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 New Horizon Mine 1 produced coal from both the upper and lower Dakota coal
seams . The upper Dakota coal seam ranges in thickness from 1 .6 feet to
3.3 feet and is separated from the lower Dakota seam by 7 to 11 feet of
interbedded sandstone and shale. The lower Dakota seam varies in thickness
from 5.9 feet to 7.9 feet. The base of the lower Dakota coal is 83 feet above
the top of the Burro Canyon Formation. The coal dips 10 to 20 southwest
and strikes N 250W to N 450 W.
The New Horizon Mine 2 will primarily produce coal from the lower Dakota coal
seam and may utilize the upper Dakota coal seam during subsequent permit terms
if the seam is thick enough and of sufficient quality. The lower Dakota coal
seam at New Horizon Mine 2 ranges in thickness from 4.2 feet to 6.9 feet and
is 99 feet above the top of the Burro Canyon Formation. The coal dips
4.50 SW along a strike of N 450W.
Surface Water
The San Miguel River has its source in the San Juan Mountains . These
mountains are primarily composed of Tertiary volcanic rocks . Iorns
et. al . (1965a) has shown these waters to be of a calcium bicarbonate -
sulfate type during high flow periods . These waters contain less bicarbonate
during low flows while the calcium and sulfate concentrations increase due to
less dilution from snowmelt runoff. The San Miguel River traverses the
interior portions of a basin that is chiefly underlain by Dakota Sandstones ,
the Morrison Formation and Mancos Shales . The Morrison Formation and Mancos
Shale have the greatest potential for influencing the river water chemistry.
The San Miguel River drains an area of 1 ,080 square miles . In addition,
approximately 15,500 acres of irrigated land lies between Placerville and
Naturita, Colorado. It is estimated that 2 .8 tons of Total Dissolved Solids
(TDS) per acre are contributed to the waters annually from this area. This
results in increased levels of magnesium, potassium, sulfate and chloride.
Water quality samples taken from the San Miguel River at Naturita, Colorado,
have a weighted average of 316 milligrams per liter (mg/1 ) TDS. Specific
conductance varies between 318 and 730 millimhos (mmhos) . The mean sodium
adsorption ratio (SAR) is about 0.7 at Naturita. Water curves indicate that ,
90 percent of the time , flow in this river exceeds 60 cubic feet per second
(cfs) , while flows exceed 1000 cfs about 10 percent of the time. The mean
discharge of the river is 351 cfs . San Miguel River waters are suitable for
domestic usage except at low flow periods when sulfate levels are high.
The Colorado Cooperative Ditch Company diverts as much as 155 cfs of water
from the San Miguel River approximately ten miles east of the town of Nucla.
The main diversion ditch then flows westerly passing just north of the town of
Nucla and then flows northwestward passing north of the New Horizon Mine 1 .
Diversion ditches distribute water to mainly agricultural users in the area.
Additional uses include domestic , municipal and stock pond consumption.
The New Horizon Mine 1 is located downslope from the main ditch in the gently
sloped upland of Second Park. This is just north of Tuttle Draw and is
totally within its watershed. The New Horizon Mine 2 site is just west of the
town of Nucla and is located in the mildly sloping upland area immediately
north of Calamity Draw, approximately in the middle of First Park. The
above-mentioned parks consist of recent undifferentiated aeolian silts and
sands overlaying the Dakota and Burro Canyon Formations . Since the completion
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