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GROUND ZERO <br />ANALYSIS, INC. <br />1172 Kansas Avenue, Suite A <br />Modesto, CA 95351 <br />209.522.4119 — PH <br />209.522.4227 - FAX <br />groundzeroanaiysis.com <br />March 16, 2022 <br />Project No. 1086 <br />Project Name: Olivarez Property (Former Skips Service Station) <br />San Joaquin County <br />Department of Environmental Health <br />1868 E. Hazelton Avenue <br />Stockton, CA 95205 <br />Re: Work Plan: Cone Penetration Testing (CPT) Drilling <br />Location: North Side of E. Lafayette Street & Under the HWY 4 Overpass <br />(Refer to the attached Site Map) <br />Dear Permit Department, <br />Background <br />In 1992 six underground storage tanks (USTs) were removed from the site, including three <br />gasoline fuel USTs, two diesel fuel USTs and one waste oil UST. Soil samples were collected <br />from beneath the USTs and dispensing equipment indicated the presence of petroleum <br />hydrocarbons. An over -excavation of the USTs was completed, and the excavation was <br />backfilled in April 1996. A portion of the backfill material used was reported to contain <br />trace petroleum hydrocarbon contamination. The location of the five fuel USTs (north of <br />building) and one waste oil UST (east of building) are shown in Figure 2, Site Map. Refer to <br />Figure 1, Vicinity Map, for location of the site. All reports and correspondence noted in this <br />Work Plan can be viewed on GeoTracker, Global ID #T0607700605 <br />Numerous phases of investigation and remediation have been conducted including over eight <br />years of intermittent groundwater pump -and -treat. Remediation ceased in February 2016 after <br />Foothill Engineering could no longer financially carry the remediation system as stated in their <br />January 5, 2016 letter. Routine groundwater and remedial system monitoring have documented <br />very significant reductions in the concentrations of dissolved contaminants. A detailed <br />summary of the Site's history is provided in the Ground Zero Analysis, Inc. Third Quarter 2017 <br />Groundwater Monitoring & Path to Closure Report dated November 20, 2017. <br />The site appears to have the potential to meet the general and media -specific criteria of the <br />RWQCB LTCP. In the January 2018 and June 2018 letters, the RWQCB requested further <br />assessment of groundwater, soil vapor and soil investigations to determine if the Site is in <br />compliance with the LTCP criteria or to determine if further remediation is needed. Ground <br />Zero submitted the Path to Closure Impediment Discussion & Site Investigation Work Plan <br />