Current through Register Vol. 48, No. 38, September 20, 2024
a) General Standards for New Bridges and
Culverts
Permits will be granted for new bridges and culverts that would
not result in flood damages or potential flood damages outside the project
right-of-way due to increases in flood heights or velocities. Absent contrary
evidence, this standard will be considered met if, for the worst-case analysis
(see Section
3700.20) :
1) the application shows that:
A) any water surface profile increase would
be contained within the channel banks (or within existing vertical extensions
of the channel banks such as within the design protection grade of existing
levees or floodwalls) or flood easements; or
B) in urban areas, the water surface profile
increase would not exceed 0.5 feet at the structure, nor 0.1 foot at a point
1000 feet upstream of the structure as determined by the horizontal projection
of the increase and the slope of the hydraulic grade line; or
C) in rural areas, the water surface profile
increase would not exceed 1.0 foot at the structure, nor 0.5 feet at a point
1000 feet upstream of the structure as determined by the horizontal projection
of the increase and the slope of the hydraulic grade line; and
2) the application shows that:
A) any increase in average channel velocity
would not be beyond the scour velocity of the predominant soil type of the
channel; or
B) increased scour,
erosion and sedimentation would be prevented by the use of riprap or other
design measures.
b) General Standards for Bridge and Culvert
Reconstruction
A bridge or culvert reconstruction project that would meet the
following provisions will be permissible. A reconstruction project that would
not meet these provisions must either comply with the general standards for new
bridges and culverts or be designed to reduce the induced flood damages to the
fullest practicable extent.
1) The
reconstruction (including approach roads) shall be no more restrictive to
normal and flood flows than the existing bridge or culvert crossing;
and
2) Documentation must be
provided that the existing crossing has not caused demonstrable flood damage.
In the case of public projects, certification by a District Engineer of the
Department of Transportation's Division of Highways, a County Engineer (if a
Professional Engineer), or a Municipal Engineer (if a Professional Engineer)
that the existing crossing has not caused demonstrable flood damage will be
adequate documentation.
