2019-01-15_REVISION - M2018057 (2)

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Ground water will not be encountered. Removal of the mine waste material is expected to improve ground and surface water quality. Surface water impacts will be controlled through implementation of our Stormwater Management best management practices. A Stormwater management Plan(SWMP)has been designed specifically for this operation and a permit has been applied for with the Colorado Water Quality Control Division. A copy of the Stormwater Management Plan is available. Stormwater Management controls could include using silt fences and/or straw bales during removal to the mine waste. Hydrologic Data North Clear Creek is the significant watershed of this vicinity and it bears approx.4.0 miles to the east and 1,800' in elevation below the Affected Area. Drainage from this watershed area follows down Russell Gulch to North Clear Creek. There are limited perched zones and no traditionally defined aquifers in this mountainous area. The site is completely composed of crystalline Precambrian rocks, i.e. gneisses and schists,and tertiary intrusive rocks such as quartz monzonites overlain by 0-24"of unconsolidated material. Ground water wells within two miles of site boundary are detailed in a map, Attachment 1'I. sourced from the Colorado Division of Water Resources. The groundwater in this area is unclassified per the CDWR and is primarily considered surface water recharge. Attachment ICI, Addendum IV shows permitted and unpermitted wells and structures. Unconsolidated materials,soils,of between 0 and 24"overlay the crystalline rocks. The rocks themselves have essentially no porosity or permeability. Random,in-identifiable fractures due to jointing and faulting provide the only groundwater transmissivity and relative porosity. The site is underlain by numerous mine openings,the most important of which is the workings of the Old Town Mine(mine complex immediately adjacent to the east). This mine's workings effectively drain the area underneath the site,connecting the Old Town to the Argo Tunnel via the Hot Time Lateral. Refer to a map from USGS Professional Paper 359,ECONOMIC GEOLOGY OF THE CENTRAL CITY DISTRICT GILPIN COUNTY COLORADO.Sims, P. K.Drake,A.A.,and Tooker,E. W., 1%3. Hydraulic conductivity for the undisturbed rock types present at the site, in-situ before mining, ranges from 10-2— 1012 gallons per day per square foot(as reported by Freeze and Cherry (1979))dut to joints and ffiuutures in the rock. The existence of the underground mine workings provide a direct hydraulic conduit for groundwater beneath the site. As previously stated,the Argo Tunnel is within the vicinity beneath the proposed Affected Area at a depth of approximately 1,500 feet. The condition of the existing ground water is significantly worse than the SPLP lab analysis of leachate from a regionally oVical abandoned 34