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j t Five exploratory borings were drilled at the site (Figure 1) on March 17, 2000. The borings revealed degraded petroleum hydrocarbon contaminants in the vicinity of the former tank pits and in groundwater just north of the pits A groundwater gradient could not be calculated from uncased borehole water levels; however, the distribution of contaminants suggests a northerly movement. A sample from the water well at the. property boundary showed Total Petroleum Hydrocarbons as Diesel at very low concentrations; these petroleum contaminants were deleted in volatile components and some did not match the gasoline or diesel laboratory standards. Proposed Scope of Work ;j f . The previous borings revealed petroleum hydrocarbons�jdepleted in volatile content in both groundwater and the water well. The soil plume appears to have been defined by the initial work. The source of the groundwater contaminants appears to be from the former tank pits, given their proximity to the tank pits on the east side of the building. Additional exploratory borings are proposed to delineate the extent of this degraded I dissolved contaminant plume (see Figure 1). The water well contaminants were quantified as very low concentrations of a degraded diesel, which did not match the laboratory diesel standard. The well log shows that this well has a sanitary seal, which crosses clay strata. It does not seem likely that light non- aqueous phase contaminants would sink or be pulled into this water well from pumping. However, it is possible that the water well may have a self-oiling pump the oil reservoir of which may have a leak causing this problem. The water well will be resample to check the results of the first sampling. One exploratory boring his proposed adjacent to the well to ascertain whether contaminants are in near proximity to the well in the shallow aquifer. This boring will attempt a vertical sample profile of soil and groundwater in the upper strata above the clay strata into which the well is sealed. Wright will also perform a regulatory file search of possible nearby sources of 'contaminants, which could be contributing sources. f The goals of this workplan are to: Y • Ascertain the vertical and horizontal extent of the contaminant plume in groundwater, continuing the initial site assessment for this site. This data, together with the previous data will be used to locate positions for groundwater monitoring wells. I • Install groundwater monitoring wells for long term dissolved plu ring as G initially discussed (as Phase 2) in the original work plan date ecember 9, 1999. il• Initiate quarterly groundwater monitoring for the site, • Resample the Calaveras well to check the initial May 10, 2000 sample results. f E M&Yl Builders Supply 2 10/16/2000 I Wright Project No.4669