PERMFILE63708

• Permit No: C1980007
• IBM Index Class Name: Revision
• Doc Date: 12/2/2004
• Doc Name: 2.04.7‎(2)‎ Surface Water Information
• Type & Sequence: PR10
• Media Type: D
• Archive: No

West Elk Mine
. per yeaz on average, and during November, the probability of any mean daily flow falling below the
minimum is nearly 25 percent.
•
u
Estimates of peak flood flows for various recurrence intervals for the North Fork were provided
by the USGS using aLog-Peazson Type III distribution and Water Resources Council guidelines.
The estimates were based on historic streamflow data from the USGS gaging station on the
North Fork near Somerset. At the time of analysis, this station was located at the access bridge
to Bear Mine. Since the Paonia Reservoir Dam, located a few miles upstream from the gaging
station, was completed in 1961, the period of record from 1934 to 1960 only was used in the
analyses by the USGS. Estimated discharges for various recurrence intervals and the
probabilities of exceeding those estimated dischazges aze presented in Table 13 and shown
graphically in Exhibit 20.
Table 13
Flood Frequency Estimates for Various Recurrence Intervals
No Fork G nison River Near o erse Colorado
Exceedance Recurtence Interval= Expected Discharge
Probabili ears cubi feet/sec nd
.995 1 10
0.50 2 520
0.200 4 970
0.100 10 10
0 25 7 0 0

0. 20 50 7 40

.010 10 8 770
0.0 200 9 630
0.002 1 770
Notes:
1. Estimated using aLog-Pearson Type III Distribution by USGS using Water Resources Council Guidelines Period
of record 1934-1960.
2. R rt nce in rval = 1/ xce don r babili .
Baseline characterization of streamflow conditions for Minnesota Creek was developed from the
USGS/MCC Gage (09134000) 4.5 miles east of Paonia. Discharge volumes average 16,100
acre-feet per yeaz based on water years 1937 through 1947, and 1986 to 2000 monitoring records.
The annual mean dischazge is 22.2 cfs for the 41.3-miZ drainage basin. The lowest daily mean
flow was 1.0 cfs on November 14, 1936, and the lowest 7-day minimum was 1,4 cfs on January
16, 1990 and February 17, 1999. Flow at this site is influenced by two small reservoirs,
Minnesota Reservoir and Beaver Reservoir and atrans-basin diversion from the Coal Creek basin
(Little Gunnison Creek) into Minnesota Creek via Dry Fork.
2.04-97 Revised November 2004 PRIO