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Inspection and Maintenance: Underground Infiltration Systems (view source)
Revision as of 18:02, 25 July 2022
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==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 [[permeable pavements]], 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 (vehicle or pedestrian) areas or those designed with higher than recommended impermeable drainage area to permeable BMP footprint area ratios ([[Notation|I:P ratios]]). 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"
|+'''Permeable Pavements: Key Components, Descriptions and Routine I&M Requirements'''
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!style="width: 500px"|Comnponent
!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
|-
|'''[[Permeable pavements: Sizing|Contributing Drainage Area (CDA)]]'''
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Area(s) from which runoff directed to the BMP originates; includes the pavement itself and any adjacent impermeable pavement or roofs that drain to it.
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*Remove trash, debris and sediment from pavements (biannually to quarterly) and eavestroughs (annually);
*Replant or seed bare soil areas as needed.
|[[File:CDA Pass p.p.JPG|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 Fail p.p.JPG|280px|thumb|center|Size of the CDA has changed from design assumptions (i.e. large asphalt area drains to a small portion of the permeable pavement). Evidence of surface ponding is visible.]]
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|'''[[Pretreatment]]'''
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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]].
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*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 p.p.JPG|280px|thumb|center|Although permeable pavers are generally considered [[pretreatment]] for other BMPs in a [[Low impact development treatment train tool|treatment train]] system, using eavestrough screens can act as pretreatment as they don't add to sediment build up and accumulation on the paver surface. (Photo Source: Guertin, 2010)<ref>Guertin, M. 2010. Simple Screen Gutter Guards Better Than Pro-Installed Systems (and way cheaper). Fine Homebuilding - The Daily Fix. Accessed July 17 2022. https://www.finehomebuilding.com/2010/08/17/simple-screen-gutter-guards-better-than-pro-installed-systems-and-way-cheaper</ref>]]
|[[File:Pretreat Fail p.p.JPG|300px|thumb|center|Build up of leads, sediment and leaf detritus in an eavestrough downspout disconnection leading to a permeable pavement surface. If not cleaned regularly this can lead to clogged pores between the pavers reducing the infiltration rate where the downspout deposits water onto the feature. (Photo Source: My Gutter Pro, 2021)<ref>My Gutter Pro. 2021. Clogged Downspout : Causes and Solutions. 10 April 2021. Accessed July 19 2022. https://mygutterpro.com/downspout-clog/</ref>]]
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|'''[[Inlets]]'''
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Structures that deliver water to the BMP (e.g., impermeable pavement edges, [[pipes]] from roof downspouts or catchbasins).
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*Keep free of obstructions;
*Remove trash, debris and sediment biannually to quarterly;
*Make note of sediment depth or volume during each cleaning or annually to estimate accumulation rate and optimize frequency of maintenance
|[[File:Inlet Pass p.p.JPG|285px|thumb|center|Impermeable pavement edges along the edge of the pervious concrete and impermeable asphalt graded so excess sheet flow is infiltrated down through the pores of the infiltration BMP. (Photo Source: Fairfax County, 2014)<ref>Fairfax County. 2014. Protecting our Environment, one Stormwater Practice at a Time - Permeable Pavements. April 2014. Accessed: July 20 2022. https://www.fairfaxcounty.gov/publicworks/sites/publicworks/files/assets/documents/pdf/factsheets/permeable-pavement.pdf</ref>]]
|[[File:Curb inlet grade.jpg|300px|thumb|center|Accumulated sediment, poor grading and vegetation is preventing stormwater from entering the [[swale]]. Sediment on the curb cut surface behind of the inlet indicates ponding is also occurring and is depositing water towards the permeable paver surface.]]
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|'''[[Permeable pavements: Specifications|Pavement Surface]]'''
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The surface of the pavement, including pavers/pavement, joints and edge restraints (e.g., curbs, edging); should not allow water to pond on the surface so any observation or evidence of surface ponding (e.g., sediment caking on the pavement) indicates a drainage problem.
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*Check for sediment, surface ponding, deformation, sink holes, damage and loss of joint fill;
*Remove trash regularly (biannually-quarterly);
*Grid systems with soil and grass fill are maintained like lawns;
*Sweep and vacuum interlocking and rigid pavements regularly (annually-biannually) with regenerative air/pure vacuum sweeper;
*Plow snow as needed and spread deicers sparingly during winter;
*Repair ruts or local sinking of 15 mm or greater over a 3 metre length, adjacent pavers or cracks in pervious concrete or porous asphalt are vertically offset by 5 mm or greater and paver joint fill is missing or below 15 mm from the paver surface.
|[[File:Pavesurface Pass p.p.JPG|350px|thumb|center|No damage, displacement or sinking of the permeable surface is visible and there are no weeds growing between paver joints.]]
|[[File:Pavesurface Fail p.p.JPG|280px|thumb|center|The pavement surface has sunk in local areas, creating a trip hazard and the potential for further damage from snow plowing and parked vehicles nearby.]]
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|'''[[Vegetation]]'''
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Applies to grid paver systems only; a mixture of deep rooting perennial grasses or low growing ground covers, tolerant to both wet and dry conditions and salt (if receiving impermeable pavement runoff); roots uptake water and return it to the atmosphere, provide habitat for soil organisms that break down pollutants trapped in the soil and help maintain soil structure and permeability.
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*Grid systems with soil and grass fill are maintained like lawns;
*In the first 2 months water 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/reseed dead plantings annually to achieve 80% cover by the third growing season;
*Do not apply chemical fertilizers.
|[[File:Veg Pass p.p.JPG|315px|thumb|center|The vegetation cover on the permeable pavement is turf grass as specified in the final design and contains very few weeds. (Photo source: WEF).]]
|[[File:Veg Fail p.p.JPG|290px|thumb|center|The turf grass cover on the permeable walkway is not thriving in some areas and needs cutting in others. It is also impairing the aesthetic value of the BMP.]]
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|'''[[Overflow|Overflow Outlet]]'''
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Structures (e.g., catchbasin, curb-cut, [[swale]]) that convey flow that exceeds the storage capacity of the BMP to another drainage system (e.g., municipal storm sewer or other BMP).
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*Keep free of obstructions;
*Remove trash, debris and sediment biannually to quarterly.
|[[File:Overflow Pass p.p.JPG|320px|thumb|center|The overflow outlet is free of damage and obstruction and functions as designed to safely convey excess water from the BMP.]]
|[[File:Overflow Fail p.p.JPG|280px|thumb|center|The overflow outlet is obstructed with sediment which impairs its function to convey excess water from the BMP.]]
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|'''[[Underdrain|Sub-drain]]'''
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Optional component; [[Pipes|perforated pipe(s)]] surrounded by [[gravel]] and may be wrapped in [[Geotextile|geotextile filter fabric]]; installed in the base or sub-base gravel layer to collect and convey treated water to an adjacent drainage system or other BMP; may also include a flow restrictor.
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*Keep pipe and flow restrictor free of obstructions by flushing annually;
*Inspect flow restrictor regularly (e.g., biannually to quarterly).
|[[File:Underdrain Pass p.p.JPG|310px|thumb|center|The solid section of the sub-drain pipe is not obstructed by sediment, debris or roots and shows no signs of damage.]]
|[[File:Underdrain Fail p.p.JPG|300px|thumb|center|A section of the sub-drain pipe has been crushed which substantially reduces its conveyance capacity]]
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|'''[[Monitoring well]]'''
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[[Wells|Perforated standpipe]] that extends from the bottom of the excavation to just below the pavement surface and contains perforations or slots to allow [[Digital technologies|measurement of subsurface water level]]; used to track drainage performance over the operating life cycle of the BMP.
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*[[Wells|Standpipes]] should be securely capped on both ends and protected from damage by vehicular traffic by a casing.
|[[File:Monitor Pass p.p.JPG|340px|thumb|center|The well is undamaged and accessible and the cap is in place and secured to prevent unauthorized access]]
|[[File:Monitor Fail p.p.JPG|300px|thumb|center|The well cap is missing and the casing is clogged by sediment, preventing access for monitoring and allowing sediment to flow into the sub-drain system.]]
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|'''[[Flow through riser|Control Structure]]'''
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Manhole or catchbasin to which the subdrain outlets that provides access to the [[underdrain]] and flow restrictor. Inspect for accessibility, damage and sediment.
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*Remove trash, debris and sediment regularly (biannually/quarterly)..
|[[File:Control Struct Pass p.p.JPG|340px|thumb|center|TThere is some sediment accumulated in the manhole but it is not impairing the flow of stormwater into or out of the BMP. (Photo source: SWC Canada)]]
|[[File:Control Struct Fail p.p.JPG|300px|thumb|center|The manhole sump is full of sediment and debris and it is beginning to impair flow of stormwater into a perforated pipe of the exfiltration storm sewer system.]]
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