HYDRO30213

• Permit No: M1999002
• IBM Index Class Name: Hydrology
• Doc Date: 2/10/2000
• Doc Name: UIC INFO
• Media Type: D
• Archive: No

by the various regulatory agencies that American Soda should prepaze a more comprehensive
ground-water monitoring plan. These concems are also discussed in Comments 4, 5, and 6. As
indicated in Comment 6, the Apri122, 1999 Water Monitoring Plan, was developed in
consultation with the EPA,, CDMG, BLM, USGS, and Rio Blanco County. It stipulated the
collection and analysis of 5 quarters of ground water and surface water baseline data prior to the
commencement of commercial operations. The revised Water Monitoring Plan, however, calls
for, at least, five quarters of monitoring. There will be approximately 25 ground-water
completions for the 0-5 yeaz mining panel alone. Four subsurface water-bearing zones will be
monitored at up-gradient, cross-gradient, and down-gradient locations. The Yankee Gulch Water
Monitoring Plan has been incorporated into the Permit. EPA believes that these additional
baseline data will provide a detailed and accurate representation ofsite-specific ground water and
surface water. This information will be reviewed prior to startup and during commercial
operations to determine if additional wells aze needed or if problems related to the mining process
aze occurring. EPA believes that the baseline data will be adequate for comparative purposes
during commercial operations.
The fact that the extent of USDWs may or may not be thoroughly defined at this time or
may be variable across the site does not affect the Permit requirements for construction or
operation of the design of the in-situ solution mining wells covered by this Permit. The Permit
precludes injection of mining fluids into either the Upper Aquifer or the Lower aquifer. The
operator is required to maintain at least a 150-foot buffer between the top of the solution mining
cavity and the base of the Lower aquifer (Dissolution Surface). The operator is required to
maintain a gas cap in each cavity to control vertical growth of the cavity in addition to and
instrumentation on each well to detect abnormal operating conditions that could be indicative of a
cavity leak. The operator must demonstrate that each injection well has mechanical integrity at all
times. This will be accomplished by a combination of logging (cement bond and temperature
logging) and well head monitoring. If mechanical integrity is lost, the Permit requires that the
well be shut-in and corrective measures be undertaken as specified by the permit and the Water
Monitoring Plan.
EPA believes, based on both regional and site-specific data, that the upper portion of the
Upper Aquifer (the Umta Formation) is a potential USDW and the base of the Lower Aquifer
(near the Dissolution Surface) is not a potential USDW. The review of regional data and public
comment have raised concems regazding the status of the upper portion of the Lower Aquifer and
the lower portion of the Upper Aquifer. These issues will be further evaluated during the
collection of additional baseline data. As stated previously, however, EPA does not believe that
the presence of a USDW in either aquifer at the site would change the Permit requirements for the
Yankee Gulch facility.
As a result of the review of this comment and the associated information, EPA has
determined that no changes to the Permit are needed in response to this specific concern.
Comment 16: It is the desire of Rio Blanco County that this project be designed and oQerated
to minimize potential negative impacts and that all decisions by PemrittinQ agencies be based on
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