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� Nnow, <br /> r <br /> WORK PLAN <br /> r <br /> UNDERGROUND STORAGE TANK INVESTIGATION <br /> Sprint Communications Company <br /> Stockton Switch Facility <br /> 3807 Coronado Avenue <br /> Stockton, California <br /> r <br /> 1.0 INTRODUCTION <br /> This work plan presents the proposed underground storage tank (UST) investigation to be conducted <br /> by Riedel Environmental Services, Inc. (RES) at the Sprint Communication Company's Stockton <br /> Switch Facility located at 3807 Coronado Avenue in Stockton, California. The purpose of the <br /> investigation is to determine whether soils surrounding the abandoned 6,000-gallon diesel UST pit <br /> have been impacted by diesel fuel. <br /> r <br /> 1.1 Site Conditions <br /> The subject site is an active communications switching facility. In August/September 1994, a new <br /> 10,000-gallon UST was installed adjacent to the previously existing 6,000-gallon UST to replace the <br /> facility's emergency generator fuel supply. The 6,000-gallon UST was removed, but the tank tie- <br /> down structure was left in place. The tie-down system was not observed, but is likely to include a <br /> concrete slab at the bottom of the UST pit at a depth of approximately 10 feet below grade. At the <br /> completion of the UST installation and removal activities, the old UST pit was backfilled with the <br /> excavated materials. A diagram of the site is provided as Figure 1. <br /> A water well currently exists at the site. The depth to ground water at the site is approximately 45 <br /> feet below grade. <br /> 1.2 Site Background <br /> On 7 September 1994, stockpile samples SPE and SPW were obtained from the stockpiled backfill <br /> material removed from the 6,000-gallon diesel UST pit. The results of the analytical testing <br /> indicated that soil sample SPE contained 17 parts per million (ppm) total petroleum hydrocarbons <br /> as diesel (TPHd) and soil sample SPW contained 230 ppm TPHd, 0.016 ppm ethylbenzene, and <br /> 0.047 ppm xylenes. <br /> Samples of the native soils at the bottom of the UST pit could not be obtained at the time of the tank <br /> removal due to caving of the backfill gravel surrounding the newly installed 10,000-gallon UST. <br /> The abandoned UST pit was immediately backfilled with the excavated gravel material to avoid <br /> damage to the adjacent 10,000-gallon UST. <br /> r <br /> 4185\CBW I\SPRINT.WPVISEP% 1 <br />