2018-09-04_PERMIT FILE - C1980007 ‎(18)‎

• Permit No: C1980007
• IBM Index Class Name: Permit File
• Doc Date: 9/4/2018
• Section_Exhibit Name: Exhibit 19E Sunset Trail Lease Modifications 2011 Hydrology Survey
• Media Type: D
• Archive: No

.1 MCC West Elk Mine Sunset Trail Lease Modifications 2011 Hydrology Survey 13
3.3.3 Wetland Areas
As noted previously, wetland surveys and delineations were beyond the scope of work for
this study, but several relatively large wetland areas were encountered in the surveys. They
occurred at relatively high elevations ranging from 8,824 to 9,561 feet amsl and ranged in size
from about 7,500 to 15,840 ft2 (0.2 to 0.4 acres).
3.4 Horse Creek Drainage
The Horse Creek drainage encompasses an area of about 1.62 square miles (1,038
acres). The drainage ranges from about 9,600 to 7,840 feet ams] with an overall average gradient
of 978 feet per mile. Approximately 0.43 square miles (-273 acres) lies in the STLM study area
(Figure 2). Horse Creek was flowing at an estimated 20 gpm at the edge of the lease boundary
on October 21, 2011.
Data collected at the various survey sites in the STLM study area in the Horse Creek
drainage are summarized in Table 4 and Appendix D. Twelve sites were identified in this area
during the survey (Figure 2) including 9 springs or spring complexes with ponds and wetlands
and 3 ponds/ ponds with associated wetland areas.
3.4.1 Springs and Seeps
The locations of the Horse Creek spring and seep sites are depicted on Figure 2. The
elevations for the 9 springs and seeps or springs with ponds and/or wetlands mapped ranged
from 8,742 to 9,693 feet amsl. Average flows ranged from no flow (seep) to 4.6 gpm. Three of
the ten springs in this drainage had flows greater than 1 gpm. The spring at site 23 had the
highest average flow in this drainage, 4.6 gpm. The field pH was near neutral, ranging from 7.02
to 7.67 s.u., electrical conductivity ranged from 95.4 to 615 µS/cm; and temperatures ranged
from 4.7 to 14.6° C (Table 4).
3.4.2 Ponds
The locations of the three pond related features identified in the Horse Creek drainage are
depicted on Figure 2. The pond elevations ranged from 8,825 to 9456 feet amsi. Ponds at sites
24 and 61 are relatively large and site 61 had outflows of 1-2 gpm. The field parameters
included temperatures ranging from 10.6 to 17.5° C, pH values ranging from 6.36 to 6.79, and
electrical conductivity values ranging from 66.9 to 434 µS/cm.
February 2012 HydroGeo, Inc.