2011-09-09_APPLICATION CORRESPONDENCE - C2010089 ‎(2)‎

• Permit No: C2010089
• IBM Index Class Name: APPLICATION CORRESPONDENCE
• Doc Date: 9/9/2011
• Doc Name: Preliminary Adequacy Review No. 2
• From: DRMS
• To: Western Fuels Association, Inc
• Email Name: SB1
• Email Name: MLT
• Media Type: D
• Archive: No

C- 2010 -089 PAR No. 2
New Horizon North Mine
9- Sep -2011
Page 16 of 25
discharge elevation to contain the runoff from a 10 year -24 hour event and revise the
sediment pond design capacities in Table 2 accordingly.
DRMS: The Division has no further concerns. The May 26, 2011 submittal contained
Sedcad designs that demonstrate that the ponds have sufficient volume capacities. However,
the response to question number 12 -B of this section may require another review if the
elevations of the primary discharge pipes are raised.
10. Response accepted.
11. Response accepted.
12. On the fourth page of Appendix 2.05.3(3) -1, it is recommended that modifications to
sediment ponds NHN -001 and NHN -002 be used in order to avoid short circuiting. Please
revise the text to describe which modifications will be used, especially for pond NHN -002.
Also for pond NHN -002, please explain per Rule 4.05.6(7) why the spillway pipe could not
be located more towards the middle of the pond since it is now positioned very close to the
outlet of ditch NHN -002 North.
DRMS: The Division has no further concerns with this question. In the renamed Appendix
2.05.3(4) -1 of the May 26, 2011 submittal, WFC stated that the gated primary discharge
pond inlets would minimize short circuiting. WFC further explained that location constraints
prohibited redesigning the ponds. The Division, however, has additional questions
concerning sediment in the ponds.
a) In the last sentence of the 3 complete paragraph on page 4 of the Arcadis report in
Appendix 2.05.3(4) -1, the sediment storage elevations listed for the three sediment
ponds don't match the sediment storage elevations presented in Table 3 on page 5.
Please revise.
b) Referring to Table 3 of the Arcadis report in Appendix 2.05.3(4) -1, the invert of the
primary discharge pipe elevation for each sediment pond is located just above the
maximum sediment storage elevation. The Division is concerned that the sediment
ponds may have sediment discharge problems due to this small elevation difference.
The Sedcad manual, on page 64, recommends a minimum 2 foot difference between the
top of the sediment level and the primary pipe invert. If the release is slow, 0.5 feet to
1.0 feet can be used. Please consider increasing the height between the top of the
sediment storage level and the invert of the primary discharge pipe, allowing for the
requirement mentioned in question number 9 of this section that the pond capacity
between the primary discharge pipe and the emergency spillway must contain the runoff
volume from a 10 year -24 hour event.
13. Figures 1 -4 of Appendix 2.05.3(3) -1 show that the sediment pond primary discharge pipes
will extend beyond the permit boundary. Please revise these figures to show that the
discharge pipes will not extend past the permit boundary.
DRMS: The Division has no further concerns with this question. Figures 1 -4 were revised
in the May 26, 2011 submittal. However, the Division has two additional requests.
a) It does not appear that the primary and emergency discharge structures for the three
sediment ponds are shown on Map 2.05.3(3) -l. Please add these structures to the map
since they are part of the surface water hydrology.