§ 16.36.110. Tract drainage.

A.

Improvement plans for drainage facilities to control drainage water generated within a land division shall be approved by the flood control and water conservation district and transportation department.

B.

In land divisions where lot grading is not proposed, the following criteria are established:

1.

Where land division streets on sustained gradients cross natural drainage courses, adequate culverts shall be provided to accommodate the one hundred (100) year storm with maximum ponding to an elevation two feet below the road centerline profile grade, provided diversion of ponded water into another drainage area will not result therefrom.

2.

Runoff in natural drainage courses exceeding the one hundred (100) year storm may be permitted to overtop the roadway in dip sections where, in the opinion of the director of transportation, topography, soil conditions, adjacent development and available all-weather routes indicate its feasibility. If a deep section is permitted, the roadway embankment slopes shall be adequately protected.

3.

Culverts of adequate size, but not less than eighteen (18) inches in diameter or equal, to prevent the one hundred (100) year storm from overtopping the roadway shall be provided in dip section or as approved by the director of transportation. Smaller culverts may be approved by the director of transportation.

4.

Streets crossing improved channels shall be provided with culverts of adequate size to permit passage of the channel design flow or such other type of crossing as approved by the appropriate flood control agency and the Director of Transportation.

5.

Asphalt concrete for lining of channels shall not be permitted.

6.

When a land division substantially changes, concentrates or increases the natural flow of surface water onto adjacent property, facilities shall be required to direct the water to an adequate outlet, or the land divider shall obtain a recordable easement or written agreement for drainage purposes across the affected property.

(Ord. 460.137 § 11.3, 1997)