2001-12-11_PERMIT FILE - C1980007A (4)

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COLOR; IDO DEPARTMEM OF PUBLIC HEALTH AND ENVIRONMEM, Water Qualiry Contra[ Division Amendment No. 4 -Rationale. Page 2, Permit No. CO-0038776. • Table II-1 -Discharge Points (continued) Outfa/! Corresponding Wastewater IO-yr/24-hr Design Capacity Receiving Rater Permittee ID Source(s) Event Vol 016'•' combination ,NW, SR, FW" 0.606 ,ti1G NA No Fk Gunnison R 017 MW tti1WTF hIW NA 2.83 MGD W. Fk Sylvester G 018 MW ~YIWTF SR SR - - W. Fk Sylvester G MW means mine water, ,NW(F means m[rte water treatment faciliry, SR means surface runoff. No Fk Gunnison R means the North Fork of thr G[nrtisan River. W Fk Sylvester G meant Wrst Fark of Sylvester Gulch. ' This pond receives unaf[ered fresh water (FW) from [he .Yorth Fork of [he Gunnison River and po[en[iatly from pond A18-1 (outfa/l combined with aurfall 002 plus mine waver to form new outfall 016). Ourfa[l 007 discharges to autfall 004, which subsequemly discharges to the North Fork of the Gunnisors River. "• This is a new autfall that Combines former ourfa[ls C02 and 006 plus mine flow directly from the portal. Outfalls 002 and 006 are shown crossed out to indicate that they will be eliminated from the permit tivhen the netiv combined outfall 016 is activated. III. PURPOSE OFA.~fENDttilENT This amendment addresses two letters front the permittee. • In the first leaer, dated .4pri1 23, 1997, they seek to combine two existing ourfalls, 002 and 006, into a new discharge point - to be described as number 0l6, and add direct mine water flow into this combined flo}v. 73tese two individual points have always discharged into a common culvert that flows to the tVorth Fork of the Gunnison River. This culvert is not "state waters ", only a conveyance to state waters. Thus, there would be no change in operation. Recently, much more mine tivater flow has occurred than before. This mine water }vas unexpected and itas been diverted into Pond ,YIB-1 (outfa!! 00?} and/or Pond ,Y1B-2R (otttfa!! 004}, tivhere it mixes with any stormtivater and subsequently is discharged. These ponds are not sized to handle these volumes of mine flaws plus the surface runoff: T/te ability to discharge mine water directly into the culvert (only when it meets effluent limitations without treatment) •,vould free up capacity in the ponds for rain and/or snow generated runoff. This permit amendment should accomplish this and is ezpecred to result in no apprecia6fe change to the effect seen by the receiving water since these discharges currently combine at the culven. !n fact, the improved fletibility could result in improved discharge quality. Additionally, the permittee would save money on effluent testing since they now test these ourfalls separately, prior [o the point where they combine and enter the culvert. Once this change is approved, a single sampling point, assigned as outfall no. 016. would result. fn the second letter, dared October ?, 1997, the perm[ttee requests addition ojartother new outfall - to be assigned as number 017 The permiaee is constructing a completely netiv mine }voter treatment facility (MWTF) will: the primary focus on total suspended solids. This is the parameter that t/te permittee has determined needs attention. There are rto metals or other pollutants that they have determined to present a problem. This jacifity will, when fully operational, treat all mine water pumped from the mining operation. This will result eventually in the cessation of all mine water discharges from other previously authorized outfalls including 016 (also 004, 01l, 012 and 013). The ~LIWTF is designed to treat an influent with 1.000 mg/Q concentration of total suspended solids (TSS) at a volume of 2, 000 gpm (2.83 :LIGD) and produce an effl[ent of < 25 mg/P TSS. The ,Y/WTF consists of the following units. • • A dewatering pump station and treatment building. TLV0 2.000 gpm deep well vertical turbine pumps will lift wastewater from the mine sump and transport it to the treatment building. Included in the treatment building will be two 1, 000 gpm high-rate flocculation and sedimentation units, chemical feed equipment and chemical storage equipment. A berm will be constructed around the chemical storage equipment to contain any spills.