2024-01-31_REVISION - M1977344 (30)

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Red Creek Quarry Baseline Surface Water and Groundwater Sampling and Analysis Plan Section 4: Groundwater Monitoring 4-2 • Collecting samples for laboratory analysis (see Section 4.3.2 below for further detail) 4.3.1 Sampling Methods A general site inspection will be performed upon arrival at each monitoring well and comments regarding site conditions will be recorded on the field sampling record. An example field sampling record for groundwater is included in SOP-6 (Appendix C). Field Instrument Calibration. The field parameter instruments will be rented from an environmental equipment company. Rented equipment will be checked to verify it is cleaned and calibrated. If field equipment is used over multiple days, the equipment will be recalibrated at the beginning of each day according to the manufacturer’s specifications using the water quality equipment calibration form located in Appendix C (SOP-2). A drift check will be performed if there are indications that the equipment is not performing normally or is subjected to adverse conditions (e.g., extreme cold); recalibration will be performed for parameter readings that are outside of acceptable performance limits. If a drift check indicates that the instrument is outside of acceptable performance limits, field staff will qualify the field data collected prior to the drift check. Water Level Measurements. Depth to water will be measured to the nearest 0.01 ft from the top of the well casing using an electrical water level sounder before sampling the well. The water level sounder will be cleaned with an environmental-grade detergent (Alconox or Liquinox) at the beginning or end of each sampling day. All parts of the sounder that will contact groundwater will be rinsed with distilled water before placement in each well. Monitoring Well Purge Methods. All monitoring wells will be purged and sampled using standard purging methods or micro-purge (i.e., low-flow) sampling methods when possible SOP-6 (Appendix C). The low- flow sampling method relies on low pumping rates (typically 0.1 to 0.5 liter per minute) from a sampling pump located near the middle of the well screen interval to draw a representative sample of formation water into the pump intake with minimal disturbance of water in the well casing. The protocol for this method requires that water levels in the well be monitored during sampling with the goal of inducing less than 0.3 ft of drawdown. If low-flow sampling is not possible, the well will be purged by bailing until either three well volumes of water have been removed or as much of the water within the well as practical has been removed. Water quality parameters for pH, SC, DO, ORP, temperature, and turbidity will be monitored during purging. Purging will be considered complete when turbidity is less than 10 nephelometric turbidity units and three successive readings for pH, SC, ORP, and DO are within 0.1 standard unit, 3 percent, 10 millivolts, and 10 percent, respectively. Stabilization of all parameters may not be achievable in some wells; protocols for this occurrence are outlined in SOP-6 (Appendix C). Groundwater Sample Collection. Certified-clean bottles obtained from the analytical laboratory or commercial bottle supplier will be used to collect samples. Samples for dissolved constituents will be filtered (0.45 µm) prior to collection in the preserved sample bottles provided by the analytical laboratory. All sample containers will be clearly labeled with the well ID, date and time of sample collection, filtered or unfiltered condition, preservatives, and the sampler’s initials. Samples will be kept cool (less than or equal to 6 degrees Celsius [°C]) from the time of collection to receipt by the analytical laboratory. COC forms and custody seals provided by the laboratory will be used for all samples shipped to the laboratory. The analytical suite for groundwater samples are summarized in Appendix A. SOPs for sample collection and handling are provided in Appendix C (SOP-4 and SOP-6). Groundwater samples will also be collected for QA/QC purposes, as outlined in the QAPP (Appendix B). For each sampling round, groundwater blind duplicate samples will be collected at a frequency 1 duplicate sample per event.