SITE INFORMATION AND CORRESPONDENCE

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1 • • a • • Mr. Robert Chambers June 20 , 1996 Page 2 The two-inch layer of asphalt-like material associated with the concrete floor of the reservoir was discovered in one of five trenches excavated to collect soil samples in 1991 . In 1992 , DTSC' s evaluation of the carcinogenic risk from this material indicated that an unacceptable risk existed. Upon re-evaluation utilizing revised risk assessment criteria, DTSC staff have concluded that the PAH levels in the asphalt-like material represent a potential risk greater than 1 x 10-6 . However, the potential risk is still within an acceptable range that would allow unrestricted land use. In addition, DTSC has concluded that the material is in a limited area and the potential for exposure is unlikely. Having assessed the risk from PAH contamination at the Site, the only remaining concern was the oil contamination. Oil was discovered at a depth of approximately 16 feet during the construction of a drainage way for the extension of Schulte Road and at a depth of 12 . 5 to 15 feet during the construction of a downgradient groundwater monitoring well . In a March 26, 1992 letter to you, DTSC expressed a concern regarding potential groundwater contamination due to the oil . Data from the four monitoring wells installed to assess whether the Site has impacted groundwater have not detected PAHs or total petroleum hydrocarbons . In addition, it has been DTSC' s experience at other sites that "Bunker C" oil after having been exposed to the environment for a number of years does not release significant amounts of toxic constituents into groundwater. Therefore, DTSC does not presently believe that the oil contamination at the Site is a threat to groundwater. Determination Pursuant to Health & Safety Code, Division 20 , Chapter 6 . 5 , Section 25221 . 1 (a) , DTSC issues the statement that, based on existing documents and other information presently available to DTSC, there is no currently known hazard at the Site .