This table shows comparison of phosphorus removal for different BMPs.a,e,f Values represent the percent of incoming pollutant that is removed. Source: MPCA Minnesota Stormwater Manual.
Link to this table
Information: 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.
BMP group BMP design variation Average TP removal rateb Maximum TP removal ratec Average soluble P removal rated,g
Bioretention Underdrain 65 75 60
Infiltration 100 100 100
Filtration Sand filter 50 55 0
Dry swale 0 55 0
Wet swale 65 75 70
Infiltrationf Infiltration trench 100 100 100
Infiltration basin 100 100 100
Stormwater ponds Wet pond 50 65 70
Multiple pond 60 75 75
Stormwater wetlands Shallow wetland 40 55 50
Pond/wetland 55 75 65

a Removal rates show in table are a composite of five sources: [(http://www.bmpdatabase.org ASCE/EPA International Database];

Caraco (Center for Watershed protection, 2001)];

Maryland Department of the Environment(2000)];

Winer (Center for Watershed Protection, 2000)];

P8 modeling (William Walker)]

b Average removal efficiency expected under MPCA 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 the literature
e See section on calculating credits for each BMP in this Manual.
f Note that the performance numbers apply only to that portion of total flow actually being treated; it does not include any runoff that bypasses the BMP
gNote that soluble P can transfer from surface water to groundwater, but this column refers only to surface water
hNote that 100% is assumed for all infiltration, but only for that portion of the flow fully treated in the infiltration facility; by-passed runoff or runoff diverted via underdrain does not receive this level of treatment.