(A) The Division of Highways shall review all drainage prior to acceptance of any facility to the state system. Drainage, utility or public easements, are not considered a portion of the highway facility.
(B) All storm drainage shall be adequate so that the road may be maintained without excessive cost and not cause flooding on private property from storm runoff of the design frequency. Permanent drainage easements may be established by the designer; however, the NCDOT does not accept maintenance responsibility for the easement outside of the roadway right-of-way. The minimum design frequency shall be as follows but may be increased at the recommendation of the State Hydraulics Engineer.
Cross drainage for secondary routes | 25 years |
Cross drainage on primary and N.C. routes | 50 years |
Minimum cross pipe diameter | 18" |
Minimum driveway pipes diameter | 15" |
Storm sewer collector | 10 years |
All drainage shall be consistent with criteria found in NCDOT's Guidelines for Drainage Studies and Hydraulic Design. (Contact Special Services Section (919) 250-4128.) | |
(C) In areas where ditch grades or quantities of flow deem it impracticable to establish and maintain vegetation, an erosive resistant lining such as paving, matting or rip rap may be required.
(D) Subsurface drainage shall be adequate to maintain a stable subgrade.
(E) When road crossings are within areas designated as flood hazard areas under the Federal Flood Insurance Program, the design must be approved by the responsible local governing agency for its consistency with local flood zoning ordinances. Retention/detention basin shall be located outside the right-of-way and shown on plans where possible. The DOT assumes no responsibility for maintenance nor liability of the basins.
(Ord. passed 1-1-2000)