Laserfiche WebLink
PROBLEM ASSESSMENT REPORT <br /> 1806 South EI Daredo Street Stockton California <br /> 1� 4.0 SITE ASSESSMENT <br /> 4 1 Site Subsurface Soil Conditions <br /> Subsurface soil conditions are indicated on cross-section A-A' (Figure 4) The cross- <br /> section location is shown on Figure 2 The subsurface profile generally consists of- <br /> • silt clay and clayey sand fill material, extending from the surface to <br /> Y Y Y Y 9 <br /> approximately 2 feet bs (fill to 16 feet bs within the former tank basin), <br /> possibly to 9-10 feet in the area of MW-3, <br /> I • silty clay to clayey silt to a depth of approximately 25-30 feet bs, <br /> • a silty to clayey sand layer extending from approximately 25-30 to 35 <br />' feet bs, <br /> • silty clay to clayey silt extending to the maximum drilled depth of <br /> approximately 60 feet bs, except for a possibly discontinuous silty fine <br /> sand layer extending from approximately 50 to 55 feet bs <br /> The cross section indicates the subsurface is generally silts and clays with some sandy <br /> intervals <br /> I4 2 Distribution of Petroleum Hydrocarbons Soil <br /> Figures 3, 4, and 5 show the distribution and estimated lateral and vertical extent of <br /> petroleum hydrocarbons in the soil The impacted soil appears to be limited to the <br /> former UST basin backfill and native soils immediately beneath the former tanks <br /> Petroleum hydrocarbons in the native soil extend from approximately 16 to 36 feet bs <br /> 4 3 Site Groundwater Conditions <br /> Depth-to-groundwater measurements have been collected quarterly by Aegis personnel <br /> since July 1991 Depth to groundwater in the monitoring wells on site has varied <br /> from approximately 42 to 48 feet bs (Table 5) Groundwater flow direction has <br /> remained relatively consistent to the east-northeast, at an average gradient of <br /> approximately 0 001 ft/ft (Figure 7) <br /> 4 4 Distribution of Petroleum Hydrocarbons- Groundwater <br /> Figure 8 indicates the distribution of TPH as gasoline and benzene in groundwater on <br /> June 21 , 1993 As shown on the figure, the highest benzene concentration was in <br /> the groundwater sample from well MW-2, upgradient of the tank basin All of the <br /> 91 044A PAR 9 <br />