ARCHIVED REPORTS XR0007845 - Laserfiche WebLink

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• w Ms Lon Duncan August 15, 2000 page 2 of 4 significantly impacted by petroleum hydrocarbons, volatile organic compounds(VOCs), and lead The vertical extent of soil contamination has been defined No contaminants were detected deeper .�Jthan 31 feet below ground surface (bgs) The lateral extent of soil contamination has been defined to �� the north, south and east, and appears to be linuted to the west Impacted soil at the site appears to 31,41,extend no more than 20 feet north, 20 feet west, or 10 feet southwest of the former UST location The estimated extent of soil contamination is shown on Figure 3 Soil analytical results are summarized on Table 2 Contaminant concentrations in groundwater appear to diminish appreciably within relatively close proximity to the former UST The extent of groundwater contamination has not been completely defined However, analytical results infer that the contaminant plume is localized, and is essentially bounded to the north by borings SB7 and S138 approximately 35 feet north of the former UST Based upon San Joaquin County groundwater flow maps and recent analytical data it appears that groundwater flow at the site is generally in a northeasterly direction However, capillary zone soil contamination present in only borings SBI and SB6 suggests a northerly flow The estimated extent of shallow groundwater contamination beneath the site is shown on Figure 4 Groundwater analytical results are summarized in Table 3 WORKPLAN To further evaluate the nature and extent of groundwater impact on the property Ground Zero proposes the following scope of work Drilling, Well Construction and Soil Sampling Four monitoring wells will be installed at the site at the approximate locations shown on Figure 5 A C-57 licensed drilling contractor will advance soil borings using a limited access ng equipped with 8" diameter hollow stem augers The wells will be completed to depths of approximately 32 feet below ground surface (bgs) and will be constructed of 2-inch diameter, Schedule 40 PVC casing and 0 020" slotted screen Due to the wide range of initial and apparent static water levels (ranging from 10 to 22 feet bgs) encountered in bonngs advanced to date, the wells will be screened from approximately 7 feet to 32 feet bgs The filter pack will consist of No 2112 Monterey sand from the bottom of the wells to approximately 1 '/2 feet above the top of the screens The remaining annulus will be completed with 2 feet of hydrated bentonite overlain by neat cement grout At the surface each well will be fitted with a locking cap and water tight, traffic rated well box Drilling and well installation will be conducted under the supervision of an experienced geologist Soil samples will be collected at five-foot intervals using a split spoon style core sampler lined with brass or stainless steel sleeves Soil samples will be collected for field screening, logging and identification in accordance with ASTM Designation D2488-90, which is equivalent to the Unified Soil Classification System The portion of the sample to be analyzed will be immediately be capped, segregated and preserved by placing in an ice chest at a temperature of approximately 4° G 1DatalC ROIJNDZEIGABBARDIrepoMi MW_WORKPLAN dot,