Infiltration guidelines for potential stormwater hotspots

Infiltration guidelines for potential stormwater hotspots.
Link to this table.

Operational area	Potential infiltration guidelines
Landscaping	Infiltration is acceptable provided there is no run-on or co-mingling from higher pollutant loading areas and appropriate pretreatment is provided for the specified practice. Chemical management is needed to limit the amount of fertilizer and pesticides.
Downspouts	Infiltration is acceptable provided there is no run-on or co-mingling from higher pollutant loading areas, there is no polluting exhaust from a vent or stack deposits on the rooftop, and there is appropriate pretreatment provided for the specific practice.
Vehicle operations	Infiltration is acceptable with the following provisions: No run-on from higher pollutant loading areas Limited salt application or use of alternative deicers Enhanced pretreatment requirements such as (suggested unless better local information is available) minimum vegetative filter lengths of 20 feet, maximum velocity in conveyance channels to infiltration practice of one foot per second, plunge pools and sediment basins/chambers with volumes of at least 25% of the water quality volume Only daily “commuter” parking areas and no long-term car/truck storage sites.
Waste management and outdoor material storage1	Infiltration is typically not recommended but may be utilized if spill prevention and containment measures are in place, such as catch basin inserts and oil and grit separators; or if redundant treatment is provided, such as filtering prior to infiltration. Infiltration should be prohibited in areas of exposed salt and mixed sand/salt storage and processing.
Loading docks1	Infiltration is typically not recommended but may be utilized if spill prevention and containment measures are in place, such as catch basin inserts and oil and grit separators; or if redundant treatment is provided, such as filtering prior to infiltration.
Vehicle fueling1	Infiltration is not allowed under the CGP.
Highways1	Infiltration is possible where enhanced pretreatment is provided. Where highways are within source water protection areas and other sensitive watersheds, additional measures should be in place such as spill prevention and containment measures (e.g., non-clogging catch basin inserts and oil and grit separators.

¹indicates operational area with likelihood of having higher pollutant loadings