GENERAL52597

• Permit No: C1981019
• IBM Index Class Name: General Documents
• Doc Date: 7/10/1987
• Doc Name: Proposed Decision & Findings of Compliance for RN1
• Permit Index Doc Type: FINDINGS
• Media Type: D
• Archive: No

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Des cri nti on of the Environment
The mine site is located in an upland area at an average elevation of
7,300 feet. Land use in the permit and adjacent area is primarilu rangeland
and wildlife habitat. There is some dr_yland farming on level uplands,
and small areas of irrigated pasture and hauland along stream courses
in the general area. Rangeland on the permit area is characterized as good
condition sagebrush and mountain shrub range that, in the past, was variouslu
grazed by either sheep or cattle during the spring, summer, or fall. The
rangeland also supports substantial populations of mule deer, e17:, sage
grouse and numerous other wildlife species at various time throughout the
year.
The site lies just west of the northward flowing Good Spring Cree}:, which
is paralleled by Colorado Highwau 13. The area is a gently sloping upland
ranging from about 7,690 feet near the southc.~est corner, to 6,560 feet near
the northeast corner. Valleys that cut into the surface are generally narrow,
v-shaped, and about 250 to 500 feet deep with valley wall gradients of
9D to 100 percent. Forth of the proposed mine site, the topographic surface
is dominated by two ridgelines about two miles long, trending north-northeast,
bounded by Good Spring, Taylor and tJilson Creeks.
The permit area lies about six miles south of the axis of the Aria1 Basin
Anticline, a large west-northwesterly-trending fold. The aris of a parallel
subsidiary fold, the Collom Sun cline, trends southeasterlu throuah the
northeast part of the permit area. Bedding orientation generally has an
east-west strike and is characterized by dips from nearly horizontal to as
much as 20 degrees to the north. Overburden material consists o.` a mixture
of shales, claystones, siltstones, and sandstones.
Coal seams mined at Colowuo are in the Williams For}: Formation of the A!esa
i~erde Group. The L:~iiiiams Fork Formation consists o` alternating beds o`
sandstone, sandy shale, carbonaceous shal=, and coal. The geolocy section
o` the eermit application describes ten coal seamms in a 392 foot interval
of the formation which are recoverable bu surface mining tec.~.-u ques. The
Gdillia.ms For}: Formation has been estimated to be 16D0 feet tti.cY. in the
vicinity, and is underlain by the -idoe-forminc Trout Cree?: Sandstone member
of the _*sles Formation. Four lower coal b?ds in the [:'iliiars Fort: Formation,
which can be rm:ned only by underground methods, are described in the 1.'orthwest
Colorado En:ironmer.tal Statement, Site-Specific An alusis.
Bedroc}: ground water ~. Col oiryo occurs as isolated, perched ao ui fe rs in the
interbedded and lenticular sandstones and coals. Base f1 or: in the two oerenrial
streams in the general area is mainly ground water discharge from the
alluvial aquifers in the stream valleus. Stratigranhically, the Trout Creek
Sandstone is the first major, regional aouifer in the area. It is approximately
600 feet beneath the lowest coal seam to be mined. The principal recharge
for the aquifer is to the south of the permit area in the headwaters of
Taylor and Good Spring CreeY.s. There is no continuous, regional ground water
system on the permit area above the flood plain. o` Good Spring Cree}:. _Tnfo*-
mation contained in the permit aonlication and the ~:orthi;est Colorado EIS
indicates that, in test holes drilled by tr.,~. Grac= a;d Company and the USES,
no saturation was encountered in any o` the beds that are to be mined.