2011-08-15_REVISION - M1990057 ‎(4)‎

• Permit No: M1990057
• IBM Index Class Name: REVISION
• Doc Date: 8/15/2011
• Doc Name: Adequacy Review
• From: DRMS
• To: Union Milling Company, LLC
• Type & Sequence: TR3
• Email Name: MAC
• Email Name: AJW
• Media Type: D
• Archive: No

Letter to Mr. Elder 2 August 15, 2011
TR -03 Adequacy Review File No. M- 1990 -057
5. Please provide the Division with a Quality Assurance /Quality Control (QA/QC) Plan for
construction of the TSF. The QA/QC Plan should address field compaction testing of the clay
under liner; a single compaction test should be performed for every 2,500 cubic yards of
placed material. In addition, the QA/QC Plan should address pressure testing and destructive
testing of the Polypropylene Geomembrane liner seams. A minimum of two destructive tests
should be performed on the liner.
6. Please provide the Division with the anticipated total maximum load on the TSF.
7. The TSF design plan calls for installing a leak detection system. The Division requires
additional design details order to evaluate the effectiveness of the proposed leak detection
system. Will the leak detection system utilize a mat or trenches to collect leachate? What is
the volume of the collection system? Will the collected leachate be returned to the mill?
Please specify how the Operator will determine if there is a leak in the Polypropylene
Geomembrane. In addition, locate the collection system on Exhibit TSF -02.
8. The Applicant has stated that following the construction of Phase 1 TSF, the historic tailings
will be placed back into Phase 1 TSF. Please describe how the tailings will be placed back
into Phase 1 TSF and describe what measures will be taken to ensure the embankment and
liner are not compromised during replacement of the historic tailings.
9. The Applicant has stated the impoundment liner will be held in place with material from the
ore stockpiles. What is the source of the ore material? The Division is concerned the 45 mil.
liner may be compromised by placing material with sharp edges on top of it. The Division
suggests placing a soil or sand cover over the liner before placing material from the ore
stockpile. Will the ore material remain in the TSF once it is placed there? Please describe
what measures will be taken to protect the liner from damage resulting from the placement of
ore material.
10. Please specify what the anticipated maximum hydrostatic head over the geomembrane will
be. In addition, specify how the Operator will monitor the hydrostatic head within the TSF.
The Division requires that the hydrostatic head not exceed two feet, please commit to
maintaining a hydrostatic head of less than two feet.
11. The Applicant has stated 4,500 yd of fill from the existing TSF OB stockpile. Please clarify
if this material was generated from the construction of the current TSF.
12. The Applicant has stated the existing on -site stockpiles will also be initial feed stock for the
mill startup. Please verify that the existing on -site stockpiles are the same ones identified
during the Division's inspection conducted on June 18, 2009.
13. In accordance with Rule 6.4.21(15) a detailed schedule for installation of the tailing
impoundment liner is required. The schedule is primarily needed for the Division to schedule
inspections of the construction. Rule 7.4.2(2) identifies activities which will require phased
construction inspections.