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PROBLEM ASSESSMENT REPORT GROUNDWATER INVESTIGATION GRANTLINE PLAZA TRACY, CALIFORNIA 1.0 INTRODUCTION i This report .presents the methodology and results of a groundwater investigation conducted by ROY F. WESTON, INC. (WESTON)`at the property known as Grantline Plaza, located at 350 West Grantline Road, Tracy, California (Figure 1). This investiga- tion was conducted at the request of the San Joaqu County Public Health Services, Environmental Health'Division (EHD). The Tri-Regional Guidelines (Appendix A) Problem Assessment Report (PAR) format has been utilized in the preparation of this report. 1.1 Site Background The subject property is located in a commercial development and consists of a 6000 square foot building and an associated lot. A 2000 gallon underground gasoline (leaded and unleaded) storage tank (UST) was removed from the south side of the building in September ;1986. Analysis of a water sample taken by Canonie Environmental from the j tank excavation indicated BTXE and TPH were present in the.water. The results of that E water analysis are as follows: Benzene Not detected, detection limit 0.01 mg1L Toluene 0.36 mglL 3 &U P w Xylene 0.14 mglL i "0 pvh Total hydrocarbons 310 mglL 310,pp°eV Ethylenedibromide Not detected, detection limit 0.0005 mglL Lead (Total) 1.13 mglL i,l . p The complete laboratory report is presented in Appendix B. As groundwater is very shallow on the site,water was presentin the excavation pit during the tank removal. ,.The property owners contend that the tank was ruptured by the backhoe during tank removal activities and that a small quantity of tank rinse.water containing " asoline'iesidue spilled into the water in the excavation pit. Inventory records kept by the property owners show no evidence of gasoline inventory loss during the life of the tank, The excavation was backfilled with clean fill. x `i # I