GENERAL32961

• Permit No: M1999002
• IBM Index Class Name: General Documents
• Doc Date: 8/18/1998
• Doc Name: COMMERCIAL MINE PLAN SUBMITTED TO BLM SECTION 7
• Media Type: D
• Archive: No

• Transmissivity of the alluvial aquifers varies between 2,700 and 20,000 square feet
per day, depending on the saturated thickness.b The storage coefficient averages
0.20 (Weeks et al. 1974).'
7.4.2.2 Upper Aquifer
The Upper Aquifer is generally defined as the saturated zone that includes the lower
portion of the Uinta Formation (Figure 7-12) and the upper 100 to 300 feet of the
Parachute Creek Member of the Green River Formation down to the top of the
Mahogany Zone (Figure 7-13). The total saturated thickness of the Upper Aquifer at
the Piceance Site is not known. However, based on previous drilling projects in the
immediate area, the saturated thickness is expected to be approximately 300 feet.
The water in the Upper Aquifer is confined mainly to joints, faults, solution
cavities, and fractures, and the principal hydraulic conductivity is relatively small.
The permeability of the Upper Aquifer is much less than that of the Lower Aquifer.
Groundwater in the Uinta portion of the Upper Aquifer occurs in both confined and
unconfined conditions. The Uinta Formation is predominantly acoarse- to fine-
grained, poorly sorted, silty sandstone with interstratified layers of siltstone and
marlstones. Primary porosity of the Uinta portion of the aquifer has been greatly
reduced by post-depositional cementation. The Uinta Formation is more permeable
than the Mahogany Zone but less permeable than the Lower Aquifer.
• The potentiometric surface of the Upper Aquifer is located in the lower portion of
the Uinta Formation at the Piceance Site. Groundwater flow in the Upper Aquifer
below the Piceance Site is about North 39 degrees East (Daub 1996).
Transmissivity values from aquifer pump tests across various stratigraphic horizons
of the Upper Aquifer vary widely depending on location, lithologic conditions, and
rock quality encountered. Transmissivity values have ranged from 4 to 2,600 square
feet per day at several locations near the Piceance Site.
Based on the available existing data, the storage coefficient of the Upper Aquifer is
estimated to be on the order of 10' (Weeks et al. 1974). Data from a pump test
conducted on the adjacent lease property to the west of the Piceance Site indicated a
preliminary storage coefficient of 2.3x10"'.
Wells completed in the Uinta Formation yield as much as 300 gpm, although yields
of less than 100 gpm are more common (Weeks et al. 1974). Tests of the Upper
The term transmissivity describes the Elow characteristics of an aquifer. Transmissivity is the
average permeability multiplied by the saturated thickness of the aquifer. It represents the
flow through a vertical strip of aquifer one unit wide.
' The storage coefficient is defined as the volume of water released Erom or taken into storage per
• unit surface area of the aquifer per unit change in the component of hydraulic head normal to
that surface. It is expressed as a ratio and is dimensionless. It may also be referred to as
specific yield, effective porosity, storativity, or coefficient of storage.
American Soda, L.L.P. 7_19
Commeraal Mine Plan
August 18, 1998