ARCHIVED REPORTS_ROY'S AUTO - HISTORICAL

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ROM Ground sero Analysis PHONE No. : 209 952 9892 S,--P- 11 1995 03:35PM P3 • The shallow stratigraphy at the site location consists of dark brown to black, organic rich clay from the surface to a depth of approximately 2-3 ft. Underlying this is a brown silty clay/clayey silt to a depth of approximately 7-8 ft. Beneath the brown clay, a red orange silt is present to the depth of 10, the maximum depth explored. * Based on published data, the current depth to groundwater beneath the site is estimated to be approximately 65 feet. Historical high groundwater (spring 19$6) is estimated to have been approximately 50 feet below grade. * It is our understanding that Caltrans excavated and removed Suspected contaminated soil from the ROW, l�ml�m_ lka las for the Sampling Plan * The data indicate that certain areas on the Roy's 'Towing property and the Caltrans ROW were impacted by petroleum hydrocarbons and/or lead, Gasoline range hydrocarbons and BTEX constituents were essentially absent. Contamination identified to date appears to have been confined to the uppermost 2 to 3 feet of the soil column. With the exception of the sump arca, contamination apparently resulted from surface spillage. The lack of significant vertical contaminant migration is most likely attributable to the organic rich surface soil type which would tend to adsorb hydrocarbons. As a result of vegetable matter content,organic soils are also notorious for providing false positives when analyzed for the heavier hydrocarbons such as TRPH and TPHd, * Based on these characteristics, most of the proposed sampling plan focuses on the analysis of near surface soil samples with the option of analyzing deeper samples if appropriate. Due to the greater potential for vertical migration all samples collected from beneath the sump and leachfield will be analyzed, Untline of Pr000sed coil Same ing Pian * A total of five (5) sampling locations are proposed for the "focused" investigation. Three (3) of these will be north and west of the warehouse and former mechanic's shop, in the arca where staining was observed and elevated levels of petroleum hydrocarbons and lead were detected (Kaldveer's "areas of concern # I and #II"). Two (2) sampling points will be located in the southeastern portion of the site near the areas identified by Kaldveer as "area of concern,-# III". Soil samples will be collected from depths of 1 foot and 5 feet. All samples from 1 foot will be analyzed for TRPH and total lead. The samples from 5 feet will be held by the laboratory and analyzed if needed to define the vertical limits of any contamination identified. * A total of four (4) sampling points will focus on the sump and leachfeld. One (1) sampling point will be from soil beneath the sump. One (1) sampling point will be near the south wall of the warehouse where the drain line from the sump has been exposed. Two (2) sampling points will be in the presumed leachfield area:, south of the warehouse,