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The table at right compares data on the water quality treatment and runoff volume reduction performance of stormwater treatment systems analyzed at the University of New Hampshire Stormwater Center (UNHSC) to date. Systems are classied by category: low impact development (LID) systems, manufactured devices, and conventional structural approaches. Data is derived from UNHSC and a variety of sources, including the U.S. Environmental Protection Agency, manufacturers, and academic field studies.

Water quality treatment performance is assessed by pollutant; percent reduction is recorded in median values. Volume reduction is represented by percent average peak flow reduction and average lag time in minutes. (For more on these performance standards, see table.) “NT” signifes “no treatment,” indicating that the stormwater treatment did not remove the pollutant in question. “NA” indicates the system was “not analyzed” for a contaminant’s removal or runoff volume reduction in a particular study. Light brown bars represent UNHSC data; white bars represent data from other sources.