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Revised Work Plan For Soil and Groundwater Assessment 6 Ranch Market 23569 South Santa Fe Road Riverbank California April 25,2000 SITE ASSESSMENT Referring to Figure 2 and Table 4, SECOR recommends drilling a total of nine soil borings in two phases of work presented below: Phase 1-Initial Soil Boring and Groundwater Investigation Deep Continuous Core Borings Continuous core two soil borings, SB-1 and SB-2, to depths of 140 feet bgs. The actual depth of the two soil borings will match the depth of well DW-2 that will be determined in a proposed down-hole video log. The lithologic description, soil sample data, and depth discrete water samples collected from the two borings will be used to define the vertical distribution of hydrocarbons adsorbed to soil and dissolved in groundwater. Direct Push Soil Borings Drive three dual cased direct push points, GP-1 through GP-3, to depths of 45 feet bgs. The soil data will be used define the lateral limits of impacted soil to the west, east, and north of the former tank pit. Phase 2- Follow-up Well Installation Investigation Drill and install one depth discrete groundwater monitoring well,MW-5D, to a depth of 80 feet bgs. Quarterly water samples collected from the well will allow detection of any changes in the vertical migration of dissolved petroleum hydrocarbons. The depth discrete completion from 80 to 85 feet bgs will also allow measure of any vertical gradient that may exist underlying the Site. Drill and install four groundwater monitoring wells, MW-6, MW-7, MW-8 and MW-9 to depth of 40 feet bgs. The wells will be used to define the lateral limits of the dissolved hydrocarbon plume up-gradient, cross-gradient, and down-gradient of the former UST pit. The initial Phase 1 investigation will be completed prior to starting the Phase 2 portion of the assessment. The results of the Phase 1 investigation may result in a change in the proposed Fle:RB-GmPmb wAml.WKP