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Subject Protection of the Hydrologic
<br />System- Somerset Coal Mine
<br />• GENERAL DATA
<br />HYDROLOGIC SOILS
<br />CALCULATION NOTES
<br />By M. O. Anderson
<br />Checked
<br />Acct
<br />January 11
<br />Sheet No. 1 of
<br />19 1980
<br />4 Sheets
<br />The disturbed areas of the Somerset Coal Mine are located in three areas in the
<br />North Fork of the Gunnison River drainage area as follows:
<br />The main yard area is located in the mouth of Elk Creek Canyon, adjacent
<br />to the town of Somerset, in the South half of Section 8, T. 13 S., R. 90 W.,
<br />6 P.M., Gunnison County. The hydrologic soil for the S 1/2, Sec. 8, is
<br />Group B.
<br />2. The Bear Canyon ventilation facility and water tank is located about 4,500
<br />feet up Bear Canyon, from the mouth of the canyon, in the SW 1/4, Section 7,
<br />T. 13 S., R. 90 W., 6 P.M., in Gunnison County. The hydrologic soil for
<br />the SW 1/4, Sec. 7, is mostly Group B, with about 40 acres of Group C.
<br />3. The Hubbard Canyon ventilation facility is located about 1 1/2 miles up
<br />i Hubbard Canyon, from the mouth of the Canyon, in the SE 1/4 of Section 2,
<br />T. 13 S., R. 91 W., 6 P.M., in Delta County. The hydrologic soil for
<br />Section 2, T. 13 S., R. 91 W., is about 50 percent soil Group Band about
<br />50 percent soil Group C.
<br />.~~ The hydrologic soil groups for the three areas listed is from a letter from
<br />' ~ Mr. Clayton F. Spears, Soil Specialist for the S.C.S. in Grand Junction, Colorado.
<br />(attached).
<br />Hydrologic Soil Maps with Curve Numbers
<br />The hydrologic soil maps (see Reference materials, maps) with curve numbers (CN),
<br />AMC-II, were prepared by U.S. Steel. Western District Engineering personnel, using
<br />aerial photographs, camera photographs (both in cola) and the following tables from
<br />the S.C.S. National Engineering Handbook, Hydrology, Section 4.
<br />Table 9.1, for Pasture or Range, Meadows, Woods and Roads.
<br />Table 9.5, Ground Cover Density in percent for Herbaceous and Oak-Aspen.
<br />Table 9.6, Ground Cover Density in percent for Juniper-Grass and Sage-Grass.
<br />The hydrologic soil and curve number determinations were made after discussing
<br />the area soils with Mr. Tom Priest, State Soil Scientist, S.C.S., Denver, Coloradi ,
<br />Mr. Clayton F. Spears, Soil Specialist (S. C.S. (above letter reference) and Mr. Dean
<br />i Fisher, Area Conservationist, both of Grand Junction, Colorado, and using guidelines
<br />obtained in these discussions.
<br />RAINFALL
<br />10 year 24 hour storm = 1.90"
<br />25 year 24 hour storm = 2.30"
<br />. 100 year 6 hour storm - 1.90"
<br />Per Weather Bureau, Denver, Colorado for Latitude 107° 31'; Longitude 38° 56'
<br />February 1978, by Telecon.
<br />B-2
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