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Cne u~gradient and hro dcwnrrad,ent grocnd wa'a~ monitoring w?Its were irstal!ec to eva:uate the hydrogeclcgy of the proposed cement kiln dust (CKD) disposal ere. These wens appear to be appropriately situated to detect any ground water :mpacs ;hat may occur as a result of CKD disposal. However, no samples have been co;tected for analysis of ambient ground vrater chemistry up to this point. The hydrogeclogical and geochamical evaluatron conducted indicates that the disposal o! CKD :n the played out quarries wilt not adversely affect ground v.ater quality. In order to assure that ro adverse impacts are occurring, the CMG will require that a cr~~ t'1 :.a;•~r monitoring program be implemented at trio site ~n accordance vri;h Rule 3.1.i of the Censtructien ;;t~;eri:: s Rules. The initial step in the implemen;a8on of Rule 3.t.7 is the characterization of ambient ground •.va;er quality. This will involve the collection of 5 quarters of ground •.vater chemcstry data from the three mon4cnng wells that have been installed. Data from the 2 downgradient wells can be considered to be ambient data up until the lima that initial CKD disposal occurs in the prccosed disposal area. Once CKD disposal has commenced, only information from the upgradient v:e!I can be presumed to represent ambient ground water quality. The operator must provide a concise plan for the characterization of ambient ground water quality. This plan must include a description of the metnod of sampling and the frequency of sampling and reporirg to the DMG. The plan must also include a Est of parameters to be analyzed and speafication of ~,vater quality analysis methods and quaGy control and qualiy assurance measures to be employed. The DMG suggests that for ambient ground vrater qualiy 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 for 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 teachate present in ground water. Items from tables 1-4 that could be excluded from the characterization parameter list vrould be asbestos, chlorophenol, color, correswity, teaming agents, and phenol. Once ambient ground water quality is established, a mere limited set of parameters may be monitored for the purpose of contamina;icn detection monitoring. Since arsenic, barium, chromium, lead, selenwm, and thallium were all detected at levels above the practical analytical quantization limit in the SPLP teachate, these metals must all be on the list of parameters included in the detecCOn monitoring plan along with pH and TDS. The collection of ambient ground water qual;ry data over a period of 5 quarters, as discussed in the previous paragraph, is taken from the Hard RocWMetal Mirnng Regulations at Rule 6.420(9)(b). However, in order to conduct a valid statistical analysis of the data, it is the DMG's position that ai teas; eight Cata pours wilt be required. In order to collect sufficient data for s;a;is;ical analyse, it is suggested that the operator collect rive samples per quarter over tine 5 quarter time period. The samples should be collected at as close ;o equally spaced time internals as possible. Once the ambient ground vrater quality is established, numeric protection levels for ground waver ~wq be specified and points of compliance determined. The frequency of sampling, method of repertine, and length of post-closure monioring period will also be es;abl~shed. The obvious chokes for points of compliance are the live downgraC'ant wells that are in place. Since this ground water s unctassAied, the numeric protection levels yr l be set according ;o the Ir.;er m I•Jarra;ive Standard for ground waver adopted by the Water Oualiry Corirol Commission v:hich is that qua~ity which meets the most s:nngent cetera set