2011-09-16_REVISION - M1990057 ‎(9)‎

• Permit No: M1990057
• IBM Index Class Name: REVISION
• Doc Date: 9/16/2011
• Doc Name: Adequacy Review
• From: The Union Milling Company
• To: DRMS
• Type & Sequence: TR3
• Email Name: MAC
• Media Type: D
• Archive: No

CDRMS question
2. Please depict the location of the temporary clay pad on Exhibit TSF 01.
UMC Response
The temporary clay pad, for the temporary storage of the historic tails and magnetite during construction
of the TSF, will require an area approximately 30ft by 250ft for a 5ft high storage pile, with 3:1 slopes.
This storage area is within the disturbed area, on the reconstructed south road. The pile will be between
the new concentrate storage room and the old septic tank, allowing minimal 8 -l0ft wide access to the
lower portion of the mill on the north side of the road during material storage. The storage pad is shown
on TSF 02.
CDRMS question
3. Please provide the Division with a plan for sub -grade pre aration o the tailin • s stora • e acili
(TSF) site. The Division requires this information to ensure the sub -grade is adequately
prepared in order to reduce the potential for liner failure.
UMC Response
The sub -grade preparation for the TSF is as follows.
1. Clear cut/log trees. Clear and grub organic matter including tree roots, pine needles, dead wood
and other deleterious materials.
2. Clear topsoil and place in topsoil stockpile for reclamation.
3. Cut and fill to design specifications using contractor selected equipment. Equipment can include
track dozer(s), backhoe(s), scraper(s), front end loader(s), road grader(s), sheep foot
compactor(s), or excavator(s).
4. Fill material will have top size of 6in and contain 50% silt and clay.
5. Fill will be placed in 10 -12in level lifts and compacted by a self - propelled sheep foot roller.
6. Fill will be placed at 95% of Standard Proctor dry density (ASTM D 698).
7. Fill will be scarified between lifts.
8. Fill will be moisture conditioned to within 2% of optimum.
9. Construction engineer will be on site to provide testing during fill placement.
10. Verify compaction of floor of pond by number of tests recommended by CTL Thompson.
11. Install 12in of 1 x 10 -6 cm/sec clay liner. Clay liner will be installed in two lifts, 6in each. Clay
will be compaction tested at one test per 2,500cy clay placed.
12. Install geomembrane wick drain leak detection grid within top layer of clay capable of
intercepting liquid within the leak detection zone and conveying the liquid to a collection sump
for storage.
13. Install leak collection sump and piping in pond corner and connect geomembrane wick drain leak
detection grid to the sump.
14. Lining contractor to install 45 mil reinforced Polypropylene.
15. Liner will be tested at intervals specified by manufacturer and contractor but not less than two
tests will be performed.
16. Materials or construction not meeting standards and design specifications will be removed and
repaired.
M1990 -057 September 16, 2011