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� - A Er. sa •r: G KLEINFELDER S CONCLUSIONS AND RECOMMENDATIONS Soil and ground water adjacent to the excavation was found to be affected by petroleum hydrocarbons. The lateral extent of impact appears to be limited to the area within 10 to 15 feet north,west, and south of the excavation. The area east of the excLvation could not be investigated because of the presence of the warehouse, and the conditions in this area are not known. The ground water gradient was found to be to the southwest, opposite the regional ground water gradient. A monitoring well was not installed directly downgradient from the excavation,however,soil-gas survey samples downgradient of the excavation did not reveal the presence of petroleum hydrocarbons in the ground water. Analysis of ground water samples indicate that ground water does not appear to be affected by petroleum hydrocarbon constituents 30 feet west of the tank excavation.h oGrounewerd water from MW-1 did appear to be affected by coliform,possibly du The low permeability of the soil, the shallow ground water gradient,and probable gradient ides and/or seasonal variations would affect the rnigration of fluctuatiors due to t ' sible that ground water samples from contaminants in ground water. Therefore, it is pas MW-1, a monitoring well located 30 feet west of the tank excavation, and soil gas sample locations K and F would be affected if contaminants migrated from the tai k excavation. A well southwest of the tank excavation does not appear to be necessary at'his time. Kieinfelder recommends continued monitoring of-the ground water quality and gradient to assess the effects of seasonal variations andr wdie reproducibility of the excavaton also for validity. The need for another monitoring1 sou hwest of the should be evaluated if a sufficient level of reproducibility iltly i affectedsoil and groundane initial dwater ata is validated. Meanwhile, Kleinfeider recommends that around the excavation be remediated. Because of forcombiningoshallow nature the treatmethe ntoof he first soil remediation options should consider options T encountered groundwater. As required, a copy of this report should be submitted to San Joaquin County Public Health Services. S F15-90-101 Copyright 1990 Kteinfelder, Inc.