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RESPONSES TO 1999 ANNUAL HYDROLOGY REPORT REVIEW The DAfG notes that the CDPS sulfate linritatiorr u•crs exceeded for discharges to Trotrt Creek on jour occasions during /999. These erceedances occzrn-ed in July, .9ugust, crud December at D~L1P OOd and in December at Dh1P 007. Bused on review of data from surface water monitoring sites TR-A, TR-B. TR-C, and TR- D, the ntuneric standcu•d jor stdjate for the nrainstenr of Trout G-eek (Segment lac of the }'ampcr River Sub-basin) was not exceeded on anp occasion during 1999. Therefore, there nr•e no specific material drnnrrge issues [o be addressed by the Divisiaz at this time as cr result of the CDPS sulfate criteria exceedances. There is a significant increase in szrlfate cazcentration from the :rpstrenm monitoring location on Trout Creek (TR-A) to the doumstrecrm maritoring point (TR-D). The highest concentration reported jor TR-D in 1999 is 660 mg/l which is within the PHC predicliorr. The PHC prediction contained in the P.9P states that sulfate concentrations in Trout G-eek might be expected to reach an upper limit ojapprorimately 8-l2 mg/l at some time drrrirzg the nrining and post-mining era at the Edna Mine. Please note that D~~/P 007 is not shown on the Water ~Lfonitoring Location A~fap (E.rhibit =t. 6-26). Exhibit 4.6-26 has been revised to show the location of DMP 007 via Tectu+ical Revision 39. On page 9 of the 1999 AHR. P&tL1 stales that "although elevated TDS concerurcrtions hare mored downstream in conjunction +vith mining and reclamation activities, all valises jor TDS are consistent +vith the probable hydrologic consequences projections". /t is evident that there has been a significant increase in TDS concentration from the upsn•enm monitoring point on Troia Creek (TR-A) to the downstream monitoring point (TR-D) in conjzrnction with the mining and reclamation activities. /t also appears that the predicted post-ruining menu annrzal concentration of TDS in Trout Creek has been exceeded for the past several years cr! the downsa•eant moniroring point TR-D. The PHC predictions presented in the P.4P indicate that after mining the [Lest Ridge and :Lfoffnt .4reas, the n:enn TDS conceruration in Trout Creek would be e-•rpected to increase to 330 mg/l. ~L/onitoring data reported in /999 shoo- that the mean nnmral TDS concentration For TR-D ryas =130 nzg/l. Please clarify the statement on page 9 that all vnhres for TDS are consistent with the PHC projections. E-cceedances of PHC predictions should be addressed in fidure AHR's so that any significant trends can be identifred and conchrsions regarding PHC' predictions can be verified. The statement on page 9 refers to the short-term analysis of TDS concentrations provided in Appendix 2.5-A. As discussed in the appendix, in the short-term, the mean TDS concentration value for Trout Creek is anticipated to be 442 mg/I (page 2.SA-7).