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in March 1996. The results of this monitoring event are reported in the First Semester 1996, Semi Annual Groundwater Monitoring Report, May 1996 ' The monitoring program has indicated that groundwater levels fluctuate seasonally with groundwater elevations ranging from 2 to 13 feet bgs Results of ' each groundwater monitoring event are presented in groundwater monitoring reports submitted to the SJCPHS and RWQCB A comprehensive table listing all of the analytical results from the groundwater monitoring sampling at the site from 1989 to 1996 is presented in Appendix C, Table C-2 The groundwater sampling results ' indicated that a petroleum hydrocarbon groundwater plume is present at the site Initially, the plume did not reach MW-9, but in the fourth quarter of 1994, and periodically since then, low levels of petroleum hydrocarbons have been detected in ' MW-9. MW-9 is believed at be at the leading edge of the plume The monitoring program has also indicated that the concentrations of petroleum hydrocarbons in the ' groundwater beneath the site are decreasing as time progresses indicating that the plume is naturally attenuating 2.4 Remedial Actions In January 1994, an active in situ bioremediation was selected for the site based on the feasibility study The bioremediation consisted of extracting groundwater from a converted monitoring well, mixing the extracted water with enzymes, ' biosurfactants, and amino acids, and reinjecting the enzyme-laden water into the aquifer Prior to designing and implementing the remediation, several tests were ' performed, including a plate count and bench scale study, to further establish that the bioremediation would be successful without negative side effects Initially, slug ' testing was performed at the site to facilitate extraction and injection well design A CAP was prepared as an addendum to the ASA/RO, Addendum No 1 to the Additional Site Assessment and Remedial Options Report Remedial Action Plan, Black ' & Veatch, September 1994, and was submitted in September 1994 to the SJCPHS and RWQCB Because reinjection was proposed, a waste discharge permit was required by the RWQCB The RWQCB raised several concerns regarding the addition of nitrogen to the aquifer and the hydraulic capture of the bioremediation ' system A bench scale study was performed to evaluate residual nitrogen levels and a short duration step draw down test was conducted to further define aquifer parameters The step draw down test was used in place of a pump test to minimize the amount of water extracted and requiring disposal The groundwater extraction ' 96R7 East Say Municipal Utility District 404297M fcr 12 Fina[ Closure Report