§ 14.06.170. Road construction standards—Drainage and culvert material.
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Roads shall be constructed to prevent ponding of runoff waters in roadside ditches.
Drainage ditches shall be constructed such that runoff waters will be conveyed to
natural drainage courses, ditches or waterways, or other man-made drainage courses.
Outfalls shall be constructed to prevent excessive siltation of riparian habitats,
channel erosion, or other damage to public or private property. The RSA board may
require an engineering analysis and design for locations susceptible to flooding,
siltation, or other natural conditions potentially damaging to the right-of-way, adjacent
property, or water courses and water bodies. Pursuant to KPB 14.06.100, the board shall require this engineering analysis and design in the SMFDA and FIRM
area. A roadway cross culvert shall be a minimum diameter of 18 inches, and with at
least a one percent drainage grade through the culvert, and driveway culverts shall
be a minimum of 15 inches and 30 feet in length. Culverts, coupling bands and special
sections shall be corrugated steel pipe of at least 16 gauge. Plastic culverts are
acceptable for driveway culverts only, if they meet AASHTO Standard Section 706-2.07
corrugated polyethylene pipe, AASHTO M 294, Type S. AASHTO cross culvert markers must
be installed.