(A) All stormwater management practices shall be designed to provide protection of life and property from flooding and flood flows. The following standards shall be incorporated into the proposed project:
(1) Post-development peak discharge rates from the 2-, 10-, and 25-year frequency (Type III) storm shall be maintained at or below pre-development rates;
(2) Downstream analysis of the 100-year frequency storm and control of the peak flow for the 100-year storm to mitigate significant downstream impacts; and
(3) Discharge from any stormwater facility must be conveyed through properly constructed watercourses to provide for nonerosive flows during all storm events. The proposed stormwater conveyance system consisting of open channels, pipes and other conveyance devices shall at a minimum accommodate the runoff from a 25-year storm event and shall not increase downstream or off-site flooding, draining, soil, erosion or other runoff related problems to public or private land, facilities, or water resources.
(B) Stormwater management plans shall incorporate best management practices for water quality control as described in the Rhode Island Stormwater Design and Installation Standards Manual, as amended, which in combination are demonstrated to reduce the average annual total suspended solids in post-development runoff by 80%. Development in drinking water supply watersheds may be held to higher standards. The water quality design volume shall be defined as one inch of runoff over all impervious surfaces or 0.4 inches of runoff over pervious areas.
(C) Stormwater management plans shall meet the following standards:
(1) Each lot will be adequately drained;
(2) Natural drainage patterns will be maintained whenever possible;
(3) All existing watercourses will be left open, unless approval to enclose is granted;
(4) All new open watercourses will be seeded, sodded, or protected with stone rip-rap depending on grades and soil types;
(5) A drainage system designed to accommodate flows resulting from up to a 25-year frequency storm will be installed and connected to a defined and approved watercourse; and
(6) All necessary easements to off-site watercourses will be obtained by the applicant, and granted to the Town of Middletown. Easements shall guarantee access to the Town of Middletown to or along any proposed stormwater drainage facility or watercourse and shall guarantee the right to construct, maintain or alter any such facility.
(Ord. passed 2-21-06)