Hydrogen (ph) removal limits that have been included in this permit are technology based limits developed for achieving secondary treatment standards. These limits are specified in 40 CFR and Minn. R and Minn. R Water quality based effluent limits (WQBELs) The total ammonia nitrogen limit included in this permit is a WQBEL. WQBELs are established to meet applicable water quality standards. Under 40 CFR (d)(1)(i), all dischargers who have the reasonable potential to cause or contribute to an exceedance of a water quality standard are required to have a WQBEL.

16 Permit Reissuance Page 16 of 30 The total residual chlorine limit is a WQBEL. 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 Restrictions (SDR) The fecal coliform bacteria limit is a SDR specified in Minn. R , subp. 1. Table 2: Surface Station Existing Limits and ing Requirements Parameter Limit Units Limit Type Effective Period Frequency Bicarbonates (HCO3) Only mg/l CalMoMax 1 x Month CBOD 5 34 kg/d CalMoAvg Dec-Mar 2 x Week CBOD 5 5 mg/l CalMoAvg Dec-Mar 2 x Week CBOD 5 69 kg/d MxCalWkAvg Dec-Mar 2 x Week CBOD 5 10 mg/l MxCalWkAvg Dec-Mar 2 x Week CBOD kg/d CalMoAvg Apr-Nov 2 x Week CBOD 5 25 mg/l CalMoAvg Apr-Nov 2 x Week CBOD kg/d MxCalWkAvg Apr-Nov 2 x Week CBOD 5 40 mg/l MxCalWkAvg Apr-Nov 2 x Week CBOD 5 % Removal 85 % MnCalMoAvg 2 x Week Calcium, Total (as Ca) mg/l CalMoMax 1 x Month Chloride, Total Only mg/l CalMoMax 1 x Month Chlorine, Total Residual mg/l DailyMax 1 x Day Copper, Dissolved (as Cu) Only ug/l CalQtrMax 1 x Quarter Copper, Total (as Cu) Only ug/l CalQtrMax 1 x Quarter Fecal Coliform 200 #/100ml CalMoGeoMn Apr-Oct 2 x Week Flow Only mgd CalMoAvg 1 x Day Flow Only mgd CalMoMax 1 x Day Flow Only Mgal CalMoTot 1 x Day Hardness, Calcium & Magnesium, Calculated (as CaCO3) Only mg/l CalMoMax 1 x Month Magnesium, Total (as Mg) Only mg/l CalMoMax 1 x Month Mercury, Total (as Hg) Only ng/l CalQtrMax 1 x Quarter Nitrite Plus Nitrate, Total (as N) Only mg/l CalMoAvg Apr, Sep 1 x Month Nitrogen, Ammonia, Total (as N) 57 kg/d CalMoAvg Dec-Mar 2 x Week Nitrogen, Ammonia, Total (as N) 8.2 mg/l CalMoAvg Dec-Mar 2 x Week Nitrogen, Ammonia, Total (as N) 50 kg/d CalMoAvg Apr-May 2 x Week Nitrogen, Ammonia, Total (as N) 7.2 mg/l CalMoAvg Apr-May 2 x Week Nitrogen, Ammonia, Total (as N) 7 kg/d CalMoAvg Jun-Sep 2 x Week Nitrogen, Ammonia, Total (as N) 1 mg/l CalMoAvg Jun-Sep 2 x Week Nitrogen, Ammonia, Total (as N) 23 kg/d CalMoAvg Oct-Nov 2 x Week Nitrogen, Ammonia, Total (as N) 3.3 mg/l CalMoAvg Oct-Nov 2 x Week Nitrogen, Kjeldahl, Total Only mg/l CalMoAvg Apr, Sep 1 x Month Oxygen, Dissolved 6 mg/l CalMoMin Dec-Mar 1 x Day

17 Permit Reissuance Page 17 of 30 Oxygen, Dissolved 10 mg/l CalMoMin Apr-Nov 1 x Day ph 9 SU CalMoMax 1 x Day ph 6 SU CalMoMin 1 x Day Phosphorus, Total (as P) Only kg/d CalMoAvg 1 x Week Phosphorus, Total (as P) Only mg/l CalMoAvg 1 x Week Potassium, Total (as K) Only mg/l CalMoMax 1 x Month Sodium, Total (as Na) Only mg/l CalMoMax 1 x Month Solids, Total Dissolved (TDS) Only mg/l CalMoMax 1 x Month Solids, Total Suspended (TSS) 208 kg/d CalMoAvg 2 x Week Solids, Total Suspended (TSS) 30 mg/l CalMoAvg 2 x Week Solids, Total Suspended (TSS) 311 kg/d MxCalWkAvg 2 x Week Solids, Total Suspended (TSS) 45 mg/l MxCalWkAvg 2 x Week Solids, Total Suspended (TSS) Percent Removal 85 % MnCalMoAvg 2 x Week Specific Conductance Only umhos/cm CalMoMax 1 x Month Sulfate, Total (as SO4) Only mg/l CalMoMax 1 x Month Proposed permit effluent limits The effluent limits and monitoring requirements in the proposed draft permit are presented in Table 3 at the end of this section. This table lists water quality based effluent limits, technology based effluent limits, and state discharge restrictions. Technology based effluent limits (TBELs) The CBOD 5, CBOD 5 percent removal, TSS, TSS percent removal, and potential for Hydrogen (ph) removal limits that have been included in this permit are technology based limits developed for achieving secondary treatment standards. These limits are specified in 40 CFR and Minn. R and Minn. R Water quality based effluent limits (WQBEL) The total ammonia nitrogen and total phosphorus (TP) limits included in this permit are WQBELs. WQBELs are established to meet applicable water quality standards. Under 40 CFR (d)(1)(i), all dischargers who have the reasonable potential to cause or contribute to an exceedance of a water quality standard are required to have a WQBEL. Additional information on the TP limit can be found on pages of this fact sheet. 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. The total nitrogen limit included in this permit is a WQBEL. To ensure there is no chronic WET toxicity, the draft permit contains a ly limit of 18 mg/l total nitrogen limit. The limit is assigned to prevent WET toxicity issues from reoccurring. Additional information on the total nitrogen limit can be found on page 26 of this fact sheet under the Toxicity Reduction Plan section. State Restrictions (SDRs) The fecal coliform bacteria limit is a state discharge restrictions specified in Minn. R , subp. 1. Table 3: Surface Station Proposed Limits and ing Requirements

18 Permit Reissuance Page 18 of 30 Subject item Phase 1 Phase 1 Phase 2 Phase 1 Phase 2 Parameter Bicarbonates (HCO3) BOD, Carbonaceous 05 Day (20 Deg C) BOD, Carbonaceous 05 Day (20 Deg C) BOD, Carbonaceous 05 Day (20 Deg C) BOD, Carbonaceous 05 Day (20 Deg C) Percent Removal Calcium, Total (as Ca) Chloride, Total Chlorine, Total Residual Copper, Total (as Cu) Fecal Coliform, MPN or Membrane Filter 44.5C Fecal Coliform, MPN or Membrane Filter 44.5C Flow limitations Quantity / Loading avg Quantity / Loading max total Quantity / Loading units kilograms per day kilograms per day kilograms per day million gallons Conc. min. 85 minimum Conc. avg geometric mean 200 geometric mean Conc. max daily daily quarter ing requirements Conc. units Frequency percent micrograms organisms per 100 milliliter organisms per 100 milliliter million gallons per day twice per twice per 3 times per day quarter twice per 3 times per day Sample type Calculation Grab Grab Grab Grab Measurement, Continuous Effective period Apr-Nov Dec- Mar Mar, Jun, Sep, Dec Apr-Oct Apr-Oct

19 Permit Reissuance Page 19 of 30 Subject item Phase 1 Phase 2 Phase 1 Phase 1 Phase 1 Phase 2 Phase 2 Phase 2 Parameter Hardness, Calcium & Magnesium, Calculated (as CaCO3) Magnesium, Total (as Mg) Mercury, Dissolved (as Hg) Mercury, Total (as Hg) Nitrite Plus Nitrate, Total (as N) Nitrite Plus Nitrate, Total (as N) limitations Quantity / Loading avg. Nitrogen, 57.0 Ammonia, Total (as N) Nitrogen, Ammonia, Total (as N) Nitrogen, Ammonia, Total (as N) Nitrogen, Ammonia, Total (as N) Nitrogen, Ammonia, Total (as N) Nitrogen, Ammonia, Total (as N) Quantity / Loading max. Quantity / Loading units kilograms per day kilograms per day kilograms per day kilograms per day kilograms per day kilograms per day Conc. min. Conc. avg Conc. max. ing requirements Conc. units Frequency nanograms nanograms twice per Sample type Grab Grab Effective period May, Sep May, Sep Dec- Mar Apr- May Oct-Nov Dec- Mar Apr- May Oct-Nov

20 Permit Reissuance Page 20 of 30 Subject item Phase 1 Phase 2 Phase 1 Phase 2 Phase 1 Phase 2 Phase 2 Parameter Nitrogen, Ammonia, Total (as N) Nitrogen, Kjeldahl, Total Nitrogen, Kjeldahl, Total Nitrogen, Total (as N) Nitrogen, Total (as N) limitations Quantity / Loading avg. 7.0 Quantity / Loading max. Quantity / Loading units kilograms per day Conc. min. ph 6.0 minimum Phosphorus, Total (as P) Phosphorus, Total (as P) Phosphorus, Total (as P) Potassium, Total (as K) Sodium, Total (as Na) kilograms per day kilograms per day kilograms per day Conc. avg Conc. max. 9.0 ing requirements Conc. units Frequency standard units twice per twice per day Sample type Grab Effective period Jun-Sep Jun-Sep Oct- May

21 Permit Reissuance Page 21 of 30 Subject item Phase 1 Phase 2 WS 001 Influent Waste Stream Phase 1 WS 001 Influent Waste Stream Phase 2 WS 001 Influent Waste Stream WS 001 Influent Waste Stream Parameter Solids, Total Dissolved (TDS) Solids, Total Suspended (TSS) Solids, Total Suspended (TSS) Solids, Total Suspended (TSS) Percent Removal Solids, Total Suspended (TSS), grab (Mercury) Specific Conductance Sulfate, Total (as SO4) BOD, Carbonaceous 05 Day (20 Deg C) BOD, Carbonaceous 05 Day (20 Deg C) Nitrite Plus Nitrate, Total (as N) Nitrogen, Kjeldahl, Total limitations Quantity / Loading avg Quantity / Loading max Quantity / Loading units kilograms per day kilograms per day Conc. min. 85 minimum Conc. avg Conc. max ing requirements Conc. units Frequency percent micromhos per cm twice per 3 times per twice per 3 times per Sample type Calculation Grab Effective period May, Sep Measurement

22 Permit Reissuance Page 22 of 30 Subject item WS 001 Influent Waste Stream WS 001 Influent Waste Stream WS 001 Influent Waste Stream WS 001 Influent Waste Stream WS 001 Influent Waste Stream Phase 1 WS 001 Influent Waste Stream Phase 2 Parameter Nitrogen, Total (as N) ph Phosphorus, Total (as P) Precipitation Solids, Total Suspended (TSS) Solids, Total Suspended (TSS) limitations Quantity / Loading avg. Quantity / Loading max. total Quantity / Loading units inches Conc. min. minimum Conc. avg. Conc. max. ing requirements Conc. units Frequency standard units day day twice per 3 times per Sample type Grab Effective period Measurement Proposed Total Phosphorus Effluent Limit Phosphorus is a common constituent in many wastewater discharges and a pollutant that has the potential to negatively impact the quality of Minnesota s lakes, wetlands, rivers, and streams. Phosphorus promotes algae and aquatic plant growth often resulting in decreased water clarity and oxygen levels. In addition to creating general aesthetic problems, these conditions can also impact a water body s ability to support healthy fish and other aquatic species. Therefore, phosphorus discharges are being carefully evaluated throughout the state. The Permittee is required to meet a phosphorus limit as specified in the limits and monitoring section of this permit. Although the Permittee is not required to prepare a Phosphorus Management Plan, elimination or reduction of phosphorus at the source will decrease the influent load to the wastewater treatment facility and has the potential to improve treatment efficiency and reduce treatment costs. The MPCA strongly encourages the Permittee to identify and eliminate/reduce sources of phosphorus to, and optimize phosphorus management within, the wastewater treatment facility. All phosphorus samples must be analyzed by a certified laboratory and the data submitted to the MPCA. If your laboratory would like more information about becoming certified, please call the Environmental Laboratory Certification Unit at Samples must be collected in a clean bottle (preferably cleaned by a certified laboratory) that was not washed with phosphate detergent. Also, a sulfuric acid preservative must be added immediately after the sample is

23 Permit Reissuance Page 23 of 30 collected, and it must be stored at four degrees Celsius until analysis. If a contract laboratory is used, the bottle and preservative would typically be provided by the laboratory analyzing the sample. River Eutrophication Standards (RES) Federal law [40 CFR (d)] restricts mass increases of pollutants upstream of an impaired water and requires WQBEL to be established for pollutant parameters where it is found that a NPDES/SDS discharger has the reasonable potential to cause or contribute to an excursion above a state water quality standard. An effluent limits analysis was completed on the Windom WWTF to determine if the WWTF s discharge has reasonable potential to cause or contribute to an exceedance of a state water quality standard or contribute to any downstream impairment. As a result of the analysis, a total phosphorus effluent limit was established for the Windom WWTF to ensure protection of downstream waters and to comply with River Eutrophication Standards. A summary of the effluent limits analysis and the assigned total phosphorus limit is included below. For additional details regarding the effluent limits analysis, please see the Total phosphorus effluent limit review: Des Moines River Headwaters Watershed. A copy of the MPCA memorandum is available upon request. The Windom WWTF is one of numerous WWTFs located within the Des Moines River Headwaters Watershed. A watershed scale analysis was completed to determine if total phosphorus effluent limits were necessary for the WWTF s located within the watershed to protect for RES. This analysis determine that a 1.0 mg/l, June through September, total phosphorus limit assigned to the Windom WWTF was sufficient to meet RES within the Des Moines River system. Guidance for the analysis, determination of reasonable potential, and WQBEL setting process is defined in the Procedures for Implementing River Eutrophication Standards for NPDES Wastewater Permits in Minnesota (MPCA 2015), which can be found at: The complete Total phosphorus effluent limit review: Des Moines River Headwaters Watershed memorandum is available upon request from the MPCA. Proposed Five-Day Carbonaceous Biochemical Oxygen Demand (CBOD 5) Limit A higher CBOD 5 limit is recommended with the CBOD 5/Ammonia Nitrogen (NH 3-N) linkage option. This option is based on the concept that a fully nitrifying wastewater treatment facility treating domestic wastewater produces single digit effluent CBOD 5 concentrations most of the year. Facilities designed and operated to meet stringent (3 mg/l or less in summer and 5 mg/l or less in winter) effluent limits consistently produce low CBOD 5 concentrations. For a discharger to take advantage of the CBOD 5/NH 3-N linkage option, the facility must be designed for full biological nitrification of the entire waste stream. With this linkage option, a 15 mg/l CBOD 5 effluent limitation is recommended for the Windom WWTF. Reasonable potential analysis Background for Reasonable Potential Review The discharge is located on the West Fork of the Des Moines River. The WWTF has submitted one WET test and three priority pollutant scans since This Facility has been in a Toxicity Reduction Evaluation (TRE) for the majority of its permit cycle. The ADW design flow is used to calculate WQBEL under critical low flow stream conditions. The ADW is now 1.13 mgd. The ADW is going to increase to mgd. The low flow condition is defined by the once in ten year ly flow (7Q 10), which is determined to be 0.0 cfs (0.0 mgd). This Facility monitored for salty parameters, total copper, dissolved copper, mercury, priority pollutants, and is still currently performing a TRE. The analysis below is based on data submitted to date. Due to an increase in the Facility s flow, the State s antidegradation rule is also part of this review, described below. Requirements Associated with the Minnesota Antidegradation State Rule Because of the change in baseline flows for this permit, there will be a larger flow into the West Fork of the Des Moines River. For the pollutants such as nitrogen and phosphorus, because of the Facility upgrades, there will be a decrease in

24 Permit Reissuance Page 24 of 30 mass loading of these pollutants to the river. Because the Windom WWTF accepted the chloride linkage option, there will also be less mass loading of the salty parameter pollutants, which have been identified as having reasonable potential to cause or contribute to the exceedance of a surface water quality standard. Thus, there is no need to go through an antidegradation review for phosphorus, the nitrogen series, or for those salty parameters, which have been shown to have reasonable potential to cause or contribute to the exceedance of their water quality standard. On February 22, 2018, the Windom WWTF accepted the chloride linkage option to freeze mass limits at the Facility s current levels in lieu of an antidegradation review. Chemical Specific Reasonable Potential for Chemical Specific Pollutants [40 CFR (d)(1)] 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 (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 (PEL) 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 for that pollutant. The priority pollutant scan information of the effluent was evaluated using reasonable potential procedures. All but chloroform of the organic priority pollutants were below the level of detection. Total arsenic, total copper, total nickel, total selenium, and total zinc were also detected in the priority pollutant scans. Mercury Reasonable Potential Conclusions Total Mercury - ing results of the effluent include 26 data points at a calculated CV of 0.6. The default CV of 0.6 was used because a large percentage of the data set was below the reporting limit of 0.5 nanograms (ng/l). The PEQ is derived as an upper bound value from the highest value measured (0.899 ng/l), and the determined variability (CV = 0.6) and number of data points (26). 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 PEL 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. Therefore, a WQBEL is not needed.

25 Permit Reissuance Page 25 of 30 Copper Reasonable Potential Conclusions Total Copper - ing results of the effluent include 29 data points at a calculated CV of The PEQ is derived as an upper bound value from the highest value measured 28 microgram/l (µg/l), and the determined variability (CV = 0.24) and number of data points (29). Reasonable potential to cause or contribute to the excursion above a water quality standard has been indicated for total copper. The MPCA EAO Division, however, is not going to recommend WQBELs for copper. The Facility monitored for both total copper and dissolved copper. Several of the data indicated there was more dissolved copper than total copper in a given sample. It is not possible to have more dissolved copper in a sample than total copper. The EAO staff believe there was some sort of matrix interference in the analysis of this metal. The EAO staff has talked to the WWTF manager. There is a higher total copper concentration than what is normally found in a WWTF. There are two SIUs in Windom, which uses powder coated paint. The WWTF manager will investigate the source of copper in the upcoming permit cycle. The EAO staff recommend quarterly total copper sampling for the upcoming permit cycle. Salty Parameters Reasonable Potential Conclusions Salty Parameters There are five salty parameter water quality standards which have reasonable potential and need WQBELs. The EAO staff recommended the chloride linkage option, which the Facility has requested to use to ensure compliance with all salty parameters. The chloride linkage option and resulting Chloride Reduction Plan is further explained in the Compliance Schedule section of this fact sheet. Table 4 shows the inputs to the reasonable potential analysis for bicarbonates (as HCO 3), hardness (Mg plus Ca as CaCO 3), the class 2B chloride water quality standard, the class 3C chloride water quality standard, sulfate, total dissolved salts [measured as total dissolved solids (TDS)], specific conductivity, copper, lead, nickel, zinc, and mercury. In regards to the metals, the analysis is made with effluent data that is expressed as total metal. These pollutants were evaluated based on analytical measurements that made evident the need for a full determination. Where PEQs exceed PELs, a WQBEL is needed.

26 Permit Reissuance Page 26 of 30 Table 4: Reasonable Potential Analysis for Windom WWTF Parameter Bicarbonates as HCO3 (mg/l) Hardness (mg/l) Class 2 Cl (mg/l) Class 3 Cl (mg/l) Sulfate (mg/l) TDS (mg/l) Specific Conductance (umhos/cm) Hg (ng/l) As (ug/l) Cu (ug/l) Ni (ug/l) Se (ug/l) Zn (ug/l) chloroform (ug/l) Max Measured Value # data points PEQ Plant flow ADW (mgd) Rec. water flow, 7Q10 (mgd) Background concentration, West Fork of the Des Moines River (2B) Chronic standard (cs) ppm hard Maximum standard (ms) NA NA 860 NA NA NA NA ppm hard Final acute value (FAV) NA NA 1720 NA NA NA NA ppm hard Mass balance -cs Mass balance -ms Coefficient of variation Long term avg-cs Long term avg-ms Preliminary effl. limits: Daily max Monthly avg. (2 x ) Reasonable Potential PEQ > Daily max. TRUE TRUE TRUE TRUE FALSE TRUE TRUE FALSE FALSE TRUE FALSE FALSE FALSE FALSE PEQ > Monthly avg. TRUE TRUE TRUE TRUE FALSE TRUE TRUE FALSE FALSE TRUE FALSE FALSE FALSE FALSE PEQ > FAV NA NA FALSE NA NA NA NA FALSE FALSE FALSE FALSE FALSE FALSE FALSE Final Reasonable Potential Yes Yes Yes Yes No Yes Yes No No NO! No No No No

27 Permit Reissuance Page 27 of 30 Additional requirements Mercury Minimization Plan (MMP) The draft permit contains requirements for mercury monitoring and for submittal of a MMP or an updated MMP. These requirements were added in response to the EPA s approval of the Minnesota state-wide Mercury TMDL plan. Specific mercury monitoring requirements are found in the Surface Stations Chapter of the draft permit. Those requirements include sampling for TSS via a grab sample taken at the same time as the mercury grab samples are taken. Toxicity Reduction Evaluation (TRE) The Facility has been in a TRE since The April 2016 TRE report concluded if the concentration of Nitrate plus Nitrite is kept below 20 mg/l, the chronic WET tests will not exceed 1.0 Toxic Unit chronic (TUc). The EAO staff recommend the concentration for Nitrate plus Nitrite not exceed 18 mg/l (Total Nitrogen) in the effluent in regards to not exceeding chronic WET toxicity. To ensure there is no chronic WET toxicity, the draft permit contains a ly limit of 18 mg/l Total Nitrogen. This limit is assigned to prevent WET toxicity issues from reoccurring. The ly is based on sampling twice per. The engineering firm working on upgrading the WWTF has requested the TRE stay in place for one year after the initial operation of the denitrification equipment. This is to give time for the equipment to be properly adjusted. The MPCA agrees with this approach. After the one year of adjustment, the WWTF will perform two chronic WET tests. One of those chronic WET tests must be performed during the winter s. If the WWTF passes both chronic WET tests, the MPCA will send the City of Windom a letter removing them from the TRE process. The WWTF will then go back into normal chronic WET testing with a 1.0 TUc daily max limit. The 1.0 TUc daily max limit must be met at the end of pipe. As a condition of coming out of the TRE, the Facility will have to perform two chronic WET tests for the life of the permit. For each year, one of the chronic WET tests must be performed during the winter s. Whole Effluent Toxicity (WET) Testing Requirements The Permittee has a chronic WET limit of 1.0 TUc established in a previous permit cycle. The Windom WWTF has chronic WET testing because the ratio of the 7Q 10 low flow of the receiving water compared to the Facility s ADW design flow is less than or equal to 20:1 and has a limit because reasonable has been shown in a past permit cycle. This 1.0 TUc limit is a daily WQBEL to be met at the end of pipe (). The Facility is currently operating in a TRE as outlined above. Upon successful completion of the TRE, the Permittee is required to complete semi-annual chronic toxicity tests for the rest of this five-year permit cycle. Nitrogen ing Requirements Nitrogen is a pollutant that can negatively impact the quality of Minnesota s water resources, including water used for drinking. Studies have shown that nitrogen in lakes and streams has a toxic effect on aquatic life such as fish. Like phosphorus, nitrogen is a nutrient that promotes algae and aquatic plant growth often resulting in decreased water clarity and oxygen levels. In September 2014, the MPCA completed the final draft of the Statewide Nutrient Reduction Strategy ( which identifies goals and milestones for nitrogen reductions for both point and non-point nitrogen sources within Minnesota. To gain a better understanding of the current nitrogen concentrations and loadings received by and discharged from the Facility additional effluent nitrogen monitoring has been added to the permit. This monitoring has been added in accordance with Minn. Stat The draft permit includes influent and effluent monitoring/limits for Ammonia Nitrogen, Nitrite plus Nitrate-Nitrogen, Total Kjeldahl Nitrogen, and Total Nitrogen. Refer to Table 3 for specific proposed Limits and ing requirements. Additional information on the total nitrogen limit can be found on above under the Toxicity Reduction Plan (TRE) section.