SITE INFORMATION AND CORRESPONDENCE

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Water Quality Site Assessment -4- 5 November 1992 + Title 22 Metals As, Ag, Ba, Be, Cu, Cd,Co, Cr (Total), Cr+6, Hg,Mo, Ni,Pb, Se, Ti,V, and Zn; General Minerals Ca, Mg, Na, K,Fe, Al, Mn, SO4, Cl, NO3, and alkalinity; and General Parameters EC, pH, and TDS. [Other constituents may need to be added, based on knowledge of past site activities.] 3. Calculate the mean soil extract concentration (in µg/l of WET extract) for each con- stituent in each lithologic unit. Also, determine the standard deviation for each mean calculation. This establishes the site-wide background concentrations of ex- tractable levels in soil extracts for each constituent in each distinct lithologic unit within the unsaturated zone. Constituent Assessment in Assessment Sites for Soils 1. For each assessment site, determine the soil extract concentrations (in µg/l of WET extract) for all general minerals and parameters, and for those Title 22 Metals that are suspected constituents of concern,based on past industrial and disposal activi- ties for that site. [Other constituents may need to be added, based on knowledge of past site activities.] Sufficient samples shall be collected and analyzed to provide data repre- sentative of the range of concentrations present. 2. Statistically compare the soil extract concentrations from each assessment site for each lithology with the corresponding soil extract concentrations from the site-wide background assessment for each lithology: a. If an assessment site soil extract concentration is less than or equal to the site- wide background soil extract concentration for a constituent in a specific lithol- ogy, then ground water quality is not threatened by that constituent, and no further action is required for that constituent in that lithology. b. If an assessment site soil extract concentration is greater than the site-wide background soil extract concentration for a constituent, then that constituent is potentially a threat to ground water, and the assessment site soil extract con- centration must be compared with the site-wide background concentrations for ground water and the applicable water quality limits. 3. In order to compare an assessment site soil extract concentration to background ground water quality and numerical water quality limits, the soil extract concentra- tion must be converted into assessment site soil leachate concentrations,because the WET procedure includes a 10-fold dilution of the soil sample (see Attachment A, a discussion of"Environmental Leachate vs. WET Extracts").