Pretreatment

From LID SWM Planning and Design Guide
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Overland sheet flow[edit]

The following pretreatements are recommended where sheet flow is being directed to a BMP (typically a bioretention cell) from the edge of an impermeable surface such as an asphalt parking lot or a paved plaza:

A gravel diaphragm typically requires less setback between the catchment and the BMP. Where space permits, these two designs can be used in combination to even greater effect!

Concentrated overland flow[edit]

Where a curb cut, a disconnected downspout or a swale directs surface water to a point, increasing the flow rate, one or more of the following pretreatments should be considered:

Concentrated underground flow[edit]

This type of pretreatement is dominated by proprietary systems, some of which have undergone verification under the Environmental Technology Verification (ETV) program.

Inline pretreatment options
Type Description ETV products Other products (not verified)
OGS Baffles Baffles slow flow, encouraging larger, heavier particles to drop out of the water column. A skimmer may also trap floating debris, oils and grease. - SAFL baffle


OGS Baffles Baffles slow flow, encouraging larger, heavier particles to drop out of the water column. A skimmer may also trap floating debris, oils and grease. - Hydrodynamic OGS The shape causes rapidly flowing water to form a vortex which forces the larger, heavier particles are outwards and downwards into a lower chamber. Floating debris, oils and grease are trapped behind a baffle or in small tank area, towards the top of the main vortex chamber

CDS
Downstream defender
SDD

Stormceptor Cartridge filters Uses membrane technology adopted from water treatment plants. - Jellyfish filter Catchbasin inserts Great for retrofitting situations, to improve water quality CB Shield Snout

External resources[edit]

This article is particularly heavy on proprietary systems and information. Please inform us of any omissions or broken links using the box below: