SITE INFORMATION AND CORRESPONDENCE_FILE 1

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5.3 Recommended Remedial Alternative According to CCR Title 23, Chapter 16, Article 11, at least two alternatives must be identified and evaluated for restoring or protecting beneficial water uses. In addition, each alternative must be designed to mitigate nuisance conditions and risk of fire or explosion. Two alterna- tives were considered below. 5.3.1 Alternative 1: Natural Attenuation This alternative consists of the following elements: (1) complete downgradient plume defini- tion, (2) groundwater monitoring, and (3) preparation and implementation of a contingency plan that includes engineered health and safety management controls. Remediation monitoring is an aspect of the existing site remediation program, and will continue to be a key aspect of any remedial alternative. In addition to the current monitoring program, remediation monitoring would be performed to maintain compliance with any implementation permits, and to evaluate progress toward attaining the remedial objectives including the collection of groundwater parameters to verify that intrinsic bioremediation is occurring. Also, monitoring will be used to demonstrate plume containment and to monitor and document the presence of chlorinated compounds in groundwater beneath the site. Engineered health and safety management controls will be used to reduce the possibility of exposure to petroleum hydrocarbon-affected groundwater at, or from, the site. Currently, access to hydrocarbon-affected groundwater is controlled by sampling protocol and general plume location. Long term site occupancy by Chevron operating a service station will dictate land use and will preclude any public use or contact with groundwater. 5.3.2 Alternative 2: SVE/Air Sparging with Treatment In addition to groundwater monitoring, engineered health and safety management controls and plume definition, this alternative includes: (1) design and installation of SVE and sparge systems, designs would utilize existing wells when possible; and (2) subsurface injection of compounds found to be limiting bioreclamation (other than introduced by SVE and sparging). This alternative would include additional design and abatement due to the presence of the chlorinated compounds which occur beneath the site. Application of this alternative would require installation of a SVE system and integral sparge system. Given the thickness of the capillary-fringe soils, the SVE well field would be installed utilizing vadose wells screened in hydrocarbon impacted areas. Sparge points, equipped with approximately 2 feet of screen, would be installed so that the top of the screened section would be approximately 5 feet below the average groundwater surface. Operation of the 3201357B/CAPREVI 13 June 29, 1995