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r Petroleum Hydrocarbon Soil Stockpile Background The LNC site had a former 10,000 gallon concrete UST that was a bulk oil storage structure used by the former winery (Shewin-Williams Winery)during the 1910 to 1950 time period. This tank was reportedly used by the winery to store heating oil for burners located in the attached building. The tank was used in this capacity after about 1940. The tank was built as part of the brick building structure and as such, formed an integral part of the building. Because the tank was an underground storage tank it was registered with the local San Joaquin County Underground Storage Tank program in the 1980's. LNC never used the tank for heating oil storage and decided to close the tank in place under regulatory agency oversight. The tank was removed under the regulatory agency oversight of San Joaquin County Public Health System Environmental Health Division(PHSEHD). In 1993, a workplan prepared by WZI Inc., Bakersfield, California(WZI)was submitted to and approved by PHSEHD for the soil sampling and abandonment of the former concrete tank (WZI, 1993). The WZI proposed scope of work included: (1) the destruction of the concrete tank roof; (2) excavation of petroleum hydrocarbon impacted soil adjacent to the tank to a depth of about 22 feet below ground surface; (3)backfill of the interior of the tank and external sidewalls with clean backfill material (pea gravel) and; (4) capping the former tank roof with a cement and asphalt surface. In addition, soil borings were advanced through the center part of the former tank and three of the four sides of the former tank to determine the depth and horizontal extent of petroleum hydrocarbons in the subsurface soils. This scope of work was conducted during 1993. During the field work, approximately 25 cubic yards of petroleum hydrocarbon impacted soil were excavated and placed on Visquene at a remediation stockpile on the LNC site(Figure 2). This stockpile was covered to prevent potential unauthorized aeration in accordance with San Joaquin Unified Air Pollution Control District(APCD)requirements. During 1993,the soil stockpile was sampled using U.S. Environmental Protection Agency (USEPA) Test Method 846-SW procedures and multiple samples were submitted to an analytical laboratory to determine if they contained any volatile organic compounds (VOC's) (WZI, 1993). The soil samples were all reported as not containing any VOC s above analytical method detection limits. However, the same soil samples were reported to contain Total Petroleum Hydrocarbon compounds as motor oil (TPH-mo) and diesel fuel (TPH-d) ranging from 1, 000 to 10,000 mg/kg (WZI, 1993). The presence of these heavy fraction petroleum hydrocarbon compounds is consistent with the prior use history of the former UST as a bulk fuel storage tank. During 1993 and 1994, the soil stockpile was landfarmed by LNC personnel in accordance with the PHSEHD approved workplan. This effort included tilling the soil and keeping the stockpile moist. Soil samples were not collected to determine the effectiveness of the landfarming activity. After mid-1995 this landfarming was discontinued. D:\EnvironmentaI\LCN\LCN103.wpd 2