2016-12-01_PERMIT FILE - C1980007 ‎(6)‎

• Permit No: C1980007
• IBM Index Class Name: Permit File
• Doc Date: 12/1/2016
• Doc Name: Hydrologic Characterization of the South of the Divide
• Section_Exhibit Name: Exhibit 71
• Media Type: D
• Archive: No

2016 Recommended Modifications to the West Elk Mine Hydrologic Monitoring Network 41
3.2.2 Upper Raven Gulch
Raven Gulch is a perennial stream that drains the West Flatiron mine panel area and is tributary
to the North Fork. The Upper Raven Gulch monitoring site was established in 2005 and is
located upstream from the confluence with the West Flatiron drainage (Map 1). The site is about
0.75 miles east of the end of B -Seam Panel 18, which was mined in February 2008.
Hydrologic monitoring at the Upper Raven Gulch monitoring station began in 2005. It should be
noted that CDRMS (2005) approved baseline monitoring for the Raven Gulch surface water sites
to be the same as routine monitoring (3 times per year and one low flow water quality sample).
Flow in Upper Raven Gulch is perennial, but diminishes significantly in the late summer months.
A time -series flow graph for Upper Raven Gulch is shown on Figure 32.
rtgure -i z. riow to upper xaven uuicn
Upper Raven Gulch
160
140 _.__..._.. _...
120 ___
3
0
w 100
E
go
u
b
N
d
J
cA
C 60
40 - — --
20
vt t0 1� W a, O .-1 N M O ✓1
O O O O O 1- 11 H N N N H
C C C C C C C C C C C C
10 IO 10 f0 A 10 16 f0 10 f0 f0 10
Date
Time -series water quality data from Upper Raven Gulch do not indicate any adverse trends in
water quality. The baseline laboratory water quality values are very limited (recorded in May and
June 2005 only) (HydroGeo, 2016b). The laboratory ECs for this stream for the period of record
are variable, ranging from 133 to 311 µmhos/cm and averaging 193 µmhos/cm. In comparison,
the baseline laboratory EC values range from 133 to 165 µmhos/cm. TDS values for this stream
for the period of record are somewhat variable, ranging from 100 to 180 mg/L, and averaging
130 mg/L, compared to baseline values ranging from 100 to 110 mg/L. The baseline field pH
values are also limited (recorded in May, June and September 2005 only) (HydroGeo, 2016b).
The field pH values for this stream over the period of record are variable, ranging from 6.96 to
8.77 s.u., and averaging 8.26 s.u., compared to baseline field pH values ranging from 7.27 to
8.29 s.u. TSS values for this stream for the period of record are variable, ranging from ND to
770 mg/L, compared to baseline values ranging from 234 to 354 mg/L. Dissolved iron values
August 2016 HydroGeo, Inc.