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Home My WebLink AboutNC0022406_AshBasinPumpingTest_WorkPlan_20180712 ASH BASIN PUMPING TEST WORK PLAN AT BELEWS CREEK STEAM STATION 3195 PINE HALL ROAD BELEWS CREEK, NORTH CAROLINA 27009 PREPARED FOR DUKE ENERGY CAROLINAS, LLC Christopher H. Bruce, NC LG 2246 Sr. Geologist Craig D. Eady, NC LG 1599 Project Manager Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra Page i \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx TABLE OF CONTENTS SECTION PAGE 1.0 INTRODUCTION ......................................................................................................... 1-1 2.0 SITE CONCEPTUAL MODEL ................................................................................... 2-1 2.1 Site Geology and Hydrogeology ............................................................................ 2-1 2.1.1 Site Geology ......................................................................................................... 2-1 2.1.2 Site Hydrogeology .............................................................................................. 2-1 3.0 WELL INSTALLATION .............................................................................................. 3-1 3.1 Installation of Pumping and Observation Wells .................................................. 3-1 3.1.1 Ash Pumping Well Installation ......................................................................... 3-1 3.1.2 Saprolite Pumping Well Installation ................................................................ 3-2 3.1.3 Ash Observation Well Installation ................................................................... 3-2 3.2 Well Development .................................................................................................... 3-3 4.0 AQUIFER PUMP TEST DATA NEEDS.................................................................... 4-1 5.0 AQUIFER PUMPING TEST ....................................................................................... 5-1 5.1 Static Water Level Collection .................................................................................. 5-1 5.2 Pumping System Installation .................................................................................. 5-1 5.3 Step-Drawdown Tests .............................................................................................. 5-2 5.4 Step Test Recovery .................................................................................................... 5-2 5.5 Constant-Rate Pumping Test .................................................................................. 5-3 6.0 WATER-QUALITY MEASUREMENTS AND SAMPLING ................................. 6-1 7.0 ANALYSIS OF WATER-LEVEL DATA ................................................................... 7-1 7.1 Baseline Analysis....................................................................................................... 7-1 7.2 Step Test Analysis ..................................................................................................... 7-1 7.3 Constant Discharge Rate Test Analysis ................................................................. 7-1 8.0 REFERENCES ................................................................................................................ 8-1 Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra Page ii \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx LIST OF FIGURES Figure 1-1 Site Location Map Figure 3-1 Proposed Location for Ash Basin Pumping Tests Figure 5-1 Typical Flow Meter Configuration Figure 5-2 Typical Step Test Drawdown Curve LIST OF TABLES Table 3-1 Proposed Well Construction Details Table 5-1 Proposed Wells to be Monitored During Ash Basin Pumping Test LIST OF APPENDICES Appendix A Boring Logs for AB-4 and AB-5 Well Clusters Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra Page 1-1 \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx 1.0 INTRODUCTION Duke Energy Carolinas, LLC (Duke Energy) owns and operates the Belews Creek Steam Station (BCSS), which is located on Belews Reservoir in Belews Creek, Stokes County, North Carolina (Figure 1-1). BCSS began operation in 1974 as a coal-fired generating station and currently operates two coal-fired units with 2,240 megawatt capacity of generation. Coal combustion residuals (CCR) have historically been managed in the Site’s ash basin (surface impoundment) located north of Pine Hall Road to the west- northwest of the station. CCR were initially deposited in the ash basin by hydraulic sluicing operations. In 1984, BCSS converted from a wet to a dry fly ash handling system. However, the ability to sluice to the ash basin is still available, but limited to certain situations (i.e. unit startup/shutdown, equipment maintenance and service). Construction of a 100% dry ash handling system has been completed onsite. The dry ash handling system is operational but not all components to sluice to the ash basin have been decommissioned. The decommissioning activities will be completed in the Fall of 2018. Detailed descriptions of the Site operational history, the Site conceptual model, physical setting and features, geology/hydrogeology, and results of the findings of the CSA and other CAMA-related works are documented in full in the following documents: • Comprehensive Site Assessment Report – Belews Creek Steam Station Ash Basin (HDR Engineering, Inc. of the Carolinas (HDR, 2015a). • Corrective Action Plan Part 1 – Belews Creek Steam Station Ash Basin (HDR, 2015b). • Corrective Action Plan Part 2 (included CSA Supplement 1 as Appendix A) – Belews Creek Steam Station Ash Basin (HDR, 2016d). • Comprehensive Site Assessment Supplement 2 – Belews Creek Steam Station Ash Basin (HDR, 2016c). • Basis of Design Report (100% Submittal) – Belews Creek Steam Station (SynTerra, 2017a). • Comprehensive Site Assessment Update – Belews Creek Steam Station Ash Basin (SynTerra, 2017). Ash basin pumping tests are planned to collect site specific data to refine the groundwater flow and transport model to be used for closure planning and potential Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra Page 1-2 \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx groundwater corrective action evaluation. The pumping tests would focus on evaluation of field scale horizontal and vertical variability of the hydrologic characteristics for the saturated media. Each test would provide estimates of media properties including transmissivity (T), hydraulic conductivity (K), and storativity (S). The following major tasks are anticipated for well installation and ash basin pumping test at the BCSS: 1. Well Installation and Development 2. Static Water Level (Baseline Data) Collection 3. Pumping System Installation 4. Step-Drawdown Tests 5. Step Drawdown Test Recovery 6. Constant Rate Pumping Tests 7. Water Quality Sampling 8. Data Analysis As a portion of this scope of work, both pumping wells and observation wells will be installed at the Site. A total of one ash pumping well and one saprolite pumping well will be installed. A total of four new observation wells will also be installed. Additionally, six existing wells will be utilized as observation points during the ash and saprolite pumping tests. One pumping test is estimated to take eight (8) days (72 hours for static conditions, 24 hours for step test/recovery, 72 hours for constant rate discharge test, 24 hours recovery). During this time, water levels would be monitored in selected wells using pressure transducers and manual water level readings. Groundwater samples will also be collected daily during the pumping test for laboratory analysis. Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra Page 2-1 \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx 2.0 SITE CONCEPTUAL MODEL 2.1 Site Geology and Hydrogeology This section provides a brief summary of the Site geology and hydrogeology. However, it should be noted that the scope of the aquifer pumping tests will be limited to the ash and underlying saprolite in the inactive ash basin. 2.1.1 Site Geology Geology beneath the BCSS site can be classified into three units. Regolith (surficial soils, fill and reworked soil, and saprolite) is the shallowest geologic unit. A transition zone of partially weathered rock underlies the regolith (where present, the saprolite is the lowest portion of the regolith) and is generally continuous throughout the BCSS site. The third unit, competent bedrock, is defined by rock core recovery, RQD and the degree of fracturing in the rock. Typically, mildly productive fractures (providing water to wells) were observed within the top 50 feet of competent rock. In general, three hydrogeologic units or zones of groundwater flow can be described for the BCSS Site. The zone closest to the surface is the shallow flow layer encompassing saturated conditions, where present, in the residual soil or saprolite beneath the Site. A transition zone (deep flow layer) is encountered below the shallow flow layer and above the bedrock, is characterized primarily by partially weathered rock of variable thickness. The bedrock flow layer occurs below the transition zone and is characterized by the storage and transmission of groundwater in water-bearing fractures. The BCSS site and its associated ash basin are located in the Milton terrane. The Milton terrane is characterized by strongly foliated gneisses and schists, commonly with distinct compositional layering and felsic composition; quartzite, calc-silicate gneiss, hornblende gneiss and schist, and marble are minor units (Carpenter III, 1982); (Butler & Secor, 1991); (Schaeffer, 2001)). The majority of the rocks in the belt are metamorphosed to the sillimanite and kyanite grade of amphibolite metamorphism (Butler & Secor, 1991). The Dan River Triassic Basin is located approximately 3,000 feet north of the site. 2.1.2 Site Hydrogeology According to LeGrand, the soil/saprolite regolith and the underlying fractured bedrock represent a composite water-table aquifer system (LeGrand 2002). The regolith provides the majority of water storage in the Piedmont province, with porosities that range from 35 to 55 percent (Daniel & Dahlen, 2002). Calculated Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra Page 2-2 \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx porosities specific to the Site (43.4% to 47.3%) are consistent with this range. Two major factors that influence the behavior of groundwater in the vicinity of the Site include the thickness (or occurrence) of saprolite/regolith and the hydraulic properties of underlying bedrock. Saprolite thickness varies across the Site but is generally thickest in upgradient areas (20 to 60 feet for GWA-8S and MW-202S) and thins in downgradient areas near the Dan River (5 to 12 feet for GWA-24S and MW-200S). Based on the site investigation, the groundwater system in natural materials (soil, soil/saprolite, and bedrock) at the BCSS site is consistent with the regolith- fractured rock system and is an unconfined, connected aquifer system. Regolith is underlain by a transition zone (TZ) of weathered rock which transitions to competent bedrock. The groundwater system at the BCSS site is divided into three flow layers referred to in this report as the shallow, deep (TZ), and bedrock layers, so as to distinguish unique characteristics of the connected aquifer system. Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra Page 3-1 \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx 3.0 WELL INSTALLATION SynTerra will conduct field oversight of drilling operations and well installations at the proposed test locations. SynTerra’s oversight will include documentation of field observations and activities associated with well drilling, well installation and well development activities conducted by a licensed North Carolina driller and support crew contracted by Duke Energy. Proposed pumping well and observation well locations and a conceptual well layout and cross-sectional view are provided on Figures 3-1. A summary of proposed well construction details for the pumping wells and observation wells is included in Table 3- 1. Proposed well depths and screened intervals are based on boring logs from the adjacent well cluster AB-4 and AB-5. Boring logs form these locations have been included as Appendix A. 3.1 Installation of Pumping and Observation Wells Prior to the start of any drilling activities at the Site, subsurface utility location will be conducted in the area of all proposed borings. 3.1.1 Ash Pumping Well Installation The ash pumping well will be installed using sonic drilling techniques with a nominal 13 inch sonic core barrel. This well will be located approximately 30 feet away from existing clusters AB-4 and will be drilled to approximately 65 feet below ground surface (bgs), Table 3-1. At each location a six-inch schedule 40 PVC well, with a 10-foot wire-wrapped 0.10 slot PVC screen will then be installed in the boring. The well screen will be positioned approximately one foot off the bottom of the boring (to allow filter material below the well screen). No. 1 well sand or equivalent filter pack materials will be used. The filter pack material will be tremie washed in if there is standing water in the bore hole (not anticipated with sonic drilling). The filter pack will be extended from the base of the boring to a minimum of five feet above screen interval. Coated bentonite pellets will be used for the seal and extend a minimum of five feet above the sand pack. Pellets will be allowed to hydrate for in accordance with manufactures specifications before grouting. After hydration of the seal, the remaining annulus will be pressured grouted using a 1-2 percent bentonite 90 percent neat cement mixture (grout mixing should be 5.2-5.75 gallons of water per 94 pound bag of Portland Type cement). Where a well is installed within 15 Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra Page 3-2 \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx feet of an existing monitoring well location, a low pH grout, such as AQUAGUARD, should be used. The use of this type of grout is intended to reduce the potential for grout impacts on existing or nearby monitoring wells. 3.1.2 Saprolite Pumping Well Installation One saprolite pumping well will be installed at the AB-4 well cluster location (adjacent to the ash pumping well). This well will be installed using sonic drilling techniques utilizing a nominal 13-inch sonic core barrel drilled to a minimum of three feet into the underlying saprolite material (assumed to be at 66 feet bgs). The nominal 13-inch sonic core barrel will serve as a temporary outer casing. Once the outer core barrel is in place, an inner nominal 10-inch boring will be advanced to a total depth of 90 feet bgs. A six-inch schedule 40 PVC well, with a 10-foot wire-wrapped PVC screen will then be installed in the boring. One well centralizer will be installed directly above the screened interval. The well screen will be positioned approximately one foot off the bottom of the boring (to allow filter material below the well screen). No. 1 well sand or equivalent filter pack materials will be used. The filter pack will be extended from the base of the boring to a minimum of five feet above screen interval. Coated bentonite pellets will be used for the seal and will extend up to the ash saprolite interface. Pellets will be allowed to hydrate in accordance with manufactures specifications before grouting. The remaining annulus will be pressured grouted (for grout specifications see Section 3.1.1). 3.1.3 Ash Observation Well Installation A total of four ash observation wells will be installed at the site at the existing AB-4 well cluster location. These wells will be located at 15 feet and 30 feet away from the pumping well. Distance from the pumping well for each observation well is provided on Table 3-1. Ash observation wells will be installed using sonic drilling techniques utilizing a nominal six-inch (or equivalent) core barrel advanced to the target depth (see Table 3-1). A two inch schedule 40 PVC well, with a five-foot Vee-Pack PVC screen will then be installed in the boring. The well screen will be positioned approximately one foot off the bottom of the boring (to allow filter material below the well screen). Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra Page 3-3 \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx No. 1 (or equivalent) filter pack will be extended from the base of the boring to a minimum of five feet above Vee-Pack screen interval. Coated bentonite pellets will be used for the seal. The well seal will be extended a minimum of five feet above the sand pack. Pellets will be allowed to hydrate in accordance with manufactures specifications before grouting. After hydration of the seal, the remaining annulus will be pressured grouted (for grout specifications see section 2.1.1). 3.2 Well Development The newly installed wells will be developed until discharge is clear and stable. Well development should include surging and high volume water removal (air lifting or other methods capable of quickly removing water). Completion of development will be determined when turbidity remains below 10 Nephelometric Turbidity Units (NTUs) or 5 borehole volumes have been extracted (subject to change based on field observations). The main objective of the well development is to improve near-well permeability and stability. The removal of the fine particles from the near-well area will help create a more permeable zone and minimize the effect of borehole smear or caking. Improper well development can cause significant impact to the results of both the step test and the constant rate discharge test. This could result in the need to stop the test (step test or constant rate test) and redevelop the wells (primarily pumping wells). Well development for the pumping wells will be considered complete when no fines are observed in the well discharge (less than 10 NTUs) after surging the well. Once the wells have been fully developed, they will be allowed to equilibrate for five days prior to the collection of baseline water level data. Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra Page 4-1 \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx 4.0 AQUIFER PUMP TEST DATA NEEDS Aquifer pumping test results will be used to define aquifer characteristics within the ash basin. Information gathered during aquifer pumping tests will be used to refine the groundwater flow and transport model. Three-day (72 hours) tests will allow for evaluation of aquifer properties. Evaluation of data in the field will ultimately be used to determine the durations. Each test will be conducted in general accordance with ASTM D 4050-96 (2002). The following pretest data is needed: • Geologic characteristics of the subsurface that influence groundwater flow. The subsurface in the area of the pumping test is composed of ash, saprolite, transition zone, and bedrock. The aquifer testing will be limited to the ash and shallow saprolite. Groundwater flow in the ash and saprolite aquifer (primary test aquifer) is porous media flow. It is assumed that groundwater flow direction and gradients are primarily controlled by topography. • The type of water-bearing zone and its lateral and vertical extent. The primary water-bearing zone for the aquifer test is the ash and shallow saprolite directly underlying the ash basin. For the purpose of this test, it is assumed to be infinite in lateral and vertical extent. • The depth, thickness, and lateral extent of any confining beds. Observations will be made during drilling operations to identify any confining beds. It is currently unknown whether the lower ash and or saprolite wells will indicate water table conditions, partially confined conditions, or confined conditions. • Location of groundwater recharge. Groundwater recharge is assumed to be primarily from the ash basin area. • Horizontal and vertical flow components (e.g., direction, gradient). Water levels will be measured in the ash and saprolite monitoring wells to determine the horizontal and vertical hydraulic gradient in the area of the aquifer test. Additionally, the multi-level well screens will provide information on potential stratification within the ash. • Location, construction, and zone of completion of existing wells in the area (see Table 1). Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra Page 5-1 \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx 5.0 AQUIFER PUMPING TEST 5.1 Static Water Level Collection Static water level (baseline data) collection may commence once the pumping wells and observation wells have been installed, developed, and allowed to equilibrate (for approximately five days). Baseline water-level readings will be used to determine long- term data trends or potential interferences from other pumping/discharge source(s). Water levels will be monitored in selected wells using pressure transducers. A summary of the wells to be monitored for each test is included as Table 5-1. Transducers will be installed in all proposed observation well at the site. Prior to the installation of transducers, an initial round of water levels will be manually collected from the wells listed in Table 5-1. Transducers will then be installed and programmed to collect water level data every 10 minutes for a minimum of 72 hours before the start of any active pumping (step test). At the end of the 72-hour period, baseline measurements would be stopped and downloaded for review. 5.2 Pumping System Installation Once baseline conditions have been established, a submersible pump would be installed in the selected pumping well by the Duke well installation contractor. The initial test will be conducted in the saprolite pumping well at the AB-4 cluster. Following the completion of testing at this location, the ash pumping well at the AB-4 cluster will be tested. The Duke well installation contractor will provide and install a flow meter capable of continuously-logging discharge rates and total flow in-line with the pump discharge line. The flow meter will need to be installed in such a way as to allow it to be full of water at all times. This can be done by the installation of a six-inch drop in the discharge line prior to the flow meter and a subsequent 6 inch rise in the discharge line past the flow meter. A minimum of one foot of straight piping will also need to be installed after the drop and before the rise to ensure laminar flow through the transducer. Two ball valves should be installed in the discharge line. One should be located prior to the drop and one should be located post rise. A photograph showing the general proposed configuration for the flow meter is presented on Figure 5-1. A small diameter sampling port should also be installed somewhere near the flow meter to allow for taking field water quality measurements and samples. The remaining discharge line should be extended away from the test area (300-500 feet) to minimize potential influence of the discharged groundwater. Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra Page 5-2 \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx 5.3 Step-Drawdown Tests After the pumping system has been installed the well will be allowed to fully recover (assumed to be 12 hours). Once the pumping well has fully recovered, SynTerra in conjunction with the drilling contractor will conduct a step-drawdown test (initial test in AB-4 saprolite pumping well). A typical step test drawdown curve is presented in Figure 5-2. A step-drawdown test (or step test) is a single-well pumping test designed to investigate the performance of a pumping well under controlled variable discharge conditions. During the step-drawdown test, an initial rate of one gallon per minute (gpm) would be used. The discharge rate would be increased approximately five gpm per step period (subject to change based on field observations). Each step would be approximately 2 hours (subject to change based on field observations). This duration should allow wellbore storage effects to dissipate. This process would continue until the well can no longer sustain the selected flow rate (curve does not flatten out) or a maximum of 20 gpm flow rate is reached. After completion of the step test, the pumping well would be allowed to return to static conditions (recovery tests). Data from the step test will be used to determine an appropriately conservative initial pumping rate (Qmax) for the constant rate pumping tests. A Qmax should be calculated that will result in a drawdown after 72 hours that is approximately 25 percent of the water column (see Section 5.2). At the end of the test the flow will be adjusted to the selected Qmax using one of the ball valves prior to shutting down the pump. As the pump is shut down the remaining ball valve will be closed to prevent the discharge line from draining into the well (which would affect recovery data). After the completion of the initial set of 72-hour pumping test and recovery, the pump will be moved to the second test location (AB-4 ash pumping well). A second step test will be conducted at following the same procedure. 5.4 Step Test Recovery Once the each step test is complete, the pump will be shut off and the flow meter will be isolated (using ball valves upstream and downstream of the flow meter). The well will be allowed to fully recover prior to the start of the constant discharge test. It is anticipated that recovery will take less than 12 hours. Water levels will continue to be monitored at the same frequency during recovery. Once recovery is complete, the transducer water-level readings will be stopped and the data downloaded and analyzed. Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra Page 5-3 \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx 5.5 Constant-Rate Pumping Test Once the step-drawdown test has been completed and water levels in the pumping well and affected observation wells have returned to static conditions and transducers have been stopped and reprogramed, a constant-rate pumping test will be conducted at each location (initial location will be AB-4 saprolite pumping well followed by and AB-4 ash pumping). Prior to the start of any active pumping a round of water levels will be collected in the monitored wells for each test location (see Table 3-1) A constant-rate pumping test involves a control well that is pumped at a constant rate while water-level response (drawdown) is measured in one or more surrounding observation wells and in the pumping well. Goals of a constant-rate pumping test are to estimate hydraulic properties of a saturated porous media such as T, K, and S and to identify potential boundary conditions that may exist. Discharge rate would be measured approximately every 15 minutes during the initial portion of the test (first four hours). If discharge rate is stable, flow readings will be collected at 8-hour intervals for the remainder of the test. Water level transducers will be set to record measurements every minute for the duration of the 72-hour test and recovery period. Discharge water will be routed to the active ash basin in the approximate locations depicted on Figures 3-1. Once pumping has started, the test will run uninterrupted for up to 72 hours. During that period, water-levels will be continuously monitored with data logging pressure transducers and flow measurements continuously recorded (24 hours per day) with an electronic flow meter that averages measurements at five minute intervals. Manual water-level readings would be collected every two hours at each selected well during active pumping to provide automated data backup (see Table 5-1). Manual water-level readings will also be collected twice daily at designated observation monitoring wells. Manual flow measurements may be conducted based on field observations, as described earlier in this section. Ground water quality field readings and laboratory samples will be collected from the discharge at selected intervals during active pumping (see Section 4.0). Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra Page 6-1 \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx 6.0 WATER-QUALITY MEASUREMENTS AND SAMPLING In order to help identify the potential geochemical changes that may occur in the ash pore water during the active pumping, water-quality data will be collected during each pumping test. Water-quality data will include the collection of both field reading and laboratory samples. Particular emphasis will be placed on collection of conductivity and pH data. Changes in water chemistry (conductivity and pH) may indicate contact with a recharge boundary. Groundwater samples will be collected from the pumping well discharge and analyzed for IMP constituent list. Water-quality measurements will be collected from the discharge during the entire constant rate discharge test. Readings of pH, specific conductance, temperature, dissolved oxygen, oxidation reduction potential, Eh, and turbidity will be collected once every hour during the test. To facilitate this, a YSI Pro Plus water-quality meter will be plumbed into the discharge line. Flow through the meter will be regulated with both upstream and downstream valves. Water-quality samples for laboratory analysis will be collected prior to the step- drawdown test and once per day during the constant rate pumping test from each of the pumping wells. Each sample will be collected from a sampling port plumbed into the discharge line. Water will be collected in laboratory-prepared sample bottles and immediately placed on ice under strict chain-of-custody. Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra Page 7-1 \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx 7.0 ANALYSIS OF WATER-LEVEL DATA Analysis of water-level fluctuations in monitoring wells will be initially conducted using Aqtesolv® Version 4.5. Baseline data, step test data, constant rate discharge data (pumping test), drawdown data, and analytical results will be summarized and included as part of a technical memorandum on the results of aquifer testing. 7.1 Baseline Analysis Baseline data will be evaluated to determine whether any long-term trends or interference from nearby production wells are observable. If long-term data trends are observed, the baseline data will be used to adjust the pumping test drawdown data to compensate for the observed trend. 7.2 Step Test Analysis Step test analysis will be conducted in the field. The Theis (1935) step-drawdown procedure will be used to analyze data. Additional analytical methods (Dougherty- Babu, 1984; Hantush-Jacob, 1955; Theis, 1935; and Hantush, 1961) may be used depending on results of the step test drawdown data. Step test results will be used to calculate a flow rate that will result in a drawdown of approximately 25 percent of the saturated thickness after 72 hours (and excel spread sheet will be provided for making these calculations). 7.3 Constant Discharge Rate Test Analysis Final analysis methods of drawdown data are dependent on actual results of the tests. Initially, it is assumed that the proposed ash pumping well is unconfined and the saprolite pumping well may be unconfined, semi-confined or confined. Additionally, drawdown may be observed only in the pumping well. This will result in analysis of the data as a single-well pumping test. If data indicates drawdown in one or more observation well, the test will be analyzed as a multiple-well pump test. Suggested analytical methodologies for data analysis of both single-well and multiple-well pump tests are outlined in the Technical Guidance Manual for Hydrogeologic Investigations and Groundwater Monitoring, Chapter 4, Slug and Pumping Test, Table 4.2 (single-well pump test) and Table 4.7 (multiple-well pump test) (Clemson, February 1995) at: http://www.clemson.edu/ces/hydro/murdoch/PDF%20Files/Pumping%20tests,%20EPA %20guidance.pdf Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra Page 8-1 \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx 8.0 REFERENCES Daniel, C. C., & Dahlen, P. R. (2002). Preliminary hydrogeologic assessment and study plan for a regional ground-water resource investigation of the Blue Ridge and Piedmont provinces of North Carolina. Raleigh, North Carolina: U.S. GEOLOGICAL SURVEY Water- Resources Investigations Report 02–4105. Dougherty, D.E and D.K. Babu, 1984. Flow to a partially penetrating well in a double porosity reservoir, Water Resources Research, vol. 20, no. 8, pp. 1116-1122. Hantush, M.S. and C.E. Jacob, 1955. Non-steady radial flow in an infinite leaky aquifer, Am. Geophys. Union Trans., vol. 36, pp. 95-100. Hantush, M.S., 1961b. Aquifer tests on partially penetrating wells, Jour. of the Hyd. Div., Proc. of the Am. Soc. of Civil Eng., vol. 87, no. HY5, pp. 171-194. LeGrand, H. (2004). A master conceptual model for hydrogeological site characterization in the Piedmont and Mountain Region of North Carolina: A guidance manual. North Carolina Department of Environment and Natural Resources, Division of Water Quality, Groundwater Section, Raleigh, NC, 55. Theis, C.V., 1935. The relation between the lowering of the piezometric surface and the rate and duration of discharge of a well using groundwater storage, Am. Geophys. Union Trans., vol. 16, pp. 519-524. Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx FIGURES STRUCTURAL FILL POWER PLANT ASH BASIN PINE HALLROAD LANDFILL ASH BASINMAIN DAM PARCEL LINE DAN RIVER CRAIG ROADLANDFILL FGD LANDFILL PARCEL A DRAWN BY: B. YOUNGCHECKED BY: A. ALBERTPROJECT MA NAGER: C. EADY 148 RIVER STREET, SUITE 220GREENVILLE, SOUTH CAROLINA 29601PHONE 864-421-9999www.synterracorp.comP:\Duke Energy Progress.1026\00 GIS BASE DATA\Belews Creek Steam Station\MapDocs\IAP\_Fig01-01_Belews_IAP_SiteLocation.mxd FIGURE 1-1SITE LOCATION MAPBELEWS CREEK STEAM STATIONDUKE ENERGY CAROLINAS, LLCSTOKES COUNTY, NORTH CAROLINA SOURCE:2016 USGS TOPOGR APHIC MAP, BELEW S LAKE QU ADRAN GLE, OBTAINED FROM THE USGS STORE AThttps://store.usgs.gov/map-locator. 1,000 0 1,000 2,000 GRAPHIC SCALE IN FEET ! ! ! DATE: 7 /10/2018CONTOUR INTERVAL: 20 FTMAP DATE: 2016 DRAWN BY: B. YOUNGPROJECT MA NAGER: C. EADY STOKESCOUNTY ASHEVILLE CHARLOTTE WINSTON-SALEM CHEC KED BY: A. ALBERT SW-AB5SW-AB4AB-5SLAB-5DAB-4DAB-4SLAB-4SAB-8DMW-203DMW-203SMW-203BRGWA-16SMW-204DGWA-16BRAB-5SAB-4BRDAB-4BRAB-8SLAB-8SGROUNDSURFACE10 BGS100200 20 BGS30 BGS40 BGS50 BGS60 BGS70 BGS80 BGS90 BGS100 BGSGROUNDSURFACE10 BGS20 BGS30 BGS40 BGS50 BGS60 BGS70 BGS80 BGS90 BGS100 BGSAB-4SAPROLITEASHTRANSITION ZONE30006/27/2018 4:16 PMP:\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Figures\BELEWS FIG 3-1 (ASH BASIN PUMP TEST).dwg148 RIVER STREET, SUITE 220GREENVILLE, SOUTH CAROLINA 29601PHONE 864-421-9999www.synterracorp.comFIGURE 3-1PROPOSED LOCATIONS FORASH BASIN PUMPING TESTSBELEWS CREEK STEAM STATIONDUKE ENERGY CAROLINAS, LLCBELEWS CREEK, NORTH CAROLINABELEWS CREEK STEAM STATION3195 PINE HALL RDBELEWS CREEK, NORTH CAROLINADUKEENERGYCAROLINASPROJECT MANAGER:LAYOUT:DRAWN BY:CRAIG EADYDATE:J CHASTAINLayout106/26/181000100200GRAPHIC SCALEIN FEETAB-4 CLUSTER(ASH PUMPING TEST) ASH PUMPING WELL (30 FEET FROM AB-4 CLUSTER) SCREENED 56-66 FEET BGS 6-INCH WIRE WRAPPED PVC SCREEN 6-INCH WELL PVC CASINGOBSERVATION WELLS CLUSTERSET 15 FEET FROM PUMPING WELL 2-INCH WELL UPPER ASH (SCREENED 15-20 FEET BGS) MEDIUM ASH (SCREENED 35-40 FEET BGS) LOWER ASH (SCREENED 60-65 FEET BGS)SET 30 FEET FROM PUMPING WELL 2-INCH WELL UPPER ASH (AB-4S) MEDIUM ASH (SCREENED 35-40 FEET BGS) LOWER ASH (AB-4SL)CONCEPTUAL PROPOSED PUMPING TESTWELL SCHEMATICPROPOSED ASHPUMPING WELLPROPOSED MEDIUMASH WELLSPROPOSED LOWERASH WELLSCONCEPTUAL LAYOUT, ACTUAL LOCATIONS FORPUMPING WELLS AND OBSERVATION WELLS WILLBE FIELD VERIFIEDAB-4BRWELL IN BEDROCKAB-4SLWELL IN ASH PORE WATERASH BASIN WASTE BOUNDARY (APPROXIMATE)LEGENDBGSBELOW GROUND SURFACEPROPOSED UPPERASH WELLSAB-4DWELL IN TRANSITION ZONEPROPOSED SAPROLITEPUMPING WELLEXISTING AB-4SEXISTING AB-4SLSAPROLITE WELL(AB-4SAP)A TOTAL OF TWO PUMPING TESTS WILL BE CONDUCTED AT THIS LOCATION.ONE WILL BE IN THE ASH AND A SECOND WILL BE IN THE UNDERLYINGSAPROLITE.EXISTING AB-4DAB-4 CLUSTER(SAPROLITE PUMPING TEST) SAPROLITE PUMPING WELL (30 FEET FROM AB-4 CLUSTER) SCREENED 78-88 FEET BGS 6-INCH WIRE WRAPPED PVC SCREEN 6-INCH WELL PVC CASING 10-INCH CASING FROM 0-70 FEET BGSOBSERVATION WELLSET 15-30 FEET FROM PUMPING WELL 2-INCH WELL AB-4SAP (SCREENED 75-85 FEET BGS)WELL IN SAPROLITEAB-4SAPAB-4SAP (PROPOSED)PROPOSED PUMPING WELL (ASH PORE WATER)PROPOSED OBSERVATION WELL (LOWER ASH PORE WATER)PROPOSED OBSERVATION WELL (UPPER ASH PORE WATER)PROPOSED PUMPING WELL (SAPROLITE)PROPOSED OBSERVATION WELL (MEDIUM ASH PORE WATER)DISCHARGE LINE P:\Duke Energy Carolinas\21. CLIFFSIDE\06.EHS-CAMA Compliance Support And Corrective Action\Assessment\Aquifer Pumping Tests\Work Plan\Workplan 5_4_2018\DWG\FIGURE 5 Flow Meter.dwg148 RIVER STREET, SUITE 220GREENVILLE, SOUTH CAROLINA 29601PHONE 864-421-9999www.synterracorp.comFIGURE 5-1TYPICAL FLOW METERCONFIGURATIONBELEWS CREEK STEAM PLANTDUKE ENERGY CAROLINAS, LLCBELEWS CREEK, NORTH CAROLINAFLOW METERFLOW METER CONFIGURATIONDISCHARGE LINEBALL VALVEBALL VALVERise -post flow meterLAMINAR FLOW SECTIONS(12-INCHES PER AND POST METER)FLOW DIRECTIONTHIS SHOWS THE GENERAL CONFIGURATION OF THE DISCHARGE LINE AND FLOW METER.FLOW METER TYPE MAY VARY BUT SHOULD FOLLOW THIS GENERAL CONFIGURATION.PROJECT MANAGER:LAYOUT:DRAWN BY:DATE:CHRIS BRUCEFigure 306/27/18SCOTT SPINNER P:\Duke Energy Carolinas\21. CLIFFSIDE\06.EHS-CAMA Compliance Support And Corrective Action\Assessment\Aquifer Pumping Tests\Work Plan\Workplan 5_4_2018\DWG\Figure 6.dwgSOURCE:MLU (Multi-Layer Unsteady state) http://www.microfem.nl/products/mlu.html148 RIVER STREET, SUITE 220GREENVILLE, SOUTH CAROLINA 29601PHONE 864-421-9999www.synterracorp.comPROJECT MANAGER:LAYOUT:DRAWN BY:DATE:CHRIS BRUCEFigure 406/27/18FIGURE 5-2TYPICAL STEP TESTDRAWDOWN CURVEBELEWS CREEK STEAM PLANTDUKE ENERGY CAROLINAS, LLCBELEWS CREEK, NORTH CAROLINA"FLAT" PORTION OF CURVE"STEP" PORTION OF CURVERECOVERY PORTION OF CURVEPumping Period 1, Layer: 1Pumping Period 2, Layer: 1Pumping Period 3, Layer: 1Pumping Period 4, Layer: 1Pumping Period 5, Layer: 1Pumping Period 6, Layer: 1Pumping Period 7, Layer: 1Pumping Period 1Pumping Period 1Pumping Period 1Pumping Period 1Pumping Period 1Pumping Period 1Recovery PeriodSTEP DRAWDOWN TESTSCOTT SPINNER Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx TABLES TABLE 3-1 PROPOSED WELL CONSTRUCTION DETAILS BELEWS CREEK STEAM STATION DUKE ENERGY CAROLINAS, LLC, BELEWS CREEK, NC P:\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Table 3-1 Well Construction_BC.xlsx Page 1 of 1 Identification Well Purpose Distance from Pumping Well (Feet) Monitoring Zone Borehole Diameter (Inches) Diameter (inches) Casing Depth (Feet BGS) Casing Diameter (Inches) Total Well Depth1 (Feet BGS) Screen Length (Feet) Ash Basin AB-4S (Existing)Observation TBD Upper Ash NA 2 NA NA 18 15 AB-4SL (Existing)Observation TBD Lower Ash NA 2 NA NA 61.3 10 AB-4D (Existing)Observation TBD Transition Zone NA 2 88 NA 94.5 5 AB-4SAP (Existing)Observation TBD Saprolite NA 2 70 NA 85 10 AB-4 Ash Well Pumping NA Lower Ash 18 6 NA NA 65 10 AB-4 Saprolite Well Pumping NA Saprolite 13.25 to 70 ft 10 to 90 ft 6 70 13.25 (temporary)90 10 AB-4 Upper Ash Observation 15 Upper Ash 6.25 2 NA NA 20 5 AB-4 Medium Ash Observation 15 Medium Ash 6.25 2 NA NA 40 5 AB-4 Lower Ash Observation 15 Lower Ash 6.25 2 NA NA 65 5 AB-4 Medium Ash Observation 30 Medium Ash 6.25 2 NA NA 40 5 AB-5S (Existing)Observation TBD Upper Ash NA 2 NA NA 18 15 AB-5SL (Existing)Observation TBD Upper Ash NA 2 NA NA 44 10 Prepared by: CHB Checked by: CDE Notes: Proposed depths and well construction details are approximate and subject to change based on field observations Bold - Indicates Proposed Wells 1"Total Well Depth" is the depth to the bottom of the screened interval, as measured during well installation. BGS - Below ground surface NA - Not applicable TBD - to be determined TABLE 5-1 PROPOSED WELLS TO BE MONITORED DURING ASH BASIN PUMPING TEST BELEWS CREEK STEAM STATION DUKE ENERGY CAROLINAS, LLC, BELEWS CREEK, NC P:\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\ Table 5-1 Proposed Pumping Test Wells.xlsx Page 1 of 1 Step Test (Ash) Pumping Test (Ash) Step Test (Saprolite) Pumping Test (Saprolite) AB-4S X X X AB-4SL X X X AB-4D X X X AB-4SAP X X X AB-4 Ash Pumping Well X X X X AB-4 Saprolite Pumping Well X X X X AB-4 Upper Ash (15 feet)X X X AB-4 Medium Ash (15 feet)X X X AB-4 Lower Ash (15 feet)X X X AB-4 Medium Ash (30 feet)X X X AB-5S X X X AB-5SL X X X Prepared by: CHB Checked by: CDE Well ID Pre-test Background AB-4 CLUSTER Ash Basin Pumping Test Work Plan July 10, 2018 Belews Creek Steam Station SynTerra \\synterracorp.com\Data\Proj\Duke Energy Carolinas\20. BELEWS CREEK\CAP UPDATE 2018\Aquifer Testing\Work Plan\Final Ash Basin Pumping Test Work Plan.docx APPENDIX A BORING LOGS FOR AB-4 AND AB-5 WELL CLUSTERS