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Mr. M. Scott Mansholt—ChevronTexaco January 13,2005 Soil and Groundwater Investigation Report—Pombo Property Page 3 of 8 WELL SEARCH In April 2004, SAIC conducted a search of California Department of Water Resources(DWR) files to review well driller logs for domestic, irrigation, or municipal water supply wells within 2,000 feet of the Pombo Property. The tabulated well search results of DWR files are presented in Table 3. Approximate locations of water supply wells identified during the DWR well search are shown on Figure 5. The well search covered portions of Township 2-South, Range 5-East, sections 19, 20,29, and 30. SAIC reviewed water well driller's reports for each section to determine if water supply wells were constructed within the 2,.000-foot search area. SAIC located nine water supply wells within the search area. Six wells (Map IDs 1, 3, 5-7 and 9)were listed as domestic supply wells,one well (Map ID 4)was listed as an industrial supply well and two wells(Map IDs 2 and 8)are listed as unknown well types. It is inferred that groundwater flows to the north. Four of the wells(Map IDs 6-9) are located between 400 to 2,000 feet up gradient of the Pombo Property. Four of the wells(Map IDs 1-3 and 5)are located cross gradient to the Pombo Property. One well(Map ID 4) is located down gradient of the Pombo Property and is an industrial supply well where the actual location is not specified. One well (Map ID 6) has a listed sea] depth of 12 feet bgs and three wells(Map IDs 4,8 and 9)have unspecified seal depths. All other well seals are at depths greater than 50 feet bgs. The down gradient industrial supply well (Map ID 4) is the only well with an unspecified screen interval. All other wells have recorded screened intervals greater than 43 feet bgs. SOIL AND GROUNDWATER INVESTIGATION To evaluate the extent of residual petroleum affecting either soil or groundwater adjacent to the areas identified in the Work Plan,SAIC supervised the installation of I 1 soil borings(SB-1 through SB-11)to the north of the Pombo Property on November 5,2003 and February 25, 2004. Soil boring locations advanced during the current and previous investigations are presented on Figure 2. A SAIC field �w,.. geologist observed Gregg Drilling and Testing, Inc.,of Martinez,California(C57#485165) advance soil borings to depths ranging from 12 to 16 feet bgs using direct-push technology. Prior to advancing the soil f' borings, each boring was cleared by hand auger to a minimum depth of 5 feet bgs. Soil borings were continuously cored from 5 feet bgs to the total depth explored using a 4-foot MaeroCore©sample barrel lined with clear poly-acrylic liners. The MaeroCore®barrel was advanced into undisturbed soil and, upon retrieval;the poly-acrylic liner was removed from the MaeroCore©barrel for logging and sample collection. Soil cores were inspected and logged using the Unified Soil Classification System(USCS). Soils were screened in the field for the presence of organic vapors using a photo-ionization detector (PID); organic vapor headspace readings were recorded on field boring logs. Soil samples were collected for laboratory analyses by cutting the poly-acrylic liner at target intervals and sealing the ends with TeflonTM sheets and plastic end caps. The samples were immediately labeled,placed in a plastic bag, and placed in an ice-cooled chest for delivery to Lancaster Laboratories, Inc., a California State-certified laboratory,under SAIC chain-of-custody protocol. Grab groundwater samples were collected on November 5, 2003 and February 25,2004 using a .75-inch diameter stainless steel bailer and decanted into laboratory-provided bottles. The bottles were labeled, sealed,and placed immediately into an ice-cooled chest for delivery to Friedman&Bruya, Inc., of Seattle, Washington, a California State-certified laboratory(ELAP#1727)under SAIC chain-of-custody protocol. Soil borings were advanced to depths ranging from 12 to 16 feet bgs. Subsurface soils observed during drilling indicate an upper unit of yellowish-brown silts and clays,underlying engineered fill and improved surfaces,extending to depths ranging from approximately 7 to 11 feet bgs. The upper unit is typically underlain by a lower water-bearing unit composed of silty and clayey sands to the maximum depth explored, which may finger in and out locally as lenses. The depth to first-encountered groundwater was ++