SITE INFORMATION AND CORRESPONDENCE

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Mr. Jackson Chih Page 2 December 28, 1990 8 . Locate and abandon monitoring wells A, B, C and D in accordance with all applicable State regulations and/or local requirements. Initially a baseline risk assessment was completed as part of the PEA to determine health protective level for residential land use. The Department views the proposed clean up level of 20, 000 parts per million (ppm) total Petroleum Hydrocarbon (TPH) , as non-health protective. Preliminary evaluation by Department Staff Toxicologist indicates that a clean up level of 800 ppm TPH would be health protective. This is based on the very limited data presented and therefore very conservative. In spite of this apparent difference, the Department concurs with your final remediation since contaminated soils will be removed from all habitable areas thereby eliminating any potential health risks associated with exposure through direct contact or ingestion. With reference to arsenic and petroleum materials detected in shallow ground water, the RWQCB, Central Valley Region has been made aware of these conditions. The Department cautions that additional contamination may be present at the site in areas which have not been thoroughly characterized, since sampling conducted to date has been directed towards characterizing known areas of contamination. Because of historic uses of this site and other nearby sites, it is possible that additional contamination sources may be buried at the site. If such areas are discovered, recommendations within the PEA may no longer be appropriate and further investigation could be required. In concurring with the above recommendations, the Department reserves the right to require further action at the site should information other than that presented in the PEA report become available. If you have any questions please contact Claudia Johansen at (916) 855-7865 . Sincerely, 1 "X' J4_� Anthony J. Landis, P.E. Chief, Site Mitigation Branch cc: See next page.