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• -2- Oil Seeps We have successfully mitigated the oil seeps that were a nuisance to residents. Six seep collection vaults were installed and three smaller oil seeps were removed by excavating a small area. If seeps appear in new locations, the collection vaults will be an effective way of solving the problem. Liquids Pumping Chevron hired Dames & Moore to conduct a two-week test of liquids pumping. To maximize the recovery of oil , the test was located in a well where the oil has a low viscosity. Under these condi- tions they recovered about 2. 8 gal . of oil and 300 gal . of groundwater/day. However , the rest of the oil in the park is about 10 times more viscous . As a result, liquids pumping would only recover about one-tenth as much oil (about 0 . 3 gal./day) from the rest of the park . Bioventinn Bioventing is a new technology. In the bioventing process, a vacuum pump pulls air through the soil and stimulates the natural process of biodegradation. Biodegradation converts the oil into water and carbon dioxide (a harmless gas) . The clay soil under Alden Park is very dense, so we had to test the bioventing pro- cess to see if it was possible to pull air through it at a prac- tical flow rate. The first part of our test showed that a high vacuum was required to obtain enough airflow. However , high vacuum causes the well to fill up with water and blocks the flow of air . This effect is similar to drinking with a straw. The problem can be solved by combining the liquids pumping and bioventing processes in a single well . At high vacuum, the bioventing process showed a radius of influ- ence of at least 40 ft and it removed more oil than liquids pump- ing alone . The test results were encouraging and it appears that this is the most effective mitigation process for this site.