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A.Taichert&Son Inc.Mobile Equipment Shap 103 N.'E'St.Stockton,CA. Remedial Action Alan March, 1994 hydrocarbon plume, but only one soil sample was collected above the current water table, and the well screen is currently below water table. Historical water sample analysis has indicated detectable concentrations of gasoline constituents in wells MW-10, 11 , 13 and 14. SVE system radius of influence in soil and at the water table should include these data points to remediate contaminated and potentially contaminated areas. 2.0 Results 2_1 Soil Boring and Sampling The upper portion of MW-14 was advanced and sampled through previously emplaced clean backfill. This material was emplaced in the excavation of three former underground storage tanks (UST), containing fuel hydrocarbons and waste oil. The backfill extended to a drilled depth of approximately 37 feet bgs at this location. Soil samples were not retained from this interval for chemical analysis. Seven soil samples were collected from the boring at five-foot intervals from depths of approximately 40 feet to seventy feet bgs. The boring (and well MW-14) extended to approximately 80 feet bgs. Groundwater was encountered under unconfined conditions at approximately 70 feet bgs. Subsurface materials below the backfill at 37 feet bgs included silts, sandy silts, sand and clayey sands. Sand content generally increases with depth, and traces of subanguiar gravel were encountered in the sample from 65 feet bgs. Silts and sandy silts between 40 and sixty feet appeared relatively tight, with abundant fines and weakly developed cementing. Coarser fine sand lithologies below 60 feet contained abundant fines and clay, 1 and were weakly cemented. Headspace evaluation of these samples by hexane-calibrated flame ionizing organic vapor monitor indicated concentrations greater than 10, 000 parts per million volume (ppmv) in the interval between 55 and 70 feet bgs. These samples were characterized by a distinct, pungent gasoline odor. A soil boring log illustrating MW- 14 is included in Appendix B. The monitoring well screened intervals and their relationship to the potentiometric surface are illustrated in Figures 4 and 5. Seven soil samples were retained for chemical analysis by Sparger Technology, a State- Certified analytical laboratory located in Sacramento, California. Analysis of the soil samples indicates concentrations of TPH and BTEX ranging from below detection limits 1 to 1,400 ppm TPH and 20 ppm xylenes. Elevated concentrations of TPH and BTEX occurred in the 50, 55 and 60-foot samples. Measurable concentrations of various BTEX constituents were detected in samples between 50 and 70 feet bgs. Highest concentrations of TPH and BTEX occurred in the 55-foot sample. Soil sample analytical results included in Appendix C are summarized in Table 1. 4 1