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CV = (n)(CD/2)2 (HW)(7.48) where: CV = casing volume (gallons) CD = casing diameter(feet) HW = height of water column within well (feet) 7.48 = conversion from cubic feet to gallons. ® Each well with sufficient recharge was purged of a minimum of three casing volumes and allowed to recover to 80 percent of the original well volume prior to sampling. Slow- recharge wells were purged of a minimum of one well volume and also allowed to recover sufficiently (for a period of no more than two hours) prior to sampling. • To assess the presence of fresh water coming into the well, dissolved oxygen(DO), electrical conductivity (EQ,pH, turbidity, and temperature were monitored after approximately every two to five gallons of purging and were recorded on a Well Data Sheet. Sampling was performed when the total estimated purge volume was reached and the EC,pH,turbidity, and temperature stabilized to within 10%between consecutive readings. • Where a bailer was used for sample collection, a bottom-emptying device was inserted into the bailer, and the sample was transferred from the bailer to the container at a rate so as to minimize aeration. Groundwater Sampling Using Low-Flow Purging Methods • Groundwater monitoring wells that are equipped with dedicated sampling equipment were purged and sampled using low-flow purging methods. • With the weighted water-level meter in the well,the submersible pump was operated at a discharge rate that would minimize the decline in water level. • Discharged water was routed through a sampling chamber equipped with probes for measuring DO, EC,pH,turbidity, and temperature. When three consecutive readings of these field parameters had stabilized to within 10% of each other, the water quality was determined to be stable and samples were collected. Groundwater Sampling Collection and Preparation • Samples, including field, trip, and equipment blanks,were collected in approved sample containers (Table 1), and each container was filled completely and immediately capped, labeled, and placed in a cooler with ice. Samples for VOC analysis were filled by pouring the sample down the side of the container to minimize aeration and capped with no airspace. • Collected samples, accompanied by a trip blank, were placed immediately in an ice-filled cooler for transport to a state-certified testing laboratory. Samples were kept chilled(at about 4°C)until delivery. 2 WK—SAplan.doex Geologic Associates