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CV = () (CD/2)2 (HW)(7.48) <br /> where: <br /> CV = casing volume (gallons) <br /> CD = casing diameter (feet) <br /> HW = height of water column within well (feet) <br /> 7.48 = conversion from cubic feet to gallons. <br /> <br />• A YSI 3560 Water Quality Meter® (or equivalent) was used to measure oxygen reduction <br />potential (ORP), pH, specific conductance (EC), temperature, and turbidity. After <br />approximately every casing volume of purging, field parameters were recorded on a Well <br />Data Sheet. Sampling was performed when the total estimated purge volume was reached. <br />• The pumping rate is reduced during evacuation of the last casing volume so that sampled <br />water is not subject to unnecessary agitation. If a bailer is used, the bailer is slowly lowered <br />to minimize agitation of the water column. <br /> <br />Groundwater Sampling Using Low-Flow (Micro Purge) Methods <br /> <br />For groundwater monitoring wells at the Austin Unit equipped with dedicated bladder pumps, <br />groundwater sampling was performed using low-flow (micro purge) methods described below. <br /> <br />• In order to minimize a decline in water level, the bladder pump was operated at a discharge <br />rate of 1 liter per minute or less. <br />• A weighted water-level meter was used to measure water levels in the well during purging. <br />Water levels were recorded on a Well Data Sheet along with water quality parameters. <br />• To assess the presence of fresh water coming into the well, discharged water was routed <br />through a flow cell attached to a YSI 3560 Water Quality Meter® (or equivalent) equipped <br />with probes for measuring ORP, pH, specific conductance, temperature, and turbidity. <br />When three consecutive readings of these field parameters had stabilized to within the <br />established criteria listed in the table below, the water quality was considered to be stable <br />and samples were collected. <br /> <br />CONSTITUENT CRITERIA <br />Turbidity ± 10% of reading <br />ORP (redox) ± 20 mv <br />Specific Conductance ± 10% of reading <br />Temperature ± 0.2 degrees Celsius <br />pH ± 0.2 units, <br /> <br />Domestic Well Sampling Methods <br /> <br />For domestic wells the water was left to run for approximately 30 minutes prior to sample <br />collection. At the time of sampling, a YSI 3560 Water Quality Meter® (or equivalent) was used <br />to measure field parameters (EC, pH, temperature, and turbidity) and recorded on a Well Data <br />Sheet.