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i:a:er (tial.ity Control Division ' 4210 East 11th aye au¢ • uent•er, Colorado 802?0 ADDEIaU?: TO R.4TI0"]ALE COLORADO 'iAMP:1 CGAL CC. PERPiIT NL~dBER: CO-0027154 RGUTT NL1'TY The permittee submitted a letter dated January 13, 1983 info:-cing the Division that the permi[tee is planning to expand ope-ations and perform underground coal wining at the site. Y:ater from the underground mine would be pumped to a sump. From [he sumo the water would be pumped to pond D, and *_o Foidel Creek through pernitted discharge point 005. Pre ser.tly, discharge point 005 has technology based, federal effluent limitations (BPT} for iron and total suspended solids. These limitations were placed ir. the permit because the pond was designed tc contair. runoff iron surface mining activities associated with Mine !'1. Discharges of runoff fzon the pond ccincidad with hiDh :..-stream flogs and it is the D'_vision's position that under these citcur..stanees more stringent limitations are not required to caintain instream water quality standards. The proposed urderg-eund mine is e:;pected to pro~uce more water than occurred fror_ the surface mite. In addition, the drainage from the underground ^ine would occur ov er a'_1 seasons of the year, not just in response to • precipitati:;n events. Based or. the projections submitted b}• the permittee, flows from t},e undergrouni mine will increase from 49 fpm in the 1st }•ear o: mining to over 1600 gpm ir. the 4th year. These rates of flow fror the nine will resLlt in a continuous or nezriy continuous discharge of water from GOS by January 1, 1984. Pond D w:zich has discharge point 005 as it's outfall has a total capacity of appro::imately 51 acre-f t. of water without using the emergenc}• spillwa}•. Eased on the calculations of the :•II.P.D, the goad needs 23.6 acre-_[, of storage *_o handle sediment. This is a censarvative figure and subject to change. However, i*_ is a .equirement of ?iLRD at this moment. In addition, 6.% acre-ft. of storage is required to handle runoff from the 10 year-24 hour storm event. In total, 3C.3 acre-f t. of storage is needed for sediment and runoff without considering the underground mine drainage. Thus, 20.i acre-f t. of storage is available for underground mine drainage. [;rainage from the underground trine is projected to be .19 acre-Ft.jda}• in }-ear one, 3.3 acre-f t./day ir. year two and reaching i.2 acre-f t./day in year four. In year two there would be appro::imateiy 6 days of storage available, in year four, only 3 da}•s of storage. Currentl}• the pond is designed to discharge almost continuously as water is collected. At the volumes of water projected to flow :tom the mine a continuous discharge would occur. Since a continuous discharge will occur instream water quality standards must be protected in the permit. •