APPCOR11820

• Permit No: C1981034
• IBM Index Class Name: Application Correspondence
• Doc Date: 10/8/1982
• Doc Name: GRAND MESA GROUND WATER FINDINGS
• From: MLR
• To: DAN MATHEWS
• Media Type: D
• Archive: No

a.
• '2- •
The D coal seam is the lowest aquifer which will be disturbed by the
proposed mining operation. The aquifer subcrops into the glacial/
alluvial aquifer and continues, at a dip of So-6o, deep into the
Pic eance Basin. Monitoring well-water-level data indicate that ground
water in the aquifer flows up-dip and discharges into the overlying
glacial/alluvial aquifer, Recharge, probably occurs around the rim of
the Piceance Basin where the aquifer outcrops. Permeability in the coal
seam is mainly the result of post-depositional fracturing and cleating.
The app~icant has determined that the transmissivity-p~f the aquifer is
16.7 ft /day and the storage coefficient is 4.4 x 10 These values
indicate that the aquifer is confined and has low permeability. The
D seam aquifer contains a sodium bicarbonate type water with total
dissolved solids (TDS) concentrations ranging from 1,184 mg/1 to
2,308 mg/1. Because of the aquifer's Iow permeability and poor water
quality, it is not suitable for large scale development.
Situated about 130 feet above the D coal seam is the E coal seam aquifer.
This coal seam is currently being mined at the Grand Mesa operation.
Like the D seam, the aquifer subcrops into the glacial/alluvial material
and continues deep into the Piceance Basin at din of 5°-60. Recharge,
flow, and discharge conditions are also similar to those encountered in
the D seam aquifer, The transmissivity of the aquifer was determined
to be 1.5 ft /day. The E seam aquifer is also unconfined and has a low
permeability. The operator currently pumps about 25 gallons (per minute)
of water from the E seam mine workings. The sources of these inflows are
discussed in the addendum (Kimball, et al ., 1982) and shown on Map 6.
Ground water in the aquifer is a sodium bicarbonate type with TDS
concentrations ranging from 1,292 mg/1 to 1,354 mg/1. Because of the
observed low permeabilities and poor water quality, large-scale development
of the aquifer has not occurred.
The glacial/alluvial aquifer is one of the most important water sources
in the mine area. The aquifer mantles about 2/3 of the surface in the
mine arm to depths of over 200 feet, Recharge probably occurs through
adjacent bedrock aquifer discharges, influent leakage from stream flow,
and vertical infiltration of precipitation aqd snow melt. The transmissivity
of the aquifeer was determined to be 1,885 ft /day. The storage coefficient
is 7.5 x 10 These values indicate that the aquifer is moderately
permeable and unconfined. Water contained in the aquifer is a calcium
bicarbonate type with TDS concentrations ranging from 260 mg/1 to 400 mg/1.
Because of the moderate permeability and good water quality characteristics,
the aquifer is used extensively near the mine for domestic, irrigation,
stock-watering, and industrial purposes.