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Minnesota Stormwater Manual

Difference between revisions of "Assessing the performance of bioretention"

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[[File:Pdf image.png|100px|thumb|alt=pdf image|<font size=3>[https://stormwater.pca.state.mn.us/index.php?title=File:Assessing_the_performance_of_bioretention_-_Minnesota_Stormwater_Manual_feb_2021.pdf Download pdf]</font size>]]
 
[[File:Pdf image.png|100px|thumb|alt=pdf image|<font size=3>[https://stormwater.pca.state.mn.us/index.php?title=File:Assessing_the_performance_of_bioretention_-_Minnesota_Stormwater_Manual_feb_2021.pdf Download pdf]</font size>]]
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[[File:Bioretention filled.png|thumb|300px|alt=photo of bioretention with water|<font size=3>A properly functioning bioretention practice should drain within 48 hours of a runoff event</font size>]]
  
 
Bioretention practices include biofiltration and bioinfiltration best management practices. <span title="A bioretention practice having an underdrain. All water entering the practice is filtered through engineered media and filtered water is returned to the storm sewer system."> [https://stormwater.pca.state.mn.us/index.php?title=Bioretention '''Biofiltration''']</span> (bioretention with <span title="An underground drain or trench with openings through which the water may percolate from the soil or ground above"> '''underdrains'''</span>) is designed to retain solids and associated pollutants by <span title="Filtration Best Management Practices (BMPs) treat urban stormwater runoff as it flows through a filtering medium, such as sand or an organic material. They are generally used on small drainage areas (5 acres or less) and are primarily designed for pollutant removal. They are effective at removing total suspended solids (TSS), particulate phosphorus, metals, and most organics. They are less effective for soluble pollutants such as dissolved phosphorus, chloride, and nitrate."> [https://stormwater.pca.state.mn.us/index.php?title=Filtration '''filtering''']</span>. A typical method for assessing the performance of of BMPs with underdrains is therefore measuring and comparing pollutant concentrations at the <span title="Influent typically refers to the water entering a stormwater bmp. It refers to water that has not been treated by the device, though the water may have received treatment from an upstream bmp"> '''influent'''</span> and <span title="Effluent typically refers to the water exiting a stormwater BMP. It therefore typically reflects water treated by the device."> '''effluent'''</span>. <span title="A bioretention practice in which no underdrain is used. All water entering the bioinfiltration practice infiltrates or evapotranspires."> '''Bioinfiltration'''</span> (bioretention bmp without underdrains) are more difficult to assess, although considering only potential impacts to surface waters, a properly functioning infiltration system is considered to be highly performing.
 
Bioretention practices include biofiltration and bioinfiltration best management practices. <span title="A bioretention practice having an underdrain. All water entering the practice is filtered through engineered media and filtered water is returned to the storm sewer system."> [https://stormwater.pca.state.mn.us/index.php?title=Bioretention '''Biofiltration''']</span> (bioretention with <span title="An underground drain or trench with openings through which the water may percolate from the soil or ground above"> '''underdrains'''</span>) is designed to retain solids and associated pollutants by <span title="Filtration Best Management Practices (BMPs) treat urban stormwater runoff as it flows through a filtering medium, such as sand or an organic material. They are generally used on small drainage areas (5 acres or less) and are primarily designed for pollutant removal. They are effective at removing total suspended solids (TSS), particulate phosphorus, metals, and most organics. They are less effective for soluble pollutants such as dissolved phosphorus, chloride, and nitrate."> [https://stormwater.pca.state.mn.us/index.php?title=Filtration '''filtering''']</span>. A typical method for assessing the performance of of BMPs with underdrains is therefore measuring and comparing pollutant concentrations at the <span title="Influent typically refers to the water entering a stormwater bmp. It refers to water that has not been treated by the device, though the water may have received treatment from an upstream bmp"> '''influent'''</span> and <span title="Effluent typically refers to the water exiting a stormwater BMP. It therefore typically reflects water treated by the device."> '''effluent'''</span>. <span title="A bioretention practice in which no underdrain is used. All water entering the bioinfiltration practice infiltrates or evapotranspires."> '''Bioinfiltration'''</span> (bioretention bmp without underdrains) are more difficult to assess, although considering only potential impacts to surface waters, a properly functioning infiltration system is considered to be highly performing.

Revision as of 17:55, 13 May 2022

Green Infrastructure: Bioretention practices can be an important tool for retention and detention of stormwater runoff. Because they utilize vegetation, bioretention practices provide additional benefits, including cleaner air, carbon sequestration, improved biological habitat, and aesthetic value.
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photo of bioretention with water
A properly functioning bioretention practice should drain within 48 hours of a runoff event

Bioretention practices include biofiltration and bioinfiltration best management practices. Biofiltration (bioretention with underdrains) is designed to retain solids and associated pollutants by filtering. A typical method for assessing the performance of of BMPs with underdrains is therefore measuring and comparing pollutant concentrations at the influent and effluent. Bioinfiltration (bioretention bmp without underdrains) are more difficult to assess, although considering only potential impacts to surface waters, a properly functioning infiltration system is considered to be highly performing.

An online manual for assessing BMP treatment performance was developed in 2010 by Andrew Erickson, Peter Weiss, and John Gulliver from the University of Minnesota and St. Anthony Falls Hydraulic Laboratory. The manual advises on a four-level process to assess the performance of a Best Management Practice.

  • Level 1: Visual Inspection. This includes assessments for infiltration practices and for filtration practices. The website includes links to a downloadable checklist.
  • Level 2: Capacity Testing. Level 2 testing can be applied to both infiltration and filtration practices.
  • Level 3: Synthetic Runoff Testing for infiltration and filtration practices. Synthetic runoff test results can be used to develop an accurate characterization of pollutant retention or removal, but can be limited by the need for an available water volume and discharge.
  • Level 4: Monitoring for infiltration or filtration practices

Level 1 activities do not produce numerical performance data that could be used to obtain a stormwater management credit (stormwater credit). BMP owners and operators who are interested in using data obtained from Levels 2 and 3 should consult with the MPCA or other regulatory agency to determine if the results are appropriate for credit calculations. Level 4, monitoring, is the method most frequently used for assessment of the performance of a BMP.

Use these links to obtain detailed information on the following topics related to BMP performance monitoring:

Additional information on designing a monitoring network and performing field monitoring are found at this link.

Related pages

Links to pages discussing assessment of other BMPs can be found at this page.

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