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HomeMy WebLinkAboutNC0004961_Fact Sheet_20150305Fact Sheet NPDES NC0004961 Renewal Page 1 DENR/DWR FACT SHEET FOR NPDES PERMIT DEVELOPMENT PERMIT RENEWAL NPDES No. NC0004961 Facility Information Applicant/Facility Name: Duke Energy Carolinas, LLC – Riverbend Steam Station Applicant Address: P.O. Box 1006, Charlotte, North Carolina 28201 Facility Address: 175 Steam Plant Road; Mount Holly, North Carolina 28120 Permitted Flow No limit Type of Waste: 100% industrial Prim.SIC Code: 4911 – Electric Services Facility/Permit Status: Class I/Active; Renewal County: Gaston County Miscellaneous Receiving Stream: Catawba River (Mt. Island Lake) Regional Office: Mooresville Stream Classification: WS-IV and B-CA State Grid / USGS Quad: F15Sw 303(d) Listed? No Permit Writer: Sergei Chernikov, Ph.D. Subbasin: 03-08-33 Date: May 21, 2014 Drainage Area (mi2): 1800 001: Lat. 35 21’ 28” N Long. 80 58’ 12” W 002: Lat. 35 22’ 06” N Long. 80 57’ 31” W 002B: Lat. 35 21’ 51” N Long. 80 58’ 11” W 011: Lat. 35 21’ 38” N Long. 80 58’ 38” W Summer 7Q10 (cfs) 80 Winter 7Q10 (cfs): 30Q2 (cfs) Average Flow (cfs): 2700 IWC (%) for Outfall 002: 0.4 – discharge 2.7 – dewatering SUMMARY Duke Energy’s Riverbend Steam Station was a coal fired steam electric plant in Gaston County, the electricity generation was discontinued on 04/1/2013. The facility has 5 permitted outfalls in the current NPDES discharge permit. The sources of wastewater for these outfalls include non - contact cooling water, ash basin discharge, sanitary waste, stormwater from process areas, sump overflows, and potentially contaminated groundwater seeps. The facility has no FGD scrubber. Currently, discharge of cooling water has discontinued and discharge from the ash pond significantly decreased. In addition to NPDES Permit NC0004961, the facility also holds 0388R20 (air permit) and NCD024717423 (Hazardous wastes). The facility is subject to 40 CFR 423 – Steam Electric Power Generation. The following descriptions of the wastes at each outfall are offered: 001 – Once through cooling water consisting of intake screen backwash and water from the plant chiller system, turbine lube oil coolers, condensate coolers, main turbine steam condensers and the intake tunnel dewatering sump. Since the facility was shut down, the discharge from this outfall is not anticipated. Fact Sheet NPDES NC0004961 Renewal Page 2 002 – Ash basin discharge consisting of induced draft fan and preheater bearing cooling water, stormwater from roof drains and paving, treated groundwater, track hopper sump (groundwater), coal pile runoff, laboratory drain and chemical makeup tanks and drums rinsate wastes, general plant/trailer sanitary wastewater, turbine and boiler rooms sumps, vehicle rinse water, and stormwater from pond areas, upgradient watershed, and miscellaneous stormwater flows. Most of the waste streams have discontinued, but some will remain. 002A- Yard drain sump overflow, discharge occurs rarely. 010 – Combined flow from all seeps. 011 – Former stormwater Outfall 1. Contains stormwater and groundwater flow, also includes wastewater from 10,000 gallon oil separator tank #3. The drainage basin includes a 2.7 acre portion of the main switchyard and 8,700 ft2 of the plant yard between power house and combustion turbine area. The powerhouse covers about 1.5 acres of the drainage basin. 100% of the drainage basin is paved or roofed. This facility discharges to the Mountain Island Lake (Catawba River) in sub-basin 03-08-33. The receiving stream is not listed as impaired. Duke Energy Submitted Application dated May 15, 2014. The current permit expires February 28, 2015. Duke Energy is required by the Coal Ash Management Act to remove all ash from the site by August 1, 2019. The discharge pipe NPDES outfall 002 from the secondary ash basin discharge tower at Riverbend Steam Station will be slip lined to ensure integrity. While this pipe is being slip lined, an alternative arrangement to convey wastewater to the permitted NPDES outfall 002 will be utilized. Temporary piping will be positioned in the secondary ash basin and the treated wastewater will be pumped to the NPDES outfall 002 discharge flow weir, located before the concrete flume that discharges into Mountain Island Lake. Once the slip line repairs are completed, the system will be returned to its original configuration. NPDES monitoring requirements will continue to be collected during the slip line project at the NPDES outfall 002 discharge flow weir. SEEPS-OUTFALL 010 The facility identified 12 unpermitted seeps from the ash settling basin. Seeps can be classified as either engineered seeps (toe drains) from the earthen dam or non-engineered seeps that occur as wastewater moves from the ash settling basin into groundwater and then into surface water, either directly or after emerging on land. Engineered seeps can be captured and routed through a permitted outfall. The non-engineered seeps represent a treatment system that has the potential to contaminate groundwater and surface water. The original design and location of the impoundment are such that wastewaster is not contained and directed to only engineered outfalls as the NPDES program generally contemplates, but wastes are also being released to groundwater and emerging in the form of seeps at the surface at diffuse and remote locations, with wastewater then flowing into surface waters depending on site specific factors. Potential groundwater contamination is regulated through North Carolina's 2L program. The CWA NPDES permitting program does not Fact Sheet NPDES NC0004961 Renewal Page 3 normally envision permitting of uncontrolled releases from treatment systems; such releases are difficult to monitor and control, and it is difficult to accurately predict their impact on water quality. Releases of this nature would typically be addressed through an enforcement action requiring their elimination rather than permitting. The non-engineered seeps at this facility represent a unique circumstance, where the occurrence of the seeps is attributable to an original pond design that will require long-term action to fully address. Recent North Carolina legislation (Coal Ash Management Act of 2014) establishes a framework for addressing all coal ash impoundments in the state to ensure that groundwater and surface water are adequately protected through closure or other measures. However, action to close or otherwise address coal ash impoundments and their threats to surface waters and groundwater will occur over a long term of those actions. In light of the long-term nature of action to fully address these impoundments, the Division is proposing, as an interim measure, to ensure that all non-engineered seeps are appropriately identified, monitored, and subject to protective effluent limits by including the seep discharges as authorized discharges in the facility's NPDES permit. The permit includes requirements to regularly inspect for new seeps, monitoring requirements for all identified seeps, and applicable effluent limits which ensure that the seeps will not result in unacceptable impacts to the receiving stream. The facility identified 12 unpermitted seeps and conducted chemical analysis of the discharges. The total flow from the seeps was measured at 0.14 MGD. Although, all seeps don’t have a permanent discharge and discharge from all seeps does not reach the surface water, for the purposes of the permitting it was assumed that all seeps reach the surface water. The seeps are not located on the walls of the dike, they appear as an emerging groundwater in a swampy area adjacent to the lake. The maximum allowable parameter concentration for seeps was determined by multiplying the highest concentration for a baseline seep data by 10. These values are substantially lower than the allowable concentration determined by the Reasonable Potential Analysis for the combined seep flow. The maximum allowable concentrations for Pb and TDS were established at the level of the water quality standards. ASH POND DAMS Seepage through earthen dams is common and is an expected consequence of impounding water with an earthen embankment. Even the tightest, best-compacted clays cannot prevent some water from seeping through them. Seepage is not necessarily an indication that a dam has structural problems, but should be kept in check through various engineering controls and regularly monitored for changes in quantity or quality which, over time, may result in dam failure. REASONABLE POTENTIAL ANALYSIS (RPA) The Division conducted EPA-recommended analyses to determine the reasonable potential for toxicants to be discharged at levels exceeding water quality standards/EPA criteria by this facility from outfall 002 (Ash Pond). Calculations included: As, Be, Cd, Total Phenolic Compounds, Cr, Cu, CN, Pb, Hg, Mo, Ni, Se, Ag, Zn, and Fe (please see attached). The renewal application listed 0.19 MGD as a current flow. The analysis indicates no reasonable potential to violate the surface water quality standards or EPA criteria. However, the monitoring will continue per recommendation of the hearing officer during the last renewal. The Division also considered data for other parameters of concern in the EPA Form 2C that the facility submitted for the renewal. The majority of the parameters were not detected in the Fact Sheet NPDES NC0004961 Renewal Page 4 discharge. The Division reviewed the following parameters that were detected in the discharge and have applicable state standards or EPA criteria for Class C WS-IV stream: fecal coliform, nitrate, Al, Ba, B, Co, Mn, Sb, and Tl. Most of these parameters were well below the state standards/EPA criteria. Only 1 parameter exceeded EPA criteria: Al (162 ug/L is above 87 ug/L). Considering the in-stream waste concentration of only 0.4%, even Al is not expected to violate applicable water quality criterion. The RPA was also conducted for the combined flow from all the seeps. The highest concentration for each constituent was chosen from one of the 12 seeps and used for the RPA. The RPA was not considered for the parameters that don’t have an applicable state water quality standard. Calculations included: As, Cd, Chlorides, Cr, Cu, F, Pb, Hg, Ni, Se, Zn, Ba, Fe, and Mn (please see attached). The analysis indicates no reasonable potential to violate the water quality standards or EPA criteria. The combined flow volume for all the seeps was measured at 0.14 MGD. However, the flow of 0.5 MGD was used for the RPA to incorporate a safety factor, account for potential new seeps that might emerge in the future or increase in flow volume at the existing seeps. The RPA was also conducted for the Outfall 011. Calculations included: As, Cd, Chlorides, Cr, Cu, F, Pb, Hg, Ni, Se, Zn, Ba, Fe, and Mn (please see attached). The analysis indicates no reasonable potential to violate the water quality standards or EPA criteria. The flow volume for the Outfall 011 was measured at 0.00036 MGD. However, the flow of 0.001 MGD was used for the RPA to incorporate a safety factor and potential increase in flow. The RPA analysis indicates that existing discharges from the facility outfalls will not cause contravention of the state water quality standards/ EPA criteria. DEWATERING – OUTFALL 002 To meet the requirements of the Coal Ash Management Act of 2014, the facility needs to dewater two ash ponds and excavate the ash to deposit it in the landfills. The facility highest discharge rate from the dewatering process will be 1.45 MGD. The facility submitted data for the surface water in the ash ponds, interstitial water in the ash, and interstitial ash water that was treated by 20 µm filter and 0.45 µm filter. To evaluate the impact of the dewatering on the receiving stream the RPA was conducted for the wastewater that will be generated by the dewatering process. To introduce the margin of safety, the highest measured concentration for a particular parameter was used. The RPA was conducted for As, Cd, Chlorides, Cr, Cu, F, Pb, Mo, Hg, Ni, Se, Zn, Ba, Fe, and Mn, SO4, Al, B, Sb, and Tl (please see attached). Based on the results of the RPA, the limit for Total Aluminum will be added to the dewatering effluent page. TECHNOLOGY BASED EFFLUENT LIMITS OUTFALL002 AND OUTFALL 010 The existing federal regulations require development of Technology Based Effluent Limits (TBELs) for the parameters of concern. Since the EPA has not promulgated any new Effluent Guidelines for Power Plants since 1982, the Division has reviewed the performance of the existing coal-fired power plants to establish TBELs: Marshall Steam Station, Belews Steam Station, and Allen Steam Station. Two of these facilities (Belews and Allen) were used by EPA to establish the proposed Effluent Guidelines for Power Plants. The Division focused on the following parameters: Total Arsenic, Total Mercury, Total Selenium, and Nitrate/nitrite as N. These parameters are consistent with the parameters selected by EPA in the proposed Effluent Guidelines. The Division agrees with the EPA statement from the proposed Effluent Guidelines Fact Sheet NPDES NC0004961 Renewal Page 5 that justifies TBEL limitations for only four pollutants of concern: “Effluent limits and monitoring for all pollutants of concern is not necessary to ensure that the pollutants are adequately controlled because many of the pollutants originate from similar sources, have similar treatabilities, and are removed by similar mechanisms. Because of this, it may be sufficient to establish effluent limits for one pollutant as a surrogate or indicator pollutant that ensures the removal of other pollutants of concern.” Based on the review of the effluent data for the past 5 years the Division established the following TBELs for the coal-fired power plants in North Carolina. The monthly average limits for Total Arsenic and Total Selenium are based on 95th percentile of the effluent data, which is consistent with the EPA methodology, and daily maximum limits for these constituents are based on the 99.9th percentile of the effluent data. The Total Mercury limit is based on the Statewide Mercury TMDL implementation strategy and was established by the Division previously. Total Arsenic – 10.5 µg/L (Monthly Average); 14.5 µg/L (Daily Maximum) Total Selenium – 13.6 µg/L (Monthly Average); 25.5 µg/L (Daily Maximum) Total Mercury – 47.0 ng/L (Monthly Average); 47.0 ng/L (Daily Maximum) The Division does not have any long-term data for Nitrate/nitrate as N. Therefore, the limits for this parameter are based on the proposed EPA Effluent Guidelines. Nitrate/nitrite as N – 0.13 mg/L (Monthly Average); 0.17 mg/L (Daily Maximum) Facility is allowed 4.5 years from the effective date of the permit to comply with the TBELs (Outfall 002 only–Ash Pond Discharge). This time period is provided in order for the facility to budget, design, and construct the treatment system. The compliance schedule is consistent with the proposed EPA Effluent Guidelines that require compliance with the TBELs “as soon as possible within the next permit cycle beginning July 1, 2012”. Since the permit cycle is 5 years, the Effluent Guidelines will allow the facility to comply with the TBELs by June 30, 2022. This permit has a more stringent requirements, the facility shall comply with the TBELs by the end of 2019. In the interim, the facility shall comply with the BPJ temporary limits that are derived by multiplying the proposed TBELs by 5, please see below: Total Arsenic – 52.5 µg/L (Monthly Average); 72.5 µg/L (Daily Maximum) Total Selenium – 68.0 µg/L (Monthly Average); 127.5 µg/L (Daily Maximum) Nitrate/nitrite as N – 0.65 mg/L (Monthly Average); 0.85 mg/L (Daily Maximum) Although these interim limits higher than the proposed TBELs, they are significantly lower than the allowable concentrations determined by the Reasonable Potential Analysis (RPA) and should be protective of the water quality in the receiving stream. The RPA allowable concentrations are listed below: Total Arsenic – 13,632.3 µg/L (Monthly Average); 91,690.8 µg/L (Daily Maximum) Total Selenium – 1,363.2 µg/L (Monthly Average); 12,492.0 µg/L (Daily Maximum) TEMPERATURE VARIANCE REMOVAL-OUTFALL 001 The facility historically had a temperature variance in accordance with CWA Section 316(a). In order to maintain the variance the facility had to conduct annual biological and chemical monitoring of the receiving stream to demonstrate that it has a balanced and indigenous Fact Sheet NPDES NC0004961 Renewal Page 6 macroinvertebrate and fish community. The latest BIP (balanced and indigenous population) report was submitted to DWQ in August of 2009. The ESS has reviewed the report and concluded that the Mountain Island Lake near Riverbend Station has a balanced and indigenous macroinvertebrate and fish community. Since the facility discontinued electricity generation in 2013, it does not wish to request continuation of the temperature variance. Therefore, Effluent Sheet A. (1.) was modified to reflect temperature requirements without a variance. CWA SECTION 316(B) Since the facility discontinued electricity generation in 2013 and does not use cooling water, it will not be the subject to the Section 316(b) of Clean Water Act. INSTREAM MONITORING-OUTFALL 002 The facility historically had 7 monitoring station, 2 located upstream and 5 located downstream. It is recommended that the monitoring will continue. The permit also required semi-annual upstream and downstream monitoring of the ash pond discharge. Upstream site (Station B) is approximately 2 miles upstream of the discharge and downstream location (Station C) is approximately 0.5 miles downstream of the discharge. These monitoring stations have been established through the BIP monitoring program, which was required to maintain 316(a) temperature variance. The monitored parameters are: As, Cd, Cr, Cu, Hg, Pb, Se, Zn, and Total Dissolved Solids (TDS). The majority of the results are below detection level, the rest of the results are below water quality standards. These results are consistent with the previous monitoring results. It is required that the monitoring at the stations B and C will continue until discharges from the station are ceased. It is also required that the facility uses low level method 1631E for all Hg analysis. FISH TISSUE MONITORING-OUTFALL 002 The permit required fish tissue monitoring for As, Se, and Hg near the ash pond discharge once every 5 years. This frequency is consistent with EPA guidance. Sunfish and bass tissues were analyzed for these trace elements. The results were below action levels for Se and Hg (10.0 µg/g – Se, 0.40 µg/g – Hg, NC) and screening value for As (1.20 – µg/g, EPA). These results are consistent with the previous monitoring results. TOXICITY TESTING- Outfall 002: Current Requirement: 24hr Chronic P/F @ 10% Recommended Requirement: 24hr Chronic P/F @ 2.7% (flow during dewatering) Monitoring Schedule: January, April, July, October This facility has passed all chronic toxicity tests during the previous permit cycle, please see attached. The change is the instream waste concentration was made based on the significant decrease in the discharge volume. COMPLIANCE SUMMARY Notwithstanding the civil lawsuit filed for unauthorized discharges and groundwater exceedances/violations, based on the monitoring required under the current version of the permit there were no violations of effluent standards contained in the permit. Fact Sheet NPDES NC0004961 Renewal Page 7 PERMIT LIMITS DEVELOPMENT  The pH limits (Outfalls 002, 002A, and 010) in the permit are based on the North Carolina water quality standards (15A NCAC 2B .0200).  The limits for Oil and Grease and Total Suspended Solids (Outfall 002 and Outfall 002A) are based on the Best Professional Judgment and are lower than prescribed in the 40 CFR 423.  The limits for Total Copper and Total Iron (Outfall 002 and Outfall 002A) were established in accordance with the 40 CFR 423.  The temperature limits (Outfall 001) are based on the North Carolina water quality standards (15A NCAC 2B .0200).  The turbidity limit in the permit (Outfall 002) is based on the North Carolina water quality standards (15A NCAC 2B .0200).  The Technology Based Effluent Limits (Outfall 002 and Outfall 010) for Total Arsenic, Total Mercury, Total Selenium, and Nitrate/nitrate as N are based on the requirements of 40 CFR 125.3(a) , 40 CFR 122.44(a)(1); 125.3(c) and (d).  The Interim Technology Based Effluent Limits (Outfall 002) for Total Arsenic, Total Selenium, and Nitrate/nitrate as N are based on the requirements of 40 CFR 125.3(a) , 40 CFR 122.44(a)(1); 125.3(c) and (d).  The Whole Effluent Toxicity limit (Outfall 002) is based on the requirements of 15A NCAC 2B .0500.  The Total Aluminum limits (Outfall 002 dewatering) in the permit are based on the results of the statistical analysis of the interstitial water data. REQUESTED MODIFICATIONS With the permit application for renewal, Duke Energy Carolinas, LLC has requested the following modifications: Monitoring Frequencies (Outfall 002) Parameter Present Proposed Flow Weekly Monthly Total Nitrogen 2/year 1/year Total Phosphorus 2/year 1/year Total Copper Quarterly none Total Iron Quarterly none These requests could not be granted because the Division needs these data to assure compliance with the water quality standards and criteria during the upcoming ash pond decanting/dewatering process. PROPOSED CHANGES:  Monitoring requirements for Outfall 001 were adjusted due to the discontinuation of once-through cooling water discharges.  The Ash Pond Closure Special Condition was updated (Please see A. (15.)).  The Seep Outfall 010 (Please see A. (5.)) and Seep Pollutant Analysis Special Condition (Please see A. (17.)) were added to the permit.  The Appendix A and Appendix B were added to the permit.  A separate effluent page for the dewatering of the ash ponds (Outfall 002) was added to the permit (Please see Special Condition A. (3.)).  The Boiler Cleaning Waste Special Condition was eliminated due to the discontinuation of the power generation. Fact Sheet NPDES NC0004961 Renewal Page 8  The Section 316(a) of CWA Thermal Variance Special Condition was eliminated due to the discontinuation of the power generation.  The Section 316(b) of CWA Special Condition was eliminated due to the discontinuation of the power generation.  The turbidity limit was added to the permit to meet the state turbidity standard per 15A NCAC 2B .0211(3) (k) (Outfall 002).  The Technology Based Effluent Limits for Total Arsenic, Total Mercury, Total Selenium, and Nitrate/nitrite as N were added to the permit and are based on the requirements of 40 CFR 125.3(a) , 40 CFR 122.44(a)(1); 40 CFR 125.3(c) and (d) (Outfall 002 and Outfall 010).  The Interim Technology Based Effluent Limits (Outfall 002) for Total Arsenic, Total Selenium, and Nitrate/nitrate as N were added to the permit and are based on the requirements of 40 CFR 125.3(a) , 40 CFR 122.44(a)(1); 125.3(c) and (d).  Proposed federal regulations require electronic submittal of all discharge monitoring reports (DMRs) and specify that, if a state does not establish a system to receive such submittals, then permittees must submit DMRs electronically to the Environmental Protection Agency (EPA). The Division anticipates that these regulations will be adopted and is beginning implementation. The requirement to begin reporting discharge monitoring data electronically using the NC DWR’s Electronic Discharge Monitoring Report (eDMR) internet application has been added to the permit. (Please see Special Condition A. (18.)).  The Applicable State Law Special Condition was added to the permit to meet the requirements of Senate Bill 729 (Coal Ash Management Act, Please see Special Condition A. (19.)).  The Outfall 011 (former Stormwater Outfall 1) was added to the permit (Please see A. (20.)). PROPOSED SCHEDULE: Draft Permit to Public Notice: March 6 , 2015 (est.) Permit Scheduled to Issue: July 27, 2015 (est.) STATE CONTACT: If you have any questions on any of the above information or on the attached permit, please contact Sergei Chernikov at (919) 807-6393 or sergei.chernikov@ncdenr.gov