All applicants for qualifying development activity must develop and submit a proposed stormwater management plan which must address post-construction stormwater management for the development which meets all the requirements of this article. All such stormwater management shall be consistent with the Rhode Island Stormwater Design and Installation Standards Manual and the Rhode Island Soil Erosion and Sediment Control Handbook, as amended. The stormwater management plan must include a description of proposed best management practices (BMPs), detailed site plans, and a written narrative that, when implemented, provides protection of receiving waters by reducing pollutant loadings and other negative impacts associated with changes in land use as described below. Structural BMPs are described as structural stormwater devices that temporarily detain and treat stormwater runoff in order to reduce pollutant loadings. Typical BMPs include wet ponds, extended detention ponds, infiltration trenches, created wetlands, grassed swales and the like.
A. Performance standards. Stormwater management plans must incorporate best management practices for water quality control, 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 or watersheds where impaired waters as defined by the state’s 303(d) list exist may be held to higher standards.
B. Disallowed stormwater best management practices. The placement of structural BMPs and other stormwater structures within a floodplain shall be avoided. If there is no alternative, the applicant must show what effects, if any, the tail waters created by the floodplain will have on the outflow and effective storage capacity of the detention facility.
C. Facilitation of maintenance. Facilities that require maintenance shall be designed to minimize the need for regular maintenance, facilitate required maintenance, and ensure accessibility of components that require maintenance. At a minimum, all stormwater management plans must incorporate structural BMPs with appropriate maintenance design in accordance with the Rhode Island Stormwater Design and Installation Standards Manual, as amended; or the Rhode Island Soil Erosion and Sediment Control Handbook, as amended.