20170848 Ver 1_SW Plan_20170710

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STORMWATER MANAGEMENT PLAN ��''�-��---��
(Version 2.07; Released October 2016) FOR NCDOT PROJECTS
WBS Element: 17BP.11.R.120 TIP No.: SF960403 County�ies): Wilkes Page 1 of 2
General Project Information
WBS Element: 17BP.11.R.120 TIP Number: SF960403 Project Type: Brid e Replacement Date: 12/27/2016
NCDOT Contact: Heath Slaughter (Division Environmental Officer) Contractor I Designer: Wetherill Engineering, Inc./ Dustin D. Creech, PE
Address: Highway Division 11 Address: 1223 Jones Franklin Rd.
801 Statesville Rd Raleigh, NC 27606
North Wilkesboro, 28659
Phone: [phone] Phone:[phone]
Email: hslau hter ncdot. ov Email: dcreech wetherillen .com
CitylTown: Purlear, NC Count ies : Wilkes
River Basin s: Yadkin-Pee Dee CAMA County? No
Wetlands within Project Limits? No
Pro'ect Description
Pro'ect Len th lin. miles or feet : 0.114 Mi. Surrounding Land Use: Rural; Wooded; Mountains
Proposed Pro'ect Existin Site
Pro'ect Built-Upon Area ac. 020 Comb'd Ac for 960403/960700 ac. 0.18 Comb'd Ac for 960403/960700 ac.
Typical Cross Section Description: (2) 7' Paved Lanes with variable width 2'-7' grassed shoulders. (1) 11' wide gravel roadway with variable width grassed shoulders
Annual Avg Daily Traffic (veh/hr/day): Design/Future: Year: Existing: 100 Year: 2016
General Project Narrative: The purpose of this project is to replace the structurally deficient bridge on SR 1302 with a new bridge. The existing bridge consists of a single span (1 @25'-7") with a timber
(Description of Minimization of Water floor on I-beams. Abutments are oriented at approximately a 115 degree skew to the roadway. The existing bridge utilizes vertical abutments. The replacement structure will
Quality Impacts) consist of a double barrel reinforced box culvert (2 @ 11' X 5' RCBC with the leftmost barrel looking downstream buried 1' and the rightmost barrel looking downstream 2' sills).
Efforts were made to minimize water surface impacts by minimizing the length of inlet and outlet channel work.
Waterbody Information
Surface Water Body (1): Little Creek NCDWR Stream Index No.: 12-31-2-4
NCDWR Surface Water Classification for Water Body Primary Classification: Class C
Supplemental Classification: Trout Waters (Tr)
Other Stream Classification: None
Impairments: None
Aquatic T&E Species? No Comments:
NRTR Stream ID: 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 Discharge Over Water Body? N/A (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 justifcation in the General Project Narrative) General Project Narrative)

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,. Highway Stormwater Program �'.
STORMWATER MANAGEMENT PLAN �`"�•-: :=�'
(Version 2.07; Released October 2016) FOR NCDOT PROJECTS
WBS Element: 17BP.11.R.1: TIP No.: SF960403 County(ies): Wilkes Page 2 of 2
Bridge to Culvert Avoidance and Minimization
Proposed Structure Summa
Sheet No. 8� Station Sheet No.: 4 Station: 13+54 -LREV- Number of Barrels: 2
Drainage Area (ac or sq mi): 1.8 Sq. Miles Barrel Width/Diameter (ft): 11
Surface Water Body: 1)Little Creek Barrel Height (ft : 5
Culvert T e: Reinforced Concrete Box Culvert Culvert Len th ft 93
Avoidance and Minimization Efforts: The culvert inverts will be buried 1 foot. Barrel widths were chosen to simulate existing stream base widths. The culvert skew of 152 degrees was
(Bridge to Culvert) chosen to closely match the skew of the existing stream. Originally an alumi�um culvert with sills/baffles was proposed, but was found to incur
excessive impacts to surface waters due to a potentially longer footprint due to skew and the number of segments required. For these reasons, a
RCBC was found to be the best option.
Stream Slope Fish and/or Aquatic Life Passage
Existing Average Stream Slope (%): 3.50 % Existing Low Flow Channel Dimensions 13 Ft. Top width, 11 Ft. - 6 In. base width, 1
Proposed Culvert Slope (%): 3.76 % in the Stream: Ft. - 6 In. depth
Culvert Burial
Proposed Culvert Burial Depth (ft): 1
Existing Streambed Material: Mostly fine sand with approx. 6 in. diamter cobble Proposed Low Flow Dimensions 11 Ft. width
Through the Culvert:
Proposed Sills/Baffles: Leftmost barrel looking downstream buried 1' with 1'
sills at 10.75' centers throughout the culvert for bed Existing Low Flow Velocities in the
material retention and the rightmost barrel looking Stream (ft/s): 1.8 (ADF=2.7CFS)
downstream with 2' sills at the inlet and outlet ropose ow ow e oci ies roug
the Culvert (fUs): 1.6 (ADF=2.7CFS)
Alternating Low Flow Sills/Baffles: N/A
Culvert/Stream Alignment
Stream Patterns Upstream and Downstream Downstream of the proposed culvert is where the existing bridge occurs. The existing bridge will be removed and bank stabilization applied to
of the Culvert that Could Affect Fish stream banks along this portion of the stream reach.
Passage and Bank Stability:
Bed Forms Impacted by Culvert (riffles, The proposed RCBC will occur in a reach of stream that includes a small waterfall. The outlet end of the proposed RCBC occurs at an existing
pools, glides, etc.): pool.
Low Flow Floodplain Bench Required? Yes A bench will be provided in order to incorporate the high flow barrel.
(provide justification)
Bends at Inlet/Outlet? No Approximately 100 Ft. upstream of the inlet and 110 Ft. downstream of the outlet of the proposed RCBC is a naturally occuring
(describe culvert alignment with stream) bend in Little Creek.
Stream Realignment Necessary? (provide No Low flow channel closely matches the existing channel.
justification)
Bank Stabilization: Class 'I' rip rap with geotextile on laid back banks (approximately 40 Ft. upstream and 50 Ft. downstream of culvert)
Outlet Velocities
Natural Stream Channel 2-yr Velocity (fUs): 6.3 Natural Stream Channel 10-yr Velocity (ft/s): 8.7
Proposed Culvert 2-yr Outlet Velocity (ft/s): 5.9 Proposed Culvert 10-yr Outlet Velocity (ft/s): 7.9
Roadway Geometric Considerations
Evaluate/Describe Roadway Geometric Constraints:
The existing road is a dead end road. The proposed roadway alignment was configured to facilitate construction of the proposed RCBCs while maintaining connectivity for local residents. In
addition, the existing topography is mountainous and consideration was given to minimize excessive right of way acquisition.