ARCHIVED REPORTS_XR0002045 - Laserfiche WebLink

Home Browse Search

Beacon Station No 641 .lune 15 2000 Stockton California Results of Additional Subsurface Iinesti ation SITE DESCRIPTION AND BACKGROUND • Beacon Station No 641 is an operating service station located on the southwest corner of the intersection of East Hammer Lane and Kathleen Drive in Stockton, California (Figure 2) The site is located in a predominantly commercial area of Stockton Site facilities include a service station/convenience store building, two canopy-covered product dispenser islands situated west and east of the store building, and three underground storage tanks (USTs) located in the west central portion of the property In rune 1996, four single-walled steel, 10,000-gallon gasoline USTs (T-1 through T-4) and associated product lines were excavated and removed from the site Horizon performed soil sampling associated with the removal of the UST systems The common UST basin was over-excavated to approximately 19 feet below surface grade (bsg) beneath UST T-1 and the west half of UST T-2 Additional over-excavation could not be performed because of the proximity to the sidewalk and street Analytical results of soil samples indicated concentrations of total petroleum hydrocarbons as gasoline (TPHg) up to 6800 milligrams per kilogram (parts per million or ppm) and benzene up to 80 ppm in soil at depths of 14 to 19 feet beneath former USTs T-1 and T-2 In June 1996, one 12,000-gallon and two 10,000-gallon double-walled, fiberglass-clad, steel USTs were installed in the former UST basin Ten 18-inch diameter conductor casings were placed in the former UST basin prior to backfilling The conductor casings were installed to facilitate future assessment and confirmation drilling through the backfilled UST basin (Tank Closure Letter Report, Horizon, August 2, 1996) Subsurface investigations have been performed since the replacement of the USTs In July 1996, Horizon drilled soil bonngs B-1 and B-2 Groundwater was encountered at depths of approximately 64 feet bsg in the soil borings Soil boring B1 was converted to a dual- completion soil vapor extraction well (VW-3 and VW4) Soil boring 132 was converted to a 641AddSbsrfcIvest5-00 doc 2 HORIZON ENVIRONMENTAL INC. 1641 14