ARCHIVED REPORTS XR0001566 - Laserfiche WebLink

Home Browse Search

r t • Mr Michael lnfurna Page 2 of 7 The UST's along with product dispensers and associated piping were removed under permit from San Joaquin County PHS/EHD on January 19, 1999 Analytical results of the soil samples collected from beneath the UST's and the former dispenser island indicated contamination by petroleum hydrocarbons Analytical results from the tank removal are summarized in Table 1 Sample locations are depicted on Figure 2 On April 19 and April 20, 1999, Ground Zero conducted a subsurface investigation in order to determine the lateral and vertical extent of contamination Two borings, SB 1 and SB2, were advanced to a depth of approximately 16 feet bgs in the area proposed for installation of new UST's in order to determine the suitability of the material for backfilling the excavation These borings were located west of the office building on the property(Figure 2) The remaining six soil borings, SB3 through SB8, were advanced to investigate the lateral and vertical extent of residual soul contamination, as well as the potential impact to groundwater Borings SB3 through SB8 were located around the perimeter of the UST excavation and in the area of the former lines and dispensers Soil and groundwater samples collected from borings SB3 and SB5-SB8 had non-detectable levels for the target analytes However, boring SB4/SB4A had elevated petroleum hydrocarbon concentrations in soil at a depth of 15 feet Soil at a depth of 20 feet did not contain detectable concentrations Petroleum hydrocarbons were also detected in the groundwater sample collected from this boring The data obtained from this investigation indicated that the vertical extent of contamination did not exceed 20 feet below ground surface (bgs) and defined the lateral extent of soil contamination The contaminants consisted primarily of diesel hydrocarbons and methyl tert butyl ether (MTBE) Soil results are summanzed in Table 1 Groundwater results are summarized in Table 2 Sample locations are depicted on Figure 2 Based on the results of this investigation, source removal excavation was proposed in the Corrective Action Workplan dated June 2, 1999 Contaminated soul excavation and confirmation sampling occurred in two stages—the first on June 16 and the second on June 30, 1999 The additional excavation was conducted in order to remove a small volume of contaminated soil remaining after the first stage of work On June 16, 1999, approximately 200 cubic yards of contaminated soil and 20 yards of overburden was excavated by Johnson Petroleum within the vicinity of the existing tank pit The area excavated was irregular in shape and vaned in depth Seven confirmation soil samples were collected from the excavation walls Analytical results from these samples indicated that a small volume of contaminated soil remained Groundwater samples were also collected from within the excavation Analytical results indicated that the groundwater was impacted by petroleum hydrocarbons t� Woolseychaaer\reporWsummary doc