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' Aprotek's experience indicates that during the first three to four days of the process, the rate of biotransformation can reach 350 to 400 parts per million (ppm) per day As the remediation progresses, this rate has been observed to slow down to 150 to 200 ppm per day The rate of biotransformation is site-specific and is a function of temperature and the availability of food sources A plate count conducted March 10, 1994, by Anlab Analytical Laboratories (Anlab) on a groundwater sample obtained by Waste Science from MW-08 indicated the presence of 930 coliform forming units per gram (CFU/g) of bacteria at the site The ' presence of bacteria in the groundwater at the Stockton site supports the supposition that natural biodegradation is occurring at the site The addition of the enzymes will make the food source more accessible to the bacteria and will increase the rate of ' bloremediation The existing microbial population is sufficient to biodegrade the hydrocarbons ' present at the site The rate of bioremediation may be enhanced through the injection of live bacteria However, because of regulatory constraints concerning the introduction of constituents into groundwater aquifers, this option will not be considered Based on the available information, it is estimated that the plume size is approximately 50 feet by 20 feet by 10 feet, or approximately 74,800 gallons of water With the levels of constituents reported in the groundwater for the Stockton site, it is anticipated that cleanup of the plume to non-detect levels will take approximately two to four weeks ' 2.2 Remedial Design and Well Placement Waste Science proposes that the remediation be implemented through the circulation of the ETEC"' multi-enzyme complex using one extraction well and three perforated injection wells (Figure 2) Based on historical data, Waste Science proposes to convert MW-08 into an extraction well. This well is constructed of 4-inch diameter, Schedule 40 flush- threaded polyvinyl chloride (PVC) casing, with 20 feet of 0 002-inch factory slotted screen The well is screened from 5 feet to 25 feet bgs Because groundwater was encountered at 15 feet bgs in MW-08, this well is adequate for the purposes of extraction The capture radius for this well is conservatively estimated to be 30 feet The rationale for the placement of the infection wells is based on historical data and the anticipated radius of influence of each well (30 feet) It should be noted that,with the exception of the slug test, no further aquifer tests have been conducted 9488 Fast Bay Municipal Utility District 40429601 rap 7 Remedial Action Plan