(a) An adequate storm drainage system shall be provided for all below-grade truck loading areas and parking lots in excess of eight thousand (8,000) square feet. For the purpose of square footage computation, all parking areas, access lines and truck loading areas on the same lot shall be considered as a contiguous total square footage.
(b) The design of a Storm Water Drainage system shall be prepared by using Rational method and shall be based on a minimum five (5) year frequency. Rainfall intensity, run-off coefficients and concentration time used in computing flows and structure sizes shall be in accordance with the tables, charts, and data in the Village Storm Water Management Plan and shall be subject to approval by the Village Engineer and conform to all Lake County regulations. All areas which contribute storm water to the proposed storm drainage system shall be considered on the determination of the sizes of pipe, structures, and channels.
(1) Drainage plans shall be accompanied by two (2) copies of the design computations. Hydraulic gradient checks for less frequent storms may also be required by the Village Engineer were deemed appropriate.
(2) Culvert sizes shall be based on a minimum ten (10) year frequency rainfall, or other less frequency storms or greater number of years, or other more stringent methodology as required by the Village Engineer where deemed appropriate.
(3) Detention ponds or basins shall be provided where necessary to control the volume and velocity of storm water leaving the site. Detention ponds and basins shall be designed in accordance with master watershed drainage plans. Where such plans do not exist, facilities shall be based on criteria established by the Village Engineer and approved by the Lake County Soil and Water Department.
(Ord. 19-10. Passed 11-7-19.)