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Fuller Mobile Home Park 365 E Louise Ave-, Lathrop, California April 3, 1998 Vertical and Laterial Extent Confirmation Work Plan (Revised) Page: 2 from each boring through a stainless steel screen inside the augers. B-5 soil samples were ND (None Detected), but the groundwater sample had BTEX contamination. B-6 was ND for both soil and water. Monitoring well MW4 was installed in the sidewalk of Bizzibe Street in the apparent down-gradient direction. Laboratory soil samples were obtained at five, ten and twenty-five feet below ground level (Tables 1 & 2). On December 21, 1994, after receiving the analytical results from the previous borings, WIN drilled and installed three monitoring wells, MW-5, 6 and 7. Each was 25 feet deep and soil samples were taken at five and ten feet. All soil samples tested "ND" (Table 1). Monthly depth to water readings are being recorded and the groundwater gradient calculated for each month. The past gradients have been irregular, probably due to the fact that the gradient is extremely flat and the lithology is probably affecting stabilization of the minor fluctuations across the site. 3.0 Scope of Work WH proposes (5) shallow soil boring to a depth of 25.0' bgl and a single slant boring at a 30' angle to east to confirm the vertical and lateral extent of the soil contamination in the unauthorized release area surrounding the former UST Llocation. The event will also provide the data to evaluate contamination reduction as a result of natural attenuation (Figure 2). A single water sample will be collected from the slant boring by hydropunch method. Soil boring locations propose in this scope of work are identifies in Figure 3 of this work plan. 3.1 Dulling Permits will be obtained as necessary for all wells (including borings) before drilling begins. The soil boring wiII be accomplished using a mobile mounted drilling rig employing the use of a hollow stem flight auger no less than 3 114-inch i.d. and 8 7/8 o.d. All drilling equipment will be thoroughly cleaned before drilling begins, to prevent the introduction of contamination from off site, and between borings to prevent cross contamination. The borings will be logged under the direct supervision of a registered professional using the Unified Soil Classification System (Figure 4). The color, texture, moisture, plasticity (if applicable), consistency of the earth materials, pertinent soil or bedrock characteristics and any evidence of contamination will be noted. All water bearing zones and the depth at which they were encountered will be noted on these logs.