_REVISION - M1974052 ‎(13)‎

• Permit No: M1974052
• IBM Index Class Name: Revision
• Doc Name: JOINTLY SPONSORED RESEARCH PROPOSAL ASH BASED GROUT INJECTION FOR SUBSIDENCE CONTROL AT SHAMROCK MI
• Type & Sequence: TR1
• Media Type: D
• Archive: No

INTRODUCTION
The U. S. Environmental Protection Agency (EPA) in its report to Congress (March,
1999) noted that the use of coal combustion products (CCPs) in mine applications represented a
beneficial reuse option, but information is needed on the environmental impact of these reuse
options before it could make its regulatory determination. It is a well-known fact that CCPs have
been used extensively in mining applications for a number of years (see Reference Section). In
surface mining the ash has been used in producing stable fill areas, in haul road construction, and
in reclamation. Certain of the ashes have sufficient neutralization potential to make them useful
for acid mine drainage abatement. The CCPs have also been used in underground mines for a
number of applications, such as bulkhead construction, acid mine drainage abatement, and
subsidence control.
The U.S. Department of Energy (DOE) sponsored three major mining-related projects at
West Virginia University, Southern Illinois University and the University of Kentucky (Black and
Ziemkiewicz, 1998; Chugh and others, 1998; and Rob] and others, 1998, 1999). These projects
addressed the use of CCPs in underground mining operations. Although the mine conditions were
variable from dry mines to partially flooded mines, the demonstrations did not adequately define
the environmental impact of CCP use in these applications. In fact, the environmental benefit in
terms of acid mine drainage abatement through the use of CCPs has not been convincingly
demonstrated. The problem does not appear to be with the ash used to produce the grout, but
instead in the injection system and the ability to control grout flow and completeness of mine void
filling. It appears in the cases cited by Kim (1998, 1999) that the acid waters continue to bypass
the grout system. The majority of the mine injection projects involve the abatement of the acid
mine drainage. In the western U.S., the coals are the major aquifers for local water supply.
Information on those flooded mine applications involving the interaction of the grout materials
with the groundwater system is very limited.
In fact, the injection of grouts into underground voids is not allowed in all states.
Wyoming and North Dakota have programs that allow for the use of ash-based grouts
underground. Unfortunately, Colorado does not have such a program. As a result, ash-based
grout injection activities in Colorado and numerous other states require considerable
documentation and data on environmental impacts prior to being issued a permit. This situation is
even further complicated when the mine is fully flooded and sits in the regional groundwater
aquifer. Such is the case of the Shamrock Mine in Weld County, Colorado.
The Shamrock Mine is an abandoned underground mine that lies in the groundwater
aquifer and is flooded. The mine is a room and pillar operation with approximately 10-foot seam
height and the mine is approximately 100 feet below the surface and subsidence is a concern. A
grout injection system is being proposed for the Shamrock Mine that would be composed of ashes
from Public Service Co. (PSCo) of Colorado facilities and Shamrock Mine water. The proposed
grout injection system will involve pumping the grout into the mine on 25-foot spacing. The
displaced mine water would be used in the grout production and/or used for surface needs.
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