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Home My WebLink About20171100 Ver 1_170808 Environmental Permitting Narrative_20170831TO: CC: FROM: DATE: SU BJ ECT: � i � • ll 1L • : G \ � 11 NC Department of Transportation — Division 1 David L. Clegg, County Manager, Tyrrell County Dan Withers, PE August 8, 2017 Tyrrell County—SR1209 Drainage Improvements Permitting Narrative ENGINEERS PLANNERS SURVEYORS LANDSCAPE ARCHITECTS NCBELS LIC. N0. F-0334 ��uui�� .�`��H CARp''�. ; �O oFEssip;��j,9 ; ; QQ� 9{ ,� : _ SEAL ��.��t� = 38746 =� . •.t�^,G 1 NE�Q' � l�� , r/�r .... �`.��, . , ''��, R„��``� The purpose of this memorandum is to document permitting requirements for a culvert replacement and roadway improvements at the crossing of SR1209 (North Road Street) and North Boundary Canal, located north of Columbia in Tyrrell County, North Carolina. The roadway section is to be raised approximately 18" above the existing roadway elevation at the culvert crossing. The roadway profile will then taper back to the existing roadway at between 0.30% and 0.38% grade in line with the roadway. The existing 36" CMP culvert will be replaced with a 16' wide, 4'-3" tall, 40' long corrugated aluminum box culvert. This culvert is in excess of the prescribed hydraulic design and has been sized to maximize the size of the culvert beneath the proposed roadway section. The existing drainage currently flows directly to the canal via sheetflow across turf or paved surfaces or via curb and gutter. Due to the change in grade of the proposed roadway, a series of catch basins, drop inlets, additional curb and gutter, and drainage piping is proposed to maintain the same drainage area flowing directly to the canal. Stormwater Mana�ement The project has been designed in accordance with NCDOT Post-Construction Stormwater Program requirements. Because this project is a roadway project, Appendix A workflows were followed: • The project is a roadway project. • It is located in a Coastal County. • The additional BUA does not disturb more than one acre (the only additional BUA is approximately 130 linear feet of 4' sidewalk). • The project does change the way stormwater is conveyed. • The project does not remove an existing Toolbox BMP. � Section 2.2 and 2.3 minimum measures have been implemented. The following is a list of the minimum measures that have been implemented on the project: • The proposed backslopes from the proposed curb and gutter are primarily turf or washed stone (in the case of a large existing parking area). • The proposed roadway slope and roadside slopes have been minimized to the greatest extent practical. 8/8/2017 Memorandum Tyrrell County — SR1209 Drainage Improvements Permitting Narrative Page 2/2 • By rerouting portions of the drainage system, some existing erosion will be stabilized. Currently the curb and gutter drains directly to the canal and there is some erosion at the outfall. The proposed drainage system minimizes the potential for erosion in this manner. • By discharging the piped network directly to connections in the culvert and below the normal water level, the need for energy dissipation at the piping discharge is eliminated. • To the extent practical, vegetated conveyance for the roadway backslope and adjacent lawns has been maintained. • The direct discharge from the culvert crossing has been re-routed such that it flows circuitously through a piping system, avoiding direct discharge direction from the pavement section over the canal. Traditional stormwater BMP's are not practical on this project due to a range of conditions: • There is limited right of way available. • Even with an increase of 18" in roadway profile, there is still not adequate vertical relief in the hydraulic system to allow for placement of a BMP. • Due to the minimum depth of drainage boxes, the piping networl<will be below the normal surface elevation ofthe canal. Thus, infiltration is not practical. 401 Water Qualitv Certification This project falls under Water Quality General Certification No. 4088 (http://edocs.deq.nc.�ov/WaterResources/DocView.aspx?dbid=0&id=493430&pa�e=1&cr=1) and Regional General Permit No. 198200031 (http://www.saw.usace.armv.mil/Portals/59/docs/re�ulatory/re�docs/Permits/Fina12015-04-30-RGP31- si�ned.pdf) because the project does not result in a loss of waters of the U.S. in excess of 500 linear feet of stream or one acre of wetland/non-tidal open water. A PCN appears to be required from the Corps and written approval for a 401 Water Quality Certification appears to be required from the Division of Water Resources. CAMA Permit This project should be eligible for a CAMA General Permit in accordance with Section .2300 of 15A NCAC 07H because this project consists of "demolition, removal, and replacement of existing bridges and culverts along the existing alignment" and appears to meet the General and Specific Conditions listed in .2304 and .2305. Erosion & Sedimentation Control This project disturbs less than one acre and does not require a permit under North Carolina Sedimentation Control or Stormwater Control law. However, the project has been designed to comply with the provisions of the North Carolina Sediment Pollution Control Act of 1973, the North Carolina Erosion and Sediment Control Planning and Design Manual, and the North Carolina Department of Transportation Erosion & Sediment Control Design and Construction Manual.