Various parts of the drainage facility must accommodate runoff water as follows:
(A) The drainage system, including inlets, catch basins, street gutters, component swales, storm sewers and small channels, which collect storm water must accommodate peak runoff from at least a 10-year return period storm. The allowable spread of water on collector streets is limited to maintaining 2 clear 10-foot moving lanes of traffic. One lane is to be maintained on local roads and subdivision streets.
(B) For rainfall heavier than a 10-year storm, these minimum requirements must be satisfied:
(1) Open channels carrying peak flows greater than 30 cubic feet per second shall be capable of accommodating peak runoff for a 50-year return period storm within the drainage easement;
(2) New culverts shall be capable of accommodating peak runoff from a 50-year return period storm when crossing under a road which is part of the Indiana Department of Transportation functional classification system and are classified as principal or minor arterial, major or minor collector roads; and
(3) Drainage systems shall have adequate capacity to convey the storm water runoff from all upstream tributary areas through the development under consideration for a storm of 100-year design return period calculated on the basis of the upstream land in its present state of development. An allowance, equivalent to the reduction in flow rate provided, shall be made for upstream detention when the upstream detention and release rates have previously been approved by the Commission and evidence of its construction can be shown. Developer shall be responsible for providing supporting documentation if the town does not have it on file.
(Ord. passed 10-11-2004)