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February 11, 1987 AGS Job 8691-4 Page 3 Applied GeoSystems personnel were present on November 21, 1986 to develop the well and collect samples. The water level was measured and found to be approximately 42 feet below the ground surface. After the initial water level measurement, the well was sampled using an acetone-washed and distilled water-rinsed teflon bailer. The bailer was lowered half-way through the ground water surface to obtain a sample from the surface of the water. The sample was then examined for hydrocarbon odor, sheen, emulsion, or floating product. No evidence of contamination was noted. The well was then developed by air jetting, swabbing, and pumping. The pump used was an air-lift submersible type, and approximately six well volumes were purged from the well. After ground water recovery to static conditions, the bailer was cleaned with acetone and distilled water and the formation water was sampled. Samples for chemical analysis were taken with the bailer by lowering the bailer through the ground water surface to a point approximately 10 feet below the water level. The water samples were slowly transferred to laboratory-cleaned glass vials and sealed with teflon-lined lids, labeled, and immediately placed in iced storage. Chain-of-Custody records for soil and water samples were initiated by the sampler, and accompanied the samples to the analytical laboratory. Copies of the completed Chain-of-Custody records are included in the Appendix of this report. Soil and water samples were delivered to Applied GeoSystems' laboratory for analysis. Analyses requested include total volatile hydrocarbons, total extractable hydrocarbons, and volatile hydrocarbon constituents (benzene, ethylbenzene, toluene, and total xylenes) . The laboratory is certified by the state of California for these types of analyses. Results of these and other analyses from previous phases in the investigation of this site are summarized in Table 1. Copies of the laboratory Record of Analyses are attached. Laboratory analyses indicate that only relatively low levels of hydrocarbons are present in the ground water collected from MW-4. The levels detected are above action levels established by the state of California for benzene and toluene, and are substantially below values detected in monitoring wells MW-1 and MW-2. We thus conclude that the ground water contamination observed in MW-1 and MW-2 has originated on site, and is not due to the service station to the north of the site, which remained a possibility after our previous investigation. .4,op/ied GeoSystems