20171492 Ver 1_SW Plan_20171120

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Storn�water ' �
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STORMWATER MANAGEMENT PLAN �_—
(Version 2.07; Released October 2016) FOR NCDOT PROJECTS
WBS Element: 17BP.11.R.173 TIP No.: SF-940261 County ies : Watau a Page 1 of 2
General Project Information
WBS Element: 17BP.11.R.173 TIP Number: SF-940261 Pro'ect T pe: Brid e Replacement Date: 5/16/2017
NCDOT Contact: Heath Slaughter Contractor I Designer: RK&K - Audrey Burnette, PE
Address: g01 Statesville Road Address: g00 Ridgefield Drive
North Wilkesboro, 28659 Suite 350
Ralei h, NC 27609
Phone: [phone] Phone: [phone]
Email: hslau hter ncdot. ov Email: aburnette rkk.com
CitylTown: County(ies): Watauga
River Basin s: New CAMA Count ? No
Wetlands within Project Limits? No
Pro'ect Description
Project Length (lin. miles or feet): 201 ft(0.038 mi.) Surrounding Land Use: Rural
Pro osed Pro'ect Existin Site
Project Built-Upon Area (ac.) 0.1 ac. 0.1 ac.
Typical Cross Section Description: 2-lanes at approx. 7' each with 2' wide unpaved shoulders 2-lanes at approx. 7' each with no shoulders.
Annual Avg Daily Traffic (veh/hr/day): Design/Future: Year: Existing: 40 Year: N!A
General Project Narrative: This project replaces existing bridge #940261, a 35.5' single span bridge timber floor superstructure on steel girders. The proposed replacement structure will be a(3)-12' x 4'-
(Description of Minimization of Water reinforcd concrete box culvert with wingwalls approximately 36.5' along centerline of culvert. The center barrel will have 1.0' sills, buried 1.0', the two outer barrels will have 2.0'
Quality Impacts) sills, buried 1.0', with 1.0' bench to match floodplain. The floodplain bench will be armored along the stream side with Class I riprap and will have coir fiber matting along the top
for stability. The proposed culvert will have 32 LF of inlet improvements and 33 LF of outlet improvements to help stabilize the stream banks and direct the flow into the culvert.
There is no significant increase in the discharge from the roadway runoff.
Waterbod Information
Surface Water Bod 1: Cove Creek NCDWR Stream Index No.: 8-15
NCDWR Surface Water Classification for Water Body Primary Classification: Class C
Supplemental Classification: None
Other Stream Classification: None
Impairments: None
Aquatic T&E Species? No Comments:
NRTR Stream ID: N/A Buffer Rules in Effect: N/A
Project Includes Bridge Spanning Water Body? No Deck Drains Discharge Over Buffer? N/A Dissipator Pads Provided in Buffer? N/A
Deck Drains Dischar e Over Water Bod ? No (If yes, provide justification in the General Project Narrative) (If yes, describe in the General Project Narrative; if no, justify in the
(If yes, provide justification in the General Project Narrative) General Project Narrative)

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STORMWATER MANAGEMENT PLAN — �
(Version 2.07; Released October 2016) FOR NCDOT PROJECTS
WBS EI@IYI@IIY: 17BP.11.R.173 TIP No.: SF-940261 County(ies): Watauga Page 2 of 2
Bridge to Culvert Avoidance and Minimization
Proposed Structure ummary
Sheet No. 8� Station Sheet No.: 4 Station: -L- 12+07.5 Number of Barrels: 3
Drainage Area (ac or sq mi): 8.5 Sq. Miles Barrel Width/Diameter (ft): 12
Surface Water Body: (1)Cove Creek Barrel Height ft : 4
Culvert T e: Reinforced Concrete Box Culvert Culvert Length (ft) 34
Avoidance and Minimization Efforts: The center barrel matches the existing stream width. The two outside barrels have been buried 1' and blocked 1', with sills to match the floodplain
(Bridge to Culvert) height. The slope is consistent with the existing stream slope and the low flow velocities are minimized. The length of the Culvert is the minimum
required for clear recovery without guardrail that may block flow in overtopping events.
Stream Slope Fish and/or Aquatic Life Passage
Existing Average Stream Slope (°/a): 1.18 % Existing Low Flow Channel Dimensions 10'-14' wide from BOB to BOB and 3' deep.
Proposed Culvert Slope (%): 1.23 % in the Stream: 21' - 24 from TOB to TOB with 0.5:1-2:1 bank
Culvert Burial slopes.
Proposed Culvert Burial Depth (ft): N/A
Existing Streambed Material: Rock and Cobble Proposed Low Flow Dimensions 12' wide from BOB to BOB and 1' deep. 16'
Through the Culvert: from TOB to TOB with 2:1 bank slopes.
Proposed SiIIs/Baffles: The (3)-12'x4' RCBC will have sills at the inlet and
outlet to hold in native material, to create a buried x�sting ow ow e ocities in t e
barrel which will accommodate fish passage within the Stream ft/s : 2'2
low flow barrel. ropose ow ow e oa ies roug
the Culvert ft/s : 4.1
Alternating Low Flow Sills/Baffles: Low flow alternating baffles are not required in
the center barrel since the stream is the same
width as the center barrel.
Culvert/Stream Alignment
Stream Patterns Upstream and The culvert lies in a portion of Cove Creek where the stream is flowing south. The proposed structure lies in a bend in the stream.
Downstream of the Culvert that Could
Affect Fish Passa e and Bank Stabilit :
Bed Forms Impacted by Culvert (riffles, Stream appears to be at a fairly constant grade. There is exposed bedrock within the streambed but none present within the limits of construction.
pools, glides, etc.):
Low Flow Floodplain Bench Required? Yes The channel width is 12'. Floodplains benches are constructed on both outside barrels to maintain existing low flow channel.
(provide justification)
Bends at Inlet/Outlet? Yes Culvert aligns with the stream. The stream enters at a 71 degree angle.
describe culvert ali nment with stream
Stream Realignment Necessary? (provide No
justification)
Bank Stabilization: Class I rip rap is used to stabilize the disturbed channel banks up to 40 feet upstream and 33 feet downstream of the culvert.
Outlet Velocities
Natural Stream Channel 2-yr Velocity (ft/s): 7.1 Natural Stream Channel 10-yr Velocity (ft/s): 8.3
Proposed Culvert 2-yr Outlet Velocity (ft/s): 7.9 Proposed Culvert 10-yr Outlet Velocity (ft/s): 8.2
Roadway Geometric Considerations
Evaluate/Describe Roadway Geometric Constraints:
Cove Creek runs perpendicular to the roadway under Marion Thomas Rd. (SR 1304). There are mountains along the western bank of Cove Creek.