STORMWATER BMP SELECTION RECOMMENDATIONS

Unlike roads, trail networks are not usually directly connected impervious surfaces and thus trails have a reduced effect on runoff rates and volumes in highly developed areas.

Trails create the opportunity to manage stormwater sustainably and improve water quality within communities if appropriate stormwater BMPs are used. In general, stormwater BMPs should be selected with an eye on optimizing effectiveness, economy, and required maintenance burden. As outlined below, BMP selections are identified within the context of greenway features. As stand alone items, BMPs listed below recommended for the associated situation. However, where opportunity allows, larger regional BMPs are more easily maintained and less likely to have problems, and should be considered in lieu of multiple stand alone BMPs.

BMP SELECTION MATRIX
SITUATION	STRATEGY	COMMENTS	IMAGE
TRAIL (UNDER 5% SLOPE)	Amended soils	Requires min 10’ width and min 2% cross slope to adjacent BMP
TRAIL (OVER 5% SLOPE)	Preferred: Swale to regional bioretention area
	Bioretention area near trail
NODES UNDER 1000 SF	Amended soils
PARKING	Permeable parking stalls
TRAIL WITH LESS THAN 10’ AVAILABLE FOR AMENDED SOIL	Preferred: Pipe or swale to large scale raingarden	Min 2% cross slope to adjacent BMP
	Curbside/ trailside bioretention	Consider utilizing in areas near intersections and nodes, or in more urban environments.
	Subterranean (Silva Cell/ tree well BMP)
SHELTER/ RESTROOMS	Roof to raingarden
NODES OVER 1000 SF	Preferred: Permeable pavement	Option 2 bioretention/rain garden in design