20170718 Ver 1_D-009_SF-940149_HYD_SMPv2.07_(20170216) (Oct 2016)_20170606

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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-940149 County(ies): Watauga Page 1 of 2
General Project Information
WBS Element: 17BP.11.R.173 TIP Number: SF-940149 Project Type: Bridge Replacement Date: 2/16/2017
NCDOT Contact: Heath Slaughter Contractor / Designer: RK&K - Eleni Riggs, 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: eri s rkk.com
CitylTown: Count ies : Watau a
River Basin s: New CAMA County? No
Wetlands within Project Limits? No
Pro'ect Description
Pro'ect Length (lin. miles or feet : 284 ft 0.054 mi. Surroundin Land Use: Rural
Proposed Pro'ect Existin Site
Pro'ect Built-Upon Area (ac. 0.1 ac. 0.1 ac.
Typical Cross Section Description: 2-lanes at 9' each with 4' shoulders (2' paved and 2' unpaved) 2-lanes at approx. 9' each with 4' wide unpaved shoulders
Annual Avg Daily Traffic (veh/hr/day): Desi n/Future: Year: Existin : 120 Year: 2000
General Project Narrative: This project replaces existing bridge #940149, a 25'-3" single span bridge with a steel I-beam and timber floor superstructure. The proposed replacement structure will be a 24'-
(Description of Minimization of Water 0" x 3'-0" bottomless (3-sided) culvert with wingwalls approximately 61.5' along centerline of culvert. The proposed culvert will have cast-in-place concrete footings founded on
Quality Impacts) rock. The footings will be constructed up to the floodplain bench elevation to alleviate constructability issues. The floodplain bench will be armored along the stream side and
across the top with Class II riprap for stability. The proposed culvert will have 44 LF of inlet improvements and 32 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.
Waterbody Information
Surface Water Body (1): Grassy Creek NCDWR Stream Index No.: 10-1-14
NCDWR Surface Water Classification for Water Body Primary Classification: Water Supply IV (WS-IV)
Supplemental Classification: +
Other Stream Classification:
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? Yes Deck Drains Discharge Over Buffer? N/A Dissipator Pads Provided in Buffer? N/A
Deck Drains Discharge Over Water Body? 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)

High�vay North Carolina Department of Transportation �
Stortnw�ate�r. 1
�,.,��-�..,� Highway Stormwater Program �;%
STORMWATER MANAGEMENT PLAN —
(Version 2.07; Released October 2016) FOR NCDOT PROJECTS
WBS Element: ��BP.�i.R.��3 TIP No.: SF-940149 County(ies): Watauga Page 2 of 2
Bridge to Culvert Avoidance and Minimization
Proposed Structure Summa
Sheet No. & Station Sheet No.: 4 Station: -L- 12+68.4 Number of Barrels: 1
Drainage Area (ac or sq mi): 2.8 Sq. Miles Barrel Width/Diameter (ft): 24
Surface Water Body: 1 Grass Creek Barrel Height ft : 3
Culvert T e: Bottomless 3-Sided Culvert Culvert Len th ft 61.5
Avoidance and Minimization Efforts: The proposed culvert is bottomless to accomodate aquatic passage and wide enough to accomodate normal channel width. The slope is
(Bridge to Culvert) consistent with the existing stream slope and the low flow velocities are minimized. Sills and baffles are not required because the culvert is
bottomless. The length of the Bottomless (3-Sided) Culvert is the minimum required for clear recovery without guardrail that may block flow in
overtopping events and the alignment avoids a significant bend at the inlet.
Stream Slope Fish and/or Aquatic Life Passage
Existing Average Stream Slope (%): 1.16 % Existing Low Flow Channel Dimensions 9'-12' wide from BOB to BOB and 3'-4' deep.
Proposed Culvert Slope (%): 1.16 % in the Stream: Approx. 22' from TOB to TOB with 1:1-2:1
Culvert Burial bank slopes.
Proposed Culvert Burial Depth (ft): N/A
Existing Streambed Material: Rock and Smooth Cobble Proposed Low Flow Dimensions 9'-12' wide from BOB to BOB and 0.75'-1.28'
Through the Culvert: deep. 14'-17' from TOB to TOB with 2:1 bank
Proposed Sills/Baffles: N/A s�opes. Floodplain bench is at top of footing.
Existing Low Flow Velocities in the
Stream (ft/s): 1.3
ropose ow ow e oci ies roug
the Culvert (fUs): � g
Alternating Low Flow Sills/Baffles: N/A
Culvert/Stream Alignment
Stream Patterns Upstream and Downstream The culvert lies in a portion of Grassy Creek where the stream is flowing north. There are several meanders in the stream with the stream
of the Culvert that Could Affect Fish crossing back and forth under the roadway upstream of the project site. The confluence with South Fork New River is downstream of the project
Passage and Bank Stability: site.
Bed Forms Impacted by Culvert (riffles, Stream appears to be at a fairly constant grade. There is exposed bedrock within the streambed several thousand feet upstream of the culvert but
pools, glides, etc.): none present within the limits of construction.
Low Flow Floodplain Bench Required? Yes Excavation is necessary to the top of the culvert footing. Fill is not possible once the culvert is put in place due to the low
(provide justification) clearance.
Bends at Inlet/Outlet? Yes There is a 135° (approx.) turn at the culvert inlet. The turn is completed over a distance of approximately 75 to 90 feet.
(describe culvert alignment with stream)
Stream Realignment Necessary? (provide No
justification)
Bank Stabilization: Class I rip rap is used to stabilize the disturbed channel banks up to 44 feet upstream and 32 feet downstream of the culvert.
Outlet Velocities
Natural Stream Channel 2-yr Velocity (fUs): 5.8 Natural Stream Channel 10-yr Velocity (ft/s): 9.8
Proposed Culvert 2-yr Outlet Velocity (ft/s): 4.0 Proposed Culvert 10-yr Outlet Velocity (ft/s): 7.6
Roadway Geometric Considerations
Evaluate/Describe Roadway Geometric Constraints:
This roadway section closely borders mountains on its northeastern corner. Grassy Creek runs parallel to the roadway on the southeastern corner.