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Work Plan Addendum Attachment -2- 21 September 1992 <br /> DDRW, Sharpe <br /> This does not imply that all sites must be remediated to background, <br /> but rather, all sites must be demonstrated not to have the potential <br /> for impacting ground water if contaminants are left in the unsaturated <br /> zone above background concentrations. If there is no threat to water <br /> quality, no remedial action is required with respect to the particular <br /> constituent. <br /> 2. This type of soil cleanup level determination is based on protection <br /> of water quality. The Department of Toxic Substances Control may have <br /> additional requirements based on the health based risk assessment. <br /> 3. It is assumed that total petroleum hydrocarbons (TPHs) , volatile <br /> organic constituents (VOCs) or any other man made compounds are not- <br /> naturally occurring. Background for these constituents and their <br /> derivatives should be at non-detectable concentrations in soils. <br /> 4. Prior to performing analyses on soil samples, the soluble portions of <br /> the samples must be extracted using a deionized water Title 22 <br /> (Section 66700) Waste Extraction Test (WET) procedure. <br /> a. General Parameters: Electrical Conductivity (EC) , pH, and Total <br /> Dissolved Solids (TDS) <br /> b. General Minerals (with low detection limits, i .e. , ppb range where <br /> possible) : Ca, Mg, Na, K, Fe, Al , Mn, SO„ Cl , NO,, and Alkalinity <br /> c. Title 22 Metals: As, Ag, Ba, Be, Cu, Cd, Co, Cr (total and <br /> hexavalent), Hg, Mo, Ni , Pb, Sb, Se, Tl , V, and Zn. <br /> C. Methodology for Establishing Background Ground Water Characteristics <br /> 1. Groundwater analyses for base-wide background concentrations should <br /> include the following constituents: <br /> a. General Parameters: (as identified above) <br /> b. General Minerals: (as identified above) <br /> c. Title 22 Metals: (as identified above) <br /> 2. The contaminants of concern (COC) derived through the health based <br /> risk assessment process do not take into consideration the impacts or <br /> potential impacts to water quality. Resolution No.68-16 (Anti- <br /> Degradation Policy) requires that the high quality waters of the state <br /> be maintained. Therefore, a soil cleanup value or a water quality <br /> threat determination must be made at every site for any contaminant or <br /> constituent that is above base-wide background concentrations or is <br /> not naturally occurring. <br /> 3. Only those contaminants or constituent that are known (documented) to <br /> have been used, leaked, or disposed of at a site need to be analyzed. <br /> For example, a UST site that was used only for storing clean diesel or <br /> gasoline needs analyses and cleanup values established for only for <br />