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: Facility name: City of Saint Cloud 400 2nd Street South Saint Cloud, Minnesota Saint Cloud Wastewater Treatment Facility th Street South Saint Cloud, Minnesota Current permit expiration date: March 31, 2018 Public comment period begins: March 29, 2017 Public comment period ends: April 26, 2017 Receiving water: Permitting contact: Mississippi River - Class 1C, 2Bd, 3C, 4A, 4B, 5, 6 water Holly Kvittem 714 Lake Avenue, Suite 220 Detroit Lakes, MN holly.kvittem@state.mn.us

2 Table of Contents Page Purpose and participation... 3 Applicable statutes... 3 Purpose... 3 Public participation... 3 Facility description... 4 Background information... 4 Facility location... 4 Outfall location... 4 Map of permitted facility... 5 Components and treatment technology... 6 Current information... 6 Flow schematic... 7 Changes to facility or operation... 8 Significant industrial users (SIUs)... 8 Recent compliance history... 9 Recent monitoring history Receiving water(s) Use classification Impairments Existing permit effluent limits Technology based effluent limits (TBELs) Water quality based effluent limits (WQBELs) Proposed permit effluent limits Technology based effluent limits Water quality based limits Additional requirements Pollutant minimization plans (PMP) Nitrogen Compliance schedules Variances Total facility requirements (TFR) Antidegredation and anti-backsliding... 23

3 Permit Reissuance Modification Page 3 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: Holly Kvittem Minnesota Pollution Control Agency 714 Lake Avenue, Ste 220 Detroit Lakes, MN 56501

4 Permit Reissuance Modification Page 4 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 The Saint Cloud Wastewater Treatment Facility (Facility) is located in the SE ¼ of Section 7, Township 123 North, Range 27 West, City of Saint Cloud, Stearns County, Minnesota (latitude: , longitude: ). The address for the Facility is th Street South, Saint Cloud, Minnesota The Facility is approximately 1 mile southeast of the city of Saint Cloud. Outfall location The outfall (SD004) for the Facility is located in the SW ¼ of Section 8, Township 123 North, Range 27 West, City of Saint Cloud, Stearns County, Minnesota. The outfall is approximately ½ - ¾ of a mile east-northeast of the Facility and has a continuous discharge to the Mississippi River. Latitude and longitude of the outfall SD004 is and , respectively.

5 Permit Reissuance Modification Page 5 of 19 Map of permitted facility

6 Permit Reissuance Modification Page 6 of 19 Components and treatment technology Current information The existing Facility is a Class A Facility and consists of a pump station with a mechanical bar screen, 30-inch and 42-inch force mains, Parshall flume, fine mechanical bar screen, manual bar screen, two vortex grit removal systems, four primary clarifiers, four biological nutrient removal (BNR) trains, ferric chloride feed system, four secondary clarifiers and ultraviolet disinfection. The existing solids processing system consist of two gravity belt thickeners, three anaerobic digesters, a storage digester, and biosolids storage. Biosolids are land applied at approved sites. The Facility has a recycled effluent water system for on-site use. The system has four recycled effluent pumps, three manifold strainers and a sodium hypochlorite feed system. The Facility has a continuous discharge (SD004) to the Mississippi River (Class 1C, 2Bd, 3B, 3C, 4A, 4B, 5, 6, Water), an Outstanding Resource Value Water (ORVW), and is designed to treat an average wet weather flow of 17.9 million gallons per day (mgd), an average dry weather flow of 17.6 mgd, a peak hourly wet weather flow of mgd, a five-day carbonaceous biochemical oxygen demand (CBOD 5 ) concentration of 239 milligrams per Liter (mg/l) and a total suspended solids (TSS) concentration of 307 mg/l when using the average wet weather design flow of 17.9 mgd. The Facility is capable of full nitrification and biological nutrient removal (BNR). When the Facility is operating in the Bio- P mode, the total capacity of all four BNR trains is 17.9 mgd average wet weather flow and the capacity per train is mgd. When the Facility is operating in the BNR mode, the total capacity of all four trains is 15.0 mgd average wet weather flow and the capacity per train is 3.75 mgd.

7 Permit Reissuance Modification Page 7 of 19 Flow schematic

8 Permit Reissuance Modification Page 8 of 19 Changes to facility or operation The Facility plans to update their current biosolids practices for the treatment of Class A biosolids along with other changes. Proposed changes include adding pad-mounted membrane biogas storage; new biosolids heat exchangers; ventilation improvements in the digester complex and boiler/electrical room; Centrifuge dewatering; incorporating use of Lystek process; biosolids struvite precipitation; and sidestream ammonia equalization. The draft permit includes a voluntary construction schedule (sections ) for the permittee to complete the proposed updates to their biosolids treatment process. Significant industrial users (SIUs) The Permittee has been delegated the authority to operate as the control authority under the General Pretreatment Regulations. The Permittee s pretreatment program was originally approved on November 9, The Facility has 23 SIUs, all of which have a control mechanism associated with the Facility. Of the 23 SIUs, 7 of them are subject to Categorical Standards. Name All Professional Powder Coatings Ameripride Linen and Apparel Branding Iron Holdings Total Average Flow (gpd) Flow from process wastewater (gpd) Flow from nonprocess wastewater (gpd) Principal Products or raw materials used Considered a SIU (Y/N) Is there currently a control mechanism and/or local limits (Y/N) Painted metal parts Y Y Y 4,229 61,333 3,717 Clean garments, rugs, rags, etc. Y Y N 57,994 57, Hamburger Patties Y Y N Custom Eyes 6,847 5,333 1,514 Eyeglasses Y Y N DBL 12,379 8,858 3,521 Eyeglasses Y Y N Laboratories DeZurik 32,100 24,543 7,557 Valves Y Y Y East Side Oil Recycled Oil Y Y Y Company Electrolux 68,499 11,282 57,217 Freezers, Y Y Y Home Products Refrigerators G&K services 93,325 91,721 1,604 Clean garments, Y Y N rugs, rags, etc National 8,403 6,999 1,404 Eyeglass lens Y Y N Vision New Flyer of 20,042 18,042 2,000 Buses Y Y N America North Central Ophthalmic 5,026 3,089 1,937 Eyeglasses Y Y N Northern Metal Products Park Industries 4415/ 4,315 Precision Optics (2) 6,932 6, Shelving units, display shelves 150/50 4,265 Stone cutting/ polishing machinery Y Y Y Y Y Y 16,051 15, Eyeglasses Y Y N Is the IU subject to Categorical Standards? (N/Y)

9 Permit Reissuance Modification Page 9 of 19 Rapid Plating 3, ,467 Coated metal Parts Y Y Y St. Cloud 220, ,939 52,080 N/A Y Y N Hospital St. Cloud Printing plates Y Y Y Engraving Talon 4,122 1,200 2,922 Gas delivery Y Y Y Innovations components for semiconductor industry VA Health N/A N/A N/A N/A Y Y N Care System Viking Cocoa- 124,414 93,124 31,290 Coke Products Y Y N Cola X-Cel Optical Company 1,883 1, Eyeglass lens Y Y N Recent compliance history A Compliance Evaluation Inspection (CEI) occurred on August 20, 2015 by Molly Baumann, Justin Barrick, and Breeanna Bateman of the MPCA. The CEI consisted of a visual inspection of the facility and a discussion with Patrick Shea, Public Services Director; Tracy Hodel, Assistant Public Services Director; Erin McMahon, Laboratory Technician; and Chris Plautz, Wastewater Operator. There was also a review of the monthly discharge monitoring reports (DMRs) for the time period of July 2012 to July Based on the results of the inspection, there were no violations of the terms and conditions set forth in the National Pollutant Discharge Elimination System (NPDES)/State Disposal System (SDS) permit. A biosolids CEI occurred on March 31, 2016 by Justin Barrick and Sherry Bock of the MPCA as a complaint investigation. The CEI included a review of biosolids records dating back to the 1980s (if pertinent to the complaint investigation), an inspection of the biosolids land application site during product injection and a discussion with Tracy Hodel (Assistant Utilities Director), Emma Larson (Environmental Compliance Specialist), and Shane Lund (Utilities Water Quality Coordinator). Biosolids techniques were reviewed at this time. Based on the results of the CEI, no violations of terms and conditions set forth in the NPDES/SDS permit were noted. A Pretreatment Compliance Inspection (PCI) occurred on May 26, 2016 by Jaramie Logelin of the MPCA. The PCI consisted of a review of the significant industrial user (SIU) files maintained by the facility, a SIU inspection of Branding Iron Sauk Rapids (Huisken Meats), and discussions with pretreatment contacts, Emma Larson and Shane Lund. Neither the wastewater treatment facility nor its operations were inspected. Based on the results of the PCI, no violations of the terms and conditions of NPDES/SDS permit were noted.

10 Permit Reissuance Modification Page 10 of 19 Recent monitoring history Surface Discharge Station SD004 - Discharge Monitoring Report Summary from January 2016 through December 2016 Parameter Desc Limit Units Limit Type Jan- 16 Feb-16 Mar- 16 Apr- 16 May- 16 Jun-16 Jul-16 Aug-16 Sep-16 Oct- 16 Nov- 16 Dec- 16 CBOD5 25 mg/l CalMoAvg CBOD5 1,229 kg/d CalMoAvg CBOD5 40 mg/l MxCalWkAv g CBOD5 1,966 kg/d MxCalWkAv g CBOD5 % Removal 85 % MnCalMoAv g Fecal Coliform 200 #/ 100ml CalMoGeoM n Flow mgd CalMoAvg Flow mgd CalMoMax Flow Mgal CalMoTot Mercury, Dissolved (as Hg) ng/l CalMoMax Mercury, Total (as Hg) ng/l CalMoMax Nitrite Plus Nitrate, Total (as N) mg/l CalMoAvg Nitrogen, Ammonia, Total (as N) mg/l CalMoAvg Nitrogen, Kjeldahl, Total mg/l CalMoAvg Oxygen, Dissolved mg/l CalMoMin ph 9 SU CalMoMax ph 6 SU CalMoMin Phosphorus, Total (as P) 1 mg/l 12MoMov Ave Phosphorus, Total (as P) 19,783 kg/yr 12MoTotal 2,695 2, ,082 1,995 1,921 1, ,873 1,785 1, ,352 1,458 1,606 Phosphorus, Total (as P) mg/l CalMoAvg

11 Permit Reissuance Modification Page 11 of 19 Phosphorus, Total (as P) kg/mo CalMoTot Solids, Total Dissolved (TDS) mg/l CalMoAvg Solids, Total Suspended (TSS) 30 mg/l CalMoAvg Solids, Total Suspended (TSS) 1,474 kg/d CalMoAvg Solids, Total Suspended (TSS) 45 mg/l MxCalWkAv g Solids, Total Suspended (TSS) 2,211 kg/d Solids, Total Suspended (TSS) % Removal 85 % MxCalWkAv g MnCalMoAv g Solids, Total Suspended (TSS), grab (Mercury) mg/l CalMoMax

12 Permit Reissuance Modification Page 12 of 19 Receiving water(s) Use classification The facility has a continuous discharge via surface discharge station SD004 to the Mississippi River. This water is classified as a Class 1C, 2Bd, 3B, 3C, 4A, 4B, 5, 6 water. Class 1 waters, domestic consumption. Domestic consumption includes all waters of the state that are or may be used as a source of supply for drinking, culinary or food processing use, or other domestic purposes and for which quality control is or may be necessary to protect the public health, safety, or welfare. 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. There are no endangered or threatened species living in the receiving water. More information on the classification of waters can be found in Minn. R Impairments This water is listed on the 303(d) list as impaired for Mercury. The following tables list the current impairments for the receiving water. AUID or Lake Waterbody Assessment Category & Pollutants or Impairment ID# SubCategory Mississippi 5B Fish-Mercury, Mercury River Lake Pepin 5B Nutrient/eutrophication biological indicators

13 Permit Reissuance Modification Page 13 of 19 Impacts of the Approved TMDLs on the Facility s Limits and Monitoring Requirements Mercury - The Statewide Mercury TMDL is applicable to all downstream reaches of the Mississippi River for mercury in fish tissue and mercury in water column impairments. Mercury monitoring requirements within this draft permit are in accordance with the Mercury Permitting Strategy. Fecal Coliform Bacteria Four downstream reaches of the Mississippi River listed as impaired for fecal coliform bacteria are being addressed by the Upper Mississippi River Bacteria TMDL project. Although the reaches are included in the TMDL, a WLA was not assigned to this facility. Total Suspended Solids (TSS) Five downstream reaches of the Mississippi River are listed as impaired for turbidity. A 32 mg/l TSS site specific standard (TSS is a surrogate for turbidity) has been developed for Pools 2 & 3 from Lock & Dam #1 to Lake Pepin. The South Metro Mississippi River TSS TMDL, which addresses these impaired reaches, has been on public notice and is currently in the process of addressing extensive public comments. The TMDL contains the following draft wasteload allocations for the Facility which are equivalent to the draft permit s TSS limit: - TSS WLA = 538,010 kg/year and 1, kg/day Nutrient/Eutrophication In 2002, Lake Pepin was listed as impaired due to excess nutrients. Phosphorus is the primary nutrient responsible for excess algal growth in Lake Pepin. The Facility has reasonable potential (RP) to cause or contribute to downstream impaired waters; therefore, a Water Quality Based Effluent Limit (WQBEL) for total phosphorus is required. The draft permit includes a TP WQBEL of 19,783 kg/year which was derived from the draft Lake Pepin TMDL wasteload allocation. The eutrophication impairment in the Mississippi River is new to the draft 2016 Impaired Waters List. The impairment is found in the downstream waters from the St. Croix River to the Chippewa River (WI). While a TMDL has not been developed to address this impairment, past and current reasonable potential analysis and effluent limit reviews have been completed to determine the extent to which the St. Cloud WWTF contributes to nutrient impairments. Detailed explanations of the St. Cloud WWTF s reasonable potential analyses are discussed under the Proposed Effluent Limits Review Section of this document. Additional Impairments - There are a number of Polychlorinated Biphenyls Fish (PCBF), Perfluorooctane Sulfonate in Fish (PFOS-F) and Perfluorooctane Sulfonate in the water column (PFOS-W) impairments; TMDLs are not underway for PCBF or PFOS impairments at this time. Existing permit effluent limits Technology based effluent limits (TBELs) The ph limits 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 five-day carbonaceous biochemical oxygen demand (CBOD 5), CBOD 5 percent removal, total suspended solids (TSS), TSS percent removal, 12-Month Moving Total total phosphorus limits are water quality based limits. State Discharge Restrictions (SDR) The fecal coliform and 12-Month Moving Average total phosphorus limits are state discharge restrictions. These limits are specified in Minn. R , subp. 1.

14 Permit Reissuance Modification Page 14 of 19 Surface Discharge Station SD004 - Existing Limit and Monitoring Requirements Parameter Desc Limit Units Limit Type Effective Period Frequency CBOD mg/l CalMoAvg Jan-Dec 3 x week CBOD kg/d CalMoAvg Jan-Dec 3 x week CBOD mg/l MxCalWkAvg Jan-Dec 3 x week CBOD kg/d MxCalWkAvg Jan-Dec 3 x week CBOD5 % Removal 85 % MnCalMoAvg Jan-Dec 3 x week Fecal Coliform 200 #/100ml CalMoGeoMn Apr-Oct 3 x week Flow Monitor Only mgd CalMoAvg Jan-Dec 1 x day Flow Monitor Only mgd CalMoMax Jan-Dec 1 x day Flow Monitor Only Mgal CalMoTot Jan-Dec 1 x day Mercury, Dissolved (as Hg) Monitor Only ng/l CalMoMax May, Sep 1 x month Mercury, Total (as Hg) Monitor Only ng/l CalMoMax May, Sep 1 x month Nitrite Plus Nitrate, Total (as N) Monitor Only mg/l CalMoAvg Apr, Sep 1 x month Nitrogen, Ammonia, Total (as N) Monitor Only mg/l CalMoAvg Jan-Dec 1 x month Nitrogen, Kjeldahl, Total Monitor Only mg/l CalMoAvg Apr, Sep 1 x month Oxygen, Dissolved Monitor Only mg/l CalMoMin Jan-Dec 1 x day ph 9.0 SU CalMoMax Jan-Dec 1 x day ph 6.0 SU CalMoMin Jan-Dec 1 x day Phosphorus, Total (as P) 1.0 mg/l 12MoMovAve Jan-Dec 1 x week Phosphorus, Total (as P) 19,783 kg/yr 12MoTotal Jan-Dec 1 x week Phosphorus, Total (as P) Monitor Only mg/l CalMoAvg Jan-Dec 1 x week Phosphorus, Total (as P) Monitor Only kg/mo CalMoTot Jan-Dec 1 x week Solids, Total Dissolved (TDS) Monitor Only mg/l CalMoAvg Apr, Sep 1 x month Solids, Total Suspended (TSS) 30.0 mg/l CalMoAvg Jan-Dec 3 x week Solids, Total Suspended (TSS) 1,474.0 kg/d CalMoAvg Jan-Dec 3 x week Solids, Total Suspended (TSS) 45.0 mg/l MxCalWkAvg Jan-Dec 3 x week Solids, Total Suspended (TSS) 2,211.0 kg/d MxCalWkAvg Jan-Dec 3 x week Solids, Total Suspended (TSS) % Removal 85 % MnCalMoAvg Jan-Dec 3 x week Solids, Total Suspended (TSS), grab (Mercury) Monitor Only mg/l CalMoMax May, Sep 1 x month Proposed permit effluent limits Technology based effluent limits The ph limits are technology based limits developed for achieving secondary treatment standards. These limits are specified in 40 CFR and Minn. R and Minn. R State Discharge Restrictions (SDR) The fecal coliform and 12-Month Moving Average total phosphorus limits are state discharge restrictions. These limits are specified in Minn. R , subp. 1.

15 Permit Reissuance Modification Page 15 of 19 Water quality based limits The five-day carbonaceous biochemical oxygen demand (CBOD 5), CBOD 5 percent removal, total suspended solids (TSS), TSS percent removal, 12-Month Moving Total total phosphorus limits are WQBELs. WQBELs are established to meet applicable water quality standards. Under 40 CFR (d)(1)(i), all dischargers who have reasonable potential to cause or contribute to an exceedance of a water quality standard are required to have a WQBEL. Additional information regarding the development of the WQBELs is included below. Background for Reasonable Potential Review The Facility discharge point on the Mississippi River is at the head of an Outstanding Resources Value Water (ORVW). The discharger has submitted three whole effluent toxicity (WET) tests and two priority pollutant scans since The low flow condition is defined by the once in 10 year weekly average flow (7Q 10), which is determined to be 1278 cubic feet per second (cfs). The dilution ratio is 108:1. Reasonable Potential for Chemical Specific Pollutants (40CFR122.44(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, 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 priority pollutants were below the level of detection or at low levels. Since these pollutants were at low levels, reasonable potential to cause or contribute to a water quality standards excursion is not indicated. At the dilution ratio of 108:1 no pollutant would indicate reasonable potential to cause or contribute to an excursion of a water quality standard. Therefore, no limit is needed in any case. Mercury- Monitoring results of the effluent include 28 data points with all values below the water quality standard of 6.9 ng/l. The preliminary effluent limit (PEL) calculation assumes that the background mercury concentration is at the water quality standard (6.9 ng/l) when the listed stream impairment is for fish consumption advice, and no local river water column analytical data exist. To assure that the discharge does not cause or contribute to a water quality standards excursion for mercury impaired waters, the numeric water quality standard (6.9) is applied at the point of discharge for the mass balance equation for the subsequent preliminary effluent limit calculations. Where PEQ exceeds the PEL, there is reasonable potential to cause or contribute to a water quality standards excursion. Since PEQ does not exceed the PEL in this case, reasonable potential to cause or contribute to an excursion above water quality standards is not indicated. A water quality-based effluent limit (WQBEL) is not needed. There was a high value for mercury (12.8 ng/l) in March The facility submitted a memo appropriately demonstrating why that sample was likely contaminated and should be excluded from the reasonable potential analysis. Reasonable Potential for acute Whole Effluent Toxicity (WET) The existing permit for the Facility requires the Permitee to complete annual acute WET tests because the ratio of the 7Q 10 low flow of the receiving water compared to the Facility s ADW flow is greater than 20:1. Of the WET tests performed, no WET test showed any toxicity (TUa <1.0) for all species considered, therefore, no effluent limitations for WET testing are required. The draft permit again includes annual acute WET monitoring for the Facility with a Toxic Unit acute (TUa) monitoring threshold value, which is not a WET limit. If the permit exceeds 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

16 Permit Reissuance Modification Page 16 of TUa is exceeded for any one WET test, the Permittee is required to perform two WET retests to determine if a Toxicity Reduction Evaluation (TRE) is needed. Total Phosphorus (TP) WQBEL The MPCA completed an evaluation to determine the total phosphorous effluent limits that are required for the St. Cloud WWTF s discharge to ensure protection of all downstream waters. River Eutrophication Standards (RES) The MPCA utilizes a watershed based approach to set total phosphorus effluent limits. Receiving waters and downstream waters are evaluated to determine the assimilative capacity and pollutant load reductions necessary to meet standards. Then, wastewater discharges are analyzed to determine whether facilities have the reasonable potential (RP) to cause or contribute to an eutrophication impairment. If RP is found, a gross wasteload allocation (WLA) is derived from the water of interest and divided into individual WLAs for all upstream dischargers. The two main approaches for calculating RES limits are a water quality model or a mass balance based equation. Water quality models are the preferred method, but in this case, a model was not available and this review was completed by utilizing a mass balance based approach. The St. Cloud WWTF is located within the Mississippi River St. Cloud Watershed (Upper Subwatershed). All of the NPDES/SDS Permitted facilities that were included in the RES watershed review for the Mississippi River St. Cloud Watershed (Upper Subwatershed) are listed in Table 1 below. The Mississippi River St. Cloud Watershed (Upper Subwatershed), is a Class 2 Bd water within the Central River Nutrient Region which has RES standards (Minn. R ) of: 100ug/L Total Phosphorous 18 ug/l chlorophyll-a (Chl-a) 3.5 mg/l DO flux 2.0 mg/l BOD 5 There are two river reaches within the Mississippi River St. Cloud Watershed (Upper Subwatershed), with sufficient water quality data to allow for evaluation of RES attainment. Both reaches are sections of the Mississippi River, and 729 (Figure 1). Water quality data available for these reaches indicate RES criteria are being met (Table 2).

17 Permit Reissuance Modification Page 17 of 19 Figure 1. Mississippi River - St. Cloud Watershed NPDES facilities. Longest highlighted blue reach is Mississippi River. Table 2. St. Cloud Watershed summer (June September) average TP, Chl-a, and BOD5 concentrations in the Mississippi River, and applicable Central River Nutrient Region RES criteria. Total phosphorus, Chl-a, and BOD5 are meeting the applicable criteria. DO flux data were not available. Since neither the cause nor response criteria are exceeded, the focus is on protecting for the cause criterion, and a protection analysis was completed to determine if additional limits need to be assigned to the St. Cloud WWTF s discharge to ensure RES protection. To complete the protection analysis the MPCA completed the following steps: 1) To better understand the impacts on receiving waters from point sources, individual load duration curves were developed for river reaches and Point sources can have a disproportionate impact on receiving waters during summer (June September) low flow conditions. The 80 th percent flow exceedance

18 Permit Reissuance Modification Page 18 of 19 (when, on average, 80% of the flow exceeds the respective flow value) has been selected as the target flow to represent low flow conditions (MPCA, 2015). The load duration curves representing historical water quality from indicated that water quality meets RES during the 80 th percent flow exceedance condition for these two river reaches (see figures 4 9 of the 1/4/2016 Upper Subwatershed of the Mississippi River St. Cloud Watershed Memo). 2) When the receiving water meets the TP RES criterion, there is real-world data demonstrating that the current performance of WWTFs in the watershed are sufficient to protect the receiving water. The existing data does not represent the potential impact of facilities at 70% of AWWDF (best estimate of facility operation at design capacity during critical lower flow conditions in the river). To evaluate whether increased flows from the WWTFs would drive the TP concentration above the RES TP criterion, TP protection potential analyses were completed for the Mississippi River. Existing monitoring data for Chl-a indicate that algal response is limited in the Mississippi River. Given the large size of the Mississippi River and relatively clear condition of the water, it is reasonable to assume that concentrations above the mg/l TP criterion may lead to increased algal production in the river. The following equation was used to calculate the protection analyses of three river locations (A C, Figure 1) with WWTFs at current permitted discharge conditions. CCCC = QQQQQQQQ + QQQQQQQQ QQQQ Cr = downstream TP concentration of river at critical flow (80 th percent flow exceedance) Qr = downstream river flow (80 th percent flow exceedance) Qs = flow of river without WWTFs Cs = concentration of river without WWTFs Qe = design flow of WWTFs Ce = mass based concentration limit using either Lake Pepin categorical limits or facility-specific concentration limit A number of different river analyses were completed along the Mississippi River to take into account different scenarios to ensure potential limits were taken into account. One of those scenarios is the potential for the Albertville WWTF to change their discharge location in the future. Below are three river locations that were analyzed; river Locations A and B look at cumulative impacts on the river with River Location B being specific to Albertville WWTFs potential relocation of their discharge point whereas River Location C looks at the impacts from only the facilities directly discharging to that specific reach ( ). River Location A Mississippi River ( ) (looks at cumulative impacts on the river) Qr = 1,445 mgd; based on permitted flow values and using Qr = Qs + Qe Qs = 1,432 mgd; calculated using average daily flow from USGS gage at the outlet of the watershed during June September at 80 th percent flow exceedance and subtracting Appert s and St. Cloud WWTF s average daily flow during June September, Cs = 0.06 mg/l; average TP concentration of the Mississippi River without contributions from WWTFs under low flow conditions Qe = 13 mgd; 70% of permitted design flow Ce = 0.8 mg/l; mass based concentration limit using either Lake Pepin categorical limits or facility-specific concentration limit Cr = mg/l less than RES TP criterion

19 Permit Reissuance Modification Page 19 of 19 River Location B (specific to the Albertville WWTF s potential discharge relocation) Two scenarios were ran to review the Albertville WWTF discharge relocation considerations, and were not included in this fact sheet. For additional information regarding River Location B and the Albertville WWTF analysis, see the 1/4/2016 Upper Subwatershed of the Mississippi River St. Cloud Watershed Memo. Both scenarios ran were found to be below the RES TP criterion (0.051 ug/l and ug/l TP). River Location C Mississippi River ( ) current conditions (looks at the impacts of facilities only discharging to this reach) Qr = 1,563 mgd; based on permitted flow values and using Qr = Qs + Qe Qs = 1,561 mgd; calculated using average daily flow from USGS gage at the outlet of the watershed during June September at 80 th percent flow exceedance and subtracting The Facilities average daily flow during June September, Cs = 0.06 mg/l; average TP concentration of the Mississippi River without contributions from WWTFs under low flow conditions Qe = 1.8 mgd; 70% of permitted design flow Ce = 0.8 mg/l; mass based concentration limit using either Lake Pepin categorical limits or facility-specific concentration limit Cr = mg/l less than RES TP criterion Facilities are considered to have a reasonable potential to cause or contribute to a downstream impairment if, while operating at capacity, they: 1) discharge at TP concentrations higher than the applicable eutrophication standard, and 2) the calculated TP concentration of the water of interest at the 80% flow value exceeds RES. The calculated concentration (Cr) for the two river reaches in the Mississippi River - St. Cloud Watershed demonstrates that the discharge from the St. Cloud WWTF is not anticipated to cause or contribute to violations of the TP criterion, and therefore satisfy the protection potential analysis (locations A and C, Figure 1). Because Cr meets RES criteria in both scenarios, it was determined there is no RP for the St. Cloud WWTF s discharge to cause or contribute to a nutrient impairment in the Mississippi River St. Cloud Watershed. As a result, a RES based TP limit was not assigned to the St. Cloud WWTF. Lake Pepin Effluent from the St. Cloud WWTF is discharged upstream of Lake Pepin, a riverine lake 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. The TMDL study for Lake Pepin is currently delayed, but 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 RP to cause or contribute to downstream impaired waters are required to have a WQBEL. When determining RP, the Code of Federal Regulations also requires the use of procedures which account for existing controls on point and nonpoint sources of pollution. Permitees 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 (i.e mg/l), and 3) there is no geographical barrier capable of trapping a significant mass of nutrients between the outfall and the impairment during most streamflow conditions. For all reasons listed above, the St. Cloud WWTF was found to have RP for TP upstream of Lake Pepin; and therefore is required to have a WQBEL.

20 Permit Reissuance Modification Page 20 of 19 As a result, the St. Cloud WWTF is required to maintain the previously assigned TP WQBEL of 19,783 kg/year that was derived from the draft Lake Pepin TMDL WLA. 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. A categorical approach was used to develop individual WLAs for the draft Lake Pepin TMDL. The St. Cloud WWTF fits into a Municipal Major (MM) category defined by municipal facilities with average wet weather design flows (AWWDFs) between 1 and 20 million gallons per day (mgd). Individual MM WLAs are calculated as follows: General Formula: MM WLA = (AWWDF x 0.8 mg/l TP x L/gal x 365 days/yr) Saint Cloud WWTF WLA: 19,783 kg/yr TP = (17.9 mgd x 0.8 mg/l x L/gal x 365 days/yr) Additionally, the facility is to maintain the previously assigned SDR limit of 1.0 mg/l as a January-December 12-Month Moving Average limit. Summary of TP WQBEL review and limit assignments This Mississippi River St. Cloud Watershed (Upper Subwatershed) analysis demonstrates that the St. Cloud WWTF doed not have RP to cause or contribute to a river eutrophication impairment in the Upper Subwatershed region of the Mississippi River St. Cloud Watershed, under permitted effluent conditions. As such, existing limits in the permit are sufficient for the immediate receiving waters (19,783 kg/yr and 1.0 mg/l). Downstream of the St. Cloud Watershed, the St. Cloud WWTF has RP to cause or contribute to the excess nutrient impairment in Lake Pepin, and therefore, is required to have a WQBEL of 19, 782 kg/yr. Detailed information regarding the TP limit evaulation can be found in the January 4, 2016 MPCA memorandum titled, Total Phosphorus effluent limit review: Mississippi River St. Cloud Watershed.

21 Permit Reissuance Modification Page 21 of 19 Proposed Limits and Monitoring Requirements for Surface Discharge Station SD004 Parameter Discharge Limitations Monitoring Requirements Limit and Units Frequency Sample Type Effective Period BOD, Carbonaceous 05 Day (20 Deg 1229 calendar month 1966 maximum calendar week kilograms per day 3 x week 24-Hour Flow Composite Jan-Dec C) average average BOD, Carbonaceous 05 Day (20 Deg C) 25 calendar month average 40 maximum calendar week average milligrams per liter 3 x week 24-Hour Flow Composite Jan-Dec BOD, Carbonaceous 05 Day (20 Deg 85 minimum calendar month average percent 3 x week Calculation Jan-Dec C) % Removal Fecal Coliform, MPN or Membrane 200 calendar month geometric mean organisms per x week Grab Apr-Oct Filter 44.5C milliliter Flow Monitor only. calendar month total million gallons 1 x day Measurement, Continuous Jan-Dec Flow Monitor only. calendar month average Monitor only. calendar month maximum million gallons per day 1 x day Measurement, Continuous Jan-Dec Mercury, Dissolved (as Hg) Monitor only. calendar month maximum nanograms per liter 1 x month Grab May, Sep Mercury, Total (as Hg) Monitor only. calendar month maximum nanograms per liter 1 x month Grab May, Sep Nitrite Plus Nitrate (N) Monitor only. calendar month average milligrams per liter 2 x month 24-Hour Flow Composite Jan-Dec Nitrogen, Ammonia (N) Monitor only. calendar month average Milligrams per liter 1 x month 24-Hour Flow Composite Jan-Dec Nitrogen, Kjeldahl, Total Monitor only. calendar month average milligrams per liter 2 x month 24-Hour Flow Composite Jan-Dec Nitrogen, Total (N) Monitor only. calendar month average milligrams per liter 2 x month 24-Hour Flow Composite Jan-Dec Oxygen, Dissolved Monitor only. calendar month minimum milligrams per liter 1 x day Grab Jan-Dec ph 6.0 calendar month minimum 9.0 calendar month maximum standard units 1 x day Grab Jan-Dec Phosphorus, Total (P) Monitor only. calendar month average kilograms per day 1 x week 24-Hour Flow Composite Jan-Dec Phosphorus, Total (P) Monitor only. calendar month average milligrams per liter 1 x week 24-Hour Flow Composite Jan-Dec Phosphorus, Total (P) month moving total kilograms per year 1 x month Calculation Jan-Dec Phosphorus, Total (P) month moving average milligrams per liter 1 x month Calculation Jan-Dec Solids, Total Dissolved (TDS) Monitor only. calendar month average milligrams per liter 1 x month 24-Hour Flow Composite Jan-Dec Solids, Total Suspended (TSS) 1474 calendar month 2211 maximum calendar week kilograms per day 3 x week 24-Hour Flow Composite Jan-Dec average average Solids, Total Suspended (TSS) 30 calendar month average 45 maximum calendar week average milligrams per liter 3 x week 24-Hour Flow Composite Jan-Dec Solids, Total Suspended (TSS) % 85 minimum calendar month average percent 3 x week Calculation Jan-Dec Removal Solids, Total Suspended (TSS), grab (Mercury) Monitor only. calendar month maximum milligrams per liter 1 x month Grab May, Sep

22 Permit Reissuance Modification Page 22 of 19 Additional requirements Pollutant minimization plans (PMP) 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 U.S. Environmental Protection Agency s approval of the Minnesota statewide Mercury TMDL plan. Specific mercury monitoring requirements are found in the Surface Discharge Stations Chapter of the proposed permit. Those requirements include sampling for total suspended solids via a grab sample taken at the same time as the mercury grab samples are taken. Nitrogen 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 Minnesota Statues Chapter The draft Permit includes influent and effluent monitoring for Ammonia Nitrogen, Nitrite plus Nitrate-Nitrogen, Total Kjeldahl Nitrogen, Total Nitrogen and Total Dissolved Solids at a frequency of twice per month for the five-year term of the Permit. There is no nitrogen limit in the Permit. This additional monitoring will provide the data necessary to develop a better understanding of the total nitrogen concentrations and loadings that is currently being received and discharged from municipal and industrial wastewater treatment plants. Once a more extensive total nitrogen data set is established nitrogen reduction work can begin to achieve the necessary reductions to meet the goal of a 20% reduction in total nitrogen loads from point source dischargers by The changes and/or increases in total nitrogen monitoring in wastewater Permits as a result of the Statewide Nutrient Reduction Strategy is outlined in the Minnesota NPDES Wastewater Permit Nitrogen Monitoring Implementation Plan document located on the MPCA wastewater Permits webpage at: Compliance schedules There are no compliance schedules in the draft permit Construction schedules The Facility plans to update their current biosolids practices for the treatment of Class A biosolids along with other changes. Proposed changes include adding pad-mounted membrane biogas storage; secondary digester cover rehabilitation; new biosolids heat exchangers; ventilation improvements in the digester complex and boiler/electrical room; Centrifuge dewatering; incorporating use of Lystek process; biosolids struvite precipitation; and sidestream ammonia equalization. Further information regarding the construction schedule can be found in sections of the draft permit document. Variances There are no variances in the draft permit.

23 Permit Reissuance Modification Page 23 of 19 Industrial Stormwater Permit Coverage within the NPDES Permit On April 5, 2015, the Industrial Stormwater General Permit (MNR050000) was reissued. 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 addresses 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 treatment facilities, in lieu of obtaining coverage under both the General Permit and the individual NPDES permit, the MPCA has created the necessary industrial stormwater (ISW) boilerplate language and limits and monitoring so that coverage under the NPDES permit alone will cover both permits. Previously, the St. Cloud WWTF was covered under the ISW Permit, MNR053D3J but elected to combine their ISW permit coverage with their NPDES/SDS wastewater permit coverage at this reissuance. Additional discharge stations SD001 and SD002 have been included in the NPDES/SDS permit with specific limits and monitoring requirements for stormwater monitoring purposes. Sampling and monitoring at these stormwater SD stations is required on a quarterly basis through the life of the permit with the results averaged on the December Discharge Monitoring Report. There is also an Industrial Stormwater Chapter specific to your facility. References are made to an Inspection Report and Annual Report that can be found on the MPCA s website. Finally, there is a Benchmark Monitoring Factsheet on the website that must be used to ensure compliance with the limits and monitoring requirements for the facility. The documents can be found at: Total 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 are outlined in 40 CFR , Minn. R , and These conditions are listed in the Total Facility Requirements chapter of the NPDES/SDS Permit. These requirements cover a wide range of areas, including recordkeeping, sampling, equipment calibration, equipment maintenance, reporting, facility upsets, bypasses, solids handling, changes in operation, facility inspections, and permit modification and reissuance. Antidegredation and anti-backsliding Changes to the facility may result in an increase in pollutant loading to surface waters or other causes of degradation to surface waters. If a change to the facility will result in a net increase in pollutant loading or other causes of degradation that exceed the maximum loading authorized through conditions specified in the existing permit, the changes to the facility are subject to antidegradation requirements found in Minn. R to The Mississippi River was designated an Outstanding Resource Value Water (ORVW) on November 5, 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 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) of the Clean Water Act, United States Code, title 33, section 1342.]