2008-12-04_PERMIT FILE - C1994082 ‎(33)‎

• Permit No: C1994082
• IBM Index Class Name: Permit File
• Doc Date: 12/4/2008
• Doc Name: Part I Pond 014 Postmine Storage Capacity Addendum
• Section_Exhibit Name: Tab 13 Attachment 13-17.1
• Media Type: D
• Archive: No

This storage capacity demonstration amends the As-Built Report dated October
2001. This addendum provides updated SEDCAD4 hydrology and sedimentology
demonstrations which incorporate recent (2007) changes to the drainage and
sediment control network that drains to Pond 014. In addition, the SEDCAD4
demonstrations evaluate the current watershed condition in support of
retaining Pond 014 as a permanent postmine feature.
The sediment storage capacity has been recalculated using watershed
conditions as of September 2007. This is an appropriate approach because the
previous As-Built SEDCAD modeling demonstration evaluated sediment delivery
to the pond based on worst-case disturbance conditions. The worst-case
disturbance approach resulted in a much higher amount of sediment delivery
than the amount delivered in the current (reclaimed) condition.
Consequently, the amount of storage volume needed to effect compliance with
Rule 4.05.2(7) and Rule 4.05.6(3) has greatly decreased. Therefore the top
of sediment elevation can be increased and the pond cleaned less frequently
than calculated in the original as-built report.
The capacity of Pond 014 is attributed partially to the embankment and
partially to the pond excavation. The embankment design, construction and
resulting stability analyses were previously certified and have not changed.
Structure elevations input into the modeling conducted for this evaluation,
and shown on Exhibit 13-17, Pond 014 As-Built, have been verified by physical
surveying.
As-Built Analysis
SCC constructed a new postmining drainage channel in the Pond 014 watershed
during 2007. This channel is incorporated into the SEDCAD4 demonstration
attached to this report. The channel network that drains to Pond 014 is
shown on Exhibit 13-12.1A, Permanent Channels and Ponds, and Exhibit 20-2,
Postmining Topography Map. Channel designs are presented in Attachment 13-
12.3.
The TR-37 hydrology and sedimentology evaluation demonstrates that Pond 014
meets or exceeds the design and performance requirements of the Regulations
of the Colorado Mined Land Reclamation Board for Coal Mining. Specifically,
the as-built configuration adheres to the following requirements:
• Provide adequate storage and treatment for runoff from the 10-year, 24-
hour storm event to assure compliance with receiving water quality
standards in accordance with Rule 4.05.6(3)(a);
TR-37 13-17.1-1 Revised 08/08