GENERAL53961

• Permit No: M1984014
• IBM Index Class Name: General Documents
• Doc Date: 8/10/2006
• Doc Name: Supplemental Geology report
• From: Cotter Corporation
• To: DRMS
• Permit Index Doc Type: General Correspondence
• Media Type: D
• Archive: No

GeoScience Services 2263 Kingston Road
5 Grand Junctioi:, CO 81503
[phone]
Date: July 18, 2006
To: Glen Williams-Cotter Corporation, Nucla, Colorado
Re: The role of fractures in unsaturated transaort
The purpose of this letter is to discuss the role of fractures or faults in water and
contaminant transport in the unsaturated zone. The geology in the vicinity of the JD-6
and JD-8 mines is characterized by large rotational blocks along faults associated with
the Paradox valley. Since these faults underlie the waste-rock dumps for these mines, it
is important to understand the role of faults or fractures in the transport of potentially
contaminated water from the waste dumps.
Faults and fractures commonly exhibit higher intrinsic penneabilities than the
surrounding porous rock. Please note that the term intrinsic permeability is dependent
only on the characteristics of the medium and is independent of the fluid. Under
saturated conditions, faults and fractures act as preferential pathways that can result in the
rapid transport of groundwater. Under unsaturated conditions, however, the physics of
flow is significantly different as is the role of fractures and faults on water transport.
To understand these differences, it is important to understand the physics of flow in the
unsaturated zone. Water moves from high potential azeas to low potential areas in the
unsaturated zone. This would be analogous to water in the saturated zone moving from
areas of high pressure and/or high elevation to areas of low pressure and/or low elevation
as measured by hydraulic head. The total potential ('Y,) in the unsaturated zone is defined
by Equation (I);
~[ -gym ~"~z (1)
where (`I',n) is the matrix potential and (`Y~) is the gravitational potential. The matrix
potential is due to capillarity in the soil or rock while the gravitational potential is
dependent on the elevation of water in the soil. If the degree of saturation is constant in a
unifonn soil, then the matrix potential will be uniform and water will move downward
under the influence of gravity. Under field conditions, variations in the degree of
saturation and non-unifonn soils result in matrix potential differences that are important
in the movement of water in the unsaturated zone. Therefore, it is important to
understand the role of capillarity in the movement of water in the soil and fractures.