ARCHIVED REPORTS_SOIL AND GROUNDWATER INVESTIGATION WORK PLAN

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' Soil and Groundwater Investigation Work Plan Vernalis Offsite April 2007 ' Soil and Groundwater Investigation Report(SAIL, 2006a). In August of 2006, SAIC completed a site investigation and concluded the following: ' • Affected soil and groundwater are delineated vertically to a maximum depth of approximately 80 feet bgs. The RWQCB accepted these delineation results in a letter dated March 19, 2004. • In the immediate vicinity of the boiler house and the pump house, the lateral extent of affected ' soil was defined by several borings located near monitoring well MW-1. • In addition to a small area of affected groundwater at MW-1, two additional areas of affected t groundwater were present: one on the Arcos property,which encompasses Geomatrix borings ASB-1,ASB-4,ASB-5,ASB-6,ASB-7, and ASB-I 1; and one on the Bellini and Bogetti properties,which includes borings SB-15, SB-16, SB-18, SB-19, SB-20, SB-23 (MW-6), SB-24, SB-25, and monitoring well MW-7 (Figure 3). ' • Up gradient, the extent of affected groundwater is delineated at the following locations, from north to south: soil boring SB-30;monitoring wells MW-3 and MW-4; and soil borings ASB-2, ' ASB-3, and ASB-9. • The extent of affected groundwater is undefined at boring SB-25 and at monitoring well MW-7, and further off-site investigation is necessary down gradient on the Bogetti property. ' • The extent of affected groundwater on the Arcos property is undefined, and investigation is necessary down gradient on the San Joaquin Valley Hay Growers Association(SJVHGA) property, or in the Highway 33 ROW. ' To define the extent of affected groundwater down gradient on the Bogetti property, SAIC proposed the following: ' • Install seven borings(SB-26, SB-27, SB-28, SB-29, SB-31, SB-32, and SB-33) from which groundwater samples will be collected for laboratory analysis of the COCs (Figure 3). Because access to the SJVHGA property has been difficult to obtain, borings SB-31 through SB-33 should ' be located in the Highway 33 ROW. Based on a search of DWR files to identify water supply wells within a 'h-mile radius of the former Vernalis Pump Station, SAIC identified a total of four wells. One domestic well and two public wells ' were located adjacent to the pump station within the search radius. The Water Well Drillers Reports indicate the domestic well was constructed with a minimum sanitary seal of 50 feet bgs. The public wells were constructed with minimum sanitary seals of 150 feet bgs and 200 feet bgs,respectively. The fourth ' supply well is an irrigation well located up gradient of the area of concern. SAIC also identified six monitoring wells and one groundwater-extraction well located within the 1/2-mile search radius. These wells are located on the Western Farm Service property,which is diagonally ' opposite the Bellini property's northern tip at the intersection of Welty Road and Highway 33. None of these wells are located down gradient from the areas of affected groundwater. There is a water supply well known to be located on the Arcos portion of the pump station,which was not ' found during the search of DWR files. SAIC could not find any information about the well's construction, completion depth,age, or use. However,the well was sampled on October 29,2003,by Geomatrix. No TPHg, TPHd,PAHs, or volatile organic compounds were detected. ' Approximate locations of the water supply wells are shown on Figure 1. A summary of the water supply well search results is presented in Table 1. ' 3. SCOPE OF WORK SAIC will implement the recommendations of the SGIR, in accordance with the methods described in ' sections 3.1 through 3.5. In general, SAIC will advance up to seven borings from which soil and 4 From Science to Solutions