PERMFILE57973

• Permit No: C1981038
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: VOLUME 8- RUNOFF PREDICTIONS
• Media Type: D
• Archive: No

accumulates to 30 percent o` the sediment dead storage volume. A
Universal recording precipitation gace, installed in February, 1977 will be
cperated on a continuing basis to ronitor rainfall. The spillv:ay of the
loe:errost pond will be equipped with a stilling v:ell and vrater level recorder
to moni[or any overflo~.JS should they occur.
It is proposed that after mining has ceased, that the retention ponds remain
in place to fore a series of drops in this reach of channel. The channel v;ould
be reinforced with heavy riprap vrhere necessary to prevent scouring of bed and
banks. It is believed that the stream v,ill have begun to adjust itself to a
ne.v flow regime by the time mining activities are terminated. Additional
disturbance by re~.,oval of the structures would again disrupt the fl o:, regime
causing increases in sedimentation and changes in channel morphology.

cable 1. Upstream area, inflow, and capacity of Orchar~~l+~~e~y ~~~~~~~~~~
sedimen*. retention ponds - Alternative 1.
__ __~
~ Approximate I Estimated
Pond Upstream Area ~ 10-year,24-hours Design
• Yur.,ber1 I (Acres ~ Inflow ~ Capacity
Disturbed Undisiurbed~ (Acre-feeL)z i(Acre-feet)
_• ~
11.0 ~ 0.11
~
1 12.3 ' •49 0.90
I
2 4.5 .04
7.5 I .30 .60
3 8 4 4.5 i .04
r 6.9 j .28 I 7.00
(0.5 A-F
r ~ r I each pond)
iPonds are consecutively numbered in downstreafl direction;
tlo. 1 is the uppermost pond.
2Estimated direct runoff fro^, 10-year, 24-hour precipitation event:
Disturbed watershed O. Ofi acre-feet/acre.
Undisturbed watershed 0. 01 acre-feet/acre.