PERMFILE62071 - Laserfiche WebLink

Home Browse Search

to Foidel Creek from Pond F occurs primarily as a result of • discharge from backfill areas updip of the pond. This discharge is concentrated at a spring area known as the Pond F Spring. The primary sources of discharge to Foidel Creek in this area during low flow periods are the underground mine discharge and the backfill discharge. During low flow periods surface runoff is relatively minor in comparison to these perenial sources. During this time, these sources constitute almost the entire flow in the creek and have resulted in the creek exhibiting perenial flow characteristics downstream from the CYCC and TCC operations. During the spring snowmelt period, as indicated by Pond F Spring discharge records, the backfill discharges increase dramactical- ly. Underground mine inflows have not shown any appreciable seasonal variation. Natural surface runoff during this time also results in appreciable flow in the creek upstream from the mine related discharges. The effects of solute contributions to the creek from both the underground mine discharge and the backfill discharge during this period will be less pronounced than during low flow periods. The major concern of potential increases in Foidel Creek solute concentrations as a result of mine-related discharges is the possibility of material damage to downstream alluvial valley floor (AVF) areas. AVF areas have been delineated at the • confluence of Foidel and Middle Creeks, and also on Trout Creek downstream from CYCC's operations. Irrigation of these AVF areas is from direct diversions of creek waters. It is important to note that direct diversion of Foidel Creek water is not presently practiced or has ever been historically practiced. The first diversion of surface waters that could potentially be effected by mine-related discharges to Foidel Creek is at the Jefferson Ditch on Trout Creek downstream from the confluence with Middle Creek. The AVF area at the confluence of Middle and Foidel Creeks is actually irrigated using waters derived from Trout Creek diverted at the Leiske and Connell Ditches and from Middle Creek divested at the Leiske Ditch. Consequently, a salt load analysis is really only applicable on Trout Creek downstream from the confluence with Middle Creek. For worst case conditions, the analysis was performed for the lowest flow period during the irrigation season which would be Septem- ber. During this period, effects of mine-related discharges are at a maximum as the underground discharge and backfill discharge constitutes almost all of the Foidel Creek flow in this area. The salt load analysis for evaluating the effect of the CYCC operations may be performe3 separately from the underground mine contributions. However, in an overall evaluation the total effects of both contributions should be considered. u 15