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r ~e e<Cayr7io~+• f li.t~7 is " ~jt' fJ. ~ .. /~ ; f- ..t.. ~ f U ~l ~( 6T-/ !/' E° ~'~'~~~ vLt ~H ~ Larry Oehler j~s, ~~,~,,P w,~/- ~~, v~-rf, f°~ p~, 1990 ~; It would appear that the glacial valley, in which the Alma Placer occurs, contains a shallow alluvial aquifer recharged by snowmelt rom the surrounding ten mile range and frequent high intensity-sho t duration thunderstorms. Assuming a ground water table of 10-15 fee below the surface in the proposed disturbed areas, it appears from t e contours on Plate 4 that all excavations will be inundated. The Divis on recanmends that Reclamation Resources predict the feasible limit (dep ) of excavations. This limit may be determined by a number of actors such as stream characteristics (gaining or losing stream), depth t groundwater, equipment limitations. and storage capacity for ground wat r inflows in the recirculation ponds. The Division would like to know he minimum elevation of the area to be mined and the corresponding de th of excavation and elevation of the adjacent river channel. Reclamation Resources has proposed to back fill excavations with processed gravels when excavation is completed. The Division agrees with this approach and recognizes its importance in maintaining site stability. However, it is unclear in the application what the maximum size of excavation will be at any one time during the operation. his information is necessary for determining the volume of pit inflows. Please submit the expected maximum size of excavation for ach area to be mined. The placement of back fill into excavations adjacent to the Middle Fork of the South Platte River would appear to constitute placemen of fill ~ material into wetlands and/or waters of the United States nd require approval from the U. S. Army Corps of Engineers. The Division requests C.r(1 ~ that the applicant contact the Corps of Engineers regardin the need for~,/y~~ a 404 Dredge and Fill Permit and submit copies of all corr spondence. 'G,r.«<~ This measure will ensure that Reclamation Resources is in appliance with 7~"~,.3bi Section 115(4)(c) of the Colorado Mined Land Reclamation Act 34-32-101 et. seq., C.R.S. 1973 which requires that a permit applica ion be in compliance with all applicable local, state and federal la s. 5. Water Management System - Impoundment Design Reclamation Resources has proposed the construction of imp undments for water management purposes The ponds may be located in ackfilled areas and will be used to contain process waters for the R ss Sluice Box, ground water encountered during excavation, runoff waters from the disturbed area, and irrigation water for reclamation. Reclamation Resources prefers to construct the ponds unlined, allowing for water to percolate through the ground and return unchanged in quali to the surrounding alluvial aquifer. The Division has concern regarding the design of ponds used for water management purposes at the proposed operation. A water bal nce for each phase of the mining operation should be included in the ap ication. Each water balance should include all hydrologic inputs and outputs for that particular phase of the operation. If the result for ach phase is a net excess, then Reclamation Resources should specify wh a the excess water will be stored or whether the excess will be dischar d to the South Platte River. An NPDES water discharge permit will required for a point source discharge from the disturbed area to the So th Platte River.