2010-12-17_REVISION - C1981019 ‎(153)‎

• Permit No: C1981019
• IBM Index Class Name: REVISION
• Doc Date: 12/17/2010
• Doc Name: Exhibit 7 Item 21 Collom Project Pre-Feasibility Hdyrology Report
• Type & Sequence: PR3
• Email Name: JRS
• Media Type: D
• Archive: No

Meteorology 15
3.3 Precipitation
In general, precipitation occurs year- round, with a slight increase in the spring. During
the winter months, precipitation falls as snow, averaging approximately 70 inches per
year in Craig and Meeker. Determination of an average precipitation for the Collom site
is complicated by incomplete records and the fact that parts of Colorado have been in a
drought since 2000, with 2002 being one of the driest years on record. This would
suggest that the average annual precipitation totals, shown in Table 3.2 from all Colowyo
stations are generally lower than the long -term average.
Table 3.2 Precipitation data summary
Source - Location
Average
Annual
precip.
(in)
Period of
record
1998
total
(in)
1999
total
(in)
PRECIPITATION
2000 2001
total total
(in) (in)
2002
total
(in)
2003
total
(in)
Colowyo -SCN 16
15.64"
1998 -2003
16.90
14.68
5.71
11.94
11.02
19.02
Colowyo -WSTPT
14.64'
1998 -2003
16.08
14.00
6.66
10.32
13.83
15.44
Colowyo -SCN 34
13.25*
1998 -2003
14.62
14.50
13.38
11.05
10.91
12.72
Colowyo-
9.65*
1998 -2003
10.59
11.48
4.07
8.04
8.89
9.27
GOSSARD
WRCC-Craig
13.06 **
1948 -1976
N/A
N/A
N/A
N/A
N/A
N/A
C WRCC-Craig 4SW
16.66 **
1977 -2004
9.88
6.16
8.09
7.19
10.00
14.14
WRCC - Hamilton
18.77 **
1948 -2004
18.82
18.45
17.13
16.79
12.24
16.75
WRCC- Hayden
16.94 **
1948 -2004
15.91
18.10
17.73
14.37
13.38
19.30
WRCC - Maybell
11.86 **
1958 -2004
13.74
13.03
10.75
9.61
9.01
9.74
WRCC- Meeker
16.45 **
1900 -2004
18.15
15.77
14.33
14.66
10.72
15.08
* Average of only the bolded values
** Average of period of record
Colowyo stations SCN 16, SCN 34, and WSTPT are closest in elevation and location to
the proposed Collom Mine. The range of annual averages is 11.05 to 19.02 inches with
an average of 14.5 inches. However, as discussed above, average annual precipitation
totals recorded at these stations are likely lower than the long -term average.
Data from the local WRCC stations were used to evaluate the long -term, regional
precipitation. The most comparable WRCC stations (based on proximity and elevation)
are in Meeker (average annual precipitation of 16.45 inches) and Hamilton (average
annual precipitation of 18.77 inches). Based on these data, the average annual
precipitation at the Collom Mine should be approximately 17.5 inches. This number is
consistent with WRCC precipitation contour data for the State of Colorado (WRCC,
2005c). The average monthly precipitation at the Hamilton and Meeker stations is
shown on Figures 3.2 and 3.3.
Estimated precipitation amounts for a 24 -hour storm with return periods of 2, 5, 10, 25,
0 50, and 100 years are shown in Table 3.3 (NOAH, 1973).
2572 -R2 Colowyo Coal Company
Water Management Consultants