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{{alert|''Reference to any specific commercial product, process, or service by trade name, trademark, service mark, manufacturer, or otherwise does not constitute or imply endorsement, recommendation, or favoring by the Minnesota Pollution Control Agency. ''|alert-info}}
  
==Project Name==
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[[File:General information page image.png|right|100px|alt=image]]
===Project Overview===
 
Narrative description of pretreatment project
 
:'''Project Location''':
 
:'''Year Constructed''':
 
:'''Type of Pretreatment Practice''': (e.g., forebay, proprietary settling device, etc.)
 
:'''Specific Practice''': (e.g., rock inlet, name of proprietary device)
 
:'''Practice Owner''':
 
:'''Practice Designer''':
 
===Design Considerations===
 
:'''Design Cost''':
 
:'''Design Year''':
 
Narrative description of contributing drainage area, including description of land use
 
  
List of existing impairments and TMDLs that the BMP drains to
+
This page provides several case studies for <span title="Pretreatment reduces maintenance and prolongs the lifespan of structural stormwater BMPs by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''pretreatment''']</span> stormwater practices. Included are case studies for vegetated and rock <span title="an area of permanent vegetation or other material used to reduce sediment, organics, nutrients, pesticides, and other contaminants from runoff and to maintain or improve water quality.> '''filter strips'''</span>, <span title="an artificial pool of water in front of a larger body of water. The larger body of water may be natural or man-made. Forebays have a number of functions. They may be used upstream of reservoirs to trap sediment and debris (sometimes called a sediment forebay) in order to keep the reservoir clean."> '''forebays'''</span>, and <span title="a pre-fabricated stormwater treatment structure utilizing settling, filtration, absorptive/adsorptive materials, vortex separation, vegetative components, and/or other appropriate technology to remove pollutants from storm runoff."> '''proprietary'''</span> settling devices.
:'''Total Contributing Drainage Area''' (acres):
 
:'''Total Impervious Area''' (acres):
 
:'''Watershed Slope''' (%):
 
:'''Downstream Structural Best Management Practice''':
 
:'''Design Pollutant Removal Performance''':
 
Discussion of why that particular pretreatment system was chosen for that project location, specific rationale (e.g., site characteristics, ease of maintenance, etc.)
 
  
Description of sizing criteria used to design pretreatment practice
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==Filter strips==
===Construction Considerations===
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Filter strips are sloped surfaces that rely on shallow distributed flow, typically through dense vegetation, to reduce flow velocity, allow particles to settle, and allow particle interception as their primary mechanism of pollutant removal. Pretreatment filter strips are not to be confused with treatment filter strips, which are designed and used as standalone structural stormwater BMPs. Concentrated or channelized flow is not appropriate for pretreatment vegetated filter strips.
:'''Construction Cost''':
 
:'''Construction Year''':
 
Description of adverse site conditions/other construction challenges encountered during installation
 
===Maintenance Considerations===
 
List or description of types of maintenance practices used for the upkeep of the pretreatment system
 
:'''Maintenance Frequency''':
 
:'''Maintenance Cost''':
 
:'''Disposal Cost''':
 
Description of maintenance challenges, discussion of ease of maintenance
 
  
Discussion of any additional maintenance considerations
+
===City of Burnsville - vegetated filter strip pretreatment===
===Results===
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[[File:Burnsville filter strip figure 1.jpg|300px|thumb|alt=schematic for filter strip|<font size=3>Location of Rain Gardens (Shown in Green) [Barr Engineering Company, 2006].</font size>]]
Discussion of how the performance was measured or estimated
 
:'''Measured or Estimated Pollutant Removal Performance''':
 
For proprietary practices, did were the manufacturer claims met?
 
  
Discussion of lessons learned through the implementation of this pretreatment practice
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*Location: Neighborhood surrounding Crystal Lake in Burnsville, Minnesota
==Villa Park Stormwater Improvements - Preserver==
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*Owners: Homeowners
[[File: Preserver Photo 1.JPG|thumb|300 px|alt=image of Preserver pretreatment device]]
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*Designer: Barr Engineering
[[File: Preserver Schematic 1.JPG|thumb|300 px|alt=image of Preserver pretreatment device]]
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*Contractor: Mike’s Lawn and Landscape
 +
*Year of completion: 2004
 +
*Type of <span title="Pretreatment reduces maintenance and prolongs the lifespan of structural stormwater BMPs by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''pretreatment''']</span> practice: <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."> '''Filtration'''</span> and <span title="Settling devices rely primarily on sedimentation, in which coarse sediments and debris sink or fall out of the collected stormwater. Some settling devices also provide secondary screening to improve the capture of floatables and sediment. Stormwater management processes not provided in settling devices include volume reduction, peak flow reduction (minimal), infiltration (typically very minimal), filtration, sorption and biological treatment.> [https://stormwater.pca.state.mn.us/index.php?title=Overview_for_pretreatment_settling_devices '''settling''']</span>
 +
*Practice Description: <span title="Pretreatment vegetated filter strips are designed to provide sedimentation and screening (by vegetation) to treat stormwater runoff prior to entering a structural stormwater BMP. Pretreatment vegetated filter strips are especially effective at capturing excess sediment in stormwater runoff by settling solids. Pretreatment vegetated filter strips provide limited (due to size) volume reduction, peak flow reduction, infiltration, and biological treatment. Stormwater management processes not provided in pretreatment vegetated filter strips include filtration and sorption."> [https://stormwater.pca.state.mn.us/index.php?title=Overview_for_pretreatment_vegetated_filter_strips '''Vegetated filter strip''']</span>
 +
*Design Features: The vegetated filter strip design filters stormwater runoff which minimizes erosion risks and filters out sediment prior to entering the <span title="Also called bioretention, rain gardens are a landscaping feature that is planted with native perennial plants and is used to manage stormwater runoff from impervious surfaces such as roofs, sidewalks, and parking lots rate control controlling the rate that stormwater is released from localized holding areas into larger conveyance systems> [https://stormwater.pca.state.mn.us/index.php?title=Bioretention '''rain gardens''']</span>.
 +
*Downstream best management practice (BMP) benefitting from pretreatment: [https://stormwater.pca.state.mn.us/index.php?title=Bioretention Rain garden]
 +
*Total drainage area and land use: 5.3 acres (primarily residential)
 +
*Construction cost: &#36;8.00 per square foot (rain garden)
 +
*Pollutant removal: Vegetated filter strips provide 90 percent stormwater runoff volume reductions
 +
*Is the site publicly accessible: No
 +
*Contact: Barr Engineering (kleuthold@barr.com)
  
===Project Overview===
+
====Design summary====
Narrative description of pretreatment project
+
[[File:Burnsville figure 2.png|300px|thumb|alt=figure of filter strip|<font size=3>Vegetated Filter Strip at Curb Cutout (Barr Engineering Company, 2006).</font size>]]
:'''Project Location''': Roseville, MN
 
:'''Year Constructed''':
 
:'''Type of Pretreatment Practice''': Proprietary settling device
 
:'''Specific Practice''': The Preserver
 
:'''Practice Owner''':
 
:'''Practice Designer''':
 
  
===Design Considerations===
+
In 2002, the City of Burnsville worked with Barr Engineering to design rain gardens in a residential neighborhood surrounding Crystal Lake to reduce the pollutant runoff into the lake. Using city funding and a grant from the Metropolitan Council, 17 rain gardens were installed along a street near Lake Crystal as part of a [https://stormwater.pca.state.mn.us/index.php?title=Burnsville_rain_gardens_-_retrofitting_for_water_quality stormwater retrofit study] (Land and Water Magazine, 2004). <span title="Pretreatment vegetated filter strips are designed to provide sedimentation and screening (by vegetation) to treat stormwater runoff prior to entering a structural stormwater BMP. Pretreatment vegetated filter strips are especially effective at capturing excess sediment in stormwater runoff by settling solids. Pretreatment vegetated filter strips provide limited (due to size) volume reduction, peak flow reduction, infiltration, and biological treatment. Stormwater management processes not provided in pretreatment vegetated filter strips include filtration and sorption."> [https://stormwater.pca.state.mn.us/index.php?title=Overview_for_pretreatment_vegetated_filter_strips '''Vegetated filter strips''']</span> provide stormwater <span title="Pretreatment reduces maintenance and prolongs the lifespan of structural stormwater BMPs by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''pretreatment''']</span> between the <span title="Curb  cuts allow  stormwater  to enter  a  stormwater  facility  at  specific  points, thus concentrating runoff both in velocity and volume."> '''curb-cut'''</span> and rain garden. The vegetated filter strip treats stormwater runoff that enters the rain garden by dissipating the flow to minimize erosion and remove sediment from the runoff via filtration and settling into the vegetation. This design reduces the [https://stormwater.pca.state.mn.us/index.php?title=Total_Suspended_Solids_(TSS)_in_stormwater total suspended solids] (TSS) load to the rain garden and allows the rain garden to function as designed and minimize costly maintenance that results from sedimentation.
:'''Design Cost''':
 
:'''Design Year''':
 
The total contributing drainage area to the Preserver was 242 acres, with 8 acres of direct drainage area. An estimated 30% of the direct drainage area to the Preserver was impervious (2.4 acres). The land use of the contributing drainage area was residential, with a mature tree canopy.
 
  
List of existing impairments and TMDLs that the BMP drains to
+
====Maintenance====
:'''Total Contributing Drainage Area''' (acres): 242
+
The homeowners are responsible for performing routine [https://stormwater.pca.state.mn.us/index.php?title=Design,_construction,_operation_and_maintenance_specifications_for_pretreatment_vegetated_filter_strips#Operation_and_maintenance maintenance] such as weeding, raking, and removal of accumulated sediment for the filter strips and rain gardens. The elevation of the filter strip increases over time because of solids settling into the vegetation, so the City of Burnsville has removed the vegetated filter strips, removed the sediment, and replaced the filter strips every five to seven years. Over the 15-year lifespan of the project, filter strips have been replaced twice by the city.
:'''Total Impervious Area''' (acres): ~30%
 
:'''Watershed Slope''' (%):
 
:'''Downstream Structural Best Management Practice''': Irrigation cistern
 
:'''Design Pollutant Removal Performance''':
 
Discussion of why that particular pretreatment system was chosen for that project location, specific rationale (e.g., site characteristics, ease of maintenance, etc.)
 
  
Description of sizing criteria used to design pretreatment practice
+
====Lessons learned====
 +
*Incorporate <span title="stones placed at the entrance to a rain garden to help slow the speed at which runoff enters the gardens> '''“drop waterfalls”'''</span> at curb cutout to slow the speed and reduce erosion potential of the runoff entering the vegetated filter strip
 +
*Vegetated filter strips have performed as designed and prolonged the lifespan and reduced maintenance of the rain gardens
  
===Construction Considerations===
+
====References====
:'''Construction Cost''':
+
*Barr Engineering Company. (2006). [http://www.burnsville.org/DocumentCenter/View/450/Rain-Garden-Project-Summary-2006?bidId= Rain Garden Project Summary]. Retrieved February 5, 2019, from City of Burnsville
:'''Construction Year''':
+
*Land and Water Magazine. (2004, September). [http://www.landandwater.com/features/vol48no5/vol48no5_2.html Burnsville Rainwater Gardens]. Land and Water Magazine, 48(5), p. 47. Retrieved February 5, 2019, from Land and Water Magazine
Description of adverse site conditions/other construction challenges encountered during installation
 
  
===Maintenance Considerations===
+
===City of Fridley - Rock-lined filter strip pretreatment===
 +
*Location: 3rd St. NE, Fridley, Minnesota
 +
*Owners: City of Fridley, Mississippi Watershed Management Organization
 +
*Designer: Wenck Associates/City of Fridley/Minnesota Nice
 +
*Contractor: Minnesota Nice
 +
*Year of completion: 2017
 +
*<span title="Pretreatment reduces maintenance and prolongs the lifespan of structural stormwater BMPs by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''Pretreatment''']</span> practice: <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."> '''Filtration'''</span> and <span title="Settling devices rely primarily on sedimentation, in which coarse sediments and debris sink or fall out of the collected stormwater. Some settling devices also provide secondary screening to improve the capture of floatables and sediment. Stormwater management processes not provided in settling devices include volume reduction, peak flow reduction (minimal), infiltration (typically very minimal), filtration, sorption and biological treatment.> [https://stormwater.pca.state.mn.us/index.php?title=Overview_for_pretreatment_settling_devices '''settling''']</span>
 +
*Practice description: Rock filter strip
 +
*Design features: The design filters stormwater runoff before entering bioswale to minimize erosion risk and filter out and settle sediment.
 +
*Downstream BMP benefitting from pretreatment: <span title="Bioswales are landscape elements designed to concentrate or remove debris and pollution out of surface runoff water. They consist of a swaled drainage course with gently sloped sides (less than 6%) and filled with vegetation, compost and/or riprap."> '''Bioswale'''</span>
 +
*Total drainage area and land use: Approximately 3 acres total (residential)
 +
*Construction Cost: &#36;27,900
 +
*Documented maintenance practices: Annual removal of trash and sediment.  Plants replaced as needed.
 +
*Pollutant removal: Sediment/nutrients, trash
 +
*Is the site publicly accessible: Yes
 +
*Contact: Marcy Bean, Mississippi Watershed Management Organization (mbean@mwmo.org); Jon Lennander, City of Fridley (jon.lennander@fridleymn.gov)
 +
 
 +
====Design summary====
 +
In 2017, the City of Fridley used grant money from the Mississippi Watershed Management Organization (MWMO) to retrofit <span title="is a traffic control measure used to extend the sidewalk, reducing the crossing distance and allowing pedestrians about to cross and approaching vehicle drivers to see each other when vehicles parked in a parking lane would otherwise block visibility."> '''curb bump-outs'''</span> with bioswales to treat stormwater runoff and provide multiple benefits (e.g., traffic control, stormwater treatment, and improved aesthetics) to the neighborhood. Rock-lined filter strips provide pretreatment at the curb cutout before stormwater entered the bioswale. The rock filter strip treats stormwater runoff that enters the bioswale by dissipating the flow to minimize erosion and remove sediment from the runoff via filtration and settling. This design reduces the [https://stormwater.pca.state.mn.us/index.php?title=Total_Suspended_Solids_(TSS)_in_stormwater TSS] load to the bioswale, which allows the bioswale to function as designed and minimize costly maintenance.
 +
 
 +
<gallery caption="Images of rock filter strip. Click on image to enlarge." widths="250px">
 +
File:Fridley figure 1.png|alt=rock filter strip image|Rock Filter Strip at Curb Cut Bioswale Installed Along 3rd Street [City of Fridley, 2018]
 +
File:Fridley figure 2.png|alt=rock filter strip image|Rock Filter Strip Treating Stormwater Runoff [MWMO, 2019]
 +
File:Fridley figure 3.png|alt=rock filter strip image|Rock-Inlet and Bioswale During Heavy Event (City of Fridley)
 +
File:Fridley figure 6.png|alt=rock filter strip image|Sediment Collected at Rock Inlet Pretreatment System on August 27, 2018 (City of Fridley)
 +
</gallery>
 +
 
 +
====Maintenance====
 +
The City of Fridley inspects the rock-lined filter strips and bioswales annually and relocates existing rock, adds rock when needed, and inspects for buried rocks that may be causing damming at the inlet. If damming at the inlet is observed, the rock-lined filter strip can be cleaned, replaced, or an <span title="Inlets collect excess stormwater from the street, transition the flow into storm drains, and can provide maintenance access to the storm drain system."> '''inlet structure'''</span> can be added.
 +
 
 +
====Lessons learned====
 +
*Only bid to contractors with demonstrated similar experience.
 +
*Blocked inlets can cause stormwater to <span title="Stormwater runoff in excess of the design flow, which is diverted around a stormwater structure"> '''bypass'''</span> the basin.
 +
*Initial rocks in filter strips were too small, which resulted in rocks getting carried into the bioswale during larger rain events. Larger rocks were used to avoid this problem moving forward. Through trial-and-error the appropriate rock size was determined to be Class I <span =title"Riprap is a permanent layer of large, angular stone, cobbles, or boulders that is typically used to armor, stabilize, and protect the soil surface against erosion and scour in areas of concentrated flow or wave energy."> [https://stormwater.pca.state.mn.us/index.php?title=Erosion_prevention_practices_-_Riprap '''riprap''']</span> (3 – 6 inches in diameter).
 +
*Regular maintenance has prolonged lifespan and function
 +
*Delegating maintenance responsibilities to contractor results in more consistent maintenance and ultimately better results compared to resident-driven projects. The City of Fridley added three years of maintenance to the contractor’s responsibility to ensure maintenance is conducted and done correctly.
 +
 
 +
====References====
 +
*City of Fridley. (2018, January). [http://www.ci.fridley.mn.us/DocumentCenter/View/4186/Community-Connection-JanuaryFebruary-2018 Fridley Community Connection]. Retrieved February 15, 2019, from City of Fridley
 +
*Mississippi Watershed Management Organization. (no date). [https://www.mwmo.org/projects/fridley-street-reconstruction/ Fridley Street Reconstruction]. Retrieved February 5, 2019 from Mississippi Watershed Management Organization
 +
 
 +
==Forebays==
 +
===City of South St. Paul - Seidl's Lake stormwater retrofit===
 +
[[File:SS Paul figure1.png|300px|thumb|alt=schematic for forebay|<font size=3>Seidl's Lake Forebay Subwatershed Area (Dakota County Soil and Water Conservation District)</font size>]]
 +
 
 +
*Location: 1415 4th Street South, South St. Paul, Minnesota
 +
*Owner: City of South St. Paul
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*Designer: Dakota County Soil and Water Conservation District
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*Contractor: G.L. Contracting
 +
*Year of completion: 2012
 +
*Pretreatment practice: Turfstone <span title="an artificial pool of water in front of a larger body of water. The larger body of water may be natural or man-made. Forebays have a number of functions. They may be used upstream of reservoirs to trap sediment and debris (sometimes called a sediment forebay) in order to keep the reservoir clean."> '''forebay'''</span>
 +
*Design features: The design includes sediment forebay with <span title="Level Spreaders are measures that reduce the erosive energy of concentrated flows by distributing runoff as sheet flow to stabilized vegetative surfaces."> '''level spreaders'''</span>
 +
*Downstream BMP and receiving water benefitting from pretreatment: <span title="Iron-enhanced sand filters are filtration Best Management Practices (BMPs) that incorporate filtration media mixed with iron. The iron removes several dissolved constituents, including phosphate, from stormwater. Iron-enhanced sand filters may be particularly useful for achieving low phosphorus levels needed to improve nutrient impaired waters. "> [https://stormwater.pca.state.mn.us/index.php?title=Iron_enhanced_sand_filter_(Minnesota_Filter) '''iron-enhanced sand filter''']</span> and Seidl’s Lake
 +
*Total drainage area and land use: 15.5 acres (residential)
 +
*Impervious drainage area: 5.68 acres
 +
*Is the site publicly accessible: Yes
 +
*Contact & Email: Joe Barten (joe.barten@co.dakota.mn.us)
 +
 
 +
====Design summary====
 +
[[File:SS Paul figure 2.png|300px|thumb|left|alt=forebay image|<font size=3>Turfstone Pavers at the Bottom of Seidel’s Lake Park Forebay and Biofiltration Cell Following Construction (Dakota County Soil and Water Conservation District)</font size>]]
 +
[[File:SS Paul figure 3.png|300px|thumb|alt=profile view forebay|<font size=3>Profile View of Turfstone Pavers and Forebay Design. Click on image to enlarge.</font size>]]
 +
[[File:SS Paul figure 4.jpg|300px|thumb|left|alt=forebay image|<font size=3>Pretreatment Cell in 2016 Before Cleanout (Dakota County Soil and Water Conservation District)</font size>]]
 +
 
 +
The Seidl’s Lake Park was an area for potential stormwater improvements identified in the [https://mn-southstpaul.civicplus.com/DocumentCenter/View/80/STORMWATER-MANAGEMENT-PLAN?bidId= City of South St. Paul’s Comprehensive Stormwater Management Plan], developed to improve the water quality within the city (City of South St. Paul, 2012). In partnership with the Dakota County Soil and Water Conservation District, an <span title="Iron-enhanced sand filters are filtration Best Management Practices (BMPs) that incorporate filtration media mixed with iron. The iron removes several dissolved constituents, including phosphate, from stormwater. Iron-enhanced sand filters may be particularly useful for achieving low phosphorus levels needed to improve nutrient impaired waters. "> [https://stormwater.pca.state.mn.us/index.php?title=Iron_enhanced_sand_filter_(Minnesota_Filter) '''iron-enhanced sand filter''']</span> and <span title="Pretreatment reduces maintenance and prolongs the lifespan of structural stormwater BMPs by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''pretreatment''']</span> forebay were designed to improve water quality in Seidl’s Lake by treating an untreated 15.5-acre subwatershed.
 +
 
 +
====Maintenance====
 +
In 2016, the pretreatment cell was excavated and found to have accumulated 6 cubic yards of sediment and organic materials.
 +
 
 +
====Lessons learned====
 +
*The turfstone and <span title="a low dam built across a river or body of flowing water to raise the level of water upstream or regulate its flow."> '''weir'''</span> design is successfully capturing large amounts of sediment
 +
*It is uncertain whether surface ponding in the pretreatment area is due to underlying soils or caking of sediment at turfstone and fabric interface
 +
*With future forebay designs, particularly in areas with poor or compacted soils, consider including <span title="An underground drain or trench with openings through which the water may percolate from the soil or ground above"> '''underdrains'''</span> beneath the pretreatment cell which could help facilitate proper drainage and reduce surface ponding
 +
*With future forebay designs, could consider raising the elevation of the pretreatment area relative to the basin and installing screened leveling pipes that connect to the basin to reduce ponding in forebay
 +
*Consider manually vacuuming out turfstone to remove layer of fine sediment at paver surface and replace with washed sand during regular maintenance
 +
 
 +
====References====
 +
*City of South St. Paul. (2012, January). [https://mn-southstpaul.civicplus.com/DocumentCenter/View/80/STORMWATER-MANAGEMENT-PLAN?bidId= Stormwater Management Plan]. Retrieved March 7, 2019, from City of South St. Paul
 +
*Dakota County Soil and Water Conservation District. (2013, January 23). [https://gis.co.dakota.mn.us/content/SWCDdata/FACTSHEETS/12-CCP-002%20Seidls%20Retrofit.pdf Seidls Retrofit]. Retrieved March 07, 2019, from Dakota County Soil and Water Conservation District
 +
 
 +
===City of Savage - Bluff Haven wet pond forebay===
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*Location: Hillsboro Avenue and McColl Drive, Savage, Minnesota
 +
*Owner: City of Savage
 +
*Designer: Westwood Professional Services
 +
*Contractor: John Arthur Homes
 +
*Year of Completion: 2018
 +
*<span title="Pretreatment reduces maintenance and prolongs the lifespan of structural stormwater BMPs by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''Pretreatment''']</span> practice: Sump manhole, <span title="a device used to restrain the flow of a fluid, gas, or loose material or to prevent the spreading of sound or light in a particular direction"> '''baffle'''</span>, and wet forebay
 +
*Practice description: Sump manhole and [https://www.dnr.state.mn.us/water_access/bmp/sump_manhole_with_safl_baffle_bmp.html St. Anthony Falls Laboratory (SAFL) baffle] (or equivalent) with wet pond forebay treat stormwater runoff prior to discharge into an infiltration basin.
 +
*Design features: The design includes a <span title="A catch basin is a structure made of precast concrete with a sump that allows solids, trash and debris to settle out to the bottom of the basin, below an outlet pipe that allows water to flow out of the structure"> '''sump manhole'''</span> with SAFL baffle and a <span title="a stormwater retention basin that includes a combination of permanent pool storage and extended detention storage above the permanent pool to provide additional water quality or rate control"> [https://stormwater.pca.state.mn.us/index.php?title=Stormwater_ponds '''wet pond''']</span> forebay which provides a treatment train approach to stormwater pretreatment. First, the SAFL Baffle retains sands and trash, then the forebay retains most of the silts and smaller organic material, prior to the stormwater entering the infiltration basin where the relatively clean water is infiltrated
 +
*Downstream BMP benefitting from pretreatment: <span title="Infiltration basins, infiltration trenches, dry wells, and underground infiltration systems capture and temporarily store stormwater before allowing it to infiltrate into the soil. As the stormwater penetrates the underlying soil, chemical, biological and physical processes remove pollutants and delay peak stormwater flows. "> [https://stormwater.pca.state.mn.us/index.php?title=Infiltration '''infiltration basin''']</span>
 +
*Total drainage area and land use: 6.8 acres, twin home development
 +
*Total impervious area: 1.84 acre
 +
*Is the site publicly accessible: Yes
 +
*Contact & email: Jesse Carlson, City of Savage (JCarlson@ci.savage.mn.us)
 +
 
 +
====Design summary====
 +
[[File:Savage figure 1.png|300px|thumb|alt=forebay image|<font size=4>Proposed Bluff Haven Stormwater Management Layout. The layout includes a sump manhole with SAFL baffle (red), wet pretreatment forebay (blue), and infiltration basin (yellow) [Scott County, RESPEC, Westwood Professional Services, 2019].</font size>]]
 +
 
 +
Water quality for the proposed 6.8-acre twin home development is provided by <span title="Pretreatment reduces maintenance and prolongs the lifespan of structural stormwater BMPs by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''pretreatment''']</span> and <span title="Infiltration basins, infiltration trenches, dry wells, and underground infiltration systems capture and temporarily store stormwater before allowing it to infiltrate into the soil. As the stormwater penetrates the underlying soil, chemical, biological and physical processes remove pollutants and delay peak stormwater flows. "> [https://stormwater.pca.state.mn.us/index.php?title=Infiltration '''infiltration practices'''] designed to infiltrate the <span title="The volume of water that is treated by a BMP."> [https://stormwater.pca.state.mn.us/index.php?title=Water_quality_criteria '''water quality volume''']</span> of 1.0 inch over the impervious area, utilizing an above ground infiltration basin and an underground infiltration rock trench. The pretreatment for the above ground infiltration basin is a wet basin with <span title="Dead or inactive storage refers to water in a reservoir that cannot be drained by gravity through a dam's outlet"> '''dead storage'''</span> exceeding 25 percent of the water quality volume which is consistent with the Minnesota Stormwater Manual guidelines for pretreatment. Pretreatment of the underground infiltration rock trench is not required because only <span title="an area of grass, trees, or other vegetation set apart for recreational or aesthetic purposes in an otherwise urban environment."> '''green space'''</span> and <span title="roof runoff that has been collected in gutters and piped directly to streets, storm drains, and streams and redirects it away from impervious surfaces to land-scaped areas"> '''disconnected roof runoff'''</span> drains to the BMP [Westwood Professional Services, 2017].
 +
 
 +
Site layout for the above ground infiltration basin and pretreatment is shown below, which treats approximately 4.4 acres of the proposed development.
 +
 
 +
====Construction considerations====
 +
The stormwater BMP <span title="multiple BMPs that work together to remove pollutants utilizing combinations of hydraulic, physical, biological, and chemical methods"> '''treatment train'''</span> included an infiltration basin. Measures shall be taken during construction to protect this area during construction and after. Employ all appropriate <span title="practices designed to prevent or minimize erosion> [https://stormwater.pca.state.mn.us/index.php?title=Erosion_prevention_practices '''erosion''']</span> and <span title="practices are designed to prevent or minimize loss of eroded soil at a site> [https://stormwater.pca.state.mn.us/index.php?title=Sediment_control_practices '''sediment control''']</span> BMPs and time the installation to prevent sediment from impacting the proposed infiltration basin.
 +
 
 +
====Lessons learned====
 +
Steep bluff slopes and existing trees limited stormwater management locations due to City ordinance prohibiting disturbance of such areas during development.  Care was taken to avoid <span title="Storm runoff, flowing in a confined feature such as a channel, ditch, swale, river, etc. Concentrated flow often occurs after a maximum of 300 feet of sheet flow. concentrated flow can lead to severe down- or side-cutting in the resulting channel."> '''concentrated flows'''</span> down the bluff areas [City of Savage, 2017].
 +
 
 +
====References====
 +
*City of Savage. (21 September 2017). [http://lfsrv2.cityofsavage.com/weblinkexternal/0/doc/177572/Page1.aspx Planning Commission Packet] for Thursday September 21, 2017. Accessed March 3, 2019.
 +
*Westwood Professional Services, Inc. (2017 August 11). Preliminary Storm Water Runoff Narrative. Savage, MN. Prepared for John Arthur Homes.
 +
*Westwood Professional Services, Inc. (2018 March 8). Construction Plans for Grading, Sanitary Sewer, Water Main, Storm Sewer, and Streets for Bluff Haven. Savage, MN. Prepared for John Arthur Homes
 +
 
 +
==Proprietary devices==
 +
 
 +
===City of Minnetonka - Libb's Lake Rain Guardian pretreatment===
 +
[[File:Minnetonka figure 2.jpg|300px|thumb|alt=schematic rain guardian|<font size=3>Site Layout With Location of Pretreatment Devices [WSB & Associates, 2017]. The manhole is sump circled in red and the Rain Guardian Turret is circled in blue.. Click on image to enlarge.</font size>]]
 +
 
 +
*Location: 16600 Park Lane, Minnetonka, Minnesota
 +
*Owner: City of Minnetonka
 +
*Designer: WSB & Associates
 +
*Contractor: GMH Asphalt Corporation
 +
*Year of completion: 2016
 +
*<span title="Pretreatment reduces maintenance and prolongs the lifespan of structural stormwater BMPs by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''Pretreatment''']</span> practice: <span title="a pre-fabricated stormwater treatment structure utilizing settling, filtration, absorptive/adsorptive materials, vortex separation, vegetative components, and/or other appropriate technology to remove pollutants from storm runoff."> '''Proprietary'''</span> <span title="Pretreatment screens are small catch basins or conveyance trenches in which screening is the primary mechanism of pollutant removal. These pretreatment devices use a perforated plate or mesh screen to separate and collect sediment, trash, debris and organic material as runoff passes over or through them."> '''screen'''</span>/<span title="Pretreatment settling devices are flow-through structures or devices, proprietary or non-proprietary, above or below ground, where settling is the primary mechanism of pollutant removal. Some of these devices also provide treatment in addition to settling by utilizing a variety of mechanisms to separate and capture pollutant-laden material."> '''settling device'''</span>
 +
*Practice description: <span title="A catch basin is a structure made of precast concrete with a sump that allows solids, trash and debris to settle out to the bottom of the basin, below an outlet pipe that allows water to flow out of the structure"> '''Sump manhole'''</span> and Rain Guardian Turret pretreatment chamber
 +
*Design features: A biofiltration wetland was installed to alleviate the existing flooding concerns near Libb’s Lake and provide water quality treatment for the 2016 street reconstruction project.
 +
*Downstream BMP and receiving water benefitting from pretreatment: Stormwater <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> area, as well as Libb’s Lake and Lake Minnetonka
 +
*Total drainage area and land uses: Sump 2.2 acres, Rain Guardian 0.75 acre (estimated); <span title="residential housing in a rural setting that preserves and minimizes impacts on environmentally sensitive locations and provides scenic quality."> '''large lot residential'''</span>; rolling flat topography
 +
*Impervious drainage area: Sump 1.2 acres (estimated from Google Earth), Rain Guardian 0.15 acre (estimated)
 +
*Design cost: &#36;6,000
 +
*Construction cost: &#36;12,000 (&#36;75,000 with stormwater biofiltration grading and plantings)
 +
*Is the site publicly accessible: Yes
 +
*Contact: Philip Olson, City of Minnetonka (polson@eminnetonka.com)
 +
 
 +
====Design summary====
 +
[[File:Minnetonka figure 1.png|300px|thumb|left|alt=rain guardian image|<font size=3>Location of Stormwater Improvements Upstream of Libb's Lake [City of Minnetonka, 2019]</font size>]]
 +
[[File:Minnetonka figure 3.jpg|300px|thumb|alt=rain guardian image|<font size=3>Rain Guardian Turret at the Inlet of the Shallow Stormwater Wetland Biofiltration Area [Google, 2019]</font size>]]
 +
 
 +
As a part of the [https://eminnetonka.com/capital-improvement-program City of Minnetonka’s 2016–2020 Capital Improvement Program], the 2016 Street Rehabilitation Project updated roadways, watermains, sanitary sewer pipes in the neighborhood around Libb’s Lake, near Grays Bay of Lake Minnetonka. The program also provided improved stormwater drainage and water quality treatment. Before this project, most of the stormwater runoff flowed overland directly to Libb’s Lake without treatment.
 +
 
 +
During the project design, challenges included developing viable stormwater treatment options while accounting for site conditions (e.g., a [https://stormwater.pca.state.mn.us/index.php?title=Shallow_groundwater high groundwater table], rolling terrain, right-of-way limitations, and existing buildings with a history of flooding). To address these challenges, a pretreatment manhole sump was installed in-line along with a Rain Guardian Turret structure to capture stormwater runoff and provide pretreatment before entering a stormwater <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> area that discharges to Libb’s Lake.
 +
 
 +
The sump treats runoff that entered the system upstream, while the Rain Guardian Turret and stormwater biofiltration area treat overland flow from Park Lane. The Rain Guardian Turret chamber treats runoff before it enters the shallow stormwater wetland biofiltration area directly from the roadway and removes sediment, coarse debris, and trash. The pretreatment system captures 0.5 pound of total [https://stormwater.pca.state.mn.us/index.php?title=Phosphorus phosphorus] and 576 pounds of [https://stormwater.pca.state.mn.us/index.php?title=Total_Suspended_Solids_(TSS)_in_stormwater TSS] annually (WSB & Associates, 2015).
 +
 
 +
====Maintenance====
 +
The <span title="A catch basin is a structure made of precast concrete with a sump that allows solids, trash and debris to settle out to the bottom of the basin, below an outlet pipe that allows water to flow out of the structure"> '''sump manhole'''</span> is truck vacuumed to remove deposited sediment and debris. Per the final feasibility study for this project, maintenance occurs twice annually at an estimated cost of &#36;450 per year (WSB & Associates, 2015).
 +
 
 +
To maintain the designed functionality of the Rain Guardian Turret, the City of Minnetonka intends to clear debris from the top grate, remove debris from inside the chamber, and clean the filter wall. In addition to performing regular maintenance, markers are recommended to be placed at the inlet in the winter months to alert snow plows of their locations and prevent snow piles from forming on top of the practice (Anoka Conservation District).
 +
 
 +
====Lessons learned====
 +
Because of the shallow nature of the storm sewer system, the Rain Guardian Turret was selected primarily for its minimal cover requirements to discharge stormwater from the reconstructed Park Lane into the new stormwater wetland. The Rain Guardian Turret has the added benefit of providing additional pretreatment, reducing maintenance needs, and increasing the lifespan of the stormwater wetland.
 +
 
 +
====References====
 +
*Anoka Conservation District. (no date). [http://www.rainguardian.biz/images/Handouts/RAIN_GUARDIAN_MAINTENANCE_GUIDE.pdf Rain Guardian Maintenance Guide]. Retrieved February 22, 2019
 +
*WSB & Associates, Inc. (2015, October 5). Feasibility Report: 2016 Street Rehabilitation Project Libbs Lake Area. Prepared for City of Minnetonka.
 +
*WSB & Associates, Inc. (2017, April). Record Drawings for 2016 Street Rehabilitation Project – Libbs Lake Area. Prepared for City of Minnetonka.
 +
 
 +
===City of New Brighton - Environment21 V2B1 MODEL 4===
 +
[[File:New Brighton figure 1.png|300px|thumb|alt=plan view proprietary device|<font size=3>Plan and section views of Environment21 V2B1 Model 4 (City of New Brighton, 2005). Click on image to enlarge.</font size>]]
 +
 
 +
*Location: Rice Creek Road and Long Lake Road, New Brighton, Minnesota
 +
*Owner: City of New Brighton
 +
*Designer: City of New Brighton
 +
*Contractor: Central Landscaping, Inc.
 +
*Year of completion: 2005
 +
*<span title="Pretreatment reduces maintenance and prolongs the lifespan of structural stormwater BMPs by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''Pretreatment''']</span> practice: <span title="a pre-fabricated stormwater treatment structure utilizing settling, filtration, absorptive/adsorptive materials, vortex separation, vegetative components, and/or other appropriate technology to remove pollutants from storm runoff."> '''Proprietary'''</span> <span title="stormwater management devices that use cyclonic separation to control water pollution. They are designed as flow-through structures with a settling or separation unit to remove sediment and other pollutants."> '''hydrodynamic separator'''</span>
 +
*Practice description: Two Environment21 V2B1 Model 4 installed as part of 2005 street improvement project.
 +
*Downstream receiving water benefitting from pretreatment device: Long Lake
 +
*Total drainage area and land Use: 1.8 and 4.2 acres (residential)
 +
*Impervious drainage area: 1.44 and 1.89 acres, respectively
 +
*Construction cost: $40,526.62
 +
*Is the site publicly accessible: Yes
 +
*Contact: Dustin Lind, City of New Brighton (Dustin.Lind@newbrightonmn.gov)
 +
 
 +
====Design summary====
 +
[[File:New Brighton figure 2.png|300px|thumb|alt=proprietary device image|<font size-3>Location of Environment21 V2B1 Model 4 Structure at Long Lake and Rice Creek Road During Field Testing (Gulliver et al, 2007)</font size>]]
 +
 
 +
As part of the City of New Brighton’s reconstruction of Rice Creek Road in 2005, proposed storm improvements included installing new storm sewer and treatment devices. The storm sewer ultimately discharges to Long Lake. Because the lake is impaired for nutrients, the Rice Creek Watershed District required stormwater treatment. The Environment21 V2B1 Model 4 treatment devices remove floatable debris and sediment from the storm sewer before discharging into Long Lake [Gulliver et al, 2007]. The V2B1 device is a pretreatment device and as such removes trash, sand, and gravels. This case study is an example of pretreatment without a downstream BMP, however pretreatment provided by the V2B1 device benefits the downstream Long Lake.
 +
 +
The system was designed for the 10-year design storm event with a peak intensity of 4.6 inches per hour, with the V2B1 Model 4 installed in-line with the new storm sewer. The Environment21 V2B1 Model 4 consists of two connected <span title="a small covered opening in a floor, pavement, or other surface to allow a person to enter, especially an opening in a city street leading to a sewer."> '''manholes'''</span>, a 5-foot-diameter settling chamber and a 5-foot-diameter floatables trap. Based on the performance assessment, anticipated [https://stormwater.pca.state.mn.us/index.php?title=Total_Suspended_Solids_(TSS)_in_stormwater TSS] removal is 65 percent [Fyten et al, 2008].
 +
 
 +
====Maintenance====
 +
At part of the City’s <span title="A municipal separate storm sewer system (MS4) is a means of transportation, individually or in a system, (e.g. roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, storm drains, etc.) that are: owned or operated by a public entity (e.g. cities, townships, counties, military bases, hospitals, prison complexes, highway departments, universities, etc.) with jurisdiction over disposal of sewage, industrial wastes, stormwater, or other wastes. This includes special districts under State law (sewer, flood control, or drainage districts, etc.), an authorized Indian tribal organization, or a designated and approved management agency under section 208 of the Clean Water Act; designed or used for collecting or transporting stormwater; not a combined sewer; and not part of a publicly owned treatment works."> '''MS4'''</span> program and documented on their MS4 form, twice a year in the spring and fall, the city-owned vacuum truck removes debris and sediment from structures. Debris and sediment are then hauled to a contained spoil pile (where the City stores possibly-contaminated soils) for testing. Barr Engineering conducts tests to determine if the soil is contaminated, then the soil is hauled to the appropriate location.
 +
 
 +
====Lessons learned====
 +
The site was included as part of a field performance study on underground stormwater treatment devices by the University of Minnesota and the Minnesota Department of Transportation. The study found that the hydraulic conditions of the storm sewer system produced a backwater effect inside the treatment manholes during a runoff event, which results in a reduced velocity at the inlet pipe.
 +
Slower velocities may reduce the mixing energy and provide more opportunities for settling. However, coarse particles are unlikely to remain in suspension and may increase sediment deposition in the inlet pipes until a large event flushes the system [Gulliver et al, 2007].
 +
 
 +
Additional Environment21 V2B1 Model 4 case studies are available for the City of Fridley and the City of Wayzata from the manufacturer’s website.
 +
 
 +
====References====
 +
*City of New Brighton. (2005, April 11). State Aid Project 147-020-32. Sheets 8-9 of 29.
 +
*Fyten, A., Lueker, M., & Mohseni, O. (2008). [https://conservancy.umn.edu/bitstream/handle/11299/118084/pr521.pdf?sequence=1&isAllowed=y Performance Assessment of the Environment21 V2B1 Model 4 for Removing Suspended Sediments from Stormwater]. University of Minnesota, St. Anthony Falls Laboratory. Minneapolis: Environment21. Retrieved March 7, 2019
 +
*Gulliver, J., Hozalski, R., Mohseni, O., & Wilson, M. (2007). [https://www.lrrb.org/pdf/200746.pdf Performance Assessment of Underground Stormwater Treatment Devices]. University of Minnesota, Department of Mechanical Engineering. St. Paul: Minnesota Department of Transportation, Research Services Section. Retrieved March 7, 2019
 +
 
 +
===City of St. Paul - Beacon Bluff SAFL Baffle pretreatment===
 +
[[File:St paul figure 1.png|300px|thumb|alt=safl baffle image|<font size=3>Beacon Bluff Storm Sewer Diversion (WSB & Associates, 2015)</font size>]]
 +
[[File:St paul figure 2.png|300px|thumb|alt=conceptual layout safl baffle|<font size=3>Conceptual Layout for the SAFL Baffle (green star) and Infiltration Basin at Beacon Bluff Redevelopment [Loucks Associates, 2013]. Click on image to enlarge.</font size>]]
 +
 
 +
*Location: Phalen Blvd., St. Paul, Minnesota
 +
*Owner: City of St. Paul
 +
*Designer: Loucks Associates
 +
*Contractor: Blackstone Contractors, LLC
 +
*Year of completion: 2011
 +
*<span title="Pretreatment reduces maintenance and prolongs the lifespan of structural stormwater BMPs by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''Pretreatment''']</span> practice: <span title="a pre-fabricated stormwater treatment structure utilizing settling, filtration, absorptive/adsorptive materials, vortex separation, vegetative components, and/or other appropriate technology to remove pollutants from storm runoff."> '''Proprietary'''</span> <span title="Pretreatment screens are small catch basins or conveyance trenches in which screening is the primary mechanism of pollutant removal. These pretreatment devices use a perforated plate or mesh screen to separate and collect sediment, trash, debris and organic material as runoff passes over or through them."> '''screen'''</span>/<span title="Pretreatment settling devices are flow-through structures or devices, proprietary or non-proprietary, above or below ground, where settling is the primary mechanism of pollutant removal. Some of these devices also provide treatment in addition to settling by utilizing a variety of mechanisms to separate and capture pollutant-laden material."> '''settling device'''</span>
 +
*Practice description: [https://www.dnr.state.mn.us/water_access/bmp/sump_manhole_with_safl_baffle_bmp.html St. Anthony Falls Laboratory (SAFL) baffle]
 +
*Design features: The design reduces the turbulence and scouring of high flows through a sump, which minimizes scouring. A garbage trap hood captures trash and other floatables at the outflow.
 +
*Downstream BMP benefitting from pretreatment: <span title="Infiltration basins, infiltration trenches, dry wells, and underground infiltration systems capture and temporarily store stormwater before allowing it to infiltrate into the soil. As the stormwater penetrates the underlying soil, chemical, biological and physical processes remove pollutants and delay peak stormwater flows."> [https://stormwater.pca.state.mn.us/index.php?title=Infiltration '''infiltration system''']</span>
 +
*Total drainage area and land use: 144 Acres, Residential and industrial
 +
*Is the site publicly accessible: Yes
 +
*Contact & email: Monte Hillman (mmh@sspa.com)
 +
 
 +
====Design summary====
 +
[[File:St paul figure 3.png|300px|left|thumb|alt=safl baffle image|<font size=3>Location of Pretreatment Sump Manhole Relative to Infiltration Basin (WSB & Associates, 2011)</font size>]]
 +
[[File:St paul figure 4.jpg|300px|thumb|alt=safl baffle image|<font size=3>Trash and Sediment Captured by Sump and SAFL Baffle at Beacon Bluff (Storm Water Solutions, 2015)</font size>]]
 +
[[File:St paul figure 5.png|300px|thumb|left|alt=safl baffle image|<font size=3>SAFL Baffle in Empty Sump Manhole (Loucks Associates, 2013).</font size>]]
 +
 
 +
On a former <span title="a former industrial or commercial site where future use is affected by real or perceived environmental contamination"> '''brownfield''' </span>, the Saint Paul Port Authority took title of the 46.5-acre brownfield with the intention of redeveloping the site. The site drains a 144-acre area that flows into the Phalen Creek tunnel and, ultimately, to the Mississippi River without any stormwater treatment. Runoff from the watershed typically contained high levels of sediment and contaminants (Saint Paul Port Authority). Flows from the existing 45-inch storm pipe on Duchess Street were diverted onto the site, along with two other storm sewer <span title="An outfall is defined as any point where a separate storm sewer system discharges to either Water of the United States or to another MS4. Outfalls include discharges from pipes, ditches swales, and other points of concentrated flow"> '''outfalls'''</span>, and into the new stormwater treatment system. The diverted flows first went through a [https://www.dnr.state.mn.us/water_access/bmp/sump_manhole_with_safl_baffle_bmp.html SAFL baffle] then into an <span title="Infiltration basins, infiltration trenches, dry wells, and underground infiltration systems capture and temporarily store stormwater before allowing it to infiltrate into the soil. As the stormwater penetrates the underlying soil, chemical, biological and physical processes remove pollutants and delay peak stormwater flows."> [https://stormwater.pca.state.mn.us/index.php?title=Infiltration '''infiltration basin''']</span> that can return the treated water via an overflow back to the Phalen Creek tunnel.
 +
 
 +
The SAFL baffle is in a 6-feet deep with a 6-foot diameter <span title="a pit or hollow in which liquid collects"> '''sump'''</span> designed to trap sand, trash, and floatables. The SAFL baffle is upstream of the infiltration basin and reduces scouring of previously deposited sediments in the sump by reducing turbulence during high flows. A trash hood (model 30R Snout from Best Management Products, Inc) installed on the outflowing pipe prevents trash and other floatables from leaving the sump. This design reduces the floatables and [https://stormwater.pca.state.mn.us/index.php?title=Total_Suspended_Solids_(TSS)_in_stormwater TSS] load to the infiltration basin, allowing the practice to function as designed, maintain storage capacity of the system, and minimize costly maintenance (Storm Water Solutions, 2015).
 +
 
 +
====Maintenance====
 +
The St. Paul Sewer Maintenance Division vacuums out the SAFL Baffle structure 3 times per year. During the first 4 months of use, 130 cubic feet (roughly 13,000 pounds) of sediment were removed. Even with the pretreatment, <span title="The infiltration rate is the velocity or speed at which water enters into the soil"> '''infiltration rates'''</span> in the infiltration basin have been decreasing on an annual basis, likely due to sediment accumulation in the BMP. Maintenance conducted on the infiltration basin last fall noted the basin was still performing as an infiltration practice. Maintenance inspections have also found trash and floatables in the SAFL baffle (WSB & Associates, 2015).
 +
 
 +
====Lessons learned====
 +
*The sump filled up more quickly than expected and clean outs were required three times per year. Planning ahead for additional maintenance in the first years after installation is recommended.
 +
*The sediment collected contained a mix of sand, silt, and organic materials.
 +
*Floatables and garbage were observed in the SAFL baffle during maintenance inspections in 2014.
 +
 
 +
====References====
 +
*Blackstone Contractors, LLC. (2018, March). [http://blackstonecontractorsllc.com/wp-content/uploads/sites/6987/2018/03/summary-beacon-bluff.pdf Beacon Bluff Stormwater Demonstration Area]. Retrieved March 7, 2019 from Blackstone Contractors
 +
*Loucks Associates. (2013). [http://plannersconference.com/pdf/sessions2013/t900_Next%20Generation%20Stormwater%20Management.pdf Next Generation Stormwater Management]. Retrieved March 7, 2019, from American Planning Association Minnesota Chapter
 +
*Saint Paul Port Authority. “Managing Stormwater for the Next Generation.” Saint Paul Historical. Retrieved March 7, 2019 from https://saintpaulhistorical.com/items/show/348
 +
*Storm Water Solutions. (2015, August 27). [https://www.estormwater.com/sites/sws/files/20_CaseBook%2024.pdf St. Paul Stops Storm Water Sediment & Trash]. Retrieved March 11, 2019 from Storm Water Solutions
 +
*WSB & Associates, Inc. (2011). Beacon Bluff SAFL Baffle Installation.
 +
*WSB & Associates, Inc. (2015, April). 2014 [https://www.stpaul.gov/sites/default/files/Media%20Root/Public%20Works/1610-10%20Monitoring%20Report%20ENTIRE%20052215.pdf Stormwater Quality and Quantity Monitoring Program for the City of Saint Paul, Minnesota]. Retrieved March 7, 2019, from City of St. Paul
 +
 
 +
===Capitol Region Watershed District – Upper Villa Park Stormwater Improvements, Preserver pretreatment===
 +
[[File:Cap region figure 1.png|300px|thumb|alt=plan layout of preserver|<font size=3>Plan Layout of Infiltration and Reuse Systems With Location of Pretreatment (Circled in Red) (SRF Consulting Group, Inc, 2015). Click on image to enlarge.</font size>]]
 +
[[File:Cap region figure 2.png|300px|thumb|alt=detail of preserver|<font size=3>Detail of Preserver Installed in Pretreatment Manhole Sump (SRF Consulting Group, Inc, 2015). Click on image to enlarge.</font size>]]
 +
 
 +
*Location: Upper Villa Park, 2100 North Dale Street, Roseville, Minnesota
 +
*Owners: City of Roseville
 +
*Designer: SRF Consulting Group, Inc.
 +
*Contractor: New Look Contracting, Inc.
 +
*Year of completion: 2016
 +
*<span title="Pretreatment reduces maintenance and prolongs the lifespan of structural stormwater BMPs by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''Pretreatment''']</span> practice: <span title="a pre-fabricated stormwater treatment structure utilizing settling, filtration, absorptive/adsorptive materials, vortex separation, vegetative components, and/or other appropriate technology to remove pollutants from storm runoff."> '''Proprietary'''</span> <span title="Pretreatment screens are small catch basins or conveyance trenches in which screening is the primary mechanism of pollutant removal. These pretreatment devices use a perforated plate or mesh screen to separate and collect sediment, trash, debris and organic material as runoff passes over or through them."> '''screen'''</span>/<span title="Pretreatment settling devices are flow-through structures or devices, proprietary or non-proprietary, above or below ground, where settling is the primary mechanism of pollutant removal. Some of these devices also provide treatment in addition to settling by utilizing a variety of mechanisms to separate and capture pollutant-laden material."> '''settling device'''</span>
 +
*Practice description: The Preserver (Momentum Environmental)
 +
*Design features: The design includes a baffled sump manhole treating stormwater inflow to cistern for water reuse as irrigation.
 +
*Downstream BMP benefitting from pretreatment: Irrigation cistern and <span title="Infiltration basins, infiltration trenches, dry wells, and underground infiltration systems capture and temporarily store stormwater before allowing it to infiltrate into the soil. As the stormwater penetrates the underlying soil, chemical, biological and physical processes remove pollutants and delay peak stormwater flows."> [https://stormwater.pca.state.mn.us/index.php?title=Infiltration '''infiltration system''']</span>
 +
*Total drainage area and land use: 242 acres (residential with a mature tree canopy)
 +
*Direct drainage area: 8 acres (30 percent impervious)
 +
*Is the site publicly accessible: Yes
 +
*Contact: Forrest Kelley, CRWD (forrest@capitolregionwd.org)
 +
 
 +
====Summary====
 +
[[File: Preserver Photo 1.JPG|thumb|300 px|left|alt=image of Preserver pretreatment device|<font size=3>Heavy Leaf and Debris Loading in Pretreatment Manhole Sump [Ramsey Conservation District, 2017]. </font size>]]
 
[[File: Preserver Pollutant Removal.JPG|thumb|450 px|alt=image showing pollutant removal for Preserver Pretreatment practice]]
 
[[File: Preserver Pollutant Removal.JPG|thumb|450 px|alt=image showing pollutant removal for Preserver Pretreatment practice]]
List or description of types of maintenance practices used for the upkeep of the pretreatment system
 
:'''Maintenance Frequency''':
 
:'''Maintenance Cost''':
 
:'''Disposal Cost''':
 
The mature tree canopy in the contributing drainage area contributed to heavy organic loads, including large debris. The total captured material would likely be greater with more frequent cleaning of the system - the sump was full approximately halfway through the monitoring period.
 
  
Discussion of any additional maintenance considerations
+
In the fall of 2015, Capitol Region Watershed District (CRWD) partnered with the City of Roseville to construct an underground stormwater <span title="a waterproof receptacle for holding liquids, usually water. Cisterns are often built to catch and store rainwater."> '''cistern'''</span> and <span title="Infiltration basins, infiltration trenches, dry wells, and underground infiltration systems capture and temporarily store stormwater before allowing it to infiltrate into the soil. As the stormwater penetrates the underlying soil, chemical, biological and physical processes remove pollutants and delay peak stormwater flows."> [https://stormwater.pca.state.mn.us/index.php?title=Infiltration '''infiltration system''']</span>. As a part of this project, <span title="Pretreatment reduces maintenance and prolongs the lifespan of structural stormwater BMPs by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''pretreatment''']</span> was used to treat stormwater before it enters the cistern. The pretreatment practice used was The Preserver™ by Momentum Environmental, a 5-foot diameter manhole with 3-foot <span title="a pit or hollow in which liquid collects"> '''sump'''</span> <span title="A catch basin is an engineered drainage structure with the sole function of collecting rainwater and snowmelt from streets and parking lots and transporting it to local waterways through a system of underground piping, culverts, and / or drainage ditches"> '''catch basin'''</span> and <span title="a device used to restrain the flow of a fluid, gas, or loose material or to prevent the spreading of sound or light in a particular direction"> '''baffles'''</span> designed to remove sand, trash, and floatables. The Preserver contains perforated baffles that dissipate inflowing stormwater and minimize scouring of previously deposited sediments in the sump. A <span title="a device to retain or remove floatables (e.g. oil) from water"> '''skimmer'''</span> at the outflow pipe prevents trash and other floatables from leaving the sump. This design reduces the [https://stormwater.pca.state.mn.us/index.php?title=Total_Suspended_Solids_(TSS)_in_stormwater TSS] load to the cistern and infiltration system, which allows these practices to function as designed and to minimize more costly maintenance.
 +
 
 +
====Maintenance====
 +
The City of Roseville routinely removes and disposes of sediment collected annually and estimates that 2,768 pounds of material are captured annually, including 0.526 pounds of total phosphorus.
 +
 
 +
A 2017 monitoring study measured the effectiveness of the Preserver pretreatment device. The results indicated the practice functioned as intended and removed gross solids, [https://stormwater.pca.state.mn.us/index.php?title=Phosphorus phosphorus], and heavy metals. The <span title="an index (means of expression) indicating what sizes (particle size) of particles are present in what proportions (relative particle amount as a percentage where the total amount of particles is 100 %) in the sample particle group to be measured"> '''particle size distribution'''</span> of the removed material showed that most of the material (93.9 percent) was sand (between 75 and 2,000 microns), 2.7 percent of the material was silt (smaller than 75 microns), and 3.4 percent was <span title"large particles, including sediment, debris, and litter"> '''gross solids'''</span> (larger than 2,000 microns), as defined by the MPCA pollutant spectrum and treatment ranges. The removed material had a <span title="the ratio of the density of a substance to the density of a standard, usually water for a liquid or solid, and air for a gas"> '''specific gravity'''</span> of 1.91, indicating a high organic content caused by mature trees in the drainage area and an upstream stormwater wetland. The sump was full approximately halfway through the monitoring period, reducing the overall effectiveness of sediment removal.
 +
 
 +
Monitoring continued in 2018 in an attempt to establish a specific spring storm event (<span title="the initial surface runoff of a rainstorm. During this phase, water pollution entering storm drains in areas with high proportions of impervious surfaces is typically more concentrated compared to the remainder of the storm"> '''first flush'''</span>) as a proxy for sump maintenance activities; however, the results showed that loading was relatively uniform and did not correlate to a specific storm event size. The study’s final recommendation is to clean the sump after spring street sweeping.
 +
 
 +
For more information see [http://www.momentumenv.com/wp-content/uploads/2015/07/Preserver-Inspection-Maintenance-Manual.pdf Preserver Inspection & Maintenance Manual]
 +
 
 +
====Lessons learned====
 +
*The Preserver device functioned as intended to capture and retain material in the sump.
 +
*The watershed loading to the structure appears higher than published values assuming 600 pounds [https://stormwater.pca.state.mn.us/index.php?title=Total_Suspended_Solids_(TSS)_in_stormwater TSS] per acre per year (Observed 2,768 pounds in 6 months over 2.4 acres <span title="impervious areas that are hydraulically connected to the conveyance system (e.g streets with curbs, catch basins, storm drains) and to the watershed outlet point without flowing over pervious areas."> '''directly connected impervious'''</span> area).
 +
*Design structures to accommodate extra sediment storage.
 +
*Runoff loading was not correlated to rainfall. Structure cleaning in spring is recommended after the street sweeping activities.
 +
*Significant heavy metals are present in the captured material.
 +
 
 +
Additional case studies are available from the manufacturer’s website.
 +
 
 +
====References====
 +
*Ramsey Conservation District. (2017). [http://www.momentumenv.com/wp-content/uploads/2018/02/Case-Study-Villa-Park-2017.pdf Preserver Case Study: Villa Park Stormwater Improvements]. Prepared by Momentum Environmental.
 +
*SRF Consulting Group, Inc. (2015). Upper Villa Park Infiltration and Reuse Subsurface Construction Plans. Sheet 6 of 29. Prepared for Capitol Region Watershed District.
 +
 
 +
<noinclude>
 +
==Related pages==
 +
*[https://igeowater.com/mpca/#/intro Pretreatment selection tool]
 +
*[[Overview and methods of pretreatment]]
 +
*Overviews for different types of pretreatment practices
 +
**[[Overview for pretreatment settling devices]]
 +
**[[Overview for pretreatment screens]]
 +
**[[Overview for pretreatment vegetated filter strips]]
 +
*Information for specific types of pretreatment practices
 +
**[[Design, construction, operation and maintenance specifications for pretreatment vegetated filter strips]]
 +
** [[Pretreatment - Hydrodynamic separation devices]]
 +
**[[Pretreatment - Screening and straining devices, including forebays]]
 +
**[[Pretreatment - Above ground and below grade storage and settling devices]]
 +
**[[Pretreatment - Filtration devices and practices]]
 +
**[[Pretreatment - Other pretreatment water quality devices and practices]]
 +
 
 +
:To see the above pages as a single page, [[Pretreatment practices combined single page|link here]]
 +
 
 +
[[Pretreatment sizing for basins and filters strips]]
 +
 
 +
[[Guidance for managing sediment and wastes collected by pretreatment practices]]
 +
 
 +
'''Tables'''
 +
*[[Pretreatment tables]] - link to tabled information for pretreatment practices
 +
*[https://stormwater.pca.state.mn.us/index.php?title=Hydrodynamic_separator_tables_combined Hydrodynamic separator tables]
 +
*[https://stormwater.pca.state.mn.us/index.php?title=Screening_and_straining_devices_tables_combined Screening and straining devices tables]
 +
*[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]
 +
*[https://stormwater.pca.state.mn.us/index.php?title=Filtration_tables_combined Filtration tables]
 +
*[https://stormwater.pca.state.mn.us/index.php?title=Other_water_quality_devices_tables_combined Other water quality devices tables]
  
===Results===
+
'''Other information and links'''
Discussion of how the performance was measured or estimated
+
*[[Pretreatment - Additional considerations]]
:'''Measured or Estimated Pollutant Removal Performance''': 2,768 lbs of material captured by the pretreatment device, including:
+
*[[Case studies for pretreatment]]
:*0.526 lbs phosphorus
+
*[[References for pretreatment]]
:*Significant heavy metals
+
*[[Links for pretreatment]]
For proprietary practices, did were the manufacturer claims met?
+
*[[Definitions for pretreatment]]
 +
*[[Supporting material for pretreatment]]
 +
*[[Photo gallery for pretreatment]]
  
Discussion of lessons learned through the implementation of this pretreatment practice
+
[[Category:Pretreatment]]
 +
[[Category:Level 3 - Best management practices/Case studies and examples/Case studies]]
 +
[[Category:Level 2 - Best management practices/Pretreatment practices‏‎]]
 +
</noinclude>

Latest revision as of 20:32, 18 July 2022

Information: Reference to any specific commercial product, process, or service by trade name, trademark, service mark, manufacturer, or otherwise does not constitute or imply endorsement, recommendation, or favoring by the Minnesota Pollution Control Agency.
image

This page provides several case studies for pretreatment stormwater practices. Included are case studies for vegetated and rock filter strips, forebays, and proprietary settling devices.

Filter strips

Filter strips are sloped surfaces that rely on shallow distributed flow, typically through dense vegetation, to reduce flow velocity, allow particles to settle, and allow particle interception as their primary mechanism of pollutant removal. Pretreatment filter strips are not to be confused with treatment filter strips, which are designed and used as standalone structural stormwater BMPs. Concentrated or channelized flow is not appropriate for pretreatment vegetated filter strips.

City of Burnsville - vegetated filter strip pretreatment

schematic for filter strip
Location of Rain Gardens (Shown in Green) [Barr Engineering Company, 2006].
  • Location: Neighborhood surrounding Crystal Lake in Burnsville, Minnesota
  • Owners: Homeowners
  • Designer: Barr Engineering
  • Contractor: Mike’s Lawn and Landscape
  • Year of completion: 2004
  • Type of pretreatment practice: Filtration and settling
  • Practice Description: Vegetated filter strip
  • Design Features: The vegetated filter strip design filters stormwater runoff which minimizes erosion risks and filters out sediment prior to entering the rain gardens.
  • Downstream best management practice (BMP) benefitting from pretreatment: Rain garden
  • Total drainage area and land use: 5.3 acres (primarily residential)
  • Construction cost: $8.00 per square foot (rain garden)
  • Pollutant removal: Vegetated filter strips provide 90 percent stormwater runoff volume reductions
  • Is the site publicly accessible: No
  • Contact: Barr Engineering (kleuthold@barr.com)

Design summary

figure of filter strip
Vegetated Filter Strip at Curb Cutout (Barr Engineering Company, 2006).

In 2002, the City of Burnsville worked with Barr Engineering to design rain gardens in a residential neighborhood surrounding Crystal Lake to reduce the pollutant runoff into the lake. Using city funding and a grant from the Metropolitan Council, 17 rain gardens were installed along a street near Lake Crystal as part of a stormwater retrofit study (Land and Water Magazine, 2004). Vegetated filter strips provide stormwater pretreatment between the curb-cut and rain garden. The vegetated filter strip treats stormwater runoff that enters the rain garden by dissipating the flow to minimize erosion and remove sediment from the runoff via filtration and settling into the vegetation. This design reduces the total suspended solids (TSS) load to the rain garden and allows the rain garden to function as designed and minimize costly maintenance that results from sedimentation.

Maintenance

The homeowners are responsible for performing routine maintenance such as weeding, raking, and removal of accumulated sediment for the filter strips and rain gardens. The elevation of the filter strip increases over time because of solids settling into the vegetation, so the City of Burnsville has removed the vegetated filter strips, removed the sediment, and replaced the filter strips every five to seven years. Over the 15-year lifespan of the project, filter strips have been replaced twice by the city.

Lessons learned

  • Incorporate “drop waterfalls” at curb cutout to slow the speed and reduce erosion potential of the runoff entering the vegetated filter strip
  • Vegetated filter strips have performed as designed and prolonged the lifespan and reduced maintenance of the rain gardens

References

  • Barr Engineering Company. (2006). Rain Garden Project Summary. Retrieved February 5, 2019, from City of Burnsville
  • Land and Water Magazine. (2004, September). Burnsville Rainwater Gardens. Land and Water Magazine, 48(5), p. 47. Retrieved February 5, 2019, from Land and Water Magazine

City of Fridley - Rock-lined filter strip pretreatment

  • Location: 3rd St. NE, Fridley, Minnesota
  • Owners: City of Fridley, Mississippi Watershed Management Organization
  • Designer: Wenck Associates/City of Fridley/Minnesota Nice
  • Contractor: Minnesota Nice
  • Year of completion: 2017
  • Pretreatment practice: Filtration and settling
  • Practice description: Rock filter strip
  • Design features: The design filters stormwater runoff before entering bioswale to minimize erosion risk and filter out and settle sediment.
  • Downstream BMP benefitting from pretreatment: Bioswale
  • Total drainage area and land use: Approximately 3 acres total (residential)
  • Construction Cost: $27,900
  • Documented maintenance practices: Annual removal of trash and sediment. Plants replaced as needed.
  • Pollutant removal: Sediment/nutrients, trash
  • Is the site publicly accessible: Yes
  • Contact: Marcy Bean, Mississippi Watershed Management Organization (mbean@mwmo.org); Jon Lennander, City of Fridley (jon.lennander@fridleymn.gov)

Design summary

In 2017, the City of Fridley used grant money from the Mississippi Watershed Management Organization (MWMO) to retrofit curb bump-outs with bioswales to treat stormwater runoff and provide multiple benefits (e.g., traffic control, stormwater treatment, and improved aesthetics) to the neighborhood. Rock-lined filter strips provide pretreatment at the curb cutout before stormwater entered the bioswale. The rock filter strip treats stormwater runoff that enters the bioswale by dissipating the flow to minimize erosion and remove sediment from the runoff via filtration and settling. This design reduces the TSS load to the bioswale, which allows the bioswale to function as designed and minimize costly maintenance.

Maintenance

The City of Fridley inspects the rock-lined filter strips and bioswales annually and relocates existing rock, adds rock when needed, and inspects for buried rocks that may be causing damming at the inlet. If damming at the inlet is observed, the rock-lined filter strip can be cleaned, replaced, or an inlet structure can be added.

Lessons learned

  • Only bid to contractors with demonstrated similar experience.
  • Blocked inlets can cause stormwater to bypass the basin.
  • Initial rocks in filter strips were too small, which resulted in rocks getting carried into the bioswale during larger rain events. Larger rocks were used to avoid this problem moving forward. Through trial-and-error the appropriate rock size was determined to be Class I riprap (3 – 6 inches in diameter).
  • Regular maintenance has prolonged lifespan and function
  • Delegating maintenance responsibilities to contractor results in more consistent maintenance and ultimately better results compared to resident-driven projects. The City of Fridley added three years of maintenance to the contractor’s responsibility to ensure maintenance is conducted and done correctly.

References

Forebays

City of South St. Paul - Seidl's Lake stormwater retrofit

schematic for forebay
Seidl's Lake Forebay Subwatershed Area (Dakota County Soil and Water Conservation District)
  • Location: 1415 4th Street South, South St. Paul, Minnesota
  • Owner: City of South St. Paul
  • Designer: Dakota County Soil and Water Conservation District
  • Contractor: G.L. Contracting
  • Year of completion: 2012
  • Pretreatment practice: Turfstone forebay
  • Design features: The design includes sediment forebay with level spreaders
  • Downstream BMP and receiving water benefitting from pretreatment: iron-enhanced sand filter and Seidl’s Lake
  • Total drainage area and land use: 15.5 acres (residential)
  • Impervious drainage area: 5.68 acres
  • Is the site publicly accessible: Yes
  • Contact & Email: Joe Barten (joe.barten@co.dakota.mn.us)

Design summary

forebay image
Turfstone Pavers at the Bottom of Seidel’s Lake Park Forebay and Biofiltration Cell Following Construction (Dakota County Soil and Water Conservation District)
profile view forebay
Profile View of Turfstone Pavers and Forebay Design. Click on image to enlarge.
forebay image
Pretreatment Cell in 2016 Before Cleanout (Dakota County Soil and Water Conservation District)

The Seidl’s Lake Park was an area for potential stormwater improvements identified in the City of South St. Paul’s Comprehensive Stormwater Management Plan, developed to improve the water quality within the city (City of South St. Paul, 2012). In partnership with the Dakota County Soil and Water Conservation District, an iron-enhanced sand filter and pretreatment forebay were designed to improve water quality in Seidl’s Lake by treating an untreated 15.5-acre subwatershed.

Maintenance

In 2016, the pretreatment cell was excavated and found to have accumulated 6 cubic yards of sediment and organic materials.

Lessons learned

  • The turfstone and weir design is successfully capturing large amounts of sediment
  • It is uncertain whether surface ponding in the pretreatment area is due to underlying soils or caking of sediment at turfstone and fabric interface
  • With future forebay designs, particularly in areas with poor or compacted soils, consider including underdrains beneath the pretreatment cell which could help facilitate proper drainage and reduce surface ponding
  • With future forebay designs, could consider raising the elevation of the pretreatment area relative to the basin and installing screened leveling pipes that connect to the basin to reduce ponding in forebay
  • Consider manually vacuuming out turfstone to remove layer of fine sediment at paver surface and replace with washed sand during regular maintenance

References

  • City of South St. Paul. (2012, January). Stormwater Management Plan. Retrieved March 7, 2019, from City of South St. Paul
  • Dakota County Soil and Water Conservation District. (2013, January 23). Seidls Retrofit. Retrieved March 07, 2019, from Dakota County Soil and Water Conservation District

City of Savage - Bluff Haven wet pond forebay

  • Location: Hillsboro Avenue and McColl Drive, Savage, Minnesota
  • Owner: City of Savage
  • Designer: Westwood Professional Services
  • Contractor: John Arthur Homes
  • Year of Completion: 2018
  • Pretreatment practice: Sump manhole, baffle, and wet forebay
  • Practice description: Sump manhole and St. Anthony Falls Laboratory (SAFL) baffle (or equivalent) with wet pond forebay treat stormwater runoff prior to discharge into an infiltration basin.
  • Design features: The design includes a sump manhole with SAFL baffle and a wet pond forebay which provides a treatment train approach to stormwater pretreatment. First, the SAFL Baffle retains sands and trash, then the forebay retains most of the silts and smaller organic material, prior to the stormwater entering the infiltration basin where the relatively clean water is infiltrated
  • Downstream BMP benefitting from pretreatment: infiltration basin
  • Total drainage area and land use: 6.8 acres, twin home development
  • Total impervious area: 1.84 acre
  • Is the site publicly accessible: Yes
  • Contact & email: Jesse Carlson, City of Savage (JCarlson@ci.savage.mn.us)

Design summary

forebay image
Proposed Bluff Haven Stormwater Management Layout. The layout includes a sump manhole with SAFL baffle (red), wet pretreatment forebay (blue), and infiltration basin (yellow) [Scott County, RESPEC, Westwood Professional Services, 2019].

Water quality for the proposed 6.8-acre twin home development is provided by pretreatment and infiltration practices designed to infiltrate the water quality volume of 1.0 inch over the impervious area, utilizing an above ground infiltration basin and an underground infiltration rock trench. The pretreatment for the above ground infiltration basin is a wet basin with dead storage exceeding 25 percent of the water quality volume which is consistent with the Minnesota Stormwater Manual guidelines for pretreatment. Pretreatment of the underground infiltration rock trench is not required because only green space and disconnected roof runoff drains to the BMP [Westwood Professional Services, 2017].

Site layout for the above ground infiltration basin and pretreatment is shown below, which treats approximately 4.4 acres of the proposed development.

Construction considerations

The stormwater BMP treatment train included an infiltration basin. Measures shall be taken during construction to protect this area during construction and after. Employ all appropriate erosion and sediment control BMPs and time the installation to prevent sediment from impacting the proposed infiltration basin.

Lessons learned

Steep bluff slopes and existing trees limited stormwater management locations due to City ordinance prohibiting disturbance of such areas during development. Care was taken to avoid concentrated flows down the bluff areas [City of Savage, 2017].

References

  • City of Savage. (21 September 2017). Planning Commission Packet for Thursday September 21, 2017. Accessed March 3, 2019.
  • Westwood Professional Services, Inc. (2017 August 11). Preliminary Storm Water Runoff Narrative. Savage, MN. Prepared for John Arthur Homes.
  • Westwood Professional Services, Inc. (2018 March 8). Construction Plans for Grading, Sanitary Sewer, Water Main, Storm Sewer, and Streets for Bluff Haven. Savage, MN. Prepared for John Arthur Homes

Proprietary devices

City of Minnetonka - Libb's Lake Rain Guardian pretreatment

schematic rain guardian
Site Layout With Location of Pretreatment Devices [WSB & Associates, 2017]. The manhole is sump circled in red and the Rain Guardian Turret is circled in blue.. Click on image to enlarge.
  • Location: 16600 Park Lane, Minnetonka, Minnesota
  • Owner: City of Minnetonka
  • Designer: WSB & Associates
  • Contractor: GMH Asphalt Corporation
  • Year of completion: 2016
  • Pretreatment practice: Proprietary screen/ settling device
  • Practice description: Sump manhole and Rain Guardian Turret pretreatment chamber
  • Design features: A biofiltration wetland was installed to alleviate the existing flooding concerns near Libb’s Lake and provide water quality treatment for the 2016 street reconstruction project.
  • Downstream BMP and receiving water benefitting from pretreatment: Stormwater biofiltration area, as well as Libb’s Lake and Lake Minnetonka
  • Total drainage area and land uses: Sump 2.2 acres, Rain Guardian 0.75 acre (estimated); large lot residential; rolling flat topography
  • Impervious drainage area: Sump 1.2 acres (estimated from Google Earth), Rain Guardian 0.15 acre (estimated)
  • Design cost: $6,000
  • Construction cost: $12,000 ($75,000 with stormwater biofiltration grading and plantings)
  • Is the site publicly accessible: Yes
  • Contact: Philip Olson, City of Minnetonka (polson@eminnetonka.com)

Design summary

rain guardian image
Location of Stormwater Improvements Upstream of Libb's Lake [City of Minnetonka, 2019]
rain guardian image
Rain Guardian Turret at the Inlet of the Shallow Stormwater Wetland Biofiltration Area [Google, 2019]

As a part of the City of Minnetonka’s 2016–2020 Capital Improvement Program, the 2016 Street Rehabilitation Project updated roadways, watermains, sanitary sewer pipes in the neighborhood around Libb’s Lake, near Grays Bay of Lake Minnetonka. The program also provided improved stormwater drainage and water quality treatment. Before this project, most of the stormwater runoff flowed overland directly to Libb’s Lake without treatment.

During the project design, challenges included developing viable stormwater treatment options while accounting for site conditions (e.g., a high groundwater table, rolling terrain, right-of-way limitations, and existing buildings with a history of flooding). To address these challenges, a pretreatment manhole sump was installed in-line along with a Rain Guardian Turret structure to capture stormwater runoff and provide pretreatment before entering a stormwater biofiltration area that discharges to Libb’s Lake.

The sump treats runoff that entered the system upstream, while the Rain Guardian Turret and stormwater biofiltration area treat overland flow from Park Lane. The Rain Guardian Turret chamber treats runoff before it enters the shallow stormwater wetland biofiltration area directly from the roadway and removes sediment, coarse debris, and trash. The pretreatment system captures 0.5 pound of total phosphorus and 576 pounds of TSS annually (WSB & Associates, 2015).

Maintenance

The sump manhole is truck vacuumed to remove deposited sediment and debris. Per the final feasibility study for this project, maintenance occurs twice annually at an estimated cost of $450 per year (WSB & Associates, 2015).

To maintain the designed functionality of the Rain Guardian Turret, the City of Minnetonka intends to clear debris from the top grate, remove debris from inside the chamber, and clean the filter wall. In addition to performing regular maintenance, markers are recommended to be placed at the inlet in the winter months to alert snow plows of their locations and prevent snow piles from forming on top of the practice (Anoka Conservation District).

Lessons learned

Because of the shallow nature of the storm sewer system, the Rain Guardian Turret was selected primarily for its minimal cover requirements to discharge stormwater from the reconstructed Park Lane into the new stormwater wetland. The Rain Guardian Turret has the added benefit of providing additional pretreatment, reducing maintenance needs, and increasing the lifespan of the stormwater wetland.

References

  • Anoka Conservation District. (no date). Rain Guardian Maintenance Guide. Retrieved February 22, 2019
  • WSB & Associates, Inc. (2015, October 5). Feasibility Report: 2016 Street Rehabilitation Project Libbs Lake Area. Prepared for City of Minnetonka.
  • WSB & Associates, Inc. (2017, April). Record Drawings for 2016 Street Rehabilitation Project – Libbs Lake Area. Prepared for City of Minnetonka.

City of New Brighton - Environment21 V2B1 MODEL 4

plan view proprietary device
Plan and section views of Environment21 V2B1 Model 4 (City of New Brighton, 2005). Click on image to enlarge.
  • Location: Rice Creek Road and Long Lake Road, New Brighton, Minnesota
  • Owner: City of New Brighton
  • Designer: City of New Brighton
  • Contractor: Central Landscaping, Inc.
  • Year of completion: 2005
  • Pretreatment practice: Proprietary hydrodynamic separator
  • Practice description: Two Environment21 V2B1 Model 4 installed as part of 2005 street improvement project.
  • Downstream receiving water benefitting from pretreatment device: Long Lake
  • Total drainage area and land Use: 1.8 and 4.2 acres (residential)
  • Impervious drainage area: 1.44 and 1.89 acres, respectively
  • Construction cost: $40,526.62
  • Is the site publicly accessible: Yes
  • Contact: Dustin Lind, City of New Brighton (Dustin.Lind@newbrightonmn.gov)

Design summary

proprietary device image
Location of Environment21 V2B1 Model 4 Structure at Long Lake and Rice Creek Road During Field Testing (Gulliver et al, 2007)

As part of the City of New Brighton’s reconstruction of Rice Creek Road in 2005, proposed storm improvements included installing new storm sewer and treatment devices. The storm sewer ultimately discharges to Long Lake. Because the lake is impaired for nutrients, the Rice Creek Watershed District required stormwater treatment. The Environment21 V2B1 Model 4 treatment devices remove floatable debris and sediment from the storm sewer before discharging into Long Lake [Gulliver et al, 2007]. The V2B1 device is a pretreatment device and as such removes trash, sand, and gravels. This case study is an example of pretreatment without a downstream BMP, however pretreatment provided by the V2B1 device benefits the downstream Long Lake.

The system was designed for the 10-year design storm event with a peak intensity of 4.6 inches per hour, with the V2B1 Model 4 installed in-line with the new storm sewer. The Environment21 V2B1 Model 4 consists of two connected manholes, a 5-foot-diameter settling chamber and a 5-foot-diameter floatables trap. Based on the performance assessment, anticipated TSS removal is 65 percent [Fyten et al, 2008].

Maintenance

At part of the City’s MS4 program and documented on their MS4 form, twice a year in the spring and fall, the city-owned vacuum truck removes debris and sediment from structures. Debris and sediment are then hauled to a contained spoil pile (where the City stores possibly-contaminated soils) for testing. Barr Engineering conducts tests to determine if the soil is contaminated, then the soil is hauled to the appropriate location.

Lessons learned

The site was included as part of a field performance study on underground stormwater treatment devices by the University of Minnesota and the Minnesota Department of Transportation. The study found that the hydraulic conditions of the storm sewer system produced a backwater effect inside the treatment manholes during a runoff event, which results in a reduced velocity at the inlet pipe. Slower velocities may reduce the mixing energy and provide more opportunities for settling. However, coarse particles are unlikely to remain in suspension and may increase sediment deposition in the inlet pipes until a large event flushes the system [Gulliver et al, 2007].

Additional Environment21 V2B1 Model 4 case studies are available for the City of Fridley and the City of Wayzata from the manufacturer’s website.

References

City of St. Paul - Beacon Bluff SAFL Baffle pretreatment

safl baffle image
Beacon Bluff Storm Sewer Diversion (WSB & Associates, 2015)
conceptual layout safl baffle
Conceptual Layout for the SAFL Baffle (green star) and Infiltration Basin at Beacon Bluff Redevelopment [Loucks Associates, 2013]. Click on image to enlarge.
  • Location: Phalen Blvd., St. Paul, Minnesota
  • Owner: City of St. Paul
  • Designer: Loucks Associates
  • Contractor: Blackstone Contractors, LLC
  • Year of completion: 2011
  • Pretreatment practice: Proprietary screen/ settling device
  • Practice description: St. Anthony Falls Laboratory (SAFL) baffle
  • Design features: The design reduces the turbulence and scouring of high flows through a sump, which minimizes scouring. A garbage trap hood captures trash and other floatables at the outflow.
  • Downstream BMP benefitting from pretreatment: infiltration system
  • Total drainage area and land use: 144 Acres, Residential and industrial
  • Is the site publicly accessible: Yes
  • Contact & email: Monte Hillman (mmh@sspa.com)

Design summary

safl baffle image
Location of Pretreatment Sump Manhole Relative to Infiltration Basin (WSB & Associates, 2011)
safl baffle image
Trash and Sediment Captured by Sump and SAFL Baffle at Beacon Bluff (Storm Water Solutions, 2015)
safl baffle image
SAFL Baffle in Empty Sump Manhole (Loucks Associates, 2013).

On a former brownfield , the Saint Paul Port Authority took title of the 46.5-acre brownfield with the intention of redeveloping the site. The site drains a 144-acre area that flows into the Phalen Creek tunnel and, ultimately, to the Mississippi River without any stormwater treatment. Runoff from the watershed typically contained high levels of sediment and contaminants (Saint Paul Port Authority). Flows from the existing 45-inch storm pipe on Duchess Street were diverted onto the site, along with two other storm sewer outfalls, and into the new stormwater treatment system. The diverted flows first went through a SAFL baffle then into an infiltration basin that can return the treated water via an overflow back to the Phalen Creek tunnel.

The SAFL baffle is in a 6-feet deep with a 6-foot diameter sump designed to trap sand, trash, and floatables. The SAFL baffle is upstream of the infiltration basin and reduces scouring of previously deposited sediments in the sump by reducing turbulence during high flows. A trash hood (model 30R Snout from Best Management Products, Inc) installed on the outflowing pipe prevents trash and other floatables from leaving the sump. This design reduces the floatables and TSS load to the infiltration basin, allowing the practice to function as designed, maintain storage capacity of the system, and minimize costly maintenance (Storm Water Solutions, 2015).

Maintenance

The St. Paul Sewer Maintenance Division vacuums out the SAFL Baffle structure 3 times per year. During the first 4 months of use, 130 cubic feet (roughly 13,000 pounds) of sediment were removed. Even with the pretreatment, infiltration rates in the infiltration basin have been decreasing on an annual basis, likely due to sediment accumulation in the BMP. Maintenance conducted on the infiltration basin last fall noted the basin was still performing as an infiltration practice. Maintenance inspections have also found trash and floatables in the SAFL baffle (WSB & Associates, 2015).

Lessons learned

  • The sump filled up more quickly than expected and clean outs were required three times per year. Planning ahead for additional maintenance in the first years after installation is recommended.
  • The sediment collected contained a mix of sand, silt, and organic materials.
  • Floatables and garbage were observed in the SAFL baffle during maintenance inspections in 2014.

References

Capitol Region Watershed District – Upper Villa Park Stormwater Improvements, Preserver pretreatment

plan layout of preserver
Plan Layout of Infiltration and Reuse Systems With Location of Pretreatment (Circled in Red) (SRF Consulting Group, Inc, 2015). Click on image to enlarge.
detail of preserver
Detail of Preserver Installed in Pretreatment Manhole Sump (SRF Consulting Group, Inc, 2015). Click on image to enlarge.
  • Location: Upper Villa Park, 2100 North Dale Street, Roseville, Minnesota
  • Owners: City of Roseville
  • Designer: SRF Consulting Group, Inc.
  • Contractor: New Look Contracting, Inc.
  • Year of completion: 2016
  • Pretreatment practice: Proprietary screen/ settling device
  • Practice description: The Preserver (Momentum Environmental)
  • Design features: The design includes a baffled sump manhole treating stormwater inflow to cistern for water reuse as irrigation.
  • Downstream BMP benefitting from pretreatment: Irrigation cistern and infiltration system
  • Total drainage area and land use: 242 acres (residential with a mature tree canopy)
  • Direct drainage area: 8 acres (30 percent impervious)
  • Is the site publicly accessible: Yes
  • Contact: Forrest Kelley, CRWD (forrest@capitolregionwd.org)

Summary

image of Preserver pretreatment device
Heavy Leaf and Debris Loading in Pretreatment Manhole Sump [Ramsey Conservation District, 2017].
image showing pollutant removal for Preserver Pretreatment practice

In the fall of 2015, Capitol Region Watershed District (CRWD) partnered with the City of Roseville to construct an underground stormwater cistern and infiltration system. As a part of this project, pretreatment was used to treat stormwater before it enters the cistern. The pretreatment practice used was The Preserver™ by Momentum Environmental, a 5-foot diameter manhole with 3-foot sump catch basin and baffles designed to remove sand, trash, and floatables. The Preserver contains perforated baffles that dissipate inflowing stormwater and minimize scouring of previously deposited sediments in the sump. A skimmer at the outflow pipe prevents trash and other floatables from leaving the sump. This design reduces the TSS load to the cistern and infiltration system, which allows these practices to function as designed and to minimize more costly maintenance.

Maintenance

The City of Roseville routinely removes and disposes of sediment collected annually and estimates that 2,768 pounds of material are captured annually, including 0.526 pounds of total phosphorus.

A 2017 monitoring study measured the effectiveness of the Preserver pretreatment device. The results indicated the practice functioned as intended and removed gross solids, phosphorus, and heavy metals. The particle size distribution of the removed material showed that most of the material (93.9 percent) was sand (between 75 and 2,000 microns), 2.7 percent of the material was silt (smaller than 75 microns), and 3.4 percent was gross solids (larger than 2,000 microns), as defined by the MPCA pollutant spectrum and treatment ranges. The removed material had a specific gravity of 1.91, indicating a high organic content caused by mature trees in the drainage area and an upstream stormwater wetland. The sump was full approximately halfway through the monitoring period, reducing the overall effectiveness of sediment removal.

Monitoring continued in 2018 in an attempt to establish a specific spring storm event ( first flush) as a proxy for sump maintenance activities; however, the results showed that loading was relatively uniform and did not correlate to a specific storm event size. The study’s final recommendation is to clean the sump after spring street sweeping.

For more information see Preserver Inspection & Maintenance Manual

Lessons learned

  • The Preserver device functioned as intended to capture and retain material in the sump.
  • The watershed loading to the structure appears higher than published values assuming 600 pounds TSS per acre per year (Observed 2,768 pounds in 6 months over 2.4 acres directly connected impervious area).
  • Design structures to accommodate extra sediment storage.
  • Runoff loading was not correlated to rainfall. Structure cleaning in spring is recommended after the street sweeping activities.
  • Significant heavy metals are present in the captured material.

Additional case studies are available from the manufacturer’s website.

References

  • Ramsey Conservation District. (2017). Preserver Case Study: Villa Park Stormwater Improvements. Prepared by Momentum Environmental.
  • SRF Consulting Group, Inc. (2015). Upper Villa Park Infiltration and Reuse Subsurface Construction Plans. Sheet 6 of 29. Prepared for Capitol Region Watershed District.


Related pages

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

Pretreatment sizing for basins and filters strips

Guidance for managing sediment and wastes collected by pretreatment practices

Tables

Other information and links

This page was last edited on 18 July 2022, at 20:32.