SITE INFORMATION AND CORRESPONDENCE

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AWAkffAM September 16, 1991 ARCO Service Station No. 2076, Lodi, California that hydrocarbons were not detected in the soil s pies submitted for analyses from borings B-2, 8-4 and B-5; benzene, toluene, ethylbenzene, and total xylene isomers (BTEX) concentrations ranging from 0.08 to 0.052 parts per million (ppm) were detected in sample from borings B-1 and B-3. During a vapor-extraction test conducted in July 1991, we evaluated whether vapor extraction is feasible at the site. Based on pressure data obtained during the vapor- extraction test and the distance between the wells, we concluded that extraction of 40 cubic feet per minute from a vapor-extraction well will produce an influence on an area with a radius of approximately 30 feet. Based upon the VET data, RESNA concludes that vapor extraction is a feasible method of remediating soil at this site. The radius of influence estimated above can be further refined and the remediation time frame can be initially estimated if additional subsurface environmental investigations are warranted. Additional details on the VET are discussed in our report in Appendix C. Tank Removal ARCO's contractors are presently securing the appropriate permits from the SJCPHS-EHD to remove the tanks. A date for the removal will be scheduled at ARCO's request by the contractor. During the tank removal a SJCPHS-EHD inspector, local fire department 1 representative, and a RESNA staff geologist will be present at the site. The contractor will first empty the tanks and dispose of the fluids in accordance with State and local regulations. The asphalt and concrete above the tanks and the product and vent lines will be removed. The contractor will triple-rinse each tank, remove the fluids, and purge the vapors. Triple rinsing is performed to clean the inside of the tanks to remove flammable material. Air is pumped through the tank to remove vapors from the tank. Each tank then will be filled with a non-reactive gas, usually nitrogen or carbon dioxide, to control the oxygen source to prevent fire or explosion; this is commonly achieved by placing dry ice in the tanks. Before the tanks are removed from the ground, the,contractor will analyze the atmosphere inside the tanks for concentrations of combustible vapors and oxygen content using a hand- held combustible gas indicator and oxygen meter. When combustible vapors and the oxygen are at the safe levels, as indicated by the meter, a representative of the local fire department will approve removal of the tanks. The ends of the product pipelines and vent lines will be sealed. The contractor will remove the tanks and product lines and place them on flatbed trailers for transport to an appropriate facility for disposal. 30x08-3w 1l