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{ Quik Stop Station No. A. + April 22,2003 <br /> Stockton, California Work Plan for Additional Groundwater Investigation <br /> 3) were advanced to depths of approximately 65 feet bsg at the locations shown on Figure 2 to <br /> collect soil and groundwater samples. Groundwater was encountered in the borings at <br /> approximately 64 feet bsg and sampled with a hydropunch tool. Tabulated analytical results <br /> of soil and hydropunch groundwater samples are contained in Appendix B. No TPHg, BTEX <br /> or oxygenate compounds were reported in the soil samples collected from the three soil <br /> �'L vm5]a�d3 <br /> borings. Concentrations of TPHg ranging from fry to 66 micrograms per liter (parts per <br /> billion or ppb), ethylbenzene ranging from 5.0 to 20 ppb and total xylenes ranging from 29 to <br /> 110 ppb were reported in the three groundwater samples. A concentration of 0.63 ppb MTBE <br /> was reported in the SB-1 groundwater sample. On the basis of these investigation results, the <br /> SJCEHD requested the installation of monitoring w-Ills. <br /> i <br /> PROPOSED GROUNDWATER INVESTIGATION <br /> The purpose of the additional groundwater investigation is to evaluate the down-gradient, <br /> 3 <br /> lateral extent of petroleum hydrocarbons reported in groundwater samples collected from soil <br /> borings located adjacent to the former UST basin. It is also proposed to conduct a sensitive <br /> receptor survey of the area within 2000 feet of the site. <br /> The one monitoring well is proposed to be installed approximately 10 feet southeast (down <br /> gradient) of soil boring SB-2 to confirm the analytical results of the groundwater samples <br /> collected from soil borings SB-1 through SB-3. The proposed location is immediately down <br /> gradient of the location of the groundwater sample containing the highest reported TPHg <br /> concentration (soil boring SB-2). <br /> 1 <br /> The proposed work shall include field planning and scheduling, advancement of one soil <br /> boring, soil sampling, conversion of the soil boring into a groundwater monitoring well, well <br /> development and collection of a groundwater sample, performance of a sensitive receptor <br />� survey, and preparation of a report documenting the fieldwork and analytical results. All <br /> fieldwork shall be conducted in accordance with Horizon Field Methods and Procedures <br /> contained in Appendix C. The tasks are described in detail below. <br /> 7076%Yp4-03.doc <br /> Project No.7076.14 3 HORIZON ENVIRONMENTAL INC. <br />