ARCHIVED REPORTS_XR0004864 - Laserfiche WebLink

Home Browse Search

conducted after obtaining approval from PHSIEHD personnel. The locations of the potholes are shown on Figures 2, 3 and 4. • A total of seven potholes were excavated. The potholes were advanced to depths between 15 and ' 22 feet below the ground surface (bgs), with most averaging 18 feet bgs. Soil samples were collected at 12 feet, 15 feet and 18 feet bgs. Potholes PH-1 and PH-3 were used to define the limits of the phase II excavation within the limits of the fenceline and the remaining five ' potholes were all excavated outside of the facility's fenceline. The soil samples collected from PH-1 and PH-3 were redesignated as sidewall (SW) samples as they were used to define the 1 limits of the phase II excavation. Upon completion, each of the potholes was backfilled using the materials removed during ' excavation and compacted to the pre-existing surface grade. 3.6 Remediation of Excavated Soil Contaminated soils were transported to a temporary storage area located on the west end of the ' property near MacArthur Drive. The soils were placed on top of plastic sheeting to prevent the vertical migration of contaminants into native soil. Stockpiled soils not undergoing active j aeration were also covered with plastic sheeting. ' Approval was granted by the San Joaquin Valley Unified Air Pollution Control District (APCD) to aerate the soils on-site (Appendix B). Based upon analytical laboratory data collected during '. previous soil investigations, it was determined that up to 30 cubic yards of gasoline contaminated soil could be placed into the active aeration pile per day. Soils were moved onto the active aeration pad from the stockpile using a bulldozer. The soil was spread into a thin layer between six and twelve inches in thickness and allowed to air dry. As the soil dried, the material was mechanically turned using a disc pulled by the bulldozer. Initially, the soil was turned on a daily basis. As the remediation progressed, mechanical turning was reduced to two or three days per week. A PID has been used to monitor volatile levels during the remediation process. When the PID readings indicate attainment of field based target levels, confirmation samples will be collected ' for Iaboratory analyses. One two-point composite sample will be collected for every 200 cubic yards of remediated soil. Soils that have attained non detectable gasoline and BTEX Ievels will be removed from the aeration program and prepared for on-site reuse. ' Based on current treatment rates and weather conditions, it is anticipated that the soil aeration program will be completed by the end of September, 1998. If confirmation sampling indicates ' that contaminant levels have been reduced to those suitable for on-site reuse of the treated soil, a letter requesting such approval will be prepared. American Geological Services,Inc. CA9517E-029 9