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Home My WebLink AboutNC0004961_Other_20160503DUKE ENERGY. 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 Harry K. Sidens Senor Vice President Environmental, Health 8 Satety 526 S. Church Street Mail Code EC3XP Charlotte, NC 28202 (704) 362-4303 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 letter 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 Cotes 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/DWR MV. 0 6 Z016 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 DEG. 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 DEC) 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, �h= Harry Sideris Senior Vice President Environmental, Health and Safety Riverbend Steam Station Ash Basin Topographic Map and Discharge Assessment Plan NPDES Permit NC0004961 April 29, 2016 10 Contents Duke Energy Carolinas, LLC I Discharge Assessment Plan �� Riverbend Steam Station Ash Basin CONTENTS Paqe Contents......................................................................................................................................i " Figures and 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..............................................................................4 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 Carolinas, LLC I Discharge Assessment Plan �� Riverbend Steam Station 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 — Riverbend Steam Station — Example of Surface Water/Seep Monitoring Flow and Analysis Results Table Duke Energy Carolinas, LLC I Discharge Assessment Plan Riverbend Steam Station Ash Basin SECTION 1 -INTRODUCTION Section 1 - Introduction The purpose of this document is to address the requirements of North Carolina General Statute (GS)l 30A-309.21 0(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 Riverbend Steam Station (RBSS) ash basin operated under National Pollutant Discharge Elimination System (NPDES) Permit NC0004961. 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 i Duke Energy Carolinas, LLC I Discharge Assessment Plan 1 � Riverbend Steam Station Ash Basin J1 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 -- n f discharges subsection are In addition to any other requirements for the assessment es o g 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. i; 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 Carolinas, LLC I Discharge Assessment Plan �� Riverbend Steam Station Ash Basin SECTION 2 -SITE BACKGROUND Section 2 - Site Background 2.1 Plant Description RBSS is a former coal-fired electricity generating facility which had a capacity of 454 megawatts located in Gaston County, North Carolina, near the town of Mt. Holly (Figure 1). As of April 1, 2013, all of the coal-fired units have been retired. The seven -unit station began commercial operation in 1929 with two units and then expanded to seven by 1954. During its final years of operation, RBSS was considered a cycling station and was brought online to supplement energy supply when electricity demand was at its highest. 2.2 Ash Basin Description The ash basin system consists of a Primary Cell and a Secondary Cell, separated by an intermediate dike. The ash basin at RBSS originally consisted of a single -cell basin commissioned in 1957 and was expanded in 1979. The single basin was divided by constructing a divider dike to form two separate cells in 1986. The ash basin is located approximately 2,400 feet to the northeast of the power plant, adjacent to Mountain Island Lake, as shown on Figure 2. The Primary Cell is impounded by an earthen embankment dike, referred to as Dam #1 (Primary), located on the west side of the Primary Cell. The Secondary Cell is impounded by an earthen embankment dike, referred to as Dam #2 (Secondary), located along the northeast side of the Secondary Cell. The toe areas for both dikes are in close proximity to Mountain Island Lake. The surface area of the Primary Cell is approximately 41 acres with an approximate maximum pond elevation of 724 feet. The surface area of the Secondary Cell is approximately 28 acres with an approximate maximum pond elevation of 714 feet. The full pond elevation of Mountain Island Lake is approximately 646.8 feet. The ash basin system was an integral part of the station's wastewater treatment system which predominantly received inflows from the ash removal system, station yard drain sump, and stormwater flows. During station operations, inflows to the ash basin were highly variable due to the cyclical nature of station operations. The inflows from the ash removal system and the station yard drain sump are discharged through sluice lines into the Primary Cell. The discharge from the Primary Cell to the Secondary Cell is through a concrete discharge tower located near the divider dike. Although the station is retired, wastewater effluent from other non -ash -related station discharges to the ash basin is discharged from the Secondary Cell, through a concrete discharge tower, to Mountain Island Lake. The concrete discharge tower drains through a 30- inch-diameter corrugated metal pipe (CMP) into a concrete -lined channel that discharges to Mountain Island Lake. The ash basin pond elevation is controlled by the use of concrete stoplogs. 3 Duke Energy Carolinas, LLC I Discharge Assessment Plan L-2%11 Riverbend Steam Station Ash Basin SECTION 2 - SITE BACKGROUND 2.3 Site Geologic/Soil Framework RBSS is located in the Charlotte terrane within the Piedmont province. The Piedmont province is bounded to the east and southeast by the Atlantic Coastal Plain and to the west by the escarpment of the Blue Ridge Mountains, covering a distance of 150 to 225 miles (LeGrand, 2004). Piedmont bedrock primarily consists of igneous and metamorphic bedrock. The fractured bedrock is overlain by a mantle of unconsolidated material known as regolith. The regolith includes, where present, the soil zone, a zone of weathered, decomposed bedrock known as saprolite, and where present, alluvium. Saprolite, the product of chemical and mechanical weatheringof the underlying bedrock, is typically composed of clay and coarser granular Y 9 tYP Y P Y material up to boulder size and may reflect the texture of the rock from which it was formed. The weathering product of granitic rocks may be quartz -rich and sandy -textured, whereas rocks poor in quartz and rich in feldspar and other soluble minerals form a more clayey saprolite. The regolith serves as the principal storage reservoir for the underlying bedrock (LeGrand, 2004). A transition zone may occur at the base of the regolith between the soil-saprolite and the unweathered bedrock. This transition zone of partially weathered rock is a zone of relatively high permeability compared to the overlying soil-saprolite and the underlying bedrock (LeGrand, 2004). RBSS is located in the Charlotte terrane of the Carolina Zone (Pippin et al., 2008), or in the older belt terminology, the Charlotte Belt of the Piedmont physiographic province (Piedmont). The Charlotte terrane is characterized by mostly felsic to mafic plutonic rocks which intrude a suite of mainly metaigneous rocks and minor metasedimentary rocks (Pippin et al., 2008). Groundwater flow paths in the Piedmont are almost invariably restricted to the zone underlying the topographic slope extending from a topographic divide to an adjacent stream. LeGrand describes this as the local slope aquifer system. Under natural conditions, the general direction of groundwater flow can be approximated from the surface topography (LeGrand 2004). i _ Groundwater recharge in the Piedmont is derived entirely from infiltration of local precipitation. Groundwater recharge occurs in areas of higher topography (i.e., hilltops) and groundwater discharge occurs in lowland areas bordering surface water bodies, marshes, and floodplains (LeGrand 2004). The RBSS ash basin is generally bounded to the north by the earthen dike and a natural ridge located between the south bank of the Catawba River on Mountain Island Lake and the north side of Horseshoe Bend Beach Road. Horseshoe Bend Beach Road runs generally west to east and is located along a local topographic divide. The geology/groundwater conditions at the site are expected to be generally consistent with the characteristics of the conceptual groundwater model developed by LeGrand for the Piedmont region. 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. Duke Energy Carolinas, LLC I Discharge Assessment Plan ��1 Riverbend Steam Station Ash Basin < SECTION 2 -SITE BACKGROUND 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. 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 embankments 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 b migration into open joints in the foundation and abutments. The control of seepage is Y 9 P 1 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 RBSS 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. HDR staff performed site observations within these identified areas as part of NPDES inspections during the reapplication process during multiple site visits from November 2013 through April 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. Duke Energy Carolinas, LLC I Discharge Assessment Plan Riverbend Steam Station Ash Basin SECTION 3 - DISCHARGE ASSESSMENT PLAN 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 "B" 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 Riverbend ash basin is provided within this j 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 • 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 during two nonadjacent quarters. The date of the 6 Duke Energy Carolinas, LLC I Discharge Assessment Plan �� Riverbend Steam Station Ash Basin 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-309.21 0.1 (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 Carolinas, LLC I Discharge Assessment Plan �� Riverbend Steam Station 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 Duke Energy Carolinas, LLC I Discharge Assessment Plan �♦� Riverbend Steam Station 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. o Mountain Island Lake and Ash Basin Sample Collection Method: Water quality samples and in -situ measurements from the Catawba River shall be collected at a location upstream and downstream of the ash basin. Additionally, water samples and in -situ measurements shall be collected from an in -process ash basin location. The grab samples shall be collected from the river and basin's surface (0.3 m) directly into appropriate sample bottles. • 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 2B 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-309.21 0.1 (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 2B 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 Carolinas, LLC I Discharge Assessment Plan Riverbend Steam Station Ash Basin 01 SECTION 4 - REFERENCES Section 4 - References LeGrand, Harry, Sr. 2004. A Master Conceptual Model for Hydrogeological Site Characterization in the Piedmont and Mountain Region of North Carolina, North Carolina Department of Environment and Natural Resources. 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). Pippin, C.G., Chapman, M.J., Huffman, B.A., Heller, M.J., and Schelgel, M.E. 2008. Hydrogeologic setting, ground -water flow, and ground -water quality at the Langtree Peninsula research station, Iredell County, North Carolina, 2000-2005: U.S. Geological Survey Scientific Investigations Report 2008-5055, 89 p. (available online at hftp://pubs.water.usgs.gov/sir2008-5055). 10 � P� yA $ 3 �' ✓�gY ��yra i J.M r 1vank a✓ i� t y k i} 4 Yr f .Ff, %1. 4 , ue f� 1 '1 r CoNX t Y - - ; l � C3`� -- -�! �.: 1. � . 1 - • . 21`� . oy X Q r� C► v. 4 a • , Vp�— •• BASIN i ' n j N 1 : a . ti jPowerplant Substa. •Wat r Ts _ .. / � ,• c. `�- r i)uke flower V ill age :. t ( '.' RIVERBEND STEAM STATION r ; em 16 Rozzelle V r �1 1 Bridge NOTES. t ✓t �'V V �e I. SOURCES: USGS TOPOGRAPHIC MAP - MT. ISLAND LAKE, CREATED 1993. USGS TOPOGRAPHIC MAP - LAKE NORMAN SOUTH, CREATED 1993. SCALE (FEET)*.. \lid`!% 1000 0 1000 2000 Fm HOR Eaai••m9, anN• Catw,as Sawn Ct—h S-1 Ch tte, NC 28 SITE LOCATION MAP RIVERBEND STEAM STATION DUKE ENERGY CAROLINAS, LLC GASTON COUNTY, NORTH CAROLINA DATE SEPTEMBER 30, 2014 FIGURE .IV ASH STORAGE ASH BASIN SECONDARY CELL PRIMARY CELL ' RIVERBENDAA _ STEAM STATION '�' ,.K`ai�' r" NOTES: 1. PARCEL DATA FOR THE SITE WAS OBTAINED FROM DUKE ENERGY REAL ESTATE AND IS APPROXIMATE. SCALE (FEET) 2. TOPOGRAPHY DATA PROVIDED BY DUKE ENERGY. 3. WASTE BOUNDARY IS APPROXIMATE. 500' 0 300' 600' 4. GROUNDWATER MONITORING WELL LOCATIONS PROVIDED BY DUKE ENERGY. S. SEEP SAMPLING LOCATIONS WERE OBTAINED BY HDR USING A TRIMBLE HANDHELD GPS UNIT ON APRIL 29, 2014. �" = 600' 6. WATER QUALITY AND NPDES SAMPLE LOCATIONS WERE PROVIDED BY DUKE ENERGY AND ARE APPROXIMATE. 7. NPDES OUTFALL LOCATIONS WERE PROVIDED BY DUKE ENERGY AND ARE APPROXIMATE. 8. S-10 NOT SAMPLED DUE TO INSUFFICIENT FLOW. 9.' INDICATES SEEP SAMPLING LOCATIONS WERE NOT RECORDED WITH GPS UNIT AND ARE APPROXIMATE. F) m LEGEND: -7D =KGROUND) DUKE ENERGY PROPERTY BOUNDARY WASTE BOUNDARY J' MOUNTAIN ISLAND LAKE BOUNDARY -- TOPOGRAPHIC CONTOUR S-8 • SEEP SAMPLE LOCATION 277.5 • WATER QUALITY SAMPLE LOCATION b!P `' , NPDES 002 A NPDES OUTFALL LOCATION iv -4 >t 4�1 COMPLIANCE GROUNDWATER MONITORING WELL R 0 VOLUNTARY GROUNDWATER MONITORING WELL DISCHARGE SAMPLING LOCATIONS 1-B BACKGROUND SAMPLING LOCATIONS TOPOGRAPHIC MAP WITH IDENTIFIED DATE SEEPS AND OUTFALLS DECEMBER, 2014 DUKE ENERGY CAROLINAS, LLC RIVERBEND STEAM STATION ASH BASIN FIGURE NPDES PERMIT #NC0004961 2 GASTON COUNTY, NORTH CAROLINA Table 1 — Riverbend Steam Station Ash Basin — Seep and Associated Discharge Locations and Descriptions - I . Discharge Location_. Seep / Location Coordinates (NAo s3). Flow Flow Measurement,' Background .' Discharge Location and Discharge Sampling, _ Coordinates . NAU a3) 1. Discharge.: Description" (MGD),andMethad Locations Location to - Latitude Longitude_ Latitude Longitude S-1 35.365 80.967 Continuous 0.163 West of Primary Cell; north of Cinder Storage Area timed -volumetric 1-D 35.366 80.967 S-2 35.365 -80.966 Continuous 0.00056 West of Primary Cell dike timed -volumetric 1-D 00044 West of Secondary Cell downgradient from the toe S-3 35.369 -80.965 Continuous . .volumetric of the Secondary Cell 35.369 -80.966 timed 2-D North of Secondary Cell downgradient from the toe Sd 35.371 80.963 Continuous 0.00562 of the Secondary Cell timed -volumetric 3-D 35.371 -80.963 0.01754 North of the Secondary Cell along the toe slope of S 5 35.370 60.963 Continuous the northern Secondary Cell abutment timed -volumetric 3-D East and downgradient of the ash basin; flowing S� 35.367 80.958 Continuous 0.00287 downgradient timed -volumetric 1-8 4-D East and downgradient of the ash basin; flowing S-7 35.367 -80.957 Continuous 0.02085 downgradient 35.366 80.956 timed -volumetric 4-D S-8 35.365 -80.956 Continuous 0.0332 East of the ash basin and Secondary Cell dike timed -volumetric 4-D 0.0245 0.024 North of the Secondary Cell north abutment near S-9 35.371 -80.963 Continuous timed -volumetric the toe 3-D 35.371 80.963 001206 East of the Secondary Cell dike downstream at the S-10 35.369 -80.960 Intermittent . timed -volumetric toe of the dike 4-D East of the Secondary Cell dike downstream at the S-11 35.369 �0.960 Continuous 0.00835 timed -volumetric toe of the dike 35.366 80.956 4-D At the end of a concrete channel downstream of S-12 35.368 80.959 Continuous 0.00568 the Secondary Cell dike timed -volumetric 4-D Notes: 1. Flow description for each seep sample location is based on multiple site visits performed by HDR from November 2013 until April 2014 2. Flow measurements and analytical samples were collected (except for S-10) on April 29, 2014 Table 2 — Laboratory Analytical Methods -Parameter Method. 'Reporting ; ,Limit' . 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 Ng/I Duke Energy Copper (Cu) EPA 200.8 1 Ng/I Duke Energy Lead (Pb) EPA 200.8 1 Ng/I Duke Energy Nickel (Ni) EPA 200.8 1 Ng/I Duke Energy Selenium (Se) EPA 200.8 1 Ng/I Duke Energy Table 3 - Riverbend Steam Station - Example of Surface Water/Seep Monitoring Flow and Analysis Results Table ... Mountain . Mountain Parameter Units S-1 ` S-2 S-3 S-4 S-5 S-6 ; S-7 �, S-8 S-9 S-11 . S-12 Island - Upstream Island.'- Downstream �, { . Fluoride mg/I < 1 < 1 < 1 < I < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 Hg - Mercury (71900) Ng/I < 0.05 < 0.05 < 0.05 < 0. )05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05. < 0.05 < 0.05 < <0.05 As - Arsenic (01002) Ng/I < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 Cd - Cadmium (01027) pg/l < 1 < 1 < 1 < < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 Cr - Chromium (01034) Ng/l < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 Cu - Copper (01042) Ng/l < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 1.58 1.63 ; 1.68 Pb - Lead (01051) Ng/l < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 Ni - Nickel (01067) Ng/I < 1 < < 1 1 6.76 < < 8.77 1 5.57 < < 1 1 7.98 < 2.47 1 6.29 < < 1 1 7.62 < 2.07 1 6.62 < 1 3.58 6.76 1.48 7 6.38 < 1.1 1 5.9 < 6.33 1 6.02 < < 1 1 7.19 < 1 < 1 7.21 Se - Selenium (01147) Ng/l < 1 pH S.U. 5.9 Temperature °c 15.81 16.8 16.75 84 15�7540.00287 16.49 16.59 15.71 17.23 16.01 15.56 17.53 17.96 117.99 Flow MGD 0.00056 0.0044 0.00562 0.01 0.02085 0.0332 0.0245 0.01206 0.00835 0.00568 N/A N/A Notes: 1. Flow measurements and analytical samples were collected on April 29, 2014 2. N/A indicates not applicable 3. Flow was not exhibited at S-10 during the time of seep sampling Central Files: APS _ SWP _ 12/20/2019 Permit Number WQ0041367 Program Category Non -discharge Permit Type Gravity Sewer Extension, Pump Stations, & Pressure Sewer Extensions Primary Reviewer barry.love Coastal SWRuIe Permitted Flow 1,330 Facility Facility Name Greyson Ridge 9 - Lots Location Address Owner Owner Name J & J Custom Homes LLC Dates/Events Permit Tracking Slip Status Project Type Active New Project Version Permit Classification 1.00 Individual Permit Contact Affiliation Major/Minor Region Minor Mooresville County Mecklenburg Facility Contact Affiliation Owner Type Non -Government Owner Affiliation Claudia AI -Hassan 2920 Old Monroe Rd Wesley Chapel NC 28104 Scheduled Orig Issue App Received Draft Initiated Issuance Public Notice Issue Effective Expiration 12/20/2019 12/18/2019 12/20/2019 12/20/2019 Regulated Activities Requested /Received Events Subdivision Additional information requested Wastewater collection Additional information received Outfall Waterbody Name Streamindex Number Current Class Subbasin