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-a- neither the oily soil or the groundwater would be classified as hazardous by the regulatory criteria of the California Department of Health Services. Results of Mitigation Efforts in 1988 In 1988 , Chevron completed the work outlined in our Preliminary Mitigation Plan ( 3 ) . This work was described in detail in our first Work Plan ( 4) . We removed oil seeps, planted trees, tested two mitigation technologies, and received approval for the final mitigation plan. The excavations of the oil seeps successfully removed the most immediate problem at the site. One active oil seep has been identified since the last excavations. It will be removed as part of this Work Plan. If additional oil seeps appear, they will be excavated also. We planted six trees in Alden Park in specially designed plan- ters. The planters prevented any contact of the tree roots with contaminated soil. However, some of the trees still did not grow well . In consultation with Dr. Robbie, a plant pathologist from U.C. Berkeley, we have concluded that standing water in the park is drowning the tree roots. As part of this Work Plan, we will verify this conclusion and suggest ways to minimize the effects of standing water on the trees . Two potential mitigation processes were tested to determine how effective they would be at mitigating the oil contamination. A test of liquids pumping was conducted for Chevron by Dames and Moore. (See Reference 5 for the Work Plan. ) Liquids pumping removes oil by pumping groundwater and any oil floating on the groundwater to the surface for treatment. Chevron conducted a test of bioventing in the summer . (See Reference 4 for the Work Plan . ) The bioventing process uses a vacuum pump to draw air through the soil. Once the soil is aerated, naturally occurring microorganisms biodegrade the oil. The conclusion of these tests was that a combination of both liquids pumping and bioventing was the best mitigation r g process. Mitigation Plan Chevron has submitted a Mitigation Plan ( 6) to the RWQCB. The objective of the Mitigation Plan is to remove the nuisance of liquid oil flowing to the residents of the Alden Park area. The RWQCB has given approval for Chevron to proceed with the plan. In the first phase of the plan, mitigation will begin with com- bined liquids pumping and bioventing in a single well at the existing bioventing facility. Figure 1 shows the location of the existing facility. Chevron will operate this first phase long enough to gain additional design data. Then a full-scale system