2015-09-22_HYDROLOGY - M1983194

• Permit No: M1983194
• IBM Index Class Name: HYDROLOGY
• Doc Date: 9/22/2015
• Doc Name: Casing Separation in DS-4 Ground Water/ Subsurface Subsidence Monitoring Well
• From: Daub & Associates, Inc.
• To: DRMS
• Email Name: THM
• Media Type: D
• Archive: No

DAUB & ASSOCIATES, INC.
September 17, 2015
Division of Reclamation, Mining and Safety
Attn: Minerals Division
1313 Sherman Street, Room 215
Denver, CO 80203
1985'/2 SOUTH BROADWAY
GRAND JUNCTION, CO 81507-9649
[phone]
FAX [phone]
email: [e-mail]
www.daubandassociates.com
RECEIVED
v SEP 2- 2015
DIVISION OF RECLAMATION
MINING AND SAFETY
Re: Natural Soda LLC, Nahcolite Project Permit No. M-1983-194: Ca_ sing_
Separation in DS -4 Ground water/Subsurface Subsidence Monitoring Well
The DS -4 (101-1-C) well has been utilized as a subsurface subsidence monitor well
pursuant to the Natural Soda LLC (NS) Mine Plan, Environmental Monitoring Plan, and
EPA UIC permit and monitors the 10H and 11H sodium bicarbonate mining intervals, per
the NS Comprehensive Monitoring Plan (June 2010, Section 4.0). The DS -4 (10H -C) was
drilled and cored in May 2009 with a 6.75 in. bit to 2,031.6 ft. total depth (TD) below
ground surface (bgs). Well bore casing (4.5 in. J-55) was set from surface to 2,023.6 ft.
(top of the R-5 Zone) and cemented in place. A baseline GR/CCL log for the DS -4 was
obtained on July 12, 2009. In August 2009 a cast iron bridge plug was set in the casing at
1,952 ft. The casing was perforated between 1,877 and 1,917 ft. to complete the well as
both a Dissolution Surface Aquifer monitoring well and a subsurface subsidence
monitoring well.
Rocky Mountain Wireline Services (RMWS), out of Grand Junction, CO, ran a gamma
ray/casing collar locator log (GR/CCL) in the DS -4 (101-1-C) well on March 9, 2011. RMWS
ran the GR/CCL log from 1,914 ft. to surface. The logging tool was run at an average rate
of 78 ft./min. The RMWS log was compared to a baseline GR/CCL/Cement Bond log run
by Weatherford (WFD) on July 12, 2009. The baseline log was run prior to the start of
mining operations in the 10H and 11H mining intervals. The two log signatures were
compared in order to determine if there was any subsurface subsidence due to the
solution mining operations. Changes in the nature and/or depth of the natural gamma
ray signatures between the two logs may be used to determine the extent of subsidence,
if any. Likewise, changes in the position of a casing collar as identified on a CCL log may
be used to monitor the extent of casing slippage, as the casing string may fail along with,
or independent from, the rock strata.
The comparison of the two logs showed no evidence of subsurface subsidence within the
logged interval. Datum for all logs is ground level. The trace of the gamma ray log
signatures in both logs overlay each other very well, although minor differences in
signature amplitude can be seen throughout logged interval. These minor discrepancies
can be attributed to the difference between the logging tools used by the two companies
as well as differences in logging speed, possible changes in wellbore fluid density
SPECIALIZING IN PROFESSIONAL GEOLOGICAL, ENVIRONMENTAL, HYDROLOGICAL, GEOTECHNICAL AND PERMITTING SERVICES