20151021 Ver 2_B4792_REVISED Culvert Avoid and Min_20160205

Carpenter,Kristi
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Ladies and Gentlemen,
Davis, Mark S
Friday, February 05, 2016 9:45 AM
'Lori Beckwith ([e-mail])'; Chapman, Amy; Carpenter,Kristi;
Barnett, Kevin; [e-mail]; Chambers, Marla J; DeWit, Benjamin J
Deyton, Joshua B; Hill, Mark E; Morgan, Stephen R
Bridge No. 4- B4792 - NW14 Permit Modification - Polk County
Bridge No. 4- B4792 - NW14 Permit Modification - Polk County.pdf
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Attached for your review and comment is the subject permit modification. The original culvert design had water flowing
through both barrels. The modification now has the flow going through one (low flow barrel) with sills. The high flow
barrel now has a two-foot sill and floodplain benches on the inlet and outlet ends of the culvert. The stream impacts did
not change; however, the permit drawings did. If you have any questions, please advise.
Thanks, Mark
Mark S. Davis
Environmental Supervisor
NC Department of Transportation/Division 14
828 586 2141 office
282 508 9670 mobile
markdavis(cancdot.qov
253 Webster Road
Sylva, NC 28779
�M � +� � � �
Email correspondence to and from this address is subject to the
North Carolina Public Records Law and may be disclosed to third parties.
Email correspondence to and from this sender is subject to the N.C. Public Records Law and may be disclosed to third parties.

[ li�,ll��'�l�' North Carolina D�partment of Transpmrtation
�1�7:'1i1��'aFCr }Eighway Storrsirvater Program �/�'
STQRMWATER MAFiAGEMEN7 PLA�I ��=�i
(Venian 2.01; Released Oecomber 2014J FOit NCDOT PRb,tECTS
WBS Element: 3&562.1.7 71P tUo.: B-4792 Coun ies : Polk Pa e 3 of 3
B�idge io Cu[verd Avo'sdance and Mdniomizatior+
Pra osed Struttur� Surroma
Sheet No. & 5tatian Sheet No.: 4 Station: 12+�1.63 Number oi Cuiverts: 2
Draina e Area 8C bC 5 mi : Z.Q9 S. Mfles Culvert WidthlDiameter ft: 11
Surface Watcr Bod : {1)Fork Creek Culvert Hei ht ft: 6
Culvert T e: Refnforced COncr�te Box CulveR Culvert Len th ft 48.57
Avoidanee and M�nimizatipn ESforts: H�ve made att�mpts ro avoid impacts ro streams and wetlands to the greatest extent practicable in the design of the preferred altemafive. Desrgn
(8ridge ta Gulve�rt) Standards in Sensrstive Watersheds was followed during khe project design due to NCWRC designation of troul waters.
Stream Slo o Fish andlor A uatic Life Passa a
Existin Avera e Stream Slo e%: 3.$0 °/n Existing Low Flow Chanrtel Dimensions Low flow dimensions were about 24'. No
Pro osed Gulvert Sfo e%: 4.00 % in the Stream: natural defin�tiv� low flow Ch�nnel.
Gulvert Burial
Pro osed Culvert Burial D� th ft: 1
Existing Streambed f4'laterial: Alluvial sand, grauel, cobbles and boulders Proposed Low Flow Dimensions Proposed low flpw d+mensions are both barrels
Tiirough the Culv€rt: of the culvert (22'}
Proposed SillslBaffles: 1 ft. sill across both barrels in inlet and outlet.
�zistirag Law Flow Velacitias irr the � 9�PS
Stream iUs : '
ropos� aw ow e octLes roug
thc Cu�vert ftfs ; $.9 fps
AEternating Low Flaw SillslBaffles: 1 fr. sill acrass both barrels in Vnlet and outlet.
Culvert slope �2%.
Cu�vortlStream Ali nment
Stream Pattems U�astream and Downsteeam None noted.
of the Culvert that Cvuld AfFect Fish
PaSsagc and Bank Stability:
Bcd Form� Impacted by CulverC (rifffes, Stream is on 4% grade, no pools nr gfides exist.
pools, g[ides, etc.):
Low Flaw Floodplain Bench Required7 No
(provide justification�
Sharp Bends at Inlet+Qutlet? No
(d�SCribe tulvert dli nment with streamj
S4ream Rea6ignment Necessary? {provide h5o
justifica€ion}
Bank Stabilization: 13a37 tons oE Class I rip-rap used for approximacely 25 feet afong strea�n on each bank. both at the in3eR and the oudet of the culuert.
puk[et Vetocities
Natural Stiream Channel 2- r Veloci ftis : N1A �latural Stream Chartnel 't0- r Ve[oai {ftls : 7.1
Pro ased CulveR 2- r Outlet Veloci ftls : NIA Pro osed CulverY �t�- r Outlet Veloci ftls : 4.36
Roadwa Geometric Considera�eans
�ua�uatelDescribc Roadwa Gcometric Cortstraints:
Phased construction to be used during bridga ramoval and Cui�eR install�tian.