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Tri Regional Recommendation Page 15 of 24 Appendix A (i.e.)local water supply wells,buildings • Excavation; or utilities impacted or potentially threat- • Soil vapor extraction; ened). • Bioventing; • Bioremediation(bio barriers); • A risk assessment will be necessary to Groundwater extraction and treat- demonstrate that the site poses no unac- ment; ceptable risks to human health or the Biosparging; environment. The site-specific risk as- In-situ oxidation; sessment must use the Office of Envi- Dual-phase extraction and treatment ronmental Health Hazard(OEHHA) and toxicity date (cancer slopes). This in- Monitored natural attenuation. formation may streamline the considera- 2. The rationale for selecting the preferred tion of remedial alternatives and the remedial alternative for restoring and pro- timeline for implementation. tecting impacted or threatened waters. Appropriate conclusions and recommen- 3. A timeframe for achieving remedial goals. dations for the next phase of work. • An updated Site Conceptual Model illus- 4. A cost comparison for remedial alterna- trating site conditions showing the extent tives evaluated. of known soil and groundwater impact With minimal investigation and explanation, relative to the leaking UST system and some remedial alternatives may be eliminated as the relationship between contaminants simply not feasible for the site. For instance, and potential receptors. (See Figure 1 be- soil vapor extraction is practical in sandy soils low for an example). but difficult to justify for tighter clay soils where excavation and landfill disposal may be more 4.2 Feasibility Study(FS)Report effective in meeting cleanup levels. The FS Report provides a summary of remedial Note: If the proposed alternatives include either alternatives evaluated to address applicable soil disposal to a landfill, groundwater discharge cleanup levels for affected or threatened human to the sanitary sewer,or venting vapor to the health and/or waters of the State. The FS Report atmosphere, etc.,the discharger must include must include a cost evaluation for at least two assurances from each appropriate regulating remedial alternatives and a recommendation for agency that the proposed activity is acceptable the preferred remedial action. The FS should and permissible. identify the preferred remedial technologies and may recommend pilot testing of the selected re- medial technologies before full-scale design. The FS Report is to include the following mini- mum information: 1. An evaluation of remedial alternatives that have a substantial likelihood to achieve cleanup of all impacted soils and/or soils and groundwater. At a mini- mum,two of the following technologies must be evaluated for implementability, cost and effectiveness, (other technologies not listed may also be evaluated):