National Pollutant Discharge Elimination System (NPDES) Permit Program FACT SHEET

Transcription

1 National Pollutant Discharge Elimination System (NPDES) Permit Program FACT SHEET Regarding an NPDES Permit To Discharge to Waters of the State of Ohio for Dynegy Miami Fort LLC Miami Fort Station Public Notice No.: Ohio EPA Permit No.: 1IB00001*LD Public Notice Date: July 5, 2018 Application No.: OH Comment Period Ends: August 5, 2018 Name and Address of Facility Where Name and Address of Applicant: Discharge Occurs: Dynegy Miami Fort LLC Dynegy Miami Fort LLC 312 Walnut Street, Suite Brower Road Cincinnati, OH North Bend, OH Hamilton County Receiving Water: Ohio River INTRODUCTION Development of a Fact Sheet for NPDES permits is mandated by Title 40 of the Code of Federal Regulations (CFR), Section and This document fulfills the requirements established in those regulations by providing the information necessary to inform the public of actions proposed by the Ohio Environmental Protection Agency (Ohio EPA), as well as the methods by which the public can participate in the process of finalizing those actions. This Fact Sheet is prepared in order to document the technical basis and risk management decisions that are considered in the determination of water quality based NPDES Permit effluent limitations. The technical basis for the Fact Sheet may consist of evaluations of promulgated effluent guidelines, existing effluent quality, instream biological, chemical and physical conditions, and the relative risk of alternative effluent limitations. This Fact Sheet details the discretionary decision-making process empowered to the Director by the Clean Water Act (CWA) and Ohio Water Pollution Control Law (Ohio Revised Code [ORC] 6111). Decisions to award variances to Water Quality Standards (WQS) or promulgated effluent guidelines for economic or technological reasons will also be justified in the Fact Sheet where necessary. No antidegradation review was necessary. Effluent limits based on available treatment technologies are required by Section 301(b) of the CWA. Many of these have already been established by the United States Environmental Protection Agency (U.S. EPA) in the effluent guideline regulations (a.k.a. categorical regulations) for industry categories in 40 CFR Parts Technology-based regulations for publicly-owned treatment works are listed in the Secondary Treatment Regulations (40 CFR Part 133). If regulations have not been established for a category of dischargers, the director may establish technology-based limits based on best professional judgment (BPJ). Ohio EPA reviews the need for water-quality-based limits on a pollutant-by-pollutant basis. Wasteload allocations (WLAs) are used to develop these limits based on the pollutants that have been detected in the discharge, and the receiving water s assimilative capacity. The assimilative capacity depends on the flow in the water receiving the discharge, and the concentration of the pollutant upstream. The greater the upstream flow, Page 1 of 55

2 and the lower the upstream concentration, the greater the assimilative capacity is. Assimilative capacity may represent dilution (as in allocations for metals), or it may also incorporate the break-down of pollutants in the receiving water (as in allocations for oxygen-demanding materials). The need for water-quality-based limits is determined by comparing the WLA for a pollutant to a measure of the effluent quality. The measure of effluent quality is called Projected Effluent Quality (PEQ). This is a statistical measure of the average and maximum effluent values for a pollutant. As with any statistical method, the more data that exists for a given pollutant, the more likely that PEQ will match the actual observed data. If there is a small data set for a given pollutant, the highest measured value is multiplied by a statistical factor to obtain a PEQ; for example if only one sample exists, the factor is 6.2, for two samples - 3.8, for three samples The factors continue to decline as samples sizes increase. These factors are intended to account for effluent variability, but if the pollutant concentrations are fairly constant, these factors may make PEQ appear larger than it would be shown to be if more sample results existed. SUMMARY OF PERMIT CONDITIONS New effluent limits are proposed for copper at outfall 002 because data indicates reasonable potential to exceed WQS. A 24-month compliance schedule has been included in the permit for the permittee to meet the new limits. New effluent limits are proposed for arsenic and mercury at internal monitoring station 608 based on the requirements of 40 CFR for flue gas desulfurization (FGD) wastewater. New final effluent limits are proposed for Escherichia coli at outfall 006. New WQS for E. coli became effective in April No compliance schedule is proposed for meeting these new final effluent limits. Based on best technical judgment, it is expected the facility will be able to comply when the permit becomes effective. More stringent loading limits are proposed for total suspended solids and oil and grease based on lower flows at outfall 002. New monitoring is proposed for copper and mercury at outfall 001 because recent data indicates that these are parameters of concern. Monitoring requirements are proposed to be removed for thermal discharge and operating output at outfall 001 because the facility no longer operates a once-through cooling water system and there is no longer reasonable potential to exceed WQS for temperature. Monitoring requirements are proposed to be removed for ammonia and zinc at outfall 002 because there is no longer reasonable potential to exceed WQS. Monitoring requirements are proposed to be removed for Kjeldahl nitrogen at outfall 002 because this is not a parameter of concern. New monitoring stations have been established to determine compliance with the zero-discharge limitation for bottom ash (603) and fly ash (604) transport water. Monthly discharge occurrence monitoring is proposed at internal monitoring stations 603 and 604. Flow rate monitoring is proposed at outfall 801 in order to meet 316(b) requirements. Page 2 of 55

3 Monitoring requirements are proposed to be removed for temperature at outfall 801 because recent data indicates that there is no longer reasonable potential to exceed WQS and historical data from this station is not representative of upstream temperatures. Monitoring requirements are proposed to be removed for total suspended solids at outfall 801 because this is not a parameter of concern in the plant s effluent. In Part II of the permit, special conditions are included that address operator certification, tracking of group 4 parameters; Section 316(b); and outfall signage. Page 3 of 55

4 Table of Contents Page INTRODUCTION... 1 SUMMARY OF PERMIT CONDITIONS... 2 PROCEDURES FOR PARTICIPATION IN THE FORMULATION OF FINAL DETERMINATIONS.. 6 INFORMATION REGARDING CERTAIN WATER QUALITY BASED EFFLUENT LIMITS... 6 LOCATION OF DISCHARGE/RECEIVING WATER USE CLASSIFICATION... 8 FACILITY DESCRIPTION... 8 DESCRIPTION OF EXISTING DISCHARGE... 8 ASSESSMENT OF IMPACT ON RECEIVING WATERS... 9 DEVELOPMENT OF WATER-QUALITY-BASED EFFLUENT LIMITS... 9 REASONABLE POTENTIAL/EFFLUENT LIMITS/MANAGEMENT DECISIONS OTHER REQUIREMENTS List of Figures Figure 1. Location of Dynegy Miami Fort Station Figure 2. Water Balance Diagram List of Tables Table 1. Monitoring Stations, Wastewater Sources, Treatment Processes, Discharge Points, and Flow Rates Table 2. Storm Water Outfalls at the Miami Fort Station Table 3. Average Annual Effluent Flow Rates Table 4. Effluent Characterization Based on Form 2C Data Table 5. Effluent Characterization Using Ohio EPA Data Table 6. Effluent Characterization Using Self-Monitoring Data Table 7. Projected Effluent Quality Table 8. Ohio EPA Toxicity Screening Results for Outfall Table 9. Water Quality Criteria in the Study Area Table 10. Instream Conditions and Discharger Flow Page 4 of 55

5 Table 11. Summary of Effluent Limits to Maintain Applicable Water Quality Criteria Table 12. Parameter Assessment Table 13. Final Effluent Limits List of Attachments Attachment 1. Applicable Federal Effluent Limitation Guidelines Attachment 2. List of Approved Boiler/Cooling Water System Additives Attachment 3. Cooling Water Intake Structure Compliance List of Addendums Addendum 1. Acronyms Page 5 of 55

6 PROCEDURES FOR PARTICIPATION IN THE FORMULATION OF FINAL DETERMINATIONS The draft action shall be issued as a final action unless the Director revises the draft after consideration of the record of a public meeting or written comments, or upon disapproval by the Administrator of the U.S. Environmental Protection Agency. Within thirty days of the date of the Public Notice, any person may request or petition for a public meeting for presentation of evidence, statements or opinions. The purpose of the public meeting is to obtain additional evidence. Statements concerning the issues raised by the party requesting the meeting are invited. Evidence may be presented by the applicant, the state, and other parties, and following presentation of such evidence other interested persons may present testimony of facts or statements of opinion. Requests for public meetings shall be in writing and shall state the action of the Director objected to, the questions to be considered, and the reasons the action is contested. Such requests should be addressed to: Legal Records Section Ohio Environmental Protection Agency P.O. Box 1049 Columbus, Ohio Interested persons are invited to submit written comments upon the discharge permit. Comments should be submitted in person or by mail no later than 30 days after the date of this Public Notice. Deliver or mail all comments to: Ohio Environmental Protection Agency Attention: Division of Surface Water Permits Processing Unit P.O. Box 1049 Columbus, Ohio The Ohio EPA permit number and Public Notice numbers should appear on each page of any submitted comments. All comments received no later than 30 days after the date of the Public Notice will be considered. Citizens may conduct file reviews regarding specific companies or sites. Appointments are necessary to conduct file reviews, because requests to review files have increased dramatically in recent years. The first 250 pages copied are free. For requests to copy more than 250 pages, there is a five-cent charge for each page copied. Payment is required by check or money order, made payable to Treasurer State of Ohio. For additional information about this fact sheet or the draft permit, contact Chris Monroe, (614) , Christopher.monroe@epa.ohio.gov. INFORMATION REGARDING CERTAIN WATER QUALITY BASED EFFLUENT LIMITS This draft permit may contain proposed water-quality-based effluent limits (WQBELs) for parameters that are not priority pollutants. (See the following link for a list of the priority pollutants: In accordance with ORC (J)(3), the Director established these WQBELs after considering, to the extent consistent with the Federal Water Pollution Control Act, evidence relating to the technical feasibility and economic reasonableness of removing the polluting properties from those wastes and to evidence relating to conditions calculated to result from that action and their relation to benefits to the people of the state and to accomplishment of the purposes of this chapter. This determination was made based on data and information Page 6 of 55

7 available at the time the permit was drafted, which included the contents of the timely submitted NPDES permit renewal application, along with any and all pertinent information available to the Director. This public notice allows the permittee to provide to the Director for consideration during this public comment period additional site-specific pertinent and factual information with respect to the technical feasibility and economic reasonableness for achieving compliance with the proposed final effluent limitations for these parameters. The permittee shall deliver or mail this information to: Ohio Environmental Protection Agency Attention: Division of Surface Water Permits Processing Unit P.O. Box 1049 Columbus, Ohio Should the applicant need additional time to review, obtain or develop site-specific pertinent and factual information with respect to the technical feasibility and economic reasonableness of achieving compliance with these limitations, written notification for any additional time shall be sent to the above address no later than 30 days after the Public Notice Date on Page 1. Should the applicant determine that compliance with the proposed WQBELs for parameters other than the priority pollutants is technically and/or economically unattainable, the permittee may submit an application for a variance to the applicable WQS used to develop the proposed effluent limitation in accordance with the terms and conditions set forth in OAC (D). The permittee shall submit this application to the above address no later than 30 days after the Public Notice Date. Alternately, the applicant may propose the development of site-specific WQS pursuant to OAC The permittee shall submit written notification regarding their intent to develop site specific WQS for parameters that are not priority pollutants to the above address no later than 30 days after the Public Notice Date. Page 7 of 55

8 LOCATION OF DISCHARGE/RECEIVING WATER USE CLASSIFICATION Dynegy Miami Fort LLC Miami Fort Station discharges to the Ohio River between mile points and Figure 1 shows the approximate location of the facility. This segment of the Ohio River is described by Ohio EPA River Code: , U.S. River Reach: , County: Hamilton, Ecoregion: Interior Plateau. The Ohio River is designated for the following uses under Ohio s WQS (OAC ): Warmwater Habitat, Agricultural Water Supply, Industrial Water Supply, Bathing Waters, and Public Water Supply. Use designations define the goals and expectations of a waterbody. These goals are set for aquatic life protection, recreation use and water supply use, and are defined in the Ohio WQS (OAC ). The use designations for individual waterbodies are listed in rules -08 through -32 of the Ohio WQS. Once the goals are set, numeric WQS are developed to protect these uses. Different uses have different water quality criteria. Use designations for aquatic life protection include habitats for coldwater fish and macroinvertebrates, warmwater aquatic life and waters with exceptional communities of warmwater organisms. These uses all meet the goals of the federal CWA. Ohio WQS also include aquatic life use designations for waterbodies which cannot meet the CWA goals because of human-caused conditions that cannot be remedied without causing fundamental changes to land use and widespread economic impact. The dredging and clearing of some small streams to support agricultural or urban drainage is the most common of these conditions. These streams are given Modified Warmwater or Limited Resource Water designations. Recreation uses are defined by the depth of the waterbody and the potential for wading or swimming. Uses are defined for bathing waters, swimming/canoeing (Primary Contact Recreation) and wading only (Secondary Contact which are generally waters too shallow for swimming or canoeing). Water supply uses are defined by the actual or potential use of the waterbody. Public Water Supply designations apply near existing water intakes so that waters are safe to drink with standard treatment. Most other waters are designated for agricultural water supply and industrial water supply. FACILITY DESCRIPTION The Miami Fort Station is a coal-fired steam electric generating station and generates approximately 1100 MW. This facility is involved in the generation, transmission, and distribution of electric power. The industrial processes at the facility include (see Figure 2): Steam-electric power generation Gypsum production (air pollution control by-product) The process operations at the Miami Fort Station are classified in the Standard Industrial Classification (SIC) category 4911, Electric Services. The process wastewaters generated from these operations are regulated under 40 CFR 423, Steam Electric Power Generating Point Source Category. The Miami Fort Station obtains water from the Ohio River for cooling purposes. DESCRIPTION OF EXISTING DISCHARGE The Miami Fort Station has three primary outfalls that discharge to the Ohio River (Outfalls 001, 002, and 006). Table 1. Monitoring Stations, Wastewater Sources, Treatment Processes, Discharge Points, and Flow Rates highlights the primary outfalls, internal monitoring stations, wastewater sources, treatment processes, Page 8 of 55

9 discharge/receiving streams and associated flows at the Miami Fort Station. Storm water outfalls are presented on Table 2. Storm Water Outfalls at the Miami Fort Station. The average flow rates for the permit cycle for all final outfalls are shown on Table 3. Table 4 presents data compiled from the NPDES permit renewal application Form 2C. Table 5 presents chemical specific data compiled from data collected by Ohio EPA. Table 6 presents a summary of unaltered Discharge Monitoring Report (DMR). Data are presented for the period January 2013 to December 2017, and current permit limits are provided for comparison. Table 7 summarizes the chemical specific data for outfalls 001, 002, and 006 by presenting the average and maximum PEQ values. Table 8. Ohio EPA Toxicity Screening Results for Outfall 002 summarizes the screening results of Ohio EPA bioassay sampling of the final effluent. ASSESSMENT OF IMPACT ON RECEIVING WATERS The Miami Fort Station discharges directly to the Ohio River in the Markland dam pool. Water quality monitoring on the Ohio River is performed by the Ohio River Valley Water Sanitation Commission (ORSANCO). This information can be found in the 2016 Biennial Assessment of Ohio River Water Quality Conditions (305b) Report and/or biological survey results/pool reports. The Biennial Report can be found at this website The most recent pool report can be found here ORSANCO evaluates the river for four uses: aquatic life, contact recreation impairment, public water supply, and fish consumption. The entire Ohio River was determined as fully attaining for aquatic life and public water supply uses. ORSANCO has designated the entire river as impaired for fish consumption uses due to concentrations of polychlorinated biphenyl compounds (PCBs) and dioxin compounds in fish tissue. Part II of the permit contains a condition that prohibits the presence of PCBs in the plant s discharges. DEVELOPMENT OF WATER-QUALITY-BASED EFFLUENT LIMITS Determining appropriate effluent concentrations is a multiple-step process in which parameters are identified as likely to be discharged by a facility, evaluated with respect to Ohio water quality criteria, and examined to determine the likelihood that the existing effluent could violate the calculated limits. Parameter Selection Effluent data for the Miami Fort Station were used to determine what parameters should undergo WLA. The parameters discharged are identified by the data available to Ohio EPA DMR data submitted by the permittee, compliance sampling data collected by Ohio EPA, and any other data submitted by the permittee, such as priority pollutant scans required by the NPDES application or by pretreatment, or other special conditions in the NPDES permit. The sources of effluent data used in this evaluation are as follows: Page 9 of 55

10 Self-monitoring data (DMR) January 2013 through December 2017 Ohio EPA bioassay sampling data 2015 and 2016 NPDES application Form 2C data 2014 to 2017 Statistical Outliers and Other Non-representative Data The data were examined and no values were removed from the evaluation. This data is evaluated statistically, and PEQ values are calculated for each pollutant. Average PEQ (PEQ avg) values represent the 95 th percentile of monthly average data, and maximum PEQ (PEQ max) values represent the 95 th percentile of all data points (see Table 7). The PEQ values are used according to Ohio rules to compare to applicable WQS and allowable WLA values for each pollutant evaluated. Initially, PEQ values are compared to the applicable average and maximum WQS. If both PEQ values are less than 25 percent of the applicable WQS, the pollutant does not have the reasonable potential to cause or contribute to exceedances of WQS, and no WLA is done for that parameter. If either PEQ avg or PEQ max is greater than 25 percent of the applicable WQS, a WLA is conducted to determine whether the parameter exhibits reasonable potential and needs to have a limit or if monitoring is required (see Table 12). Wasteload Allocation For those parameters that require a WLA, the results are based on the uses assigned to the receiving waterbody in OAC Dischargers are allocated pollutant loadings/concentrations based on the Ohio WQS (OAC ). Most pollutants are allocated by a mass-balance method because they do not degrade in the receiving water. For free-flowing streams, WLAs using this method are done using the following general equation: Discharger WLA = (downstream flow x WQS) - (upstream flow x background concentration). Discharger WLAs are divided by the discharge flow so that the allocations are expressed as concentrations. The applicable waterbody uses for this facility s discharge to the Ohio River and the associated stream design flows are as follows: Aquatic life (Warmwater Habitat) Toxics (metals, organics, etc.) Average 10% of annual 7Q10 Maximum 1% of annual 1Q10 Agricultural Water Supply 10% of harmonic mean flow Human Health (carcinogens) 10% of harmonic mean flow Human Health (non-carcinogens) 100% of 7Q10 Allocations are developed using a percentage of stream design flow as specified in Table 10, and allocations cannot exceed the Inside Mixing Zone Maximum (IMZM) criteria. The data used in the WLA are listed in Table 4, Table 5, and Table 6. The WLA results to maintain all applicable criteria are presented in Table 11. Whole Effluent Toxicity Wasteload Allocation Whole effluent toxicity (WET) is the total toxic effect of an effluent on aquatic life measured directly with a toxicity test. Acute WET measures short term effects of the effluent while chronic WET measures longer term and potentially more subtle effects of the effluent. WQS for WET are expressed in Ohio s narrative free from WQS rule [OAC (D)]. These free froms are translated into toxicity units (TUs) by the associated WQS Implementation Rule (OAC ). WLAs can then be calculated using TUs as if they were water quality criteria. Page 10 of 55

11 The WLA calculations for WET are similar to those for aquatic life criteria - using the chronic toxicity unit (TU c) and 7Q10 flow for the average and the acute toxicity unit (TU a) and 1Q10 flow for the maximum. These values are the levels of effluent toxicity that should not cause instream toxicity during critical low-flow conditions. For the Miami Fort Station, the WLA values are 1.0 TU a and 42 TU c (outfall 001); 1.0 TU a and 56 TU c (outfall 002); and 1.0 TU a and 9516 TU c (outfall 006). The chronic toxicity unit (TU c) is defined as 100 divided by the estimate of the effluent concentration which causes a 25% reduction in growth or reproduction of test organisms (IC 25): TU c = 100/IC 25 This equation applies outside the mixing zone for warmwater, modified warmwater, exceptional warmwater, coldwater, and seasonal salmonid use designations except when the following equation is more restrictive (Ceriodaphnia dubia only): TU c = 100/geometric mean of No Observed Effect Concentration and Lowest Observed Effect Concentration The acute toxicity unit (TU a) is defined as 100 divided by the concentration in water having 50% chance of causing death to aquatic life (LC 50) for the most sensitive test species: TU a = 100/LC 50 This equation applies outside the mixing zone for warmwater, modified warmwater, exceptional warmwater, coldwater, and seasonal salmonid use designations. REASONABLE POTENTIAL/EFFLUENT LIMITS/MANAGEMENT DECISIONS After appropriate effluent limits are calculated, the reasonable potential of the discharger to violate the WQS must be determined. Each parameter is examined and placed in a defined "group". Parameters that do not have a WQS or do not require a WLA based on the initial screening are assigned to either group 1 or 2. For the allocated parameters, the preliminary effluent limits (PEL) based on the most restrictive average and maximum WLAs are selected from Table 11. Summary of Effluent Limits to Maintain Applicable Water Quality Criteria. The average PEL (PEL avg) is compared to the average PEQ (PEQ avg) from Table 7, and the PEL max is compared to the PEQ max. Based on the calculated percentage of the allocated value [(PEQ avg PEL avg) X 100, or (PEQ max PEL max) X 100)], the parameters are assigned to group 3, 4, or 5. The groupings are listed in Table 12. Parameter Assessment. The final effluent limits are determined by evaluating the groupings in conjunction with other applicable rules and regulations. Table 13. Final Effluent Limits presents the final effluent limits and monitoring requirements proposed for the Miami Fort Station outfalls 001 (040), 002, and 006 and internal monitoring stations 608, 611, and 612 and the basis for their recommendation. Unless otherwise indicated, the monitoring frequencies proposed in the permit are continued from the existing permit. Outfall 001/040 ph The limits for ph are ORSANCO pollution control standards and are protective of WQS. Total residual chlorine and total residual oxidants Page 11 of 55

12 The Ohio EPA risk assessment (Table 12. Parameter Assessment) places total residual chlorine in group 5. This placement, as well as the data in Tables 4, 5, and 6, indicates that the reasonable potential to exceed WQS exists and limits are necessary to protect water quality. For this parameter, the PEQ is greater than 100 percent of the WLA. Pollutants that meet this requirement must have permit limits under OAC (A)(1). The proposed daily maximum concentration limit for total residual chlorine at outfall 001 is based on an analysis of the inside-mixing-zone maximum WQS when discharges of chlorine are limited to two hours per day. The limit for total residual oxidants is based on data submitted by the Chemical Manufacturers Association to U.S. EPA Region V that shows bromine being approximately four times as toxic as chlorine. The discharge limit for residual oxidants is therefore set at ¼ of the chlorine limit. The chlorine and oxidants limits for Outfall 040 are based on the WLA because this outfall allows chlorination/bromination more frequently than 2 hours/day. Copper and mercury The Ohio EPA risk assessment (Table 12. Parameter Assessment) places copper and mercury in group 4. This placement, as well as the data in Tables 4, 5, and 6, support that these parameters do not have the reasonable potential to contribute to WQS exceedances, and limits are not necessary to protect water quality. Monitoring for Group 4 pollutants (where PEQ exceeds 50 percent of the WLA) is required by OAC (A)(2). Arsenic, boron, chromium, molybdenum, nickel, barium, fluoride, iron, nitrate + nitrite, and sulfates The Ohio EPA risk assessment (Table 12. Parameter Assessment) places arsenic, boron, chromium, molybdenum, nickel, barium, fluoride, iron, nitrate + nitrite, and sulfates in groups 2 and 3. This placement, as well as the data in Tables 4, 5, and 6, support that these parameters do not have the reasonable potential to contribute to WQS exceedances, and limits are not necessary to protect water quality. No new monitoring is proposed. Flow rate and temperature Monitoring for these parameters is proposed to continue in order to evaluate the performance of the treatment plant. Outfall 002 Total suspended solids, oil and grease, and ph Federal effluent guideline limitations (ELGs) are based on available treatment technology. Federal and State laws and regulations require that dischargers meet both the ELGs and any standards need to comply with state WQS. Permit limits are based on the more stringent of the two. The limits recommended for total suspended solids, oil and grease, and ph are based on the federal effluent limitation guidelines (ELGs) found in 40 CFR Part 423. All limits are shown in Attachment 1. Oil and grease has a more stringent WQS. However, recent data indicates no reasonable potential to exceed WQS for oil and grease at this outfall. Therefore, only the BPT standards are proposed. Total residual chlorine and total residual oxidants Limits for residual chlorine are needed at this outfall because the effluent guidelines for cooling tower blowdown contain limits for free available chlorine (FAC). Using the same formula to calculate a maximum effluent guideline limit for TSS at Outfall 002: FAC (002) = 0.5 mg/l x (blowdown volume)/19.14 MGD (002 flow) = 0.37 mg/l. Page 12 of 55

13 We have included the WQ-based limit for total residual chlorine because that limit (0.038 mg/l) is more restrictive than 0.2 mg/l free available chlorine. The proposed limit for total residual chlorine is based on WLA as limited by the IMZM standard. The IMZM is a value calculated to avoid rapidly lethal conditions in the effluent mixing zone. Ohio EPA cannot authorize discharge of a pollutant greater than WQS. As with Outfall 001, the discharge limit for residual oxidants at Outfall 002 is set at ¼ of the chlorine limit. Copper The Ohio EPA risk assessment (Table 12. Parameter Assessment) places copper in group 5. This placement, as well as the data in Tables 4, 5, and 6, indicates that the reasonable potential to exceed WQS exists and limits are necessary to protect water quality. For this parameter, the PEQ is greater than 100 percent of the WLA. Pollutants that meet this requirement must have permit limits under OAC (A)(1). The daily maximum concentration limit for copper is based on reasonable potential to exceed WQS. The daily maximum loading limit for copper is based on the 95 th percentile of monthly average flows. Mercury The Ohio EPA risk assessment (Table 12. Parameter Assessment) places mercury in group 4. This placement, as well as the data in Tables 4, 5, and 6, support that this parameter does not have the reasonable potential to contribute to WQS exceedances, and limits are not necessary to protect water quality. Monitoring for Group 4 pollutants (where PEQ exceeds 50 percent of the WLA) is required by OAC (A)(2). In addition, the mercury effluent quality falls within 75 percent of the WLA. Under OAC (A)(2), parameters in this range must have a tracking requirement in the permit that specifies reductions in pollutant concentrations if effluent concentrations exceed the WLA. The tracking/reduction requirements are included in Part II of the permit. Arsenic, boron, selenium, and total filterable residue The Ohio EPA risk assessment (Table 12. Parameter Assessment) places arsenic, boron, selenium, and total filterable residue in groups 2 and 3. This placement, as well as the data in Tables 4, 5, and 6, support that these parameters do not have the reasonable potential to contribute to WQS exceedances, and limits are not necessary to protect water quality. Monitoring at a low frequency is proposed to document that these pollutants continue to remain at low levels. Aluminum, manganese, titanium, bis(2-ethylhexyl)phthalate, butyl benzyl phthalate, chromium, diethyl phthalate, molybdenum, strontium, zinc, antimony, barium, cadmium, chlorides, total filterable residue, fluoride, iron, lead, nickel, nitrate + nitrite, sulfates, and thallium The Ohio EPA risk assessment (Table 12. Parameter Assessment) places aluminum, manganese, titanium, bis(2- ethylhexyl)phthalate, butyl benzyl phthalate, chromium, diethyl phthalate, molybdenum, strontium, zinc, antimony, barium, cadmium, chlorides, total filterable residue, fluoride, iron, lead, nickel, nitrate + nitrite, sulfates, and thallium in groups 2 and 3. This placement, as well as the data in Tables 4, 5, and 6, support that these parameters do not have the reasonable potential to contribute to WQS exceedances, and limits are not necessary to protect water quality. No new monitoring is proposed. Monitoring for nitrate + nitrite and zinc is proposed to be removed. Ammonia Sufficient data is not available to conduct representative reasonable potential analysis for ammonia at the facility. A BPJ determination to remove ammonia monitoring is proposed based on analysis of ammonia data for outfall 002. Outfall 006 Page 13 of 55

14 E. coli Limits proposed for E. coli are based on WQS. Total suspended solids and 5-day biological oxygen demand The limits recommended for total suspended solids and 5-day carbonaceous biochemical oxygen demand are technology-based treatment standards included in 40 CFR Part 133, Secondary Treatment Regulation. Secondary treatment is defined by the Best Practicable Waste Treatment Technology criteria, which are minimum standards required of all publicly owned treatment works. Copper and mercury The Ohio EPA risk assessment (Table 12. Parameter Assessment) places copper and mercury in group 4. This placement, as well as the data in Tables 4, 5, and 6, support that these parameters do not have the reasonable potential to contribute to WQS exceedances, and limits are not necessary to protect water quality. Monitoring for Group 4 pollutants (where PEQ exceeds 50 percent of the WLA) is required by OAC (A)(2). Zinc The Ohio EPA risk assessment (Table 12. Parameter Assessment) places zinc in group 3. This placement, as well as the data in Tables 4, 5, and 6, support that this parameter does not have the reasonable potential to contribute to WQS exceedances, and limits are not necessary to protect water quality. No new monitoring is proposed. Hardness Monitoring for hardness is proposed to continue in order to compile data used to calculate IMZM limits for this outfall. Flow rate and turbidity Monitoring for these parameters is proposed to continue in order to evaluate the performance of the treatment plant. Internal Monitoring Stations 603 and 604 Federal effluent guideline limitations (ELGs) require a cease of bottom and fly ash transport water discharges by December 31, Monitoring is proposed at these stations to evaluate the Cardinal Plant s progress towards achieving the no discharge requirements. On a monthly basis, the permittee shall report the number of days that a discharge was observed for each station. Internal Monitoring Station 608 Arsenic, mercury, and total suspended solids Federal effluent guideline limitations (ELGs) are based on available treatment technology. The limits recommended for arsenic, mercury, and total suspended solids are based on the federal effluent limitation guidelines (ELGs) found in 40 CFR Part 423. All limits are shown in Attachment 1. Internal Monitoring Station 611 Total suspended solids and oil and grease Federal effluent guideline limitations (ELGs) are based on available treatment technology. The limits recommended for total suspended solids and oil and grease are based on the federal effluent limitation guidelines (ELGs) found in 40 CFR Part 423. All limits are shown in Attachment 1 Internal Monitoring Station 612 Page 14 of 55

15 Iron and copper Federal effluent guideline limitations (ELGs) are based on available treatment technology. The limits recommended for iron and copper are based on the federal effluent limitation guidelines (ELGs) found in 40 CFR Part 423. All limits are shown in Attachment 1 Whole Effluent Toxicity Reasonable Potential Based on evaluating the WET data presented in Table 8 and other pertinent data under the provisions of OAC (B), the Miami Fort Station is placed in Category 4 with respect to WET. No monitoring is proposed at this time. Additional Monitoring Requirements Additional monitoring requirements proposed at the final effluent, influent and upstream/downstream stations are included for all facilities in Ohio and vary according to the type and size of the discharge. In addition to permit compliance, this data is used to assist in the evaluation of effluent quality and treatment plant performance and for designing plant improvements and conducting future stream studies. Sludge Limits and monitoring requirements proposed for the disposal of sewage sludge by the following management practices are based on OAC : transfer to another facility with an NPDES permit. OTHER REQUIREMENTS Compliance Schedule A 24-month compliance schedule is proposed for the Miami Fort Station to meet the new daily maximum concentration and loading limits for copper at outfall 002. Details are in Part I.C of the permit. Operator Certification and Operator of Record Operator certification requirements have been included in Part II of the permit in accordance with rules adopted in December 2006 (OAC ). These rules require the Miami Fort Station to have a Class I wastewater treatment plant operator in charge of the sewage treatment plant operations discharging through outfall 006. These rules also require the permittee to designate one or more operator of record to oversee the technical operation of the treatment works. Cooling Water Intake Structure Compliance Under Section 316(b) of the federal CWA, cooling water intake structures (CWISs) are required to use best technology available (BTA) to minimize adverse environmental impact resulting from the operation of the intake. New rules were promulgated on October 14, 2014, and facilities with permits that expire after July 14, 2018 must be in compliance with the new rules. The CWIS is considered an existing unit at an existing facility and therefore must comply with 40 CFR 125, Subpart J. Information supplied from the permittee regarding the CWIS and other pertinent data are located in Attachment 3. Ohio EPA has evaluated this information and at this time has determined that the CWIS represents BTA in accordance with Section 316(b) of the CWA. This BTA conclusion has been reached based on the use of a closed-cycle recirculating cooling system to reduce flow and a through-screen design velocity of less than 0.5 feet per second (fps). In order to ensure that the facility remains compliant with Section 316(b), special conditions are included in Part II of the permit. Page 15 of 55

16 Steam Electric ELG Compliance Revisions to the Effluent Limitations Guidelines and Standards (ELGs) for the Steam Electric Power Generating Point Source Category were finalized on September 30, 2015, published in the Federal Register on November 3, 2015 (80 Fed. Reg. 67,838), and became effective on January 4, The rule required implementation as soon as possible beginning November 1, 2018, but no later than December 31, However, on April 25, 2017, the U.S. EPA published a stay in the federal register of compliance dates that have not yet passed. On September 17, 2017, U.S. EPA published another final rule that extended as soon as possible two years, or November 1, 2020, for bottom ash transport water and flue gas desulfurization waste streams. Within the preamble of the rule, the U.S. EPA included a footnote which indicated that the rule was being reconsidered and that if a new rule is not promulgated prior to November 1, 2020, that U.S. EPA would postpone the compliance dates again. The Director may establish a later date than November 1, 2020, based on four factors [40 CFR (t)] including the time it takes to design and raise capital as well as other factors as appropriate. Due to the uncertainty of the rule regarding bottom ash transport water, the Director has determined that as soon as possible is December 31, The most significant requirements that apply to the Miami Fort Station include: 1. A "no discharge" requirement for fly ash transport water, with a very limited exemption for transport water used as makeup water in a flue gas desulfurization (FGD) scrubber; 2. A "no discharge" requirement for bottom ash transport water, again with a limited exemption for use as makeup water in an FGD scrubber; and 3. Stringent arsenic, mercury, selenium, and nitrate/nitrite limits based on physical/chemical and biological treatment for FGD wastewater. Ohio EPA has approved a compliance end date of December 31, 2023 to meet all applicable ELG requirements. Additional language is proposed to capture the potential for different timelines and/or different final ELGs depending on additional rule-making by U.S. EPA. Preliminary effluent analysis of the facility s FGD wastewater indicates that the Miami Fort Station is currently capable of achieving compliance with the ELG Best Available Technology (BAT) limits for arsenic and mercury. Ohio EPA proposes that the Miami Fort Station be required to meet these limits by November 1, 2020, the initial date for compliance with the new Steam Electric ELGs. Outfall Signage Part II of the permit includes requirements for the permittee to place and maintain a sign at each outfall to the Ohio River providing information about the discharge. Signage at outfalls is required pursuant to OAC (A). Part III Part III of the permit details standard conditions that include monitoring, reporting requirements, compliance responsibilities, and general requirements. Storm Water Compliance Parts IV, V, and VI have been included with the draft permit to ensure that any storm water flows from the facility site are properly regulated and managed. As an alternative to complying with Parts IV, V, and VI, the Page 16 of 55

17 Miami Fort Station may seek permit coverage under the general permit for industrial storm water (permit # OHR000006) or submit a No Exposure Certification. Parts IV, V, and VI will be removed from the final permit if: 1) the Miami Fort Station submits a Notice of Intent (NOI) for coverage under the general permit for industrial storm water or submits a No Exposure Certification, 2) Ohio EPA determines that the facility is eligible for coverage under the general permit or meets the requirements for a No Exposure Certification, and 3) the determination by Ohio EPA can be made prior to the issuance of the final permit. Page 17 of 55

18 Figure 1. Location of Dynegy Miami Fort Station Page 18 of 55

19 Figure 2. Water Balance Diagram Page 19 of 55

20 Table 1. Monitoring Stations, Wastewater Sources, Treatment Processes, Discharge Points, and Flow Rates Station # Wastewater Source Treatment Utilized Discharge/ Receiving Stream Average Flow Rate (MGD) 001/040 Boiler Blowdown, Heat Exchangers, Cooling Water Dechlorination, Disinfection Ohio River Ash Pond B, RO Reject Water, Units 6, 7 & 8 Drains/Sumps, Boiler Tube Chemical Cleaning, Units 7 & 8 Ash Handling/CT Blowdown, FGD Effluent, Coal Pile Runoff, Storm Water Flocculation, Sedimentation, Coagulation, Neutralization Ohio River Sanitary Waste Aerobic Digestion, Clarification, Sand Filtration, UV Disinfection Ohio River FGD Wastewater Ash Pond Outfall Boiler Blowdown None Outfall Boiler Tube Chemical Cleaning Ash Pond Outfall Page 20 of 55

21 Table 2. Storm Water Outfalls at the Miami Fort Station Station # Represented by Representative Sampling Basis Plant area N of generating units; includes cooling towers, gas turbine generating station, and metal cleaning waste tank Plant area includes: generating units, coal piles, FGD area, crusher house. Central area of plant; includes SW yard, oil house, substations. Page 21 of 55

22 Table 3. Average Annual Effluent Flow Rates Outfall 001 Year Annual Flow in MGD 50th Percentile 95th Percentile Maximum Outfall 002 Year Annual Flow in MGD 50th Percentile 95th Percentile Maximum Outfall 006 Year Annual Flow in MGD 50th Percentile 95th Percentile Maximum MGD = million gallons per day Page 22 of 55

23 Table 4. Effluent Characterization Based on Form 2C Data Units Max daily No. of Parameter Conc Mass Conc Mass Analyses Outfall 001 Ammonia mg/l kg <0.10 <122 1 Aluminum µg/l kg Arsenic µg/l kg Barium µg/l kg Boron µg/l kg Bromide mg/l kg Chlorine, Total Residual mg/l kg Chromium µg/l kg Copper µg/l kg Fluoride mg/l kg Iron µg/l kg Manganese µg/l kg Mercury ng/l kg Molybdenum µg/l kg Sulfate µg/l kg Titanium µg/l kg Outfall 002 Ammonia mg/l kg Aluminum µg/l kg Antimony µg/l kg Arsenic µg/l kg Barium µg/l kg Boron µg/l kg Bromide mg/l kg Chlorine, Total Residual mg/l kg <0.012 < Chromium µg/l kg Copper µg/l kg Cyanide, Total µg/l kg Fluoride mg/l kg Iron µg/l kg Lead µg/l kg Manganese µg/l kg Mercury ng/l kg Molybdenum µg/l kg Nickel µg/l kg Page 23 of 55

24 Units Max daily No. of Parameter Conc Mass Conc Mass Analyses Selenium µg/l kg Sulfate µg/l kg Thallium µg/l kg Titanium µg/l kg Zinc µg/l kg Page 24 of 55

25 Table 5. Effluent Characterization Using Ohio EPA Data Outfall 002 Parameter Units 12/7/15 4/12/16 Aluminum mg/l Ammonia mg/l Arsenic µg/l Barium µg/l Bis(2-ethylhexyl) Phthalate µg/l Butyl Benzyl Phthalate µg/l Cadmium µg/l Calcium mg/l Carbonaceous Biochemical Oxygen Demand (5 day) mg/l AA (2) AA (2) Chloride mg/l Chloroethane µg/l AA (0.15) 0.19 Chromium µg/l Copper µg/l Cyanide, Free mg/l AA (3) AA (3) Diethyl Phthalate µg/l 1.1 AA (0.1) Iron mg/l Lead µg/l Magnesium µg/l Manganese µg/l Methyl Chloride µg/l 0.28 AA (0.18) Nickel µg/l Nitrate+Nitrite mg/l Oil & Grease mg/l AA (0.8) AA (0.8) Phosphorus mg/l Selenium µg/l Strontium µg/l Total Filterable Residue (Dissolved Solids) mg/l Total Kjeldahl Nitrogen mg/l Total Suspended Solids mg/l 16 6 Zinc µg/l 11 AA (2) AA = not-detected (analytical method detection limit) NA = not applicable Page 25 of 55

26 Table 6. Effluent Characterization Using Self-Monitoring Data Current Permit Limits Percentiles Parameter Season Units 30 day Daily # Obs. 50 th 95 th Data Range Outfall 001 Water Temperature Annual F - MONITOR Million - MONITOR- Thermal Discharge Annual BTU/Hr Station Operating Output Annual Megawatts - MONITOR ph Annual S.U. 6.0(min) - 9.0(max) Oxidants, Total Residual Annual mg/l Flow Rate Summer MGD - MONITOR Flow Rate Winter MGD - MONITOR Flow Rate Annual MGD - MONITOR Chlorine, Total Residual Annual mg/l Chlorination/Bromination Duration Annual Minutes - MONITOR Outfall 002 ph Annual S.U. 6.0(min) - 9.0(max) Residue, Total Dissolved Annual mg/l - MONITOR Total Suspended Solids Annual mg/l Oil and Grease, Total Annual mg/l Nitrogen, Ammonia (NH3) Summer mg/l - MONITOR Nitrogen, Ammonia (NH3) Winter mg/l - MONITOR Nitrogen Kjeldahl, Total Annual mg/l - MONITOR Nitrite Plus Nitrate, Total Annual mg/l - MONITOR Hardness, Total (CaCO3) Annual mg/l - MONITOR Arsenic, Total Recoverable Annual µg/l - MONITOR Selenium, Total Recoverable Annual µg/l - MONITOR Page 26 of 55

27 Current Permit Limits Percentiles Data Range Parameter Season Units 30 day Daily # Obs. 50 th 95 th Boron, Total Recoverable Annual µg/l - MONITOR Barium, Total Recoverable Annual µg/l - MONITOR Nickel, Total Recoverable Annual µg/l - MONITOR Zinc, Total Recoverable Annual µg/l - MONITOR Cadmium, Total - MONITOR- Recoverable Annual µg/l Lead, Total Recoverable Annual µg/l - MONITOR Chromium, Total - MONITOR- Recoverable Annual µg/l Copper, Total Recoverable Annual µg/l Oxidants, Total Residual Annual mg/l Flow Rate Summer MGD - MONITOR Flow Rate Winter MGD - MONITOR Flow Rate Annual MGD - MONITOR Chlorine, Total Residual Annual mg/l Mercury, Total (Low Level) Annual ng/l - MONITOR Residue, Total Filterable Annual mg/l - MONITOR Outfall 006 Color, Severity Annual Units - MONITOR ph Annual S.U. 6.0(min) - 9.0(max) Total Suspended Solids Annual mg/l Hardness, Total (CaCO3) Annual mg/l - MONITOR Zinc, Total Recoverable Annual µg/l - MONITOR Copper, Total Recoverable Annual µg/l - MONITOR Odor, Severity Annual Units - MONITOR Turbidity, Severity Annual Units - MONITOR Fecal Coliform Annual #/100 ml E. coli Annual #/100 ml Flow Rate Summer MGD - MONITOR Page 27 of 55