§ 1010. Stormwater Management

A. Stormwater Management System. The stormwater management system may be comprised of both structural and non-structural elements. Appropriate structural elements include the Best Management Practices (BMPs) described in the RI Stormwater Design and Installations Manual (RI Stormwater Manual) and the associated conveyance system. Low Impact Design (LID) site planning and design elements (see Subsection D. below) that mitigate pollution, reduce sedimentation, provide visual amenities and provide wildlife habitat shall be utilized over structural elements, unless waived by the Planning Board due to the characteristics of the site and/or the proposed development, and based upon evidence submitted to the Planning Board by an appropriate professional (engineer, land surveyor, landscape architect).

B. Stormwater Calculation Methodology. Where a stormwater management plan and run-off calculations are required they shall be prepared by a registered professional engineer or landscape architect, as qualified. The stormwater calculations, runoff rates and system design shall be based upon the methods established in the RI Stormwater Manual.

C. Stormwater Management Requirements. The stormwater management plan shall further indicate how the following specific requirements will be met:

1. That each lot will be adequately drained;

2. That natural drainage patterns will be maintained whenever possible;

3. That all existing watercourses will be left open unless approval to enclose is granted by the Planning Board;

4. That all new open watercourses will be seeded or sodded, depending on grades and soil types;

5. That the water quality of any receiving water, particularly the salt pond, will be protected through use of BMPs;

6. That provisions for continuing future maintenance and repair shall be provided to, and approved by, the Planning Board; and

7. That all necessary easements to off-street watercourses will be obtained by the developer.

D. Design Requirements.

1. LID site planning and design strategies shall be used to the maximum extent practicable in order to reduce the generation of the water run-off volume, as follows:

a. Maximum protection of undisturbed open space in order to maintain pre-development hydrology and allow natural infiltration;

b. Maximum protection of natural drainage areas, streams, surface waters, wetlands and other regulated areas;

c. Minimize land disturbance, including clearing and grading, and avoid areas susceptible to erosion and sediment loss;

d. Minimize soil compaction and restore soils compacted as a result of construction activities;

e. Provide low maintenance, native vegetation that encourages retention and minimizes use of lawns, fertilizers and pesticides;

f. Minimize impervious surfaces;

g. Minimize the decrease in the time it takes run-off to travel from the hydraulically most distant point of the drainage area to the point of interest within a watershed;

h. Infiltrate precipitation as close as possible to the point it reaches the ground using vegetated conveyance and treatment systems;

i. Break-up or disconnect the flow of run-off over impervious surfaces; and

j. Provide source controls to prevent or minimize the use or exposure of pollutants into stormwater run-off at the site in order to prevent or minimize the release of those pollutants into the run-off.

2. Stormwater should be recharged within the same subwatershed to the maximum extent possible.

3. Open drainage and pipe conveyance systems must be designed to provide adequate passage for flows leading to, from and through stormwater management facilities for at least the peak flow from the 10-year 24 hour Type III design storm event.

4. The proposed drainage system shall be designed to accommodate stormwater so that post construction conditions do not result in peak run-off increases in rate or volume from pre-construction conditions.

F. Constructions Standards. Where storm drainage systems are required, their construction and installation shall conform to the specifications set forth in the Town of New Shoreham Utilities Standards Section C.