The drainage system shall be designed and constructed to provide for the proper drainage of the subdivision. The following items shall be provided:

    A.    Drainage Report. This report shall address the existing and proposed drainage conditions and shall evaluate the ability of the proposed water course, channels, drainage tiles, farm tiles, storm sewers, culverts and other improvements to handle the run-off. A registered professional engineer or land surveyor shall prepare this report. The report shall include:

    1.    Estimates of the water entering the subdivision;

    2.    Conditions of the watershed that may affect run-off such as subsoil type, positive drainage channels, obstructions and so forth;

    3.    Quantities of flow at each pick-up point, or culvert;

    4.    Description of minor and major drainage systems. The minor system will usually consist of storm sewers, drainage ditches, grassed swales, storm inlets or infiltration structures. The minor system shall be designed to handle a ten-year storm. The major system will usually consist of roadways, culverts, bridges or overflow drainage flow-ways. The major system shall be designed to handle a one-hundred year storm;

    5.    The location of all existing subsurface drainage tiles and a plan to preserve or relocate the tiles;

    6.    Proposals which include detention, retention or infiltration facilities shall include data coordinating field tests with design assumptions and estimates of expected annual maintenance costs.

    B.    Street Drainage System Standards. The streets shall serve as the primary drainage system and be designed to carry at least the street, adjacent land and building stormwater. The following standards shall be followed:

    1.    The system shall consist of curbs, gutters, dry wells and storm sewers. Side ditches and culverts may be used in administrative and agricultural subdivisions.

    2.    For subdivisions with curbs and gutters, drainage inlets shall be spaced and capacity shall be adequate to limit the water onto the street per the design standards specified in Table I, Public Street Design Standards set out in Section 16.24.030.

    3.    For subdivisions without curbs and gutters, the swales, culverts and inlets shall be adequate to accommodate all water during a ten-year storm. For a one-hundred-year storm, all water shall be contained within the right-of-way.

    4.    Bicycle safe protective gratings shall be placed over all inlets.

    5.    Proposals which include detention or retention ponds or infiltration facilities shall include data coordinating field tests with design assumptions and estimates of expected annual maintenance costs.

    6.    All streets having curb and gutter on which stormwater flows across intersections and/or driveways, shall be provided with concrete cross-gutter at such intersections and driveways. (Ord. 99-24 § 3 (part), 1999; prior code § 28-46)