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f 4 KLEINFELDER • RECOMMENDATIONS Based on the above results and assuming the second set of groundwater samples does not contain the above analytes, Kleinfelder recommends destroying the monitoring wells (after receipt of the data and regulatory approval), removing the impacted soil, and collecting verification samples from the excavation to confirm the removal The impacted soil can be stockpiled at an appropriate and convenient on-site location After sampling the stockpile, final remediation/disposition of the soil can be considered Monitoring Well Destruction Each of the monitoring wells will be destroyed by overdnlhng the existing well and removing the casing The resultant borehole will be backfilled through tremae pipe with a 4% bentonite grout to approximately 28 feet below ground surface (bgs). From approximately 28 feet bgs to surface, the boreholes will be backfilled with bentonite pellets. After each bucket of pellets, approximately 2 gallons of potable water will be added to hydrate the bentonite Impacted Soil Removal Impacted soil will be excavated Based on the above results, Kleinfelder estimates that approximately 1,000 cubic yards (on deck) of soil have been impacted by petroleum hydrocarbons to a maximum depth of nearly 30 feet. In addition, approximately 1,000 cubic yards (on deck) of non-impacted soil will need to be removed to expose portions of the impacted soil . Soil being removed will be qualitatively screened with a PID or a flame-ionization detector (FID). Soil with qualitative readings less than 50 ppmv will be stockpiled near the site for use in backfilling the excavation Soil with qualitative readings greater than 50 ppmv will be stockpiled at an on-site location designated by the San Joaquin County Department of Capital Projects One soil sample per each approximately 100 cubic yards will be collected to assist in the final disposition of the soil The impacted soil will be covered with plastic pending receipt and review of the analytical data Verification samples will be collected from the excavation Due to the anticipated depth of the excavation, the samples will be collected out of the bucket of the excavator One sample will be collected per each approximately 20 lineal feet of sidewall and one sample will be collected per each approximately 100 square feet of excavation bottom Each sample will be collected by driving a 6-inch brass (or stainless steel) tube into the soil Upon removal, the tube will be immediately sealed with Teflon sheeting and plastic caps, labeled, logged on a chain-of- custody, and placed in an iced cooler for transport to Superior Each of the samples will be analyzed for TPH-D TPH-G ► BTEX The samples may be analyzed on a rush turnaround schedule A copy of the analytical report will be sent directly to the San Joaquin County Public Health Department, Environmental Health Division • FWP3-2(1993) Page 3 of 4 24-220152-D00 Copynght 1993 Kleinfelder, Inc