PERMFILE41923

• Permit No: C1982057A
• IBM Index Class Name: Permit File
• Doc Date: 10/4/2002
• Doc Name: Drainage and Sediment Control Plan
• Section_Exhibit Name: Tab 13 Attachment 13-5B
• Media Type: D
• Archive: Yes

Srptrmhrr 1998 Srnrto IIIY/ South E apannan 'Drainage anASrrlimrn! Contml Plan • 5
4.0 PONDS
. All three ponds are designed to effectively treat the peak runoff produced from the 10-year, 24-hour
storm event. The ponds were designed using SEDCAD+ computer program. The input pazameters
and results are shown on the SEDCAD+ printouts located in Appendix 1, Sediment Pond SEDCAD
Results, and summarized in Table 5. The location of the ponds along with pond and embankment
configurations for Ponds 015, O1G and 017 can be found on Drawings
13-8,13-8A and ]3-8B.
All three ponds will employ a principal spillway which consists of an S foot tall, cmp riser, with a cmp
culverc. AU three ponds employ an emergency spillway. The spilways will be a trapezoidal channel
with 3H:1 V side slopes. The outslope of the spillways will be armored. The spillways are designed to
safely pass the peak discharge from the 25-yeaz, 24-hour storm event .vhile maintaining over 1 foot of
freeboard. The spillways are conservatively designed assuming the prinupal spillway is clogged and the
water level is at the invert level of the spillway prior to the storm event.
The embankments for all three ponds are less than ] 5 feet in height when measured from the upstream
side. The embankments will be constructed with 3H:1V slopes and a top width of 75 feet. Prior to
construction of the embankments all topsoil will be removed and stockpiled. A keyway will be cut
down the center of the embankment. The embankment will be constructed in lifts not exceeding
twelve inches in loose thickness. Each lift will be compacted by at least one pass of the bulldozer
tracks over the entire lift before additional material is placed. The fill material will not contain sod,
large roots, other large vegetative matter, or coal waste. Placement will not occur during periods of
excess moisture.
5.0 HAUL ROAD CHANNEL AND CULVERT DESIGNS
• All haul road ditches were designed to safely pass the peak discharge from the 10-year, 24-hour event.
The ditch dimensions were determined using Mannings Equation for open channel flow. All road side
ditches will be gravel lined. All road side ditch inputs and results can be found in Appendix 2, Haul
Road Channel and Culvert Designs. The design results and ditch locations are shown on Exhibits 13-
21.1, 13-22.1 and 13-23.1. As shown on the ditch results, the flow velocities for all the road side
ditches aze less than G feet per second and will not require riprap.
The culvens were designed to safely pass the peak dischazge from the ]0-yeaz, 24-hour event. The
culverts were sized using the U.S. Bureau of Public Roads nomograph. All culvert design inputs and
results can be found in Appendix 2, Haul Road Channel and Culvert Designs.
Haul Road J is designed as a relatively flat road and the location and length of road side channels and
location of culverts is difficult to predict until the road is built. Given the difficulty to predict the
location and length of the ditches, the ditches were conservatively designed to handle the peak
dischazge from the entire watershed above Hau] Road J. Culver J1 was also conservatively designed
to handle the peak discharge from the entire watershed above Haul Road J and Haul Road I. Culvert
J-2 vas designed to pass the peak flow from the entire watershed above the Pond 076 system,
assuming worst case disturbed conditions. Additional culverts may be required along Haul Road J.
These additional Culverts were conservatively designed to handle the peak dischazge from the entire
watershed above Haul Road J.
•
Montgomery Wrahon hlimnr C.mup • lGi S. Uuon Bou&ian1, Suin 1G0 • t~birvwd. Gdo ~ 80778 • [phone]
Rev 1/02