2006-02-28_GENERAL DOCUMENTS - C1994082

• Permit No: C1994082
• IBM Index Class Name: General Documents
• Doc Date: 2/28/2006
• Doc Name: Proposed Decision & Findings of Compliance for PR2
• From: Change Mine Plan
• Permit Index Doc Type: Findings
• Media Type: D
• Archive: No

Sage Creek
Sage Creek is a perennial stream to the west of the proposed permit azea. Flows upstream from the
proposed permit area range from an average 0.7 cubic feet per second (cfs) in the spring to near 0 in
late summer and fall. Approximately two miles downstream from the permit azea, average flows of
1.5, 0.09, and 0.04 cfs were observed during baseline data collection in the spring, summer, and fall
respectively.
Water quality in Sage Creek vazies from upstream to downstream. Upstream from the permit azea, a
CaMgHCCO3 water type predominates. Total dissolved solids (TDS) typically range from 296 to
510 mg/1 at high and low flows, respectively. Downstream from the permit area, a CaMgSO4HCO3
water type predominates, and TDS typically ranges from 526 to 695 mg/l at high and low flows,
respectively.
Most of the flow in Sage Creek is diverted out of the stream for irrigation purposes prior to reaching
the site where downstream baseline data was collected. Sage Creek water is also used for livestock
watering.
Grassy Creek
Grassy Creek is a pen•enial stream to the east of the permit azea. Flow in Grassy Creek upstream
from the permit azea was perennial during baseline data collection. Mean flow rates in the spring,
summer and fall were 0.91, 0.10, and 0.06 cfs respectively. A CaMgSO4HCO3 water type
predominates upstream from the permit azea. TDS ranges from 680 to 853 mg/1 at high and low
flows, respectively.
Permit Area
Intermittent flows from the northern side of the permit azea drain through Armand Draw into
Scotchmans Gulch, and then into Grassy Creek. Spring flows in Armand Draw aze predominately
from the melting of snowpack. Late spring to eazly summer flows are a combination of bank storage,
runoff from precipitation events over saturated or frozen ground, or perched spring flow rechazged by
snowmelt. The remainder of the year, the channel exhibits ephemeral flow characteristics. The mean
flow rate in the spring is .056 cfs, and .02 cfs in the summer.
Within the permit azea, there aze five primary drainages, four of which aze ephemeral. The drainage
channels have been identified as Armand Draw, 011 Draw, Yl Draw, Y2 Draw, and Y3 Draw.
Armand Draw is intermittent. The drainage patterns exhibited in these draws are a combination of
pazallel and dendritic. The drainage densities are moderate (7.26 to 10.38 mi/mi2), channel
sinuosities aze low (1.01 to 1.07 mi/mi), and channel gradients aze moderate to steep (.039 to .218
ft/ft).
Yoast Mine 12 February 28, 2006