PERMFILE107771

• Permit No: C1980005
• IBM Index Class Name: Permit File
• Doc Date: 9/12/2006
• Doc Name: Pond 008 Emergency Spillway As-Built Report
• Section_Exhibit Name: Tab 07 Appendix 7-6f.2
• Media Type: D
• Archive: No

Introduction
Sediment Pond 008 was originally constructed in 1987. The pond is located
in the NW/4, Section 7, Township 5 North, Range 86 West (see Exhibit 13-2A,
Postmining Topography and Permanent Features) in the Bond Creek drainage,
which is tributary to Fish Creek. The contributing watershed is
approximately 271 acres, of which 224 acres were disturbed by mining
activities, and which have since been reclaimed and revegetated.
Pond 008 was constructed as an earthen fill embankment pond (see Exhibit 7-
17A, Sediment Pond 008 As-Built). The original spillway was a 6-inch
diameter orifice cut into a 29-inch diameter drop inlet pipe. In 1992, a
trapezoidal emergency spillway channel was cut into the embankment to
increase the capacity of the pond. Certified as-built reports for each
phase are included as Appendix 7-6f.1, Pond 008 1987 As-Built Report and
Appendix 7-6f.2, Pond 008 Emergency Spillway As-Built Report. Certified
as-built drawings for each phase are included as Exhibits 7-17A and 7-17C,
Sediment Pond 008 As-Built.
• During the April 2005 inspection following snow and ice melt, Seneca Coal
Company (SCC) representatives noted that th e "existing" principal spillway
was no longer functioning as designed and constructed. The 24-inch CMP
riser pipe had significantly deteriorated below the 6-inch inlet orifice
and was not retaining the design volume of water. SCC submitted a
technical revision (TR-39) which presented the design an d replacement plan
for a new principal spillway pipe in June 20 05.
The replacement principal spillway construction was initiated and completed
during August 2005. The new principal spillway is an 8-inch diameter
plastic corrugated straight pipe set at an invert elevation of 7,015.3
feet. A screened cage is fitted to the inflow end to prevent trash and
debris clogging the spillway pipe.
The redesign did not affect or include the pond embankment configuration
(except to abandon the old pipe and install the new pipe) or the existing
emergency spillway channel. The existing 29-inch CMP straight pipe was
abandoned as follows: the pipe was uncovered for approximately 15 feet at
the downstream end; the exposed pipe was crimped; concrete was pumped into
the straight pipe until the barrel through the embankment was filled; and,
the exposed pipe was backfilled at both the downstream end and the riser.
TR-37 1 Revised 10/OS