Wyoming Department of Environmental Quality Water Quality Division WYPDES (Wyoming Pollutant Discharge Elimination System) Program STATEMENT OF BASIS

Transcription

1 Wyoming Department of Environmental Quality Water Quality Division WYPDES (Wyoming Pollutant Discharge Elimination System) Program STATEMENT OF BASIS RENEWAL APPLICANT NAME: MAILING ADDRESS: FACILITY LOCATION: City of Cheyenne, Wyoming 2101 O Neil Avenue Cheyenne, WY Crow Creek Water Reclamation Facility which is located in the NWSE Section 3, Township 13N, Range 66W, Laramie County. The wastewater will be discharged to Crow Creek (class 2C), South Platte River basin. Latitude: Longitude: PERMIT NUMBER: WY This permit has been renewed in accordance with current WYPDES permitting requirements. All permit effluent limits and monitoring requirements have been updated in accordance with current WDEQ regulations and policy. This permit first appeared in public notice August 16, 2013 to September 16, Based upon a formal objection filed by U.S. E.P.A., and other comments received during the public notice period, the following changes have been included in this permit: 1. The monitoring frequencies in the Industrial Pretreatment Requirements of this permit have been increased and are based upon the design flow of 6.5 MGD. Per EPA directives, facilities that are major dischargers with a design flow of 5.0 to 15.0 MGD and have an approved program are required to sample more frequently. See Part III, Section B of the permit for more information. 2. A selenium limit and compliance schedule has been implemented in this permit. It requires that selenium limits shall become effective on September 1, The facility will be required to submit quarterly reports delineating the progress made during the previous three months, in preparation to be in compliance with the selenium limits on the day the limits become effective. Monthly monitoring will be required for the entire permit term, and the limit for selenium, total recoverable, will be 5 µg/l on September 1, This is the same date that selenium limits become effective for permit number WY , Frontier Refinery, which is believed to be the actual source of the selenium in Crow Creek. Statement-of-Basis Page 1

2 3. Copper, cadmium, and lead limits, as well as a compliance schedule, have all been implemented in this permit. It is required that copper, cadmium, and lead limits shall become effective on November 1, The facility will be required to submit quarterly reports, delineating the progress made during the previous three months, in preparation to be in compliance with the copper, cadmium, and lead limits on the day the limits become effective. Monthly monitoring will be required for the entire permit term for copper, cadmium, and lead (all in dissolved); and the final effluent limits for copper will be µg/l, monthly average, in the summer and µg/l, monthly average, in the winter; for cadmium the limits will be 0.51 µg/l, monthly average, in the summer and 0.54 µg/l, monthly average, in the winter; for lead, the limits will be 6.83 µg/l, monthly average, in the summer and 7.17 µg/l, monthly average, in the winter. Because all of these metals are hardness based, monthly downstream hardness in mg/l, as CaCO 3, will be required in reporting. 4. A wasteload allocation is implemented in this revised permit for total residual chlorine and total ammonia as N. 5. WET testing requirements have been adjusted for available dilution in Crow Creek (class 2C). 6. The pretreatment requirements in Part III, Section B require the facility to submit the pretreatment annual reports to the WDEQ/WQD as well as to EPA, Region 8. This is also being listed under the reporting requirements in Part I, Section B of the permit. A. FACILITY DESCRIPTION: The Cheyenne Board of Public Utilities operates this wastewater treatment facility (WWTF) for the City of Cheyenne. This is one of two facilities that service the Cheyenne area. The facility consists of in-plant pumping, course screening, grit removal, and primary clarification. The wastewater then flows through two Moving Bed Biofilm Reactors (MBBR) that run in parallel, followed by oxic tanks, final clarification, UV disinfection, and then final discharge. All or part of the influent to this facility can be diverted to the Dry Creek Water Reclamation Facility (WYPDES Permit Number WY ). The sludge from this wastewater facility is pumped into an interceptor sewer, along with flushing water, and is sent to the Dry Creek Water Reclamation Facility for further treatment, removal, and final disposal. This facility has a tertiary treatment segment that consists of sand filtration and sodium hypochlorite disinfection. A portion of the effluent (before discharge to Crow Creek) is diverted through this treatment area and is utilized as irrigation water for a portion of Cheyenne s parks, ball fields, and schools. The WWTF has a design flow of 6.5 million gallons per day (MGD). This system receives wastewater from a population of approximately 21,527 residents from the Cheyenne metropolitan area and includes collection from the F.E. Warren Air Force Base serving a population of 3,072. The average monthly flows are MGD. The discharge from the plant (outfall 001) flows to Crow Creek (class 2C water), South Platte River basin. The permit establishes effluent limits for the end of pipe, which are protective of all the designated uses defined in Chapter 1 of Wyoming Water Quality Rules and Regulations. This may include drinking water, game and non-game fish, fish consumption, aquatic life other than fish, recreation, agriculture, wildlife, industry and scenic value. Statement-of-Basis Page 2

3 Outfall Location Information This facility discharges to a pipe that carries the treated effluent a very short distance before discharge into Crow Creek. The latitude, longitude, and location listed in this permit are at the physical discharge on Crow Creek. B. EFFLUENT LIMITS AND MONITORING REQUIREMENTS: Permit effluent limits are based on federal and state regulations and are effective as of the date of issuance. The permit limits are technology based limits and water quality based limits as described below. 1. Technology based limits: The permit requires immediate compliance with National Secondary Treatment Standards (NSTS), Wyoming Water Quality Standards, and the effluent limits that are established by this permit. a. The five-day carbonaceous biochemical oxygen demand (CBOD 5 ) concentration shall not exceed 25 mg/l (monthly average) or 40 mg/l (weekly average) or 80 mg/l (daily maximum) and the percent reduction shall not be less than 85%. These limits are based upon NSTS for CBOD 5. i. EPA allows a nitrification inhibitor to be used in the BOD 5 testing procedure that effectively removes the nitrogenous oxygen demand and leaves only the carbonaceous portion of the BOD 5 to be measured as long as carbonaceous permit limits, which are more stringent, are used in the permit. For this reason the permit includes the more stringent CBOD 5 limits. b. The total suspended solids (TSS) concentration shall not exceed 30 mg/l (monthly average) or 45 mg/l (weekly average) or 90 mg/l (daily maximum) and the percent reduction of TSS shall not be less than 85%. These limits are based upon NSTS. 2. Water quality based limits: Water quality based limits are set to ensure that the quality of the receiving water is protected. Expected contaminants in this municipal wastewater include E. coli, total ammonia, total residual chlorine, selenium, copper, cadmium, and lead. a. The permit requires that the ph must remain within 6.5 and 9.0 standard units (SU). The ph limit is based on water quality standards established in the Wyoming Water Quality Rules and Regulations, Chapter 1. b. Mixing zone: This permit sets water quality based effluent limits so that mixing zone requirements, per Chapter 1, Section 9, Wyoming Water Quality Rules and Regulations are met. Mixing zone requirements ensure that a minimal area of the water body is impacted by the discharge during mixing of the discharge and receiving water. Per The Wyoming Water Quality Implementation Policies for Mixing Zones, this facility is considered complete mix because the mean daily flow of the discharge exceeds the critical low instream flow. c. Wasteload allocation: Because Crow Creek has a perennial flow at the point of discharge; a wasteload allocation calculation was performed to determine the effluent limits for ammonia, residual chlorine, copper, cadmium, and lead, which take into account dilution provided by the receiving water. This involves a mass balance approach to determine the maximum allowable concentration in the effluent at the end-of-pipe, so that when mixed with the receiving stream, the in-stream standard of the constituent is not violated. The wasteload allocation, with the mass balance approach, utilizes 1) the upstream flow of the receiving stream, 2) the upstream concentration of the constituent 3) the maximum monthly average design discharge volume, and 4) the instream standard concentration, to calculate the 5) maximum allowable concentration of the constituent in the effluent. Also refer to Tables A and B in the Statement-of-Basis, for wasteload allocation information. Statement-of-Basis Page 3

4 d. Critical Low Flows: The low flow conditions can be determined by applying the 7Q10 (the minimum seven consecutive day flow that has the probability of occurring once in ten years) of the receiving water body. Using the 7Q10 values to establish the effluent limits will provide a margin of safety because worse case flow conditions are assumed. The effluent limits shown below are based on flow data from the USGS gauging station number (Crow Creek at 19 th Street, Cheyenne, WY). The period of record for this station is from 1993 to present day. U.S.G.S. Station Number Station Name Period of Flow Records Crow Creek at 19 th Street Cheyenne, WY May- September season 7Q10 Value, cfs October- April season 7Q10 Value, cfs 1993 to current Background Water Quality: The background water quality on Crow Creek (class 2C) is listed below. The values shaded and in bold are the values used in calculating effluent limits for this permit: Background Instream Concentration Constituent April- September season October- March season May- September season October- April season Number of Observations Ammonia, average, mg/l 1 N/A N/A Period of Record Chlorine, mg/l Copper, average, µg/l 1 N/A N/A Cadmium, average, µg/l 1 N/A N/A 0 0 Lead, average, µg/l 1 N/A N/A 0 0 Default is Zero Background N/A Hargett, Eric, WDEQ/WQD, Water Quality Condition and Designated Use Determination for Crow Creek, South Platte Basin, , 2009, WEB, 21, November, Statement-of-Basis Page 4

5 e. THE MAXIMUM MONTHLY AVERAGE DESIGN DISCHARGE VOLUME The average daily flow from this facility is MGD, with a design flow of up to 6.5 MGD. Because the design flow is used in the wasteload allocation equation, the permit also includes a flow limit of 6.5 MGD, monthly average. A summary of the mixing zone compliance specific to this permit is as follows: i. Total Residual Chlorine: calculated limits from waste load allocation using critical low stream flows above. ii. Total Ammonia: calculated limits from a waste load allocation using critical low stream flows above. iii. E. coli: set to instream standards due to impairment in Crow Creek. iv. Selenium: set to load allocation as determined in the Crow Creek TMDL (effluent limits effective September 1, 2015). v. Copper: calculated effluent limits from a waste load allocation using critical low stream flows above (effluent limits effective November 1, 2017). vi. Cadmium: calculated effluent limits from a waste load allocation using critical low stream flows above (effluent limits effective November 1, 2017). vii. Lead: calculated effluent limits from a waste load allocation using critical low stream flows above (effluent limits effective November 1, 2017). f. TABLES INDICATING WATER QUALITY BASED EFFLUENT LIMITS i. Effluent Limits For Total Residual Chlorine: The chronic instream standard for total residual chlorine is mg/l, and the acute instream standard is mg/l. The calculated effluent limits for total residual chlorine in the permit are listed in the table below. TOTAL RESIDUAL CHLORINE LIMITS* Season Maximum Effluent Discharge (MGD) Limit, Total Residual Chlorine, chronic (mg/l) Limit, Total Residual Chlorine, acute (mg/l) May-Sept Oct-April *Values shaded and in bold are the effluent limits applied in this permit. ii. Effluent Limits for Ammonia: Because of the low stream flow to facility discharge ratio, instream standards for ammonia are based on the ph and maximum temperature ( o C) of the discharge stream only, as collected and reported on monthly discharge monitoring reports (DMR). The calculated effluent limits for ammonia in the permit are listed in the table below. Statement-of-Basis Page 5

6 AMMONIA LIMITS* Season Maximum Effluent Discharge (MGD) Facility ph (median) Facility Temp ( o C) (maximum) Limit, Chronic Ammonia (mg/l) Limit, Acute Ammonia (mg/l) May- Sept Oct- April * Values shaded and in bold are the effluent limits applied in this permit. iii. Effluent Limits For E. coli: E. coli bacteria conditions reflect a primary contact recreation E. coli standard established in the Wyoming Water Quality Rules and Regulations, Chapter 1 as 126 colonies/100 ml monthly geometric mean limit during the months May 1 through September 30 (summer recreation season), with a 235 colonies/100 ml daily maximum for the same period. Crow Creek is an Infrequently Used Full Body Contact water, per Chapter 1, because this water, based on professional judgment, is an infrequently used recreational area. However, Crow Creek is impaired for E. coli from Hereford Reservoir #1 upstream to 0.7 miles below Morrie Avenue. Because of this, the facility effluent limits are set to the instream standards for E. coli which includes a 235 colonies/100 mls., daily maximum, during the summer recreation season. During the October 1-April 30 season (winter recreation season), the E. coli limit is based on the monthly average standard for secondary contact recreation of 630 colonies/100 ml. This standard applies for both the monthly geometric mean limit and the daily maximum limit. These limits are based on Water Quality Criteria as established in Wyoming Water Quality Rules and Regulations, Chapter 1. See the table(s) below for more information. E. coli Limits* Season Instream Standard Design Effluent Discharge (MGD) Instream Standard and Limit, E. coli, monthly avg. (colonies/100 ml) Instream Standard and Limit, E. coli, daily max. (colonies/100 ml) May-Sept Oct-April *Values shaded and in bold are the effluent limits applied in this permit. Statement-of-Basis Page 6

7 E. coli Bacteria Standards, In Waters Designated for Primary Contact Recreation Monthly Average Standard 126 colonies/100 ml April through September Daily Maximum Criteria Standards 235 colonies/100 High Use Swimming Areas ml 298 colonies/100 Moderate Full Body Contact ml 410 colonies/100 Lightly Used Full Body Contact ml 576 colonies/100 Infrequently Used Full Body ml Contact October through March Monthly Average and Daily Maximum 630 colonies/100 ml iv. Effluent Limits for Selenium, Total Recoverable: Crow Creek is impaired for selenium and a TMDL was completed for the impaired section of Crow Creek. Because selenium limits for other permits in the locale affected by the TMDL become effective on September 1, 2015, final selenium effluent limits are effective September 1, 2015 for this permit as well. Interim monitoring from the issuance date of the permit through August 31, 2015, and compliance schedule requirements, are included in the permit. The TMDL for selenium on Crow Creek allocates the amount of selenium any point source is allowed to discharge in the affected stream reach. The amount the TMDL allocated the Crow Creek facility is equivalent to instream standards (5 µg/l). Because the allocated load for this facility is restricted to the instream standard, the final effluent limit for selenium was not calculated with a waste load allocation. Compliance Schedule: From the effective date of this permit through August 31, 2015, quarterly reports are to be submitted delineating the progress being made to come into compliance with final selenium limits. See Part I, Section D.1 in the permit for more information. Season SELENIUM, TOTAL RECOVERABLE* Maximum Effluent Discharge (MGD) Jan-Dec Instream Standard and Limit, Selenium, Total Recoverable, chronic (µg/l), Daily maximum (Effective September 1, 2015) *Values shaded and in bold are the final effluent limits for selenium included in this permit. Statement-of-Basis Page 7

8 v. Effluent Limits for Copper, Dissolved: Based upon data submitted in upfront analysis with the application for renewal to WDEQ, and based upon effluent monitoring reports submitted to EPA, Region 8, the discharge shows a reasonable potential to include copper in amounts above instream standards as established in Wyoming Water Quality Rules and Regulations, Chapter 1. Therefore interim monitoring requirements for copper, final effluent limits for copper, and a compliance schedule, are included in the permit. There are no interim limits for copper; however monthly monitoring is required during the interim period. Final effluent limits for copper become effective November 1, This allows the facility a window of opportunity to determine the source of copper in the facility discharge, and to determine and implement the most feasible way to come into compliance when the limits do become effective. This water quality based effluent limit is calculated from a waste load allocation (see Table B on page 12 of the Statement-of-Basis). Compliance Schedule: From the effective date of this permit issuance through October 31, 2017, quarterly reports are to be submitted delineating the progress being made to come into compliance with final copper limits. See Part I, Section E.1 in the permit for more information. COPPER, DISSOLVED* Season Maximum Effluent Discharge (MGD) Limit, Copper, Dissolved, chronic (µg/l), Monthly Average (Effective November 1, 2017) May-Sept Oct-April *Values shaded and in bold are the final effluent limits for copper included in this permit. vi. Effluent Limits for Cadmium, Dissolved: Based upon data submitted to EPA, Region 8, the discharge shows a reasonable potential to include cadmium in amounts above instream standards as established in Wyoming Water Quality Rules and Regulations, Chapter 1. Therefore interim monitoring requirements for cadmium, final effluent limits for cadmium, and a compliance schedule, are included in the permit. There are no interim limits for cadmium; however monthly monitoring is required during the interim period. Final effluent limits for cadmium become effective November 1, This allows the facility a window of opportunity to determine the source of cadmium in the facility discharge, and to determine and implement the most feasible way to come into compliance when the limits do become effective. This water quality based effluent limit is calculated from a waste load allocation (see Table B on page 12 of the Statement-of-Basis). Statement-of-Basis Page 8

9 Compliance Schedule: From the effective date of this permit issuance through October 31, 2017, quarterly reports are to be submitted delineating the progress being made to come into compliance with final cadmium limits. See Part I, Section E.1 in the permit for more information. CADMIUM, DISSOLVED* Season Maximum Effluent Discharge (MGD) Limit, Cadmium, Dissolved, chronic (µg/l), Monthy Average (Effective November 1, 2017) May-Sept Oct-April *Values shaded and in bold are the final effluent limits for cadmium included in this permit. vii. Effluent Limits for Lead, Dissolved: Based upon data submitted in upfront analysis supplied with the application for renewal to WDEQ, and based upon effluent monitoring reports submitted to EPA, Region 8, the discharge shows a reasonable potential to include lead in amounts above instream standards as established in Wyoming Water Quality Rules and Regulations, Chapter 1. Therefore interim monitoring requirements for lead, final effluent limits for lead, and a compliance schedule, are included in the permit. There are no interim limits for lead; however monthly monitoring is required during the interim period. Final effluent limits for lead become effective November 1, This allows the facility a window of opportunity to determine the source of lead in the facility discharge, and to determine and implement the most feasible way to come into compliance when the limits become effective. This water quality based effluent limit is calculated from a waste load allocation (see Table B on page 12 of the Statement-of-Basis). Compliance Schedule: From the effective date of this permit issuance through October 31, 2017, quarterly reports are to be submitted delineating the progress being made to come into compliance with final lead limits. See Part I, Section E.1 in the permit for more information. LEAD, DISSOLVED* Season Maximum Effluent Discharge (MGD) Limit, Lead, Dissolved, chronic (µg/l), Monthly Average (Effective November 1, 2017) May-Sept Oct-April *Values shaded and in bold are the final effluent limits for lead included in this permit. Statement-of-Basis Page 9

10 3. EXPLANATION OF REASONABLE POTENTIAL ANALYSIS: The reasonable potential analysis was calculated for the additional contaminants of concern. Based on a review of upfront water quality data submitted with the application renewal and from the industrial pretreatment annual reports submitted to EPA, Region 8, these constituents are copper, cadmium, and lead. When conducting reasonable potential analysis, a Mass-Balance Equation is solved for Cr; the resultant in-stream pollutant concentration in mg/l (or in µg/l) that is present based upon previous data collected. The Mass-Balance Equation for reasonable potential analysis is as follows: Cr = (Qd)(Cd) + (Qs)(Cs) Qr Where: Qs = critical stream flow in MGD or cfs above point of discharge Cs = critical background in stream pollutant concentration Qd = critical effluent flow in MGD or cfs Cd = critical effluent pollutant concentration in mg/l (or µg/l) Qr = resultant in stream flow, after discharge in MGD or cfs Cr = resultant in stream pollutant concentration in mg/l (or µg/l) Based on the data evaluated, the highest reasonable potential for dissolved copper in-stream pollutant concentration is µg/l. For the dissolved cadmium evaluation, the highest reasonable potential in-stream pollutant concentration is µg/l; and for the dissolved lead evaluation, the highest reasonable potential in-stream pollutant concentration is µg/l. These constitute levels that are higher than in-stream standards allow based upon Chapter 1, Wyoming Water Quality Rules and Regulations. The standards used in the waste load allocation (TABLE B in the Statement-of-Basis) are adjusted for hardness as CaCO 3 in mg/l. 4. EXPLANATION OF HARDNESS BASED METALS (COPPER, CADMIUM, AND LEAD): The toxicity of copper, cadmium, and lead on aquatic life varies with hardness and the standard applied to the limits for copper, cadmium, and lead must be calculated based upon the hardness as CaCO 3 of the receiving stream after mixing. The water quality standards for cadmium, copper, and lead final effluent limits in this permit were calculated based upon an in-stream hardness of 250 mg/l. Statement-of-Basis Page 10

11 HARDNESS* DEPENDENT METALS - DISSOLVED VALUES Enter Hardness value (mg/l) here: 250 For Hardness values greater than 400 mg/l, use 400. Chronic Value (ug/l) CADMIUM 0.5 COPPER 19.6 LEAD 6.7 Chronic value= 4-day average concentration HARDNESS DEPENDENT CONVERSION FACTORS Cadmium Acute Cadmium Chronic Lead Acute & Chronic *Hargett, Eric, WDEQ/WQD, Water Quality Condition and Designated Use Determination for Crow Creek, , 2009, WEB, 21, November, The 250 mg/l hardness is from data downstream of the Crow Creek Reclamation Facility Discharge. 5. PERCENT REMOVAL REQUIREMENTS: The arithmetic mean of the CBOD and TSS concentration for effluent samples collected in a period of 30- day average shall demonstrate a minimum of eight-five percent (85%) removal of CBOD and TSS, as measured by dividing the respective differences between the mean influent (prior to treatment of the stabilization ponds) and effluent concentrations for the calendar month (30-day average) by the respective mean influent concentration for the calendar month (30-day average), and multiplying the quotient by 100. See the below equation for clarification: Percent Removal: Statement-of-Basis Page 11

12 Wasteload Allocation (WLA) Calculations Facility: City of Cheyenne, WY (Crow Creek Water Reclamation Facility) TABLE A Waste Load Allocation Calculation 100% dilution allowed Permit Number: WY Wasteload Allocation Formula: Cd = (QrCr - QsCs)/Qd Season Parameter Q s Q d Q r C r C s C d Low Flow, cfs Low Flow, MGD Discharge Rate, Combined Water Quality Background (7Q10) (7Q10) MGD Flow, MGD Standard Con. (LA) Limit (WLA) * May - Sept TRC, chronic Oct - April TRC, chronic May - Sept TRC, acute Oct - April TRC, acute May - Sept Ammonia, chronic Oct - April Ammonia, chronic May - Sept Ammonia, acute Oct - April Ammonia, acute *All units are mg/l, unless otherwise specified. Effluent Limits Are Shaded, In Bold Statement-of-Basis Page 11

13 Wasteload Allocation (WLA) Calculations TABLE B Waste Load Allocation Calculation 100% dilution allowed Facility: City of Cheyenne, WY (Crow Creek Water Reclamation Facility) Standards used in this waste load allocation are based upon Permit Number: WY a hardness of 250 mg/l Wasteload Allocation Formula: Cd = (QrCr - QsCs)/Qd Season Parameter Q s Q d Q r C r C s C d Low Flow, cfs Low Flow, MGD Discharge Rate, Combined Water Quality Background (7Q10) (7Q10) MGD Flow, MGD Standard Con. (LA) Limit (WLA) * May - Sept Copper, chronic Oct - April Copper, chronic May - Sept Cadmium, chronic Oct - April Cadmium, chronic May - Sept Lead, chronic Oct - April Lead, chronic *All units are µg/l, unless otherwise specified. Effluent Limits Are Shaded, In Bold Statement-of-Basis Page 13

14 6. ANTIDEGRADATION/IMPAIRMENT REVIEW: The discharge of wastewater and the effluent limits that are established in this permit have been reviewed to ensure that the levels of water quality necessary to protect the designated uses of the receiving waters are maintained and protected. An antidegradation review has been conducted and verifies that the permit conditions, including the effluent limitations established, provide a level of protection to the receiving water consistent with the antidegradation provisions of Wyoming surface water quality standards. An evaluation has been completed that shows that the receiving water has been listed on the 303(d) list as a water body that cannot support designated uses. Crow Creek (class 2C) is impaired for selenium, E.coli, and sediment. Effluent limits for E. coli and selenium have been applied at the most stringent in stream standards in order to assure that this facility does not contribute to the impairment. This facility is not considered to be a contributor to the sediment impairment so the limits remain the same as in previous permits. 7. WHOLE EFFLUENT TOXICITY (WET) TESTING AND LIMITS: Because the (calculated) dilution factor at this facility is less than 100:1, the permittee must pass chronic toxicity criteria for two species based upon Chapter 2 Wyoming Water Quality Rules and Regulations. In the chronic test the test organisms are exposed for a longer period of time and the effects on growth (fathead minnows) and reproduction (Ceriodaphnia) are measured. However, with the chronic test, pass or failure is determined under low stream flow dilution condition. In this case the low stream flow dilution is 98% effluent 1, so the chronic test criteria must be met in a test solution containing 98% effluent and 2% control water during the summer recreation season (May through September) and 93% effluent and 6% control water during the winter recreation season (October through April). Control water may be either water from the receiving stream or laboratory control water. Chronic testing and reporting is required quarterly. 1 The calculation for the low stream flow and effluent dilution for WET test is as follows: 6.50 MGD / (0.12 MGD stream low flow available for dilution MGD design flow) The above division equals 6.50 MGD/6.62 MGD design flow + low stream flow = Converting to a percentage = 98.19% effluent (May through September) (98%). For the winter season (October through April) 6.50 MGD/ (0.46 MGD stream low flow MGD design flow) The above division equals 6.50 MGD/6.96 MGD = % effluent (93%). During the previous permit monitoring schedule, the permittee requested WET testing for one species (Ceriodaphnia or Fathead Minnows) on an alternating basis. As per Part I, Section B.3. of the previous permit, the DEQ granted the permittee s request because of five consecutive passing WET test results of both species. With this permit issuance, the permittee will be required to test on both species per quarter. With five consecutive passing chronic WET tests, the permittee may again request testing for one species on an alternating basis. See Part I, Section F of the permit for more information. Statement-of-Basis Page 14

15 8. DOWNSTREAM MONITORING POINT (DMP1): A downstream monitoring point is included in this permit. Monthly monitoring is required at DMP1 for hardness, mg/l as CaCO 3, ph, and temperature in degrees Celsius. Reporting is required monthly. This is not to be considered a compliance point, but rather a location to collect data used to set future permit limits. See Part I, Section G.9 of the permit for the location of DMP1. 9. INDUSTRIAL PRETREATMENT PROVISIONS: This permit also contains the industrial pretreatment requirements of the U.S. Environmental Protection Agency. Those requirements are intended to ensure that industrial discharges to the plant do not cause an upset of the system or violation of the effluent limits that are established in the permit. See Part III, Section B of the permit for more information. 10. MAJOR DISCHARGE: This facility is classified as a major discharger per the U.S. Environmental Protection Agency. The permit will be submitted to the U.S. Environmental Protection Agency, Region 8 for review. This permit renewal shall become effective upon date of issuance. Self monitoring of effluent quality and quantity is required on a regular basis with reporting of results monthly. The permit is scheduled to expire on October 31, Marcia Porter Water Quality Division Department of Environmental Quality Drafted: August 5, 2013 Revised: December 2, 2013 Revised: January 14, 2014 Statement-of-Basis Page 15

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17 PART I A. EFFLUENT LIMITATIONS (FIRST AND SECOND INTERIM EFFLUENT LIMITS AND FINAL EFFLUENT LIMITS) - SEE ANY ADDITIONAL REQUIREMENTS UNDER PART III of the permit Parameter Effective immediately and lasting through August 31, 2015, the quality of effluent discharged by the permittee shall, at a minimum, meet the limitations set forth below. The permittee is authorized to discharge from outfall serial number(s) 001: 1. FIRST INTERIM (effective immediately) EFFLUENT LIMITS: Such discharges shall be limited as specified below: Effluent Limitations Monthly Average (b) Weekly Average (b) Daily Maximum (a) (b) Flow, MGD 6.50 N/A N/A E. coli, MPN colonies/100 ml, May- September E. coli, MPN colonies/100 ml, October- April Carbonaceous Biochemical Oxygen Demand (CBOD), mg/l 126 N/A N/A Total Suspended Solids, mg/l Total Residual Chlorine (mg/l), January- December N/A N/A 0.01* Ammonia as N (mg/l), May-September 2.81 N/A Ammonia as N (mg/l), October-April 3.56 N/A ph, s.u. (c) N/A N/A Carbonaceous Biochemical Oxygen Demand (CBOD), % Removal (d) Total Suspended Solids (TSS), % Removal (d) WET, Chronic, IC 25 at 98% effluent, May- September 85 N/A N/A 85 N/A N/A N/A N/A Pass WET, Chronic, IC 25 at 93% effluent, October-April N/A N/A Pass *The detection limit for most total residual chlorine test methods is greater than the 0.01 mg/l effluent limit. Any test resulting in a non-detect will be considered to be compliance with this limit. Page 2

18 (a) (b) (c) (d) Any single analysis and/or measurement beyond this limitation shall be considered a violation of the conditions of this permit. Monthly Average, Weekly Average and Daily Maximum are defined in Part I.G.3. The ph shall not be less than 6.5 standard units nor greater than 9.0 standard units in any single grab sample. Compliance with percent removal requirements is based on 30-day average sampling. More frequent sampling is optional. The arithmetic mean of the CBOD and TSS concentration for effluent samples collected in a period of 30-day average shall demonstrate a minimum of eighty-five percent (85%) removal of CBOD and TSS, as measured by dividing the respective differences between the mean influent and effluent concentrations for the calendar month by the respective mean influent concentration for the 30-day average, and multiplying the quotient by 100. Samples taken to determine compliance with the effluent limitations specified above shall be taken at the outfall from the final treatment unit and prior to admixture with diluent waters or the receiving stream. There shall be no discharge of floating solids or visible foam in other than trace amounts, nor shall the discharge cause formation of a visible sheen or visible hydrocarbon deposits on the bottom or shoreline of the receiving water. All waters shall be discharged in a manner to prevent erosion, scouring, or damage to stream banks, stream beds, ditches, or other waters of the state at the point of discharge. In addition, there shall be no deposition of substances in quantities which could result in significant aesthetic degradation, or degradation of habitat for aquatic life, plant life or wildlife; or which could adversely affect public water supplies or those intended for agricultural or industrial use. 2. Effective September 1, 2015 and lasting through October 31, 2017, the quality of effluent discharged by the permittee shall, at a minimum, meet the limitations set forth below. The permittee shall be authorized to discharge from outfall serial number(s) 001: SECOND INTERIM (effective September 1, 2015) EFFLUENT LIMITS: Such discharges shall be limited as specified below. Page 3

19 Parameter Effluent Limitations Monthly Average (b) Weekly Average (b) Daily Maximum (a) (b) Flow, MGD 6.50 N/A N/A E. coli, MPN colonies/100 ml, May- September 126 N/A 235 E. coli, MPN colonies/100 ml, October-April 630 N/A 630 Carbonaceous Biochemical Oxygen Demand (CBOD), mg/l Total Suspended Solids, mg/l Total Residual Chlorine (mg/l), January- December N/A N/A 0.01* Total Ammonia as N (mg/l), May-September 2.81 N/A Total Ammonia as N (mg/l), October-April 3.56 N/A ph, s.u. (c) N/A N/A Carbonaceous Biochemical Oxygen Demand (CBOD), % Removal (d) Total Suspended Solids (TSS), % Removal (d) 85 N/A N/A 85 N/A N/A Selenium, Total Recoverable, µg/l N/A N/A 5.0 WET, Chronic, IC 25 at 98% effluent, May- September N/A N/A Pass WET, Chronic, IC 25 at 93% effluent, October- April N/A N/A Pass *The detection limit for most total residual chlorine test methods is greater than the 0.01 mg/l effluent limit. Any test resulting in a non-detect will be considered to be compliance with this limit. (a) (b) (c) Any single analysis and/or measurement beyond this limitation shall be considered a violation of the conditions of this permit. Monthly Average, Weekly Average and Daily Maximum are defined in Part I.G.3. The ph shall not be less than 6.5 standard units nor greater than 9.0 standard units in any single grab sample. Page 4

20 (d) Compliance with percent removal requirements is based on 30-day average sampling. More frequent sampling is optional. The arithmetic mean of the CBOD and TSS concentration for effluent samples collected in a period of 30-day average shall demonstrate a minimum of eighty-five percent (85%) removal of CBOD and TSS, as measured by dividing the respective differences between the mean influent and effluent concentrations for the calendar month by the respective mean influent concentration for the 30-day average, and multiplying the quotient by 100. Samples taken to determine compliance with the effluent limitations specified above shall be taken at the outfall from the final treatment unit and prior to admixture with diluent waters or the receiving stream. There shall be no discharge of floating solids or visible foam in other than trace amounts, nor shall the discharge cause formation of a visible sheen or visible hydrocarbon deposits on the bottom or shoreline of the receiving water. All waters shall be discharged in a manner to prevent erosion, scouring, or damage to stream banks, stream beds, ditches, or other waters of the state at the point of discharge. In addition, there shall be no deposition of substances in quantities which could result in significant aesthetic degradation, or degradation of habitat for aquatic life, plant life or wildlife; or which could adversely affect public water supplies or those intended for agricultural or industrial use. 3. Effective November 1, 2017 and lasting through October 31, 2018, the quality of effluent discharged by the permittee shall, at a minimum, meet the limitations set forth below. The permittee shall be authorized to discharge from outfall serial number(s) 001: FINAL (effective November 1, 2017) EFFLUENT LIMITS: Such discharges shall be limited as specified below. Page 5

21 Parameter Effluent Limitations Monthly Average (b) Weekly Average (b) Daily Maximum (a) (b) Flow, MGD 6.50 N/A N/A E. coli, MPN colonies/100 ml, May- September E. coli, MPN colonies/100 ml, October- April Carbonaceous Biochemical Oxygen Demand (CBOD), mg/l 126 N/A N/A Total Suspended Solids, mg/l Total Residual Chlorine (mg/l), January- December N/A N/A 0.01* Ammonia as N (mg/l), May-September 2.81 N/A Ammonia as N (mg/l), October-April 3.56 N/A ph, s.u. (c) N/A N/A Carbonaceous Biochemical Oxygen Demand (CBOD), % Removal (d) Total Suspended Solids (TSS), % Removal (d) 85 N/A N/A 85 N/A N/A Selenium, Total Recoverable, µg/l N/A N/A 5.0 Copper, Dissolved, µg/l, May - September N/A N/A Copper, Dissolved, µg/l, October - April N/A N/A Cadmium, Dissolved, µg/l, May- September 0.51 N/A N/A Cadmium, Dissolved, µg/l, October-April 0.54 N/A N/A Lead, Dissolved, µg/l, May-September 6.83 N/A N/A Lead, Dissolved, µg/l, October-April 7.17 N/A N/A WET, Chronic, IC 25 at 98% effluent, May- September WET, Chronic, IC 25 at 93% effluent, October-April N/A N/A Pass N/A N/A Pass Page 6

22 *The detection limit for most total residual chlorine test methods is greater than the 0.01 mg/l effluent limit. Any test resulting in a non-detect will be considered to be compliance with this limit. (a) (b) (c) (d) Any single analysis and/or measurement beyond this limitation shall be considered a violation of the conditions of this permit. Monthly Average, Weekly Average and Daily Maximum are defined in Part I.G.3. The ph shall not be less than 6.5 standard units nor greater than 9.0 standard units in any single grab sample. Compliance with percent removal requirements is based on 30-day average sampling. More frequent sampling is optional. The arithmetic mean of the CBOD and TSS concentration for effluent samples collected in a period of 30-day average shall demonstrate a minimum of eighty-five percent (85%) removal of CBOD and TSS, as measured by dividing the respective differences between the mean influent and effluent concentrations for the calendar month by the respective mean influent concentration for the 30-day average, and multiplying the quotient by 100. Samples taken to determine compliance with the effluent limitations specified above shall be taken at the outfall from the final treatment unit and prior to admixture with diluent waters or the receiving stream. There shall be no discharge of floating solids or visible foam in other than trace amounts, nor shall the discharge cause formation of a visible sheen or visible hydrocarbon deposits on the bottom or shoreline of the receiving water. All waters shall be discharged in a manner to prevent erosion, scouring, or damage to stream banks, stream beds, ditches, or other waters of the state at the point of discharge. In addition, there shall be no deposition of substances in quantities which could result in significant aesthetic degradation, or degradation of habitat for aquatic life, plant life or wildlife; or which could adversely affect public water supplies or those intended for agricultural or industrial use. B. SELF-MONITORING REQUIREMENTS 1. Effective immediately and lasting through October 31, 2018, the permittee shall monitor this discharge(s) as shown below: Page 7

23 Parameter Frequency (a) Sample Type (b) Total Residual Chlorine, mg/l (d) Daily Grab Flow, MGD Monthly Report 30 Day Average Flow, MGD Monthly Report Daily Maximum for the Reporting Month E. coli, MPN colonies/100 ml Twice Weekly (c) Grab CBOD, mg/l, influent Twice Weekly Composite CBOD, mg/l, effluent Twice Weekly Composite CBOD, % Removal Monthly Calculate 30 day Average TSS, mg/l, influent Twice Weekly Composite TSS, mg/l, effluent Twice Weekly Composite TSS, mg/l, % Removal Monthly Calculate 30 day Average Ammonia, mg/l Twice Weekly Composite ph, units Twice Weekly Grab Temperature, o C Twice Weekly Grab Selenium, Total Recoverable, µg/l Monthly Composite Copper, Dissolved, µg/l Monthly Composite Cadmium, Dissolved, µg/l Monthly Composite Lead, Dissolved, µg/l Monthly Composite *WET, chronic Quarterly Composite Annual Pretreatment Report Annually Submit Copy of Report to WDEQ at Address Listed in Part G of the Permit *Submit WET results on the DMR; submit hardcopies of the actual laboratory report to WDEQ, Cheyenne, quarterly. Samples taken in compliance with the monitoring requirements specified above shall be taken at the outfall from the final treatment unit and prior to admixture with diluent water or the receiving stream. (a) (b) (c) (d) If the discharge occurs on an intermittent basis, samples shall be collected during the period when that intermittent discharge occurs. See "definitions" under the Monitoring and Reporting portion of this permit. Twice Weekly is defined as two different sampling dates per week; i.e. Monday/Wednesday or Tuesday/Thursday, etc. Monitor only if chlorine is used in the wastewater treatment process. Page 8

24 C. DOWNSTREAM MONITORING POINT (DMP1) Monitoring at DMP1 shall occur monthly from the date of issuance of the permit through October 31, 2018 for the parameters listed in the table below. This is not to be considered a compliance point, but rather a location to gather data to be used to set future permit limits. See Part I, Section G.9 for location of DMP1. Parameter Frequency Sample Type ph Monthly Grab Temperature, o C Monthly Grab Hardness, mg/l as CaCO 3 Monthly Grab D. SELENIUM COMPLIANCE SCHEDULE Based upon a Total Maximum Daily Load (TMDL) developed on Crow Creek (class 2C water); the facility has been allocated 5 µg/l selenium, total recoverable as the limit on discharges. A compliance schedule gives the community a window of opportunity to come into compliance with this requirement. 1. Compliance Schedule Event Description Due Date(s) Implementation Schedule Submit quarterly reports summarizing the progress in coming into compliance with the selenium limits for this facility discharge. Wyoming Department of Environmental Quality-Water Quality Division WYPDES Permitting Herschler Building, 4 West 122 West 25 th Street Cheyenne, WY Telephone: (307) The initial quarterly report is to be received no later than July 28, Quarterly reports are due on April 28 th, July 28 th, October 28 th and January 28 th of each year. The final report is due by August 28, Submit to the address in the table below. 1 The final compliance report is due after 8 months rather than 6 months. Page 9

25 E. COPPER, CADMIUM, AND LEAD COMPLIANCE SCHEDULE Based upon upfront analysis and annual pretreatment reports submitted to EPA, Region 8, this facility has shown the reasonable potential to contain amounts of copper, cadmium, and lead in amounts above surface water quality standards. Because of this, interim monitoring requirements and final proposed effluent limits for these three constituents have been included in the permit. A compliance schedule, which gives the community a window of opportunity to come into compliance with the proposed limits, is listed in the table below. 1. Compliance Schedule Reports for Copper, Cadmium, and Lead: The city shall develop an Implementation Plan outlining steps the facility will take to come into compliance with copper, cadmium, and lead limits by November 1, The plan shall identify specific milestones and dates in which the milestones will be completed that will ultimately lead to the achievement of the permit effluent limits. This plan must be submitted to the DEQ by July 28, In addition, quarterly reports must be submitted defining the progress of the development of the plan and implementation of milestones identified in the plan. 2. Compliance Schedule Event Description Due Date(s) Implementation Schedule Beginning July 28, 2014, quarterly reports must be submitted summarizing the progress of development and ultimate achievement of the Implementation Plan referenced above. This plan must be submitted by July 28, After the plan is submitted to the DEQ, quarterly reports must then describe the process of implementing the milestones as defined in the plan. The initial quarterly report is to be received no later than July 28, Quarterly reports are due on April 28 th, July 28 th, October 28 th and January 28 th of each year. The Implementation Plan must be submitted by July 28, Submit to the address below. Wyoming Department of Environmental Quality-Water Quality Division WYPDES Permitting Herschler Building, 4 West 122 West 25 th Street Cheyenne, WY Telephone: (307) F. WHOLE EFFLUENT TOXICITY TESTING 1. Effluent Limitations (Toxic Pollutants) Effective immediately upon issuance of this permit renewal, there shall be no chronic toxicity occurring in the effluent from this facility. a. Whole Effluent Testing (Chronic). Page 10

26 Starting in the second quarter of calendar year 2014, the permittee shall, at least once each calendar quarter, conduct chronic static replacement toxicity tests on a composite sample of the discharge. The replacement static toxicity tests shall be conducted in accordance with the procedures set out in 40 CFR 136 and the most current edition of Methods for Measuring the Chronic Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms, EPA-821 R In the case of conflicts in method, 40 CFR 136 will prevail. The permittee shall conduct a chronic static renewal toxicity test using Ceriodaphnia dubia and a chronic seven-day static renewal toxicity test using Pimephales promelas. All tests will be conducted utilizing a multi-dilution series consisting of at least five (5) concentrations and a control as defined below: Summer: May through September 98% effluent 85% effluent 70% effluent 50% effluent 25% effluent control (or 0% effluent) Winter: October through April 93% effluent 85% effluent 70% effluent 50% effluent 25% effluent control (or 0% effluent) In the event of inconclusive test results, the WDEQ reserves the right to require the permittee to perform additional tests at alternate dilutions and/or replicates. The WDEQ also reserves the right to require the submission of all information regarding all initiated tests, regardless of whether the tests were carried to completion or not. Chronic toxicity occurs when, during a chronic toxicity test, the 25% inhibition concentration (IC 25 ) calculated on the basis of test organism survival and growth or survival and reproduction, is equal to 98% effluent for the summer recreation season and is equal to 93% effluent for the winter recreation seasons. If chronic toxicity occurs at any outfall during a sampling period, then WDEQ will assume that all outfalls, which have not yet been sampled, exhibit similar chronic toxicity characteristics as well. If a test acceptability criterion is not met for control survival, growth, or reproduction, the test shall be considered invalid. In such cases, the test shall be repeated until all test acceptability criteria are met and valid results are obtained. If chronic toxicity occurs, an additional test shall be conducted within two (2) weeks of the date of when the permittee learned of the test failure. If only one species fails, retesting may be limited to this specie. Should chronic toxicity occur in the second test, testing shall occur once a month until further notified by the permit issuing authority. Page 11