1993-04-19_REVISION - C1981008

• Permit No: C1981008
• IBM Index Class Name: Revision
• Doc Date: 4/19/1993
• Doc Name: PROPOSED DECISION & FINDINGS OF COMPLIANCE FOR RN2
• Type & Sequence: RN2
• Media Type: D
• Archive: No

The topography is gently sloping with a few small ridges and shales . Most of
the land surrounding the permit area is agricultural and is used primarily for
irrigated and non-irrigated farmland which produces alfalfa and pasture
grasses . The New Horizon Mine 1 area has been reclaimed and therefore is
being returned to pastureland and/or wildlife habitat.
The mine is located within the southeast portion of the Colorado Plateau. The
region is characterized by broad, fairly smooth surfaced plateaus and mesas
with gently dipping slopes dissected by steep canyons . Surface elevations at
the New Horizon Mine 1 range from a high of 5,767 feet (MSL) in the northwest
part of the permit area to a low of slightly less than 5,672 feet on the
southeast part of the permit area along Tuttle Draw (see the attached Index
Map Figure 1 ) . Total topographic relief for the New Horizon 1 area is about
95 feet. Surface elevations at the New Horizon Mine 2 area range from a high
of 5,760 feet (MSL) in the northwest part to a low of 5,642 feet in the
southeast part along Calamity Draw for a total relief of about 110 feet.
Climate
The regional climate of the New Horizon area is typical of intermountain
regions . It is characterized by cold winters , hot summers , low rainfall , and
short growing seasons . The mine receives approximately 12 inches of
precipitation in an average year. The majority of the precipitation falls
between October and May.
Regional Geology
The New Horizon Mines are located near the axis of the Nucla Syncline
(San Miguel Syncline) , a shallow, broad synclinal fold running northwesterly
for 65 miles . No evidence of faults has been observed in drill holes at
New Horizon Mine 2 or at the New Horizon Mine 1 area. The Nucla Syncline is
10 to 15 miles southwest of the major regional geologic feature of the area,
the Uncompahgre uplift. The region lies in the Dolores River basin. The
mines are located two to four miles northeast of the San Miguel River. Gently
rolling terrain traverses the area and the mines occupy a predominantly
southwestern exposure.
The mines are located in the Nucla-Naturita coal field. The coal is found in
late Cretaceous sediments . The youngest Cretaceous rocks in the area consist
of Mancos shale , a dark grey marine shale, present only on isolated hilltops
south of the town of Nucla. Two hundred feet of Dakota sandstone outcrops
extensively along the axis of the Nucla syncline. This formation consists of
a yellowish-gray, fissile sandstone and conglomeratic sandstone interbedded
with dark grey shale and coal . There are two coal seams within 100 feet of
the base of the Dakota (Figure 2) . The lower Cretaceous unit in the area, the
Burro Canyon Formation, is separated from the Dakota by an unconformity. The
Burro Canyon is comprised of white, grey and light brown sandstones and
conglomerates interbedded with green and purplish shales , siltstones ,
mudstones and thin beds of limestone. This formation has a maximum thickness
of 200 feet and outcrops on rims of canyons west and northwest of the mine .
This formation is difficult to differentiate from the Dakota in this area and
is commonly considered hydrogeologically similar. The Jurassic Morrison
Formation is composed of 250 feet to 600 feet of varicolored siltstones and
mudstones with beds of limestone and sandstone.
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