WORK PLANS - Laserfiche WebLink

Home Browse Search

o Ms. Lori Duncan f January 11, 2005 Page 2 of 7 Underground Storage Tank Removal The site previously utilized one 1,100-gallon UST for storage of unleaded gasoline (Figure 2). Jim Thorpe Oil, Inc. of Lodi, California removed the UST under permit from EHD and conducted ininor-sail-rx-eavation-oa-Febnmp/-�, 99. According to Mr. Rich Thorpe, less than 30 cubic yards of soil were excavated as part of the removal activities. The excavated soil was stockpiled on site adjacent to the excavation. Soil samples collected beneath the tank contained ethylbenzene and total xylenes at levels exceeding the respective laboratory detection limits. Analytical results of soil samples collected from beneath the former UST are summarized in Table 1. Sensitive Receptor Survey At the request of EHD, Ground Zero conducted a survey of production and/or domestic wells within 2000 feet of the site (Well Installation Workplan, August 10, 2000). As part of the survey, Ground Zero contacted the California Department of Water Resources (DWR), the City of Manteca, and EHD, and conducted a drive-by survey of the area. Fifteen wells were located near the site, including six wells within 2,000 feet of the site. In addition to the wells confirmed through well logs obtained from the listed agencies, nine residences were also located within 2,000 feet for which no documentation of any well was available from any agency. Ground Zero stated in the report that, although no well logs were available, each of these residences was likely to have their own domestic well. Pursuant to EHD's request for additional information, Mr. Marty Harris of Tuff Boy conducted additional survey to confirm that the residences identified by Ground Zero each have a domestic well for drinking water. The nearest water supply wells are the former facility well located approximately 220 feet northwest (downgradient) of the former UST and a neighboring domestic well located approximately 125 feet southeast (upgradient) of the former UST. The former facility well is no longer used by the facility, but is maintained as an emergency fire suppression well. The facility currently utilizes a newer well at the northern boundary of the property approximately 500 feet north of the former UST. All three of the wells mentioned above were sampled for gasoline constituents on September 26, 2003. No.gasoline constituents, including benzene or MTBE, were detected in these water supply wells. Subsurface Investigations Ground Zero supervised the drilling of three soil borings on December 17, 1999 to investigate the extent of soil and groundwater contamination in the vicinity of the former UST. Results of the investigation indicated that soil and groundwater had been impacted from an unauthorized release of gasoline. Residual soil contamination appeared to be limited vertically to a depth of less than 15 feet below ground surface (bgs), but monitoring wells were necessary to evaluate the extent of groundwater contamination. Soil and groundwater analytical results are summarized on Tables I and 2, respectively. G:IGROUNDZE1TuffBoy\Reports\W orkplansl W Pf 204.doc