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• Page 3 December 23, 1998 ongoing geochemical evaluation of the CKD to assure that the nature of the materials to be placed in the disposal area remain consistent in terms of the leachable; chemical composition. 6. Ground W Ater Protection One upgradient and two downgradient ground water monitoring wells were installed to evaluate the hydrogeology of the proposed CKD disposal site. These wells appear to be appropriately situated to detect any ground water impacts that may occur as a re:~ult of CKD disposal. However, no samples have been collected for analysis of ambient ground water chemistry up to this point. The hydrogeological and geochemical evaluation conducted indicates that the disposal of CKD in the played out quarries will not adversely affect ground water quality. In order to assure that no adverse impacts are occurring, the DMG will require that a ground water monitoring program be implemented at the site in accordana~ with Rule 3.1.7 of the Construction Materials Rules. The initial step in the implementation of Rule 3.1.7 is the characterization of ambient ground water quality. This will involve the collection of 5 quarters of ground water chemistry data from the three monitoring wells that have been installed. Data from the 2 downgradient wells can be considered to be ambient data up until the time that initial CKD disposal occurs in the proposed disposal area. Once CKD disposal has commenced, only information from the upgradient well can be presumed to represent ambient ground water quality. iHolnam must provide a concise plan for the characterization of ambient ground water quality. This plan must include a description of the method of sampling and the frequency of sampling and reporting to the DMG. The plan must also include a list of parameters to be anaalyzed and specification of water quality analysis methods and quality control and quality assurance measures to be employed. The DMG suggests that for ambient ground water quality characterization afull suite of parameters be evaluated over the five quarter characterization period. A full suite of parameters is listed in tables 1-4 of 'The Basic Standards fo_r Ground Water" Regulation 41, (5 CCR 1002-41). It is particularly important that pH and total dissolved solids (TDS) be included in the ambient quality characterization because these parameters would be good indicators of CKD derived leachate present in ground water. Items from tables 1-4 that could be excluded from the characterization parameter list would be asbestos, chlorophenol, color, corrosivity, foaming agents, and phenol. Once ambient ground water quality is established, a more limited set of parameters may be monitored for the purpose of contamination detection monitoring. Since arsenic, barium, chromium, lead, selenium, and thallium were all detected at levels above the practica{ analytical quantitation limit in the SPLP leachate, these metals must all be on the list of parameters included in the detection monitoring plan along with pH and TDS. The collection of ambient ground water quality data over a period of 5 quarters, as discussed in the previous paragraph, is taken from the Hard RockiMetal Mining Regulations at Rule 6.4.20(9)(b). However, in order to conduct a valid statistical analysis of the dat~-, it is the DMG's position that at least eight data points will be required. In order to collect sufficient data for statistical analysis, it is suggested that Holnam collect two samples per quarter over the 5 quarter time period. The samples should be collected at as close to equally spaced time intervals as possible. Once the ambient ground water quality is established, numeric protection levels for ground water will be specified and points of compliance determined. The frequency of sampling,