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. scale, and has been used commercially for full-scale operations by a number of consulting firms at sites around the country The final report of one such full-scale operation is attached to this work plan (Appendix A) Bioaugmentation has been shown to be effective in treating petroleum fuels, including 1•enzene and other aromatic components, especially when the treatment medium can be effective y delivered to the contaminated zone The permeability of the soil within the contaminated zone at the Valley Motors site is sufficient to merit testing of this method, which offers a relatively low- cost alternative to groundwater extraction Cytoculture Environmental Biotechnology,,Me a bioremediation laboratory and services firm based in Point Richmond, California, will provide the bacterial annoculum that will be tested at the Valley Motors site 4 2 1 Bacterial Cultures The selection of specific bacteria for a pilot test should be based on data obtained from the specific site that is under investigation In some cases, it is possible to take native bactei is from the site's soil and groundwater and culture it in a special bioreactor tank for a period of a few days prior to its use Ammonia and phosphate nutrients, pH buffers, and a vegetable oil-based carbon source are added to the reactor to seed the bacterial culture, and a regenerative blower aerates and suspends the bacterial cultures during their initial growth At the time of apr lication, bacterial concentrations should be several thousand colony-forming units (CPU's) per nullilfter of water However, based on the five soil samples that were analyzed by Cytoculture from borings drilled in early 1998, it appears that native bacterial abundance is rather low anc may be . inadequate to produce the required populations In such cases, standarized "stock" bacterial mixtures are used Prior to selecting the culture, groundwater samples,wxll be collected 'rom the on-site monitor wells to determine whether bacteria are present in sufficient quantities 4 2 2 Monitoring Prior to performing any feasibility test, it is necessary to collect baseline data for comparison to data collected later The groundwater sample from VM-2 (see section 4 1 1) will be used to establish the baseline bacterial abundance, and the existing data on hydrocarbon concen rations from this well will be used to assess the effectiveness of the test In addition, because carbon dioxide is a primary product of biodegradation, one baseline air sample will be collected from VM-2 in a Drager tube for laboratory analysis of carbon dioxide The dissolved oxygen concentration in the groundwater sample will also be recorded for future monitoring use The dissolved oxygen concentration will be measured and hydrocarbon, bacteria, and carbon dioxide samples will be collected from the vapor extraction well one month after innoculation for comparison to the baseline samples The results will be used to determine the effectiveness of the method 4.3 Soil Vapor Extraction Another effective in-situ remedial technique is soil vapor extraction, where liquid hydrocarbons are vaporized in place and withdrawn from the soil under a vacuum and treated above grcund This