§ 23-136. Grades.

(a)

Grades shall be approved by the Director in accordance with the relevant specifications of the American Association of State Highway and Transportation Officials (AASHTO), as amended, and with the following:

(1)

No grade shall be less than one percent (1%) or more than ten percent (10%) except under extraordinary circumstances, as determined by the Director.

(2)

Where roads are constructed with concrete curb and gutter, a minimum of one and one-half percent (1.5%) grade will be required through the intersection of intersecting roads.

(3)

Where roads are constructed without curb and gutter, the minimum street grade shall be two percent (2%). Where a street grade of less than two percent (2%) is used, ditches shall have positive drainage.

(4)

All new roads shall be constructed to remain passable during a 100-year flood event along any adjacent or nearby watercourse having a watershed of fifty (50) acres or more. The determination of the 100-year flood level with respect to the roadway for purposes of this Subsection shall include the effects of the roadway itself and any appurtenant structures and adjacent or nearby developments, but not the effects of partial or complete blockage of the approved drainage systems or structures. Exceptions to this requirement may be allowed at the discretion of the Director when:

(A)

The watercourse is to be conveyed in an approved storm drain system running along the right-of-way and depending on the roadway as the overflow path for storms in excess of the 10-year storm, provided the watershed area does not exceed four hundred (400) acres, and provided that the Department approves the resultant 100-year floodway with respect to affected properties; or

(B)

The roadway must be constructed to a lower elevation in order to serve existing development or to connect with an existing publicly maintained road, provided the extent of the lowering is the minimum practicable while meeting the requirements of paragraphs (1), (2), and (3) of this Subsection; or

(C)

The roadway would be overtopped solely by reason of computed flood elevations and flow routing resulting from assumed partial or complete blockage of the approved drainage systems or structures;

(D)

The roadway is a private road, right-of-way, or easement serving no more than four (4) lots or dwelling units.

(CB-98-1989; CB-18-2013)