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

Transcription

1 National Pollutant Discharge Elimination System (NPDES)/State Disposal System (SDS) Permit Program Fact Sheet Permittee: City of New Ulm 310 First North Street New Ulm, Minnesota Facility Name: New Ulm Wastewater Treatment Facility 3 Tower Road New Ulm, Minnesota Permit Number: MN Current Permit Expiration: September 30, 2014 Public Comment Period Begins: February 5, 2015 Period Ends: March 6, 2015 Receiving Water: Minnesota River (Class 2B, 3C, 4A, 4B, 5, 6 Water) Or Cottonwood River (Class 2B, 3C, 4A, 4B, 5, 6 Water) Proposed Action: Reissuance Permitting Contact Ashley Wahl 504 Fairgrounds Road, Suite 200 Marshall, Minnesota Phone: Fax:

2 Table of Contents Purpose and Participation... 3 Applicable Statutes... 3 Fact Sheet Purpose... 3 Public Participation... 3 Facility Description... 5 Facility Outfall and Location... 5 Map of Permitted Facility... 6 Components and Treatment Technology... 6 Flow Schematics... 7 Significant Industrial Users... 8 Recent Compliance History... 9 Recent Monitoring History Receiving Waters Use Classifications Impairments Expanded Fecal Coliform Bacteria Wasteload Allocation Existing Permit Effluent Limits State Discharge Restrictions Technology Based Effluent Limits Water Quality Based Effluent Limits Proposed Permit Effluent Limits Technology Based Effluent Limits Water Quality Based Effluent Limits Toxics Review for SD Background Summary Reasonable Potential for Chemical Specific Pollutants Mercury Salty Monitoring Acute Whole Effluent Toxicity Testing New Chronic WET Testing Toxics Review for SD Reasonable Potential for Chemical Specific Pollutants Mercury Salty Monitoring Phosphorus State and Federal Rules Downstream Water Quality Limit Determination Concentration Averaging Period Adjustment Summary

3 Additional Requirements Mercury Minimization Plan Nitrogen Monitoring Biosolids Total Facility Requirements Nondegradation and Anti-Backsliding References

4 Purpose and Participation Applicable Statutes This fact sheet has been prepared according to Title 40 CFR and and Minn R , subp. 3, in regards to a draft National Pollutant Discharge Elimination System (NPDES)/State Disposal System (SDS) Permit (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; and 3. The reasons supporting your position, stated with sufficient specificity as to allow the Commissioner to investigate the merits of your position. You may also request that the MPCA Commissioner hold a public informational meeting. A public informational meeting is an informal meeting which the MPCA may hold to help clarify and resolve issues. In accordance with Minn. R and Minn. R , your petition requesting a public informational meeting must identify the matter of concern and must include items 1 through 3, identified above and a statement of the reasons the MPCA should hold the meeting; and the issues you would like the MPCA to address at the meeting. In addition, you may submit a petition for a contested case hearing. A contested case hearing is a formal hearing before an administrative law judge. Your petition requesting a contested case hearing must include a statement of the reasons or proposed findings supporting the MPCA decision to hold a contested case hearing pursuant to the criteria identified in Minn. R , subp. 1, and a statement of the issues proposed to be addressed by a contested case hearing and the specific relief requested. To the extent known, your petition should include a proposed list of witnesses to be presented at the hearing, a proposed list of publications, references or studies to be introduced at the hearing, and an estimate of time required for you to present the matter at hearing. You must submit all comments, requests, and petitions during the public comment period identified on page 1 of this notice. All written comments, requests, and petitions received during the public comment period will be considered in the final decisions regarding the permit. If the MPCA does not receive any written comments, requests, or petitions during the public comment period, the Commissioner or other MPCA staff, as authorized by the Commissioner will make the final decision concerning the draft permit. During the public comment period, however, you may request that the draft permit be presented to the MPCA s Citizens Board (Board) for final decision. You may participate in the activities of the Board as provided in Minn. R

5 Comments, petitions, and/or requests must be submitted by the last day of the public comment period to: Ashley Wahl Minnesota Pollution Control Agency 504 Fairgrounds Road, Suite 200 Marshall, Minnesota The Permit will be reissued if the MPCA determines that the proposed Permittee will, with respect to the facility or activity to be permitted, comply or undertake a schedule to achieve compliance with all applicable state and federal pollution control statutes and rules administered by the MPCA and the conditions of the permit and that all applicable requirements of Minn. Stat. ch. 116D and the rules promulgated thereunder have been fulfilled. More detail on all requirements placed on the facility may be found in the Permit document. Facility Description Facility and Outfall Location The New Ulm Wastewater Treatment Facility (Facility) is located in the NE ¼ of the SW ¼ of Section 34, Township 110 North, Range 30 West, Cottonwood Township, Brown County, Minnesota. The Facility has two continuous discharge points. Discharge point SD002 to the Minnesota River (Class 2B, 3C, 4A, 4B, 5, 6 Water) is used during normal conditions. Discharge point SD003 to the Cottonwood River (Class 2B, 3C, 4A, 4B, 5, 6 Water) is used during high water periods when there is insufficient hydraulic capacity for the effluent in the SD002 outfall line. The location of the Facility, SD002, and SD003 are shown in Figure 1. 5

6 Figure 1. Location of Permitted Facility and Discharge Stations 6

7 Components and Treatment Technology Current Information The application and plans indicate that the Facility consists of two separate pretreatment systems and a secondary treatment system. The original pretreatment system, located at the site of the old trickling filter facility, is a half-mile from the secondary treatment facility and processes the majority of the city of New Ulm s (City) wastewater. In 1998, the City was approved to accept wastewater from the city of Courtland. A new pretreatment system was built to accommodate a small portion of the City s wastewater and all of the wastewater from the city of Courtland. This second pretreatment system is located at the secondary treatment facility. Both pretreatment systems contain bar screens, aerated grit removal chambers, grit washing, comminutor and flow metering. After pretreatment, the waste streams join. The secondary wastewater treatment system consists of dual lift stations, two primary clarifiers, a biological phosphorus removal system which includes one anoxic basin and one anaerobic basin, a back up ferric chloride chemical feed phosphorus removal system, four complete mix-aerated-activated sludge tanks, and three final clarifiers. There is one chlorination tank composed of two cells operated in series, which may be operated separately. The effluent is dechlorinated using sulfur dioxide prior to discharge. Thickened primary sludge and waste-activated sludge generated by the wastewater treatment process are sent through an aerated solids balancing tank, gravity thickened, and then pumped to the preautothermal thermophilic aerobic digestion (ATAD) holding tank. The holding tank ensures that a constant volume of sludge is pumped into the ATAD process on a daily basis. From the ATAD process, biosolids are pumped to one of four storage basins and land applied. The ATAD system was designed to process solids at a rate that correlates to a waste solids loading to the ATAD system of 39,375 gallons per day (gpd) at four percent (combined primary and secondary solids). The final clarifiers were designed for a peak hourly wet weather flow of 9.4 million gallons per day (mgd). The biosolids, generated as a result of the ATAD process, are a liquid slurry of exceptional quality sewage sludge. The Facility is currently rated for an average wet weather (AWW) design flow of 6.77 mgd, with a fiveday carbonaceous biochemical oxygen demand (CBOD 5 ) concentration of 428 milligrams per liter (mg/l) or 24,166 pounds per day. The average dry weather flow of the Facility is 2.28 mgd. Changes to Facility or Operation There are no proposed changes to the Facility at this time. 7

8 Flow Schematic Figure 2. Flow Schematic 8

9 Significant Industrial Users (SIUs) At the time of permit reissuance, there are four SIUs of the Facility: Associated Milk Producers, Inc. (AMPI), August Shell Brewing Company, Firmenich, and Kraft Foods Global Incorporated. Table 1. SIU Processes and Flow Information SIU Process Type Production Rate Associated Milk Producers, Inc. Food, Dairy Products Processing 66,000 gallons per day (AMPI) August Shell Brewing Company Food, Beverage Production 52,000 gallons per day Firmenich Food Processing 50,000 gallons per day Kraft Foods Global Incorporated Food, Dairy Products Processing 138,000 gallons per day The Permittee is delegated by the MPCA to administer its own pretreatment program. The MPCA has been delegated authority to approve local Publicly Owned Treatment Works pretreatment programs by the U.S. Environmental Protection Agency (EPA). Recent Compliance History A Compliance Evaluation Inspection (CEI) was conducted on October 29, 2014, by the MPCA to determine the Facility s compliance with the terms and conditions of its NPDES/SDS Permit. The CEI consisted of a visual inspection of the Facility and a discussion with Wastewater Treatment Plant Supervisor and the Assistant Wastewater Treatment Plant Supervisor. In addition, there was a review of the monthly Discharge Monitoring Reports (DMRs) for the time period from May 2012 through September The Facility s biosolids land application sites, biosolids related recordkeeping requirements, and the second pretreatment system serving wastewater from the city of Courtland was not inspected. Based on the results of the CEI, no violations of the terms and conditions set forth in the NPDES/SDS Permit were noted. 9

10 Recent Monitoring History Table 2: Discharge Monitoring Report Results November 2013 Through October 2014, Station SD002 Main Facility Discharge Table 3: Discharge Monitoring Report Results November 2013 Through October 2014, Station SD003 Backup Discharge 10

11 Receiving Waters Use Classification The Facility has two continuous discharge points. Discharge point SD002 to the Minnesota River is used during normal conditions. Discharge point SD003 to the Cottonwood River is used during high water periods when there is insufficient hydraulic capacity for the effluent in the SD002 outfall line. Both waters are classified as a 2B, 3C, 4A, 4B, 5, 6 water. This classification indicates that the body of water is capable of sustaining aquatic life and recreation. Aquatic life and recreation include supporting or the ability to support fish, other aquatic life, bathing, boating, or other recreational purposes and for which water quality control is or may be necessary to protect aquatic or terrestrial life and its habitat or public health, safety, or welfare. More information on the classification of waters can be found in Minn. R Impairments Table 4. Impairments of the Receiving Waters Station SD002 AUID or Lake ID # AUID description or Lake name Assessment Category & subcategory Minnesota River: Eightmile Cr to 4A Cottonwood R Minnesota River: Eightmile Cr to Cottonwood R Table 5. Impairments of the Receiving Waters Station SD003 AUID or Lake ID # AUID description or Lake name Assessment Category & subcategory Cottonwood River : JD 30 to Minnesota R Cottonwood River : JD 30 to 4A Minnesota R Cottonwood River : JD 30 to Minnesota R Pollutants or Impairment Mercury in fish tissue 5 PCB in fish tissue Pollutants or Impairment 5 Fecal Coliform Mercury in fish tissue 5 Turbidity Expanded Fecal Coliform Bacteria Wasteload Allocation The Facility includes two permitted discharge points (SD002 and SD003). SD002 discharges to the Minnesota River and used during normal flow conditions. SD003 discharges to the Cottonwood River and is used during high water periods. The Facility has an AWW design flow of 6.77 mgd. The permitted fecal coliform limit at both SD002 and SD003 is 200 organisms per 100 milliliters (ml) (April through October). On January 8, 2014, the Cottonwood River Fecal Coliform Total Maximum Daily Load (TMDL) report was approved by the U.S. Environmental Protection Agency. For wastewater treatment facilities (WWTFs), the wasteload allocations (WLAs) were calculated by multiplying AWW design flow for continuously discharging WWTFs or the maximum permitted discharge rate for controlled discharge pond facilities by the permitted discharge fecal coliform limit of 200 organisms per 100 ml. As long as the WWTF s discharge at or below this Permit limit, they will not cause violations of the water quality standard regardless of their fecal coliform load. 11

12 An analysis of the effects of expanded WLA, 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. The Cottonwood River Fecal Coliform TMDL study did not include a WLA for the New Ulm WWTF s SD003 permitted discharge. This NPDES/SDS Permit authorizes the expansion of the WLA for the New Ulm WWTF. Expansion of the WLA will not contribute to the Fecal Coliform impairment in the Cottonwood River because the NPDES/SDS Permit s Fecal Coliform permitted discharge limit of 200 organisms per 100 ml is equivalent to the water quality standard. The New Ulm WWTF is designed to treat an AWW design flow of up to 6.77 mgd (12.58 cubic feet per second (cfs)). This results in an increase of cfs of flow from the New Ulm WWTF to the Cottonwood River, which in turn expands the fecal coliform loading capacity by billion organisms/day (b-org/day). The discharge will not result in a decrease in the Cottonwood River s water quality because fecal coliform bacteria loading capacities will increase as a result of the increased stream flow resulting from the discharge. Table 6. WLA Modification New Ulm WWTF s WLA Expansion Cottonwood River (AUID ) Loading Capacity Expansion Approved Wasteload Allocation 0 b-org./day Flow Increase Fecal Coliform Load Increase cfs b-org./day cfs b-org./day Modified Wasteload Allocation b- org./day 12

13 Existing Permit Effluent Limits The limits and monitoring requirements in the current permit are presented in Tables 7 and 8. These tables list state discharge restrictions and both water quality and technology-based limits. Table 7. Existing Effluent Limits for SD

14 Table 8. Existing Effluent Limits for SD003. State Discharge Restrictions (SDRs) The limit for fecal coliform has been developed to meet state discharge restrictions specified under Minn. R Technology Based Effluent Limits The Total Suspended Solids (TSS), CBOD 5, and ph limits are technology-based limits developed for achieving secondary treatment standards. These limits are specified in 40 CFR and in Minn. R

15 Water Quality Based Effluent Limits (WQBELs) The total residual chlorine (TRC) limit for SD002 and SD003 and the ammonia-nitrogen limits for SD002 are WQBELs. These effluent limits are based on the designated use classification of the receiving water. Water quality based limits are the limits which were determined to be necessary to protect the use classification for the receiving water. Proposed Permit Effluent Limits The limits and monitoring requirements for the draft reissued Permit are presented in Tables 9, 10, and 11. These tables list state discharge restrictions, and both water quality and technology-based effluent limits. 15

16 Table 9. Proposed Effluent Limits and Monitoring for SD

17 Table 10. Proposed Effluent Limits and Monitoring for SD

18 Table 11. SD004: Mass Limits Calculation Station for SD002 and SD003. Technology Based Effluent Limits The TSS, CBOD 5, and ph limits are technology-based limits developed for achieving secondary treatment standards. These limits are specified in 40 CFR and in Minn. R Water Quality Based Effluent Limits (WQBELs) The ammonia-nitrogen and the fecal coliform limits for SD002 and the total phosphorus (TP) limits for SD002 and SD003 are WQBELs. These effluent limits are based on the designated use classification of the receiving water. Water quality based limits are the limits which were determined to be necessary to protect the use classification for the receiving water. Toxics Review for SD002 Background Summary The discharge is located on the Minnesota River. This portion of the Minnesota River has the following water classification: 2B, 3C, 4A, 4B, 5, and 6.The Facility has submitted three whole effluent toxicity (WET) tests and three priority pollutant scans since The average dry weather design flow (ADWF) is used to calculate WQBELs under critical low flow stream conditions. The ADWF for this Facility is 2.28 mgd. The low flow condition is defined by the once in 10 year weekly average flow (7Q 10 ), which is determined to be cfs or mgd. The analysis below is based on data submitted to date. Reasonable Potential for Chemical Specific Pollutants (40CFR122.44(d)(1)) Federal regulations require the MPCA to evaluate the discharge to determine whether the discharge has the reasonable potential to cause or contribute to a violation of water quality standards. The MPCA 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 but chloroform of the organic priority pollutants were below the level of detection. Since these pollutants were at low enough levels not to be detected, reasonable potential to cause or contribute to a water quality standards excursion is not indicated. 18

19 Table 12 contains the inputs to the reasonable potential analysis for total arsenic, total copper, total chloroform, total selenium, and total mercury. The analysis is made with effluent data that is expressed as total metal. These pollutants were evaluated on the basis of analytical measurements that made evident the need for a full determination. Reasonable potential to cause or contribute to the excursion above a water quality standard has not been indicated for any of the five pollutants listed above. No effluent limits are needed. 19

20 Table 12. Inputs to Reasonable Potential Analysis P arameter As (ug/l) Cu (ug/l) chloroform (ug/l) Se(ug/L) Hg (ng/l) Max Measured Value # data points PEQ Plant flow ADW (mgd) Rec. water flow, 7Q10(mgd) Background Conc. (see below) Continuous Std (cs) ppm hard Maximum Std (ms) ppm hard Final Acute Value (FAV) ppm hard Mass Balance -cs Mass Balance -ms Coeff of Variation (CV) Long Term Avg-cs Long Term Avg-ms Preliminary Effl limits: Daily Max Monthly Ave (2x/month) Reasonable Potential PEQ>Daily max FALSE FALSE FALSE FALSE FALSE PEQ>Monthly Ave. FALSE FALSE FALSE FALSE FALSE PEQ> FAV FALSE FALSE FALSE FALSE FALSE Final Reasonable Potential No No No No No Notes Actual hardness is over 500 ppm. Per Minn Rule , subpart 4, hardness can not exceed 400 ppm for any hardness related WQS. Will use 400 ppm hardness for the effluent and for the receiving water Three acute WET tests were performed during the last permit cycle- no toxicity found background for selenium and arsenic from general Minn River above this outfall (this review)- station S background for copper is from 2009 reasonable potential review. Minn River mile 196 * Mercury background assumed to be at the standard because of the statewide mercury TMDL. 20

21 Mercury Monitoring results of the effluent include 18 data points at a calculated CV of Projected effluent quality (PEQ) is derived as an upper bound value from the highest value measured (4.1 nanograms per liter (ng/l)), and the determined variability (CV = ) and number of data points (18). 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 ng/l) is applied at the point of discharge for the mass balance equation for the subsequent preliminary effluent limit calculations. Where PEQ exceeds the PEL, there is reasonable potential to cause or contribute to a water quality standards excursion. Since PEQ does not exceed the PEL in this case, reasonable potential to cause or contribute to an excursion above water quality standards is not indicated. A water quality-based effluent limit (WQBEL) is not needed. The draft permit contains twice per year effluent sampling for total mercury, dissolved mercury with a concurrent total suspended solids sample. Salty Monitoring Requirements Because this Facility is now accepting reverses osmosis (RO) reject from the August Shell Brewing Company, the Facility will now have to monitor once per month for the following parameters: chloride, hardness, specific conductance, total dissolved solids, sulfates, bicarbonates, calcium, magnesium, and potassium. Acute Whole Effluent Toxicity During the last permit cycle the Facility ran three acute WET tests. For each of thewet tests, all the species tested had less than 1.0 TUa (Toxic Unit acute). As such, there was no reasonable potential for an acute WET limit at this Facility. New Chronic WET Testing Monitoring Requirements In regards to WET testing, if the ratio of the 7Q10 flow to the ADWF is greater than 20:1, acute WET testing is required. If the ratio is 20:1 or less, then chronic WET testing is recommended. The ADWF for this Facility is fairly old and as such, the MPCA staff reviewed the average winter flow to be used as a measure of a more current ADWF. The average winter flow for this facility is 1.84 mgd. The ratio of the 7Q10 river flow of to the ADWF (winter flow) of 1.84 mgd is Since the ratio is less than 20:1, annual chronic WET monitoring is required as part of the reissued Permit Using the 7Q10 flow of mgd and the winter flow of 1.84 mgd the receiving water concentration (RWC) is 5.2% and the applicable Toxic Unit chronic (TUc) number is 19.2 TUc. The 19.2 TUc is a monitoring threshold value, not a WET limit. The draft permit requires annual WET testing. If the permit exceeded five years, there will be an additional WET test for each year that exceeds the five year permit cycle. If the monitoring threshold value of 19.2 TUc is exceeded for any one WET test, the facility will perform two WET retests to determine if a Toxicity Reduction Evaluation (TRE) is needed. 21

22 Toxics Review for SD003 Reasonable Potential for Chemical Specific Pollutants (40CFR122.44(d)(1)) The discharge is located on the Cottonwood River. This section of the Cottonwood River has the following water classification: 2B, 3C, 4A, 4B, 5, and 6. This particular outfall is only active when the Minnesota River is at high flows. The ADWF is used to calculate water quality-based effluent limits under critical low flow stream conditions. The ADWF for this facility is 2.28 mgd. The low flow condition is defined by the once in 10 year weekly average flow (7Q 10 ), which is determined to be cfs ( mgd). The analysis below is based on data submitted to date. This discharge is only used during high river flow events. Because this outfall is rarely utilized, very few sampling events occurred. The only pollutant sample that was taken was one mercury sample. The MPCA does not do reasonable potential based on one sample. As such no reasonable potential evaluation was done for this outfall. Mercury In the event there are adequate discharge events at SD003, the draft permit will require twice per year effluent sampling for total mercury, dissolved mercury with a concurrent total suspended solids sample. Salty Monitoring Requirements Because this Facility is now accepting RO reject from the August Shell Brewing Company, the Facility will now have to monitor once per month for the following parameters: chloride, hardness, specific conductance, total dissolved solids, sulfates, bicarbonates, calcium, magnesium, and potassium. Phosphorus State and Federal Rules (Lake Pepin and Federal Regulations) The Facility discharges upstream of Lake Pepin, a reservoir on the Mississippi River. In 2002, Lake Pepin was placed on the federal Clean Water Act Section 303(d) list of impaired waters due to excess nutrients. A total maximum daily load (TMDL) study 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 requires all NPDES dischargers that have reasonable potential (RP) to cause or contribute to downstream impaired waters, have a WQBEL. When determining reasonable potential, the Code of Federal Regulations also states that the MPCA shall use procedures which account for existing controls on point and nonpoint sources of pollution. Permittees are found to have RP for TP if: 1) they discharge upstream of a nutrient impaired waterbody, 2) they discharge at TP concentrations greater than the ambient target, and 3) there is no geographical barrier capable of trapping a significant mass of nutrients between the outfall and the impairment. For all reasons listed above, the Facility has RP to contribute to the excess TP in Lake Pepin. Therefore, the Facility is required to have a TP WQBEL. The draft permit contains a is 7,482 kilogram per year (kg/yr) TP WQBEL, which was derived from a draft TMDL WLA as described later. 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 computer reservoir model for Lake Pepin was developed by the MPCA modeling consultant, LimnoTech, to evaluate site specific eutrophication standards and the reductions necessary to achieve these standards (LTI 2009). Using the best available science, draft standards for Lake Pepin were determined to be 100 micrograms per liter (µg/l) for TP and 28 µg/l for chlorophyll-a (Heiskary and Wasley 2012). Within the model, all major sources of TP upstream of Lake Pepin were considered, and 21 separate scenarios were developed. Scenario 17 achieved compliance with the draft criteria and predicted the following TP reductions from tributaries would be necessary: 50 percent from the 22

23 Minnesota River and Cannon River and 20 percent from the Mississippi River upstream of Lock and Dam 1 and the St. Croix River. Again, per Code of Federal Regulations, it was assumed that reductions would be from both point and nonpoint sources. During the modeling process, the MPCA staff simultaneously developed draft WLAs, compatible with scenario 17 reductions for all NPDES dischargers within the contributing watershed. All simulations represented point source on a 12 month basis and not as a five month seasonal period. Downstream Water Quality Currently Minnesota has numeric lake eutrophication standards and is scheduled to adopt river eutrophication standards (RES) in An evaluation to determine if the Facility s discharge could contribute to downstream lake or river eutrophication exceedances was completed. The nearest downstream river reach with sufficient data from which to evaluate river eutrophication is the Minnesota River (AUID ). Current (10 year) summer mean Chl-a and TP at this reach is 74 µg/l and 190 µg/l, respectively. Both the cause variable, TP, and response variable, Chl-a, exceed the proposed RES (Heiskary 2013). A memorandum describing phosphorus loading and point source reductions in the greater Minnesota River Basin states, the WQBELs necessary for Lake Pepin are sufficient to meet RES in several reaches of the Minnesota River (Wasley, 2013). This document looked at the majority of the WWTPs in the Minnesota River in one analysis rather than looking at each WWTP separately. Limit Determination A categorical approach was used to develop individual WLAs for the draft Lake Pepin TMDL. The draft Lake Pepin TMDL classifies New Ulm as a municipal major which includes continuously discharging municipal facilities with AWW design flowss < 20 and > 1.0 mgd. Facilities within this category are allotted mass limits based on AWW design flow and a TP concentration multiplier of 0.8 mg/l as follows: General Formula: WLA kg/yr = (AWW design flow x 0.8mg/L TP x liters per gallon (L/gal) x 365 days/yr) New Ulm WWTF WLA: 7,482 kg/yr TP = (6.77mgd x 0.8mg/L x L/gal x 365 days/yr) Concentration Averaging Period Adjustment Permitting staff and effluent limits staff discussed and agreed to change the monthly TP concentration and mass limits to a 12 month moving average limit in Minnesota rule , subp.6 allows for a 12 month moving average when two conditions are met. First, there are no predicted adverse effects of TP loading to the Minnesota River or Lake Pepin from changing from a monthly concentration limit to a 12 month moving average limit. Second, the facility has biological phosphorus removal which limits the use of chemicals which is an environmental benefit. Compliance with the 12 month moving average will be assessed each month. Summary The Facility discharges upstream of a river reach in excess of the draft RES. It was determined that the Facility has RP to cause or contribute to the excess nutrient impairment in Lake Pepin and is therefore required to have a WQBEL. A rolling total 12 month total mass TP effluent limit of 7,482 kg/yr will insure that downstream water quality standards can be achieved in both the Minnesota River and Lake Pepin. The existing mass limit will be dropped from the Permit. The averaging period for the current 1.0 mg/l TP concentration limit should be changed to a 12 month averaging period. More restrictive TP limits may be necessary following the completion of the Lake Pepin TMDL study and the adoption of numeric river nutrient criteria during the next triennial rulemaking session. 23

24 Additional Requirements Mercury Minimization Plan (MMP): The Limits and Monitoring section of this draft permit contains requirements for twice per year effluent total and dissolved mercury monitoring, with a concurrent grab sample for TSS, and for submittal of an updated MMP. These requirements were added in response to the EPA s approval of the Minnesota statewide mercury TMDL plan. The specific language regarding these requirements are in Chapter 3: Mercury Pollutant Minimization Plan of this draft reissued Permit. Nitrogen Monitoring 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 2013 the MPCA completed a draft 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 your Facility additional influent and effluent nitrogen monitoring has been added to the permit. This monitoring has been added in accordance with Minn. Stat. ch 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 once per month for the five-year term of the permit. Biosolids This draft reissued permit authorizes the city to store and land apply domestic wastewater treatment biosolids in accordance with the provisions of Chapter 8 of this draft permit and Minn. R. ch Total Facility Requirements (TFR) All NPDES permits issued in the state of Minnesota contain certain conditions that remain the same regardless of the size, location, or type of discharge. The standard conditions satisfy the requirements outlined in 40 CFR These conditions are listed in the Total Facility Requirements chapter of an NPDES permit. These requirements cover a wide range of areas including recordkeeping, sampling, equipment calibration, equipment maintenance, reporting, facility upsets, bypass, solids handling, changes in operation, facility inspections, and permit reissuance. Nondegradation and Anti-Backsliding In accordance with the MPCA s rules regarding nondegradation for all waters that are not ORVW, nondegradation review is required for any new or expanded significant discharge (Minn. R ). A significant discharge is: 1. A new discharge (not in existence before January 1, 1988) that is greater than 200,000 gpd to any water other than a Class 7 water; 2. An expanded discharge that expands by greater than 200,000 gpd that discharges to any water other than a Class 7 water; or 3. A new or expanded discharge containing any toxic pollutant at a mass loading rate likely to increase the concentration of the toxicant in the receiving water by greater than 1% over the baseline quality. 24

25 The flow rate used to determine significance is the AWW design flow. The January 1, 1988, AWW design flow for this Facility is 6.77 mgd. This permit also complies with Minn. R , regarding anti-backsliding. Any point source discharger of sewage, industrial, or other wastes for which an NPDES Permit has been issued by the MPCA that contains effluent limits more stringent than those that would be established by Minn. R to Minn. R shall continue to meet the effluent limits established by the permit, unless the permittee establishes that less stringent effluent limits are allowable pursuant to federal law, under section 402(o) (2) (A) of the Clean Water Act, United States Code, title 33, section

26 References Heiskary, S. and D. Wasley Mississippi River Pools 1 through 8: Developing River, Pool and Lake Pepin Eutrophication Criteria. MPCA St. Paul 81 pp LimnoTech Upper Mississippi River-Lake Pepin Quality Model. Development, Calibration and Application. Prepared for MPCA by LimnoTech, Ann Arbor, MI Steven Heiskary, Dr. R. William Bouchard, Jr. and Dr. Howard Markus Minnesota Nutrient Criteria Development for Rivers MPCA St. Paul 176 pp Wasley, D.M Phosphorus Effluent Limit Review: Minnesota River Basin, MPCA St. Paul 17 pp 26