REV94610

• Permit No: M1983194
• IBM Index Class Name: Revision
• Doc Date: 5/15/1991
• Doc Name: AMENDMENT 2 FN M-83-194 ADEQUACY REVIEW
• From: MLRD
• To: NATEC MINERALS INC
• Type & Sequence: AM2
• Media Type: D
• Archive: No

MINED LAND RECLAMATION DIVISION
Department of Natural Resources
1313 Sherman St.. Room 215
Denver, CO 80203
303 866-3567
FAX: [phone]
STATE OF COLORADO
OF' CO(Q
~~' ?~
N~9 ~$
•{~ 8 ~'•
<<iur>~
~ /876 ~
Roy Romer,
Gavemor
Fred R. Banta,
Division Drtepor
DATE: April 22, 1991
T0: Gregg R. Squire
FROM: John T. Doerfer '.l r ri
RE: Hydrologic Adequacy Review, Amendment No. 2, Nahcolite Solution Mine,
NaTec Minerals, Inc., File No. M-83-194
I have reviewed the hydrologic aspects of the above-referenced permit
amendment. The proposa'I is to expand the permit area by 30 acres to a total
of 73 acres. The amendment consolidates previous information describing the
in-situ method of mining sodium bicarbonate using hot water dissolution. I
reviewed the mine plan, reclamation plan, water resources, and monitoring plan
and provide you the following comments:
1. The ground water monitoring plan states that the monitoring frequency
will increase to once per week if the effects from the mining operations
are recorded (page 37 ). In the Appendix under Item 1.2.7 of the BLM
requirements, leakage from cavities is defined as exceeding State of
Colorado Standards (Table 3-2, Final EIS) for total dissolved solids. A
review of this table in the EIS indicates a 25 percent increment above
855 mg1L for the upper aquifer and 2,210 mg1L for the lower aquifer, or
1,070 mg1L and 2,7fi~0 mg1L, respectively, as the standards. The use of
TDS as an indicator• of contamination may be appropriate, however, it also
may be difficult to distinguish between natural variability and man-made
effects due to mining. Have other indicators been considered? Please
confirm the criteria proposed to be used to determine the effects of
mining on ground water quality.
2. The ground water monitoring plan includes a network of up gradient and
downgradient monitoring wells, referred to as dedicated monitors, as well
as a number of wells within the area to mined. The Division is currently
in the process of developing proposed rules which will identify criteria
to be used in establishing appropriate "point of compliance" for ground
water standards. i'he discussion on page 8 states that the distance to
the two groups of wells is appropriate, in that wells closer could
potentially "miss" the effect and wells at a greater distance could
result in too long of a time between development of a problem and
detecti on of that p~robl em.
If you were to propose an appropriate "point of compliance" for ground
water from the proposed operation, which location would you choose? If
the more distant set of wells was selected, where would new wells be
located as the operation extends laterally?