ARCHIVED REPORTS_XR0004025 - Laserfiche WebLink

Home Browse Search

Ms Margaret Lagono April 6, 2001 Page 2 ProjectNo 2002-1426-01 concentrations of 18,000 parts per billion (ppb) and 220 ppb, respectively Benzene was detected in the samples collected from wells MW-1 and MW-2 at concentrations of 4,400 and 33 ppb, respectively In the vicinity of the site are a former ARCO Service Station, a Chevron Service Station, a Texaco Service Station, The Transmission Shop, and a former Colombo Bakery, all of which have or previously had USTs Based on data collected from subsurface investigations performed at the former ARCO Service Station, the Chevron Station, The Transmission Shop, and the Texaco Service Station, residual and dissolved hydrocarbons have been detected beneath these facilities and a commingled plume exists beneath Charter Way and Lincoln Street It is our understanding that the groundwater flow direction near the intersection has generally been towards the east and northeast The extent of the groundwater plume has not been established, but reportedly extends down gradient as far as Van Buren Street A work plan to further evaluate the vertical extent of hydrocarbon impact was submitted to San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) on January 28, 2000 The scope of work included using a cone penetrometer • tool (CPT) to continuously log the soil profile to 120 feet bgs followed by depth discreet soil and groundwater sampling Stratus retained Gregg Drilling and Testing, Inc and the work was completed on May 30, 2000 Results of the investigation were presented in a findings report dated October 27, 2000 GROUNDWATER MONITORING On March 8, 2001 a representative from Stratus measured depth to groundwater and collected groundwater samples from the two onsite monitoring wells The locations of the groundwater monitoring wells are presented in Figure 2 Groundwater Elevation First quarter 2001 groundwater levels were measured on March 8, 2001 using an electronic sounding device and recorded on the data form presented in Appendix A Table 1 presents the historical and first quarter 2001 groundwater elevation data At the time of the first quarter monitoring event, groundwater was encountered in monitoring wells MW-1 and MW-2 at 19 39 and 19 41 feet bgs, respectively Sampling, Analysis, and Monitoring Program Results Groundwater samples were collected from monitoring wells MW-1 and MW-2 on March 8, 2001 Groundwater sampling procedures are presented in Appendix B Samples were forwarded to Alpha Analytical Laboratory for chemical analysis with appropriate chain-of-custody documentation C Troject Filesll B Clstockton\Qrtlyhbc-stockton-1Q01 doc 5TRAru5