SITE INFORMATION AND CORRESPONDENCE

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■ MEMO TO: Diane Hinson, Supervising REHS October 20, 1995 FROM: Steve Sasson, REHS RE: 510 E Magnolia Stockton Developmental Center In February of 1995, a preliminary investigation was conducted, to determine the extent of petroleum hydrocarbon contamination discovered during closure of underground storage tank 3 (UST), at the Stockton Developmental Center. Bunker fuel #6 was stored in the UST to provide fuel for the boiler at the Developmental Center. The tank is located within 8 feet of a water tower which provides pressure for the water system at the Develomental Center. Contamination from the UST is present above cleanup levels, but cleanup is not proceeding due to the presence of the tower. A budget change proposal of $90,000 for the cleanup has been submitted to the state legislature, and the status of the request will be finalized in March for the fiscal 1996-1997 budget year. Cleanup will begin when the funds become available July 1, 1996. The result of the investigation is that diesel and bunker fuel are present at a depth of 15 feet below ground surface. Diesel fuel contamination is present at 830 ppm, 5400 ppm and 6500 ppm in the three sample locations obtained from borings advanced around the eastern half of the tank at a depth of 15 feet. Bunker fuel contamination is present at 5600 ppm, 9600 ppm and 5400 ppm in the same three samples. The 20 foot samples in these three borings had non detectable concentrations of diesel and bunker fuel. Four additional borings, advanced at a slightly greater distance from the tank than the three initial borings, had no detectable contamination in any sample from ground surface to 20 feet below ground surface. Based on a historical high depth to groundwater of 35 feet, in this area of Stockton, the level of contamination is too great to leave in place. The maximum allowable level to leave in place is 1000 ppm for both diesel and bunker fuel. There are tests that can be performed, which may indicate that the maximum allowable level can be increased, and still provide adequate groundwater protection. Groundwater in this area of Stockton is currently approximately 70 feet below ground surface. The planned activities for the site are stated in a written correspondence dated May 31, 1995, written by Mike Bean, the Chief of Plan Operations at the center, and were repeated during an October 18, 1995 telephone conversation, with Mike Golden, at the Division of the State Architect. The state will over excavate the area, and remove the UST when the water tower is removed, because over excavation near the water tower may compromise the structural integrity of the tower. During my conversation with Mike Golden, he indicated that if the site is not a water quality problem, they would like to leave the contamination in place for 2 or 3 years, until the tower comes down. He also stated that when the property is turned over to the county, it will be minus the water tower, UST and contaminated soil. The turn over to the county will be phased in over 3 to 5 years. We discussed in situ remediation as an option for cleanup with the tower in place, but he indicated that bunker fuel is not readily treatable using current in situ remediation technology.