ARCHIVED REPORTS_XR0002310 - Laserfiche WebLink

Home Browse Search

ATTACHMENT A SUMMARY OF PREVIOUS INVESTIGATIONS Chevron 9-8632,575 Grant Luce Road,Tracy,CA • In 1964 the product lines and an unspecified number of steel underground storage tanks (USTs)were installed at the site In 1984, the steel USTs and product lines were removed They were replaced with three 10,000-gallon capacity gasoline USTs, and one 1,000-gallon capacity waste oil UST, all of single-wall fiberglass construction In May 1994, the USTs, product lines, hoists, sand/grease trap, and approximately 400 cubic yards of impacted soil generated during excavation activities were removed from the site As approved by San Joaquin County Public Health Services (SJCPHS), slightly impacted soil was aerated to non-detect levels and reused onsite Groundwater was encountered during excavation activities at approximately 8 feet below ground surface (bgs) In August 1994, the waste-oil UST and sump excavations were over-excavated until soil exhibiting low to non-detect levels of oil and grease were encountered Approximately 150 to 200 cubic yards of oil and grease impacted soil was removed and hauled offsite In May 1995, wells MW-1 through MW-4 were installed at the site Maximum concentrations of TPHg and benzene in wet soil'were reported in the area of the former pump islands (boring MW-3) at 7,600 mg/kg at 6 5 feet below ground surface (bgs) and 24mg/kg at 6 5 feet bgs, respectively There are currently four groundwater-monitoring wells located at the site During the second quarter 2001, total petroleum hydrocarbons quantified as diesel (TPHd) were detected in samples from three of the four wells at concentrations ranging from 75 milligrams per liter (µg11) at MW-2 to 530 µg11 at MW-3 Total petroleum hydrocarbons quantified as gasoline (TPHg) were detected in three of four samples at concentrations ranging from 630 µg11 (MW-2) to 2,200 pg/1 (MW-4) Benzene was detected in three of four samples at concentrations ranging from 43 µg/l (MW-2) to 340 µg/1 (MW-4) Methyl- tertiary-butyl-ether (MtBE) was detected in three of the four samples at concentrations ranging from 27 µg/1 (MW-1) to 780 µg/1 (MW-3) Groundwater flow has been reported consistently to the northwest at gradients ranging from 0 005 to 0 02 ft/ft i