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HomeMy WebLinkAboutNC0004979_316 (b) Alternate Schedule Request_20141015 316 (b)Alternate Schedule Request Alternate Schedule Request§316(b)of the Clean Water Act Allen Steam Station Final regulations to establish requirements for cooling water intake structures at existing facilities were published in the Federal Register on August 15, 2014(i.e. regulations implementing§316(b)of the Clean Water Act)with an effective date of October 14, 2014. Allen Steam Station is subject to the regulations. The design intake flow of the station is greater than 2 million gallons per day (MGD) and the historical actual intake flows are greater than 125 MGD; therefore, the following submittals are expected to be required: — §122.21(r)(2)Source Water Physical Data — §122.21(r)(3)Cooling Water Intake Structure Data — §122.21(r)(4)Source Water Baseline Biological Characterization Data — §122.21(r)(5)Cooling Water System Data — §122.21(r)(6)Chosen Method(s)of Compliance with the Impingement Mortality Standard — §122.21(r)(7) Entrainment Performance Studies — §122.21(r)(8)Operational Status — §122.21(r)(9) Entrainment Characterization Study — §122.21(r)(10)Comprehensive Technical Feasibility and Cost Evaluation Study — §122.21(r)(11)Benefits Valuation Study — §122.21(r)(12) Non-water Quality and Other Environmental Impacts Study As allowed under §125.95(a)(2), Duke Energy would like to request an alternate schedule for the submittals listed above. Allen Steam Station was not subject to the remanded Phase II Rule due to the intake velocity; therefore, none of the above submittals were prepared. Duke Energy will need at least 60 months to prepare the necessary submittals.This timeframe includes complying with the peer review requirement for submittals§122.21(r)(10), §122.21(r)(11), and§122.21(r)(12). The rule requires the necessary submittals to be included with the permit renewal application for permits with an effective date after July 14, 2018. Duke Energy, therefore, would like to request the 316(b) submittals, with the exception of §122.21(r)(6) Chosen Method(s) of Compliance with Impingement Mortality Standard, for Allen Steam Station to be required with the subsequent permit renewal application after July 14, 2018. Since Allen Steam Station is subject to the entrainment best technology available (BTA) determination, a compliance schedule to complete §122.21(r)(6) Chosen Method(s) of Compliance with Impingement Mortality Standard will be requested to be included in the permit upon issuance of the entrainment BTA determination. Fish Tissue Monitoring Allen Steam Station NPDES Permit No. NC0004979 Monitoring of Arsenic,Selenium and Mercury in Fish Muscle Tissue from Upper Lake Wylie,NC Duke Energy 2014 Table of Contents Page 1.0 Introduction 1 2.0 Study Site Description and Sampling Locations 1 3.0 Target Species 1 4.0 Field Sampling Methods 1 5.0 Laboratory Processing and Arsenic,Selenium and Mercury Analysis 2 6.0 Data Analysis and Reporting 2 7.0 References 2 List of Tables Page Table 1 Arsenic,selenium and mercury concentrations in axial muscle of fish from Lake Wylie during April 2014. 3 List of Figures Page Figure 1 Lake Wylie arsenic,selenium and mercury monitoring locations 4 1.0 Introduction Duke Energy owns and operates the Allen Steam Station located on upper Lake Wylie in Gaston County, Belmont, NC. The Allen Station's National Pollutant Discharge Elimination System (NPDES) Permit (No. NC0004977 Section A 16) requires monitoring of trace elements (arsenic, selenium and mercury) in fish tissues near the discharge once per permit cycle. Fish were collected according to the submitted study plan(dated December 4, 2013). The resulting data are submitted in this report. 2.0 Study Site Description and Sampling Locations Fish were collected from three locations in upper Lake Wylie (Figure 1). These locations were adjacent to the Allen Station discharge (DI), 6.2 kilometers upstream (UP) and 10.9 kilometers downstream of the discharge(DN). 3.0 Target Species The target species of fish were largemouth bass and redear sunfish. As recommended by the US Environmental Protection Agency (EPA), an attempt was made to limit the smallest fish to 75% of the largest fish total length by species depending on availability(US EPA 2000). 4.0 Field Sampling Methods Fish were collected using electrofishing according to our Biology Program Procedures Manual (Procedure NR-00080, Rev. 1), which is approved by the NC Division of Water Resources under the Company's NC Biological Laboratory Certification (# 006), located at New Hill, NC. Only live fish that showed little or no signs of deterioration were retained for analysis. Retained fish were individually tagged(Floy tags), identified to species,measured for total length(mm), weight (g),placed on ice until frozen and transferred to a freezer within 24 hours of collection. Water quality data consisting of temperature, pH, dissolved oxygen, specific conductance and turbidity were recorded daily at the surface at each sampling location. Other noteworthy environmental conditions including river flow conditions and weather conditions were noted and are available upon request. 1 5.0 Laboratory Processing and Arsenic,Selenium and Mercury Analysis All fish samples were processed in the New Hill trace element laboratory according to procedure NR-00107 (Rev. 4) Trace Element Monitoring Laboratory Procedure. The processed samples (lyophilized left axial muscle; right muscle occasionally included when needed) were analyzed for arsenic, selenium and mercury by x-ray spectrophotometry. Quality control was achieved by analytical standards, replicates and certified reference materials. The remaining fish carcasses were archived and will be kept at least two years in the event that re-analysis is needed. 6.0 Data Analysis and Reporting Arsenic, selenium and mercury concentrations(converted to µg/g fresh weight) in the fish muscle tissue collected during 2014 are shown in Table 1. In addition to the length and weight of each fish, the dry-to-fresh weight ratios are presented to convert the arsenic, selenium and mercury concentrations fresh weight values back to dry weight values as desired. All fish collected during 2014 were below the US EPA Screening Values for Recreational Fishermen of 1.2 µg/g (fresh weight) for arsenic (US EPA 2000). All fish collected during 2014 were below the NC human consumption advisory level of 10 µg/g(fresh weight) for selenium. All fish collected during 2014 had mercury concentrations below the NC Health Directors Action Advisory Level of 0.4 µg/g fresh weight(NCDHHS 2006). References NCDHHS. 2006. Health effects of methylmercury and North Carolina's advice on eating fish. North Carolina Occupational and Environmental Epidemiology Branch,Raleigh,NC. US EPA. 2000. Guidance for assessing chemical contaminant data for use in fish advisories. Vol. 1. Fish sampling and analysis. Third edition. EPA 823-B-00-007. United States Environmental Protection Agency,Office of Water,Washington,DC. 2 Table 1. Arsenic, selenium and mercury concentrations (fresh weight) in axial muscle of fish from upper Lake Wylie during April 2014. Length Weight As Se Hg Dry-to-fresh Fish species Location Month (mm) (g) (pg/g) (pg/g) (pg/g) weight ratio* Largemouth bass UP April 377 630 0.21 0.37 <0.05 0.193 Largemouth bass UP April 411 878 0.08 0.40 <0.05 0.190 Largemouth bass UP April 408 822 0.14 0.45 <0.06 0.205 Largemouth bass UP April 316 381 0.18 0.47 <0.05 0.195 Largemouth bass UP April 338 550 0.08 0.35 <0.06 0.205 Largemouth bass UP April 422 952 <0.03 0.27 <0.03 0.127 Redear sunfish UP April 235 263 <0.04 0.70 <0.06 0.211 Redear sunfish UP April 224 195 0.04 0.79 <0.05 0.202 Redear sunfish UP April 218 162 0.04 0.52 <0.05 0.192 Redear sunfish UP April 261 283 0.06 0.52 <0.05 0.187 Redear sunfish UP April 214 161 <0.04 0.52 <0.05 0.200 Redear sunfish UP April 206 154 0.06 0.68 <0.05 0/00 Largemouth bass DI April 332 427 0.18 0.36 <0.05 0.198 Largemouth bass DI April 325 450 0.19 0.46 <0.06 0.209 Largemouth bass DI April 371 635 0.23 0.42 <0.06 0.209 Largemouth bass DI April 348 514 0.23 0.41 <0.06 0.206 Largemouth bass DI April 321 354 0.15 0.53 <0.05 0.190 Largemouth bass DI April 374 671 0.14 0.65 <0.05 0.198 Redear sunfish DI April 228 193 0.16 0.81 <0.05 0/03 Redear sunfish DI April 240 233 0.14 0.62 <0.05 0.194 Redear sunfish DI April 209 132 0.06 0.64 <0.06 0.207 Redear sunfish DI April 260 284 0.15 0.65 <0.05 0.191 Redear sunfish DI April 219 162 0.11 0.63 <0.05 0.185 Redear sunfish DI April 223 166 0.04 0.52 <0.05 0.186 Largemouth bass DN April 344 491 0.29 0.35 <0.05 0.196 Largemouth bass DN April 361 558 0.26 0.32 <0.06 0.214 Largemouth bass DN April 365 559 0.21 0.38 <0.06 0.213 Largemouth bass DN April 355 610 0.20 0.36 <0.05 0.197 Largemouth bass DN April 362 580 0.18 0.44 <0.05 0.198 Largemouth bass DN April 349 551 0.24 0.40 <0.05 0.200 Redear sunfish DN April 219 150 0.09 0.44 <0.05 0.185 Redear sunfish DN April 246 253 0.10 0.51 <0.05 0.198 Redear sunfish DN April 215 172 0.04 0.43 <0.05 0.195 Redear sunfish DN April 210 150 <0.04 0.46 <0.05 0.201 Redear sunfish DN April 203 146 0.04 0.49 <0.05 0.197 Redear sunfish DN April 209 155 0.04 0.53 0.05 0.203 *To convert to a dry weight,divide the fresh weight concentrations by the dry-to-fresh weight ratio. 3 ON Lake Metals Sampling in the Vicinity Of Ash Basins Allen Steam Station In-Stream Monitoring Plan 2011 - Present In-stream Monitoring Requirement A requirement to sample locations in Lake Wylie, semi-annually,upstream and downstream of the Allen Steam Station(AS) ash basin discharge was implemented in the March 1, 2011 AS National Pollutant Discharge Elimination System permit under section A.17 of the permit. The following document details methods and analyses of the monitoring program and provides the monitoring data to meet this requirement. In-stream Sampling Locations Lake Wylie water sampling locations are depicted in Figure 1. The upstream location(250) is approximately two miles upstream of the AS ash basin discharge. The downstream location(235) is approximately 3.0 miles downstream of the AS ash basin discharge. Sampling and Analytical Methods Grab samples collected from the surface(0.3 m) of the upstream and downstream locations in Lake Wylie were analyzed for the following parameters: arsenic(As), cadmium(Cd), chromium(Cr), copper (Cu), mercury(Hg), lead(Pb), selenium(Se),zinc(Zn), and total dissolved solids (TDS). Storage and preservation techniques of the samples after collection, and prior to analyses,were followed according to Appendix A. Analyses were conducted by Duke Energy's Huntersville analytical laboratory(NC Wastewater Certification#248). Methods of analysis and results for each parameter are in Table 1. Results/Recommendations Most of the analytical results upstream and downstream of the ash basin discharge with the exception of copper and zinc are at, or near,the method detection limits and below water quality standards. Measured values at these two locations are consistent with historical data from previous monitoring efforts in Lake Wylie. Duke Energy proposes that the semi-annual in-stream monitoring frequency be maintained. Gtlb�C." �E/4 Ca'^IY Beaver0am C� t Mountain Island Dam �f s P ,� Creek 1 i 1 e l .?� Allen Steam Station 250 (Upstream) �� Ash Basin Discharge SOUTH CARO�hA I ti : % 235 (Do wrtstrelfi* eef 9 0 Ate, CrG.w -Aw"rt 0 05 1 1 3 4 AAs 0 05 1 Y ] 4 ��.y r •� fr��f� O�`S A� SfuCma� i v `r ad i Catawba Nuclear ql �Statlon 4y jdp rr eP Wylie Dam Figure 1. Map of Lake Wylie with ash basin discharge and in -stream monitoring locations depicted. Appendix A Sample Preservation and Hold times parameter name Containerl Preservation2 3 Maximum noldina time Table 1BihOrgali Tests: 1.Acidity P,FP,G Cool,56°C18 14 days. 2.Alkalinity P,FP,G Cool,56°C18 14 days. 4.Ammonia P,FP,G Cool,56°CrB,H2SO4 to pH<2 28 days. 9.Biochemical Oxygen demand P.FP,G Cool,56°C18 48 hours. 10.Boron P,FP,or Quartz HNO3 to pH<2 6 months. 11.Bromide P,FP,G None required 28 days. 14.Biochemical oxygen demand,carbonaceous P,FP G Cool,56°C18 48 hours. 15.Chemical oxygen demand P,FP,G Cool,56'Ct8,HTSO,,to pH<2 28 days. 16.Chloride P, FP,G None required 28 days. 17.Chlorine,total residual P,G None required Analyze within 15 minutes. 21.Color P, FP,G Cool,56'C18 48 hours. 23-24.Cyanide,total or available(or CATC)and P,FP,G Cool,56°C18,NaOH to pH 14 days. free >1056,reducing agent if oxidizer present 25.Fluoride P None required 28 days. 27.Hardness P,FP,0 HNO3 or HaSQ06;PHH,<2 6 months. 28.Hydrogen ion(pH) P,FP,G None required Analyze within 15 minutes. 31,43.Kjeldahl iiiidiiiiiiiic N P.FP.0 Co9T`S¢',CC tb <2 28 days. Table IB—Metals:' 18.Chromium VI P.FP,0 Cool,56'Cts pH*.93:9.72Q 28 days. 35.Mercury(CVAA) P,FP,G HNO3 to pH<2 28 days. 35.Mercury(CVAFS) FP,G;and FP- 5 mUL 12N HCI or 5 mUL 90 days.' lined cap" BrCl17 3,5-8,12,13,19,20,22,26,29,30,32-34,36,37, P,FP,G HNO3 to pH<2,or at least 24 6 months. 45,47,51,52,58-60,62,63,70-72,74,75.Metals, hours prior to analysis19 except boron,chromium VI,and mercury 38.Nitrate P,FP,G Cool,56°Ct6 48 hors. 39.Nitrate-nitrite P,FP,G Cool,56°C18,H2SO4 to pH<2 28 days. 40.Nitrite P,FP,G Cool,56°C18 48 NOV. 41.Oil and grease G Cool to 56°C16,HCI or H2SO4 28 days. to pH<2 42.Organic Carbon P,FP,G Cool to 56'C1',HCI,H2SO4, 28 days. or H3PO4 to pH<2 44.Orthophosphate P,FP,G Cool,to 56°C1824 Filter within 15 minutes;Analyze within 48 hours. 46.Oxygen,Dissolved Probe G,Bottle and top None required Analyze within 15 minutes. 47.Winkler G,Bottle and top Fix on site and store in dark 8 hours. 48.Phenols G Cool,56°C16,H2SO4 to pH<2 28 days. 49.Phosphorous(elemental) G Cool,56°C18 48 hours. 50.Phosphorous,total P.FP,G Cool,56°C18,Hi.SO4jci pH<2 28 days. 53.Residue,total P,FP,G Cool,s6°C18 7 days. 54.Residue,Filterable P,FP,G Cool,s6°Ct8 7 days. 55.Residue,Nonfilterable(TSS) P,FP,G Cool,s6°C18 7 days. 56.Residue,Settleable P,FP.G Cool,56°C18 48 hours. 57.Residue,Volatile P,FP,G Cool,56°C18 7 days. 61.Silica P or Wertz Cool,56°Ct8 28 days. 64.Specific conductance P,FP,G Cool,56°C18 28 days. 95.Sulfate P.FP,0 Cool,56°Ct0 28 days. 66.Sulfide P,FP,G Cool,56°C18,add zinc 7 days. acetate plus sodium hydroxide to pH>9 67.Sulfite P,FP,G None required Analyze within 15 minutes. 68.Surfactants P,FP,G Cool,56°C18 48 hours. 69.TemPeratum P,FP,G None required Analyze. 73.Turbidity P,FP,G Cool,56°C18 48 hours. '"P"is for polyethylene;"FP"is fluoropolymer(polytetrafluoroethylene(PTFE);Teflon"),or other fluoropolymer,unless stated otherwise in this Table II;"G"is glass;"PA"is any plastic that is made of a sterilizable material(polypropylene or other autocavable plastic);"LDPE"is low density polyethylene. 2Except where noted in this Table II and the method for the parameter, preserve each grab sample within 15 minutes of collection. For a composite sample collected with an automated sample (e.g., using a 24-hour composite sample; see 40 CFR 122.21(gx7Hi)or 40 CFR Part 403,Appendix E),refrigerate the sample at 56°C during collection unless specified otherwise in this Table II or in the method(s). For a composite sample to be split into separate aliquots for preservation and/or analysis,maintain the sample at 56 °C, unless specified otherwise in this Table II or in the method(s), until collection, splitting, and preservation is completed.Add the preservative to the sample container prior to sample collection when the preservative will not compromise the integrity of a grab sample, a composite sample, or aliquot split from a composite sample within 15 minutes of collection. If a composite measurement is required but a composite sample would compromise sample integrity, individual grab samples must be collected at prescribed time intervals(e.g.,4 samples over the course of a day,at 6-hour intervals).Grab samples must be analyzed separately and the concentrations averaged. Alternatively, grab samples may be collected in the field and composited in the laboratory if the compositing procedure produces results equivalent to results produced by arithmetic averaging of results of analysis of individual grab samples. For examples of laboratory compositing procedures,see EPA Method 1664 Rev.A(oil and grease)and the procedures at 40 CFR 141.34(f)(14Xiv)and(v)(volatile organics). 3When any sample is to be shipped by common carrier or sent via the U.S. Postal Service, it must comply with the Department of Transportation Hazardous Materials Regulations (49 CFR part 172). The person offering such material for transportation is responsible for ensuring such compliance. For the preservation requirement of Table II, the Office of Hazardous Materials,Materials Transportation Bureau,Department of Transportation has determined that the Hazardous Materials Regulations do not apply to the following materials: Hydrochloric acid(HCI)in water solutions at concentrations of 0.04%by weight or less(pH about 1.96 or greater; Nitric acid(HNO3)in water solutions at concentrations of 0.15%by weight or less(pH about 1.62 or greater); Sulfuric acid (H2SO4) in water solutions at concentrations of 0.35% by weight or less (pH about 1.15 or greater); and Sodium hydroxide(NaOH)in water solutions at concentrations of 0.080%by weight or less(pH about 12.30 or less). `Samples should be analyzed as soon as possible after collection.The times listed are the maximum times that samples may be held before the start of analysis and still be considered valid. Samples may be held for longer periods only if the permittee or monitoring laboratory has data on file to show that, for the specific types of samples under study, the analytes are stable for the longer time,and has received a variance from the Regional Administrator under Sec. 136.3(e). For a grab sample,the holding time begins at the time of collection. For a composite sample collected with an automated sampler(e.g., using a 24-hour composite sampler;see 40 CFR 122.21(gX7)(i)or 40 CFR part 403,Appendix E),the holding time begins at the time of the end of collection of the composite sample. For a set of grab samples composited in the field or laboratory, the holding time begins at the time of collection of the last grab sample in the set. Some samples may not be stable for the maximum time period given in the table. A permittee or monitoring laboratory is obligated to hold the sample for a shorter time if it knows that a shorter time is necessary to maintain sample stability.See 136.3(e)for details.The date and time of collection of an individual grab sample is the date and time at which the sample is collected. For a set of grab samples to be composited,and that are all collected on the same calendar date, the date of collection is the date on which the samples are collected. For a set of grab samples to be composited, and that are collected across two calendar dates, the date of collection is the dates of the two days; e.g., November 14-15. For a composite sample collected automatically on a given date,the date of collection is the date on which the sample is collected. For a composite sample collected automatically,and that is collected across two calendar dates,the date of collection is the dates of the two days; e.g., November 14-15. For static-renewal toxicity tests,each grab or composite sample may also be used to prepare test solutions for renewal at 24 h,48 h,and/or 72 h after first use,if stored at 0-6°C,with minimum head space. 5ASTM D7365-09a specifies treatment options for samples containing oxidants (e.g., chlorine). Also, Section 9060A of Standard Methods for the Examination of Water and Wastewater(20th and 21st editions)addresses dechlorination procedures. (Sampling,preservation and mitigating interferences in water samples for analysis of cyanide are described in ASTM D7365- 09a.There may be interferences that are not mitigated by the analytical test methods or D7365-09a.Any technique for removal or suppression of interference may be employed, provided the laboratory demonstrates that it more accurately measures cyanide through quality control measures described in the analytical test method. Any removal or suppression technique not described in D7365-09a or the analytical test method must be documented along with supporting data. 'For dissolved metals, filter grab samples within 15 minutes of collection and before adding preservatives. For a composite sample collected with an automated sampler(e.g.,using a 24-hour composite sampler;see 40 CFR 122.21(gx7xi)or 40 CFR Part 403,Appendix E),filter the sample within 15 minutes after completion of collection and before adding preservatives.If it is known or suspected that dissolved sample integrity will be compromised during collection of a composite sample collected automatically over time(e.g., by interchange of a metal between dissolved and suspended forms), collect and filter grab samples to be composited (footnote 2)in place of a composite sample collected automatically. (Guidance applies to samples to be analyzed by GC,LC,or GC/MS for specific compounds. °If the sample is not adjusted to pH 2,then the sample must be analyzed within seven days of sampling. 10The pH adjustment is not required if acrolein will not be measured. Samples for acrolein receiving no pH adjustment must be analyzed within 3 days of sampling. "When the extractable analytes of concern fall within a single chemical category, the specified preservative and maximum holding times should be observed for optimum safeguard of sample integrity(i.e., use all necessary preservatives and hold for the shortest time listed).When the analytes of concern fall within two or more chemical categories, the sample may be preserved by cooling to 56°C,reducing residual chlorine with 0.008%sodium thiosulfate,storing in the dark,and adjusting the pH to 6-9;samples preserved in this manner may be held for seven days before extraction and for forty days after extraction.Exceptions to this optional preservation and holding time procedure are noted in footnote 5(regarding the requirement for thiosulfate reduction),and footnotes 12,13(regarding the analysis of benzidine). elf 1,2-diphenylhydrazine is likely to be present, adjust the pH of the sample to 4.0 ±0.2 to prevent rearrangement to benzidine. 13Extracts may be stored up to 30 days at<0°C. 14For the analysis of diphenylnitrosamine, add 0.008% Na2S2O3 and adjust pH to 7-10 with NaOH within 24 hours of sampling. "The pH adjustment may be performed upon receipt at the laboratory and may be omitted if the samples are extracted within 72 hours of collection.For the analysis of aldrin,add 0.008%Na2S2O3. 16Place sufficient ice with the samples in the shipping container to ensure that ice is still present when the samples arrive at the laboratory.However,even if ice is present when the samples arrive,immediately measure the temperature of the samples and confirm that the preservation temperature maximum has not been exceeded.In the isolated cases where it can be documented that this holding temperature cannot be met, the permittee can be given the option of on-site testing or can request a variance. The request for a variance should include supportive data which show that the toxicity of the effluent samples is not reduced because of the increased holding temperature.Aqueous samples must not be frozen. Hand-delivered samples used on the day of collection do not need to be cooled to 0 to 6°C prior to test initiation. "Samples collected for the determination of trace level mercury(<100 ng/L)using EPA Method 1631 must be collected in tightly-capped fluoropolymer or glass bottles and preserved with BrCI or HCI solution within 48 hours of sample collection.The time to preservation may be extended to 28 days if a sample is oxidized in the sample bottle.A sample collected for dissolved trace level mercury should be filtered in the laboratory within 24 hours of the time of collection. However, if circumstances preclude overnight shipment,the sample should be filtered in a designated clean area in the field in accordance with procedures given in Method 1669. If sample integrity will not be maintained by shipment to and filtration in the laboratory,the sample must be filtered in a designated clean area In the field within the time period necessary to maintain sample integrity. A sample that has been collected for determination of total or dissolved trace level mercury must be analyzed within 90 days of sample collection. "Aqueous samples must be preserved at 56°C, and should not be frozen unless data demonstrating that sample freezing does not adversely impact sample integrity is maintained on file and accepted as valid by the regulatory authority.Also,for purposes of NPDES monitoring,the specification of"5°C"is used in place of the"4°C"and"<4°C"sample temperature requirements listed in some methods. It is not necessary to measure the sample temperature to three significant figures (1/100th of 1 degree); rather, three significant figures are specified so that rounding down to 6 °C may not be used to meet the 56 °C requirement. The preservation temperature does not apply to samples that are analyzed immediately(less than 15 minutes). 1BAn aqueous sample may be collected and shipped without acid preservation. However, acid must be added at least 24 hours before analysis to dissolve any metals that adsorb to the container walls. If the sample must be analyzed within 24 hours of collection, add the acid immediately (see footnote 2). Soil and sediment samples do not need to be preserved with acid. The allowances in this footnote supersede the preservation and holding time requirements in the approved metals methods. 20To achieve the 28-day holding time, use the ammonium sulfate buffer solution specified in EPA Method 218.6. The allowance in this footnote supersedes preservation and holding time requirements in the approved hexavalent chromium methods, unless this supersession would compromise the measurement,in which case requirements in the method must be followed. 21Holding time is calculated from time of sample collection to elution for samples shipped to the laboratory in bulk and calculated from the time of sample filtration to elution for samples filtered in the field. 22Sample analysis should begin as soon as possible after receipt;sample incubation must be started no later than 8 hours from time of collection. 23For fecal coliform samples for sewage sludge (biosolids)only, the holding time is extended to 24 hours for the following sample types using either EPA Method 1680(LTB-EC)or 1681 (A-1):Class A composted,Class B aerobically digested,and Class B anaerobically digested. 24The immediate filtration requirement in orthophosphate measurement is to assess the dissolved or bio-available form of orthophosphorus(i.e.,that which passes through a 0.45-micron filter), hence the requirement to filter the sample immediately upon collection(i.e.,within 15 minutes of collection). [38 FR 28758,Oct. 16,1973 Ash Basin Capacity Calculations Duke Energy Company Allen Steam Station -Ash Basin Forecasting 2014 Wet Weather Detention Volume Calculation Determination of Wet Weather Detention Volume: Wet Weather Detention Volume is the sum of the runoff accumulated in the ash basin which results from a 10-yr 24-hr storm (assuming 100% runoff)plus the maximum 24-hr dry weather waste stream which discharges to the Ash Basin (refer to NPDES Permit NC0004979) I. Estimate Runoff to the Ash Basin from a 10-yr 24-hr storm: 1. Natural Drainage Area of Ash Basin= 288.0 Acres Station Yard Drainage Area Pumped to Ash Basin= 40.0 Acres Total= 328.0 Acres 2. Precipitation from 10-yr 24-hr storm= 5.0 Inches 3. Total Stormwater Runoff to Ash Basin= 136.67 Acre-feet (Assuming 100%runoff) II. Estimated Maximum 24-hr Dry Weather Waste Stream Discharging to Ash Basin: 1. Maximum recorded Ash Basin Discharge= 21,000,000 Gallons/day 2. Increase maximum daily disharge by 10%for conservatism and convert units to acre-feet= 70.89 Acre-feet III. Wet Weather Detention Volume: Sum of Parts I.and II.= 207.55 Acre-feet IV. Estimated Quantity of Solids(Ash)to be discharged to Ash Basin through December 31,2020. Note: NPDES Permit expiration date is 5/31/2015. Time Period Actual or %Ash Estimated Estimated Ash Estimated Estimated Estimated Total Ash Sent to Ash Ash Coal Production Structural Fill Discharged Discharged Consumption (1000's tons) or Lined Land to Ash basin to Ash basin (1000's tons) Fill(1000's (1000's tons) (Acre-feet) bons) 2014(Jun-Dec) 848.41 10.00% 84.84 72.11 12.73 10.62 2015 1283.88 10.00% 128.39 109.13 1926 16.08 2016 489.32 10.00% 48.93 41.59 7.34 6.13 2017 232.88 10.00% 2329 19.79 3.49 2.92 2018 107.53 10.00% 10.75 9.14 1.61 1.35 2019 47.95 10.00% 4.80 4.08 0.72 0.60 2020 77.74 10.00% 7.77 6.61 1.17 0.97 Total 3087.71 10.00% 308.77 262.46 46.32 38.66 * Calculation assumes an in-place ash density of 55 lbs. per cubic foot. Duke Energy Company Allen Steam Station -Ash Basin Forecasting 2014 Wet Weather Detention Volume Calculation V. Estimated Total Storage Volume Required through 2015: Wet Weather Detention Volume= 207.6 Acre-feet Estimated Solids to Ash Basin= 38.7 Acre-feet Required Storage Volume Through 12/31/2020= 246.2 Acre-feet VI. Results: Ash Basin @ Pond Elevation 644'+0" = 672.5 Acre-feet Total Available Storage= 672.5 Acre-feet Note: Available Storage based on basin survey dated 7/18/2014 Available Storage>Required Storage Based on these calculations,there is sufficient capacity in the ash basin to provide the retention volume specified in the permit through the year 2020.