2011-07-01_PERMIT FILE - C1982057 ‎(7)‎

• Permit No: C1982057
• IBM Index Class Name: Permit File
• Doc Date: 7/1/2011
• Doc Name: Pond 016 Spillway Certifiation
• Section_Exhibit Name: Tab 13 Attachment 13-5F Appendix 1
• Media Type: D
• Archive: No

In some instances, mining will cause the drainage area to change during the life of the
• sedimentation structure. When the pit moves into the watershed, runoff is intercepted by
the pit. In these cases, a conservative procedure was used; the structure was analyzed
for the largest anticipated disturbed drainage area that will contribute runoff to the
structure. It was estimated that this condition will occur if all of the proposed mining area
is disturbed and the area is in different phases of mining and reclamation. In addition, the
structure was conservatively designed to include adequate capacity for sediment storage
and to treat the runoff from a 10-year, 24-hour precipitation event. FinaNy, the design
conservatively assumed the principal spillway is clogged during the 25-year, 24-hour
precipitation event and provides for maintenance of adequate freeboard to prevent
overtopping of the embankment. The SEDCAD output for the pond as-built conditions are
presented in Addendums 13-5F-A, 13-5F-B, and 13-5F-C.
Summarv
The capacity of Sedimentation Pond 016 is attributed partiaNy to the embankment and
partially to the pond excavation. During passage of the 10-year, 24-hour storm the
spillway does not discharge sediment downstream nor is there any flow through the
emergency spillway. In addition, the spillway is designed to safely discharge the 25-year,
24-hour storm event.
• The embankment was constructed to be stable and provide adequate freeboard. Therefore,
based on the design, this structure complies with the appropriate regulations for a
sedimentation structure. Seneca Coal Company will periodically inspect the structure for
sediment storage, structural integrity, and hazardous conditions. Maintenance and
remedial work will be performed in accordance with the approved mine permit.
Construction Summary
In accordance with Rule 4, Part 4.05.6110) of the Rules and Regulations of the Colorado
Mined Land Reclamation Board pursuant to the Colorado Surface Coal Mining Reclamation
Act 34-33-101 et seq., I, Michael G. Altavilla, hereby certify that the construction of
Sedimentation Pond 016 was inspected and constructed under my supervision. The
construction of Pond 016 was supervised on site by Dan Allen, Surveyor, and Roy Karo,
Reclamation Manager, at the Seneca fl-W Mine. Dan and Roy assured all work was
performed in accordance with the design and the specifications.
•
13-5F-2 Revised 06/01