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present beneath the former location of the UST. There appears to have been lateral migration of contaminants at 15 feet below the surface. This migration is probably related to the higher clay content found in a the soil at that level . The level of soil contamination found at the Pacific Bell Stockton facility 7s significant and will require remediation. However, ground water does not appear to be involved at this time. Therefore, " remediation efforts should be implemented in a timely manner to ensure that the required remediation will be limited to soil contamination. 5.2 ReMedial Action Alternative s In view of TPH concentrations found in the soil analyses, remediation will be required. The clay-rich soil types present at the Pacific Bell Stockton facility would tend to preclude any insitu remediation without encountering significant technical problems. The most effective methods of remediation all involve excavation of the contaminated soil . Versar proposes to excavate all soil from the site which has a TPH r concentration of greater than 100 ppm. However, two factors must be allowed for in any excavation. First, the excavation pit would be immediately adjacent to the front of the Pacific Bell Stockton facility, a critical telephone switching station in the Central Valley. Second, in front of the facility is a major telephone transmission cable. Should excavating to the 100 ppm concentration in anyway threaten either, the facility or the cable, a lower excavation limit of 500 ppm should be employed near these features. This would still ensure the vast majority of the contamination would be removed and would remove any threat to ground water. Additional work to secure the septic system and to disconnect and later reconnect subsurface pipes would be required no matter what level of concentration is removed. The resulting excavation 14 1