Decision process for selecting liners

Design process for selecting the appropriate liner level.
Link to this table

Condition	Design level	Note
Filtration BMP with less than 3 feet of separation to seasonal saturated soil or bedrock	1	Required under the Construction Stormwater permit
BMP in confirmed potential stormwater hotspot with high or very high groundwater pollution potential	1	Applies to all post-construction BMPs. See section on Potential stormwater hotspots for more information
Constructed ponds with less than 3 feet separation from seasonally high water table in a potential hotspot	1
Constructed wet ponds underlain by soils with an infiltration rate of 0.3 inches per hour or greater (HSG A or B soils)(see [1] or [2])	1	To maintain a permanent pool
Karst terrain with high or very high groundwater pollution potential	1	See section on karst for more information
Prevent groundwater intrusion into a BMP requiring aerobic conditions, such as iron-enhanced media	1
Maintain permanent pool in constructed ponds or constructed wetlands in areas underlain by geologic material that is fractured or has a high infiltration rate	2
Separation distance from a BMP cannot be achieved	2
Separate tree BMP from road, parking lot, sidewalk or adjacent walls or building foundation	2	To prevent tree root intrusion. See link