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Y v, M I i F.5 } , EVAX Project 2260-03 6 May 1941 Wel] Construction Hazmat installed the wells on March 28, 1991 under the supervision of the _ geologist. Flush thread jointed, Schedule 40, polyvinyl chloride (PVC) casing of 2-inch diameter was installed in each boring. In accordance with the vapor-extraction systera design, the base of MW-25 casing was set _ at a depth of 77 feet below ground surface. The lower 35-foot section of MW-25 casing (from 77 to 42 feet) was screened with 0.020-inch slots and the remaining section of the casing was solid. The base of VW-26 casing was set at 59 feet below ground surface. The lower 30-foot section of VW-26 casing (from 59 to 29 feet) was screened with 0.020-inch slots and the remaining casing section was solid. A well cap was slipped on to the base of the casing of each well. The annular space between the well casing and borehole wall was filled with the following materials. No. 3 Monterey Type sand was poured into the annular space from the base of each well to approximately 2 to 3 feet above the top of the screened well casing. A layer of bentonite pellets, 2 to 3 feet thick, was placed above the sand pack and clean water was added to hydrate the bentonite. The remaining annulus (approximately the «•__ top 38-foot section of MW-25 and 25-foot section of VW-26) was then filled with neat cement grout. A traffic rated utility box was placed around the wellhead and set in concrete even with the ground surfGre. A locking well cap was placed on the wellhead. On March 29, 1941, Hazmat developed MW-25 manually with a bailer ar;d surge block. Hazmat reported 40 gallons of water were bailed from the well and stored on-site in a 55-gallon capacity steel drum. Water Sampling i-2 EVAX sampled MW-25 on April 3, 199I. Sampling activities included depth to water measurement, subjective evaluation, and purging and sampling € groundwater for laboratory analysis. Depth to water was measured to the nearest 0.01 foot with a Solinst electronic water-level indicator. r Subjective evaluation consisted of lowering a clean Teflon bailer approximately half its length past the air-water interface. The bailer . j was then retrieved from the well and water was examined for possible evidence of petroleum hydrocarbon product such as floating product, sheen, or odor. Following subjective evaluation, MW-25 was purged of approximately 15 gallons using a bailer. After the water level in the well recovered to at least 80% of the static level, a water sample was retrieved from the ! ` well using a pre-cleaned bailer as explained above. Water from the bailer was transferred into 40-m1, volatile organic analysis (VOA),_..gl..ass_.__..____.._—_____________ — —— -- -- - -- -vials--and a----i-1 C amber— glass-bottle.: The .glass containers were..then - 3 MQ