20161008 Ver 1_SF-610228_HYD_SMPv2.02_2015-07-14_20161019

North Carolina Department of Transportation
Highway Stormwater Program
STORMWATER MANAGEMENT PLAN
FOR NCDOT PROJECTS
(Version 2.02; Released April 2015)
WBS Element:
17BP.8.R.58 - 610228TIP No.:County(ies):Montgomery Page 2of 2
Bridge to Culvert Avoidance and Minimization
Proposed Structure Summary
Sheet No. & StationNumber of Culverts:1
Sheet No.:4Station:13+90
Drainage Area (ac or sq mi):1.2 sq. mi.Culvert Width/Diameter (ft):31'-1" x 9'-2" Aluminum Box Culvert
Surface Water Body:(1)Suck Branch9'-2" with 1' buried below stream invert
Culvert Height (ft):
40'-6"
Culvert Length (ft)
Culvert Type:Aluminum Box Culvert
Avoidance and Minimization Efforts:Used 9' lanes to minimize the length of culvert and stream impacts
End walls used to minimize the length of culvert and stream impacts
(Bridge to Culvert)
Stream section/geomerty will be maintained thru culvert with the use of sills
Maintaining low flow velocities
Stream SlopeFish and/or Aquatic Life Passage
Existing Average Stream Slope (%):1.00
%
Existing Low Flow Channel Dimensions 8' wide x 1' deep
Proposed Culvert Slope (%):1.00
%
in the Stream:
Culvert Burial
Proposed Culvert Burial Depth (ft):1'
Sand, Gravel and CobblesProposed Low Flow Dimensions 8' wide x 1' deep
Existing Streambed Material:
Through the Culvert:
2'-0" Sill at each end of culvert with low flow channel
Proposed Sills/Baffles:
8'-0" wide x 1' deep low flow channel with 1' flood
Existing Low Flow Velocities in the
0.7 f.p.s.
bench
Stream (ft/s):
Proposed Low Flow Velocities Through
2.4 f.p.s.
the Culvert (ft/s):
Alternating Low Flow Sills/Baffles:Low flow sills provided at each end;
No baffles provided because of flat slope (1%)
Culvert/Stream Alignment
Stream Patterns Upstream and None
Downstream of the Culvert that Could
Affect Fish Passage and Bank Stability:
Bed Forms Impacted by Culvert (riffles, No significant bed forms
pools, glides, etc.):
Low Flow Floodplain Bench Required?
Yes
(provide justification)
Sharp Bends at Inlet/Outlet?NoStream is relatively straight through the culvert
(describe culvert alignment with stream)
Stream Realignment Necessary? (provide
No
justification)
Bank Stabilization:Class I Riprap proposed for stream banks and slopes of the floodplain bench.
Outlet Velocities
Natural Stream Channel 2-yr Velocity (ft/s):2.8Natural Stream Channel 10-yr Velocity (ft/s):3.1
Proposed Culvert 2-yr Outlet Velocity (ft/s):3.2Proposed Culvert 10-yr Outlet Velocity (ft/s):3.9
Roadway Geometric Considerations
Evaluate/Describe Roadway Geometric Constraints:
No significant roadway geometric constraints