2007-06-01_PERMIT FILE - C1981019 ‎(3)‎

• Permit No: C1981019
• IBM Index Class Name: Permit File
• Doc Date: 6/1/2007
• Doc Name: Attachment 1 to Attachment 12
• Section_Exhibit Name: Exhibit 07 West Pit Pond 008A
• Media Type: D
• Archive: No

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COLOWYO COAL COMPANY
008A -WEST PIT
SEDIAAENTATION POND SUMMARY
OR(G1NAL 1998 1998 2006 DIFFERENCE
CONFIGURATION STUDY STUDY DIFFERENCE STUDY 1998 T4 2006
ATERSHED AREA (aeras):
Disturbed 0.0 0.0 0.0 0.0
Pnsimining Topsoiled and Beaded 80.6 90,4 9.8 87.5 -2.9
Pasbntning Undisturbed 22.7 0.0 -22.7 23.2 23.
t-2 YearReCiamaBan 20.6 20,9 0:3 0.0 -20.9
3+YearReCtamatlon 379.9 446A 66.1 88,8 -357.2
Tn~l Area
.. 503,8 557.3 53.5 199.5 -357.
POND PARAMETERS:
eattam Elevation 6820.7 6820.7 6820.7 O.p 6821.0 4:3
Prtndpal Spiihvay irrvart Eievatinn 6837.0 6$35.5 6837.0 t5 6837.0 0.0
Emergency SpliMray Invert Elevat~rr 6837.7 6837.7 683$.0 0.3 6838.0 0.0
lap at Em~nkment 6841.0 6841.0 6841.0 OA 6841.0 0.0
Storage Voume t3etow Emergency SpiiM/aY (aC•R) 13.02 '13.02 12,86 -0.16 13.8 1.0
Storage Volume Below Pdncipal Spillway (ac-ft} 11.62 10.43 11.62 1.19 12.6 1.0
Principal Spitlway Parameters:
Type prop Inlet Drop inlet Perf. Riser Perf. Riser
Riser Diameter (tn} 18.0 18.0 18.0 0.0 18.0 0:0
Riser Heigh({fl} 11.6 10.1 11.6 1.5 11.6 0,0
Barrel Diameter (in} 18.0 18.0 98.4 OA 18.0 0.0
Elevation of Pertnratinn{s) {ft} N!A WA 6830,0 8$30.0
SFie of Perforatian(s} {in} N1A NIA 4.0 4A
Number of Perforations NJA N1A 3 3.0
Emergency SpIllway Parameters.,
Type Trapezoidal Trapezoidal Trapezoidal Trapezoidal
Diameter{in) N/A NtA NIA NIA
Baroom Width {ft) 20,0 20.0 24:0 4,0 24.0 0.0
Length (tt) 25.0 25.0 21.0 -4.0 21.0 0.0
5We Slopes'z`H:iV (ft) 2.0 3.0 1.5 -1,5 1.5 0.0
HYDROLOGiCMYDRAtfLIC pARAMETERB:
Base Plav Rates (Cfs) 1.00 0.03 -0.97 0.03 0,0
t0-Year, 2A-Hnur Sfarrrt Event:
PreciPitauan pn) 1.8 1.8 0.0 1.8 0.0
Runoff Volume (ac-ft) 4,8 5,3 0.6 3.5 -1.
Pdnctpat Spittway Peak Discharge {c(s) 12.2 2.4 -9.8 1.7 -0.7
Emergency Spillway Peak Discharge (cfs) O.b OA 0.0 0.0 0.
Peak Surface Water Stags Elavatian (ft) 6837.6 6833.7 -3,9 6831.7" -1.9
25-Year, 24-Hwrr Storm Event
PreciPitatian (In) 2,3 2.3 OA 2.3 0.
Runoff Vtuume (aC•tt) 8.1 9.1 9.0 6.5 -2.6
Princfpai Spiihvay Peak Discharge {afsy 14.2 3.1 -11.1 2.4 -b:7
Emergency Spi(tway Psak Dscharge {Cfe) 14.0 OA -94.0 OA 0.0
Peak Surface Water Stags Elevation (ft) 8838.4 6836. i -2,3 6833.6 -2.6
Pond fraebnard tft 2.6 4.9 2.3 7.4 2.6
SEDIMENT LOADINGS PARAMETERS:
Storm Predicted Psak Satt~bla CnncentraGan (mUi} 0.00 0.00 0.0 0.00 OA
Predicted Annual Sediment Loading {ac-ft} 0.17 0.49 0.32 0.49 OA
Availatsla Sediment Storage Volume {aC•ft} 4.68 1.88 -2.80 2.18 0.3
Maximum Sediment Storage Elevation (fl) 6825.4 6825.4 6825.4 0.0 6825.4 0.0 i
Predicted Number at Story Years 27.5 3.8 -23.7 4.4 0.6'.
Exh. 7-WP-16 Revision Date: 2/1/06
Revision No.: TR-63