2010-04-16_PERMIT FILE - C1996083A ‎(11)‎

• Permit No: C1996083A
• IBM Index Class Name: Permit File
• Doc Date: 4/16/2010
• Section_Exhibit Name: 2.04 Information on Environmental Resources
• Media Type: D
• Archive: Yes

2.04.7 Hydrology Description
These wells range from 14 feet to 77 feet deep and typically produce water from 12
feet. The well yield ranges from 5 gpm to 120 gpm with average yields of
approximately 17 gpm. Water quality is highly variable within the alluvial fill. Most
wells completed near the river sustain quality adequate for human consumption;
however, the higher sulfate and total dissolved solids values are probably a function
of return irrigation flows and well completion depths near the alluvium - Mancos shale
contact.
Localized Alluvium - Colluvium
Localized deposits of alluvium - colluvial material reworked by fluvial processes are
present within the area, primarily within the Hubbard Creek, and Terror Creek
drainages. Hydrologic testing in similar material performed by Colorado
Westmoreland Inc. (CWI) during development of their Steven's Gulch well field
showed that yields from these sources are moderate (27 gpm at Steven's Gulch well
field), with transmissivity values ranging from 187 to 230 sq. ft. per day, and storage
coefficient of 0.0002. Water from wells penetrating this lithotype are classified as
sodium bicarbonate (Brooks, 1983). Recharge is accomplished from precipitation
and run -off, and water is discharged from seeps or springs. Although similar in
some respects, these areas do not fulfill the requirements of being Alluvial Valley
Floor areas.
Several years of water table monitoring in the CINI wells installed in the Steven's
Gulch indicated the water level in this aquifer is below the local streambed for most
• of the year, and therefore the streams are recharging the aquifer.
The areas of the colluvial- alluvial sediments in Hubbard Creek and Terror Creek lie
below the coal seam to be mined. Protection of these sediments is provided by
limited extraction zones under the Creeks and assuring the projected extent of
subsidence is 100 -feet from the centerline of the Creeks.
Mesaverde Formation - Perched Groundwater
All of the mines in the region report a similar experience as that observed at the
Bowie No. 2 Mine. The Mesaverde formation does not contain extensive aquifers.
Typically, the formation is dry or the rock units are of such low permeability they yield
insufficient water for sustained use. Even the Extensive Rollins Sandstone, the
recognized aquifer in the region, is highly cemented and a low producer.
Groundwater occurrences within the Mesaverde Formation have been interpreted
from monitoring holes and logs run during the exploration drilling process (refer to
Geology Map 07). From the monitoring holes, water quality samples were obtained
and static water levels or potentiometric elevation data were noted. In addition, file
research was done on the logs of the exploration drill holes to detect static water
levels noted during drilling or logging. From the available information, two saturated
horizons within the Mesaverde Formation, above the Rollins Sandstone, were
interpreted. Both are characterized as locally discontinuous saturated strata
occurring as perched horizons. One is stratigraphically between the Rollins
Sandstone member and the "C" coal seam, typically 200 ft. below the "D" coal seam
(refer to the potentiometric surface presented on Map 11, Lower Perched Water
• Zone). The other, is located above the "D" coal seam (refer to the potentiometric
surface presented on Map 10
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