2008-09-08_REVISION - C1994082

• Permit No: C1994082
• IBM Index Class Name: REVISION
• Doc Date: 9/8/2008
• Doc Name: Response to Preliminary Adequacy Comments
• From: Seneca Coal Company
• To: DRMS
• Type & Sequence: TR37
• Email Name: DTM
• Media Type: D
• Archive: No

SE
coal C0nWWW Seneca Coal Company
September 4, 2008
Mr. Dan Mathews
Division of Reclamation, Mining and Safety
101 South 3rd, Suite 301
Grand Junction, CO 81501
[phone] SEP Q 0 4008
Diviswu '--Oamation,
RE: Yoast Mine Permit No. C-94-082 Mining and Safely
Technical Revision (TR-37)
Response to Preliminary Adequacy Comments
Mr. Mathews,
SCC has reviewed the PAR Comments that you hand delivered on June 17, 2008 and the additional itemized review
comments dated July 1, 2008. We have developed the following responses to each comment. In addition we have
categorized and numbered the responses accordingly.
• 1. The revised As-Built Report for Pond 010 contains new SEDCAD demonstrations for the l0year and 25year, 24-hour event. The
100year, 24-hour event is discussed in text but was not revised with this submittal. The 100year, 24-hour event demonstration would
only be required if the impoundment meets the size criteria of 30 CFR 77.216(a) or if it meets the Class B or C criteria for dams in
NRCS Technical Release No. 60. However, since the As-Built Report states that the spillway geometry and peak discharge are based
on the 100-year, 24-hour storm event it would be appropriate to update the 100year, 24-hour demonstration for inclusion into the
revised As-Built Report.
Response: The Division and SCC have commented on the inclusion of the Pond 010 100-year, 24-hour event
demonstration in several recent technical revisions. It is SCC's understanding the 100-year, 24-hour event was included
in the original design (December 1997) to address regulations existing at that time; however, SCC is unable to confirm
this assumption. Subsequent as-built reports have retained demonstrations for the 100-year, 24-hour event. SCC
agrees that the 100-year, 24-hour demonstration is only needed if the impoundment meets the criteria referenced by the
Division in this comment and acknowledges the impoundment does not meet the criteria.
In its response to the Division's TR-35 Adequacy Comments of September 5, 2007, SCC revised the Pond 010 As-Built
Report to clarify that the emergency spillway design and subsequent construction are overly conservative - both
incorporate the 100-year, 24-hour event. The 100-year, 24-hour demonstration is retained in Part II of the Pond 010
As-Built Report because Part II presents the as-built construction documentation that demonstrates the pond meets or
exceeds the design and performance requirements of the Regulations of the Colorado Mined Land Reclamation Board
for Coal Mining. Exhibit 13-4A, is the corresponding, certified as-built drawing; the exhibit table summarizes the
minimum configuration needed to safely convey the 100-year, 24-hour event. SCC personnel have explained to
Division staff that it is inappropriate to revise Exhibit 13-4A because this exhibit was certified by the engineer who
oversaw the pond and embankment construction; Mr. Mike Boulay concurred during a phone conversation on June 24,
2008.
•
Seneca Coal Company a P.O. Box 670 • Hayden, Colorado 81639
Telephone [phone] • FAX [phone]