2011-01-24_PERMIT FILE - M2011007 (7)

Home Browse Search

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 one-quarter mile of site boundary are detailed in a map attached at the end of this Exhibit C, sourced from the Colorado Division of Water Resources. It shall also be noted that the groundwater in this area is unclassified per the Colorado Division of Water Resources and is primarily considered surface water recharge. Unconsolidated materials, soils, of between 0 and 18"-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 True 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., 1963 at the end of Exhibit C detailing this. Hydraulic conductivity for the undisturbed rock types present at the site, in-situ before mining, ranges from 10-2 - 10+2 gallons per day per square foot (as reported by Freeze and Cherry (1979)) due to joints and fractures 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 the abandoned mine dump material (see appendix for dump sample analysis). Baseline groundwater quality is carefully observed at the Argo Tunnel by the US EPA and the CDPHE. A representative Argo Tunnel water sample was reported in Thomas R. Wildeman's Water Handbook for Metal Mining (attached as an appendix to this Exhibit C), page 4 and 10, Table I and Il: Page 4of8