REV02407

• Permit No: C1984065
• IBM Index Class Name: Revision
• Doc Date: 10/1/1990
• Doc Name: PROPOSED DECISION & FINDINGS OF COMPLIANCE FOR PN 1 COAL RIDGE 1 MINE C-84-065
• Type & Sequence: PR1
• Media Type: D
• Archive: No

-18-
The alluvial bodies are not laterally continuous through the length of the
Colorado River, but are dissected by meanderings of the Colorado and by the
narrow flood plain of the Colorado River across the Grand Hogback Monocline.
The surface facilities of the Coal Ridge No. 1 Mine are east of the outcrop of
the Grand Hogback, and on the south side of the Colorado River. The alluvial
body present at the confluence of Harvey Gap and the Colorado River is on the
north side of the Colorado River and to the west of the Grand Hogback
outcrop. Therefore, these two alluvial bodies are not continuous. However,
due to the relationship between the waters of the alluvial bodies and the
Colorado River, there is a potential that impacts to the alluvium could be
cumulative between the mines.
Description and Hydrologic Impacts
of Mining at the Eastside Mine
The Eastside Mine is located in Garfield County, approximately 3.5 miles north
of the town of Silt. The proposed mine will affect 299 acres of non-federal
land during the life-of-mine. This underground mining operation involves 12
acres of surface disturbance with the surface facilities and roads.
The mine is located adjacent to the perennial-flowing Harvey Gap Drainage.
The Harvey Gap Drainage is a deeply incised north-south trending stream
valley, which cuts through the resistant sandstone of the Grand Hogback. The
nature of this drainage has been altered by construction of canals and a
reservoir for irrigation. The Grass Valley Reservoir is located 600 feet
upstream of the mine site on Harvey Gap Creek. The water in this reservoir is
impounded during high flow seasons from the headwaters of Harvey Gap and from
water diverted from the headwaters of East Rifle Creek through the Grass
Valley Canal. The impounded water is released from April 15 to October 15 to
irrigate almost 6000 acres of land in the Silt and Rifle area.
The Eastside Mine will be developed in coals of the Iles and William Fork
Formations of the Mesa Verde Graup. This 5-year permit is for mining in the
E-Seam of the Iles Formation. This seam is approximately 20 feet thick and
dips 59° on the average to the south. Coal will be mined by continuous miner
or conventional section with 200,000 tons per year projected as maximum
production. The life-of-mine plan includes recovery of the Wheeler seams of
the Williams Fork Formation, which are separated from the E-Seam by 200 feet
of strata characterized as predominately marine shales.
The probable hydrologic consequences of mining at the Eastside Mine have been
previously detailed in the Proposed Decision and Findings of Compliance for
the Eastside Mine issued December 14, 1984, and on file at the Division. A
summary of the projected impacts as detailed in this study follow.
Three domestic wells were found to have been completed in the shallow bedrock
aquifers of the area of the Eastside Mine. It was projected that mining at
the Eastside Mine would not affect these wells because of the extreme dip of
bedrock in the area and because of separation of the producing aquifers of
these wells from the mined seams at the Eastside Mine by 200 feet or more of
shale units.