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Minnesota Stormwater Manual

Difference between revisions of "Pretreatment"

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[[file:St cloud pretreatment.png|300px|thumb|alt=photo of a pretreatment device for a bioretention practice in St. Cloud, MN|<font size=3>Pre-treatment concept developed by the City of Eagan, modified and implemented by the City of St. Cloud.  Two 5 inch by 40 inch channel drains bolted to the back of the curb.  Construction adhesive used where concrete and drains meet; weep holes drilled in bottom of drains.  Maintenance completed by removing screws with cordless drill, then the grates and scooping out sediment/debris. Hex head screws required.  this is a cost-effective BMP for small surface infiltration practices and can be easily used for retrofits. Photo courtesy of the City of St. Cloud.</font size>]]
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[[file:Check it out.png|100px|thumb|alt=image link to pretreatment selection tool|<font size=3>[https://igeowater.com/mpca/#/intro Pretreatment selection tool]</font size>]]
  
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<font size=4>{{alert|'''Webinar''': June 18, 2019, 9:30-11:00 - [[Stormwater Manual webinars|Minnesota Stormwater Manual updates on Stormwater Pretreatment Practices]]|alert-info}}</font size>
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'''It is strongly recommended that pretreatment devices be certified through [https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-permittee-guidance-resources/Emerging-stormwater-treatment-technologies Washington State's TAPE] or [https://dep.nj.gov/stormwater/stormwater-manufactured-treatment-devices/ NJDEP Manufactured  Treatment Device] certification programs, be modeled using [https://shsam.barr.com/ SHSAM], or follow guidance in this manual for [https://stormwater.pca.state.mn.us/index.php?title=Design,_construction,_operation_and_maintenance_specifications_for_pretreatment_vegetated_filter_strips vegetated filter strips] and [https://stormwater.pca.state.mn.us/index.php?title=Design_criteria_for_stormwater_ponds#Pretreatment forebays].'''
  
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The Manual user will notice that many of the stormwater practices discussed in this Manual recommend [[Glossary#P|pretreatment]] as an integral part of the [[Glossary#B|BMP]] application. In fact, in many applications (ex. infiltration, stormwater ponds), the BMP would not be properly used if pre-treatment is ignored. The simple reason for the use of pretreatment techniques is the necessity to keep a BMP from being overloaded, primarily by sediment. Pretreatment can also be used to dampen the effects of high or rapid inflow, dissipate energy, and provide additional storage. All of these ancillary benefits help BMP performance.
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[[file:St cloud pretreatment.png|300px|thumb|alt=photo of a pretreatment device for a bioretention practice in St. Cloud, MN|<font size=3>Pretreatment concept developed by the City of Eagan, modified and implemented by the City of St. Cloud.  Two 5 inch by 40 inch channel drains bolted to the back of the curb.  Construction adhesive used where concrete and drains meet; weep holes drilled in bottom of drains.  Maintenance completed by removing screws with cordless drill, then the grates and scooping out sediment/debris. Hex head screws required.  this is a cost-effective BMP for small surface infiltration practices and can be easily used for retrofits. Photo courtesy of the City of St. Cloud.</font size>]]
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The Manual user will notice that many of the stormwater practices discussed in this Manual recommend [[Glossary#P|pretreatment]] as an integral part of the [[Glossary#B|BMP]] application. In fact, in many applications (ex. infiltration, stormwater ponds), the BMP would not be properly used if pretreatment is ignored. The simple reason for the use of pretreatment techniques is the necessity to keep a BMP from being overloaded, primarily by sediment. Pretreatment can also be used to dampen the effects of high or rapid inflow, dissipate energy, and provide additional storage. All of these ancillary benefits help BMP performance.
  
 
Pretreatment is a required part of infiltration and filtration practices covered under the Minnesota Construction Stormwater General Permit. This manual describes three general types of pretreatment practices - settling devices, screens, and vegetated filter strips. These are described on the pages below.
 
Pretreatment is a required part of infiltration and filtration practices covered under the Minnesota Construction Stormwater General Permit. This manual describes three general types of pretreatment practices - settling devices, screens, and vegetated filter strips. These are described on the pages below.
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<font size=4>[[Acknowledgements for pretreatment|Acknowledgements]]</font size>
 
<font size=4>[[Acknowledgements for pretreatment|Acknowledgements]]</font size>
  
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<font size=4>[https://stormwater.pca.state.mn.us/index.php?title=Stormwater_Manual_webinars#June_18.2C_2019_-_Minnesota_Stormwater_Manual_updates_on_Stormwater_Pretreatment_Practices '''Webinar on pretreatment''']</font size>
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*[https://igeowater.com/mpca/#/intro Pretreatment selection tool]
 
*[[Overview and methods of pretreatment]]
 
*[[Overview and methods of pretreatment]]
 
*Overviews for different types of pretreatment practices
 
*Overviews for different types of pretreatment practices
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**[[Overview for pretreatment screens]]
 
**[[Overview for pretreatment screens]]
 
**[[Overview for pretreatment vegetated filter strips]]
 
**[[Overview for pretreatment vegetated filter strips]]
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*information for specific types of pretreatment practices
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*Information for specific types of pretreatment practices
 
**[[Design, construction, operation and maintenance specifications for pretreatment vegetated filter strips]]
 
**[[Design, construction, operation and maintenance specifications for pretreatment vegetated filter strips]]
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**[[Pretreatment - Hydrodynamic separation devices]]
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**[[Pretreatment - Screening and straining devices, including forebays]]
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**[[Pretreatment - Above ground and below grade storage and settling devices]]
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**[[Pretreatment - Filtration devices and practices]]
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**[[Pretreatment - Other pretreatment water quality devices and practices]]
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:To see the above pages as a single page, [[Pretreatment practices combined single page|link here]]
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*[[Pretreatment sizing for basins and filters strips]]
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*[[Technical basis for pretreatment sizing for basins and filter strips]]
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*[[Guidance for managing sediment and wastes collected by pretreatment practices]]
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==Tables==
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*[[Pretreatment tables]] - link to tabled information for pretreatment practices
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*[https://stormwater.pca.state.mn.us/index.php?title=Hydrodynamic_separator_tables_combined Hydrodynamic separator tables]
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*[https://stormwater.pca.state.mn.us/index.php?title=Screening_and_straining_devices_tables_combined Screening and straining devices tables]
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*[https://stormwater.pca.state.mn.us/index.php?title=Above_ground_and_below_grade_storage_and_settling_tables_combined Above ground and below grade storage and settling tables]
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*[https://stormwater.pca.state.mn.us/index.php?title=Filtration_tables_combined Filtration tables]
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*[https://stormwater.pca.state.mn.us/index.php?title=Other_water_quality_devices_tables_combined Other water quality devices tables]
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==Other information and links==
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*[[Pretreatment - Additional considerations]]
 
*[[Case studies for pretreatment]]
 
*[[Case studies for pretreatment]]
 
*[[References for pretreatment]]
 
*[[References for pretreatment]]
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*[[Supporting material for pretreatment]]
 
*[[Supporting material for pretreatment]]
 
*[[Photo gallery for pretreatment]]
 
*[[Photo gallery for pretreatment]]
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*[[Pretreatment - Hydrodynamic separation devices]]
 
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*[[Pretreatment - Screening and straining devices, including forebays]]
 
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*[[Pretreatment - Above ground and below grade storage and settling devices]]
 
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*[[Pretreatment - Filtration devices and practices]]
 
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*[[Pretreatment - Other pretreatment water quality devices and practices]]
 
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*[[Pretreatment - Additional considerations]]
 
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The following page was previously included in this pretreatment section of the manual. Much of this information has been updated and the reader is encouraged to use the information in the updated sections, shown in the above Table of Contents. However, there may be some useful information on this page. We hope to eventually update the information on this page. [[Flow-through structures for pre-treatment]]
 
The following page was previously included in this pretreatment section of the manual. Much of this information has been updated and the reader is encouraged to use the information in the updated sections, shown in the above Table of Contents. However, there may be some useful information on this page. We hope to eventually update the information on this page. [[Flow-through structures for pre-treatment]]
  
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[[Category:Level 2 - Best management practices/Pretreatment practices‏‎]]
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For bioretention practices, the type of vegetation in the bioretention cell determines the appropriate flow velocity for which the pre-treatment device should be designed.  For tree-shrub-mulch bioretention cells, velocity through the pre-treatment device should not exceed 1 foot per second, which is the velocity that causes incipient motion of mulch.  For grassed bioretention cells, flow velocity through the pre-treatment device is not to exceed 3 feet per second.  In all cases, appropriate maintenance access should be provided to pre-treatment devices.
 
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==Methods of pretreatment==
 
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[[file:St cloud pretreatment.png|300px|thumb|alt=photo of a pretreatment device for a bioretention practice in St. Cloud, MN|<font size=3>Pre-treatment concept developed by the City of Eagan, modified and implemented by the City of St. Cloud.  Two 5 inch by 40 inch channel drains bolted to the back of the curb.  Construction adhesive used where concrete and drains meet; weep holes drilled in bottom of drains.  Maintenance completed by removing screws with cordless drill, then the grates and scooping out sediment/debris. Hex head screws required.  this is a cost-effective BMP for small surface infiltration practices and can be easily used for retrofits. Photo courtesy of the City of St. Cloud.</font size>]]
 
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Most stormwater managers would identify [[Glossary#F|forebays]] or small sediment basins as the principal pre-treatment method. Although this is probably correct, there are many other ways to pre-treat runoff prior to discharging it into a BMP. Other methods that may under certain circumstances be a better approach than a forebay could include:
 
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*[[Vegetated filter strips]]
 
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*Vegetated swale – soak up water and filter pollutants. Vegetated swales may also be used as a pretreatment device for bioretention cells, particularly in residential areas.  They should bedesigned in accordance with the Minnesota Stormwater Manual.  Grassed swales are open channel conveyances that, when properly vegetated and designed with a shallow slope, provide for sedimentation and trash deposition.  Grassed swale maintenance involves removal of debris, accumulated sediment, and trash. The University of [http://www.sustland.umn.edu/maint/maint.htm Minnesota’s Sustainable Urban Landscape Series website] provides guidance for turf species selection and maintenance,including mowing heights. The [http://www.mncia.org/assets/documents/pub/sod/Production_Requirements_MNST-12-Sod.pdf Minnesota Crop Improvement Association] has developedproduction requirements for salt tolerant turf seed and sod.
 
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*[[Flow-through structures for pre-treatment]]
 
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*Forebays.  Forebays can be used for pre-treatment when concentrated flow enters a bioretention cell.  Forebays generally accept flow from a pipe or curb cut, and provide stilling, sedimentation, and gross pollutant filtration.  They have two specific regions: one for dissipation of velocity and one for sedimentation.  The energy dissipation zone is located immediately adjacent to the pipe or conveyance, and should be 12 to 18 inches deep.  The forebay should then taper to a 6 to 9 inch depth adjacent to the bioretention cell, which provides a zone for sedimentation to occur.  The plan view size of the forebay should be approximately 10 percent of the size of the bioretention cell.  Length to width ratio should be 2:1.
 
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:Forebays are typically lined with a non-woven geotextile and rip-rap that has been sized per MnDOT standards.  An underdrain may be provided beneath the forebay to allow for dewatering between storm events to reduce the potential for mosquito habitat.  Forebays may also be lined in concrete, which allows for easier maintenance when removing sediment and trash.  Weep holes in the concrete should be provided to drain the forebay between storm events.  Maintenance of forebays typically involves removal of accumulated trash and sediment, usually using a small excavator.  Maintenance should be performed when the forebay is half-full with gross solids or more frequently; frequency of maintenance will depend on the amount of sediment and trash generated by the watershed.
 
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:A proprietary product such as Scourstop can often be used as an alternative to rip rap for pretreatment forebays. Scourstop transition mats are semi rigid, high density polyethylene mats that are installed over sod or turf re-inforcement mats and secured with anchors. NOTE: Mention of a specific product does not represent an endorsement of that product by the MPCA.
 
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*Street/parking lot sweeping – remove pollutants from an impervious surface draining to a BMP
 
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*Proprietary settling/swirl chambers – remove particulates and litter prior to a BMP
 
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*Rain gardens – filter pollutants and soak water into the ground
 
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Many of the BMPs discussed in this Manual can be used as pre-treatment for another BMP. The BMP designer is encouraged to go through a planning step in the BMP design that configures it in a [[Using the treatment train approach to BMP selection|treatment train]] with some kind of pre-treatment step.
 
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==References==
 
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*Abu-Zreig, M., R.P. Rudra, H.R. Whiteley, M.N. Lalonde, and N.K. Kaushik. 2003. ''Phosphorus removal in vegetated filter strips''. Journal of Environmental Quality. 32:613-619.
 
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*Abu-Zreig, M., R.P. Rudra, M.N. Lalonde, H.R. Whiteley, and N.K. Kaushik. 2004.'' Experimental investigation of runoff reduction and sediment removal by vegetated filter strips''. Hydrological Processes. 18:2029-2037.
 
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*Barrett, M.E., P.M. Walsh, J.F. Malina, R.J. Charbeneau. 1998. ''Performance of vegetative controls for treating highway runoff''. Journal of Environmental Engineering. 124(11): 1121-1128.
 
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*Blanco-Canqui, H., C.J. Gantzer, S.H. Anderson, and E.E. Alberts. (2004). ''Grass barriers for reduced concentrated flow induced soil and nutrient loss''. Soil Science Society of America Journal 68:1963-1972.
 
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*CALTRANS. 2004. California Department of Transportation, Division of Environmental Analysis. [http://www.dot.ca.gov/hq/oppd/stormwtr/Studies/BMP-Retro-fit-Report.pdf BMP retrofit pilot program]. Final Report CTSW-RT-01-050. January, 2004.
 
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*Goel, P.K., R.P. Rudra, B. Gharabaghi, S. Das, and N. Gupta. 2004. [http://www.pcwp.tamu.edu/docs/lshs/end-notes/pollutants%20removal%20by%20vegetative%20filter%20strips%20planted%20with%20dif-1660940058/pollutants%20removal%20by%20vegetative%20filter%20strips%20planted%20with%20different%20grasses.pdf Pollutants removal by vegetated filter strips planted with different grasses]. ASAE International Meeting, Ottawa Canada, August 1-4, 2004: 2521-2535.
 
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*Howard, A.K., O. Mohseni, J.S. Gulliver, and H.G. Stefan (2012). ''Hydraulic Analysis of Suspended Sediment Removal from Storm Water in a Standard Sump''. Journal of Hydraulic Engineering. ASCE. June 2012. 138(6): 491-502.
 
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*Lantin, A. and Barrett, M. (2005). ''Design and pollutant reduction of vegetated strips and swales''. Conference proceedings. ASCE Environmental and Water Resources Institute (EWRI) Conference. Anchorage, AK.
 
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*McIntire, K. D., Howard, A. K., Mohseni, O., and Gulliver, J.S. (2012). [http://www.cts.umn.edu/Publications/ResearchReports/reportdetail.html?id=2138 Assessment and Recommendations for the Operation of Standard Sumps as Best Management Practices for Stormwater Treatment, Volume 2]. Final Report. Minnesota Department of Transportation. May 2012.
 
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*MPCA (2005). The Minnesota Stormwater Manual. Minnesota Pollution Control Agency. November 2005.
 
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*NJDEP (2004). [http://www.njstormwater.org/bmp_manual2.htm The New Jersey Stormwater Best Management Practices Manual]. New Jersey Department of Environmental Protection, Division of Watershed Management. April 2004.
 
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*Saddoris, D. A., McIntire, K. D., Mohseni, O., and Gulliver, J. S. (2010). Hydrodynamic Separator Sediment Retention Testing. Final Report. [http://www.cts.umn.edu/Publications/ResearchReports/reportdetail.html?id=1890 Minnesota Department of Transportation]. March 2010.
 
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*Van Dijk, P.M., F.J. Kwaad, and M. Klapwijk. (1996). ''Retention of water and sediment by grass strips''. Hydrological Processes 10:1069-1080.
 
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*Wilson, M.A., and O. Mohseni, J. S. Gulliver, R.M. Hozalski, and H.G. Stefan (2009). ''Assessment of Hydrodynamic Separators for Storm-Water Treatment''. Journal of Hydraulic Engineering. ASCE, May 2009. 135(5): 383-392.
 
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*Yu, S., S. Barnes, and V. Gerde. 1993. [http://ntl.bts.gov/lib/36000/36800/36876/93-R16.pdf Testing of Best Management Practices for Controlling Highway Runoff]. FHWA/VA 93-R16. Virginia Transportation Research Council, Charlottesville, VA.
 
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Latest revision as of 21:39, 22 June 2023

image link to pretreatment selection tool
Pretreatment selection tool

It is strongly recommended that pretreatment devices be certified through Washington State's TAPE or NJDEP Manufactured Treatment Device certification programs, be modeled using SHSAM, or follow guidance in this manual for vegetated filter strips and forebays.

photo of a pretreatment device for a bioretention practice in St. Cloud, MN
Pretreatment concept developed by the City of Eagan, modified and implemented by the City of St. Cloud. Two 5 inch by 40 inch channel drains bolted to the back of the curb. Construction adhesive used where concrete and drains meet; weep holes drilled in bottom of drains. Maintenance completed by removing screws with cordless drill, then the grates and scooping out sediment/debris. Hex head screws required. this is a cost-effective BMP for small surface infiltration practices and can be easily used for retrofits. Photo courtesy of the City of St. Cloud.

The Manual user will notice that many of the stormwater practices discussed in this Manual recommend pretreatment as an integral part of the BMP application. In fact, in many applications (ex. infiltration, stormwater ponds), the BMP would not be properly used if pretreatment is ignored. The simple reason for the use of pretreatment techniques is the necessity to keep a BMP from being overloaded, primarily by sediment. Pretreatment can also be used to dampen the effects of high or rapid inflow, dissipate energy, and provide additional storage. All of these ancillary benefits help BMP performance.

Pretreatment is a required part of infiltration and filtration practices covered under the Minnesota Construction Stormwater General Permit. This manual describes three general types of pretreatment practices - settling devices, screens, and vegetated filter strips. These are described on the pages below.

Warning: The Construction Stormwater general permit states: To prevent clogging of the infiltration or filtration system, the Permittee(s) must use a pretreatment device such as a vegetated filter strip, small sedimentation basin, or water quality inlet (e.g., grit chamber) to settle particulates before the stormwater discharges into the infiltration or filtration system.

Acknowledgements

Webinar on pretreatment

To see the above pages as a single page, link here

Tables

Other information and links

The following page was previously included in this pretreatment section of the manual. Much of this information has been updated and the reader is encouraged to use the information in the updated sections, shown in the above Table of Contents. However, there may be some useful information on this page. We hope to eventually update the information on this page. Flow-through structures for pre-treatment

Retrieved from "https://stormwater.pca.state.mn.us/index.php?title=Pretreatment&oldid=68530"

This page was last edited on 22 June 2023, at 21:39.