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I N- Effl-al _ rL,MA -�, MAN - - T I 4I Quik Stop Market N-o. 132 September 19, 1990 Project No.349132-3I Page 6 RECOMMENDATIONS Exceltech recommends that laboratory detected hydrocarbon contaminated soil be removed as soon as ssible beginning � F Po� in the area of boring 13-3 (Figure 2). Eiccavation would continue until no further detectable hydrocarbons are found. Samples will be field tested with a PID and confirmatory samples will be sent to a state-certified laboratory. Laboratory samples will be taken from the base and along the sidewalls of the excavation as near to 15 foot depth using the "backhoe bucket" method. The excavation will be terminated at this depth to avoid encountering groundwater.Since the primary detectable soil contamination is found below ten foot depth,the relatively uncontaminated upper soil will b stockpiled on plastic separate from the contaminated soil. Confirmatory sampling of"clean"soil will be sent to a state-certified laboratory,after which its proper disposal can be decided according . to San Joaquin County Health Service;sm.cifications. If needed,the fuel storage tanks can be removed to allow excavation in that area to continue. Exceltech does not foresee this necessity. After the contaminated soil is removed,the excavation will be bacldilled with the r clean soil and import as needed: � �. y = Exceltech further recommends the destruction of monitoring well MW-I. There i t possibility that its construction makes possible the cross-contamination of a,potential~' contaminated upper perch zone of water with the underlying aquifer. MW-I will be F removed with a 10 inch diameter hollow-stem auger drilling over the well. The new boring t will extend below the previous boring MW-1, assuring that all of the well construction material is removed. The boring will then be sealed to grade with a neat cement and bentonite grout. It may then be necessary to replace monitoring well MW I with two other wells, one screened for the upper perched zone and the second screened for the lower aquifer. The new wells will be,constructed in the same r canner as the previous wells. L14MITATIONS The discussion and recommendations presented in this report are based on the followi,��k- 1. The observations by field personnel. 2. The results of laboratery analyses performed by a state-certified laboratory. . 1 Our understanding of the regulations of the State of California and San Joaquin County. It is possible that variations in the soil and groundwater conditions could exist beyond the points explored in this investigation. Also, changes in the groundwater conditions could occur at some time in the future clue io variations in rainfall, temperature, regional water usage,or other factors.