2012-01-18_REVISION - C1994082

• Permit No: C1994082
• IBM Index Class Name: Revision
• Doc Date: 1/18/2012
• Doc Name: Proposed Decision & Findings
• From: DRMS
• To: Seneca Coal Company
• Type & Sequence: SL3
• Email Name: SLB
• Email Name: SB1
• Media Type: D
• Archive: No

C. Suspended Solids Demonstration
SCC submitted pond discharge sample data for all of the ponds receiving discharge from
the proposed release area, as well as receiving stream sample data from monitoring points
upstream and downstream of the pond outfalls. The pond outfall data indicate that total
suspended solids (TSS) contributions do not exceed the limits set forth by the Colorado
Department of Public Health and Environment. Monitoring data of the upstream and
downstream receiving stream sites indicate that TSS is reduced from the upstream site at the
downstream site.
The sediment ponds receiving runoff from the proposed release area (Ponds 010, 011, 012,
013, and 014) have all been proposed as permanent ponds; the operator demonstrated that
the quantity and quality of impounded water were appropriate for their intended use. Final
approval is dependent on approval from the Colorado Department of Water Resources
where water rights are concerned.
In addition to the pond effluent sample data submitted by SCC, the Division requested
annual sediment level data from Seneca Coal Company (Table 2) for the ponds receiving
runoff from the proposed release area. The data show that sediment levels in the ponds
have stabilized since revegetation activities began in 2006. None of the ponds have
required cleaning since Pond 010 was dredged in 2002 and Pond 011 in 2003.
Table 2 - Sediment Data Provided by Seneca Coal Company
Sediment Trends
(ac -ft gained/lost by year)
Pond ID
2005
2006
2007
2008
2009
2010
2011
watershed area
010
0.0
3.1
0.2
-2.3
0.0
-0.2
-0.2
940.4 ac
011
0.0
0.2
0.7
-0.7
0.0
0.0
0.0
141.3 ac
012
0.0
-0.3
1.9*
3.2*
0.0
-0.4
0.2
36.8 ac (336.6)
013
0.0
-0.2
0.7
-0.4
0.1
-0.1
0.1
34 ac
014
0.0
-0.8
1.3
0.1
3.0
-0.1
0.1
154.3 ac
from the adjacent Pond 012 landslide
The Division also independently completed a Revised Universal Soil Loss Equation
(RUSLE) calculation comparing the reclaimed areas to the adjacent unmined areas. The
Division's calculation was based on data in the permit application package for climate, soil
types and control /practice factors; slope measurements from the existing topography maps
submitted annually by SCC; and vegetation monitoring data from the SL -3 application for
the Phase H bond release and Extended Reference areas. Several slopes in the reclamation
area were individually modeled and then averaged and compared to a weighted average of
the extended reference areas. The calculations, presented in Table 3, indicate that sediment
delivery from the mined areas is approximately equal to that of the adjacent unmined areas.
Yoast Mine C- 1994 -082 Page 8 of 17 Phase II Bond Release SL -3