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alluvial water is naturally higher in metals and disso:Lved soli de than the <br />mine discharge water, no other impacts on the water quality are expected. <br />Bffects of Seepage from No. 9 Portal Backfill <br />The No. 9 Mine portal backfill has a surface area of approximately five <br />acres. IIsing an infiltration rate of three inches per year, the annual <br />infiltration will be less than one gpm. This amount ie~ insignificant and <br />will therefore have no measurable effect on nearby aquifers. Also, the <br />backfill area is stratigraphically separated from the r.~.earest aquifer, the <br />Twentymile Sandstone, by 360 feet of very low permeability interbedded <br />claystone, siltstones, and sandstones. <br />NPDES Discharge Monitoring <br />A. Sedimentation Ponds <br />Information on the sediment control system is presented in Section 4.05 <br />and in Exhibit 18 of the permit application. Permit Map 26 shows the <br />location of the components of the sediment control system. <br />All surface disturbance at the Eagle Mines, other than those areas dis- <br />cussed above, ie routed to sediment ponds designed •to treat the water <br />for suspended solids. Runoff from the surface dietirrbance areas ie <br />routed to sediment ponds by a series of diversion ditches. All undis- <br />turbed drainage, where practical, is routed by collections ditches <br />around the disturbed areas and discharges. directly to the natural <br />surface water system. Therefore, the amount of runoff water needed to <br />be treated by the sediment pond is minimized. <br />Stipulation No. 5 had previously been attached to ttce permit which <br />required Cyprus Empire to submit updated versions of permit map 26 and <br />permit exhibit 18. This stipulation was relieved upon Division <br />approval of Technical Revision No. 8 (October 1987), which satisfied <br />the Division's requirements. <br />B. Water Quality Standards and Sffluent Limitations <br />Several areas at the~Cyprvs Smpire Mine Complex have been granted small <br />area exemptions which exclude the need for drainage to pass through a <br />sedimentation pond. These exemptions have been granted based on the <br />areas.being small, that there ie no mixture of surface drainage, with <br />~~~~diecharge from~the underground mine workings, and that sedimentation <br />ponds or treatment facilities are not necessary for the drainage to <br />meet the effluent limitations of 4.05.2 and applicable State and <br />Federal water quality requirements for receiving wat~.re. The small <br />area exemptions are listed below. All calculations +ind demonstrations <br />for SAE's are found in Exhibit 18 of the permit. <br />Rock Dust Tanks - Tanks are fully enclosed. Tank sire disturbance <br />areas are small (less than one acre), surface is gra~reled and they are <br />located away from any receiving streams. <br />No. 5 and No. 6 Miae Water Facility - Rule 4.05.2(4) does not require <br />sediment control from this type of area. Outslopes gave been <br />stabilized with vegetation. <br />Sewage Lagoon and Polishing Pond - Rule 4.05.2(4) does not require <br />sediment control for this type of area. Outslopes have been stabilized <br />with vegetation. <br />Boreholes - Mine dewatering or fresh water cased drill holes, less than <br />200 square feet of disturbance each. <br />28 <br />