ARCHIVED REPORTS_XR0012660 - Laserfiche WebLink

Home Browse Search

Lf E09HILLfIfAIIENi{OFF,ING. II. PROPOSED WORKPLAN SOIL INVESTIGATION Soil Boring and Sampling Soil samples will be collected from four 6-inch diameter hollow-stem augered boreholes in order to verify the vertical and lateral presence or absence of petroleum hydrocarbon residuals in the soil. Three of these borings will be located to investigate the main former underground tank located near the center of the site (see Figure 1). Balbi and Chang's soil boring TB-1 showed detectable levels of gasoline hydrocarbons in a soil sample collected from a depth of 2 feet and the log for TB-1 noted gasoline odors at depths of 3 and 6 feet, Soil samples collected from depths of lO and 15 feet showed no detectable BTX&E and TPH as gasoline or diesel. Wier samples collected by Balbi & Chang and confirmation samples recently collected by LH show high concentrations of BTX&E and TPH (as gasoline) from MW-2, which is adjacent to this former tank site (see Table l). Ealbi and Chang drilled boring TB-1 with the intention of boring directly through the former tank excavation. However, the only information available regarding the location of the four former tanks is a map attached to the permit application filed with Stockton City Hall in 1978, for the removal of these four tanks. Two large tanks were located in the center of the site, and two smaller tanks were located at the southern end of the site. On the site map included with this permit, it is unclear whether the measurements to the tanks are taken from the curb line or the property line, and when Balbi and Chang drilled TB-1, they presumably measured from the curb line. After Balbi and Chang released their report, action was taken by Roek Brothers to excavate the former tank area and aerate the soil. The site was investigated by LH in July I989 and examination of the northerly excavation walls showed the material to be native, not disturbed fill. However, examination of the southerly walls of the excavation did show fill material. Fherefnre, it appears that the measurements to the tanks should have been taken from the property lines, and that TB-I is actually located outside of the former tank excavation.