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June 26, 1992 ARCO Service Station No. 549, Stockton, California Ground-Water Monitoring Well Develo ment Before developing the wells, static water levels were measured using a Solinst water-level meter. Following initial water-levels measurements, the water in the wells were examined for subjective evidence of hydrocarbons by lowering about half the length of a Teflon bailer past the air-water interface. The sample is retrieved and inspected for floating product, sheen,emulsion, color, and clarity. The thickness of floating product detected was recorded to the nearest 1/8-inch. Monitoring wells that did not contain floating product were developed using a 4-inch-diameter PVC surge block alternately raised and lowered through the water column in each well. Development is performed to remove the fine-grained sediment from the monitoring well. Ground-Water Samplin The static water level in each well was measured to the nearest 0.01-foot with a Solinst water-level sounder cleaned with industrial soap and water before use in each well. A clean bailer was used to obtain a sample from the surface of the water in each well. The sample was retrieved and inspected for floating product, sheen, emulsion, color, and clarity. The thickness of floating product detected was recorded to the nearest 1/8-inch. Wells that did not contain floating product were purged using a 3.5-inch-diameter stainless- steel electric submersible pump. The pump, cables, and hoses were cleaned with industrial soap and water before use in each well. The wells were purged until withdrawal is of sufficient duration to result in a stabilized pH, temperature, and electrical conductivity of the water measured using portable meters calibrated to a standard buffer and conductivity standard. If the well was dewatered, the water level was allowed to recover to at least 80 percent of the initial water level. Before collecting each groundwater sample, a Teflon bailer was cleaned with industrial soap and rinsed with tap water and deionized water, and the sampler changes latex gloves. The appropriate preservative (concentrated sulfuric, nitric, or hydrochloric acid) was added to each sample bottle as required for the preservation of the sample before laboratory analysis. A sample of the formation water was then collected from the surface of the water in each of the wells using the Teflon bailer. The water samples were sealed in laboratory-cleaned, 40-milliliter glass vials with Teflon-lined lids so that no air bubbles are present. The samples were then labeled and promptly placed in iced storage. Chain of Custody Records were initiated by the field geologist and accompanied the samples to the analytical laboratories. A field log of well evacuation procedures and parameter monitoring was maintained. saooa-a