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