2009-08-06_REVISION - C1982056

• Permit No: C1982056
• IBM Index Class Name: REVISION
• Doc Date: 8/6/2009
• Doc Name: Preliminary Adequacy Review ‎(Memo)‎
• From: Marcia Talvitie
• To: Janet Binns
• Type & Sequence: TR67
• Email Name: JHB
• Media Type: D
• Archive: No

C-1982-056 TR-67
PAR - MLT
06-Aug-2009
Page 2 of 3
paragraph on page 2.05-97.4 makes mention of the Construction Certification and
Quarterly Refuse Pile Inspection Reports, but does not incorporate the specific details
contained within the NWCC report.
Please provide language in the permit which confirms that the Inspection and Testing
program recommended in the NWCC Geotech report will, in fact, be utilized during
construction of the expanded CRDA and that all pertinent requirements of Sections
4.10.2 and 4.09.1(11) will be met.
4.10.3 - Water Control Measures
Subdrainage systems are required and provided-to intercept all ground water sources and
to protect groundwater from infiltration of surface water or leachate from coal mine
waste banks. The test holes drilled and test pits dug by NWCC indicate that groundwater
is not likely to be present near the surface of the reclaimed spoil which comprises the
foundation of the proposed CRDA expansion. Given that there will be no groundwater to
capture and protect, TCC instead proposes to construct an underdrain along the base of
the CRDA. The purpose of the underdrain will be to hasten the removal of any water that
does enter the coal refuse material (storm water, snowmelt, and water draining from the
coal processing waste). All water discharged from the CRDA and from the proposed
underdrain system will be routed to Sediment Pond D. Pond D discharges will continue
to be subject to applicable effluent standards.
Rule 4.10.3(5) allows utilization of an alternative subdrainage system, "after approval by
the Division upon a thorough analytical demonstration that such an alternative will ensure
the applicable static safety factor, stability of the fill and protection of the surface and
groundwater in accordance with the requirements of these Rules." Though the
application does not clearly state as much, the Division understands that such approval is
being requested for the proposed underdrain design. The clear intent of 4.10.3 is to
ensure that groundwater beneath a coal mine waste bank is kept separate from all water
that has been in contact with coal mine waste.
It is the Division's determination that the CRDA underdrain proposed by this revision
accomplishes the intent of the rule. The presence of the underdrain, as designed, will
ensure that the applicable safetyfactor of 1.5 will continue to be achieved, will serve to
increase the stability of the fill by preventing any significant build-up of hydrostatic
pressure within the pile, and will protect the surface and groundwater in accordance
with the requirements of the Rules.
Contour lines (existing) shown on the Phase I Grading Plan (Sheet No. C-102) reveal
the presence of a topographic flow path beginning approximately 500 feet ESE from
the coal stockpile tube and running perhaps 800 feet SSE to intercept the Phase I
Underdrain. No underdrain has been proposed to occupy this flow path. Please
incorporate an additional underdrain at this location, or provide sufficient justification
which explains why such an underdrain should not be required.
4.10.4 - Construction Requirements
4.10.4(2) requires coal mine waste banks to have a minimum static safety factor [FS] of
1.5. The NWCC report identifies the northern benched slope, which will be the steepest