SITE INFORMATION AND CORRESPONDENCE

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V %MOP consisted of very decomposed organic material that had clearly been present in the storm drain system for some time. It is likely that the small concentration of Toluene present in the water in the vault was related to the Toluene in the sediment sample that pre-dated the unauthorized release on February 25, 2003. MTBE was detected in the water sample collected from the gutter drain on the northern margin of Roselawn Avenue closest to the origin of the release in a concentration of 0.65 ug/L. The lower laboratory detection limit for MTBE was 0.5 ug/L. Remediation of the Unauthorized Release Kiff'Laboratories could not provide results from the four storm drain samples until 5:00 PM on Monday, March 3, 2003. Weather reports indicated a possible storm event beginning on Monday evening. WEGE therefore decided to remediate the storm drain system before the pumps in the vault could be activated by the predicted storm. On March 3, 2003, WEGE used a gasoline powered centrifugal pump to extract a total of 2400 gallons of wastewater from the main vault at the southern end of Buena Vista, the small vaults located beneath each gutter drain on Roselawn Avenue, and two larger vaults located in the centerline of Buena Vista Avenue. The water was pumped into 55 gallon drums and then transferred by pump into the Baker tank located at 1876 Country Club BIvd. WEGE also pumped 100 gallons of clean water into the drain system to help wash out any residual contamination. Revision of Pumping Procedures Following Unauthorized Release and Remediation WEGE was unable to determine the precise reason for the failure of the pumping system that led to the overtopping of the Baker tank. WEGE therefore instituted a new set of operating procedures for the project which required the presence of onsite personnel during any pumping activity from the open excavation to the Baker tank. As of March 10, 2003 the excavation has been backfilled and the Baker tank is no longer receiving wastewater. The waste water that was recovered from the storm drain system has been pumped from the Baker tank through carbon canisters and into the sanitary sewer system. The Baker tank will be removed from the site within the next week. If you have any questions about the information contained in this report please contact David Threlfall or George Converse at 530--668-5300. Sincerely, David Threlfall Western Geo-Engineers CC: Mr. Steven Shih, SJCEHD; Mr. Michael Infurna, SJCEHD; Mr. Clyde James, Reclamation District#1614 4