The URL can be used to link to this page

Home My WebLink AboutNC0038377_Topographic Map/Discharge Assessment Plan_20160303 Mayo Steam Electric Plant Ash Basin Topographic Map and Discharge Assessment Plan NPDES Permit NC0038377 DUKE E N E RGY RECEIVED/NCDEQ/DWR FN MAY April 29, 2016 i Permitting • DUKE Harry Sidens Senior Vice President ENERGY. _ :ronmentat, Health d Safety 526 S Church Street Mail Code EC3XP Charlotte, NC 28202 (704/382.4303 April 28, 2016 Jeffrey O. Poupart Water Quality Permitting Section Chief Division of Water Resources Department of Environmental Quality State of North Carolina 1617 Mail Service Center Raleigh, NC 27699-1617 Subject: March 2, 2016 Insufficiency of Discharge Assessment Plans— Duke Energy Carolinas, LLC and Duke Energy Progress, LLC Dear Mr. Poupart: This responds to your 'etter of March 2, 2016 to Duke Energy Carolinas, LLC and Duke Energy Progress, LLC on March 2, 2016 regarding Duke Energy's proposed Discharge Assessment Plans. With regard to your letter describing changes in Section 3.2.2 Observation and Sampling: • The discussion must include a statement noting that jurisdictional determinations regarding the extent of waters of the United States and their relationship with identified seeps at the subject facilities will be obtained from the United States Army Corps of Engineers (USA COE). Duke Energy does not yet have jurisdictional determinations from the US Army Corps of Engineers for the relevant areas at all of the twelve sites mentioned in your letter. We submitted applications for jurisdictional determinations in September, October, and November 2015 and have since worked with the Corps of Engineers to schedule site visits and provide draft plats for approval. Nonetheless, the timing of the approved jurisdictional determinations is up to the Corps and outside of Duke's control_ To date, out of these twelve sites, only Buck has an approved jurisdictional determination, but we do not yet have the signed plats. We will submit the maps you have requested for each site on a rolling basis, within a reasonable period after the jurisdictional determinations are complete. In order to address the changes described in your March 2, 2016 letter, we have added the following text at the start of Section 3.2.2. Jurisdictional determinations regarding the extent of waters of the United States and their relationship with identified seeps at the subject facilities will be obtained from the United States Army Corps of Engineers (USA COE). Until jurisdictional determinations are finalized by USA COE, preliminary information will be used to evaluate the seeps as described in the section below. RECEIVED/NCDEQ/D" MAY 0 Water Quality Permitting Section The second change in Section 3.2.2 described in your letter is as follows. • The schedule for water quality sampling of the seeps and related jurisdictional waters must be more frequent than the semi-annual basis stated in the proposed DAPs. DWR recommends a monthly monitoring schedule, consistent with the conditions described in the DAPs`general assessment requirements, for all identified seeps that will continue for twelve ( 12)months. After that time, monitoring may be reduced to a semi-annual basis until such monitoring becomes a requirement of the NPDES permit. We do not believe sampling monthly as part of a revised Discharge Assessment Plan is warranted. For the larger receiving waters, data is available from sampling associated with NPDES permits that demonstrates the lack of impact on the larger surface waters of the state. In addition, we are conducting weekly observations of all AOWs on a dam or dike slope, sampling any new seeps, and providing the analytical results to DEQ. We recommend the sampling frequency under the DAPs remain at twice/year with the weekly inspections of dam slopes for any new seeps with data provided to DEQ. We recommend that we collectively focus our resources on the completion of all of the NPDES Wastewater Permits for the Duke Energy sites and implement appropriate sampling frequency for each of the permitted seeps in that document . However, in order to address the changes described in your March 2, 2016 letter, we have added the following text in Section 3.2.2. In addition to sampling conducted with the semi-annual assessments, additional seep sampling will be conducted at locations and at a frequency as determined through discussions with NC DEQ personnel. We would like to work with DEQ to achieve alignment of the various (present and future) documents involving required seep activities including: • Discharge Assessment Plans • Discharge Identification Plans • NPDES Wastewater Permits • EPA requirements • Any future legal agreements with either DEQ or EPA Duke Energy is committed to providing the Department with additional information to facilitate the issuance of new NPDES Wastewater permits. The issues are complex and require special consideration, as illustrated by the time elapsed since the permit applications were submitted. We look forward to working with you further to resolve the issues identified here on a mutually acceptable schedule. Sincerely, Harry Sideris Senior Vice President Environmental, Health and Safety Mayo Steam Electric Plant Ash Basin Topographic Map and Discharge Assessment Plan DUKE E N E NPDES Permit NC0038377 April 29,2016 J L RGY Duke Energy Progress,LLC 1 Discharge Assessment Plan �1J� Mayo Steam Electric Plant Ash Basin CONTENTS Contents Page Contents......................................................................................................................................i Figuresand Tables..................................................................................................................... Section1 - Introduction.............................................................................................................. 1 Section2- Site Background....................................................................................................... 3 2.1 Plant Description..................................................................................................3 2.2 Ash Basin Description..........................................................................................3 2.3 Site Geologic/Soil Framework..............................................................................3 2.4 Topographic Map and Identification of Discharges...............................................4 2.4.1 Engineered Drainage System for Earthen Dam........................................5 2.4.2 Non-Engineered Seep Identification.........................................................5 Section 3 - Discharge Assessment Plan..................................................................................... 6 3.1 Purpose of Assessment.......................................................................................6 3.2 Assessment Procedure........................................................................................6 3.2.1 General Assessment Requirements.........................................................6 3.2.2 Observation and Sampling .......................................................................7 3.2.3 Evaluation ................................................................................................9 3.2.4 Assessment Reporting .............................................................................9 Section4 - References..............................................................................................................10 Duke Energy Progress,LLC Discharge Assessment Plan FN Steam Electric Plant Ash Basin FIGURES AND TABLES Figures and Tables Figure 1 —Site Location Map Figure 2—Topographic Map Table 1 — Seep and Associated Discharge Locations and Descriptions Table 2— Laboratory Analytical Methods Table 3— Mayo Steam Electric Plant Ash Basin— Example of Surface Water/Seep Monitoring Flow and Analysis Results Table Duke Erergy Progress, LLC Discharge Assessment Plan FN Steam Eectric Plart Ash Basin SECTION 1 -INTRODUCTION Section 1 - Introduction The purpose of this document is to address the requirements of North Carolina General Statute (GS)130A-309.210(a) topographic map and (b) Assessment of Discharges from Coal Combustion Residuals Surface Impoundments to the Surface Waters of the State, as modified by North Carolina Senate Bill 729, for the Mayo Steam Electric Plant (Mayo Plant) ash basin operated under National Pollutant Discharge Elimination System (NPDES) Permit NC0038377. The following requirements are contained in General Statute (GS) 130A-309.210(a): (1) The owner of a coal combustion residuals surface impoundment shall identify all discharges from the impoundment as provided in this subsection. The requirements for identifying all discharges from an impoundment set out in this subsection are in addition to any other requirements for identifying discharges applicable to the owners of coal combustion residuals surface impoundments. (2) No later than December 31, 2014, the owner of a coal combustion residuals surface impoundment shall submit a topographic map that identifies the location of all (i) outfalls from engineered channels designed or improved for the purpose of collecting water from the toe of the impoundment and(ii) seeps and weeps discharging from the impoundment that are not captured by engineered channels designed or improved for the purpose of collecting water from the toe of the impoundment to the Department. The topographic map shall comply with all of the following: a. Be at a scale as required by the Department. b. Specify the latitude and longitude of each toe drain outfall, seep, and weep. c. Specify whether the discharge from each toe drain outfall, seep, and weep is continuous or intermittent. d. Provide an average flow measurement of the discharge from each toe drain outfall, seep, and weep including a description of the method used to measure average flow. e. Specify whether the discharge from each toe drain outfall, seep, and weep identified reaches the surface waters of the State. if the discharge from a toe drain outfall, seep, or weep reaches the surface waters of the State, the map shall specify the latitude and longitude of where the discharge reaches the surface waters of the State. f. Include any other information related to the topographic map required by the Department. The following requirements are contained in General Statute (GS) 130A-309.210(b): b) Assessment of Discharges from Coal Combustion Residuals Surface impoundments to the Surface Waters of the State. The owner of a coal combustion residuals surface impoundment shall conduct an assessment of discharges from the coal combustion Duke Energy Progress,LLC Discharge Assessment Plan 1 Mayo Steam.Electnc Plant Ash Basin J�� SECTION 1 -INTRODUCTION residuals surface impoundment to the surface waters of the State as provided in this subsection. The requirements for assessment of discharges from the coal combustion residuals surface impoundment to the surface waters of the State set out in this subsection are in addition to any other requirements for the assessment of discharges from coal combustion residuals surface impoundments to surface waters of the State applicable to the owners of coal combustion residuals surface impoundments. (1) No later than December 31, 2014, the owner of a coal combustion residuals surface impoundment shall submit a proposed Discharge Assessment Plan to the Department. The Discharge Assessment Plan shall include information sufficient to allow the Department to determine whether any discharge, including a discharge from a toe drain outfall, seep, or weep, has reached the surface waters of the State and has caused a violation of surface water quality standards. The Discharge Assessment Plan shall include, at a minimum, all of the following: a. Upstream and downstream sampling locations within all channels that could potentially carry a discharge. b. A description of the surface water quality analyses that will be performed. c. A sampling schedule, including frequency and duration of sampling activities. d. Reporting requirements. e. Any other information related to the identification of new discharges required by the Department. (2) The Department shall approve the Discharge Assessment Plan if it determines that the Plan complies with the requirements of this subsection and will be sufficient to protect public health, safety, and welfare; the environment,and natural resources. (3) No later than 30 days from the approval of the Discharge Assessment Plan, the owner shall begin implementation of the Plan in accordance with the Plan's schedule. The North Carolina Senate Bill 729 establishes the submittal date of this topographic map and Discharge Assessment Plan no later than December 31, 2014. The topographic map, developed to satisfy the requirements of GS1 30A-309.21 0(a), was utilized as the basis for developing the assessment procedures presented in this plan, required by GS1 30A-309.21 0(b). 2 Duke Energy Progress,LLC I Discharge Assessment Plan �� Mayo Steam < Electric Plant Ash Basin SECTION 2-SITE BACKGROUND Section 2 - Site Background 2.1 Plant Description The Mayo Plant is a single-unit, coal-fired electricity-generating facility located in Person County, North Carolina, near the city of Roxboro. The location of the Mayo Plant is shown on Figure 1. The Mayo Plant became fully operational in June 1983. The Mayo Plant is located on Boston Road (US Highway 501) north of Roxboro. The northern plant property line extends to the North Carolina/Virginia state line. The overall topography of the Mayo Plant generally slopes toward the east(Mayo Reservoir)and northeast (Crutchfield Branch). 2.2 Ash Basin Description The Mayo Plant ash basin is approximately 153 acres in size with an earthen dike. Ash generated from the Mayo Plant's coal combustion is contained in the ash basin. The ash basin was constructed and began receiving ash in 1983. The ash basin is located north of the Mayo Plant operational area and west of Mayo Lake. A former permitted landfill is located on the east side of the ash basin. The Mayo Plant NPDES permit(NC0038377)authorizes two discharges to Mayo Lake. Outfall 001 discharges cooling tower water and circulating water system discharge water. Outfall 002 is comprised of a number of streams including internal Outfall 008 (cooling tower blowdown), internal Outfall 009 (FGD blowdown), ash transport water, coal pile runoff, and other sources including water from wastewater treatment processes. Stormwater outfalls are also authorized for the Mayo Plant. 2.3 Site Geologic/Soil Framework The Mayo Plant is situated in the eastern Piedmont Region of north-central North Carolina. The Piedmont is characterized by well-rounded hills and rolling ridges cut by small streams and drainages. Elevations in the area of the Mayo Plant range between 570 feet above mean sea level (msl) near the Mayo Plant entrance along Boston Road to 360 feet msl in the Crutchfield Branch stream area on the north side of the Mayo Plant. Geologically, the Mayo Plant is located at the contact between two regional zones of metamorphosed intrusive rocks: the Carolina Slate Belt (now referred to as Carolina Terrane) on the east and the Charlotte Belt(or Charlotte Terrane)to the west. The majority of the Mayo Plant, including the largest portion of the ash basin and Mayo Lake are situated in the Carolina Terrane. The characteristics and genesis of the rocks within these regional metamorphic belts have been the subject of intense study to describe the geology in tectonic, structural, and/or litho-stratigraphic terms (Hibbard, et. al., 2002). Rocks of Charlotte Terrane are characterized by strongly foliated felsic mica gneiss and schist and metamorphosed intrusive rocks. Carolina Terrane rocks in the vicinity of the Mayo Plant are typically felsic meta-volcanics and meta-argillites. This is consistent with the description of the geologic nature of the area according to the Geologic Map of North Carolina (1985). The 3 Duke Energy Progress,LLC i Discharge Assessment Plan �11 Mayo Steam Electric Plant Ash Basin J< SECTION 2-SITE BACKGROUND Geologic Map of North Carolina describes the felsic meta-volcanic rock as metamorphosed dacitic to rhyolitic flows and tuffs, light gray to greenish gray; interbedded with mafic and intermediate volcanic rock, meta-argillite and metamudstone. The felsic mica gneiss of the Charlotte Terrane is described as being interlayered with biotite and hornblende schist. These general observations are consistent with site-specific observations from well logs for the Mayo Plant, which document the bedrock of the northwestern portion of the compliance boundary as intermediate meta-volcanic rock and the bedrock of the remainder of the site as felsic meta- volcanics or meta-argillites. Rocks of the region, except where exposed in road cuts, stream channels, and steep hillsides, are covered with unconsolidated material formed from the in-situ chemical and physical breakdown of the bedrock. This unconsolidated material is referred to as saprolite or residuum. Direct observations at the Mayo Plant confirm the presence of residuum, developed above the bedrock, which is generally 10 feet to 30 feet thick. The residuum extends from the ground surface (soil zones) downward, transitioning through a zone comprised of unconsolidated silt and sand, downward through a transition zone of partially weathered rock in a silt/sand matrix, down to the contact with competent bedrock. Based on previous activities at the site, subsurface lithology beneath the Mayo Plant area is comprised of tan, brown to orange sandy silt and fine to coarse sands grading into partially weathered rock and then competent bedrock. The first occurrence of groundwater tends to be within the partially weathered rock or competent bedrock at depths ranging from nine to 20 feet below land surface(bls)along the downgradient compliance boundary and greater than 30 feet bls upgradient of the ash basin. 2.4 Topographic Map and Identification of Discharges A topographic map is presented in Figure 2 to meet the requirements of GS 130A-309.210(a) in the identification of outfalls from engineered channels, as well as seeps and weeps. Seepage is the movement of wastewater from the ash basin through the ash basin embankment, the embankment foundation, the embankment abutments, basin rim, through residual material in areas adjacent to the ash basin. A seep is defined in this document as an expression of seepage at the ground surface. A weep is understood to have the same meaning as a seep. Indicators of seepage include areas where water is observed on the ground surface and/or where vegetation suggests the presence of seepage. Seepage can emerge anywhere on the downstream face, beyond the toe, or on the downstream abutments at elevations below normal pool. Seepage may vary in appearance from a "soft,"wet area to a flowing "spring." Seepage may show up first as only an area where the vegetation is lusher and darker green than surrounding vegetation. Cattails, reeds, mosses, and other marsh vegetation often become established in a seepage area. However, in many instances, indicators of seeps do not necessarily indicate the presence of seeps. Areas of apparent iron staining and/or excess iron bacteria may also indicate the presence of a seep. 4 Duke Energy Progress,LLC Discharge Assessment Pian 1 Mayo Steam Electric Plant Ash Basin J�� SECTION 2-SITE BACKGROUND Locations of seepage at the ground surface adjacent to the ash basin have been identified and are shown in Figure 2. These areas include the earthen embankment which impound the ash basin as well as adjacent areas where water from the ash basin may have infiltrated into the underlying residual materials and expressed as seepage. 2.4.1 Engineered Drainage System for Earthen Dam Earth dams are subject to seepage through the embankment, foundation, and abutments. Seepage control is necessary to prevent excessive uplift pressures, instability of the downstream slope, piping through the embankment and/or foundation, and erosion of material by migration into open joints in the foundation and abutments. The control of seepage is performed by the use of engineered drains such as blanket drains, trench drains, and/or toe drains. In certain cases horizontal pipes may be installed into the embankment to collect and control seepage. It is standard engineering practice to collect the seepage and convey seepage away from the dam. The Mayo Plant ash basin dam was constructed with a drainage system, which is monitored by Duke Energy. The drainage features, or outfalls, associated with the ash basin dam are shown as required by GS 130A-309.210(a)(2)(i)on Figure 2. 2.4.2 Non-Engineered Seep Identification Topographic maps of the site were reviewed to identify regions of the site where there was a potential for ash basin related seepage to be present. These regions were determined by comparing ash basin full pond elevations to adjacent topography with ground surface elevations lower than the ash basin full pond elevation. Synterra staff performed site observations within these identified areas as part of NPDES inspections during the reapplication process during August and November 2014 and documented locations where seepage was apparent at the time of the site visit. These seeps are identified as required by GS 130A-309.210(a)(2)(ii) on Figure 2. 5 Duke Energy Progress,LLC I Discharge Assessment Plan I Mayo Steam Electric Plant Ash Basin J�� SECTION 3-DISCHARGE ASSESSMENT PLAIN Section 3 - Discharge Assessment Plan 3.1 Purpose of Assessment The purpose of the assessment is to determine whether existing, known discharges from toe drain outfalls, seeps, and weeps associated with the coal combustion residuals surface impoundment(ash basin) have reached the surface waters of the State and have caused a violation of surface water quality standards as required by North Carolina General Statute 130A- 309.210(b). Figure 2 and Table 1 present the background and downstream sampling locations to be considered as part of this Discharge Assessment Plan (DAP). These locations may be assessed by comparing surface water sampling analytical results of the associated background location with the corresponding downstream location. For discharges located at the toe of a dam, an upstream location within the channel may not have been possible to isolate for comparison given the proximity to the ash basin, which would have the same chemical composition as the discharge itself. As such, the upstream location was established upstream of the ash basin and is considered "background." For discharges located a distance from the ash basin, an identified upstream, or"background" location for sampling may be compared to the downstream portion of the discharge channel. The background and downstream sampling locations are shown on Figure 2 with "6" and "D" identifiers, respectively, and the corresponding seep locations associated with the sampling locations are indicated on Table 1. 3.2 Assessment Procedure The assessment procedure associated with the Mayo Plant ash basin is provided within this section. In addition to the specific requirements for the assessment, Section 3.2 also provides the general requirements, the frequency of assessment, documentation requirements, and a description of the surface water quality analyses that will be performed. 3.2.1 General Assessment Requirements Assessments are to be performed in three phases as follows: • Observation and sampling (assessment site visit), • Evaluation, and Assessment reporting. The assessment site visit shall be performed when the background and downstream locations are accessible and not influenced by weather events. Locations on or adjacent to the ash basin embankments should be performed within two months after mowing, if possible. In addition, the assessment site visit should not be performed if the following precipitation amounts have occurred in the respective time period preceding the planned assessment site visit: • Precipitation of 0.1 inches or greater within 72 hours or • Precipitation of 0.5 inches or greater within 96 hours. The assessments shall be performed under the direction of a qualified Professional Engineer or Professional Geologist on a semi-annual basis within two nonadjacent quarters. The date of the 6 Duke Energy Progress, LLC Discharge Assessment Plan FN Steam Electric Plant Ash Basrr, SECTION 3 -DISCHARGE ASSESSMENT PLAN initial assessment site visit shall be selected no later than 30 days from the approval of the Discharge Assessment Plan and should fall within one of the semi-annual timeframes. Additional seep locations that may have been identified and documented in an Identification of New Discharge report(s) shall be reviewed prior to performing an assessment site visit, if available. 3.2.2 Observation and Sampling Jurisdictional determinations regarding the extent of waters of the United States and their relationship with identified seeps at the subject facilities will be obtained from the United States Army Corps of Engineers (USACE). Until jurisdictional determinations are finalized by USACE, preliminary information will be used to evaluate the seeps as described in the section below. The initial assessment site visit should be performed to document baseline conditions of the discharge channel, including location, extent (i.e., dimensions of affected area), and flow of each discharge. Discharge channel background and downstream locations should be verified using a Global Positioning System (GPS)device. Photographs should be taken from vantage points that can be replicated during subsequent semi-annual assessments. Initial and subsequent assessment site visits shall document a minimum of the following to respond to the requirements in 130A-309.210.1(b): • Record the most recent ash basin water surface elevation and compare to the seep and outfall and associated discharge location surface water elevations. • For each discharge channel, the observer shall note the following as applicable on the day of the assessment site visit: o Is the discharge channel flowing at the time of the assessment site visit? o Does the discharge channel visibly flow into a Water of the U.S. at the time of the assessment site visit? o How far away is the nearest Water of the U.S.? o Document evidence that flow has or could reach a Water of the U.S. (e.g., description of flow, including extent and/or direction) and describe the observed condition. Evidence that flow could or has reached a Water of the U.S. may be indicated by an inspection of the adjacent and downstream topographic drainage features. o Observe and document the condition of the discharge channel and outfall of the engineered channel or seep location with photographs. Photographs are to be taken from similar direction and scale as photographs taken during the initial assessment site visit. • Record flow rate within the discharge channel, if measureable, using the following methods: Duke Energy Progress, LLC Discharge Assessment Plan FN Steam Electric Plant Ash Basin SECTION 3.DISCHARGE ASSESSMENT PLAN o Timed-volumetric method: Collect a volume of water from the discharge of the PVC pipe directly into an appropriately sized container. Measure volumes (in mL) in the field utilizing a graduated container. Record the amount of time (in seconds) needed to collect the volume of water and calculate the flows (in MGD)for the timed-volume. o A V-notch weir apparatus will be installed, if necessary, during the initial assessment site visit to impound seepage at locations with a defined channel. Once the impounded seep reaches equilibrium discharge, flows will be measured using the timed-volumetric method described above. o Area-velocity method: Measure point velocities and water depth at a minimum of 20 stations along a transect setup perpendicular to the direction of flow using a Swoffer®3000 flow meter mounted to a standard United States Geologic Survey (USGS)top-set wading rod. Utilize the average velocity and cross-sectional area of the wetted channel to calculate flows in MGD. • Collect water quality samples using the following methods: o Collect background and downstream samples during a period with minimal preceding rainfall to minimize potential effects of stormwater runoff. Sampling procedures should prevent the entrainment of soils and sediment in water samples that can result in analytical results not being representative of the flow. Because Areas of Wetness (AOWs)/seeps often have poorly defined flow channels and minimal channel depth, conventional grab samples collected directly into laboratory containers or intermediate vessels is not possible without disturbance and entrainment of soils and sediments. Further, many AOWs are contiguous with low- lying areas subject to surface water runoff and resulting heavy sediment loading during storm events or are near surface waters subject to flooding such that representative samples of the AOW cannot be obtained. If the facility is unable to obtain an AOW sample due to the dry, low flow or high flow conditions preventing the facility from obtaining a representative sample, a "no flow" result or"excessive flow" will be recorded. o After collection, samples will be preserved and stored according to parameter- specific methods and delivered to the laboratory under proper Chain-of-Custody (COC) procedures. o Analytical parameters for analysis include: Fluoride, Arsenic, Cadmium, Copper, Chromium, Nickel, Lead, Selenium, and Mercury. This list includes all parameters previously identified for seep sampling at Duke Energy power plants for which relevant stream water quality standards are in place. (This list is responsive to the statutory requirement for the discharge assessment to allow determination whether discharges from toe drain outfalls, seeps, or weeps have reached surface waters and caused a violation of surface water quality standards.)Analyses shall be conducted by Duke Energy's Huntersville Analytical Laboratory (NC Wastewater Certification #248)and Pace Analytical Laboratories (NC Wastewater Certification 8 Duke Energy Progress, LLC i Discharge Assessment Plan 1 Mayo Steam Electric Plant Ash Basin J�� SECTION 3-DISCHARGE ASSESSMENT PLAN # 12). Laboratory analytical methods used for each constituent are provided in Table 2. o Seep in-situ measurements: In-situ field parameters (temperature and pH) shall be measured utilizing calibrated field meters either at the discharge of the seep directly, at the discharge of the flow measurement devices, or in the water pool created behind the device, if sufficient water depth did not exist at the device discharge. • In addition to sampling conducted with the semi-annual assessments, additional seep sampling will be conducted at locations and at a frequency as determined through discussions with NC DEQ personnel. 3.2.3 Evaluation Evaluation of the data from the initial assessment site visit will establish baseline conditions and will serve as the basis for comparison for subsequent assessment site visit results. Evaluation of observations and sampling results shall include location, extent (i.e., dimensions of affected area), and flow of each discharge. The analytical results of the upstream and downstream locations shall be compared to the 15A NCAC 213 standards for surface water quality upon receipt to identify potential exceedances. 3.2.4 Assessment Reporting Each assessment site visit shall be documented by the individual performing the assessment, as described in Section 3.2.2 to meet the requirements in 130A-309.210.1(b). The report should contain site background, observation and sampling methodology, and a summary of the observations and descriptions of the discharge channels observed, changes in observations compared to previous assessment events, estimates of flows quantities, and photographs of discharges and outfalls of engineered channels designed or improved for collecting water from the impoundment. Photographs are to be numbered and captioned. The flow and analytical results shall be recorded and presented in tables similar to the examples provided as Tables 1 and 3. The analytical results shall be compared to the 15A NCAC 213 standards for surface water quality and exceedances highlighted. This information shall be compiled, reviewed, and submitted to NC DEQ within 90 days from the Observation and Sampling event. 9 Duke Energy Progress, LLC'Discharge Assessment Plan 1AF11� ayo Steam Electric Plant Ash Basin SECTION 4-REFERENCES Section 4 - References Hibbard, James P., Edward F. Stoddard, Donald T. Secor, and Allen J. Dennis. 2002. The Carolina Zone: overview of Neoproterozoic to Early Paleozoic peri-Gondwanan terranes along the eastern Flank of the southern Appalachians: Earth Science Reviews, v. 57. North Carolina Department of Environment and Natural Resources. 2007. Dam Operation, Maintenance, and Inspection Manual, North Carolina Department of Environment and Natural Resources, Division of Land Resources, Land Quality Division, 1985 (Revised 2007). North Carolina Geological Survey. 1985. Geologic map of North Carolina: North Carolina Geological Survey, General Geologic Map , scale 1:500000. ,o FIGURES AND TABLES OR 3.1 \-7 PROPERTY BOUNDARY \. ,• '-cam `..- r+' ci < _ # WASTE ' > - ,BOUNDARY _� .� /, sir./ �y, � .� �>_ : • -'' ��I'��:. _7 ' �1 $fie '�. �., �,✓_ _t - �:� � ;. <. 500'COMPLIANCE 9 BOUNDARY _ lar o } ,• r-� 4 r � h , E� ( cl -. Z �f ^em QMonta�Ue. tiM 6iv t. -FATIAL L a - .. l Y SCALE .FEE-. h �1 r 1 lry �i , T $ O ti SITE LOCATION MAP aiF ul DUKE ENERGY PROGRESS DEC. 16. 2014 C y MAYO STEAM ELECTRIC PLANT 0 ,URE 1 NPDES PERMIT m - ROXBORO, NORTH CAROLINA HALIFAX COUNT' COMPLWNCEBOUNDARY MONRORINGWELLS LEGEND Discharge Location Coordinates NORTH CAROLINA VIRGINIA STATE LINE IAPPROXWATE) w 110 „'0Rr„INGm -A9nnc xl vE1F 1G Pr Loxatla(NCoardinafes Dlstlrvge Location plNl as) - O S-01 SEEP LOCATION See I plb�) Flom Flow Measurement ,Y PERSON COUNTY _ } ,,, cw-] 101270M5 23715as aesea P Background Location Md Discharge � 1 � 1 � COMPLIANCE GROUNDWATER Discharge ID Ong Description (IIIGD)and Method Sampling Location -%/ If/ ' --y� CVs]] vO1sTo355 203221 71 390.96 MONITORING WELL Latitude L iWM Latitude Longitude �/ 7"'� 1/ _._-k cwz ]o]mn3sa zo3zz3e.x] aesoo ac'w.x West toe drain;flows t Y - _ C'N4� 1 li.f a CRUTCHFIEL❑ fj,� f 1 vo]Susuew 2W 45uz. 3e95a DUKE ENERGY PROGRESS MAYO PLANT 5-01 36.53890 -78.89351 Continuous 0'00410 toward Crutchfield Branch , • Ay �/17y.` eRANCNr �'� cw-4 ]o]ss3zss zoo rsn2 500 R COMPLIANCE BOUNDARY ,,ti 1,1• } ]0}591 3 2030435]T 4513] fined-vdumebic 1_D � •\, � 7?'.. cwt -i-o15]62�3 zozs]eza9 509.60 - WASTE BOUNDARY 1 `3.-�. 'S"J- l Cwt ]]T43sz zo3x46.a6 46za3 �� FLOW DIRECTION(APPROXIMATE) East toe drain;flows --- �j 0.00362 toward Crutchfield Branch '� - ]moeosse zoze 9�s.ae 1-1 A" - NPDES OUTFALL LOCATION 5-02 3fi.53890 -78.8934, Continuous 7t sG] ,, timed-volumetric 1_p � y� }•- � W"M � � 6Gz � ■�-� STORM WATER OUTFALL LOCATION 20 ft upslope from east '� \ - I ( AS DISCHARGE SAMPLING LOCATIONS S-02A .36.53801. -78.89161 Intermittent NIA toedrain I '� `•^`S-04 cwz- )) + I U 36.539533 -78.889481 �,- 501 :%"' � ._..��__. _ �2-B BACKGROUND SAMPLING LOCATIONS LJpslope from east toe ` cw zn - �' S-02B 36.5380D -78.89137 Intermittent N/A dram .' �' -'�. /�I! 1 Vii' - �'--- f• _ ® TOPOGRAPHIC CONTOUR 14 FOOT INTERVAL) 1-D Channel downstream of S-03 36.53865 -78.89071 Continuous 0.02456 east toe drain limed-volumetric1-13 1-p f ```� ,' •]I. ,r f6 _ _ _ r Channel downstream of - S-G4 36.53890 -78.89341 Continuous NF West toe drain I � 1D a l 0.01102 South of plant;flows dMao Lake 36520625 -78.8831 towards y . 67 t 3fi.52197 -78.88526 Continuous 5-06 Y 3-area-velocity ,I D Downslope from former1981 LANDFILL S 5-07 36.52180 -78.89215 Intermittent N/A production well location '.;1 ACTIVE ASH BASIN " .73-E { / PERMIT NO.73-8 3-D - �. �� Over ione ddge from east toe drain;seems to 0.000724 ori9rate di ractlY from 36.539533 -78.889481 -ve 5-08 36.53750 -78.89040 Continuous timediumetrlc bedrock D / 1,��,1 , v ; �. �f^ � - -, l � �� fie, �_.�-_,•,/', POWER � �,I � � � i� , •�h ~ PLANT ��. r y�w�j 7. i r� "r I� 4 I f / � 1 LOO'S ANA PAGIfIC CORPORATION 1' •v+1,�..I, � � � � t _ ��.I I 4�4 4� y .e 1 r w" r'- Y of a r, SOURCES: 1. 2010 AERIAL PHOTOGRAPH OF PERSON COUNTY,NORTH CAROLINA WAS OBTAINED FROM NRCS GEOSPATIAL DATA GATEWAY AT GRAPHIC SCALE http://datagateway.nres.usda.gov/ 00 DATE oo TOPOGRAPHIC MAP WITH IDENTIFIED 2. 2012 AERIAL PHOTOGRAPH OF HALIFAX COUNTY,VIGINIA WAS OBTAINED FROM NRCS GEOSPATIAL DATA GATEWAY AT http://datagateway.nres.usda.gov/ SEEPS AND OUTFALLS DECEMBER,2014 3. 2014 AERIAL PHOTOGRAPH WAS OBTAINED FROM WSP FLOWN ON APRIL 17,2014. DUKE ENERGY CAROLINAS, LLC MAYO STEAM ELECTRIC PLANT FIGURE 4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200(NAD 83). NPDES PERMIT#NC0038377 2 5. WELL SURVEY INFORMATION,PROPERTY LINE,LANDFILL LIMITS AND BOUNDARIES ARE FROM ARCGIS FILES PROVIDED BYS&ME AND PROGRESS ENERGY. ROXBORO, NORTH CAROLINA 6. PARCEL BOUNDARIES WERE OBTAINED FROM PERSON COUNTY(NC)GIS DATA AT http://Os.personcounty.net a t t t Table 1-Mayo Steam Electric Station Ash Basin-Seep and Associated Discharge Locations and Descriptions t Location coordinatse Discharge Location Seep/ p"93) Flow Flow Measurement Background Discharge Location and Discharge Sampling (NAD coordinates M� m Discharge 10 Description (MGD)and Method Location Location t Latitude Longwxle Latitude Longitude S-01 36.53890 -78.89351 Continuous 0.00410 West toe drain;flows toward Crutchfield Branch timed-volumetric 1-D $-02 36.53890 78.89341 Continuous 0.0036'2 East toe drain;flows toward Crutchfield Branch limed-volumetric 1.0 t 20 ft upslope from east toe drain S-02A 36.53801 76.89161 Intermittent N/A 1-D t 36.539533 -78.889481 S-02B 36.53800 -78.89137 Intermittent N/A Upslope eran east toe drain 1-O 1 S-03 36.53865 -78.89071 Continuous 0.02456 Channel downstream of east toe drain timed-volumetric 1-8 1-0 I Channel downstream of west toe drain S-04 36.53890 -78.89341 Continuous NF 1-0 S-06 36.52197 -78.88526 Continuous 0.01102 South of plant;flows towards Mayo Lake area-velocity 3-0 36.520625 -78.883167 t S-07 36.52180 -78.89215 Intermittent NIA Downslope from former production well location 3-0 0.000724 Over one ridge from east toe drain;seems to t S-08 36.53750 •78.89040 Continuous originate directly from bedrock 36.539533 -78.889481 timed-volumetric 1-D I Notes: 1. Flow description for each seep sample location is based on observation during site visits performed by Synterra June and July 2014. t t t t t t t Table 2—Laboratory Analytical Methods Parameter Method ReportingLimit Units Laboratory Fluoride(F) EPA 300.0 1 mg/I Duke Energy Mercury(Hg) EPA 245.1 0.05 Ng/I Duke Energy Arsenic(As) EPA 200.8 1 Ng/I Duke Energy Cadmium(Cd) EPA 200.8 1 Ng/I Duke Energy Chromium(Cr) EPA 200.8 1 ug/I Duke Energy Copper(Cu) EPA 200.8 1 Ng/I Duke Energy Lead(Pb) EPA 200.8 1 Ug/I Duke Energy Nickel(Ni) EPA 200.8 1 Ng/I Duke Energy Selenium(Se) EPA 200.8 1 ug/I Duke Energy Monitoring Flow and Analysis Results Table Table 3-Mayo Steam Electric Plant Ash Basin Example of Surface Water/Seep g Y 5-08 Stormwater Stormwater S-01 5-02 5-02 5-03 5-04 5-05 5-06 (NOV 12 Parameter Units Outfall 004 Outfall 005 Duplicate 2014) Fluoride mg/l 0.51 0.22 0.15 < 0.1 < 0.1 0.14 0.16 0.30 0.18 0.11 Hg-Mercury(71900) Ng/l < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 As -Arsenic(01002) Ng/l < 1 < 1 2.64 < 1 < 1 < 1 1.97 3.03 < 1 < 1 Cd-Cadmium (01027) pg/l < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 Cr-Chromium(01034) Ng/I 2.05 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 Cu -Copper(01042) Ng/l 1.20 1.97 < 1 < 1 < 1 < 1 < 1 1.56 < 1 < 1 Pb -Lead (01051) Ng/l < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 Ni -Nickel (01067) Ng/l < 1 < 1 1.20 2.41 2.04 < 1 1.37 < 1 < 1 1.25 Se-Selenium (01147) Ng/l 2.58 2.08 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 PH S.U. 7.6 6.9 6.2 5.7 5.7 6.4 6.3 8.4 7.2 6.5 Temperature °C 21 22 19 17 17 19 25 27 21 15 Flow MGD 0.00106 0.05261 0.00410 0.00362 0.00362 0.02456 NF NM 0.01102 0.000724 Notes: 1. Flow measurements and analytical samples were collected on August 27, 2014 and November 12, 2014(S-08).