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IU'UI-JU U4. 1 Uf1Yl PIlVIYI 1/1 JV VV1Y I JA1.1 V, 1V UJUU IUIJ • fUUJ/ VU4 Mr. Robert Chambers Page 2 The two-inch layer of asphalt-like material associated with the concrete floor of the reservoir was discovered in one of five trenchcw 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 han 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 t�e 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 significaIL amounts of toxic constituents into groundwater. Therefore, DTSC does not presently believe that Che oil contamination at the Sita is a threat to groundwater. Determination Pursuant to Health & Safety Code, Division 20, Chapter 6 . 5, Section 25221 . 1 (x) , 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 .