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JVM ASSOCIATES • WKA No 1735 01 April 22, 1992 Page 3 Analysis of soils samples obtained from shallow depths at the northerly portion of the excavation revealed detectable levels of TPH as motor oil The motor oil is apparently unrelated to the USTs and piping However, some of the motor oil contaminated soil was excavated during this phase of work The shallow motor oil contamination is believed to be the result of past application of asphalt oils to the previously unpaved, gravel covered yard Significant motor oil contamination does not appear to have migrated below two feet, and appeared not to have come from the UST or associated piping Our firm discussed the shallow motor oil contamination with San Joaquin County Public Health Services representative Margaret Lagor;o on July 23, 1991 Ms Lagorto indicated that San Joaquin County PHS would not address contamination unrelated to the former UST's or related piping No additional motor oil contaminated soil was excavated subsequent to this conversation A total of 68 samples were collected during the excavation process Preliminary and final confirmation sample locations are indicated on Plate 8, a summary of excavation sample results and collection depths is presented in Tables 3 through 6 Complete laboratory reports and chain-of-custody documentation are • contained in Appendix C Field methods and sample collection and preservation techniques are described in detail in Appendix D The excavation reached a maximum depth of 36 feet below surface grade in the area directly beneath the old dispenser island The excavation extended in a northeasterly direction approximately 130 feet with a width ranging from 15 to 45 feet Plate 9 shows two interpretive cross-section diagrams of the excavation Excavation Backfill Verbal authorization was obtained from the San Joaquin County PHS on July 8, 1991 to backfill the UST portion of the excavation using pea gravel Pea gravel was used in the excavation based on availability, cost and compaction considerations Pea gravel was placed in the excavation to a depth of approximately ten feet below grade The pea gravel was overlain by clean imported fill, placed in the excavation in one to two foot lifts and compacted to at least 90 percent relative compaction, based on the ASTM D1557-78 standard The excavation area was paved with one foot of aggregate base rock compacted to at least 95 percent relative compaction ASTM D1557-78, then covered with asphalt `�W WALLACE•KUHL Rny Ld pup ErA550C1 - INC