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Inspection and Maintenance: Enhanced Swales (view source)
Revision as of 19:12, 28 September 2022
, 2 years agoCreated page with "File:Cover Photo swales.PNG|thumb|750px|link=https://sustainabletechnologies.ca/app/uploads/2018/02/Enhanced-Swales-Fact-Sheet.pdf|Inspection & Maintenance Guidance of [[enh..."
[[File:Cover Photo swales.PNG|thumb|750px|link=https://sustainabletechnologies.ca/app/uploads/2018/02/Enhanced-Swales-Fact-Sheet.pdf|Inspection & Maintenance Guidance of [[enhanced swales]], which are a vegetated stormwater best management practices that contains gently sloping open channels featuring a [[Enhanced swales: Specifications|parabolic or trapezoidal cross-section]] and [[check dams]], designed to both convey and treat stormwater runoff temporarily before entering the storm system (TRCA, 2016<ref> TRCA. 2016. Fact Sheet - Inspection and Maintenance of Stormwater Best Management Practices: Enhanced Swales. https://sustainabletechnologies.ca/app/uploads/2018/02/Enhanced-Swales-Fact-Sheet.pdf</ref>)]]
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==Overview==
[[Enhanced swales]] are gently sloping vegetated open channels featuring a parabolic or trapezoidal cross-section and check dams, designed to convey and treat stormwater runoff (i.e., rainwater or snowmelt from roofs or pavements). The [[grading]], [[Check dams]] and [[vegetation]] spreads out and slows down the flow of water, allowing suspended sediment and floatables (e.g., trash, natural debris, oil and grease) to settle out. A portion of the flowing water soaks into the soil and replenishes groundwater or is taken up by plant roots and evaporated back to the atmosphere. Runoff water is delivered to the practice through [[inlets]] such as [[curb cuts]], [[Curb cuts: Gallery|spillways]] or other concrete structures, sheet flow from pavement edges, or [[pipes]] connected to [[Pretreatment|catchbasins]] or [[Downspout disconnection|roof downspouts]]. The [[Plant lists|planting bed]] and side [[slopes]] are typically covered with [[grasses]] or a mixture of flood tolerant, [[erosion]] resistant [[vegetation]] and [[stone]]. They do not feature [[filter media]] soil and [[underdrains|sub-drains]] like [[bioretention]] or [[bioswales]] do. Water not ponded behind check dams or absorbed by the planting bed is conveyed to an adjacent drainage system (e.g., municipal storm sewer or other BMP) at the lowest downstream point by an [[Overflow|outlet structure]] (e.g., ditch inlet catchbasin, culvert). Key components of this feature are described in further detail below. <br>
</br>
Properly functioning enhanced swales reduce the quantity of pollutants and runoff being discharged to municipal storm sewers and receiving waters (i.e., rivers, lakes and wetlands). In addition to their SWM benefits, enhanced swales provide aesthetic value as attractive landscaped features.
</br>
{{textbox|Key components of [[Enhanced swales]] to pay close attention to are the:
*[[Inlets]]
*[[Turf|Vegetated Slopes]]
*[[Enhanced swales: Specifications|Slope & Channel Design]]
*[[Overflow|Overflow outlets]]}}
Trash, debris and sediment builds up at these locations and can prevent water from flowing into or out of the practice.
==Associated Practices==
*'''[[Swales: Gallery|Grass Swales]]''': A parabolic or trapezoidal-sized bottom, swale that contains grassed sloping sides and a filter media bottom to both convey overland flow and provide water treatment, and are often subject to more frequent maintenance. They generally contain an outlet structure at the lowest point for water to be sent to another LID BMP or the storm system; sometimes referred to as a roadside ditch. Does not contain check dams.
*'''[[Swales]]''': Swales are linear landscape features consisting of a drainage channel with gently sloping sides. Underground they may be filled with engineered soil and/or contain a water storage layer of coarse gravel material. Two variations on a basic swale are recommended as low impact development strategies, although using a combination of both designs may increase the benefit.
*'''[[Bioswales]]''' are sometimes referred to as 'dry swales', 'vegetated swales', or 'water quality swales'. This type of BMP is form of [[bioretention]] with a long, linear shape (surface area typically >2:1 length:width) and a slope which conveys water and generally contains various water tolerant [[vegetation]]
==Inspection and Testing Framework==
[[File:Storm drain protection.PNG|thumb|330px|Example of a storm drain inlet sediment control measure (sediment retention barrier) used at the bottom of an enhanced swale to limit excess suspended sediment from entering the storm drain outlet at the end of the feature. This type of barrier would generally be in place during construction activity and would be reviewed during construction inspections to ensure its operating efficiently and excess sediment is removed routinely (Source: [https://sustainabletechnologies.ca/app/uploads/2020/01/ESC-Guide-for-Urban-Construction_FINAL.pdf ESC Guide, 2019]<ref name="example1">Toronto and Region Conservation Authority (TRCA). 2019. Erosion and Sediment Control Guideline for Urban Construction. Toronto and Region Conservation Authority, Vaughan, Ontario. https://sustainabletechnologies.ca/app/uploads/2020/01/ESC-Guide-for-Urban-Construction_FINAL.pdf</ref>]]</br>
[[File:Simulated storm event in a swale.PNG|thumb|330px|The image above shows a simulated storm event testing indicator for an enhanced swale taking place at the [https://climate-adapt.eea.europa.eu/metadata/case-studies/climate-proofing-social-housing-landscapes-2013-groundwork-london-and-hammersmith-fulham-council Social Housing Landscapes project located in London, England]. The simulation event occurs by calculating the amount of expected rainfall to occur during a 1-in-100 year event by adding water to the feature with a large municipal watering truck during a 1-hr. event at the same expected magnitude during a natural event to ensure the LID BMP is effectively conveying an filtering stormwater in a real-life scenario (Source: Connop and Nash, 2019)<ref>Connop S. and Nash, C. 2019. A Storm in a Bioswale: Breaking Down Barriers to Nature-Based Solutions. The Nature of Cities. 16 December 2019 Accessed: 4 July 2022. https://www.thenatureofcities.com/2019/12/16/a-storm-in-a-bioswale-breaking-down-barriers-to-nature-based-solutions/</ref>]]
{| class="wikitable" style="width: 900px;"
|+'''Visual Indicators Framework - Enhanced Swales'''
|-
!<br>'''Component'''
!<br>'''Indicators'''
!<br>'''Construction Inspection'''
!<br>'''Assumption Inspection'''
!<br>'''Routine Operation Inspection'''
!<br>'''Verification Inspection'''
|-
|rowspan="2"|'''[[Bioretention: Sizing|Contributing Drainage Area]]'''
|-
|CDA condition
|x
|x
|x
|x
|-
|rowspan="5"|'''[[Inlets|Inlet]]'''
|-
|Inlet/Flow Spreader Structural Integrity
|
|x
|x
|x
|-
|Inlet/Flow Spreader Structural Integrity
|x
|x
|x
|x
|-
|Pretreatment sediment accumulation
|x
|x
|x
|
|-
|Inlet erosion
|
|x
|x
|
|-
|rowspan="4"|'''Perimeter'''
|-
|BMP dimensions
|x
|x
|
|x
|-
|Side slope erosion
|
|x
|x
|
|-
|Surface ponding area
|x
|x
|
|x
|-
|rowspan="8"|'''[[Bioretention: Filter media|Filter Bed]]'''
|-
|Standing water
|
|x
|x
|x
|-
|Trash
|
|x
|x
|
|-
|Filter bed erosion
|
|x
|x
|
|-
|Filter bed sediment accumulation
|
|x
|x
|x
|-
|Surface ponding depth
|x
|x
|
|x
|-
|Filter bed surface sinking
|
|x
|x
|x
|-
|Check dams
|x
|x
|x
|x
|-
|rowspan="4"|'''[[Vegetation|Planting Area]]'''
|-
|Vegetation cover
|x
|x
|x
|x
|-
|Vegetation condition
|
|x
|x
|
|-
|Vegetation composition
|x
|x
|x
|
|-
|rowspan="2"|'''[[Overflow|Outlet]]'''
|-
|Overflow outlet obstruction
|x
|x
|x
|x
|-
|}<br>
{| class="wikitable" style="width: 900px;"
|+'''Testing Indicators Framework - Enhanced Swales'''
|-
!<br>'''Component'''
!<br>'''Indicators'''
!<br>'''Construction Inspection'''
!<br>'''Assumption Inspection'''
!<br>'''Routine Operation Inspection'''
!<br>'''Verification Inspection'''
|-
|rowspan="6"|'''Testing Indicators'''
|-
|Soil characterization testing
|x
|x
|
|(x)
|-
|Sediment accumulation testing
|x
|x
|x
|x
|-
|Surface infiltration rate testing
|
|x
|
|(x)
|-
|Natural or simulated storm event testing
|
|x
|
|(x)
|-
|colspan="7" style="text-align: center;" |'''<u><span title=>Note:''' (x) denotes indicators to be used for Performance Verification inspections only (i.e., not for Maintenance Verification inspections) </span></u>
|-
|}
[[File:Protecting swale durign construction.PNG|thumb|750px|The diagram above depicts the use of an enhanced swale as a temporary detention basin during construction. This practice is avoided at all costs as it can lead to subgrade clogging and compaction, but in the case where LIDs must be used for construction stormwater detention due to site constraints, protection measures can be applied to prevent accumulated sediment from migrating into the subgrade when an LID is first being developed. This method would have to be outlined on the inspection sheet specifically to ensure construction inspection tasks include addressing its condition through all three sequences (Source: TRCA, 2019)<ref name="example1" />]]</br>
==Construction Inspection Tasks==
Construction inspections take place during several points in the construction sequence, specific to the type of LID BMP, but at a minimum should be done '''weekly''' and include the following:
# During site preparation, prior to BMP excavation and grading to ensure the CDA is stabilized or that adequate ESCs or flow diversion devices are in place and confirm that construction materials meet design specifications
# At completion of excavation and grading, prior to installation of pipes/sewers and backfilling to ensure depths, slopes and elevations are acceptable
# Prior to hand-off points in the construction sequence when the contractor is responsible for the work changes (i.e., hand-offs between the storm sewer servicing, paving, building and landscaping contractors
# After every large storm event (e.g., 15 mm rainfall depth or greater) to ensure [https://sustainabletechnologies.ca/app/uploads/2020/01/ESC-Guide-for-Urban-Construction_FINAL.pdf Erosion Sediment Controls (ESCs)] and pretreatment or flow diversion devices are functioning and adequately maintained. View the table below, which describes critical points during the construction sequence when inspections should be performed prior to proceeding further. You can also download and print the table [https://wikidev.sustainabletechnologies.ca/images/d/db/Construction_Inspection_Enhanced_Swale.pdf '''here''']<br>
</br>
[[File:Topsoil depth.jpg|340px|thumb|A rudimentary way for determining topsoil depth of an LID BMP and determining that it is acceptable for the practice (Source: Vidacycle, 2020)<ref>Vidacycle. 2020. Soil Monitoring Guide: Other Soil Tests. Accessed 4 July 2022. https://soils.vidacycle.com/soil-tests/</ref>]]
{| class="wikitable" style="width: 900px;"
|+'''Enhanced Swales: Construction Inspections'''
|-
!<br>'''Construction Sequence Step & Timing'''
!<br>'''Inspection Item'''<br>
!<br>'''<u><span title="Note for Observation Column: S = Satisfactory; U= Unsatisfactory; NA = Not Applicable ">Observations*</u>'''<br>
|-
|rowspan="6"|'''Site Preparation''' - after site clearing and grading, prior to BMP excavation and grading
|Natural heritage system and tree protection areas remain fenced off
|
|-
|ESCs protecting BMP layout area are installed properly
|
|-
|CDA is stabilized or runoff is diverted around BMP layout area
|
|-
|BMP layout area has been cleared and is staked/delineated
|
|-
|Benchmark elevation(s) are established nearby
|
|-
|Construction materials have been confirmed to meet design specifications
|
|-
|rowspan="4"|'''BMP Excavation and Grading''' - prior to landscaping
|Excavation location, footprint, depth and slopes are acceptable
|
|-
|Excavated soil is stockpiled outside the CDA
|
|-
|Embankments/berms (elevations, slopes, compaction) are acceptable
|
|-
|Excavation bottom and sides roughened to reduce smearing and compaction
|
|-
|rowspan="4"|'''Landscaping''' – after final grading, prior to planting
|Topsoil depth, degree of compaction and surface elevations at inlets and outlets are acceptable
|
|-
|Maximum surface ponding depth is acceptable
|
|-
|Filter bed is free of ruts, local depressions and not overly compacted
|
|-
|Planting material meets approved planting plan specifications (plant types and quantities)
|-
|colspan="3" style="text-align: center;" |'''<u><span title=>Note:''' for Observation Column: S = Satisfactory; U = Unsatisfactory; NA = Not Applicable*</span></u>
|-
|}
==Routine Maintenance - Key Components and I&M Tasks==
Regular inspections (twice annually, at a minimum) done as part of routine maintenance tasks over the operating phase of the BMP life cycle to determine if maintenance task frequencies are adequate and determine when rehabilitation or further investigations into BMP function are warranted.
Table below describes routine maintenance tasks for [[bioretention]] practices, organized by BMP component, along with recommended minimum frequencies. It also suggests higher frequencies for certain tasks that may be warranted for BMPs located in highly visible locations or those receiving flow from high traffic areas (vehicle or pedestrian). Tasks involving removal of trash, debris and sediment and weeding/trimming of [[vegetation]] for BMPs in such contexts may need to be done more frequently (i.e., higher standards may be warranted).
Individuals conducting [[vegetation]] maintenance and in particular, weeding (i.e., removal of undesirable vegetation), should be familiar with the species of [[Plant lists|plants]] specified in the planting plan and experienced in plant identification and methods of removing/controlling noxious weeds. Key resources on these topics are provided below at the links provided:
*[http://www.weedinfo.ca/en/ Agriculture and Agri-food Canada’s Weed Info database]
*[http://www.omafra.gov.on.ca/english/crops/facts/ontweeds/weedgal.htm Ontario Ministry of Agriculture, Food and Rural Affairs’ Ontario Weed Gallery]
*[http://www.omafra.gov.on.ca/english/crops/facts/noxious_weeds.htm Ontario Ministry of Agriculture, Food and Rural Affairs’ Noxious Weeds In Ontario list]
*[https://www.ontarioinvasiveplants.ca/wp-content/uploads/2016/07/QRG_FINAL.pdf Ontario Invasive Plant Council’s Quick Reference Guide to Invasive Plant Species]
*[https://wrrc.arizona.edu/sites/wrrc.arizona.edu/files/OSU_Field%20Guide%20-%20Maintaining%20Rain%20Gardens%2C%20Swales%2C%20and%20Stormwater%20Planters.pdf Oregon State University Stormwater Solutions, 2013, Field Guide: Maintaining Rain Gardens, Swales and Stormwater Planters, Corvallis, OR.]
*[https://lonepinebooks.com/product/plants-of-southern-ontario-2/ Plants of Southern Ontario (book), 2014, by Richard Dickinson and France Royer, Lone Pine Publishing, 528 pgs.]
*[http://www.agrifs.ir/sites/default/files/Weeds%20of%20North%20America%20%7BRichard%20Dickinson%7D%20%5B9780226076447%5D%20%282014%29_2.pdf Weeds of North America (book), 2014, by Richard Dickinson and France Royer, University of Chicago Press, 656 pgs.]
{|class="wikitable" style="width: 1280px"
|+'''Enhanced Swales: Key Components, Descriptions and Routine I&M Requirements'''
|-
!style="width: 500px"|Component
!style="width: 1500px"|Description
!style="width: 1500px"|Inspection & Maintenance Tasks
!style="width: 500px"|<span style="color:green">('''Pass''')</span> Photo Example
!style="width: 550px"|<span style="color:red">('''Fail''')</span> Photo Example
|-
|'''[[Enhanced swales: Specifications|Contributing Drainage Area (CDA)]]'''
|
Area(s) from which runoff directed to the BMP originates; includes both impervious and pervious areas.
|
*Remove trash, debris and sediment from pavements (biannually to quarterly) and eavestroughs (annually);
*Replant or seed bare soil areas as needed.
|[[File:CDA Pass swale.PNG|300px|thumb|center|CDA has not changed in size or land cover. Sediment, trash or debris is not accumulating and point sources of contaminants are not visible.]]
|[[File:CDA Fass swale.PNG|280px|thumb|center|Ponding and sediment accumulation on the CDA is visible indicating runoff is not freely entering the BMP and that the pavement has not been swept recently.).]]
|-
|'''[[Pretreatment]]'''
|
Devices or features that retain trash, debris and sediment; help to extend the [[Cost analysis resources|operating life cycle]]; examples are eavestrough screens, [[Pretreatment|catch basin]] inserts and sumps, [[oil and grit separators]], [[inlets|geotextile-lined inlets]], [[Gravel diaphragms|gravel trenches]], [[Vegetated filter strips|grass filter strips]] and [[forebays]].
|
*Remove trash, debris and sediment annually to biannually or when the device sump is half full;
*Measure sediment depth or volume during each cleaning, or annually to estimate accumulation rate and optimize frequency of maintenance
|[[File:Pretreat Pass swale.PNG|310px|thumb|center|The [[Vegetated filter strips|grass filter strip]] pretreatment is free of sediment, trash and debris. (Source: Abbey and Associates).]]
|[[File:Pretreat Fail swale.PNG|310px|thumb|center|Sediment and debris has accumulated in the [[forebay]] and is preventing stormwater from flowing into the BMP]]
|-
|'''[[Inlets]] & [[Overflow: Gallery|Overflow Outlets]]'''
|
Structures that deliver water to the BMP (e.g., [[Curb cuts]], [[inlets|spillways]], pavement edges, [[inlets|catch basins]], [[pipes]]) or [[Flow control|convey flow]] that exceeds the storage capacity of the BMP to another drainage system (i.e. other LID BMP, or storm sewer).
|
*Keep free of obstructions;
*Remove trash, debris and sediment biannually to quarterly;
*Measure sediment depth or volume during each cleaning or annually to estimate accumulation rate and optimize frequency of maintenance;
*Remove woody [[vegetation]] from filter bed at [[inlets]] annually.
|[[File:Inlet Obstruction Pass swale.PNG|340px|thumb|center|There are no obstructions at the inlet and stormwater can freely flow into the BMP.]]
[[File:Overflow Outlet Pass swale.PNG|thumb|center|340px|The overflow outlet elevation and maximum surface ponding area closely match what was specified in the final design.]]
|[[File:Inlet Obstruction Fail swale.PNG|300px|thumb|center|Accumulated sediment and vegetation is preventing stormwater from entering the BMP. Sediment on the pavement surface in front of the inlet indicates ponding is occurring.]]
[[File:Overflow Outlet Fail swale.PNG|300px|thumb|center|The elevation of the overflow outlet is higher than what was specified in the design, producing a much larger surface ponding area than intended which could produce standing water for prolonged periods and cause vegetation to die off.]]
|-
|'''Perimeter'''
|
Side slopes or structures that define the BMP footprint; may be covered by a mixture of [[vegetation]], [[mulch]] and [[stone]] with slopes up to 3:1 (H:V), or concrete or masonry structures with vertical walls.
|
*Confirm the surface ponding footprint area dimensions are within ±10% of the design and that the maximum surface ponding depth behind [[check dams]] meets design specifications;
*Check for side slope erosion/damage from vehicular/foot traffic.
|[[File:Perimeter Pass swale.PNG|315px|thumb|center|The footprint area of the BMP does not significantly deviate from the final design and should not negatively affect its stormwater management treatment performance.]]
|[[File:Perimeter Fail swale.PNG|310px|thumb|center|The footprint area of the BMP is significantly smaller than what was specified in the final design of this example and differ greater than the recommended SWM criteria requirements (>10%), due to half the width having been paved over.]]
|-
|'''[[Enhanced swales: Specifications|Filter Bed]]'''
|
Linearly-oriented, gently sloping area (between 0.5 and 4% [[slope]]) where [[Runoff volume control targets|runoff]] is filtered and conveyed; [[Flow in a swale|parabolic or trapezoidal cross-section]], lined with 20 to 30 cm of planting soil and covered with deep rooting perennial [[grasses]] or a mixture of [[vegetation]] and [[stone]].
|
*Check for standing water, barren/eroded areas, sinkholes or animal burrows;
*Remove trash biannually to quarterly;
*Rake regularly to redistribute [[mulch]] and prevent sediment crusts;
*Mow [[grasses]] to maintain height of > 10 cm;
*For sod or [[turf grass|turf grass]] vegetation cover, aerate and dethatch annually to maintain [[Low permeability soils|soil permeability]] and dense grass cover;
*Repair sunken areas when ≥ 10 cm deep and barren/eroded areas when ≥ 30 cm long;
*Remove sediment when > 5 cm deep or time to drain water ponded behind [[check dams]] exceeds 48 hours.
|[[File:Filter Bed Pass swale.PNG|315px|thumb|center|The filter bed has retained its original grading without any sharp depressions that would indicate surface bed sinking.]]
[[File:Surface ponding Pass Swale.PNG|315px|thumb|center|TThe maximum surface ponding depth behind check dams matches what was specified in the final design. (Source:
Mark M. Holeman, Inc., 2015)<ref>Mark M. Holeman, Inc. 2015. What is a Bio-Swale? Authored by Rick Blankenship. 25 September 2015. Accessed 5 July 2022. http://www.holemanlandscape.com/2015/09/25/what-is-a-bio-swale/</ref>]]
|[[File:Filter Bed Fail swale.PNG|300px|thumb|center|Clear evidence of bed sinking is visible, creating a preferential ponding area where vegetation has died off.]]
[[File:Surface ponding Fail Swale.PNG|300px|thumb|center|The maximum ponding depth of the swale is significantly deeper than intended as the elevation of the check dam or overflow outlet is too high. (Source: Stiffler, 2012<ref>Stiffler, L. 2012.RAIN GARDEN REALITY CHECK: Comparing LID to conventional system failures. Authored by: Eric De Place. 18 April 2012. Sightline Institute. Sustainable Living Series. Accessed 5 July 2022. https://www.sightline.org/2012/04/18/rain-garden-reality-check/</ref>)]]
|-
|'''[[Vegetation]]'''
|
Deep rooting perennial [[grasses]] or a mixture of [[Perennials:_List|wildflowers]] and [[shrubs]], tolerant to both wet and dry conditions and [[salt]]; roots uptake water and return it to the atmosphere, provide habitat for organisms that break down trapped pollutants and help maintain soil structure and permeability
|
*Routine maintenance is the same as a conventional lawn;
*In the first 2 months water plantings frequently (biweekly in the absence or rain) and as needed (e.g., bimonthly) over the remainder of the first growing season;
*Remove weeds and undesirable plants biannually to quarterly;
*Replace dead plantings annually to achieve 80% cover by the third growing season;
*Do not apply chemical fertilizers.
|[[File:Veg Cover Pass swale.PNG|315px|thumb|center|The planted portion of the swale is well covered with dense, attractive vegetation which helps to maintain its stormwater treatment function and aesthetic value.]]
|[[File:Veg Cover Fail swale.PNG|315px|thumb|center|Major portions of the swale surface contains dead or dying vegetation which reduces its aesthetic value and could be negatively affecting its stormwater treatment function.]]
|-
|'''[[Check dams]]'''
|
Structures constructed of a non-erosive material, such as suitably sized [[Reservoir aggregate|aggregate]], wood, gabions, riprap, [[stone]] or concrete; used to slow runoff water. Can be employed in practices such as bioswales and enhanced grass swales. Constructed across a drainage ditch, [[swale]], or channel to lower the speed of concentrated flows for a certain design range of storm events and to promote infiltration.
|
*Remove accumulated sediment by rake/shovel.
*Check for signs of oil or grease contamination (e.g. sheen on surface of water when sediment is submerged). I suspected, submit a sediment sample for contaminant testing by an accredited laboratory to determine the proper disposal method.
*Assess the CDA for changes in land cover or point sources of sediment.
*Inspect and remove sediment from [[pretreatment]] devices.
*If problems persist, consider adding pretreatment devices or increasing frequency of routine maintenance.
|[[File:Check Dam Pass swale.PNG|355px|thumb|center|The check dams are visible and continue to help retain sediment and spread the flow of water across the BMP surface.]]
|[[File:Veg Cover Fail swale.PNG|355px|thumb|center|Sediment has accumulated on the upstream side of the check dam and is affecting its function. (Source: Tennessee EPSC).]]
|-
|}
==Tips to Preserve Basic BMP Function==
*Because the risk of compaction is higher when topsoil is saturated, any maintenance tasks involving vehicle (e.g., ride mower) or foot traffic on the filter bed should not be performed during wet weather.
*Use push mower to maintain enhanced swales with [[grasses]] as [[vegetation]] cover or the lightest ride mower equipment available to minimize compaction of the filter bed.
*Use a mulching mower to maintain enhanced swales with grass as vegetation cover or leave clippings on the surface to help replenish organic matter and nutrients in the topsoil.
*Pruning of mature [[trees]] should be performed under the guidance of a Certified Arborist.
*Woody vegetation should not be planted or allowed to become established where snow will be piled/stored during winter.
*Removal of sediment accumulated on the filter bed surface should be performed by hand with rake and shovel, or vacuum equipment where feasible. If a small excavator is the chosen method, keep the excavator off the BMP footprint to avoid damage to side slopes/embankments and compaction of the [[topsoil]].
==Rehabilitation & Repair==
Table below provides guidance on rehabilitation and repair work specific to enhanced grass swales organized according to BMP component.
[[File:Outlet covered swale.PNG|330px|thumb|link=https://sustainabletechnologies.ca/app/uploads/2018/02/Enhanced-Swales-Fact-Sheet.pdf|An example of an outlet in an enhanced swale requiring maintenance to remove built up debris and sediment. <ref>TRCA. 2018. Inspection and Maintenance of Stormwater Best Management Practices - Enhanced Swales. Fact Sheet. https://sustainabletechnologies.ca/app/uploads/2018/02/Enhanced-Swales-Fact-Sheet.pdf</ref>]]
{|{| class="wikitable" style="width:900px;"
|+'''Enhanced Swales: Key Components, Typical Issues and Rehabilitation Requirements'''
|-
!Component
!Problem
!Rehabilitation Tasks
|-
|'''[[Inlets]]'''
|
Inlets are producing concentrated flow and causing filter bed erosion
|
*Add [[Level spreaders|flow spreading device]] or re-grade existing device back to level. Rake to regrade damaged portion of the filter bed and replant. If problem persists, replace some [[vegetation|plant]] cover with [[stone]].
|-
| rowspan="3"|'''[[Swales: Construction|Filter Bed]]'''
|Local or average sediment accumulation ≥ 5 cm in depth.
|
*At [[inlets]] remove [[stone]] and use vacuum equipment or rake and shovel to remove sediment. For large areas or BMPs, use of a small excavator may be preferable. Restore grades with planting soil that meets design specifications. Test surface infiltration rate to confirm it is > 15 mm/h. Replace [[stone]] and [[vegetation]] coverage (re-use/transplant where possible). If problem persists, add [[pretreatment]] device(s) or investigate the source(s).
|-
|Surface ponding remains for > 48 hours or surface infiltration rate is < 15 mm/h.
|
*Remove sediment as described above. Core aerate (for grass swales); or remove [[stone]], sediment and [[vegetation|plant]] cover and till 5 cm of yard waste compost into the exposed planting [[Soil groups|soil]] to a depth of 20 cm; or remove and replace the uppermost 15 cm of material with planting soil that meets design specifications. Test [[Infiltration: Testing|surface infiltration rate]] to confirm it has been restored to > 15 mm/h. Replace stone and plants (re-use/transplant where possible).
|-
|Damage to filter bed or slide slope is present (e.g., [[erosion]] rills, animal burrows, sink holes, ruts)
|
*Regrade damaged portion by raking and replant or restore [[stone]] cover. Animal burrows, sink holes and compacted areas should be tilled to 20 cm depth prior to re-grading. If problems persist, consider adding [[Level spreaders|flow spreading device]] to prevent [[erosion]] or barriers to discourage foot or vehicular traffic.
|-
|'''[[Vegetation]]'''
|
Plants not thriving and planting soil is low in organic matter (<5%) or available [[Nutrients|phosphorus]] (<12 mg/kg)
|
*Remove [[stone]] and [[vegetation|plant]] cover and uppermost 5 cm of planting soil, spread 5 cm of yard waste compost, incorporate into [[Soil groups|soil]] to 20 cm depth by tilling. Replace stone and plants (re-use/transplant where possible).
|-
|}
==Inspection Time Commitments and Costs==
Estimates are based on a typical partial infiltration bioretention design (i.e., includes a sub-drain); estimates for other designs (i.e., full infiltration and no-infiltration) can be found in the [https://sustainabletechnologies.ca/app/uploads/2016/08/LID-IM-Guide-7.1-Bioretention-and-Dry-Swales.pdf Low Impact Development (LID) Stormwater Management Practice Inspection and Maintenance Guide]<br>
</br>
[[File:Time commit cost swale.PNG|thumb|left|400px|General time commitments and costs for inspection of enhanced swale features (in 2016 $ figures).<ref>TRCA. 2018. Inspection and Maintenance of Stormwater Best Management Practices. Bioretention - Fact Sheet. https://sustainabletechnologies.ca/app/uploads/2018/02/Bioretention-and-Dry-Swales-Fact-Sheet.pdf</ref>]]
[[File:Per-task cost estimate swale.PNG|thumb|400px|Per-task cost estimates for maintenance and rehabilitation of enhanced swale features (in 2016 $ figures).<ref>TRCA. 2018. Inspection and Maintenance of Stormwater Best Management Practices. Bioretention - Fact Sheet. https://sustainabletechnologies.ca/app/uploads/2018/02/Bioretention-and-Dry-Swales-Fact-Sheet.pdf</ref>]]
[[File:Construction life cycle cost swale.PNG|thumb|center|400px|Construction and life cycle cost estimates for enhanced swale features (in 2016 $ figures).<ref>TRCA. 2018. Inspection and Maintenance of Stormwater Best Management Practices. Bioretention - Fact Sheet. https://sustainabletechnologies.ca/app/uploads/2018/02/Bioretention-and-Dry-Swales-Fact-Sheet.pdf</ref>]]<br>
</br>
</br>
</br>
</br>
</br>
</br>
Estimates of the life cycle costs of inspection and maintenance have been produced using the latest version of the [[Cost analysis resources|LID Life Cycle Costing Tool]] for three design variations (full infiltration, partial infiltration and no infiltration) to assist stormwater infrastructure planners, designers and asset managers with planning and preparing budgets for potential LID features.
Assumptions for the above costs and the following table below are based on the following:
*Capital costs included within the category of construction include those related to site assessment, and conceptual and detailed design related tasks such as borehole analysis and soil testing. All material, delivery, labour, equipment (rental, operation, operator), hauling and disposal costs are accounted for within the construction costs of the facility. Standard union costs were derived from the RSMeans database in 2010 and have been adjusted for 5 year inflation of 8.79% (2010 to June, 2015).
**Costs include overhead and inflation to represent contractor pricing. It was assumed the practice is part of a new development (i.e., not a retrofit), thereby excluding (de)mobilization costs unless a particular piece of equipment would not normally have been present at the site. Additionally, it was assumed that excavated soil associated with construction of the BMP would be reused elsewhere on site. Overhead costs were presumed to consist of construction management (4.5%), design (2.5%), small tools (0.5%), clean up (0.3%) and other (2.2%).
*For maintenance frequencies and requirements and the life span of each practice are based on both literature and practical experience. Life cycle and associated maintenance costs are evaluated over a 50 year timeframe, which is the typical period over which infrastructure decisions are made.
*For enhanced grass swales it is assumed that some rehabilitation (e.g., rehabilitative maintenance) work will be needed on the filter bed surface once the BMP reaches 25 and 50 years of age in order to maintain functional drainage performance at an acceptable level. Included in the rehabilitation costs are (de)mobilization costs, as equipment would not have been present on site. Design costs were not included in the rehabilitation as it was assumed that the original LID practice design would be used to inform this work. The annual average maintenance cost does not include rehabilitation costs and therefore represents an average of routine maintenance tasks, as outlined in the Table under section, [[Inspection and Maintenance: Enhanced Swales#Routine Maintenance - Key Components and I&M Tasks|Routine Maintenance - Key Components and I&M Tasks]] above. All cost value estimates represent the net present value (NPV) as the calculation takes into account average annual interest (2%) and discount (3%) rates over the evaluation time periods.
*For all enhanced swale design variations, the CDA has been defined as a 2,000 m2 impervious pavement area plus the footprint area of a bioretention cell that is 133 m2 in size, as per design recommendations. The impervious area to pervious area ratio (I:P ratio) used to size the BMP footprint is 15:1, which is the maximum ratio recommended in the LID SWM Planning and Design Guide (CVC & TRCA, 2010)<ref>CVC and TRCA. 2010. Low Impact Development Stormwater Management Planning and Design Guide. Version 1.0. https://cvc.ca/wp-content/uploads/2014/04/LID-SWM-Guide-v1.0_2010_1_no-appendices.pdf</ref>. It is assumed that water drains to the cell through curb inlets spaced 6 m apart with stone cover on the filter bed at the inlets to dissipate the energy of the flowing water.
*Estimates of the life cycle costs of Enhanced Swales in Canadian dollars per unit CDA ($/m2) are presented in the table below. The [[Cost analysis resources|LID Life Cycle Costing Tool]] allows users to select what BMP type and design variation applies, and to use the default assumptions to generate planning level cost estimates.
**Users can also input their own values relating to a site or area, design, unit costs, and inspection and maintenance task frequencies to generate customized cost estimates, specific to a certain project, context or stormwater infrastructure program.
**For all BMP design variations and maintenance scenarios, it is assumed that rehabilitation of part or all of the filter bed surface will be necessary once the BMP reaches 25 and 50 years of age to maintain acceptable surface drainage performance (e.g., surface ponding drainage time). Filter bed rehabilitation for enhanced swales is assumed to typically involve the tasks outlined under section, [[Inspection and Maintenance: Enhanced Swales#Routine Maintenance - Key Components and I&M Tasks|Routine Maintenance - Key Components and I&M Tasks]] above.<br>
</br>
[[File:Life cycle costs swales.PNG|thumb|center|900px|Life cycle cost estimates for all variation types of [[enhanced swales]] under minimum and high frequency scenarios (in 2016 $ figures).<ref>TRCA. 2018. Inspection and Maintenance of Stormwater Best Management Practices. Bioretention - Fact Sheet. https://sustainabletechnologies.ca/app/uploads/2018/02/Bioretention-and-Dry-Swales-Fact-Sheet.pdf</ref>]]
'''Notes:'''
<small>
#Estimated life cycle costs represent NPV of associated costs in Canadian dollars per square metre of CDA ($/m2).
#Average annual maintenance cost estimates represent NPV of all costs incurred over the time period and do not include rehabilitation costs.
#Rehabilitation cost estimates represent NPV of all costs related to repair work assumed to occur every 25 years including those associated with inspection and maintenance over a two (2) year establishment period for the plantings.
#Life cycle costs are very similar but slightly lower for BMPs constructed with filter sock or rock check dams, than concrete ones due to differences in material and labor unit costs.
#Rehabilitation costs are estimated to be between 24.4 to 28.1% of the original construction costs for High Frequency and Minimum Recommended maintenance program scenarios, respectively.
# Maintenance and rehabilitation costs over a 25 year time period are estimated to be 1.77 to 2.66 times the original construction cost, for the Minimum Recommended and High Frequency maintenance scenarios respectively, depending on check dam construction material.
# Maintenance and rehabilitation costs over a 50 year time period are estimated to be 3.13 and 4.74 times the original construction cost for the Minimum Recommended and High Frequency maintenance scenarios respectively, depending on check dam construction material.</small>
==Inspection Field Data Sheet==
Feel free to '''download''' (downward facing arrow on the top righthand side) and '''print''' (Pinter emoticon on top right hand side) the following [[enhanced swales|Enhanced Swale]] Inspection Field Data Form developed by TRCA, STEP and its partners for the [https://sustainabletechnologies.ca/app/uploads/2016/08/LID-IM-Guide-2016-1.pdf Low Impact Development Stormwater Management Practice Inspection and Maintenance Guide]<ref>STEP. 2016. Low Impact Development Stormwater Management Practice Inspection and Maintenance Guide. https://sustainabletechnologies.ca/app/uploads/2016/08/LID-IM-Guide-2016-1.pdf</ref>.
The 6 page document prompts users to fill out details previously mentioned above on this page in other sections about various zones associated with [[Enhanced swales|Enhanced swale]] features (i.e. inlets, perimeter of the feature, filter bed, outlets, etc.) and describe why each area is a pass or fail, and if remediate action is required and under what timeframe it would be completed by. Furthermore, the forms prompt the reviewer to determine what type of inspection is being conducted for the feature in question: Construction (C), Routine Operation (RO), Maintenance Verification (MV), or Performance Verification (PV). <br>
<br>
[[File:Newly developed swale.PNG|thumb|330px|Example of a newly developed enhanced swale in a recently developed subdivision.]]
<pdf width="900" height="800">File:Swales inspection sheet.pdf</pdf>
==References==
{{TOClimit|2}}
==Overview==
[[Enhanced swales]] are gently sloping vegetated open channels featuring a parabolic or trapezoidal cross-section and check dams, designed to convey and treat stormwater runoff (i.e., rainwater or snowmelt from roofs or pavements). The [[grading]], [[Check dams]] and [[vegetation]] spreads out and slows down the flow of water, allowing suspended sediment and floatables (e.g., trash, natural debris, oil and grease) to settle out. A portion of the flowing water soaks into the soil and replenishes groundwater or is taken up by plant roots and evaporated back to the atmosphere. Runoff water is delivered to the practice through [[inlets]] such as [[curb cuts]], [[Curb cuts: Gallery|spillways]] or other concrete structures, sheet flow from pavement edges, or [[pipes]] connected to [[Pretreatment|catchbasins]] or [[Downspout disconnection|roof downspouts]]. The [[Plant lists|planting bed]] and side [[slopes]] are typically covered with [[grasses]] or a mixture of flood tolerant, [[erosion]] resistant [[vegetation]] and [[stone]]. They do not feature [[filter media]] soil and [[underdrains|sub-drains]] like [[bioretention]] or [[bioswales]] do. Water not ponded behind check dams or absorbed by the planting bed is conveyed to an adjacent drainage system (e.g., municipal storm sewer or other BMP) at the lowest downstream point by an [[Overflow|outlet structure]] (e.g., ditch inlet catchbasin, culvert). Key components of this feature are described in further detail below. <br>
</br>
Properly functioning enhanced swales reduce the quantity of pollutants and runoff being discharged to municipal storm sewers and receiving waters (i.e., rivers, lakes and wetlands). In addition to their SWM benefits, enhanced swales provide aesthetic value as attractive landscaped features.
</br>
{{textbox|Key components of [[Enhanced swales]] to pay close attention to are the:
*[[Inlets]]
*[[Turf|Vegetated Slopes]]
*[[Enhanced swales: Specifications|Slope & Channel Design]]
*[[Overflow|Overflow outlets]]}}
Trash, debris and sediment builds up at these locations and can prevent water from flowing into or out of the practice.
==Associated Practices==
*'''[[Swales: Gallery|Grass Swales]]''': A parabolic or trapezoidal-sized bottom, swale that contains grassed sloping sides and a filter media bottom to both convey overland flow and provide water treatment, and are often subject to more frequent maintenance. They generally contain an outlet structure at the lowest point for water to be sent to another LID BMP or the storm system; sometimes referred to as a roadside ditch. Does not contain check dams.
*'''[[Swales]]''': Swales are linear landscape features consisting of a drainage channel with gently sloping sides. Underground they may be filled with engineered soil and/or contain a water storage layer of coarse gravel material. Two variations on a basic swale are recommended as low impact development strategies, although using a combination of both designs may increase the benefit.
*'''[[Bioswales]]''' are sometimes referred to as 'dry swales', 'vegetated swales', or 'water quality swales'. This type of BMP is form of [[bioretention]] with a long, linear shape (surface area typically >2:1 length:width) and a slope which conveys water and generally contains various water tolerant [[vegetation]]
==Inspection and Testing Framework==
[[File:Storm drain protection.PNG|thumb|330px|Example of a storm drain inlet sediment control measure (sediment retention barrier) used at the bottom of an enhanced swale to limit excess suspended sediment from entering the storm drain outlet at the end of the feature. This type of barrier would generally be in place during construction activity and would be reviewed during construction inspections to ensure its operating efficiently and excess sediment is removed routinely (Source: [https://sustainabletechnologies.ca/app/uploads/2020/01/ESC-Guide-for-Urban-Construction_FINAL.pdf ESC Guide, 2019]<ref name="example1">Toronto and Region Conservation Authority (TRCA). 2019. Erosion and Sediment Control Guideline for Urban Construction. Toronto and Region Conservation Authority, Vaughan, Ontario. https://sustainabletechnologies.ca/app/uploads/2020/01/ESC-Guide-for-Urban-Construction_FINAL.pdf</ref>]]</br>
[[File:Simulated storm event in a swale.PNG|thumb|330px|The image above shows a simulated storm event testing indicator for an enhanced swale taking place at the [https://climate-adapt.eea.europa.eu/metadata/case-studies/climate-proofing-social-housing-landscapes-2013-groundwork-london-and-hammersmith-fulham-council Social Housing Landscapes project located in London, England]. The simulation event occurs by calculating the amount of expected rainfall to occur during a 1-in-100 year event by adding water to the feature with a large municipal watering truck during a 1-hr. event at the same expected magnitude during a natural event to ensure the LID BMP is effectively conveying an filtering stormwater in a real-life scenario (Source: Connop and Nash, 2019)<ref>Connop S. and Nash, C. 2019. A Storm in a Bioswale: Breaking Down Barriers to Nature-Based Solutions. The Nature of Cities. 16 December 2019 Accessed: 4 July 2022. https://www.thenatureofcities.com/2019/12/16/a-storm-in-a-bioswale-breaking-down-barriers-to-nature-based-solutions/</ref>]]
{| class="wikitable" style="width: 900px;"
|+'''Visual Indicators Framework - Enhanced Swales'''
|-
!<br>'''Component'''
!<br>'''Indicators'''
!<br>'''Construction Inspection'''
!<br>'''Assumption Inspection'''
!<br>'''Routine Operation Inspection'''
!<br>'''Verification Inspection'''
|-
|rowspan="2"|'''[[Bioretention: Sizing|Contributing Drainage Area]]'''
|-
|CDA condition
|x
|x
|x
|x
|-
|rowspan="5"|'''[[Inlets|Inlet]]'''
|-
|Inlet/Flow Spreader Structural Integrity
|
|x
|x
|x
|-
|Inlet/Flow Spreader Structural Integrity
|x
|x
|x
|x
|-
|Pretreatment sediment accumulation
|x
|x
|x
|
|-
|Inlet erosion
|
|x
|x
|
|-
|rowspan="4"|'''Perimeter'''
|-
|BMP dimensions
|x
|x
|
|x
|-
|Side slope erosion
|
|x
|x
|
|-
|Surface ponding area
|x
|x
|
|x
|-
|rowspan="8"|'''[[Bioretention: Filter media|Filter Bed]]'''
|-
|Standing water
|
|x
|x
|x
|-
|Trash
|
|x
|x
|
|-
|Filter bed erosion
|
|x
|x
|
|-
|Filter bed sediment accumulation
|
|x
|x
|x
|-
|Surface ponding depth
|x
|x
|
|x
|-
|Filter bed surface sinking
|
|x
|x
|x
|-
|Check dams
|x
|x
|x
|x
|-
|rowspan="4"|'''[[Vegetation|Planting Area]]'''
|-
|Vegetation cover
|x
|x
|x
|x
|-
|Vegetation condition
|
|x
|x
|
|-
|Vegetation composition
|x
|x
|x
|
|-
|rowspan="2"|'''[[Overflow|Outlet]]'''
|-
|Overflow outlet obstruction
|x
|x
|x
|x
|-
|}<br>
{| class="wikitable" style="width: 900px;"
|+'''Testing Indicators Framework - Enhanced Swales'''
|-
!<br>'''Component'''
!<br>'''Indicators'''
!<br>'''Construction Inspection'''
!<br>'''Assumption Inspection'''
!<br>'''Routine Operation Inspection'''
!<br>'''Verification Inspection'''
|-
|rowspan="6"|'''Testing Indicators'''
|-
|Soil characterization testing
|x
|x
|
|(x)
|-
|Sediment accumulation testing
|x
|x
|x
|x
|-
|Surface infiltration rate testing
|
|x
|
|(x)
|-
|Natural or simulated storm event testing
|
|x
|
|(x)
|-
|colspan="7" style="text-align: center;" |'''<u><span title=>Note:''' (x) denotes indicators to be used for Performance Verification inspections only (i.e., not for Maintenance Verification inspections) </span></u>
|-
|}
[[File:Protecting swale durign construction.PNG|thumb|750px|The diagram above depicts the use of an enhanced swale as a temporary detention basin during construction. This practice is avoided at all costs as it can lead to subgrade clogging and compaction, but in the case where LIDs must be used for construction stormwater detention due to site constraints, protection measures can be applied to prevent accumulated sediment from migrating into the subgrade when an LID is first being developed. This method would have to be outlined on the inspection sheet specifically to ensure construction inspection tasks include addressing its condition through all three sequences (Source: TRCA, 2019)<ref name="example1" />]]</br>
==Construction Inspection Tasks==
Construction inspections take place during several points in the construction sequence, specific to the type of LID BMP, but at a minimum should be done '''weekly''' and include the following:
# During site preparation, prior to BMP excavation and grading to ensure the CDA is stabilized or that adequate ESCs or flow diversion devices are in place and confirm that construction materials meet design specifications
# At completion of excavation and grading, prior to installation of pipes/sewers and backfilling to ensure depths, slopes and elevations are acceptable
# Prior to hand-off points in the construction sequence when the contractor is responsible for the work changes (i.e., hand-offs between the storm sewer servicing, paving, building and landscaping contractors
# After every large storm event (e.g., 15 mm rainfall depth or greater) to ensure [https://sustainabletechnologies.ca/app/uploads/2020/01/ESC-Guide-for-Urban-Construction_FINAL.pdf Erosion Sediment Controls (ESCs)] and pretreatment or flow diversion devices are functioning and adequately maintained. View the table below, which describes critical points during the construction sequence when inspections should be performed prior to proceeding further. You can also download and print the table [https://wikidev.sustainabletechnologies.ca/images/d/db/Construction_Inspection_Enhanced_Swale.pdf '''here''']<br>
</br>
[[File:Topsoil depth.jpg|340px|thumb|A rudimentary way for determining topsoil depth of an LID BMP and determining that it is acceptable for the practice (Source: Vidacycle, 2020)<ref>Vidacycle. 2020. Soil Monitoring Guide: Other Soil Tests. Accessed 4 July 2022. https://soils.vidacycle.com/soil-tests/</ref>]]
{| class="wikitable" style="width: 900px;"
|+'''Enhanced Swales: Construction Inspections'''
|-
!<br>'''Construction Sequence Step & Timing'''
!<br>'''Inspection Item'''<br>
!<br>'''<u><span title="Note for Observation Column: S = Satisfactory; U= Unsatisfactory; NA = Not Applicable ">Observations*</u>'''<br>
|-
|rowspan="6"|'''Site Preparation''' - after site clearing and grading, prior to BMP excavation and grading
|Natural heritage system and tree protection areas remain fenced off
|
|-
|ESCs protecting BMP layout area are installed properly
|
|-
|CDA is stabilized or runoff is diverted around BMP layout area
|
|-
|BMP layout area has been cleared and is staked/delineated
|
|-
|Benchmark elevation(s) are established nearby
|
|-
|Construction materials have been confirmed to meet design specifications
|
|-
|rowspan="4"|'''BMP Excavation and Grading''' - prior to landscaping
|Excavation location, footprint, depth and slopes are acceptable
|
|-
|Excavated soil is stockpiled outside the CDA
|
|-
|Embankments/berms (elevations, slopes, compaction) are acceptable
|
|-
|Excavation bottom and sides roughened to reduce smearing and compaction
|
|-
|rowspan="4"|'''Landscaping''' – after final grading, prior to planting
|Topsoil depth, degree of compaction and surface elevations at inlets and outlets are acceptable
|
|-
|Maximum surface ponding depth is acceptable
|
|-
|Filter bed is free of ruts, local depressions and not overly compacted
|
|-
|Planting material meets approved planting plan specifications (plant types and quantities)
|-
|colspan="3" style="text-align: center;" |'''<u><span title=>Note:''' for Observation Column: S = Satisfactory; U = Unsatisfactory; NA = Not Applicable*</span></u>
|-
|}
==Routine Maintenance - Key Components and I&M Tasks==
Regular inspections (twice annually, at a minimum) done as part of routine maintenance tasks over the operating phase of the BMP life cycle to determine if maintenance task frequencies are adequate and determine when rehabilitation or further investigations into BMP function are warranted.
Table below describes routine maintenance tasks for [[bioretention]] practices, organized by BMP component, along with recommended minimum frequencies. It also suggests higher frequencies for certain tasks that may be warranted for BMPs located in highly visible locations or those receiving flow from high traffic areas (vehicle or pedestrian). Tasks involving removal of trash, debris and sediment and weeding/trimming of [[vegetation]] for BMPs in such contexts may need to be done more frequently (i.e., higher standards may be warranted).
Individuals conducting [[vegetation]] maintenance and in particular, weeding (i.e., removal of undesirable vegetation), should be familiar with the species of [[Plant lists|plants]] specified in the planting plan and experienced in plant identification and methods of removing/controlling noxious weeds. Key resources on these topics are provided below at the links provided:
*[http://www.weedinfo.ca/en/ Agriculture and Agri-food Canada’s Weed Info database]
*[http://www.omafra.gov.on.ca/english/crops/facts/ontweeds/weedgal.htm Ontario Ministry of Agriculture, Food and Rural Affairs’ Ontario Weed Gallery]
*[http://www.omafra.gov.on.ca/english/crops/facts/noxious_weeds.htm Ontario Ministry of Agriculture, Food and Rural Affairs’ Noxious Weeds In Ontario list]
*[https://www.ontarioinvasiveplants.ca/wp-content/uploads/2016/07/QRG_FINAL.pdf Ontario Invasive Plant Council’s Quick Reference Guide to Invasive Plant Species]
*[https://wrrc.arizona.edu/sites/wrrc.arizona.edu/files/OSU_Field%20Guide%20-%20Maintaining%20Rain%20Gardens%2C%20Swales%2C%20and%20Stormwater%20Planters.pdf Oregon State University Stormwater Solutions, 2013, Field Guide: Maintaining Rain Gardens, Swales and Stormwater Planters, Corvallis, OR.]
*[https://lonepinebooks.com/product/plants-of-southern-ontario-2/ Plants of Southern Ontario (book), 2014, by Richard Dickinson and France Royer, Lone Pine Publishing, 528 pgs.]
*[http://www.agrifs.ir/sites/default/files/Weeds%20of%20North%20America%20%7BRichard%20Dickinson%7D%20%5B9780226076447%5D%20%282014%29_2.pdf Weeds of North America (book), 2014, by Richard Dickinson and France Royer, University of Chicago Press, 656 pgs.]
{|class="wikitable" style="width: 1280px"
|+'''Enhanced Swales: Key Components, Descriptions and Routine I&M Requirements'''
|-
!style="width: 500px"|Component
!style="width: 1500px"|Description
!style="width: 1500px"|Inspection & Maintenance Tasks
!style="width: 500px"|<span style="color:green">('''Pass''')</span> Photo Example
!style="width: 550px"|<span style="color:red">('''Fail''')</span> Photo Example
|-
|'''[[Enhanced swales: Specifications|Contributing Drainage Area (CDA)]]'''
|
Area(s) from which runoff directed to the BMP originates; includes both impervious and pervious areas.
|
*Remove trash, debris and sediment from pavements (biannually to quarterly) and eavestroughs (annually);
*Replant or seed bare soil areas as needed.
|[[File:CDA Pass swale.PNG|300px|thumb|center|CDA has not changed in size or land cover. Sediment, trash or debris is not accumulating and point sources of contaminants are not visible.]]
|[[File:CDA Fass swale.PNG|280px|thumb|center|Ponding and sediment accumulation on the CDA is visible indicating runoff is not freely entering the BMP and that the pavement has not been swept recently.).]]
|-
|'''[[Pretreatment]]'''
|
Devices or features that retain trash, debris and sediment; help to extend the [[Cost analysis resources|operating life cycle]]; examples are eavestrough screens, [[Pretreatment|catch basin]] inserts and sumps, [[oil and grit separators]], [[inlets|geotextile-lined inlets]], [[Gravel diaphragms|gravel trenches]], [[Vegetated filter strips|grass filter strips]] and [[forebays]].
|
*Remove trash, debris and sediment annually to biannually or when the device sump is half full;
*Measure sediment depth or volume during each cleaning, or annually to estimate accumulation rate and optimize frequency of maintenance
|[[File:Pretreat Pass swale.PNG|310px|thumb|center|The [[Vegetated filter strips|grass filter strip]] pretreatment is free of sediment, trash and debris. (Source: Abbey and Associates).]]
|[[File:Pretreat Fail swale.PNG|310px|thumb|center|Sediment and debris has accumulated in the [[forebay]] and is preventing stormwater from flowing into the BMP]]
|-
|'''[[Inlets]] & [[Overflow: Gallery|Overflow Outlets]]'''
|
Structures that deliver water to the BMP (e.g., [[Curb cuts]], [[inlets|spillways]], pavement edges, [[inlets|catch basins]], [[pipes]]) or [[Flow control|convey flow]] that exceeds the storage capacity of the BMP to another drainage system (i.e. other LID BMP, or storm sewer).
|
*Keep free of obstructions;
*Remove trash, debris and sediment biannually to quarterly;
*Measure sediment depth or volume during each cleaning or annually to estimate accumulation rate and optimize frequency of maintenance;
*Remove woody [[vegetation]] from filter bed at [[inlets]] annually.
|[[File:Inlet Obstruction Pass swale.PNG|340px|thumb|center|There are no obstructions at the inlet and stormwater can freely flow into the BMP.]]
[[File:Overflow Outlet Pass swale.PNG|thumb|center|340px|The overflow outlet elevation and maximum surface ponding area closely match what was specified in the final design.]]
|[[File:Inlet Obstruction Fail swale.PNG|300px|thumb|center|Accumulated sediment and vegetation is preventing stormwater from entering the BMP. Sediment on the pavement surface in front of the inlet indicates ponding is occurring.]]
[[File:Overflow Outlet Fail swale.PNG|300px|thumb|center|The elevation of the overflow outlet is higher than what was specified in the design, producing a much larger surface ponding area than intended which could produce standing water for prolonged periods and cause vegetation to die off.]]
|-
|'''Perimeter'''
|
Side slopes or structures that define the BMP footprint; may be covered by a mixture of [[vegetation]], [[mulch]] and [[stone]] with slopes up to 3:1 (H:V), or concrete or masonry structures with vertical walls.
|
*Confirm the surface ponding footprint area dimensions are within ±10% of the design and that the maximum surface ponding depth behind [[check dams]] meets design specifications;
*Check for side slope erosion/damage from vehicular/foot traffic.
|[[File:Perimeter Pass swale.PNG|315px|thumb|center|The footprint area of the BMP does not significantly deviate from the final design and should not negatively affect its stormwater management treatment performance.]]
|[[File:Perimeter Fail swale.PNG|310px|thumb|center|The footprint area of the BMP is significantly smaller than what was specified in the final design of this example and differ greater than the recommended SWM criteria requirements (>10%), due to half the width having been paved over.]]
|-
|'''[[Enhanced swales: Specifications|Filter Bed]]'''
|
Linearly-oriented, gently sloping area (between 0.5 and 4% [[slope]]) where [[Runoff volume control targets|runoff]] is filtered and conveyed; [[Flow in a swale|parabolic or trapezoidal cross-section]], lined with 20 to 30 cm of planting soil and covered with deep rooting perennial [[grasses]] or a mixture of [[vegetation]] and [[stone]].
|
*Check for standing water, barren/eroded areas, sinkholes or animal burrows;
*Remove trash biannually to quarterly;
*Rake regularly to redistribute [[mulch]] and prevent sediment crusts;
*Mow [[grasses]] to maintain height of > 10 cm;
*For sod or [[turf grass|turf grass]] vegetation cover, aerate and dethatch annually to maintain [[Low permeability soils|soil permeability]] and dense grass cover;
*Repair sunken areas when ≥ 10 cm deep and barren/eroded areas when ≥ 30 cm long;
*Remove sediment when > 5 cm deep or time to drain water ponded behind [[check dams]] exceeds 48 hours.
|[[File:Filter Bed Pass swale.PNG|315px|thumb|center|The filter bed has retained its original grading without any sharp depressions that would indicate surface bed sinking.]]
[[File:Surface ponding Pass Swale.PNG|315px|thumb|center|TThe maximum surface ponding depth behind check dams matches what was specified in the final design. (Source:
Mark M. Holeman, Inc., 2015)<ref>Mark M. Holeman, Inc. 2015. What is a Bio-Swale? Authored by Rick Blankenship. 25 September 2015. Accessed 5 July 2022. http://www.holemanlandscape.com/2015/09/25/what-is-a-bio-swale/</ref>]]
|[[File:Filter Bed Fail swale.PNG|300px|thumb|center|Clear evidence of bed sinking is visible, creating a preferential ponding area where vegetation has died off.]]
[[File:Surface ponding Fail Swale.PNG|300px|thumb|center|The maximum ponding depth of the swale is significantly deeper than intended as the elevation of the check dam or overflow outlet is too high. (Source: Stiffler, 2012<ref>Stiffler, L. 2012.RAIN GARDEN REALITY CHECK: Comparing LID to conventional system failures. Authored by: Eric De Place. 18 April 2012. Sightline Institute. Sustainable Living Series. Accessed 5 July 2022. https://www.sightline.org/2012/04/18/rain-garden-reality-check/</ref>)]]
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|'''[[Vegetation]]'''
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Deep rooting perennial [[grasses]] or a mixture of [[Perennials:_List|wildflowers]] and [[shrubs]], tolerant to both wet and dry conditions and [[salt]]; roots uptake water and return it to the atmosphere, provide habitat for organisms that break down trapped pollutants and help maintain soil structure and permeability
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*Routine maintenance is the same as a conventional lawn;
*In the first 2 months water plantings frequently (biweekly in the absence or rain) and as needed (e.g., bimonthly) over the remainder of the first growing season;
*Remove weeds and undesirable plants biannually to quarterly;
*Replace dead plantings annually to achieve 80% cover by the third growing season;
*Do not apply chemical fertilizers.
|[[File:Veg Cover Pass swale.PNG|315px|thumb|center|The planted portion of the swale is well covered with dense, attractive vegetation which helps to maintain its stormwater treatment function and aesthetic value.]]
|[[File:Veg Cover Fail swale.PNG|315px|thumb|center|Major portions of the swale surface contains dead or dying vegetation which reduces its aesthetic value and could be negatively affecting its stormwater treatment function.]]
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|'''[[Check dams]]'''
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Structures constructed of a non-erosive material, such as suitably sized [[Reservoir aggregate|aggregate]], wood, gabions, riprap, [[stone]] or concrete; used to slow runoff water. Can be employed in practices such as bioswales and enhanced grass swales. Constructed across a drainage ditch, [[swale]], or channel to lower the speed of concentrated flows for a certain design range of storm events and to promote infiltration.
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*Remove accumulated sediment by rake/shovel.
*Check for signs of oil or grease contamination (e.g. sheen on surface of water when sediment is submerged). I suspected, submit a sediment sample for contaminant testing by an accredited laboratory to determine the proper disposal method.
*Assess the CDA for changes in land cover or point sources of sediment.
*Inspect and remove sediment from [[pretreatment]] devices.
*If problems persist, consider adding pretreatment devices or increasing frequency of routine maintenance.
|[[File:Check Dam Pass swale.PNG|355px|thumb|center|The check dams are visible and continue to help retain sediment and spread the flow of water across the BMP surface.]]
|[[File:Veg Cover Fail swale.PNG|355px|thumb|center|Sediment has accumulated on the upstream side of the check dam and is affecting its function. (Source: Tennessee EPSC).]]
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==Tips to Preserve Basic BMP Function==
*Because the risk of compaction is higher when topsoil is saturated, any maintenance tasks involving vehicle (e.g., ride mower) or foot traffic on the filter bed should not be performed during wet weather.
*Use push mower to maintain enhanced swales with [[grasses]] as [[vegetation]] cover or the lightest ride mower equipment available to minimize compaction of the filter bed.
*Use a mulching mower to maintain enhanced swales with grass as vegetation cover or leave clippings on the surface to help replenish organic matter and nutrients in the topsoil.
*Pruning of mature [[trees]] should be performed under the guidance of a Certified Arborist.
*Woody vegetation should not be planted or allowed to become established where snow will be piled/stored during winter.
*Removal of sediment accumulated on the filter bed surface should be performed by hand with rake and shovel, or vacuum equipment where feasible. If a small excavator is the chosen method, keep the excavator off the BMP footprint to avoid damage to side slopes/embankments and compaction of the [[topsoil]].
==Rehabilitation & Repair==
Table below provides guidance on rehabilitation and repair work specific to enhanced grass swales organized according to BMP component.
[[File:Outlet covered swale.PNG|330px|thumb|link=https://sustainabletechnologies.ca/app/uploads/2018/02/Enhanced-Swales-Fact-Sheet.pdf|An example of an outlet in an enhanced swale requiring maintenance to remove built up debris and sediment. <ref>TRCA. 2018. Inspection and Maintenance of Stormwater Best Management Practices - Enhanced Swales. Fact Sheet. https://sustainabletechnologies.ca/app/uploads/2018/02/Enhanced-Swales-Fact-Sheet.pdf</ref>]]
{|{| class="wikitable" style="width:900px;"
|+'''Enhanced Swales: Key Components, Typical Issues and Rehabilitation Requirements'''
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!Component
!Problem
!Rehabilitation Tasks
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|'''[[Inlets]]'''
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Inlets are producing concentrated flow and causing filter bed erosion
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*Add [[Level spreaders|flow spreading device]] or re-grade existing device back to level. Rake to regrade damaged portion of the filter bed and replant. If problem persists, replace some [[vegetation|plant]] cover with [[stone]].
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| rowspan="3"|'''[[Swales: Construction|Filter Bed]]'''
|Local or average sediment accumulation ≥ 5 cm in depth.
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*At [[inlets]] remove [[stone]] and use vacuum equipment or rake and shovel to remove sediment. For large areas or BMPs, use of a small excavator may be preferable. Restore grades with planting soil that meets design specifications. Test surface infiltration rate to confirm it is > 15 mm/h. Replace [[stone]] and [[vegetation]] coverage (re-use/transplant where possible). If problem persists, add [[pretreatment]] device(s) or investigate the source(s).
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|Surface ponding remains for > 48 hours or surface infiltration rate is < 15 mm/h.
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*Remove sediment as described above. Core aerate (for grass swales); or remove [[stone]], sediment and [[vegetation|plant]] cover and till 5 cm of yard waste compost into the exposed planting [[Soil groups|soil]] to a depth of 20 cm; or remove and replace the uppermost 15 cm of material with planting soil that meets design specifications. Test [[Infiltration: Testing|surface infiltration rate]] to confirm it has been restored to > 15 mm/h. Replace stone and plants (re-use/transplant where possible).
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|Damage to filter bed or slide slope is present (e.g., [[erosion]] rills, animal burrows, sink holes, ruts)
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*Regrade damaged portion by raking and replant or restore [[stone]] cover. Animal burrows, sink holes and compacted areas should be tilled to 20 cm depth prior to re-grading. If problems persist, consider adding [[Level spreaders|flow spreading device]] to prevent [[erosion]] or barriers to discourage foot or vehicular traffic.
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|'''[[Vegetation]]'''
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Plants not thriving and planting soil is low in organic matter (<5%) or available [[Nutrients|phosphorus]] (<12 mg/kg)
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*Remove [[stone]] and [[vegetation|plant]] cover and uppermost 5 cm of planting soil, spread 5 cm of yard waste compost, incorporate into [[Soil groups|soil]] to 20 cm depth by tilling. Replace stone and plants (re-use/transplant where possible).
|-
|}
==Inspection Time Commitments and Costs==
Estimates are based on a typical partial infiltration bioretention design (i.e., includes a sub-drain); estimates for other designs (i.e., full infiltration and no-infiltration) can be found in the [https://sustainabletechnologies.ca/app/uploads/2016/08/LID-IM-Guide-7.1-Bioretention-and-Dry-Swales.pdf Low Impact Development (LID) Stormwater Management Practice Inspection and Maintenance Guide]<br>
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[[File:Time commit cost swale.PNG|thumb|left|400px|General time commitments and costs for inspection of enhanced swale features (in 2016 $ figures).<ref>TRCA. 2018. Inspection and Maintenance of Stormwater Best Management Practices. Bioretention - Fact Sheet. https://sustainabletechnologies.ca/app/uploads/2018/02/Bioretention-and-Dry-Swales-Fact-Sheet.pdf</ref>]]
[[File:Per-task cost estimate swale.PNG|thumb|400px|Per-task cost estimates for maintenance and rehabilitation of enhanced swale features (in 2016 $ figures).<ref>TRCA. 2018. Inspection and Maintenance of Stormwater Best Management Practices. Bioretention - Fact Sheet. https://sustainabletechnologies.ca/app/uploads/2018/02/Bioretention-and-Dry-Swales-Fact-Sheet.pdf</ref>]]
[[File:Construction life cycle cost swale.PNG|thumb|center|400px|Construction and life cycle cost estimates for enhanced swale features (in 2016 $ figures).<ref>TRCA. 2018. Inspection and Maintenance of Stormwater Best Management Practices. Bioretention - Fact Sheet. https://sustainabletechnologies.ca/app/uploads/2018/02/Bioretention-and-Dry-Swales-Fact-Sheet.pdf</ref>]]<br>
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Estimates of the life cycle costs of inspection and maintenance have been produced using the latest version of the [[Cost analysis resources|LID Life Cycle Costing Tool]] for three design variations (full infiltration, partial infiltration and no infiltration) to assist stormwater infrastructure planners, designers and asset managers with planning and preparing budgets for potential LID features.
Assumptions for the above costs and the following table below are based on the following:
*Capital costs included within the category of construction include those related to site assessment, and conceptual and detailed design related tasks such as borehole analysis and soil testing. All material, delivery, labour, equipment (rental, operation, operator), hauling and disposal costs are accounted for within the construction costs of the facility. Standard union costs were derived from the RSMeans database in 2010 and have been adjusted for 5 year inflation of 8.79% (2010 to June, 2015).
**Costs include overhead and inflation to represent contractor pricing. It was assumed the practice is part of a new development (i.e., not a retrofit), thereby excluding (de)mobilization costs unless a particular piece of equipment would not normally have been present at the site. Additionally, it was assumed that excavated soil associated with construction of the BMP would be reused elsewhere on site. Overhead costs were presumed to consist of construction management (4.5%), design (2.5%), small tools (0.5%), clean up (0.3%) and other (2.2%).
*For maintenance frequencies and requirements and the life span of each practice are based on both literature and practical experience. Life cycle and associated maintenance costs are evaluated over a 50 year timeframe, which is the typical period over which infrastructure decisions are made.
*For enhanced grass swales it is assumed that some rehabilitation (e.g., rehabilitative maintenance) work will be needed on the filter bed surface once the BMP reaches 25 and 50 years of age in order to maintain functional drainage performance at an acceptable level. Included in the rehabilitation costs are (de)mobilization costs, as equipment would not have been present on site. Design costs were not included in the rehabilitation as it was assumed that the original LID practice design would be used to inform this work. The annual average maintenance cost does not include rehabilitation costs and therefore represents an average of routine maintenance tasks, as outlined in the Table under section, [[Inspection and Maintenance: Enhanced Swales#Routine Maintenance - Key Components and I&M Tasks|Routine Maintenance - Key Components and I&M Tasks]] above. All cost value estimates represent the net present value (NPV) as the calculation takes into account average annual interest (2%) and discount (3%) rates over the evaluation time periods.
*For all enhanced swale design variations, the CDA has been defined as a 2,000 m2 impervious pavement area plus the footprint area of a bioretention cell that is 133 m2 in size, as per design recommendations. The impervious area to pervious area ratio (I:P ratio) used to size the BMP footprint is 15:1, which is the maximum ratio recommended in the LID SWM Planning and Design Guide (CVC & TRCA, 2010)<ref>CVC and TRCA. 2010. Low Impact Development Stormwater Management Planning and Design Guide. Version 1.0. https://cvc.ca/wp-content/uploads/2014/04/LID-SWM-Guide-v1.0_2010_1_no-appendices.pdf</ref>. It is assumed that water drains to the cell through curb inlets spaced 6 m apart with stone cover on the filter bed at the inlets to dissipate the energy of the flowing water.
*Estimates of the life cycle costs of Enhanced Swales in Canadian dollars per unit CDA ($/m2) are presented in the table below. The [[Cost analysis resources|LID Life Cycle Costing Tool]] allows users to select what BMP type and design variation applies, and to use the default assumptions to generate planning level cost estimates.
**Users can also input their own values relating to a site or area, design, unit costs, and inspection and maintenance task frequencies to generate customized cost estimates, specific to a certain project, context or stormwater infrastructure program.
**For all BMP design variations and maintenance scenarios, it is assumed that rehabilitation of part or all of the filter bed surface will be necessary once the BMP reaches 25 and 50 years of age to maintain acceptable surface drainage performance (e.g., surface ponding drainage time). Filter bed rehabilitation for enhanced swales is assumed to typically involve the tasks outlined under section, [[Inspection and Maintenance: Enhanced Swales#Routine Maintenance - Key Components and I&M Tasks|Routine Maintenance - Key Components and I&M Tasks]] above.<br>
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[[File:Life cycle costs swales.PNG|thumb|center|900px|Life cycle cost estimates for all variation types of [[enhanced swales]] under minimum and high frequency scenarios (in 2016 $ figures).<ref>TRCA. 2018. Inspection and Maintenance of Stormwater Best Management Practices. Bioretention - Fact Sheet. https://sustainabletechnologies.ca/app/uploads/2018/02/Bioretention-and-Dry-Swales-Fact-Sheet.pdf</ref>]]
'''Notes:'''
<small>
#Estimated life cycle costs represent NPV of associated costs in Canadian dollars per square metre of CDA ($/m2).
#Average annual maintenance cost estimates represent NPV of all costs incurred over the time period and do not include rehabilitation costs.
#Rehabilitation cost estimates represent NPV of all costs related to repair work assumed to occur every 25 years including those associated with inspection and maintenance over a two (2) year establishment period for the plantings.
#Life cycle costs are very similar but slightly lower for BMPs constructed with filter sock or rock check dams, than concrete ones due to differences in material and labor unit costs.
#Rehabilitation costs are estimated to be between 24.4 to 28.1% of the original construction costs for High Frequency and Minimum Recommended maintenance program scenarios, respectively.
# Maintenance and rehabilitation costs over a 25 year time period are estimated to be 1.77 to 2.66 times the original construction cost, for the Minimum Recommended and High Frequency maintenance scenarios respectively, depending on check dam construction material.
# Maintenance and rehabilitation costs over a 50 year time period are estimated to be 3.13 and 4.74 times the original construction cost for the Minimum Recommended and High Frequency maintenance scenarios respectively, depending on check dam construction material.</small>
==Inspection Field Data Sheet==
Feel free to '''download''' (downward facing arrow on the top righthand side) and '''print''' (Pinter emoticon on top right hand side) the following [[enhanced swales|Enhanced Swale]] Inspection Field Data Form developed by TRCA, STEP and its partners for the [https://sustainabletechnologies.ca/app/uploads/2016/08/LID-IM-Guide-2016-1.pdf Low Impact Development Stormwater Management Practice Inspection and Maintenance Guide]<ref>STEP. 2016. Low Impact Development Stormwater Management Practice Inspection and Maintenance Guide. https://sustainabletechnologies.ca/app/uploads/2016/08/LID-IM-Guide-2016-1.pdf</ref>.
The 6 page document prompts users to fill out details previously mentioned above on this page in other sections about various zones associated with [[Enhanced swales|Enhanced swale]] features (i.e. inlets, perimeter of the feature, filter bed, outlets, etc.) and describe why each area is a pass or fail, and if remediate action is required and under what timeframe it would be completed by. Furthermore, the forms prompt the reviewer to determine what type of inspection is being conducted for the feature in question: Construction (C), Routine Operation (RO), Maintenance Verification (MV), or Performance Verification (PV). <br>
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[[File:Newly developed swale.PNG|thumb|330px|Example of a newly developed enhanced swale in a recently developed subdivision.]]
<pdf width="900" height="800">File:Swales inspection sheet.pdf</pdf>
==References==