ARCHIVED REPORTS_XR0007692 - Laserfiche WebLink

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GeoHydrologic Consultants, Inc • 10 INTRODUCTION On behalf of Thrifty Oil Co (Thrifty), GeoHydrologic Consultants, Inc (GHQ has ' prepared this report to fulfill the requirements of the San Joaquin County Environmental Health Department (SJCEHD), which required Thrifty to perform remedial action activities consisting of the abandonment/installation of groundwater wells and pilot ' testing using a mobile treatment unit for conducting two multi-phase extraction (MPE) events, and two groundwater pumping tests for Thrifty Station No 171 located at 1250 North Wilson Way, Stockton, California ("the Site", Figure 1) The proposed scope of work for these activities was recommended in the Workplan for Well Abandonment/Installation of Groundwater Wells and Pilot Testing prepared by Thrifty dated November 12, 2004, and approved by the SJCEHD in their letter to Thrifty dated December 7, 2004 The scope of work completed during this investigation included the abandonment of ' groundwater monitoring well MW-5 which was completed at the direction of the SJCEHD because of their concerns regarding the potential for this well to be screened across a shallow and deeper aquifer At the direction of the SJCEHD, vapor extraction well VE-5 was installed in the same borehole as MW-5 following drilling this well and backfilling the boring with bentonite chips as approved by the SJCEHD in order to ensure that the same capture zone was maintained for future vapor extraction activrttes from this well A workplan addendum for installation of VE-5 in the MW-5 borehole was required by the SJCEHD prior to commencement of this work and prepared by Thrifty on March 15, 2005 A shallow groundwater extraction well (EW-5S) and deeper groundwater extraction well (EW-5D) were completed to the east of existing well MW-5 in separate boreholes as required by the SJCEHD The newly installed groundwater extraction wells were developed by surging and bailing after installation along with the remaining eight onsite wells, since these existing wells had silted up significantly over the last few years ' 2.0 SITE DESCRIPTION The Site is owned by Thrifty and is currently leased and operated as a self-service gasoline sales facility by ARCO Products Company since May 1997 It is located on the southeast corner of Wilson Way and Harding Way in Stockton, California (Figure 1) The Site is generally square and about 12,300 square feet in size The Site features a ' cashier's booth, three product dispenser islands, and three double-walled fiberglass underground tanks (Figure 2) These tanks were installed in November 1994 and are located near the northeastern corner of the Site The newer tanks replaced five steel USTs that were located in the southwest portion of the Site There is an equipment enclosure located in the southeast corner of the Site which currently houses the thermal oxidizer being used at the Site to perform ongoing soil remediation through vapor extraction The ' Site has been operated as a service station for at least the last 30 years and there are no plans for alternate use TOC i71 Pilot study Page 1