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PREFERRED ALTERNATIVE <br /> The preferred alternative for groundwater cleanup at DDRW-Tracy OU #1 is Alternative 3, <br /> groundwater extraction at 1000 gpm with treatment by air stripping and vapor-phase carbon <br /> and injection to the upper and middle horizons of the aquifer. Alternative 3 has been <br /> determined to be protective of human health and the environment for exposure to <br /> groundwater, to be cost effective, and to be implementable in a timely manner. <br /> Alternative 3 represents a significant expansion of the current IRM, both on site and off site. <br /> It will prevent further migration of the contaminated groundwater and will, in time (estimated <br /> at 45 years), remediate the contaminated aquifer to health-based cleanup levels. <br /> Alternative 4 includes all of the components of Alternative 3 and adds an in situ biological <br /> treatment feature. This feature has promise to accelerate and improve cleanup of the most <br /> heavily contaminated part of the aquifer. However, it is untried at full scale and would <br /> therefore require significant advance testing and experimentation and would be significantly <br /> more costly. It is not preferred at present for these reasons, but could be considered in the <br /> future to enhance the effectiveness of Alternative 3. <br /> HOW TO COMMENT <br /> Please review and comment on this Proposed Plan and the draft remedial investigation/ <br /> feasibility study (RI/FS) reports for OU #1 that are included in the Administrative Record. <br /> These documents are available for review at the public library information desk located in <br /> Tracy and at DDRW-Tracy. <br /> Stockton-San Joaquin County Public Library - Tracy Branch <br /> 20 E. Eaton Avenue <br /> Tracy, CA 95376 <br /> (209) 835-2221 <br /> Hours: Monday and Thursday--10 a.m. to 9 p.m. <br /> Tuesday, Wednesday, and Friday--10 a.m. to 6 p.m. <br /> Saturday--10 a.m. to 5 p.m. <br /> Sunday--Closed <br /> Q.WG003.1(90380C)V 6 16 M1007921612 <br />