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National Pollutant Discharge Elimination System (NPDES)/
State Disposal System (SDS) Permit Program Fact Sheet
Permit Reissuance
MN0020567 Permittee: City of Monticello
505 Walnut Street Monticello, Minnesota 55362-8822
Facility name: Monticello Wastewater Treatment Facility 1401 Hart Boulevard
Monticello, Minnesota 55362 Current permit expiration date: November 30, 2017 Public comment period begins: March 6, 2020 Public comment period ends: May 4, 2020 Receiving water: Mississippi River - Class 1C, 2Bd, 3C, 4A, 4B, 5, 6 Water Permitting contact: Sarah Starr Minnesota Pollution Control Agency 520 Lafayette Road North St. Paul, Minnesota 55155-4194 651-757-2335 [email protected]
Table of Contents Page
Purposeandparticipation................................................................................................................................................................ ...................4
Applicablestatutes................................................................................................................................................................ ..............................4
Purpose................................................................................................................................................................................................ ....................4
Publicparticipation............................................................................................................................................................................................4
Facilitydescription.................................................................................................................................................................................................5
Backgroundinformation..................................................................................................................................................................................5
Facilitylocation................................................................................................................................................................................................ ....5
Outfalllocation................................................................................................................................................................ .....................................5
Mapofpermittedfacility..................................................................................................................................................................................6
Componentsandtreatmenttechnology....................................................................................................................................................7
Currentinformation................................................................................................................................................................ ...........................7
Flowschematic.....................................................................................................................................................................................................8
Changestofacilityoroperation.....................................................................................................................................................................8
Significantindustrialusers(SIUs).................................................................................................................................................................9
Recentcompliancehistory................................................................................................................................................................ ...............9
Recentmonitoringhistory.............................................................................................................................................................................10
Receivingwater(s)................................................................................................................................................................ ................................10
Useclassification................................................................................................................................................................ ...............................10
Impairments&TotalMaximumDailyLoads(TMDLs)........................................................................................................................11
WasteloadAllocations:................................................................................................................................................................ ....................11
Existingpermiteffluentlimits................................................................................................................................................................ .........12
Technologybasedeffluentlimits(TBELs)................................................................................................................................................12
Waterqualitybasedeffluentlimits(WQBELs).......................................................................................................................................12
State discharge restrictions (SDRs)...............................................................................................................................................................12
Proposedpermiteffluentlimits......................................................................................................................................................................13
Technologybasedeffluentlimits(TBELs)................................................................................................................................................13
Waterqualitybasedlimits(WQBELs).......................................................................................................................................................13
State discharge restrictions (SDRs)...............................................................................................................................................................13
TotalPhosphorusWQBEL..............................................................................................................................................................................15
ReasonablePotentialforChemicalSpecificPollutants.......................................................................................................................16
ReasonablePotentialforPriorityPollutants..........................................................................................................................................19
ReasonablePotentialforMercury...............................................................................................................................................................20
ReasonablePotentialforCopper................................................................................................................................................................ .20
ReasonablePotentialforWET......................................................................................................................................................................20
Additionalrequirements....................................................................................................................................................................................20
TotalNitrogen....................................................................................................................................................................................................20
Pollutantminimizationplans.......................................................................................................................................................................21
MMP................................................................................................................................................................................................ .......................21
Complianceschedules......................................................................................................................................................................................21
Variances................................................................................................................................................................ ..............................................21
Totalfacilityrequirements(TFR)...................................................................................................................................................................21
Antidegradationandanti-backsliding..........................................................................................................................................................21
TermofPermit................................................................................................................................................................................................ .......22
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 4 of 22 Purpose and participation Applicable statutes This fact sheet has been prepared according to the 40 CFR § 124.8 and 124.56 and Minn. R. 7001.0100, 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 that the MPCA may hold to help clarify and resolve issues. In accordance with Minn. R. 7000.0650 and Minn. R. 7001.0110, 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. 7000.1900, 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:
Sarah Starr Minnesota Pollution Control Agency 520 Lafayette Road North St. Paul, Minnesota 55155-4194
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 5 of 22 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 Monticello Wastewater Treatment Facility (Facility) is located on the southeast side of Monticello at: 1401 Hard Boulevard, Monticello, Minnesota, 55362, Wright County. Outfall location The Facility’s discharge outfall (SD 001) is located in the SE ¼ of the SW ¼ of Section 12, Township 121 North, Range 25 West, Monticello, Wright County, Minnesota.
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 6 of 22 Map of permitted facility
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 7 of 22 Components and treatment technology Current information The Monticello Wastewater Treatment Facility (Facility) is located at 1401 Hart Boulevard, Monticello, Minnesota 55362, Wright County. This is a Class A Facility. The existing Facility consists of screening, grit removal, three wastewater pumps, three sequencing batch reactors with activated sludge for biological treatment, and chlorination/dechlorination equipment. Existing biosolids treatment consists of dissolved air floatation thickening and primary and secondary anaerobic sludge digestion. Biosolids are stored in a storage tank prior to being disposed of by either land application or dewatering and landfilling. A carbon absorption filter controls odor from the headworks building. Odor from biosolids processing is controlled by a biofilter. The Facility has a continuous discharge (SD 001) to the Mississippi River (Class 1C, 2Bd, 3C, 4A, 4B, 5, 6 water) and is designed to treat an average wet weather flow of 2,360,000 gallons per day (gpd) and an average dry weather flow of 1,790,000 gpd. The Facility is designed to treat wastewater with a 5-day carbonaceous biochemical oxygen demand (CBOD5) strength of 468 milligrams per liter. There are no known bypass or overflow points known to exist at this Facility.
The Mississippi River was designated an Outstanding Resource Value Water (ORVW) on November 5, 1984. The design average wet weather flow of this Facility on the date of ORVW designation is 1,200,000 gpd.
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 8 of 22 Flow schematic
Changes to facility or operation There have been no changes to the Facility or its operation from the previous permit. No changes are proposed for the next permit term.
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 9 of 22 Significant industrial users (SIU) There is one SIU that contributes process wastewater to the Facility. Cargill Kitchen Solutions processes eggs and contributes approximately 110,000 gpd of continuously flowing process wastewater and 6,000 gpd of continuously flowing non-process wastewater. The Facility has a pretreatment agreement, which includes local limits, with Cargill Kitchen Solutions. None of the permit limits are based on the SIU’s wastewater contribution. Recent compliance history A Compliance Evaluation Inspection (CEI) was conducted at the Facility on August 14, 2018, by the MPCA staff 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, a discussion with staff, and a review of the monthly Discharge Monitoring Reports for the time period of October 2016 through September 2017. The Facility was compliant overall, with one round of nitrogen sampling missed in September 2014 (N+N, TKN, TDS). This issue was resolved through a previous inspection report.
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 10 of 22 Recent monitoring history Table 1: Monticello WWTF Discharge Monitoring Report summary for SD 001 from December 2018 through November 2019
Receiving water(s) Use classification The Facility has a continuous discharge via surface discharge station SD 001 to the Mississippi River. This water is classified as a Class 1C, 2Bd, 3C, 4A, 4B, 5, 6 Water. The Mississippi River was designated an Outstanding Resource Value Water (ORVW) on November 5, 1984. The design average wet weather flow of this Facility on the date of ORVW designation is 1,200,000 gpd. 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.
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 11 of 22 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 waters. 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. 7050.0140. Impairments & Total Maximum Daily Loads (TMDL) The Facility discharges to the Mississippi River. There are 42 impairments downstream of this discharge including mercury in fish tissue, mercury in the water column, fecal coliform, total suspended solids, nutrients, PCBF, PFOS-F, and PFOS-W. Following are the draft and final TMDLs that are applicable to this Facility.
Wasteload Allocations: Upper Mississippi River – Bacteria TMDL
· Bacteria WLA = 11.3 billion organisms per day (page 46, Table 4-2) · This WLA is equivalent to the current permitted fecal coliform limit of 200 org/100 ml.
South Metro Mississippi TMDL Turbidity Impairment (TSS)
· TSS WLA = 49,640 kg/year and 136.00 kg/day (page 97) · This WLA is equivalent to the current permitted effluent TSS limit. · This Facility is included in Appendix A.1, of the TMDL, Minnesota Wastewater Permits with TSS limits
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 12 of 22 Draft Lake Pepin – Excess Nutrients TMDL
· Draft Total Phosphorus WLA = 2,608 kg/year 12-month moving total and 7.145 kg/day. · This draft WLA is equivalent to the current permitted effluent total phosphorus limit.
Existing permit effluent limits The effluent limits and monitoring requirements for SD 001 in the current permit are presented in Table 3 at the end of this section. Applicable TBELs, WQBELs, and SDRs are explained below. Technology based effluent limits (TBEL) Total suspended solids (TSS), 5-day carbonaceous biochemical oxygen demand (CBOD5), and pH limits are technology-based limits developed for achieving secondary treatment standards. These limits are specified in 40 CFR §133.102, Minn. R. 7050.0211 and Minn. R. 7053.0215. Water quality based effluent limits (WQBEL) The limits for total phosphorus, total residual chlorine, and total mercury are WQBELs. WQBELs are established to meet applicable water quality standards. Under 40 CFR 122.44(d)(1)(i), all dischargers who have a reasonable potential to cause or contribute to an exceedance of a water quality standard are required to have a WQBEL. State discharge restrictions (SDR) The limit for fecal coliform bacteria is a state discharge restriction. This limit is specified in Minn. R. 7053.0215, subp. 1. Table 2: Current effluent limits and monitoring requirements (SD 001)
Parameter Limit Units Limit Type Effective Period Sample Type Frequency
CBOD5 114 kg/day calendar month average Jan-Dec 24-Hour Flow Composite 3 x Week
CBOD5 182 kg/day maximum calendar week average Jan-Dec 24-Hour Flow Composite 3 x Week
CBOD5 25 mg/L calendar month average Jan-Dec 24-Hour Flow Composite 3 x Week
CBOD5 40 mg/L maximum calendar week average Jan-Dec 24-Hour Flow Composite 3 x Week
CBOD5 % Removal 85 % minimum calendar month average Jan-Dec Calculation 3 x Week
Chlorine, Total Residual 0.038 mg/L daily maximum Jan-Dec Grab 1 x Day
Fecal Coliform 200 #100ml calendar month geometric mean Apr-Oct Grab 3 x Week
Flow Monitor only mgd calendar month average Jan-Dec Measurement, Continuous 1 x Day
Flow Monitor only mgd calendar month maximum Jan-Dec Measurement, Continuous 1 x Day
Flow Monitor only MG calendar month total Jan-Dec Measurement, Continuous 1 x Day
Mercury, Dissolved Monitor only ng/L calendar month maximum Jan-Dec Grab 1 x Month
Mercury, Total 6.9 ng/L 12 month moving average Jan-Dec Grab 1 x Month
Mercury, Total Monitor only ng/L calendar month average Jan-Dec Grab 1 x Month
Nitrite Plus Nitrate, Total Monitor only mg/L calendar month average Apr, Sep 24-Hour Flow Composite 1 x Month
Nitrogen, Ammonia, Total Monitor only mg/L calendar month average Jan-Dec 24-Hour Flow Composite 1 x Month
Nitrogen, Kjeldahl, Total Monitor only mg/L calendar month average Apr, Sep 24-Hour Flow Composite 1 x Month
Oxygen, Dissolved Monitor only mg/L calendar month minimum Jan-Dec Grab 1 x Day
pH 6.0 SU calendar month minimum Jan-Dec Grab 1 x Day
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 13 of 22 pH 9.0 SU calendar month maximum Jan-Dec Grab 1 x Day
Phosphorus, Total 2608 kg/yr 12 month moving total Jan-Dec 24-Hour Flow Composite 1 x Week
Phosphorus, Total Monitor only mg/L calendar month average Jan-Dec 24-Hour Flow Composite 1 x Week
Phosphorus, Total Monitor only kg/mo calendar month total Jan-Dec 24-Hour Flow Composite 1 x Week
TDS Monitor only mg/L calendar month average Apr, Sep 24-Hour Flow Composite 1 x Month
TSS 136 kg/day calendar month average Jan-Dec 24-Hour Flow Composite 3 x Week
TSS 204 kg/day maximum calendar week average Jan-Dec 24-Hour Flow Composite 3 x Week
TSS 30 mg/L calendar month average Jan-Dec 24-Hour Flow Composite 3 x Week
TSS 45 mg/L maximum calendar week average Jan-Dec 24-Hour Flow Composite 3 x Week
TSS % Removal 85 % minimum calendar month average Jan-Dec Calculation 3 x Week
TSS, grab (Mercury) Monitor only mg/L calendar month maximum Jan-Dec Grab 1 x Month
Proposed permit effluent limits The effluent limits and monitoring requirements for SD 001 in the proposed permit are presented in Table 4 at the end of this section. Applicable TBELs, WQBELs, and SDRs are explained below.
Technology based effluent limits (TBELs) Total suspended solids (TSS), 5-day carbonaceous biochemical oxygen demand (CBOD5), and pH limits are technology-based limits developed for achieving secondary treatment standards. These limits are specified in 40 CFR §133.102, Minn. R. 7050.0211 and Minn. R. 7053.0215. Water quality based limits (WQBELs) The limits for total phosphorus, total residual chlorine, and total mercury are WQBELs. WQBELs are established to meet applicable water quality standards. Under 40 CFR 122.44(d)(1)(i), all dischargers who have a reasonable potential to cause or contribute to an exceedance of a water quality standard are required to have a WQBEL. WQBELs for total residual chlorine are based on Class 2B waters (Minn. R. 7050.0222). For total phosphorus, WQBELs are derived from numeric lake and river eutrophication standards (Minn. R. 7050.0222). See the ‘Total Phosphorus WQBEL’ section below for additional information regarding the development of the total phosphorus limit.
State discharge restrictions (SDRs) The limit for fecal coliform bacteria is a state discharge restriction. This limit is specified in Minn. R. 7053.0215, subp. 1. Table 3: Proposed effluent limits and monitoring requirements (SD 001)
Parameter Limit Units Limit Type Effective Period Sample Type Frequency
CBOD5 114 kg/day calendar month average Jan-Dec 24-Hour Flow Composite 3 x Week
CBOD5 182 kg/day maximum calendar week average Jan-Dec 24-Hour Flow Composite 3 x Week
CBOD5 25 mg/L calendar month average Jan-Dec 24-Hour Flow Composite 3 x Week
CBOD5 40 mg/L maximum calendar week average Jan-Dec 24-Hour Flow Composite 3 x Week
CBOD5 % Removal 85 % minimum calendar month average Jan-Dec Calculation 1 x Month
Chlorine, Total Residual 0.038 mg/L daily maximum Jan-Dec Grab 1 x Day
Copper, Total Monitor only mg/L calendar quarter maximum Mar, Jun, Sep, Dec 24-Hour Flow Composite 1 x Quarter
Fecal Coliform 200 #100ml calendar month geometric mean Apr-Oct Grab 3 x Week
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 14 of 22 Flow Monitor only mgd calendar month average Jan-Dec Measurement, Continuous 1 x Day
Flow Monitor only mgd calendar month maximum Jan-Dec Measurement, Continuous 1 x Day
Flow Monitor only MG calendar month total Jan-Dec Measurement, Continuous 1 x Day
Mercury, Dissolved Monitor only ng/L calendar month average Jan, Mar, May, Jul, Sep, Nov Grab 2 x Month
Mercury, Dissolved Monitor only ng/L daily maximum Jan, Mar, May, Jul, Sep, Nov Grab 2 x Month
Mercury, Total 10 ng/L calendar month average Jan, Mar, May, Jul, Sep, Nov Grab 2 x Month
Mercury, Total 17 ng/L daily maximum Jan, Mar, May, Jul, Sep, Nov Grab 2 x Month
Nitrite Plus Nitrate, Total Monitor only mg/L calendar month average Jan-Dec 24-Hour Flow Composite 1 x Month
Nitrogen, Ammonia, Total Monitor only mg/L calendar month average Jan-Dec 24-Hour Flow Composite 1 x Month
Nitrogen, Kjeldahl, Total Monitor only mg/L calendar month average Jan-Dec 24-Hour Flow Composite 1 x Month
Oxygen, Dissolved Monitor only mg/L calendar month minimum Jan-Dec Grab 1 x Day
pH 6.0 SU calendar month minimum Jan-Dec Grab 1 x Day
pH 9.0 SU calendar month maximum Jan-Dec Grab 1 x Day
Phosphorus, Total 2608 kg/yr 12 month moving total Jan-Dec Calculation 1 x Month
Phosphorus, Total Monitor only mg/L calendar month average Jan-Dec 24-Hour Flow Composite 1 x Week
TDS Monitor only mg/L calendar month average Jan-Dec 24-Hour Flow Composite 1 x Month
TSS 136 kg/day calendar month average Jan-Dec 24-Hour Flow Composite 3 x Week
TSS 204 kg/day maximum calendar week average Jan-Dec 24-Hour Flow Composite 3 x Week
TSS 30 mg/L calendar month average Jan-Dec 24-Hour Flow Composite 3 x Week
TSS 45 mg/L maximum calendar week average Jan-Dec 24-Hour Flow Composite 3 x Week
TSS % Removal 85 % minimum calendar month average Jan-Dec Calculation 1 x Month
TSS, grab (Mercury) Monitor only mg/L calendar month average Jan, Mar, May, Jul, Sep, Nov Grab 2 x Month
TSS, grab (Mercury) Monitor only mg/L daily maximum Jan, Mar, May, Jul, Sep, Nov Grab 2 x Month
Differences between current and proposed effluent limits and monitoring requirements
a. Change in CBOD5 percent Removal and TSS percent Removal frequency from three times per week to once per month.
b. Addition of quarterly (Mar, Jun, Sep, Dec) Copper monitoring. c. Change in Nitrite plus Nitrate and Total Kjeldahl Nitrogen monitoring frequency from once per month (Apr, Sep)
to once per month (Jan-Dec). d. Addition of Total Nitrogen monitoring at a frequency of once per month (Jan-Dec). e. Change in Total Dissolved Solids (TDS) monitoring frequency from once per month (Apr, Sep) to once per month
(Jan-Dec). f. Change in the Total Mercury limit from 6.9 ng/L (12 month moving average) to 10 ng/L (calendar month
average) and 17 ng/L (daily maximum) because the EPA will no longer accept a rolling monthly average limit for mercury.
g. Change in Total Mercury monitoring frequency from reporting calendar month average once per month (Jan-Dec) to reporting daily maximum and calendar month average with a monitoring frequency of twice per month (Jan, Mar, May, Jul, Sep, Nov).
h. Change in Dissolved Mercury and TSS (grab, mercury) monitoring frequency from reporting calendar month maximum once per month (Jan-Dec) to reporting daily maximum and calendar month average with a monitoring frequency of twice per month (Jan, Mar, May, Jul, Sep, Nov).
i. Removal of the compliance schedule for Total Phosphorus since the facility attained compliance with the final limit (2,608 kg/yr) by December 31, 2018 as required in the current permit.
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 15 of 22 Differences between current and proposed influent monitoring requirements
a. Change in Total Mercury monitoring frequency from reporting calendar month maximum once per month (Jan-Dec) to reporting calendar month average with a monitoring frequency of twice per month (Jan, Mar, May, Jul, Sep, Nov).
b. Addition of Nitrite plus Nitrate Nitrogen, Total Kjeldahl Nitrogen, and Total Nitrogen monitoring at a frequency of once per month (Jan-Dec).
Total Suspended Solids Suspended solids may include both organic and inorganic matter. The inorganic compounds may include sand, silt, clay and precipitated metals. The organic fraction may include such materials as wood fibers and unsettled biomass from biological treatment systems. These solids may settle out rapidly and bottom deposits are often a mixture of both organic and inorganic solids. Solids may be suspended in water for a time and then settle to the bed of the stream or lake. They may be inert, slowly biodegradable materials, or rapidly decomposable substances. While in suspension they increase the turbidity of the water, reduce light penetration, and impair the photosynthetic activity of aquatic plants. Suspended solids may kill fish and shellfish by causing abrasive injuries, by clogging gills and respiratory passages, by screening out light and by promoting and maintaining the development of noxious conditions through oxygen depletion. Suspended solids also reduce the recreational value of water. The outfall monthly average 30 mg/L TSS limit is more protective than the 32 mg/L reach-specific TSS standard determined for the South Metro Mississippi River (MPCA, 2015). The South Metro Mississippi River Total Suspended Solids TMDL contains a WLA for the facility; the daily mass limit of 136 kg/day is applied at SD 001 in the permit. Total Phosphorus WQBELFederal law [40 CFR §122.44(d)] restricts mass increases of pollutants upstream of an impaired water and requires WQBEL(s) to be established for pollutant parameters where it is found that a NPDES/SDS discharger has the reasonable potential (RP) to cause or contribute to an excursion above a state WQS. An effluent limits analysis was completed on the Facility to determine if the Facility’s discharge has RP to cause or contribute to an exceedance of a state WQS or contribute to any downstream impairment. As a result of the analysis in 2012, total phosphorus effluent limits were established for the Facility to ensure protection of downstream waters and to comply with Lake Eutrophication Standards. A summary of the effluent limits analysis and the assigned total phosphorus limit are included below. For additional details regarding the effluent limits analysis, please see the “Draft Lake Pepin Watershed phosphorus total maximum daily loads” which can be found at https://www.pca.state.mn.us/sites/default/files/wq-iw9-22b.pdf and “Total phosphorus effluent limit review: Mississippi River – St. Cloud Watershed”. A copy of the MPCA memorandum is available upon request.
Lake Eutrophication Standards Effluent from the Facility is discharged upstream of Lake Pepin, a reservoir on the Mississippi River, which currently exceeds numeric lake eutrophication standards. Eutrophication standards for lakes, shallow lakes, and reservoirs can be found in Minn. R. 7050.0222 (https://www.revisor.mn.gov/rules/?id=7050.0222). Federal law [40 CFR §122.44(d)] restricts mass increases upstream of impaired waters and states that NPDES/SDS permits for all dischargers that have the RP to cause or contribute to downstream impaired waters are required to contain WQBELs derived from the WQS. When determining RP, the Code of Federal Regulations also states that 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 is found to have RP for TP upstream of Lake Pepin. Therefore, the Facility is assigned a 12-month moving total mass TP WQBEL as a result of the Waste Load Allocation (WLA) derived from
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 16 of 22 the Draft Lake Pepin – Excess Nutrients TMDL. Draft WLAs in combination with other point and nonpoint allocations are calculated to achieve the draft nutrient/eutrophication criteria for Lake Pepin.
A computer reservoir model for Lake Pepin was developed by the MPCA modeling consultant, LimnoTech, to evaluate site specific eutrophication criteria and the reductions necessary to achieve these criteria (LTI 2008). Using the best available science, draft criteria for Lake Pepin were determined to be 100 µg/L for TP and 28 µg/L for chlorophyll-a (Heiskary and Wasley 2010). 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 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 MPCA staff simultaneously developed draft WLAs, compatible with scenario 17 reductions for all NPDES dischargers within the contributing watershed.
A categorical approach was used to develop individual WLAs for the draft Lake Pepin TMDL. Monticello fits into a Municipal Major (MM) category defined by municipal facilities with AWWDFs between 1 and 20 mgd. Individual MM WLAs are calculated as follows:
General Formula: MM WLA = (AWWDF x 0.8 mg/L TP x 3.785 L/gal x 365 days/yr)
Monticello WWTF WLA: 2,608 kg/yr TP = (2.36 mgd x 0.8 mg/L x 3.785 L/gal x 365 days/yr)
Given that Monticello is not expanding and does not affect a downstream lake, as defined by Minn. R. 7053.0255, it is not required by State Rules to receive a 1.0 mg/L TP limit. Nonetheless, it was determined that Monticello has RP to cause or contribute to the excess nutrient impairment in Lake Pepin and is therefore required to have a WQBEL. The recommended TP effluent limit (2,608 kg/yr) in the draft permit is a WQBEL derived from the draft WLA, which in turn is derived from the water quality standard that the receiving water must meet to support designated uses. 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.
The existing TP effluent limit assigned to the Facility in the 2012 permit reissuance to protect for eutrophication impairment in Lake Pepin remains 2,608 kg/yr as a 12-month moving total. No additional limits are needed at this time to protect for river eutrophication standards (RES) in the St. Cloud Watershed.
BackgroundonReasonablePotentialReview The Permittee has submitted five acute whole effluent toxicity (WET) tests and three priority pollutant scans during the current permit cycle. The average dry weather (ADW) design flow is used to calculate WQBELs under critical low flow stream conditions. The ADW is 1.79 mgd. The low flow condition is defined by the once in ten year weekly average flow (7Q10), which is determined to be 910 cfs (588.2 mgd). The analysis below is based on data submitted to date.
Reasonable Potential for Chemical Specific Pollutants [40 CFR § 122.44 (d)(1)]Federal regulations require the MPCA to evaluate the discharge to determine whether the discharge has the reasonable potential to cause or contribute to a violation of water quality standards. The Agency must use acceptable technical procedures, accounting for variability (coefficient of variation, or CV), when determining whether the effluent causes, has the reasonable potential to cause, or contribute to an excursion of an applicable water quality standard. Projected effluent quality (PEQ) derived from effluent monitoring data is compared to Preliminary Effluent Limits (PEL) determined from mass balance inputs. Both determinations account for effluent variability. Where PEQ exceeds the PEL, there is
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 17 of 22 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.
Table 4 contains the inputs to the reasonable potential analysis for mercury (Hg), arsenic (As), chromium 6 (measured as total chromium in the samples), copper (Cu), antimony (Sb), nickel (Ni), zinc (Zn), DEPH, chloroform, and free cyanide (Cn). The analysis is made with effluent data that is expressed as total metal. These pollutants were evaluated on the basis of analytical measurements that made evident the need for a full determination. Where PEQs exceed PELs, a WQBEL is needed.
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 18 of 22 Table 4: Reasonable Potential Analysis
Hg (ng/L) As (ug/L) Cr6 (ug/L) Cu (ug/L) Sb (ug/L)
Max Measured Value 0.802 1.4 0.92 61.5 9.1
# data points 57 3 3 3 3
PEQ 0.802 4.2 2.76 184.5 27.3
Plant flow ADW (mgd) 1.79 1.79 1.79 1.79 1.79
Rec. water flow, 7Q10(mgd) 588.235294 588.2352941 588.2352941 588.2352941 588.2352941
Background Conc. 6.9 0 2.48 0.95 0
Continuous Std (cs) 6.90 2.00 11.00 20.29 5.50
322 ppm hardness
Maximum Std (ms) 2400.00 360.00 16.00 53.35 90.00
322 ppm hardness
Final Acute Value (FAV) 4900 720 32 82 180
244 ppm hardness
Mass Balance -cs 6.90 659.25 2810.87 6376.49 1812.93
Mass Balance -ms 788827.87 118664.30 4458.98 17271.59 29666.08
Coeff of Variation (CV) 0.60 0.60 0.60 0.60 0.60
Long Term Avg-cs 5.38 514.41 1482.52 3363.12 1414.62
Long Term Avg-ms 253289.00 38102.56 1431.76 5545.83 9525.64
Preliminary Effl limits:
Daily Max 16.77 1602.04 4458.98 10473.89 4405.60
Monthly Ave (2x/month) 9.68 924.74 2573.85 6045.82 2543.03
Reasonable Potential
PEQ>Daily max FALSE FALSE FALSE FALSE FALSE
PEQ>Monthly Ave. FALSE FALSE FALSE FALSE FALSE
PEQ> FAV FALSE FALSE FALSE TRUE FALSE
Final Reasonable Potential No No No NO! No
notes
Mississippi River Class 1C, 2Bd…
Mercury background set to chronic std due to
state wide TMDL
thirty of the fifty seven mercury data pts
are less than the reporting limit
background concs. based on S000-151
NO!- Copper is rp is based on very limited data. EAO staff is going to recommend more monitoring
No Acute WET limit needed
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 19 of 22
Reasonable Potential for Priority Pollutants The priority pollutant scan information of the effluent was evaluated using reasonable potential procedures. All but Di-2- ethyl hexyl phthalate (DEPH) and 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.
The MPCA recommends sending in the entire priority pollutant report, including the Quality Check/Control (QC) section each time the priority pollutant scan is performed. The Permittee must send three priority pollutant scans in the life of the permit.
Ni (ug/L) Zn (ug/L) DEPH (ug/L) Chloroform (ugFree CN (ug/L)
Max Measured Value 1.4 45.1 14.5 25 13.3
# data points 3 3 3 3 3
PEQ 4.2 135.3 43.5 75 39.9
Plant flow ADW (mgd) 1.79 1.79 1.79 1.79 1.79
Rec. water flow, 7Q10(mgd) 588.2352941 588.2352941 588.2352941 588.2352941 588.2352941
Background Conc. 1.5 2.6 0 0 0
Continuous Std (cs) 297.00 285.51 1.90 53.00 5.20
322 ppm hardness
Maximum Std (ms) 3814.14 315.19 NA 1392.00 22.00
322 ppm hardness
Final Acute Value (FAV) 6032 498 NA 2784 45
244 ppm hardness
Mass Balance -cs 97405.12 93256.31 626.28 17470.02 1714.04
Mass Balance -ms 1256735.74 103039.67 #VALUE! 458835.31 7251.71
Coeff of Variation (CV) 0.60 0.60 0.60 0.60 0.60
Long Term Avg-cs 51373.87 49185.68 488.69 13631.76 904.03
Long Term Avg-ms 403532.07 33085.56 #VALUE! 147329.91 2328.49
Preliminary Effl limits:
Daily Max 159995.65 103039.67 1521.93 42453.94 2815.45
Monthly Ave (2x/month) 92353.98 59477.39 878.50 24505.61 1625.16
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
Mississippi River Class 1C, 2Bd…
Mercury background set to chronic std due to
state wide TMDL
thirty of the fifty seven mercury data pts
are less than the reporting limit
background concs. based on S000-151
NO!- Copper is rp is based on very limited data. EAO staff is going to recommend more monitoring
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 20 of 22 Reasonable Potential for Mercury MPCA staff re-evaluated the mercury limit for the Facility since the current 6.9 ng/L rolling monthly average is no longer permitted by Region V EPA. Effluent limits were derived from water quality standards pursuant to 40 CFR 122.44 (d)(1)(vii)(A). As such, the MPCA used the current mercury data to recalculate a daily max and a monthly average limit. Because much of the data was less than the reporting limit for mercury, MPCA had to use default statistics (CV= 0.6) to determine the new mercury WQBELs. The calculation of WQBELs are as follows:
Daily Maximum = 17 ng/L Monthly Average = 10 ng/L (based on 2 samples/month). Reasonable Potential for Copper Reasonable potential to cause or contribute to the excursion above a water quality standard has been indicated for total copper in regards to the Final Acute Value (FAV). Effluent limits were derived from water quality standards pursuant to 40 CFR 122.44 (d)(1)(vii)(A). The basis of the reasonable potential is more due to the high PEQ adjustment value since there are only three data points. The highest concentration of copper is 61 ug/L. However, at this time, the MPCA is not going to recommend a WQBEL for copper. Instead, the MPCA recommends quarterly monitoring for copper to build a better database and to give the city time to find where the high source(s) of copper might be located.
Reasonable Potential for WET The permittee has acute WET monitoring as a requirement. The permittee has acute WET testing because the ratio of the 7Q10 low flow of the receiving water compared to the facility’s ADW flow is greater than 20:1. In the previous permit cycle, all five acute toxicity tests were less than 0.9999 TUa (Toxic Unit acute), as such no reasonable potential to exceed the WET threshold value was found. Because no reasonable potential has been found, a monitoring threshold value of 0.9999 TUa has been established. The 0.9999 TUa is a threshold value, not a WET limit.
Continued annual testing is recommended at existing permit conditions for the next permit cycle. The first set of annual acute WET results is due 180 days after the permit issuance date, and annually thereafter. Additional requirements Total 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 (found on the MPCA’s Nutrient reduction strategy website at http://www.pca.state.mn.us/water/nutrient-reduction-strategy), which identifies goals and milestones for nitrogen reductions for both point and nonpoint 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. ch. 115.03. The permit includes effluent monitoring for Nitrite plus Nitrate Nitrogen, Ammonia Nitrogen, Total Kjeldahl Nitrogen, Total Nitrogen and Total Dissolved Solids at a frequency of once per month (Jan-Dec). The permit includes influent monitoring for Nitrite plus Nitrate Nitrogen, Total Kjeldahl Nitrogen, and Total Nitrogen at a frequency of once per month (Jan-Dec) for the five-year term of the permit. This additional monitoring will provide the data necessary to develop a better understanding of the total nitrogen concentrations and loadings that are 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 percent reduction in total nitrogen loads from point source
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 21 of 22 dischargers by 2025. 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 http://www.pca.state.mn.us/index.php/water/water-types-and-programs/wastewater/wastewater-permits/index.html. Pollutant minimization plans The draft permit includes requirements to submit an updated Mercury Minimization Plan (MMP). MMP The Permittee is required to submit an updated MMP to the MPCA within 180 days of permit issuance. The MMP requirements include educating users with regard to proper mercury disposal in order to prevent its introduction into the waste stream. This requirement complies with the U.S. Environmental Protection Agency’s approval of the Minnesota statewide Mercury TMDL plan. More information on the TMDL can be found on the MPCA webpage at http://www.pca.state.mn.us/wfhy9ef. Guidance for completing the MMP is available on the MPCA webpage at http://www.pca.state.mn.us/gp0rb25. This permit contains limits and requirements for mercury monitoring. Specific mercury monitoring requirements are found in the surface discharge station section of the draft permit. Those requirements include sampling for TSS via a grab sample taken at the same time as the total and dissolved mercury grab samples are taken. Compliance schedules This permit does not contain a compliance schedule. Variances This permit does not include any variances to water quality standards. 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 outlined in 40 CFR § 122.41, Minn. R. 7001.0150, and 7001.1090. 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. Antidegradation and anti-backsliding The Mississippi River (St. Cloud to Anoka) was designated an Outstanding Resource Value Water [ORVW] on November 5, 1984. The design average wet weather flow of this Facility on the date of ORVW designation is 1,200,000 gpd. 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. 7050 to 7050.0335. The permit does not propose to allow a new or increased discharge and does not trigger antidegradation.
NPDES/SDSPermitProgramFactSheet MN0020567 Permit Reissuance Page 22 of 22 Any point source discharger of sewage, industrial, or other wastes for which a NPDES permit has been issued by the agency that contains effluent limits more stringent than those that would be established by Minn. R. 7053.0215 to 7053.0265 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. The permit complies with Minn. R. 7053.0275 regarding anti-backsliding. Term of Permit The effective date of the permit and the permit expiration date will be determined at the time of issuance.
The Agency has made a preliminary determination to reissue this NPDES/SDS permit for a term of approximately five years.
