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MAR 2? '93 09:52 ALTON G IENCE 5106826921 P.7 WELL DEVELOPMENT AND SAMPLING PROCEDURES, AND FIELD SURVEY FORMS t i All development, purging, and ground water sampling equipment is cleaned prior to use to minimize cross-contamination between wells. All equipment in contact with ground water will be triple-rinsed prior to each sampling event in successive baths consisting of an Alconox solution, and two baths of tap water. ': Monitoring wells will be initially developed by surge block and removing as many as 10 casing volumes. All wells will be inspected for the presence of free product using an electronic interface probe prior to purging, During purging, pH, temperature, and electroconductivity are measured periodically until these parameters stabilize, indicating that formation water has entered the well casing. Pigged water will be pumped into a barrels prior to disposal or recycling at an appropriate waste disposal facility. Prior to sampling, monitoring wells will be purged of as many as 4 casing volumes, or until pH, temperature, and electroconductivity parameters stabilized. Ground `water samples will be ; collected by lowering a disposable 2-inch-diameter, bottom-fill, polyethylene bailer just below the water level in the well. Tl e samples will be carefully transferred from the check-valve-equipped bailer to zero�headspace, 40-milliliter glass containers fitted with Teflon-sealed caps and 1-liter arnber glass containers fitted with Teflon-sealed caps. All 40-milliliter samples are inverted to ensure that entrapped air is not present. Each sample will be labeled with sample number, well number, sample date, and sampler's initials. The samples will remain on ice prior to and during transport to a California-certified laboratory for analysis in accordance with proper chain of custody documentation. i i 6