Laserfiche WebLink
Mr. Gabe Racz Page 2 of 6 <br /> November 28, 2016 <br /> carried out various exploration and surface mining activities, the most recent including crushing <br /> previously mined ore and chemically extracting traces of gold and silver. The purpose of this <br /> SWSP is to provide replacement water for that consumed during the various mining operations <br /> on site. <br /> DEPLETIONS <br /> Stream depletions occur to Fourmile Creek from mining operations. CC&V's gold mining <br /> operations contain areas (such as leaching pads, fuel farms, etc.) permitted by the Division of <br /> Reclamation Mining & Safety to be zero-discharge, which capture all precipitation and result in a <br /> reduction of runoff from precipitation. Maximum monthly depletions to the Fourmile Creek <br /> drainage were calculated based on the maximum number of acres of zero-discharge area that <br /> will occur. Zero-discharge areas within the Fourmile Creek drainage are subdivided into those <br /> overlying the volcanic diatreme (a more porous geological area containing the mined deposits) <br /> and those outside the boundary of the diatreme. Capture of precipitation is considered to affect <br /> stream flow on a lagged basis, and CC&V has computed lagging for each area separately. <br /> Should the actual land area of a zero-discharge zone be less than the acreages used to <br /> compute the maximum depletion; the actual depletion will be reduced proportionally. <br /> Pursuant to§ 37-92-305(12)(c), C.R.S., the amount of replacement water provided <br /> under this SWSP for the zero-discharge areas will equal the precipitation upon the zero- <br /> discharge (lined)areas, less the historical evaporation and evapotranspiration that would have <br /> occurred prior to construction of the zero-discharge areas. For the purposes of this SWSP, it will <br /> be assumed that 70%of the total precipitation was historically consumed by evaporation and <br /> evapotranspiration prior to construction of the zero-discharge areas. <br /> This SWSP will also replace depletions resulting from evaporation of precipitation and <br /> runoff from sediment detentions ponds that capture stormwater out-of-priority. Table 4 in the <br /> SWSP submittal materials shows the estimated monthly evaporative depletions from sediment <br /> ponds. Actual depletions will be assessed on any pond that contains a free water surface for <br /> more than 72 hours using the monthly evaporation rates given in Table 4, pond surface area, <br /> and number of days the pond contains water. <br /> Finally, depletions will also be replaced from the pumping system where water is <br /> pumped back from an underdrain and spring collection system intended to reduce potential <br /> hydraulic head at the base of the mine's engineered liner system. This pumping will be metered <br /> and replacements made equal to pumping, in the following month. <br /> The depletions to Fourmile Creek have been estimated to be 263.5 acre-feet/year <br /> resulting from interception of precipitation on the lined areas, 31.6 acre-feet/year from the <br /> detention ponds and 13.4 acre-feet/year from the pump back system; totaling 308.5 acre- <br /> feet/year. According to the application, there are 0 acre-feet of depletions to the West Beaver <br /> Creek drainage basin associated with lined areas, and only 8.6 acre-feet/year from the sediment <br /> detention ponds. Therefore, the total replacement requirement has been estimated to be 317.1 <br /> acre-feet/year. <br /> REPLACEMENT <br /> The sources of replacement water for the augmentation plan include the following: <br />