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Home My WebLink AboutNC0003425_Appx G - Methodology_201710312017 Comprehensive Site Assessment Update October 2017 Roxboro Steam Electric Plant SynTerra APPENDIX G METHODOLOGY Duke Energy Low Flow Sampling Plan (June 10, 2015) Assessment Methodology 2017 Comprehensive Site Assessment Update October 2017 Roxboro Steam Electric Plant SynTerra Duke Energy Low Flow Sampling Plan (June 10, 2015) Low Flow Sampling Plan Duke Energy Facilities Ash Basin Groundwater Assessment Program North Carolina June 10, 2015 Duke Energy | Low Flow Groundwater Sampling Plan Table of Contents TABLE OF CONTENTS Low Flow Sampling Plan ....................................................................................................... 1 1.0 PURPOSE ............................................................................................................................... 1 2.0 GENERAL CONSIDERATIONS ............................................................................................. 1 3.0 PROCEDURES ....................................................................................................................... 2 3.1 Pre-Job Preparation ............................................................................................................. 2 3.2 Water-Level Measurements ................................................................................................. 3 3.3 Well Purging ........................................................................................................................ 4 3.3.1 Low-Flow Well Purging ............................................................................................ 4 3.3.2 Volume-Averaging Well Purging .............................................................................. 8 3.4 Sampling ....................................................................................................................... 10 3.4.1 Low-Flow Sampling ............................................................................................... 10 3.4.2 Sampling after Volume-Averaging Purge ............................................................... 11 3.5 Sample Handling, Packing, and Shipping ..................................................................... 11 3.5.1 Handling ................................................................................................................ 11 3.5.2 Sample Labels ....................................................................................................... 11 3.5.3 Chain-of-Custody Record ...................................................................................... 12 3.6 Field Quality Control Samples ....................................................................................... 12 3.7 Field Logbook Documentation....................................................................................... 13 3.8 Decontamination and Waste Management ................................................................... 14 4.0 REFERENCES ..................................................................................................................... 14 APPENDIX ADecontamination of Equipment SOP ................................................................... 15 1.0 Purpose & Application ...................................................................................................... 16 2.0 Equipment & Materials .......................................................................................................... 16 3.0 Procedure ............................................................................................................................. 16 3.1 Decontamination of Non-Disposable Sampling Equipment .......................................... 16 3.2 Decontamination of Field Instrumentation .................................................................... 16 3.3 Decontamination of Groundwater Sampling Equipment ............................................... 17 3.4 Materials from Decontamination Activities .................................................................... 17 APPENDIX BSampling Equipment Check List – Table 1.......................................................... 18 APPENDIX CField Logbook/Data Sheets ................................................................................. 20 Duke Energy | Low Flow Groundwater Sampling Plar 1.0 PURPOSE 1 1.0 PURPOSE The purpose of this low flow sampling plan is to establish a standard operating procedure (SOP) to describe collection procedures for groundwater samples from monitoring wells using low-flow purging and sampling techniques or by the volume- averaged purging and sampling method at Duke Energy Ash Basin Groundwater Assessment Program facilities. 2.0 GENERAL CONSIDERATIONS Potential hazards associated with the planned tasks shall be thoroughly evaluated prior to conducting field activities. The Ready-To-Work Plan developed for each facility provides, among other items, a description of potential hazards and associated safety and control measures. Sampling personnel must wear powder-free nitrile gloves or equivalent while performing the procedures described in this SOP. Specifically, gloves must be worn while preparing sample bottles, preparing and decontaminating sampling equipment, collecting samples, and packing samples. At a minimum, gloves must be changed prior to the collection of each sample, or as necessary to prevent the possibility of cross-contamination with the sample, the sample bottles, or the sampling equipment. Field sampling equipment shall be decontaminated in accordance with the Decontamination of Equipment SOP (Appendix A) prior to use. Although sampling should typically be conducted from least to most impacted location, field logistics may necessitate other sample collection priorities. When sampling does not proceed from least to most impacted location, precautions must be taken to ensure that appropriate levels of decontamination are achieved. An example of equipment needed to properly conduct low-flow purging and sampling or volume- averaged groundwater purging and sampling is listed on the example checklist in Table 1 (Appendix B). If a portable generator is used to power the purge pump, it shall be attempted to be located downwind of the well being sampling to avoid cross-contamination of the sample with exhaust from the generator motor. Duke Energy | Low Flow Groundwater Sampling Plan 3.0 PROCEDURES 2 3.0 PROCEDURES The following sections describe the general operating procedures and methods associated with groundwater sampling. Any variation in these procedures must be approved by the Project Manager (PM) and Quality Assurance/Quality Control (QA/QC) Lead and must be fully documented. Field work cannot progress until deviations are approved or resolved. 3.1 Pre-Job Preparation The information listed below may be reviewed prior to sampling activities, if available, and can be beneficial on-site for reference in the field as necessary: • A list of the monitoring wells to be sampled; • Information describing well location, using site-specific or topographic maps or Global Positioning System (GPS) coordinates and descriptions tied directly to prominent field markers; • A list of the analytical requirements for each sampling location; • Boring logs and well construction details, if available; • Survey data that identify the documented point of reference (V-notch or other mark on well casing) for the collection of depth-to-groundwater and total well depth measurements; • Previous depth-to-groundwater measurements; • Previous pump placement depths (dedicated pumps as well as portable pumps) for each sampling location, if available; • Previous pump settings and pumping and drawdown rates, if available; and • Previous analytical results for each monitoring well, if known. The information above is useful when determining the sampling order, pump intake depth, and purge and recharge rates, and can facilitate troubleshooting. The following activities should be completed prior to mobilizing to the site: • Obtain equipment necessary for completing the sampling activities (see the example checklist in Table 1). • Ensure appropriate laboratory-provided bottles are available for both the required analyses and for QC samples and that there has been thorough coordination with the analytical laboratory. Duke Energy | Low Flow Groundwater Sampling Plan 3.0 PROCEDURES 3 • Obtain site-specific maps or GPS coordinates showing clearly marked monitoring well locations or groundwater sample points. • Review the project work control documents such as the Ready-To-Work Plan, and appropriate SOPs in an effort to determine project-specific sampling requirements, procedures, and goals. • Verify that legal right-of-entry has been obtained and site access has been granted, where required. • Instruct the field team to avoid discussing project data with the public and to refer questions to the Project Manager. 3.2 Water-Level Measurements Prior to pump placement, an initial depth-to-water level and total well depth should be measured. For monitoring wells screened across the water table, this measurement shall be used to determine the required depth to the pump intake (typically, approximately the mid-point of the saturated screen length for low-flow purging and sampling). The procedure for measuring water levels may include the following: 1) Inspect the well head area for evidence of damage or disturbance. Record notable observations in the field logbook. 2) Carefully open the protective outer cover of the monitoring well noting the presence of bee hives and/or spiders, as these animals are frequently found inside well covers. Remove any debris that has accumulated around the riser near the well plug. If water is present above the top of the riser and well plug, remove the water prior to opening the well plug. Do not open the well until the water above the well head has been removed. 3) If practical, well plugs shall be left open for approximately five minutes to allow the static water level to equilibrate before measuring the water level (if well plugs are vented, then a waiting period is not applicable). 4) Using an electronic water-level indicator accurate to 0.01 feet, determine the distance between the established point of reference (usually a V-notch or indelible mark on the well riser) and the surface of the standing water present in the well. Record these data in the field logbook. Repeat this measurement until two successive readings agree to within 0.01 feet. 5) Using an electronic water-level indicator accurate to 0.01 feet, determine the distance between the established point of reference (usually a V-notch or indelible mark on the well riser) and the bottom of the well. Note that there should not be considerable slack in the water-level indicator cable. Record these data in the field logbook. Repeat this measurement until two successive readings agree to within 0.01 feet. 6) If the monitoring well has the potential to contain non-aqueous phase liquids (NAPLs), probe the well for these materials using an optical interface probe. These wells will be attempted to be identified by the Project Manager prior to Duke Energy | Low Flow Groundwater Sampling Plan 3.0 PROCEDURES 4 mobilizing to the well. If NAPL is present, consult the Project Manager for direction on collecting samples for analysis. In general, do not collect groundwater samples from monitoring wells containing NAPL. 7) Decontaminate the water-level indicator (and interface probe, if applicable) and return the indicator to its clean protective casing. 3.3 Well Purging Wells must be purged prior to sampling to ensure that representative groundwater is obtained from the water-bearing unit. If the well has been previously sampled in accordance with this sampling plan, then the depth to the pump intake and the pumping rates should be duplicated to the extent possible during subsequent sampling events. Section 3.3.1 provides a description of low-flow well purging, and Section 3.3.2 provides a description of volume-averaging well purging (in the case it’s needed). 3.3.1 Low-Flow Well Purging Adjustable-rate peristaltic, bladder and electric submersible pumps are preferred for use during low-flow purging and sampling activities. Since purging and sampling are joined together as one continuous operation, care will be given to pump selection as it applies to the specific well conditions and analytes to be tested. Note that a ball valve (or similar valve constructed of polyethylene) may need to be installed to reduce the flow rate to the required level. The low-flow purging and sampling guidance is provided below: 1) Using the specific details of well construction and current water-level measurement, determine the pump intake set depth (typically the approximate mid-point of the saturated well screen or other target sample collection depth adjacent to specific high-yield zones). 2) Attach tubing and supporting rope (if applicable) to the pump and very slowly lower the unit until the pump intake depth is reached. Measure the length of supporting rope required, taking into account the pump length, to attain the required depth. Record the depth to the pump intake in the field logbook. Notes: 1) Sampling shall use new certified-clean disposable tubing. 2) Rope shall be clean, unused, dedicated nylon rope. If a pump is to remain in a well as part of a separate monitoring program, then the rope shall be suspended within the well above the water column for future use. If the pump is removed after sample collection, the rope shall be disposed. 3) After allowing time for the water level to equilibrate, slowly lower the electronic water-level probe into the well until the probe contacts the groundwater. Record the water level in the field logbook. Duke Energy | Low Flow Groundwater Sampling Plan 3.0 PROCEDURES 5 4) If the well has been previously sampled using low-flow purging and sampling methods, begin purging at the rate known to induce minimal drawdown. Frequently check the drawdown rate to verify that minimum drawdown is being maintained. If results from the previous sampling event are not known, begin purging the well at the minimum pumping rate of approximately 100 milliliters per minute (mL/min) (EPA, July 1996). Slowly increase the pumping rate to a level that does not cause the well to drawdown more than about 0.3 feet, if possible. Never increase the pumping rate to a level in excess of 500 mL/min (approximately 0.13 gallon per minute [gpm]). Record the stabilized flow rate, drawdown, and time on the field data sheets. 5) If the drawdown does not stabilize at 100 mL/min (0.026 gpm), continue pumping. However, in general, do not draw down the water level more than approximately 25% of the distance between the static water level and pump intake depth (American Society for Testing and Materials [ASTM], 2011). If the recharge rate of the well is lower than the minimum pumping rate but the drawdown is less than 25% of the distance between the static water level and pump intake depth after three volumes of well water are removed, then collect samples at this point even though indicator field parameters have not stabilized (EPA, July 1996). Commence sampling as soon as the water level has recovered sufficiently to collect the required sample volumes. Otherwise, the Volume-Averaging Well Purging method should be considered.Allow the pump to remain undisturbed in the well during this recovery period to minimize the turbidity of the water samples. Fully document the pump settings, pumping rate, drawdown, and field parameter readings on the Well Sampling / MicroPurge (Low Flow) Log in the field logbook. Note: For wells that either have very slow recharge rates, that draw down excessively (more than 25% of the distance between the static water level and pump intake depth) at the minimum pumping rate (100 mL/min or 0.026 gpm), or require a higher pumping rate (greater than 500 mL/min or 0.13 gpm) to maintain purging, the procedures described above may not apply. For these “special case” wells, the Field Team Leader shall seek guidance from the Project Manager about the appropriate purging and sampling methodologies to be employed (such as volume-averaged purging and sampling described in Section 3.3.2). 6) Once an acceptable flow rate has been established, begin monitoring designated indicator field parameters. Indicator parameters are pH, specific conductance, dissolved oxygen (DO), and turbidity. Although not considered purge stabilization parameters, temperature and oxidation reduction potential (ORP) will be recorded during purging. Base the frequency of the measurements on the time required to completely evacuate one volume of the flow through the cell to ensure that independent measurements are made. For example, a 500-mL cell in a system pumped at a rate of 100 mL/min is evacuated in five minutes; accordingly, measurements are made and recorded on the field data form (Appendix C) approximately five minutes apart. Indicator parameters have stabilized when three consecutive readings, taken at three to five-minute intervals, meet the following criteria (EPA, March 2013): Duke Energy | Low Flow Groundwater Sampling Plan 3.0 PROCEDURES 6 • pH ± 0.1 standard unit • Specific Conductance ± 5% in µS/cm • DO ± 0.2 mg/L or 10% saturation • Turbidity less than 10 NTUs The target for monitoring turbidity is readings less than ten nephelometric turbidity units (NTUs). In some instances, turbidity levels may exceed the desired turbidity level due to natural aquifer conditions (EPA, April 1996). When these conditions are encountered, the following guidelines shall be considered. • If turbidity readings are slightly above 10 NTU, but trending downward, purging and monitoring shall continue. • If turbidity readings are greater than 10 NTU and have stabilized to within 10% during three successive readings, attempt to contact the Project Manager prior to collecting the groundwater sample. • If turbidity readings are greater than 10 NTU and are not stable, well sampling shall be based upon stabilization of more critical indicator parameters (such as dissolved oxygen) without attainment of the targeted turbidity. Attempt to contact the Project Manger if this condition is encountered prior to collecting the groundwater sample. • If after 5 well volumes or two hours of purging (whichever is achieved first), critical indicator field parameters have not stabilized, discontinue purging and collect samples. Fully document efforts used to stabilize the parameters (such as modified pumping rates). Note: While every effort should be taken to ensure that indicator parameters stabilize, some indicator parameters are more critical with respect to certain contaminant types. It is important to identify which indicator parameters are most important to the project prior to commencement of field activities so that unnecessarily protracted purge times can be avoided. For example, the critical indicator parameter associated with metals is turbidity. While it is desirable to sample wells when turbidity measurements are less than 5 NTU, Duke Energy recognizes that these values may not be attainable. Duke Energy, and its sub- consultants, have taken multiple steps (e.g., use of pre-packed screens, carefully selected sand pack, etc.) to alleviate the potential for elevated turbidity in newly installed wells. However, even with these conservative and targeted well installation specifications, other naturally occurring conditions (e.g., iron fluctuation) may prevent sampling of wells at turbidity values less than 5 NTU. Following sample collection and laboratory data evaluation, Duke Energy may review these data with respect to turbidity values to determine if additional well development is needed or if well construction has affected groundwater conditions. It may be necessary to redevelop wells from time to time to minimize Duke Energy | Low Flow Groundwater Sampling Plan 3.0 PROCEDURES 7 sample turbidity. Fine silt and clay can collect at the base of a well over time. The effect on future sampling events can be reduced by lowering the tubing or pump to the bottom of the well (after all the groundwater samples have been collected) and pumping until the purge water from the bottom of the well screen is clear. Note: If purging of a well does not result in turbidity measurements of 10 NTU or less, the field sampler shall alert the Project Manager. The sampling team will assess options to reduce the turbidity as soon as possible. There are a variety of water-quality meters available that measure the water quality parameters identified above. A multi-parameter meter capable of measuring each of the water quality parameters referenced previously (except for turbidity) in one flow-through cell is required. Turbidity shall be measured using a separate turbidity meter or prior to flow into the flow through cell using an inline T-valve, if using one multi-meter during purging. The water quality meter (and turbidity meter) shall be calibrated as per manufacturer’s instructions. Calibration procedures shall be documented in the project field logbook including calibration solutions used, expiration date(s), lot numbers, and calibration results. Duke Energy | Low Flow Groundwater Sampling Plan 3.0 PROCEDURES 8 3.3.2 Volume-Averaging Well Purging For wells that either have very slow recharge rates, that draw down excessively at the minimum pumping rate (100 mL/min or 0.026 gpm), or require a higher pumping rate (greater than 500 mL/min or 0.13 gpm) to maintain purging (i.e., low-flow well purging and sampling is not appropriate), the volume-averaging well purging and sampling method may be used. The Field Team Leader shall seek approval from the Project Manager before utilizing the volume-averaging method instead of the low-flow method. 3.3.2.1 CALCULATE PURGE VOLUMES Based on the depth-to-water (DTW) and total depth (TD) measurements, the volume of standing water in the well must be calculated using the following procedures. 1) Subtract DTW from TD to calculate the length of the standing water column (Lwc) in the well. ܶܦ െ ܦܹܶ ൌ ܮ௪௖ 2) Multiply the length of the standing water column by the volume calculation (gallon per linear foot of depth) based on the inner casing diameter (see example list below) to determine the total standing water volume; this represents one well volume. ܸ௪ = ܮ௪௖ ൈ2ߨݎଶ 1-inch well = 0.041 gallon per linear foot 2-inch well = 0.163 gallon per linear foot 4-inch well = 0.653 gallon per linear foot 6-inch well = 1.469 gallons per linear foot 8-inch well = 2.611 gallons per linear foot 3) Multiply the well volume calculated in the previous step by three and five to obtain the approximate respective total purge volume (the target purge volume is between three and five standing well volumes). For wells with multiple casing diameters (such as open bedrock holes), calculate the volume for each segment. Take the sum of the values and multiply by three and five to determine the minimum and maximum purge volumes, respectively. 4) Fully document the volume calculation in the field logbook or on the Groundwater Sampling Field Sheets. Duke Energy | Low Flow Groundwater Sampling Plan 3.0 PROCEDURES 9 3.3.2.2 PURGE THE MONITORING WELL Determine the appropriate pump to be used for purging—the preferred and most commonly used methods involve the use of a surface centrifugal or peristaltic pump whenever the head difference between the sampling location and the water level is less than the limit of suction and the volume to be removed is reasonably small. Where the water level is below the limit of suction or there is a large volume of water to be purged, use the variable speed electric submersible pump as the pump of choice (EPA, 2013). In some cases (shallow wells with small purge volumes), purging with a bladder pump may be appropriate. Once the proper pump has been selected: 1) Set the pump immediately above the top of the well screen or approximately three to five feet below the top of the water table (EPA, 2013). 2) Lower the pump if the water level drops during purging. Note: Use new certified-clean disposable tubing for purging and sampling. Note: Although volume-averaged sampling involves purging a specified volume of water (such as three to five well volumes) rather than basing purge completion on the stabilization of water quality indicator parameters, measuring and recording water-quality indicator parameters during purging provides information that can be used for assessment and remedial decision-making purposes. Indicator parameters are pH, specific conductance, DO, and turbidity as described in Section 3.3.1. Temperature and ORP will also be recorded during purging. 3) During well purging, monitor the discharge rate using a graduated cylinder or other measuring device, water-quality indicator parameters (if desired), and DTW as follows: • Initially, within approximately three minutes of startup, • Approximately after each well volume is purged, and then • Before purge completion. 4) Record pump discharge rates (mL/ min or gpm) and pump settings in the field logbook. Also, record any changes in the pump settings and the time at which the changes were made. 5) Maintain low pumping rates to avoid overpumping or pumping the well to dryness, if possible. If necessary, adjust pumping rates, pump set depth, or extend pumping times to remove the desired volume of water. 6) Upon reaching the desired purge water volume, turn off the purge pump. Do not allow the water contained in the pump tubing to drain back into the well when the pump is turned off. Use an inline check valve or similar device, or if using a peristaltic pump, remove the tubing from the well prior to turning off the pump. It is Duke Energy | Low Flow Groundwater Sampling Plan 3.0 PROCEDURES 10 preferred to collect samples within two hours of purging, but acceptable for collection up to 24 hours of purging. Do not collect samples after 24 hours of purging. Note: The removal of three to five well volumes may not be practical in wells with slow recovery rates. If a well is pumped to near dryness at a rate less than 1.9 L/min (0.5 gpm), the well shall be allowed to completely recover prior to sampling. If necessary, the two-hour limit may be exceeded to allow for sufficient recovery, but samples should be collected within 24 hours of purge completion. 3.4 Sampling 3.4.1 Low-Flow Sampling Following are the procedures for the collection of low-flow groundwater samples. These procedures apply to sample collection for unfiltered and filtered samples using a 0.45 micron filter. See Appendix A for use of 0.1 micron filtered samples. 1) Record the final pump settings in the field logbook prior to sample collection. 2) Measure and record the indicator parameter readings prior to sample collection on both the stabilization form and in the field logbook. 3) Record comments pertinent to the appearance (color, floc, turbid) and obvious odors (such as sulfur odor or petroleum hydrocarbons odor) associated with the water. 4) Arrange and label necessary sample bottles and ensure that preservatives are added, as required. Include a unique sample number, time and date of sampling, the initials of the sampler, and the requested analysis on the label. Additionally, provide information pertinent to the preservation materials or chemicals used in the sample. 5) Collect samples directly from pump tubing prior to the flow-through cell or via the in-line T-valve used for turbidity measurements (as described Section 3.3.1 (6) above). Ensure that the sampling tubing remains filled during sampling and attempt to prevent water from descending back into the well. Minimize turbulence when filling sample containers, by allowing the liquid to run gently down the inside of the bottle. Fill the labeled sample bottles in the following order: • Metals and Radionuclides, • Filtered Metals and Radionuclides, if required, and then • Other water-quality parameters. 6) Seal each sample and place the sample on ice in a cooler to maintain sample temperature preservation requirements. Duke Energy | Low Flow Groundwater Sampling Plan 3.0 PROCEDURES 11 7) Note the sample identification and sample collection time in field logbook and on Chain-of-Custody form. 8) Once sampling is complete, retrieve the sample pump and associated sampling equipment and decontaminate in accordance with procedures outlined in the Decontamination of Equipment SOP (Appendix A). 9) Close and secure the well. Clean up and remove debris left from the sampling event. Be sure that investigation-derived wastes are properly containerized and labeled, if applicable. 10) Review sampling records for completeness. Add additional notes as necessary. 3.4.2 Sampling after Volume-Averaging Purge The procedures described below are for the collection of groundwater samples after a volume-averaged purge has been conducted. Volume- averaging purge methods are described in Section 3.3.2. 1) If sampling with a pump, care shall be taken to minimize purge water descending back into the well through the pump tubing. Minimize turbulence when filling sample containers by allowing the liquid to run gently down the inside of the bottle. Fill the labeled sample bottles in the following order: • Metals and Radionuclides, • Filtered Metals and Radionuclides, if required, and then • Other water-quality parameters. 2) If sampling with a bailer, slowly lower a clean, disposable bailer through the fluid surface. Retrieve the bailer and fill the sample bottles as described above. Care shall be taken to minimize disturbing the sample during collection. 3.5 Sample Handling, Packing, and Shipping Samples shall be marked, labeled, packaged, and shipped in accordance with the sections outline below. 3.5.1 Handling The samples will be stored in coolers for transport to the site. Collected samples will be placed on ice in the sampling coolers for pickup or transport to the laboratory for analysis. 3.5.2 Sample Labels All sample containers will be new, laboratory cleaned and certified bottles. The bottles will be properly labeled for identification and will include the following information: • Project Site/ID Duke Energy | Low Flow Groundwater Sampling Plan 3.0 PROCEDURES 12 • Sample identifier (Well ID) • Name or initials of sampler(s) • Date and time of collection • Analysis parameter(s)/method • Preservative 3.5.3 Chain-of-Custody Record Sample transport and handling will be strictly controlled to prevent sample contamination. Chain-of-Custody control for all samples will consist of the following: • Sample containers will be securely placed in coolers (iced) and will remain under the supervision of project personnel until transfer of the samples to the laboratory for analysis has occurred. • Upon delivery to the laboratory, the laboratory director or his designee will sign the Chain-of-Custody control forms and formally receive the samples. The laboratory will ensure that proper refrigeration of the samples is maintained. The Chain-of-Custody document contains information which may include: • Client name • Client project name • Client contact • Client address • Client phone/fax number • Sampler(s) name and signature • Signature of person involved in the chain of possession • Inclusive dates of possession • Sample identification • Sample number • Date & time of collection • Matrix • Type of container and preservative • Number of containers • Sample type - grab or composite • Analysis parameter(s)/ method • Internal temperature of shipping container upon opening in the laboratory 3.6 Field Quality Control Samples Field quality control involves the routine collection and analysis of QC blanks to verify that the sample collection and handling processes have not impaired the quality of the samples. Duke Energy | Low Flow Groundwater Sampling Plan 3.0 PROCEDURES 13 • Equipment Blank – The equipment blank is a sample of deionized water, which is taken to the field and used as rinse water for sampling equipment. The equipment blank is prepared like the actual samples and returned to the laboratory for identical analysis. An equipment blank is used to determine if certain field sampling or cleaning procedures result in cross-contamination of site samples or if atmospheric contamination has occurred. One equipment blank sample will be prepared per day or per 20 groundwater samples, whichever is more frequent. Field and laboratory QA/QC also involves the routine collection and analysis of duplicate field samples. These samples are collected at a minimum rate of approximately one per 20 groundwater samples per sample event. A field duplicate is a replicate sample prepared at the sampling locations from equal portions of all sample aliquots combined to make the sample. Both the field duplicate and the sample are collected at the same time, in the same container type, preserved in the same way, and analyzed by the same laboratory as a measure of sampling and analytical precision. 3.7 Field Logbook Documentation Field logbooks shall be maintained by the Field Team Leader to record daily activities. The field logbook may include the following information for each well: • Well identification number • Well depth • Static water level depth • Presence of immiscible layers (yes – no) • Estimated well yield, if known • Purge volume and purge pumping rate • Time well purge began and ended • Well evacuation procedure and equipment • Field analysis data • Climatic conditions including air temperature • Field observations on sampling event • Well location • Name of collector(s) • Date and time of sample collection • Sampling procedure • Sampling equipment • Types of sample containers used and sample identification numbers • Preservative used Duke Energy | Low Flow Groundwater Sampling Plan 4.0 REFERENCES 14 The Field Team Leader shall review the field logbook entries for completeness and accuracy. The Field Team Leader is responsible for completion of the required data collection forms. Example field logs are in Appendix C. 3.8 Decontamination and Waste Management Sampling equipment decontamination shall be performed in a manner consistent with the Decontamination of Equipment SOP (Appendix A). Decontamination procedures shall be documented in the field logbook. Investigation-derived wastes produced during sampling or decontamination shall be managed in accordance with State and Station-specific rules for disposal of wastes. 4.0 REFERENCES American Society for Testing and Materials (ASTM). Standard Practice for Low-Flow Purging and Sampling for Wells and Devices Used for Ground-Water Quality Investigations, D 6771-02. 2011. Test Methods for Evaluating Solid Waste - Physical/Chemical Methods (SW-846), Third Edition. U.S. Environmental Protection Agency. Update I, II, IIA, IIB, III, IIIA, IVA and IVB. United States Environmental Protection Agency (EPA), Office of Research and Development, Office of Solid Waste and Emergency Response. Ground Water Issue, “Low-Flow (Minimal Drawdown Sampling Procedures). Document Number EPA/540/S- 95/504,” April 1996. U.S. EPA. Region 4, Groundwater Sampling Operating Procedure. Document Number SESDPROC-301-R3, November 2013. U.S. EPA. Region I, Low Stress (Low Flow) Purging and Sampling Procedure for the Collection of Ground Water Samples from Monitoring Wells, Revision 2, July 1996. Duke Energy | Low Flow Groundwater Sampling Plar Decontamination of Equipment SOP 15 A Decontamination of Equipment SOP Duke Energy | Low Flow Groundwater Sampling Plar Purpose & Application 16 1.0 Purpose & Application This procedure describes techniques meant to produce acceptable decontamination of equipment used in field investigation and sampling activities. Variations from this SOP should be approved by the Project Manager prior to implementation and a description of the variance documented in the field logbook. 2.0 Equipment & Materials • Decontamination water, • Alconox detergent or equivalent non-phosphate detergent • Test tube brush or equivalent • 5-gallon bucket(s) • Aluminum foil • Pump 3.0 Procedure 3.1 Decontamination of Non-Disposable Sampling Equipment Decontamination of non-disposable sampling equipment used to collect samples for chemical analyses will be conducted prior to each sampling as described below. Larger items may be decontaminated at the decontamination pad. Smaller items may be decontaminated over 5-gallon buckets. Wastewater will be disposed in accordance with applicable State and Station-specific requirements. 1. Alconox detergent or equivalent and water will be used to scrub the equipment. 2. Equipment will be first rinsed with water and then rinsed with distilled/deionized water. 3. Equipment will be air dried on plastic sheeting. 4. After drying, exposed ends of equipment will be wrapped or covered with aluminum foil for transport and handling. 3.2 Decontamination of Field Instrumentation Field instrumentation (such as interface probes, water quality meters, etc.) will be decontaminated between sample locations by rinsing with deionized or distilled water. If visible contamination still exists on the equipment after the rinse, an Alconox (or equivalent) detergent scrub will be added and the probe thoroughly rinsed again. Decontamination of probes and meters will take place in a 5-gallon bucket. The decontamination water will be handled and disposed in accordance with applicable State and Station-specific requirements. Duke Energy | Low Flow Groundwater Sampling Plar 3.0 Procedure 17 3.3 Decontamination of Groundwater Sampling Equipment Non-disposable groundwater sampling equipment, including the pump, support cable and electrical wires in contact with the sample will be thoroughly decontaminated as described below: 1. As a pre-rinse, the pump will be operated in a deep basin containing 8 to 10 gallons of water. Other equipment will be flushed with water. 2. The pump will be washed by operating it in a deep basin containing phosphate- free detergent solution, such as Alconox, and other equipment will be flushed with a fresh detergent solution. Detergent will be used sparingly, as needed. 3. Afterwards, the pump will be rinsed by operating it in a deep basin of water and other equipment will be flushed with water. 4. The pump will then be disassembled and washed in a deep basin containing non-phosphate detergent solution. All pump parts will be scrubbed with a test tube brush or equivalent. 5. Pump parts will be first rinsed with water and then rinsed with distilled/deionized water. 6. For a bladder pump, the disposable bladder will be replaced with a new one for each well and the pump reassembled. 7. The decontamination water will be disposed of properly. 3.4 Materials from Decontamination Activities All wastewater and PPE generated from decontamination activities will be handled and disposed in accordance with applicable State and Station-specific requirements. Duke Energy | Low Flow Groundwater Sampling Plar Sampling Equipment Check List – Table 1 18 B Sampling Equipment Check List – Table 1 Duke Energy | Low Flow Groundwater Sampling Plar Sampling Equipment Check List – Table 1 19 Table 1: Suggested Groundwater Sampling Equipment & Material Checklist Item Description Check Health & Safety Nitrile gloves Hard hat Steel-toed boots Hearing protection Field first-aid kit Fire Extinguisher Eyewash Safety glasses Respirator and cartridges (if necessary) Saranex™/Tyvek® suits and booties (if necessary) Paperwork Health and Safety Plan Project work control documents Well construction data, location map, field data from previous sampling events Chain-of-custody forms and custody seals Field logbook Measuring Equipment Flow measurement supplies (for example, graduated cylinder and stop watch) Electronic water-level indicator capable of detecting non-aqueous phase liquid Sampling Equipment GPS device Monitoring well keys Tools for well access (for example, socket set, wrench, screw driver, T-wrench) Laboratory-supplied certified-clean bottles, preserved by laboratory (if necessary) Appropriate trip blanks and high-quality blank water Sample filtration device and filters Submersible pump, peristaltic pump, or other appropriate pump Appropriate sample and air line tubing (Silastic®, Teflon®, Tygon®, or equivalent) Stainless steel clamps to attach sample lines to pump Pump controller and power supply Oil-less air compressor, air line leads, and end fittings (if using bladder pump) In-line groundwater parameter monitoring device (for example, YSI-556 Multi- Parameter or Horiba U-52 water quality meter) Turbidity meter Bailer Calibration standards for monitoring devices Duke Energy | Low Flow Groundwater Sampling Plar Field Logbook/Data Sheets 20 C Field Logbook/Data Sheets Duke Energy | Low Flow Groundwater Sampling Plar Field Logbook/Data Sheets 21 Groundwater Potentiometric Level Measurement Log Well Number Time Depth to Water (ft)* Depth to Bottom (ft)* Water Column Thickness (ft) Reference Point Elevation (ft, MSL) Potentiometric Elevation (ft, MSL) Remarks Field Personnel: Checked By: * - Measurements are referenced from the top of the PVC inner casing (TOC) for each respective monitoring well. TOCs shall be surveyed by a Professional Land Surveyor and referenced to NAVD88. Duke Energy | Low Flow Groundwater Sampling Plar Field Logbook/Data Sheets 22 Well Sampling / MicroPurge Log Project Name: Sheet: of Well Number: Date: Well Diameter: Top of Casing Elevation (ft, MSL): Pump Intake Depth (ft): Total Well Depth (ft): Recharge Rate (sec): Initial Depth to Water (ft): Discharge Rate (sec): Water Column Thickness (ft): Controller Settings: Water Column Elevation (ft, MSL): Purging Time Initiated: 1 Well Volume (gal): Purging Time Completed: 3 Well Volumes (gal): Total Gallons Purged: WELL PURGING RECORD Time Volume Purged (gallons) Flow Rate (mL/min) Depth to Water (ft) Temperature (°C) pH (s.u.) Specific Conductance (mS/cm) Dissolved Oxygen (mg/L) ORP (mV) Turbidity (NTU) Comments Stabilization Criteria Min. 1 Well Volume + 3°C + 0.1 + 3% + 10% + 10 mV < 5 NTU or + 10 % if > 5 NTU GROUNDWATER SAMPLING RECORD Sample Number Collection Time Parameter Container Preservative Duke Energy | Low Flow Groundwater Sampling Plar Field Logbook/Data Sheets 23 DAILY FIELD REPORT Project Name: Field Manager: Field Personnel: Date: Weather: Labor Hours Equipment Materials Field Observations: Submitted by: Reviewedby: 2017 Comprehensive Site Assessment Update October 2017 Roxboro Steam Electric Plant SynTerra Assessment Methodology Appendix G - Methodology Duke Energy Progress – Roxboro Steam Electric Plant Comprehensive Site Assessment Update 1 of 16 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\CSA Update Oct 2017\Draft Final 10_20_2017\Appendices\Appendix G\Methodology.docx The approach to conducting the Comprehensive Site Assessment (CSA) in 2015 at the Roxboro Plant was described in the Groundwater Assessment Work Plan (Revision 1, December 2014). The objective was to collect and analyze samples of soil, ash, groundwater, surface water, and sediment to more accurately determine the vertical and horizontal concentrations of Constituents of Interest (COIs). This section describes equipment and methods employed to collect and preserve appropriate samples and obtain representative analytical results. Assessment procedures were conducted in general accordance with this plan and other, task- specific NCDEQ-approved work plans/procedures. 1.0 Subsurface Investigation Characterization of subsurface material was conducted by collecting ash, soil, sediment, ash pore water, groundwater, seep water, and surface water samples for analysis. Ash, soil, ash pore water, and groundwater samples were obtained through completion of drilled borings and monitoring wells. The approach for subsurface sample acquisition and analysis follows. 1.1 Drilling Methods Five drilling methods were employed to collect subsurface samples. The selection of drilling technology was dependent on soil conditions, sample depth, and accessibility. Drilling tools (sonic core barrels and casings, downhole pneumatic air hammer, GeoprobeTM samplers and drill rods, hand auger buckets and hollow stem augers) were thoroughly decontaminated prior to starting a boring. Daily equipment rinse samples were collected to confirm the effectiveness of decontamination. Water used for drilling operations was obtained from the City of Roxboro Municipal water supply. A sample of this source water was analyzed for the full set of parameters). 1.1.1 Sonic Coring The primary method used for drilling soil borings and monitoring wells was rotary sonic drilling. The advantages provided by this method include less disturbance of the borehole wall and minimized groundwater sample turbidity. 1.1.2 Direct Push Technology A GeoprobeTM direct push sampling rig was used to acquire sample cores in the ash basin. The primary advantage of this drilling method was the small size and weight of the rig. Appendix G - Methodology Duke Energy Progress – Roxboro Steam Electric Plant Comprehensive Site Assessment Update 2 of 16 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\CSA Update Oct 2017\Draft Final 10_20_2017\Appendices\Appendix G\Methodology.docx 1.1.3 Hand Auger A hand auger was used at locations where sample depth was shallow or site conditions precluded the use of mechanized drilling equipment. 1.1.4 Air Rotary A GeoprobeTM drill rig was used in combination with compressed air to pneumatically hammer a boring. The primary advantage of this drilling method was the speed of drilling. 1.1.5 Hollow Stem Auger A GeoprobeTM drill rig equipped with hollow stem augers was used to install a boring. The primary advantage of this drilling method is for drilling and casing the hole simultaneously, thereby eliminating hole caving problems and contamination of soil samples in shallow unconsolidated subsurface materials. 1.2 Monitoring Well Installation Each monitoring well was constructed by North Carolina-licensed well drillers using sonic, direct push, or air rotary drilling techniques and in accordance with 15A NCAC 02C (Well Construction Standards). Drilling equipment was decontaminated prior to use at each location. Monitoring wells were constructed of 2-inch ID, National Sanitation Foundation (NSF) grade polyvinyl chloride (PVC) (ASTM D-1785-12) schedule 40 flush-joint threaded casing and 0.010-inch machine-slotted pre-packed screens. Well construction also included the use of pre-packed screens with additional sand in the annular space, to minimize sample turbidity. Packed well screens for each well were filled with clean, well-rounded, washed high grade No. 1A silica sand. No.1A sand is a 12/40 mesh filter sand comparable to the 20/40 mesh sand referenced in the Work Plan and is commonly used in monitoring well construction. Monitoring wells installed in ash pore water utilized additional precautions against fly ash fines incursion by using an extra fine “Geothermal” silica sand in the annular space and No. 1A silica sand in the pre-packed well screens. The filter pack was placed approximately two feet above the top of the pre-packed screen and then a minimum two-foot pelletized bentonite seal was placed above the filter pack. The remainder of the annular space was filled with a neat cement grout from the top of the upper bentonite seal to near ground surface. For some wells completed in the bedrock aquifer, double-cased wells were constructed as a precautionary measure to prevent COI migration from overlying material along Appendix G - Methodology Duke Energy Progress – Roxboro Steam Electric Plant Comprehensive Site Assessment Update 3 of 16 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\CSA Update Oct 2017\Draft Final 10_20_2017\Appendices\Appendix G\Methodology.docx annular space of the borehole. Surface casings were employed where saturated conditions existed in the saprolite or transition zone, and the necessity was determined based on observations of continuous cores recovered during drilling. Protective outer casing was installed using sonic drilling equipment with a 10-inch core barrel into the top of the bedrock which was determined based on observation of continuous cores recovered during drilling or air hammer drilling equipment. A permanent 6-inch diameter schedule 40 PVC protective outer casing was then installed and grouted in place. After the grout had sufficient time to set (minimum 24 hours), drilling was advanced through the outer casing using a 5-inch diameter core barrel or four-inch air hammer, and through the bedrock to the depth of water-bearing fractures (determined based on observation of continuous cores). If water-bearing fractures were not encountered in the shallow bedrock (2015 site assessment), drilling continued to a maximum approximate depth of 50 feet below the top of bedrock. To address data gaps, drilling continued to well yielding water bearing were encountered. Well were then installed in a similar approach as shallow monitoring wells as described above. Monitoring wells were completed with either aluminum/steel above ground protective casings or flush-mounted vaults with locking caps, locking expansion caps, and well tags. Protective covers were secured and completed in a concrete collar and a minimum two-foot square concrete pad. Vaults were installed in high traffic areas or other areas designated by Roxboro Plant personnel. 1.2.1 Monitoring Well Development Following installation, monitoring wells were developed to remove drill fluids, clay, silt, sand, and other fines which may have been introduced into the formation or sand pack during drilling and well installation, in addition to establishing connectivity of the well with the aquifer. Well development was performed using a portable submersible pump that was repeatedly moved up and down the well screen interval until the water was relatively clear. Some wells were initially developed with a bailer to remove the most turbid water and were later completed by developing with a submersible pump or a peristaltic pump. Development continued by sustained pumping until monitoring parameters (e.g., conductivity, pH, DO, and temperature) were generally stabilized, estimated quantities of drilling fluids, if used, were removed, and turbidity decreased to acceptable levels (approximately 10 NTUs). Wells were developed no sooner than 24 hours after well installation to allow for an adequate grout cure time. Appendix G - Methodology Duke Energy Progress – Roxboro Steam Electric Plant Comprehensive Site Assessment Update 4 of 16 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\CSA Update Oct 2017\Draft Final 10_20_2017\Appendices\Appendix G\Methodology.docx 1.3 Sample Collection and Analytical Methods Methods used for the collection and preservation of samples for various analyses are described in this section. Samples were collected in accordance with the quality assurance and quality control procedures outlined in the Work Plan. 1.3.1 Soils and Ash Sampling and Analysis Borings were logged and ash/soil samples were photographed, described, and visually classified in the field for origin, consistency/relative density, color, and soil type in accordance with the Unified Soil Classification System (ASTM D2487/D2488). Rinse blanks from soil sample collection equipment were collected for each soil boring/well installation location. At times, drilling for one location took more than one day and the rinse blank was collected on the first day. Rinse blanks for soil samples were collected by pouring deionized water through the sonic drill bit or through the hand auger bit. These pieces of equipment are normally the first introduced into the subsurface for a soil boring. Laboratory results for the rinse blanks are provided in Appendix I. Soil and ash samples were collected wearing nitrile gloves and prepared and analyzed using the following methods: 1.3.1.1 Metals Soil and ash samples were placed in amber glass bottles and stored on ice for shipment for total metals analysis. Concentrations of metals present in soils and ash were determined using analytical parameters presented in this report. 1.3.1.2 Organic Constituents Soil and ash samples were placed in amber glass bottles and stored on ice for shipment for total organic carbon (TOC) analysis. TOC content of soils and ash were determined in accordance with EPA Method 9060. 1.3.1.3 Leaching Characteristics Select soil and ash samples were placed in amber glass bottles and stored on ice for shipment for the mobility of inorganic analytes present using the Synthetic Precipitation Leaching Procedure (SPLP) following U.S. EPA Method 1312. 1.3.1.4 Bulk Chemistry Appendix G - Methodology Duke Energy Progress – Roxboro Steam Electric Plant Comprehensive Site Assessment Update 5 of 16 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\CSA Update Oct 2017\Draft Final 10_20_2017\Appendices\Appendix G\Methodology.docx Select soil and ash samples were stored and shipped in sealable plastic bags for bulk chemistry analysis. Identification and relative concentration of bulk chemistry was determined by American Assay Laboratories. Samples were dried at 80 oC overnight and pulverized to - 150 mesh and analyzed as follows: XRF-PP – a known sample amount was combined with binder, ground finer, and pressed into a disk. The disk was then analyzed by X-ray fluorescence (XRF). ICP-D4A – A sample pulp was digested with a combination of HF, HClO4, HCl, and HNO3 for a near-total digestion. The solution was then analyzed by Inductively Coupled Plasma (ICP)-Atomic Emission Spectroscopy (AES) and ICP-Mass Spectroscopy (MS). ICP-NF – A sample pulp was fused with Na2O2 and digested with HCl. The solution was then analyzed by ICP-AES and ICP-MS. Eltra Carbon & Sulfur – A sample pulp was combined with tungsten and iron accelerator and combusted in Eltra furnace for analysis of carbon and sulfur. Loss of Ignition (LOI) – A sample pulp was gradually heated in a gravimetric furnace to 1000° C while sample loss was calculated. 1.3.1.5 Mineralogy Select samples were stored and shipped in sealable plastic bags for mineralogical analysis. Identification and relative concentration of mineral types were determined by X-ray diffraction (XRD). The original sample was dried at 80° C (no pulp) and combined with water and disaggregated in an ultrasonic bath. The sample was then wet sieved at 63 micrometers to separate and quantify the sand fraction. The slurry was centrifuged at a calculated rotation per minute and time to separate the clay particles from the silt. The clay solution was then decanted off. Sand and silt fractions were dried, quantified, and analyzed using XRD as random mounts (XRD is a process by which X-rays are scattered by atoms that comprise the crystal structure of a given mineral, creating a pattern). Clay particles are deposited on slides forming an oriented mount for XRD. After the analysis, the clay particles were placed in an ethylene glycol environment overnight to test for expanding clays. When Appendix G - Methodology Duke Energy Progress – Roxboro Steam Electric Plant Comprehensive Site Assessment Update 6 of 16 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\CSA Update Oct 2017\Draft Final 10_20_2017\Appendices\Appendix G\Methodology.docx necessary, the clay particles are then heated to 400° C and re-analyzed for collapsing layers. 1.3.1.6 Development of Kd Terms To determine the sorption capacity of site soils, select samples were collected along proposed flow path transects. Samples were collected, handled, and preserved in order to eliminate impacts of ambient air on the oxidation-reduction potential (ORP) and hydrous ferrous oxide (HFO) on sampled materials. Samples were collected in plastics bags and sealed with a conventional vacuum sealer. The samples were stored on ice for shipment and kept out of direct sunlight. Samples were prepared and analyzed by the Civil and Environmental Engineering Department of the University of North Carolina at Charlotte (UNCC). Prior to sorption determinations, soil samples were dried at room temperature and periodically mixed throughout the drying process to prevent grain aggregation. Once dry, samples were sieved using a No. 10 U.S. standard sieve (10 mm) with 0.0787 inch openings. To quantify soil partition coefficients (Kd), column and batch tests were performed. Effluent samples collected from these tests were analyzed by inductively coupled plasma-mass spectroscopy and ion chromatography. To provide a basis for estimating COI source terms, leaching tests were performed on ash samples. Details of the analytical procedures/methods are briefly discussed below with more detail included in the analytical reports. 1.3.1.6.1 Column Tests Column tests were conducted by compacting soil and ash samples into 8 inch long (20.3 cm) polyethylene tubes (with dimensions 0.675 in. (16 mm) I.D. by 0.75 in. (19 mm) O.D) and plugged with two polypropylene end caps. Using groundwater and ash pore water analytical results from the site, feed solutions amended with all COIs found above the NCAC 15A 02L .0106(g) standards were produced and pumped into the columns. Analyses and equipment used are provided in the table below: Analyte Method Trace metals (Sb, As, B, Cd, Cr, Fe, Mn, Pb, Tl) EPA 200.8 Sulfate EPA 300.0 pH Standard Method 4500 B Appendix G - Methodology Duke Energy Progress – Roxboro Steam Electric Plant Comprehensive Site Assessment Update 7 of 16 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\CSA Update Oct 2017\Draft Final 10_20_2017\Appendices\Appendix G\Methodology.docx Conductivity Standard Method 2510 Oxidation-reduction potential (ORP) ASTM method G200-19 1.3.1.6.2 Batch Tests Batch tests were conducted in accordance with U.S. Environmental Protection Agency Technical Resource Document EPA/530/SW-87/006-F. COI-amended feed solution (described above in 1.3.1.6.1) and soil samples were mixed across a range of soil-to-solution ratios, followed by shaking until chemical equilibrium was achieved. Once equilibrium was achieved, solutions were drawn and analyzed as described in the above table. 1.3.1.6.3 Hydrous Ferrous Oxides Analysis The method for HFO determination in soil and ash samples was adapted from Chao and Zhou (1983). Following this method, soil samples were extracted using a 0.25M NH2OH·HCl-0.25M HCl combined solution. 1.3.1.6.4 Ash Leaching Tests Ash leach tests were performed to provide a basis for estimating COI source terms to develop the Kd terms. Ash samples were prepared and analyzed using EPA Method 1313 [2] (Liquid-Solid Partitioning as a Function of Extract pH Using a Parallel Batch Extraction Procedure) and EPA Method and EPA Method 1316 [3] (Liquid-Solid Partitioning as a Function of Liquid-Solid Ratio using a Parallel Batch Extraction Procedure). Method 1313 provides COI concentration as a function of pH (the test was conducted only at natural pH). Method 1316 provides COI concentration as a function of liquid to solid ratio. 1.3.1.7 Index Property Sampling and Analysis Select soil and ash samples were collected for laboratory analysis of physical properties to provide data for use in groundwater modeling. Samples were collected at selected locations for the following analyses using the described methods: Natural Moisture Content Determination, in accordance with ASTM D-2216 Appendix G - Methodology Duke Energy Progress – Roxboro Steam Electric Plant Comprehensive Site Assessment Update 8 of 16 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\CSA Update Oct 2017\Draft Final 10_20_2017\Appendices\Appendix G\Methodology.docx Grain size with hydrometer determination, in accordance with ASTM Standard D-422 In addition, undisturbed samples were collected using thin-walled tubes (“Shelby” tubes) advanced in ash and soil at select locations. Undisturbed samples were tested for the following: Natural Moisture Content Determination (ASTM D-2216) Grain size with hydrometer determination (ASTM Standard D-422) Hydraulic Conductivity Determination (ASTM Standard D-5084) Specific Gravity of Soils (ASTM Standard D-854) Sample porosity was calculated from parameters measured by these tests. 1.3.2 Ash Pore Water and Groundwater Sampling and Analysis New and existing wells were sampled using low-flow sampling techniques in accordance with the USEPA Region 1 Purging and Sampling Procedure for the Collection of Groundwater Samples from Monitoring Wells (revised January 19, 2010), the Groundwater Monitoring Program Sampling, Analysis and Reporting Plan, Roxboro Steam Electric Plant (SynTerra, October 2014), updated by the Low Flow Sampling Plan, Duke Energy Facilities, Ash Basin Groundwater Assessment Program, North Carolina, June 10, 2015. NCDEQ conditionally approved the Low Flow Sampling Plan in a June 11, 2015 email with an attachment summarizing their approval conditions. Groundwater was collected with a peristaltic pump, monsoon pump, or permanently installed bladder pump. Equipment blanks for groundwater sampling were collected daily. The sample was collected from a laboratory-supplied container of deionized water into laboratory-supplied bottleware. The equipment consisted of a peristaltic pump and tubing was pulled from the supplies planned for the day. Ash pore water and groundwater samples were analyzed in the field and laboratory. Only select samples were analyzed for radionuclides and metals speciation. For speciation analysis, select ash pore water or groundwater samples were collected with peristaltic or Engineered Plastic Mega Monsoon pump as described above but with acid-washed tubing and following a condensed version of EPA Method 1669. Appendix G - Methodology Duke Energy Progress – Roxboro Steam Electric Plant Comprehensive Site Assessment Update 9 of 16 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\CSA Update Oct 2017\Draft Final 10_20_2017\Appendices\Appendix G\Methodology.docx 2.0 Hydrogeologic Testing Hydrogeologic tests were performed and measurements were made to characterize site-specific hydrogeologic conditions. These activities included measuring water levels and conducting slug tests and packer tests. 2.1 Water Level Measurements During groundwater sampling activities, water level measurements were recorded at existing site monitoring wells, observation wells, piezometers, and newly installed wells. The measurements were made using electrical tapes that indicate the contact with water. A tape was lowered into a well and a graduated scale on the tape was used to measure the depth of the water level below the top of the casing. The uncertainty in this measurement is approximately +/- 0.01 ft, which is the resolution of the scale on the tape. The elevation of a reference point on the top of each casing was determined by a licensed surveyor, and we estimate the accuracy of these elevations to be +/- 0.01 ft Elevations were measured relative to a common datum, which was then referenced to mean sea level. Depth to water and the elevation of the top of casing were used to calculate the elevation of the water level in the well. This elevation was assumed to be the hydraulic head at the mid-point of the screen on the well. The hydraulic heads measured in shallow wells were contoured using standard linear interpolation methods to generate water level maps for shallow, water table conditions. These maps were used to infer approximate directions of horizontal groundwater flow within the constraints that the hydraulic conductivity was isotropic in the horizontal direction. Measurements from clusters of piezometers were used to estimate vertical hydraulic head gradients. Water levels in wells in the ash basins were used to estimate the elevation of saturated conditions, and multiple measurements provided approximate estimates of the directions of ground water flow. Water level measurements used for preparation of hydraulic head maps were collected during a single 24-hour period and prior to purging for sampling. 2.2 Slug Tests 2.2.1 Field Methods After the development and sampling of monitoring wells, hydraulic conductivity tests (rising head and/or falling head slug tests) were conducted on each of the new wells. Slug tests were performed in general accordance with ASTM D4044- 96 Standard Test Method (Field Procedure) for Instantaneous Change in Head (Slug) Tests for Determining Hydraulic Properties of Aquifers and NCDENR Performance and Analysis of Aquifer Slug Test and Pumping Test Policy, dated May 31, 2007. Appendix G - Methodology Duke Energy Progress – Roxboro Steam Electric Plant Comprehensive Site Assessment Update 10 of 16 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\CSA Update Oct 2017\Draft Final 10_20_2017\Appendices\Appendix G\Methodology.docx A slug test involves the injection or withdrawal of a known volume (slug) while measuring the resulting fluctuation of the groundwater level. Site slug tests employed both the solid cylinder (PVC slug) and the water withdrawal (bailer) methods. When a PVC slug was utilized, both a falling-head (slug-in) and a rising-head (slug-out) test was performed. However, when a bailer was used, only a rising-head slug test was performed. Prior to the performance of each slug test, static water level was measured and recorded. A Solinst Model 3001® Edge electronic pressure transducer or equivalent was placed in a well at least one foot beneath the lowest level that would be reached by the submerged slug. This ensured that the cross-sectional area of the well bore remained uniform during the slug test, which facilitates analysis of the results. The Levelogger® was connected to a field laptop and programmed with the well identification, date, and time. The pressure transducer was then allowed to equilibrate to the conditions in the well for at least 10 minutes. Falling-Head Slug Test Falling-head slug tests were conducted by rapidly lowering a slug into the well and positioning the top of the slug approximately one foot below the initial static water level. This caused the water level to rise, and then the water level fell and the resulting pressure change was measured and recorded electronically using the pressure transducer. The water level in the well was allowed to recover to between 60 and 80 percent of the initial water level. After falling-head slug tests were completed, sufficient time was allowed for the water level to reach equilibrium before conducting the rising-head slug test. Rising-Head Slug Test A rising-head slug test, also known as a slug-out test, was conducted by rapidly withdrawing a submerged slug, dropping the water level in the well. Most rising-head slug tests were performed until the water level in the well recovered to 60 to 80 percent of the pre-test water level. Slug tests in wells completed in low permeability formations were terminated after 70% recovery or one hour, whichever occurred first. When using a bailer to withdrawal a slug of water, the rising-head procedure was followed, first allowing time for the well to equilibrate with the bailer in the water before removing the slug of water. Hydraulic well tests were conducted with packers in some bedrock borings. Packer tests utilized a double packer system arranged to straddle an interval of the borehole between 5 feet and 10 feet long. The straddle packer system was used to isolate and characterize Appendix G - Methodology Duke Energy Progress – Roxboro Steam Electric Plant Comprehensive Site Assessment Update 11 of 16 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\CSA Update Oct 2017\Draft Final 10_20_2017\Appendices\Appendix G\Methodology.docx depth intervals identified from observations of the rock core. Typically, depth intervals of the core containing fractures that were thought to be open in the subsurface were selected for packer testing. This might bias the hydraulic conductivity determined from packer tests, but it is justified because the objective of the testing was to characterize the depth intervals that controlled groundwater flow. The U.S. Bureau of Reclamation test method and calculation procedures as described in Chapter 17 of their Engineering Geology Field Manual (2nd Edition, 2001) were utilized. Slug tests were conducted with packers using a solid cylinder as described in Section 2.2. Packers were also used during a purge-recovery investigation. The purge-recovery investigation involved purging the well and monitoring the recovery of water level in the packed-off zone. Purge-recovery results were used as an indicator of the location of water bearing zones to and determine well screen placement. 2.2.2 Parameters Slug test data were analyzed using AQTESOLVTM for Windows, version 4.5 (AQTESOLVTM). This involved using pressure data from transducers, aquifer data thickness data from cross-sections, and boring logs and well completion data (such as screen length, inside radius of well casing, and radius of well obtained) from CSA boring logs. 2.2.3 Analytical Methods In selecting a method for analyzing the slug tests, the formations intersected by the wells were assumed to isotropic and uniform over the scale influenced by the well. Furthermore, it was assumed that Darcy’s Law was valid in all the formations, and that the wells sampled a scale that was large enough so that flow through fractures could be characterized using an equivalent hydraulic conductivity. This is an accepted approach for characterizing flow through porous and fractured media. Anisotropy was assumed when analyzing the slug tests because slug tests are only weakly sensitive to anisotropy and the resulting large uncertainty in parameters would not warrant pursuing the interpretation of anisotropy using slug tests. Wells were recently developed prior to slug testing, and it was assumed that development was sufficient to remove well skin. As a result, effects of well skin were ignored in the analyses. Slug tests are weakly sensitive to storage properties in aquifers. Methods of analysis are available to estimate storativity from slug tests, but the uncertainty is typically large because of the weak sensitivity. Pressure transients were of minor Appendix G - Methodology Duke Energy Progress – Roxboro Steam Electric Plant Comprehensive Site Assessment Update 12 of 16 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\CSA Update Oct 2017\Draft Final 10_20_2017\Appendices\Appendix G\Methodology.docx importance compared to steady state conditions during this investigation. Storativity is unnecessary for steady state analyses, so methods of analyzing slug tests that provided estimates of storativity were ignored. Slug tests were analyzed using the Hvorslev method. This method is consistent with the assumptions outlined above, and it is the most widely used method of analyzing slug tests among practicing hydrogeologists. AQTESOLVTM was used to input parameters listed above and plotted normalized head vs. time. Hvorslev method was chosen in AQTESOLVTM and visual line matching used for the Hvorslev equation was used to calculate the transmissivity. The Hvorslev method involves plotting the log of the normalized head as a function of time and fitting the data with a straight line (Butler, 1998). The slope of the straight line is used in a calculation to determine the transmissivity of the aquifer. The length of the well screen was assumed to be the characteristic thickness of the aquifer, and this length was used to calculate the hydraulic conductivity from the transmissivity. Three Hvorslev equations were used while using AQTESOLVTM under three different conditions: partially penetrating wells within confined aquifer; a well abutting a confined aquifer; and a fully penetrating well within a confined or unconfined aquifer. The equations are listed below: (1) Hvorslev’s equation for a partially penetrating well not in contact with an impermeable boundary. ln(𝐻𝐻0 )−ln(𝐻𝐻)=2𝐾𝐾𝑟𝑟𝐿𝐿𝐿𝐿𝑟𝑟𝑐𝑐2 ln(𝐿𝐿2𝑟𝑟𝑤𝑤𝑤𝑤+�1 +(𝐿𝐿2𝑟𝑟𝑤𝑤𝑤𝑤)2 𝑟𝑟𝑤𝑤𝑤𝑤=𝑟𝑟𝑤𝑤�𝐾𝐾𝑧𝑧/𝐾𝐾𝑟𝑟 (2) Hvorslev’s equation for a well abutting a confining unit. ln(𝐻𝐻0 )−ln(𝐻𝐻)=2𝐾𝐾𝑟𝑟𝐿𝐿𝐿𝐿𝑟𝑟𝑐𝑐2 ln(200) (3) Hvorslev’s equation for a fully penetrating well in an unconfined or confined aquifer. ln(𝐻𝐻0 )−ln(𝐻𝐻)=2𝐾𝐾𝑟𝑟𝐿𝐿𝐿𝐿𝑟𝑟𝑐𝑐2 ln(𝐿𝐿2𝑟𝑟𝑤𝑤𝑤𝑤+�1 +(𝐿𝐿2𝑟𝑟𝑤𝑤𝑤𝑤)2 Appendix G - Methodology Duke Energy Progress – Roxboro Steam Electric Plant Comprehensive Site Assessment Update 13 of 16 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\CSA Update Oct 2017\Draft Final 10_20_2017\Appendices\Appendix G\Methodology.docx where: 𝐻𝐻0 = initial displacement at t=0 [L] H = displacement at time t [L] 𝐾𝐾𝑟𝑟 = radial (horizontal) hydraulic conductivity [L/T] L = screen length [L] t = elapsed time since initiation of the test [T] 𝑟𝑟𝑐𝑐 = nominal casing radius [L] 𝑟𝑟𝑤𝑤 = well radius [L] 𝐾𝐾𝑧𝑧 = vertical hydraulic conductivity [L/T] The hydraulic head data obtained during slug tests from this investigation could always be approximated by a straight line, but the degree of approximation varied between the tests. A concave-upward curvature of the slug test data was common, and this could result from storage processes in the aquifer (Butler, 1998)—in general, storage is ignored in the Hvorslev analysis. In such cases, the two most common approaches to fit a straight line to the plotted curve for the Hvorslev method were exercised (Butler, 1998). The most common approach matches the early time data of the slug test while ignoring the late time data where the curvature is typically manifested. Another approach breaks up the curve into two separate line segments and the analysis uses the slope of the second linear segment. This approach was applied when the slug test was affected by storage in a well sand pack, which affected the early response of the test. 3.0 Screening Level Risk Assessments To support the groundwater assessment, potential risks to human health and the environment were assessed in accordance with applicable federal and state guidance. Screening level human health and ecological risk assessments were conducted that included development of conceptual exposure models (CEM) to serve as the foundation for evaluating potential risks to human and ecological receptors. The purpose of the human health and ecological CEMs was to identify potentially complete exposure pathways to environmental media associated with the site and to specify the types of exposure scenarios relevant to include in the risk analysis. Potential exposure pathways were considered complete when all of the following elements applied: 1) a constituent source; 2) mechanisms of constituent release and transport from the source area to an environmental medium; and 3) feasible routes of potential exposure at the point of contact (e.g., ingestion, inhalation, dermal or ambient contact). Maximum constituent concentrations were compared to appropriate risk-based screening values as a preliminary step in evaluating potential for risks to human and ecological receptors. Based on results of the Appendix G - Methodology Duke Energy Progress – Roxboro Steam Electric Plant Comprehensive Site Assessment Update 14 of 16 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\CSA Update Oct 2017\Draft Final 10_20_2017\Appendices\Appendix G\Methodology.docx screening level risk assessments, a refinement of COPCs will be conducted and more definitive risk characterization will be performed as part of the corrective action process if needed. 3.1 Human Health Risk Assessment The screening level human health risk assessment process involved comparison of constituent concentrations in various media to the following risk-based screening criteria: Soil analytical results collected from the 0 to 2 foot depth interval compared to US EPA residential and industrial soil Regional Screening Levels (RSLs) (US EPA, June 2015); Groundwater results compared to NCDENR Title 15A, Subchapter 2L Standards (NCDENR, 2006); Surface water analytical results compared to North Carolina surface water standards (Subchapter 2B) and US EPA national recommended water quality criteria (NCDENR, 2007; US EPA, 2006). The surface water classification as it pertains to drinking water supply, aquatic life, high/exceptional quality designations and other requirements for other activities (e.g., landfill permits, NPDES wastewater discharges) were noted; Sediment results compared to US EPA residential and industrial soil RSLs (US EPA, October 2014 or latest update); and Sediment, soil and ground water results compared to available local, regional and national background sediment, soil and ground water data, as available. If warranted as part of corrective action decisions, site and media specific risk-based remediation standards can be calculated in accordance with the Eligibility Requirements and Procedures for Risk-Based Remediation of Industrial Sites Pursuant to N.C.G.S. 130A-310.65 to 310.77, North Carolina Department of Environment and Natural Resources, Division of Waste Management, 29 July 2011. 3.2 Ecological Risk Assessment The screening level ecological risk assessment (SLERA) for the site included a description of the ecological setting and development of the ecological CEM specific to the ecological communities and receptors potentially exposed to site-related COPCs. A list of potential ecological receptors (e.g., plants, benthic invertebrates, fish, mammals, birds, etc.) was compiled, as well as identification of sensitive ecological populations and Appendix G - Methodology Duke Energy Progress – Roxboro Steam Electric Plant Comprehensive Site Assessment Update 15 of 16 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\CSA Update Oct 2017\Draft Final 10_20_2017\Appendices\Appendix G\Methodology.docx critical habitat based on information from the North Carolina Natural Heritage Program, and U.S. Fish and Wildlife Service. Step 1 of the SLERA consisted of completion of an ecological checklist as required by Guidelines for Performing Screening Level Ecological Risk Assessment within North Carolina (NCDENR, 2003). Step 2 of the SLERA consisted of performing screening level exposure estimates and risk calculations. This involved comparison of maximum detected concentrations or maximum detection limits for non-detected constituents to applicable ecological screening values (ESVs) intended to be protective of ecological receptors. If exposure concentrations exceeded ESVs, potential ecological impacts could not be ruled out. The following ESV sources were used in the SLERA: US EPA Ecological Soil Screening Levels; US EPA Region 4 Recommended Ecological Screening Values; and US EPA National Recommended Water Quality Criteria and North Carolina Standards. Constituents were identified as a Step 2 COPCs as follows: Category 1 – Constituents whose maximum detection exceeded the media-specific ESV; Category 2 – Constituents that generated a laboratory sample quantitation limit that exceeded the US EPA Region IV media-specific ESV; Category 3 – Constituents with no US EPA Region IV media-specific ESV but were detected above the laboratory sample quantitation limit; Category 4 – Constituents that were not detected above the laboratory sample quantitation limit and had no US EPA Region IV media-specific ESV; and Category 5 – Constituents with a sample quantitation limit or maximum detection that exceeded the North Carolina Surface Water Quality Standards. 3.3 Surface Investigation Samples were collected at the ground or water surface to support the screening level risk assessment. Samples were collected wearing nitrile gloves. Appendix G - Methodology Duke Energy Progress – Roxboro Steam Electric Plant Comprehensive Site Assessment Update 16 of 16 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\CSA Update Oct 2017\Draft Final 10_20_2017\Appendices\Appendix G\Methodology.docx 3.3.1 Surface Water Sampling Surface water samples were collected to assess groundwater to surface water pathways and evaluate surface water quality. Sample jars that did not contain a preservative were used to collect the water directly from the source. The water was decanted from the sample jars into the jars that required preservative. Stream flow measurements were recorded at the time of sampling with the exception of measurements within major waterways. 3.3.2 Sediment Sampling Sediment samples were collected from the bed surface and co-located with surface and seep samples to evaluate sediment quality and provide data to be used in the screening level risk assessment. Where possible, samples were collected directly into sample jars. If surface water was too deep to safely collect sediment samples directly, sediment was obtained using a sampling dredge. 3.3.3 Seep Sampling Seep samples were collected wearing nitrile gloves to assess groundwater to surface water pathways at the site and support the human health and ecological risk assessment. Seep flow measurements were recorded at the time of sampling. Procedures for seep sampling are found in Duke Energy’s Standard Operating Procedure for Seep Sampling, dated 3/24/2016.