REV13055

• Permit No: C1994082
• IBM Index Class Name: Revision
• Doc Date: 5/25/2007
• Doc Name: Adequacy Response Letter
• From: Seneca Coal Company
• To: DRMS
• Type & Sequence: TR30
• Media Type: D
• Archive: No

E~~~1
S Coal Company Seneca Coal Company
May 21, 2007
Mr. Michael Boulay
Division of Reclamation, Mining and Safety
101 South 3«', Suite 301
Grand]unction, CO 81501
[phone]
via: FedEx 859229799860
F~~~E9V~D
MAY 2 5 2001
RE: Yoast Mine (Permit No. C-94-082)
Technical Revision No. 30 (TR-30)
Responses to Adequacy Comments
Dear Mr. $oulay:
Division of r,::.:nreuon,
Mining and Safety
Seneca Coal Company (SCC) has reviewed you letter regarding Techxucal Revision No. 30, Pond 10
Storage Capacity Demonstration, dated Apri124, 2007, and is providing the following responses to the
comments.
The reference far the updated R value taken from Derign Hydrology and Sedimentology for Small Catchmentr
war not attached ar indicated on page 13-3A.3. Pleare incorporate this attachment for inclusion into the
permit application package (PAP).
Response: The attachment has been included in the permit application package as Attachment 13-
3A-1.
2. Anew curve number war ured in the Pond 010 derign for Rack Outcrop". Pleare update Table 13-12.1 to
the PAP with the new eznve number.
Response: Table 13-12.1 has been updated to include a clove number value fox "Rock Outcrop."
SCC would like to note that this value is a previously approved curve number (see Table
13-1, Curve Number Values for Yoast Mine.
3. According to the l0year, 24-hour SEDCAD demonstration, there it only .21 feet between the tap of
rediment rtorage and the low-hole spillway. Ar derigned the model demonrtrates that the pond would roll
provide adequate capacity to contain or treat the inflow entering the pond ar a rerult of 10-year, 24-hour
precipitation event. However a more prudent derign and to avoid reruspension of sediment would be to allow for
additional rpace between the tap of rediment storage and the lowest rpillway elevation. In the SEDCAD 4
Urer'r Guide (page 64) it it ruggerted that a minimum two foot elevation difference exirtr between the invert of
the principal rpillway and the top of the sediment rdorage area. If a slaw pasrive dewatering rystem u employed
.ruck ar the low-hole rpillway of Pond 010, the elevation can be reduced to 0.5 to 1.0 ft, depending upon the
rite and flow rate of the dewatering hale. Please nconrider the design far Pond 010 to allow far between D.S to
1.0 ft between the top of rediment rtorage and the /ow-hole rpillway.
Response: SCC has revised the 10-year, 24-hour storm even[ SEDCAD4 demonstration for Pond 10
to increase the elevation difference between the top of sediment and water surface
(principal spillway invert elevation) to approximately 1.0 feet as recommended by
Colorado Division of Reclamation, Mining and Safety.
Seneca Coal Company • P.O. Box 670 • Hayden, Colorado 81639
Telephone [phone] • FAX [phone]