GENERAL56035

• Permit No: M1999002
• IBM Index Class Name: General Documents
• Doc Date: 3/12/2004
• Doc Name: Cavity Characterization and Stability of Large Diameter Cavities
• From: DMG
• To: File
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman St., Room 215 C O 1.0 RA D O
Denver, Colorado 80203 D I v t 5 t D N O F
Phone: [phone]VI 1 (~ &RA I. S
PAX: [phone] G E O 1. O G Y
n . ,r /~
////l///,`- 0.EC LAMATION•MINING
SAFETY•SCIENCE

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~
~~• ~ Bill Owens
Governor
DATE: V Mareh 12, 2004 r Russell George
Executive Director
TO: Erica Crosby R°naFd w. carczny
Division Director
Natural Resource Trustee
FROM: Allen Sorenson
S
C
RE: Cavity Characterization and Stability of Large Diameter
vibes, American Soda, LLP,
Yankee Gulch Sodium Minerals Project, Permit No. M-1999-002 /
On February 18, 2004, Carl Mount and I attended a meeting with American Soda, BLM, and EPA to
discuss characterization ofthe shape of the solution mine cavities. An attendee list from that meeting is
attached to this memorandum. Previous discussions of cavity characterization had centered on production
well 29-24 having the first cavity to undergo characterization. This is because for some time now well
29-24 has been on a growth track to be the first well to reach an estimated 200 feet diameter. However,
29-24 continues to be American Soda's best producing well even as it approaches 200 feet diameter, and
the company is understandably loath to suspend production from this well in order to characterize the
solution mined cavity. Also, American Soda believes that the 29-24 cavity can continue to be mined
successfully to at least 225 feet in diameter. Accordingly, American Soda is proposing to characterize the
we1128-21 cavity. We1128-21 is currently on standby and has an estimated cavity diameter of 159 feet.
Based on American Soda's proposal, DMG and the other agencies have the following issues to consider:
1. Is American Soda's proposal to use down hole seismic and partial cavity solution displacement
approvable? The consensus of the agencies during the Februazy 2004 meeting was to approve
these methods.
2. Is we1128-21 acceptable as the first tazget for cavity characterization? Yes.
3. Can American Soda continue to solution mine we1129-24 beyond a 200-foot cavity diameter?
(American Soda's proposal is to mine 29-24 to a 225-foot diameter, based on volumetrics, and
then conduct a cavity characterization). This issue is discussed below.
4. Is there any permitting to be required to act upon American Soda's proposals?
Review of the DMG American Soda permit file indicates that there is no permit restriction on the
maximum diameter for solution mined cavities. This is because during original permitting it was
assumed, based on results at the test mine facility and thermal-economic modeling, that even reaching 200
feet diameters in the cavities was unlikely. Now that American Soda has determined that for at least some
of the cavities, mining to beyond 200 feet diameter is desirable, the potential for adverse environmental
results must be evaluated. American Soda has provided a report prepared by Agapito Associates dated
June 17, 2003. This report concludes that the cavities can be mined to diameters significantly beyond 200
Office of Office of Colorado
Mined Land Reclamation Active and Inactive Mines Geological Survey