SITE INFORMATION AND CORRESPONDENCE_1992

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Work Plan Addendum Attachment -3- 21 September 1992 DDRW, Sharpe those types of contaminants. However, in the case of an oil/water separator where the type of waste constituents are unknown, then a complete analysis suite must be performed and compared to background. Once groundwater contamination has been confirmed, a full ground water characterization will have to be performed. 4. Soil cleanup values for protecting ground and/or surface waters can be derived through the development of attenuation values that are site- and constituent specific. California's Water Quality Standards and Their Applicability To Waste Management and Site Cleanup lists several of the factors that should be considered in developing site specific attenuation values. Additional analyses of existing site conditions may be required to satisfy the requirements for developing site and constituent specific attenuation factors. D. Presentation of Results and Findings 1. To aid in displaying that "all" potential contaminants or constituents that may impact groundwater have been assessed at the soil contamination sites, a table should be prepared similar to the attached "Soil Cleanup Determination Table". The table must display which of the constituents that are above background or not naturally occurring will require remediation to protect groundwater. The table assumes that the contaminants are in the soils only and not in the groundwater above base-wide background concentrations. If contaminant concentrations are above base-wide background concentrations in the groundwater then it is assumed there is no site attenuation available in the soils. In this case, remediation must be considered and contamination can only be left in-place as long as the leachate concentration will meet background or appropriate water quality standards and protect beneficial uses. The following must be displayed in the table: a. Base-wide background soluble soil concentrations. b. Site soils' soluble contaminant concentrations. c. The site's weighted leachate concentrations. d. Base-wide background groundwater concentrations. e. Water Quality Standards. f. Required site attenuation to protect groundwater g. Determination whether the site has the required attenuation. 2. The following information is provided to aid in understanding the Soil Cleanup Determination Table: a. Determine the base-wide background soils average extractable concentrations. b. Determine the site's average extractable concentrations.