The same information as required in § 158.049 is required for properties larger than five acres, or with a tributary area larger than five acres, along with the following additional information for the minor drainage system's design runoff event and the 100-year runoff event of critical duration:
(A) Elevations and maps of 100-year flooding;
(B) Cross-section data for open channel flow paths and designated overland flow paths;
(C) Direction of storm flows;
(D) Flow rates and velocities at representative points in the drainage system; and
(E) A statement by the design engineer of the drainage system's provisions for handling events greater than the 100-year's runoff.
(F) The village reserves the right to request that the IDNR-OWR review all drainage plan submittals.
(G) Area of inundation exhibit showing affected areas due to storm sewer failure
(H) Minimization of increases in runoff volumes and rates. In the selection of a drainage plan for a development, the applicant shall evaluate and implement, where practicable, site design features that minimize the increase in runoff volumes and rates from the site. The applicant's drainage plan submittal shall include evaluations of site design features that are consistent with the following hierarchy:
(1) Minimize impervious surfaces on the property, consistent with the needs of the project;
(2) Attenuate flows by use of open vegetated swales and natural depressions and preserve existing natural stream channels;
(3) Infiltrate runoff on-site;
(4) Provide stormwater retention structures;
(5) Provide stormwater detention structures; and
(6) Construct storm sewers. In developments where the village requires the installation of curb and gutter, storm sewers are preferred. The village may also modify the above hierarchy as required based on an evaluation of the site conditions.
(Ord. 04-02, § 158.013.02, passed 4-5-04)