2008-10-07_PERMIT FILE - C1981047

• Permit No: C1981047
• IBM Index Class Name: Permit File
• Doc Date: 10/7/2008
• Section_Exhibit Name: Appendix C Calculations for the Sediment Control Ponds, Culverts, Diversions, Soil Loss Comparison
• Media Type: D
• Archive: No

• DR is the sediment delivery ratio discussed in Section IV
of the referenced technical notes. This factor is a
judgement factor which takes into account the configuration
of the watershed and the amount of the sediment that would be
deposited enroute to the sediemnt pond. Deposition points
include Ditch A for Area A, Diversion BC and Ditch A for
Areas B and C, and Ditch D for Areas D and E. All of these
ditches area relatively flat and should cause most of
the sediment load from these areas to be deposited prior to
sediment reaching the sediment pond.
Figure 4 of the referenced technical notes lists values of
the Topographic Factor "LS". A note at the bottom of Figure
4 indicates that when the length of slope exceeds 400 feet
and or the percent slope exceeds 24 percent, soil loss
estimates are speculative as those values are beyond the
range of research data.
Considering the above factors it is clear that the sediment
volume calculation presented above is at best an educated
guess. The formulas used are considered speculative and
the configuration of the collection ditches provides long
flow distances for probable deposition of sediment prior to
the sediment reaching the pond.
• The important issue regarding sediment accumulation in
sediment ponds is to provide for periodic clean out of
the sediment. It should be noted that no significant
sediment has accumulated in the pond since it was constructed
in 1986. After the sediment pond is revised as outlined below,
the Operator commits to cleaning the sediment from the pond
after the sediment level reaches 60% of its design volume.
A new Pond Certification will be required after the elevation
of the emergency spillway is revised as outlined below. This
new certification will indicate the elevation that the sediment
in the pond can accumulate before clean out is necessary.
The elevation of the sediment level in the pond will be
determined by measuring down from the elevation of the
primary spillway.
SUMMARY SEDIMENT POND 5 SIZING CALCULATIONS
TOTAL REQUIRED WATER VOLUME
TOTAL REQUIRED SEDIMENT VOLUME
0.49
0.20
TOTAL REQUIRED SEDIMENT POND 5 CAPACITY -- AF 0.69
Pond 5 has a total capacity of .795 AF. This information is
presented in the #5 POND CERTIFICATION prepared by Larry M.
Reschke on 10-29-86. This certification indicates that the
water capacity totals 0.455 AF and the sediment capacity
• totals 0.29 AF.
C-15
3-29-91
~ a.