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0 • EVALUATION OF ALTERNATIVES considered in the future to enhance the effective- ness of Alternative 3. The alternatives described above were evalu- ated using the nine EPA criteria that follow: State Acceptance l.Overall protection of human health and DTSC and the RWQCB have approved the environment use of the existing air stripper system and have 2.Compliance with applicable or relevant and indicated general acceptance of this technology as appropriate requirements(ARARs),which are(1) it was presented for the IRM. Through document the federal and state standards applicable to the reviews and public meetings, the RWQCB and chemicals of concern and remedial actions at DTSC have participated in investigations atDDRW- DDRW-Tracy, and (2)federal and state standards Tracy and have previewed the Operable Unit No. that, while not directly applicable to the site, ad- 1 Remedial Investigation,Risk Assessment,Feasi- dress problems and situations similar enough that bility Study, and Proposed Plan. their use is suited to the site. 3.Long-term effectiveness and permanence Community Acceptance 4.Short-term effectiveness 5.Reduction of toxicity,mobility,and volume Community acceptance will be addressed through treatment based on comments received during the public 6.Implementability comment period. Given the current rapid pace of 7.Cost development in the Tracy area,it can be anticipated 8.State acceptance that neither developers interested in purchasing 9.Community acceptance land near DDRW-Tracy nor landowners interested in selling property near DDRW-Tracy would ac- Figure 3 (page 13) provides a brief explana- cept deed restrictions on residential development. tion of the EPA evaluation criteria. Similarly, existing agricultural landowners near DDRW-Tracy would be unlikely to favor perma- A comparative evaluation of the four alterna- nent well drilling restrictions. The community fives by the first seven of the nine EPA evaluation may perceive other negative socioeconomic im- criteria is summarized in Table 1 (page 14). State pacts (lower property values, restricted land use, and community acceptance are discussed further etc.)associated with deed and aquifer restrictions. below. PREFERRED ALTERNATIVE An alternative must meet the first two EPA criteria to be eligible for selection. Alternatives 1 The preferred alternative for grotmdwa- and2are not preferred because theydonotcleanup ter cleanup at DDRW-Tracy OU #1 is Alter- the contaminated aquifer and do not meet ARARs. native 3: groundwater extraction at 1000 gpm, with treatment by air stripping and Alternative 4 includes all of the components vapor-phase carbon, and injection to the of Alternative 3 and adds an in situ biological upper and middle horizons of the aquifer. treatment feature. This feature hasP romise to accelerate and improve cleanup of the most heavily Alternative 3 has been determined to be 'r contaminated part of the aquifer. However, it is protective of human health and the environment untried at full scale and would therefore require for exposure to groundwater, to be cost effective, significant advance testing and experimentation and to be implementable in a timely and would be significantly more costly. It is not manner.Altemative 3 represents a significant ex- preferred at present for these reasons,but could be pansion of the current IRM, both on base and off 7