ARCHIVED REPORTS_XR0008769 - Laserfiche WebLink

Home Browse Search

Page 2 - January 30, 1992 Job No 400511-SA In 1985, it was discovered by Kayo Oil Company that the station's underground tanks were apparently leaking gasoline The station has been out of service since 1985 The station's underground storage tanks were removed in 1987 -The-initial-drilling program at-the site-was-performed-by-IT—Corporation-on February-27;-1985 to ----- ' provide basic subsurface soil and hydrogeologic information Four boreholes (DH-1, DH-2,DH-3, and DH-4) were drilled and backfilled in this initial phase of investigation Their study reported the soil ' contained benzene at levels as high as 160,000 parts per billion (ppb) in the area of VW-32 A second drilling program was performed by Tr Corporation on March 26 and 29, 1985, the objective of which was to determine the extent of the hydrocarbon plume discovered in the initial drilling phase Four ' vadose zone monitoring wells(MW-1, MW-2, MW-3, and MW-4)were drilled and installed at that tune to a depth of 20 feet On May 29, 1985, IT Corporation conducted its third drilling phase to install 1 three wells (MW-5, MW-6; and MW-7) to the groundwater table to determine if the groundwater had been contaminated and to determine the direction of groundwater flow Four additional monitoring wells were installed at the site from (MW-8� MW-9, MW-10, and MW-I1) September'18 through 20, 1985 These wells were installed by the Twining Laboratories, Inc as a subcontractor of Fox Environmental.Services, Inc The purpose of these wells was to further define the extent of soil contamination and assess the groundwater conditions Soil and groundwater samples were collected and the results presented in numerous reports by Fox Environmental Services and the Twining Laboratories Groundwater Technology Inc drilled and installed groundwater monitoring wells MW-12 and MW-14 through MW-23 during a four month period of tune from October 1987 through January 1988 These wells ranged in depth from 50 to 66 feet Monitoring wells MW-12, MW-17, MW-19, MW-20, MW-21, and MW-22 were installed as off-site wells Du Pont Biosystems installed three groundwater remediation wells (RW-24, RW-25, and RW-26) on f September 26 through 29,'1988 The first two-of these wells were completed to a depth of 69 feet,the third well was completed to a depth of 64 feet Soil samples from these wells were collected and analyzed and the results are presented in the report entitled"Quarterly Ground-Water Sampling Report and Additional Well Installation, November 1988, former Econo Gas Station, 4325 East Washington Street, Stockton, California,"-dated February-9, 1989 _ This study reported the-soil contained TPHg at levels as high as 33,000 milligrams per kilogram (mg/kg) in RW-25, 430 mg/kg in RW-24, and 152 mg/kg in RW-26 4005111 Rev 1 Du Pont Environmental Remedlatton Services Pnnted on Recycled Paper