Comparative BMP phosphorus removal

General summary of comparative BMP phosphorus removal performance^a,e,f

BMP Group	BMP Design Variation	Average TP Removal Rateb	Maximum TP Removal Ratec	Average Soluble P Removal Ratedg
Bioretention	Underdrain	50%	65%	60%
	Infiltration	100	100	100
Filtration	Media Filter	50	55	0
	Vegetative Filters (dry)	0	55	0
	Wet Swale	0	40	0
Infiltrationf,i	Infiltration Trench	100	100	100
	Infiltration Basin	100	100	100
Stormwater Ponds	Wet Pond	50	75	70
	Multiple Pond	60	75	75
Stormwater Wetlands	Shallow Wetland	40	55	50
	Pond/Wetland	55	75	65

^{a Removal rates shown in table are a composite of five sources: ASCE/EPA International BMP Database; Caraco (CWP), 2001; MDE, 2000; Winer (CWP), 2000; and Issue Paper D P8 modeling
b Average removal efficiency expected under MPCA Construction General Permit Sizing Rules 1 and 3
c Upper limit on phosphorus removal with increased sizing and design features, based on national review
d Average rate of soluble phosphorus removal in literature
e See also Calculating stormwater volume and pollutant reductions and credits
f Note that the performance numbers apply only to that portion of total flow actually being treated; it does not include any runoff that by-passes the BMP
g Note that soluble P can transfer from surface water to ground water, but this column refers only to surface water
h Note that 100% is assumed for all infiltration, but only for that portion of the flow fully treated in theinfiltration facility; by-passed runoff or runoff diverted via underdrain does not receive this level of treatment}

Caution: Removal rates shown here are composite averages intended solely for use in comparing performance between BMP designs and for use in calculating load reduction in site-based TP models. They have been adapted, rounded and slightly discounted from statistical values published in BMP performance databases.