2020-12-15_HYDROLOGY - M1983194

• Permit No: M1983194
• IBM Index Class Name: Hydrology
• Doc Date: 12/15/2020
• Doc Name: Water Monitoring - Groundwater
• From: Daub & Associates, Inc.
• To: DRMS
• Email Name: ACY
• Media Type: D
• Archive: No

DAUB &ASSOCIATES, INC. 1985% SOUTH BROADWAY
GRAND JUNCTION, CO 81507-9649
[phone]
FAX[phone]
email: [e-mail]
www.daubandassociates.com
December 11, 2020
Re: Natural Soda LLC Nahcolite Project Permit No. M-1983-194 BG-S Well Condition Summary and Action
Plan
The BG-5 groundwater monitoring well (GMW) is exhibiting elevated chemistry values for total alkalinity,
conductivity,total dissolved solids, boron, potassium, and sodium. The BG-5 is a B-Groove (BG)Aquifer and
subsurface subsidence monitoring well (SSMW), and was a September 2009 completion of the 12H-C,which
was initially drilled as an exploratory core hole to the depth of 3,005 feet below ground level (BGL). The
BG-5 water chemistry is indicating possible communication with DS Aquifer fluids. There is increasing
evidence that dual purpose NS wells which were originally drilled as exploratory core holes and then
completed as GMWs may be more susceptible to being a conduit for higher conductivity DS Aquifer fluids to
migrate up through this conduit to a point where GMW sampling may be detecting these localized, higher
conductivity fluids rather than the actual BG Aquifer fluids (video logging in the BG-8 (plugged and
abandoned) and BG-9 tend to support this assertion). This dual use strategy of converting exploratory wells
to GMWs was done in an attempt to minimize environmental impacts by reducing the number of drilled
wells,well pads,and surface and subsurface disturbance.
A geo-chemistry departure in the BG-S began in late 2017 with a more significant departure noted in
November 2020 when conductivity values which had been in the 3,000 to 9,000 range subsequently
elevated to 15,000 micromhos. December laboratory results (pending) should be reviewed to determine if
the November conductivity value was aberrant. As stated previously, it is believed that fluids from the DS
Aquifer may be migrating up along a pathway which was created when the well was originally cored and
subsequently completed as an GMW. NS believes that this chemistry deviation is localized higher
conductivity water associated with a well-specific conduit and will dissipate when the conduit is blocked.
An investigation to determine the cause of this departure is planned for the near future and will include a
video inspection of the well bore/casing. Remediation strategies will be formulated following investigative
work. Following the video inspection of the well and implementation of appropriate remediation for the
well, NS will begin collecting weekly groundwater samples from the BG-5 to monitor the water chemistry
(including TDS, halite, carbonate, pH, and alkalinity) until the analyte levels begin to taper in the right
direction. If the elevated conductivity continues to lower, then the remediation performed to date will be
considered a success and monthly sampling will replace the weekly sampling and continue for a minimum of
6 months. If conductivity does not return to a more acceptable, historic level, then further remediation or
plug and abandonment will be considered.
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