Kenai Peninsula Borough, AK Environmental Rules: Stormwater Management (2026)

In the Kenai Peninsula Borough outside the cities, drainage requirements apply mainly to roads accepted for borough maintenance and to subdivision development, not to general private-lot stormwater. KPB 14.06.170 requires that roads be constructed to prevent ponding of runoff in roadside ditches, with ditches built to convey runoff to natural drainage courses, ditches, waterways, or man-made drainage courses. Outfalls must be built to avoid excessive siltation of riparian habitat, channel erosion, or damage to public or private property. Where a location is susceptible to flooding or siltation, the road service area (RSA) board may require an engineered drainage analysis and design, and under KPB 14.06.100 the board must require that analysis in the SMFDA and FIRM area.

Cross-culverts on borough roads must be at least 18 inches in diameter with at least a one percent drainage grade, and driveway culverts must be at least 15 inches in diameter and 30 feet long, built of corrugated steel pipe of at least 16 gauge (KPB 14.06.170). Separately, several adopted Local Option Zoning Districts carry their own drainage language: for example, the R-1, R-2, R-R, R-W, and R-M district development standards each state that 'existing natural drainage ways shall be retained' (KPB 21.44.160(C)(5) and parallel provisions), but that rule only binds a lot inside an adopted district with that standard, not the borough generally.