20171062 Ver 1_SW Plan_20170824 (2)

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_.. Highway Stormwater Program .��'
STORMWATER MANAGEMENT PLAN _
(Version 2.07; Released October 2016) FOR NCDOT PROJECTS
WBS Element: 176P.8.R.124 TIP No.: SF-180094 County(ies): Chatham Page 1 of 1
General Project Information
WBS Element: 17BP.8.R.124 TIP Number: SF-180094 Project Type: Bridge Replacement Date: 5/31/2017
NCDOT Contact: Matthew Lauffer, PE Contractor / Designer: Trenton Cormier, PE
Address: NCDOT Hydraulics Unit Address: ICA Engineering, Inc.
1590 Mail Services Unit 5121 Kingdom Way, Suite 100
Raleigh, NC 27560 Raleigh, NC 27607
Phone: [phone] Phone: [phone]
Email: mslauffer@ncdot. ov Email: [e-mail]
City/Town: Pittsboro County ies : Chatham
River Basin(s): Cape Fear CAMA County? No
Wetlands within Project Limits? Yes
Pro'ect Description
Project Length lin. miles or feet): 730 feet (0.138 miles) 5urrounding Land Use: Wooded, Low Residential
Proposed Project Existing Site
Project Built-Upon Area ac.) 0.4 ac. 0.4 ac.
Typical Cross Section Description: Old Graham Rd (SR 1520): 2 paved lanes (total 22' wide), 3' paved shoulder on each Old Graham Rd (SR 1520): 2 paved lanes (total 18' wide), 6' unpaved shoulder on
side (7' shoulder with guardrail). each side.
Annual Avg Daily Traffic (veh/hr/day): Design/Future: 660 Year: 2018 Existing: 460 Year: 2010
General Project Narrative: The North Carolina Department of Transportation (NCDOT) has proposed to replace Chatham County Bridge #94 on Old Graham Rd (SR 1520) over Dry Creek. The existing
(Description of Minimization of Water structure is a three span bridge (1 @30'-4", 1@30', 1@30'-4") and is a steel plank deck on I-Beams supported by timber caps on timber piles encased in concrete for the interior
Quality Impacts) and end bents. The proposed structure is a single span (1@100'), 39" box beam with 4' deep caps. This structure has been designed to have as little environmental and surface
water impacts as possible. There are no wetland impacts. The exisiting concrete sills along the banks will be retained to minimize the impacts to the bank of the channel
underneath the bridge.
To avoid direct discharge of bridge storm water into the receiving water, deck drains are not required for the proposed bridge. Storm water impacts to the stream have been
minimized by utilizing grated inlets and pipes to collect bridge storm water and use rip rap outlet protection at 14+77 LT to dissipate energy to provide a diffuse flow (non-erosive
sheet flow). This diffuse flow will run for a distance of 15'+/- in a wooded area before entering the buffer. At the same (NW ) quadrant an existing roadside ditch has outlet at
16+35 LT with a non-erosive outlet velocity. This diffuse flow runs for a distance of 165'+/- in the wooded area before entering the buffer. This ditch will be retained. At the NE
quadrant an existing roadside ditch has outlet at 15+15 RT with a non-erosive outlet velocity. This diffuse flow runs for a distance of 45'+/- in a wooded area before entering the
buffer. This ditch will be retained. At the SE quadrant, an existing roadside ditch has outlet at 13+35 RT with a non-erosive outlet velocity. This diffuse flow runs for a distance of
20'+/- in a wooded before entering buffer zone 1. This ditch will be retained and lined with toe protection along the fill slope. At the SW quadrant an existing roadside ditch has
outlet at 11+85 LT with a non-erosive outlet velocity. This diffuse flow runs for a distance of 155'+/- in a pasture area before entering the buffer. This ditch will be retained. Due to
the nature of low impact bridge replacement, the increases in stormwater discharges (post vs pre condition) are insignificant and the existing ditches do not need to be modified.
Therefore, additional stormwater measures are not required.
Waterbody Information
Surface Water Body (1): Dry Creek NCDWR Stream Index No.: 16-34-(0.7)
NCDWR 5urface Water Classification for Water Body Prirriary Classification: Water Supply IV (WS-IV)
5upplemental Classification: Nutrient Sensitive Waters NSW
Other Stream Classification: None
Impairments: None
Aquatic T&E Species? No Comments:
NRTR Stream ID: Buffer Rules in Effect: Jordan Lake
Project Includes Bridge Spanning Water Bod ? Yes Deck Drains Discharge Over Buffer? No Dissipator Pads Provided in Buffer? No
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)