SITE INFORMATION AND CORRESPONDENCE

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Water Quality Site Assessment -2- D.UFT 5 November 1992 ` 2. Collect filtered ground water samples, and ensure that no sample aeration takes place. At each sampling location, collect a sample from all hydrogeologic zones identified beneath the water table. Analyze each sample for the following dissolved constituents and parameters: 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 and the standard deviation of the mean dissolved concentration for each constituent and parameter in each hydrogeologic zone to establish site-wide background concentrations for the different ground water zones. Constituent Assessment in Assessment Areas for Ground Water 1. For each assessment area, determine the dissolved ground water concentrations for all general minerals and parameters, and for those Title 22 Metals that are suspected constituents of concern, based on past industrial and waste management activities for that area. [Other constituents may need to be added, based on knowledge of past site ac- tivities.] 2. Statistically compare each constituent's dissolved concentration from each assess- ment area for each hydrogeologic zone with each constituent's background ground water concentration for that ground water zone. a. If an assessment area ground water concentration for a constituent in a specific ground water zone is less than the background ground water concentration for that constituent in the same ground water zone, then the constituent is not a constituent of concern for water quality. No further action is required for that constituent in that ground water zone,provided that the concentration does not present a risk to human health. b. In an assessment area, if the concentration of a constituent in a ground water zone is greater than the background ground water concentration for that con- stituent in the same ground water zone, then the constituent is a constituent of concern for water quality. This means that ground water degradation has oc- curred and ground water remediation may be necessary. In addition, if the same contaminant is present in overlying soils, contaminant breakthrough has occurred and no attenuative capacity is available for that constituent within overlying soils at that site.