20171446 Ver 1_SW Plan_20171109

�� ��
HlghWdy North Carolina Department of Transportation �.
Storn�wa�er
- ,�«�.���.,� � Highway Stormwater Program =�
STORMWATER MANAGEMENT PLAN —
(Version 2.07; Released October 2016) FOR NCDOT PROJECTS
WBS Element: 17BP.14.R.48 TIP No.: County(ies): Macon Page 1 of 1
Bridge to Culvert Avoidance and Minimization
Proposed Structure Summa
Sheet No. & Station Sheet No.: Station: Number of Barrels: 1
Drainage Area (ac or sq mi): 1.3 Sq. Miles Barrel Width/Diameter (ft): 16
Surface Water Body: Watau a Creek Barrel Hei ht ft: 4.25
Culvert T e: Corru ated Aluminum box culvert Culvert Len th ft 42.5
Avoidance and Minimization Efforts:
(Bridge to Culvert)
Stream Slope Fish and/or Aquatic Life Passage
Existing Average Stream Slope (%�: --3.5 % Existing Low Flow Channel Dimensions 10'
Proposed Culvert Slope (%): 3.61 % in the Stream:
Culvert Burial
Proposed Culvert Burial Depth (ft): 1
Existing Streambed Material: gravel, sand and cobble Proposed Low Flow Dimensions 8 ft. wide 0.5' deep
Through the Culvert:
Proposed Sills/Baffles: There will be three 1.5' H sills (one mid-culvert) with 8'
W x 0.5' D notches Existing Low Flow Velocities in the
Stream (ft/s): 7'83
ropose ow ow e oci ies roug
the Culvert (ft/s): 7'83
Alternating Low Flow Sills/Baffles: There will be three 1.5' H sills (one mid-culvert)
with 8' W x 0.5' D notches
Culvert/Stream Alignment
Stream Patterns Upstream and Downstream The stream pattern should not affect fish passage. The slope is relatively consistent and the meander above and below the culvert is moderate.
of the Culvert that Could Affect Fish
Passage and Bank Stability:
Bed Forms Impacted by Culvert (riffles, Structure is in a glide to riffie transition.
pools, glides, etc.):
Low Flow Floodplain Bench Required? Yes Short benches are proposed to transition the culvert into the incised stream channel upstream and downstream of the culvert.
(provide justification)
Bends at Inlet/Outlet? Yes The culvert should provide a relatively gradual transiion in into the existing channel bends upstream and downstream of the culvert.
(describe culvert alignment with stream)
Stream Realignment Necessary? (provide No
justification)
Bank Stabilization: Standard rip rap stabilization and benching is proposed at both the inlet and outlet of the cuivert.
Outlet Velocities
Natural Stream Channel 2-yr Velocity (ft/s): 6.99 Natural Stream Channel 10-yr Velocity (ft/s): 6.68
Proposed Culvert 2-yr Outlet Velocity (ft/s): 7.92 Proposed Culvert 10-yr Outlet Velocity (ft/s): 10.07
Roadway Geometric Considerations
Evaluate/Describe Roadway Geometric Constraints:
The existing roadway alignment and vertical celarance limitations do not lend well to a bridge, so the culvert has been pursued for this crossing.