20160905 Ver 1_Bridge 600061 Mitchel SMP_20160921

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,, . .. Highway Stormwater Program �'
STORMWATER MANAGEMENT PLAN
(Version 2.06; Released June 2016) FOR NCDOT PROJECTS
WBS Element: 176P.13.R.144 TIP No.: County(ies): Mitchell Page 1 of 2
General Project Information
WBS Element: 17BP.13.R.144 TIP Number: Project T pe: Brid e Replacement Date: 6/27/2016
NCDOT Contact: Paul F. Fisher, P.E. Contractor / Designer: Desi ner (Scott Homewood) - Mattern & Crai Consultin Engineers
Address: Hydraulics Unit Address: 12 Broad Street
1020 Birch Ridge Road Asheville, N.C. 28801
Ralei h, 27610
Phone: [phone] Phone: [phone]
Email: pfisher ncdot. ov Emaii: mshomewoodna matternandcraip.com
Cit ITown: Spruce Pine Count ies : Mitchell
River Basin(s): French Broad CAMA County? No
Wetlands within Project Limits? No
Pro'ect Description
Project Length (lin. miles or feet): 272 linear feet Surrounding Land Use: Woods / Open Grass Land
Proposed Pro'ect Existin Site
Pro'ect Built-Upon Area (ac. 0.1 ac. 0.1 ac.
Typical Cross Section Description: The approaches to the proposed culvert will be 18-foot pavement width providing two 9- The existing paved approaches are approximately 13.0' wide provideingone 13.0' lane
foot lanes and one foot grassed shoulders on each side. with one foot grassed shoulders.
Annual Avg Daily Traffic (veh/hr/day): Desi n/Future: 900 Year: 2025 Existin : 450 Year: 1997
General Project Narrative: The purpose of this project is to replace Bridge No. 600061 on SR1172(Patrick Phillips Rd) over Snow Creek in Mitchelll County. The Existing bridge is a two span 41' timber
(Description of Minimization of Water bridge on I-Beams. The replacement structure will be a three sided box culvert with a 40' span. The roadway alignment and grade of the new structure will be revised stighly to
Quality Impacts) accomidate proper vertical and horizontal curves. The Storm drainage will sheet flow off roadway and is collected into vegetated ditches and diffused over rip-rap at the proposed
culvert inlet and outlet. Runoff from the culvert deck will be discharged at the culvert ends and will not be directly discharged to Snow Creek.
Waterbod Information
Surface Water Bod 1: Snow Creek NCDWR Stream Index No.: 7-2-47
NCDWR Surface Water Classification for Water Body Primary Classification: Class C
Su lemental Classification: Trout Waters Tr
Other Stream Classification: None
Im airments: None
A uatic T&E S ecies? No Comments:
NRTR Stream ID: Buffer Rules in Effect: N/A
Pro'ect Includes Brid e S annin Water Bod ? No Deck Drains Dischar e Over Buffer? N/A Dissi ator Pads Provided in Buffer? N/A
Deck Drains Dischar e Over Water Bod ? N/A Qf yes, provide justification in the General Project Narrative) Qf yes, describe in the General Project Narrative; if no, justify in the
(If yes, provide justification in the General Project Narrative) General Project Narrative)

][j�f ��� ���� North Carolina Department of Transportation
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Highway Stormwater Program �
STORMWATER MANAGEMENT PLAN -
(Version 2.06; Released June 2016) FOR NCDOT PROJECTS
WBS Element: 17BP.13.R.1� TIP No.: County(ies): Mitchell Page 2 of 2
Bridge to Culvert Avoidance and Minimization
Proposed tructure ummary
Sheet No. 8� Station Sheet No.: 4 Station: Number of Barrels: 1
Drainage Area (ac or sq mi): 4.5 sq. mi. Barrel Width/Diameter (ft): 40'-0"
Surface Water Body: (1)Snow Creek Barrel Height (ft): 7'-0"
Culvert T e: Three-sided concrete box culvert Culvert Length (ft) 31'-4"
Avoidance and Minimization Efforts: Culvert is designed to minimize stream impact by being the minimum length to provide an adequate roadway cross section and by placement at or
(Bridge to Culvert) near natural streeam alignment. A three-sided (bottomless) box culvert was selected to further minimize impacts to streambed and existing flow
channel.
Stream Slope Fish and/or Aquatic Life Passa e
Existing Average Stream Slope (%): 3.86 % Existing Low Flow Channel Dimensions Approximately 20'
Proposed Culvert Slope (%): 3.86 % in the Stream:
Culvert Burial
Proposed Culvert Burial Depth (ft): N/A - bottomless
Existing Streambed Material: Cobble and gravel with some coarse sand Proposed Low Flow Dimensions Approximately 20'
Through the Culvert:
Proposed Sills/Baffles: Proposed culvert has no bottom (three-sided box
culvert) and will therefore preserve existing xisting ow ow e ocities in t e
streambed and channel. Stream (fUs): 6.11 (Q2)
ropose ow ow e oa ies roug
the Culvert (ft/s): 6.11 (Q2)
Alternating Low Flow Sills/Baffles: Bottomless culvert - no baffles proposed
Culvert/Stream Alignment
Stream Patterns Upstream and Stream has existing bends upstream and downstream of existing/proposed location. No impact to fish passage or bank stability is anticipated due
Downstream of the Culvert that Could to use of three-sided box culvert.
Affect Fish Passage and Bank Stability:
Bed Forms Impacted by Culvert (riffles, No bed forms are expected to be impacted
pools, glides, etc.):
Low Flow Floodplain Bench Required? No Three-sided box culvert preserves existing streambed and flow channel
(provide justification)
Sharp Bends at Inlet/Outlet? No Culvert is aligned with stream
describe culvert ali nment with stream
Stream Realignment Necessary? (provide No
justification)
Bank Stabilization: Streambanks to be stabilized with Class II rip rap for approximately 30 feet up and down sterem from culvert
Outlet Velocities
Natural Stream Channel 2-yr Velocity (ft/s): 6.2 Natural Stream Channel 10-yr Velocity (ft/s): 8.7
Proposed Culvert 2-yr Outlet Velocity (ft/s): 6.1 Proposed Culvert 10-yr Outlet Velocity (ft/s): 8.5
Roadway Geometric Considerations
Evaluate/Describe Roadway Geometric Constraints:
The roadway alignment and grade of the new structure will be revised stighly to accomidate proper vertical and horizontal curves.