SITE INFORMATION AND CORRESPONDENCE

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ri ReLicmal Recommendation Page 19 of 2y I Appendix A 6. N1=AR Criteria lot L'ovv Risk vadose Lone reyuiied in itll cases unless i1 can be shown Cases that the collection of such sampling) is unreasonable or unattainable. (e.g.. the Vadose zolic cases are those sites for which estimated"depth to water is greater than 100 documentation'has been provided to demonstrate feet below the deepest soil impacts). that fuel h\drocarbons or additives have iiot reached and are riot expected.to reach 6.4 NFAR for Cases Above Background groundwater. If site conditions do not Meet the Groundwater Conditions criteria below. then additional .remediation ma[y be required. All of the following mtisl'be Ideally. the goal of remediation is to ensure thaw demonstrated in order to designate a vadose zone contaminants are cleaned up to background water site as lots risk" quality. 1-lo�+ever contanlinants may be allowed to remain in the ground\+ater above back round I'. the release has been stopped and the levels in certain cases. Any proposal to leave _ source of contamination has been removed contaminants in proundwater at levels above orrenlediated. Soil that contains mobile back 21 round must include.justification for such constituents in concentrations that threaten de-uradaiion. Cleanup levels above background to degrade water quality or result ill a must also conform to all applicable state policies. significant risk to hurnan health and safety regulations and procedures. See Policy/or or the environmenf (asdeteriiiined by site Ing-esti 0linn and 0(1(7n7iJ� cif Con/aminnreri.Ci1eS _. specific data. or as concluded using in Chapter IV of the Water Quality Contl"01 flans appropriate mathematical models) should (Basin Plans)for the Central Valley Region. be considered a source_. Central Valley Regional Water Quality Control The site has been adequately characterized. Board staff have closed UST cases that do not The vertical and laieral,ement of subsurface meet background water quality levels. but the impact must be defined to the degree that it water quality objectives at the site are met. or-a\ill is necessary to evaluate whether the site be met within a reasonable timeframe. In most of c.irrenily poses, or in the future tnay pose. a these instances. concentrations of pollutants were significant threat to human health and either below or close to applicable water qualiry . safely. v\aiers of the State; or other nearb\ obJectives prior to closure. sensitive receptors. The level of detail required at a aiven site,will depend on the Cases that have been closed above backaround contaminants of concern, the types of levels in groundwater were deemed to be low potential receptors and exposure pathways. risks jo other receptors such as surface water and. and the proximity of the potential receptors. drinking water wells. Regional Board staff Groundwater beneath a site and adjacent considers the followinL) love risk factors \vhen Surface waters are to be cotis'idered as making this determination: receptors. 1. The source of the UST release has been No waters of the State, or other sensitiveidewified,and removed. receptors are likely to be impacted. Waters of the State include all �iraundwater and ?. Free-phase product in groundwater has surface water regardless of current use.. been removed to the full extent practicable. Central Valley aquifers generally are not in accordance with the UST Regulations se_sregated into discrete units. but are (Title.23. CCR. Section 2655).. subject to \eriical and horizomal:nllgratlon " of coater (either by natural or man-induced 3. :Contaminants remaining in the vadose zone mechanisms) and any pollutants carried by cannot migrate in soil'vapor or leach at or in the coater nrav degrade the waters of concentrations that would cause rhe State. Groundwater sample(s) are