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2024-12-16_REVISION - M1977410 (2)
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2024-12-16_REVISION - M1977410 (2)
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Last modified
12/17/2024 10:20:14 AM
Creation date
12/17/2024 7:47:22 AM
Metadata
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Template:
DRMS Permit Index
Permit No
M1977410
IBM Index Class Name
Revision
Doc Date
12/16/2024
Doc Name Note
Table of Contents, Introduction Exhibit A Thru Exhibit U Appendix A Thru Appendix G
Doc Name
Request For Conversion
From
Grand Island Resources LLC
To
DRMS
Type & Sequence
CN1
Email Name
JPL
JLE
EL1
LJW
THM
Media Type
D
Archive
No
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Cross Gold Mine <br />December 2024 G-4 <br /> <br /> <br />public water supplies (Nederland, Boulder) rely on surface water sources (Weritz, 2015). Wells within 2- <br />miles of the site can be seen on Map C-2B. <br /> <br />The hydrology of alpine and subalpine basins in the Colorado Front Range has been a topic of <br />research since the 1920’s. Recent research using naturally occurring chemical tracers and groundwater <br />dating has refined the conceptual model for recharge, groundwater flow, and surface water <br />groundwater interaction (Frisbee et al., 2011). Hydrologic and climatic conditions cause most of the <br />precipitation to be released as spring and summer snowmelt which drains rapidly from the mountain <br />front and shallow aquifers to streams and wetlands over the course of months. The sudden emergence <br />through old workings that intersect the current underground mines suggests a direct pathway to some <br />runoff being funneled into old shafts during surface runoff. During runoff, it has been observed that <br />significant changes in Coon Tract Creek fill a wetland that sits atop the Cross Mine. Infiltration of <br />volumes of water occur almost as soon runoff occurs fractures leading from the Coon Tract Creek <br />channel and adjacent wetlands down into the Cross mine. Obviously, these pathways have a very high <br />transmissivity. This makes Coon Tract Creek a losing stream along its path above the Cross mine, with <br />overland flow occurring once the regolith and fracture pathways are saturated by the flow in the Creek. <br />Therefore, it can be assumed that if there is flow in the Creek, there is also flow into the Cross mine. <br />The sub-alpine hydrology conceptual model indicates that high elevation steep catchments recharge <br />due to weather or leaching near surface rock and overlying regolith. Ground water flow returns to the <br />surface, some in the form of springs and artesian wells and the apparent gaining in surface waters to <br />topographically-driven-flow. This reemergence as surface water happens because of topography- <br />driven- flow and hydraulic conductivity contrasts with depth (Frisbee et al., 2013; Bukoski et al., 2021; <br />Foks et al., 2017; Tóth, 1963). The time between snowmelt and discharge to streams can be highly <br />variable depending on path, but the steady-state mass balance is nearly complete within sub-alpine <br />basins. Because of the complete discharge to streams and springs, changes in groundwater quality are <br />detectable in surface water quality in sub-alpine basins such as Coon Track Creek. <br />Groundwater flow at the facility is generally to the south-east, following topography and the track of <br />Coon Track Creek. Water table maps for late July 2021 and late March 2022 are presented as Maps 3 <br />and 4 of Appendix G-4. The water table maps were created by hand-contouring linear interpolations <br />between water level measurements made at the three wells (Appendix G-4, Table 1) and the water <br />level in the Cross Winze. Conceptual water table contour cross sections were drawn from these maps, <br />where the surface projections of the cross section lines are presented in Appendix G-4, Map 5 and <br />cross-section of the conceptual groundwater table are presented in Appendix G-4, Figure 1, at both <br />natural (July 2021) dewatered conditions at the Cross winze (March 2022); dewatered conditions come <br />about due to dewatering related to pumping from the lower levels of the Cross mine. Non-pumping <br />conditions for the Cross Winze (water table at the collar of the winze) was assumed. <br /> <br />Groundwater flow at the Cross Gold Mine is controlled by faults, fractures, and jointing. The primary <br />porosity of un-weathered igneous and metamorphic crystalline rock is generally too low to meaningfully
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