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Discussion <br /> The site is underlain by silt and sand sediments which are interpreted to be typical of <br /> the alluvial sedimentation in the area. Analytical results show that TPHG and BTEX <br /> were not detected in soil or groundwater. Concentrations of lead are consistent with <br /> background levels observed for soils of the western United States. Microbial activity <br /> -is typical for the area and that activity is interpreted to indicate oxygenated <br /> conditions. Given the sandy sediment and soil, this activity probably has contributed <br /> to the degradation of hydrocarbons in the vicinity of the former UST. Soil vapors <br /> were observed using reconnaissance soil vapor measurements, and since <br /> contaminants were not observed in samples from the borings, indicating a lack of <br /> lateral migration from the leak source. <br /> Interim Soil Vapor Extraction and Surface Treatment <br /> The need for interim soil vapor extraction for site cleanup has been previously stated <br /> by PHS-EHD. At this time, the District has not yet performed soil vapor tests, and a <br /> request for testing has not been forwarded to Wright. <br /> Conclusions ^ <br /> Two exploratory borings were advanced to ascertain the deep of possible contaminant <br /> penetration from a former UST located at the Waterloo School. The results of this <br /> study indicate that the soils within a 12 foot radius to the south and west of the former <br /> UST were not significantly impacted, and that groundwater in the surmised <br /> downgradient direction is not contaminated. Weak field evidence of soil vapors were <br /> encountered in the uppermost 30 feet of soil where previous investigations have <br /> observed soil contamination. One groundwater monitoring well was installed along <br /> with one shallow vapor well, and the existing vapor well was modified to allow for an <br /> initial soil vapor recovery program in the upper soils. Samples of microbial activity <br /> indicate that these soils would support biodegradation of hydrocarbons, and <br /> biodegradation is interpreted to have occurred since the initial leak. <br /> Wright recommends that the groundwater monitoring well be monitored biannually <br /> for one year for TPHG and BTEX. We also recommend that the soil vapor test be run to <br /> ascertain whether soil vapor recovery is feasible and cost effective. <br /> Limitations <br /> This report has been prepared for the specifically for the Linden Unified School <br /> District, Waterloo School at 7007 Pezzi Road in Stockton, CA, and was done according to <br /> the State and local agency suggested guidance documents for similar investigations. <br /> The interpretations, conclusions and recommendations made herein are based on the <br /> data and analysis for the soil and water samples collected on-site. Wright <br /> Environmental Services, Inc. is not responsible for errors in laboratory analysis and <br /> reporting, or for information withheld during the course of the study. No warranty <br /> Linden School District 4 <br />