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Waste Science and Technology Corp., December 1993 (ASA/RO). The soil and <br /> groundwater data from this additional investigation are presented in Appendix C, <br /> Tables C4 and C-2. <br /> 2.2 Feasibility Study <br /> Following the additional assessment, Black & Veatch developed a feasibility <br /> study to determine the best remedial action alternative for the site. The feasibility <br /> study is presented in the ASA RO and consists of/ the development of several <br /> remedial action alternatives and the evaluation of these alternatives according to <br /> implementability, technical feasibility, and cost. Alternatives included extraction and <br /> air stripping, air sparging and vapor extraction, and in situ bioremediation. An <br /> f innovative active in situ bioremediation was selected as the preferred alternative <br /> based on the feasibility study. <br /> 2.3 Monitoring <br /> Groundwater monitoring was implemented at the site following the first <br /> investigation in 1989. However, the monitoring was not continuous and several <br /> quarters were skipped. Following the additional assessment in September 1993, a <br /> quarterly groundwater monitoring program was implemented. Initially, all nine <br /> f monitoring wells were monitored and sampled. The SJCPHS permitted the District <br /> t to reduce the number of wells from which groundwater samples were collected to <br /> threeMW-1 MW-8 and MW-9 beginning( } inni <br /> g g with the first quarter of 1994. Water <br /> levels were still measured in all nine monitoring wells. <br /> L: <br /> In June of 1995, SJCPHS approved of the following changes in the groundwater <br /> monitoring program: <br /> v Measure dissolved oxygen in MW-1, MW-8, and MW-9 in addition to sampling <br /> for BTEX and TPH-g. <br /> �� • Reduce the number of wells monitored for water levels to seven (MW-1, MW-3, <br /> MW-4 MW-5 MW-7, M - <br /> W 8, and MW-9). <br /> Reduce the groundwater monitoring and sampling frequency to semi-annual in <br /> 1996 and include MW-1, MW-4, MW-5, MW-8, and MW-9. <br /> The District performed the first semi-annual monitoring event in March 1996. <br /> 4 At the request of SJCPHS, methyl tertiary-butyl ether (MtBE) was included in the <br /> list of analytes. MtBE was not detected in any of the groundwater samples collected <br /> 96R7 East Bay Municipal Utility District <br /> 40429700.Fcr 6 Final Closure Report <br /> 4f <br /> I <br /> L <br /> 4 �t <br />