SITE INFORMATION AND CORRESPONDENCE

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-s- To reach the liquid oil from inside the park the venting wells will need to reach 70 ft laterally. To reach this far the vacuum will likely be greater than our previous experiences due to the soil type at Tracy. The vacuum requirements and the amount of air pulled into the soil can be determined with a pilot test. The test will also confirm the hydrocarbon concentration in the vent gas for air permits. Laboratory Testing for Biodegradability To confirm the oil was indeed biodegradable, we mixed liquid oil sampled from observation wells at the site with soil from Tracy and put them in flasks with air flowing through them. The carbon dioxide (CO2) measurements were made over a period of 12 weeks and are used in Figure 3 to show the amount of oil biodegraded with time. The CO2 evolved at a fairly constant rate, indicating the oil was biodegradable. We will continue to monitor the bio- degradation rate and watch longer-term trends . Liquid Oil Seepage Oil has seeped to the surface in a few locations in and around the park. The oil comes up through cracks in the sidewalks, cracks in the streets, and in a rare case, through a home owner ' s lawn. The oil is even more viscous than that on the water table, and in most cases solidifies as it weathers and biodegrades . Some of the seeps have stopped while others continue to be active. There are three locations where oil is seeping to the surface. (See Figure 4 . ) These were located by talking with the citizens in the area and by asking them to point out any areas where liquid oil was seeping to the surface. To stop the active oil seepage, we plan to excavate the three areas where seepage is occurring, and if the source of the oil appears to be deeper than 3 or 4 ft, we will install small vaults to collect the oil periodically. It ' s possible that after exca- vating to a depth of 3 or 4 ft, the oily soil will be removed, eliminating the source of the seepage altogether .