20171428 Ver 1_SW Plan_20171107

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STORMWATER MANAGEMENT PLAN �=^%'
(Version 2.07; Released October 2016) FOR NCDOT PROJECTS
WBS Element: 17BP.3.R.48 TIP No.: County(ies): Onslow Page 1 of 3
General Project Information
WBS Element: 17BP.3.R.48 TIP Number: Project Type: Bridge Replacement Date: 10/11/2017
NCDOT Contact: Robert T. Turnbull, Environmental Services, Inc. Contractor / Designer: HNTB North Carolina, P.C. / John F. Watson, PE
Address: 4901 Trademark Dr. Address: 343 E. Six Forks Road
Raleigh, NC 27610 Suite 200
Ralei h, NC 27609
Phone: [phone] Phone: [phone]
Email: rturnbull esinc.cc Email: 'fwatson hntb.com
Cit ITown: Maysville Count ies : Onslow
River Basin(s): White Oak CAMA County? Yes
Wetlands within Project Limits? Yes
Pro'ect Description
Project Length (lin. miles or feet): 0.13 Surrounding Land Use: Agriculture / Rural
Proposed Pro'ect Existin Site
Pro'ect Built-Upon Area ac. 0.7 ac. 0.3 ac.
Typical Cross Section Description: 2-11' asphalt paved lanes with 2' paved shoulders. Roadside ditches are retained and 2-10' asphalt paved lanes with grassed shoulders. Roadside ditches exist in two
amended in two quadrents with 3:1 slopes. One continues to tie to Gibson Branch, while quadrents. One ties to Gibson Branch, while the other dissipates prior to wetlands
the other dissipates into class'B' rip-rap prior to entering wetlands adjacent to Gibson adjacent to Gibson Branch.
Branch.
Annual Avg Daily Traffic (veh/hr/day): Design/Future: 3400 Year: 2033 Existing: 1700 Year: 2013
General Project Narrative: State project 17BP.3.R.48 involves the replacement of Bridge #660134 on White Oak River Rd. (SR 1331) over Gibson Branch in Onslow County, NC. The existing bridge
(Description of Minimization of Water #660134 consists of 1@ 17'-10°, 1@ 17'-0°, and 1@ 17'-10° spans with reinforced concrete deck on timberjoists and caps. It is to be replaced with a 1@ 45' - 0", 1@ 35' -
Quality Impacts) 0", 21" cored slab bridge (80' total length, 33' total width) at the same location. The project also includes 0.112 miles of roadway improvements on each end of the bridge. The
proposed bridge does not contain deck drains, all storm water from the bridge and approaches will be collected by a storm drainage system and discharged into a Rip-Rap Pad
on the edge of the wetlands in the southeastern quadrent at -L- 18+19 LT.
Only the two southern quadrents contain roadside ditches. Both are impacted by the proposed slope stakes. The proposed ditch in the western quadrent ties to the existing ditch
prior to entering Gibson Branch and passes through a 15" drive pipe. The ditch in the southeastern quadrent outlets into wetlands prior to reaching Gibson Branch. All existing
drainage patterns are maintained in the proposed design with special lateral 'V' ditches, and class 'B' rip-rap is added at the outlet of the southeastern quadrant ditch to dissipate
the concentrated flow.
To facilitate the construction of the proposed bridge, an onsite detour is proposed on the upstream side of White Oak River Rd. The southwestern ditch will be impacted by the
proposed detour and will be designed to dissipate prior to entering Gibson Branch to minimize impacts to the stream.
Waterbody Information
Surface Water Body (1): Gibson Branch NCDWR Stream Index No.: 20-6.5
NCDWR Surface Water Classification for Water Body Primary Classification: Class C
Supplemental Classification: None
Other Stream Classification:
Impairments:
Aquatic T&E Species? Comments:
NRTR Stream ID: Buffer Rules in Effect: N/A
Project Includes Bridge Spanning Water Body? Yes Deck Drains Discharge Over Buffer? No 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)

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STORMWATER MANAGEMENT PLAN —
(Version 2.07; Released October 2016) FOR NCDOT PROJECTS
WBS Element: 17BP.3.R.48 TIP No.: County(ies): Onslow Page 2 of 3
Swales
Station & Coordinates Surface Base Front Back Drainage Recommended Actual Longitudinal Rock BMP
Sheet (Road and Non Road Water Width Slope Slope Area Treatm't Length Length Slope Q2 V2 Q70 V10 Checks Associated w/
No. Projects) Body (ft) (H:1) (H:1) (ac) (ft) (ft) (%) (cfs) (fps) (cfs) (fps) Used BufferRules?
4 -L- 15+00 RT (1)Gibson 0.0 3.0 3.0 0.3 30 100 2.95 % 0.6 1.7 0.8 1.8 No No
34.91258 / -77.27339 Branch
4 -L- 17+Zg LT (1)Gibson 0.0 3.0 3.0 1.4 140 270 1.55 % 3.0 2.0 3.9 2.1 No No
34.91303 / -77.27404 Branch
Additional Comments
Note: All ditch designs replicate existing conditions.

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STORMWATER MANAGEMENT PLAN —
(Version 2.07; Released October 2016) FOR NCDOT PROJECTS
WBS Element: TIP No.: County(ies): Onslow Page 3 of 3
Preformed Scour Holes and Energy Dissipators
Station & Coordinates Drainage Pipe/Structure BMP
Sheet (Road and Non Road Surface Energy Dissipator Area Conveyance Dimensions Q10 V10 Associated w/
No. Projects) Water Body Type Riprap Type (ac) Structure (in) (cfs) (fps) Buffer Rules?
4 -L-18+19 LT (1)Gibson Riprap Energy Class'B' 0.1 Pipe 15 0.3 0.5 N/A
34.91317 / -77.27425 Branch Dissipator Basin
Additional Comments
* Refer to the NCDOT Best Management Practices Toolbox (2014), NCDOT Standards, the Federal Highway Administration (FHWA) Hydraulic Engineering Circular No. 14 (HEC-14), Third Edition, Hydraulic Design of Energy
Uissipators tor Gulverts and Ghannels (July ZUU6), as applicable, tor design gwdance and cnteria.