Water may be released through designed outfall or overflow structures.

Structure is protected with curbs or other barrier devices where appropriate.

Natural, freeform design is preferable.

Detailed grading plan to establish shape and grades of the structures.

Cross sections of weirs, dams, outlet structures, subdrainage, and spillways.

Specifications for filter sands, soil additives, clay or fabric liners, and temporary erosion control.

Setbacks and side slopes that allow for driver recovery of errant vehicles.

Side slopes are designed for maintenance activities (mowing), see ;

Appropriate vegetation for the pond use.

Designed to provide flood control, remove silt and pollutants, and protect downstream water bodies.

Rain gardens and biofiltration ponds should be designed so that water is held for no longer than 48-72 hours. Otherwise, the pond could develop nuisance conditions where mosquitos can breed.

Typically used for smaller drainage areas (less than 1 acre). See .

Biofiltration Ponds typically have drainage areas larger than one acre.

Used for retention and/or infiltration, and typically less than 12” depth.

With infiltration-type rain gardens, water flows in slowly and is not released, but instead percolates into the groundwater through porous soils.

In locations with native clay soil, the water quality facility must incorporate an underdrain.

Vegetation may be comprised of turf and/or other plant material but is always specifically selected for periodic inundation.

Appropriate substrate for the region is utilized for the rain garden base.

Used as conveyance, with vegetation filtering and slowing runoff.

Aligned to drain to a specific location.

Vegetation suitable for variable flow rates, as well as periodic inundation.

Side slopes designed for periodic maintenance.

Utilize an approved channel lining material.