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CLEARWATER G. R O U P, I q C. Y• 1.0 INTRODUCTI N This report presents the results of fourth quarter 1995 groundwater. monitoring performed by Clearwater Group, Inc. (Clearwater) on December 21, 1995 at 1210 Vera Avenue in Ripon, California (Figure 1). The tasKS performed during this phase of work included groundwater gauging, well PILrging, and groundwater sample collection. 2.0; BACKGROU D The project site is located on the southerly outskirts of Ippon in an agricultural and residential area. The Stanislaus River meanc ers in a southwesterly direction approximately 2,000 feet south of`the site (Figure 1). Municipal water treatment ponds are located approximately 1,000 feet south and east of the site. Two 10,000 gallon underground storage tanks (UST's) were removed from the h subject location.on May 23 1990. The site cu rre tly has at least one above ground fuel tank. The site layout, including former UST locations, is presented in Figure 2. A review of available tank removal documents .indicated that the tanks were used to store regular gasoline and diesel fuel. Soil samples collected from beneath the UST's during removal did not contain total pe roleum hydrocarbons as gasoline (TPHg), kerosene, or motor oil, benzene, tolue e, ethylbenzene, and total xylenes (BTEX) or tetra-ethyl lead above respective method detection limits. One soil sample contained total petroleum hydrocarbons as diesel (TPHd) at a concentration of 9,800 parts per million (ppm). Three 2-inch-diameter monitoring wells were in talled by Clearwater on February 23, 1995. No petroleum hydrocarbons were detected in soil samples collected during soil borehole drilling, however, all three groundwater samples collected from the monitoring wells on February 28, 1995 contained TPHd in concentrations up to 330 . parts per billion (ppb). D-104 4Q95 1 January 26, 1996