GENERAL53077

• Permit No: C1981041
• IBM Index Class Name: General Documents
• Doc Date: 12/1/1982
• Doc Name: Proposed Decision and Findings of Compliance
• Permit Index Doc Type: FINDINGS
• Media Type: D
• Archive: No

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VI. Ground Water Hydrology (cont'd)
Three stratigraphic units can be defined•as.acjuifers and each transmits water to,
or is recharged by, the river. The first unit is the strata overlying the coal
seam. This unit consists of interbedded sandstones and shales of di~:continuous
lateral extent. Consequently, the stratigraphy indicates that the entire sequence
of strata overlying the coal zone in the permit area behaves as a single hydraulic
unit which contains only localized perched aquifers in areas where it is recharged
by the river. Cround water moves slowly through and between intercronnected sandstone
and shale lenses and beds.
The second aquifer is the Cameo coal seam. The coal seam receives recharge
water from the river where the seam dips below the river at an elevation of
4,750 feet, as evidenced from tie subsurface structural contour map in Exhibit 15.
The Rollins Sandstone formation is the thickest and most continuous sandstone in
the project area. The Rollins Sandstone is the third aquifer and
cronstitutes the best potential aquifer in the region. This unit is t:ypicaZly 119
feet thick in the permit area. As can be seen in Exhibit 13 of the sipplication,
the Rollins Sandstone underlies the entire permit area, except within Debeque
Canyon, where it has been eroded and presently outcrops. Recharge to the Rollins
Sandstone occurs primarily along the subcrop of the sandstone below t:he alluvium
of the Colorado River.
In addition to the three stratigraphic formations addressed, the a1lc~vial deposits
of the Colorado River flood plain can also be classified as an aquifer. The
alluvium contains water from the river and presumbly discharges watery to the
permeable units which subcrop beneath it.
The strata in the Roadside mine plan area dip toward the Colorado River, whereas
the strata in the Cameo mine plan area dip away from the Colorado River. Therefore,
ground water from the Roadside mine plan area discharges to the Colozado River,
whereas the Colorado River recharges the ground water system in the Cameo mine plan
area.
Presently, approximately 13 acre-feet of water is consumed annually within the
Roadside mine through evaporation and absorption. Upon closure of the Roadside
mine, ground water in the aquifers would resume its flow to the Co1oz•ado River.
Approximately 225 acre-feet of water is produced within the Cameo mine as inflows.
Some of this water is consumed within the Cameo mine by evaporation in ventiliation air
and absorption on the coal. The remaining water is pumped to the surface and
discharged. The source of this inflow water is the Colorado River. Upon the
closure of the Cameo mine, water will continue to flow fmm the CoIoz•ado River
until the entire underground workings are filled with water.
The applicant will have to submit evidence that adequate water will be obtained
to replace the water which is Iost from the Colorado River prior tv mine
closure. Until the mine closes down, there will be no problem with water balance,
since the water is pumped back into the river, and mine closure is not anticipated
until 1995 at the earliest.
Although it is evident that the Colorado River is the major source of water which
is discharged from the Cameo mine, the applicant has not supplied sut.'ficient
evidence to determine how much rnmes from dewatering the troal, perched water tables,