Difference between revisions of "Inspection and Maintenance: Rainwater Harvesting"

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!<br>'''Verification Inspection'''
!<br>'''Verification Inspection'''
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|''Contributing Drainage Area''
|rowspan="2"|'''Contributing Drainage Area'''
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|CDA Condition
|CDA Condition
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||rowspan="3"|'''[[Inlets|Inlet]]''''
|rowspan="4"|'''[[Inlets|Inlet]]'''
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|Inlet/Flow spreader structural integrity
|Inlet/Flow spreader structural integrity
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|'''Perimeter'''
|rowspan="2"|'''Perimeter'''
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|BMP dimensions
|BMP dimensions
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|rowspan="2"|'''[[Overflow|Overflow outlets]]'''
|rowspan="3"|'''[[Overflow|Overflow outlets]]'''
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|Overflow outlet obstruction
|Overflow outlet obstruction
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|rowspan="2"|'''[[Rainwater harvesting: Sizing and modeling#Cistern dimensions|Cistern]]'''
|rowspan="3"|'''[[Rainwater harvesting: Sizing and modeling#Cistern dimensions|Cistern]]'''
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|Cistern structural integrity
|Cistern structural integrity
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!<br>'''Verification Inspection'''
!<br>'''Verification Inspection'''
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|rowspan="4"|'''Testing Indicators'''
|rowspan="2"|'''Testing Indicators'''
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|Sediment accumulation testing  
|Sediment accumulation testing  

Revision as of 15:48, 12 August 2022

Inspection & Maintenance Guidance of Rainwater harvesting/cisterns best management practices. Rainwater harvesting is the practice of collecting, storing and making use of stormwater from roofs. Relatively clean roof runoff water is collected by eavestroughs or other types of roof drains, filtered to remove coarse debris, and conveyed to a structure where it is stored and drawn upon for purposes not requiring potable water (i.e. landscape irrigation, outdoor washing needs, fire suppression and toilet flushing (TRCA, 2018).[1]

Overview[edit]

Rainwater harvesting/cisterns uses storage structures that can be installed either:

  • Below-ground;
  • Indoors that provide a year-round water source; or,
  • Aboveground tanks and rain barrels that can only be used seasonally and must be taken out of service for the winter.

Rainwater cisterns can range in size from about 750 to 40,000 litres+ and may be constructed from fiberglass, plastic, metal or concrete. Underground cisterns are most often installed to a depth below the maximum frost penetration depth (generally 1.2 m in Southern Ontario) (Armstrong and Csathy, 1963; Ministry of Transportation, 2013)[2][3] to ensure they can be used year-round. A pump is used to deliver the stored water to the hose bibs or fixtures where it is utilized. Water that is in excess of the storage capacity of the cistern overflows to an adjacent drainage system (e.g., other BMP or municipal storm sewer) via an overflow outlet structure and pipe. Cisterns that are drawn upon for indoor water uses (e.g., toilet flushing) will also feature water level sensors and the means of adding municipal water during extended periods of dry weather or winter when stormwater does not meet the demand (i.e., make-up water supply system). They may also include in-line devices to filter stored cistern water prior to delivery at hose bibs or fixtures.

Generalized cross-section view of a rainwater harvesting system showing key components of a commercial configuration of this LID BMP (TRCA, 2018)[1].

Some of the benefits of green roofs include:

  • The ability to reduce the quantity of pollutants and runoff being discharged to municipal storm sewers and receiving waters (i.e., rivers, lakes and wetlands);
  • Underground and indoor cisterns can be used year-round and located below parking lots, roads, plazas, parkland, landscaped areas or within buildings themselves.
  • Can reduce a large commercial building or residential home's water usage significantly if used for non-potable needs


Key components of Underground Infiltration Systems to pay close attention to are the:

Associated Practices[edit]

  • Rain Barrels Rain barrels are an above ground form of rainwater harvesting, typically used in residential settings. The precipitation flows from the roof, to the guttering and down the downspout before being diverted to the rain barrel for storage.
  • Downspout disconnection Downspout disconnections are common in many older urban centers. They require that residents retroactively disconnect their downspouts from the municipal sewer system. This is due to older sewer systems being undersized for the combined flow of sanitary waste and stormwater.
  • Blue roofs are systems that temporarily capture rainwater using the roof as storage and allow it to evaporate and/or to be used for non-potable requirements (i.e. irrigation, toilet flushing, truck washing) and ultimately offset potable water demands.

Inspection and Testing Framework[edit]

Maintneance of the Green roofs filter bed and vegetation composition/condition being performed by staff (TRCA, 2018).[1]
Visual Indicators Framework - Rainwater Harvesting Systems

Component

Indicators

Construction Inspection

Assumption Inspection

Routine Operation Inspection

Verification Inspection
Contributing Drainage Area
CDA Condition x x x x
Inlet
Inlet/Flow spreader structural integrity x x x
Inlet/Flow spreader obstruction x x x x
Pretreatment sediment accumulation x x x
Perimeter
BMP dimensions x x x
Overflow outlets
Overflow outlet obstruction x x x x
Control structure condition x x x x
Cistern
Cistern structural integrity x x x x
Cistern sediment accumulation x x x x



Testing Indicators Framework - Green Roofs

Component

Indicators

Construction Inspection

Assumption Inspection

Routine Operation Inspection

Verification Inspection
Testing Indicators
Sediment accumulation testing x x x x
Cistern pump testing x x (x)
Note: (x) denotes indicators to be used for Performance Verification inspections only (i.e., not for Maintenance Verification inspections)
  1. 1.0 1.1 1.2 TRCA. 2018. Fact Sheet - Inspection and Maintenance of Stormwater Best Management Practices: Rainwater Cisterns. https://sustainabletechnologies.ca/app/uploads/2018/02/Rainwater-Cisterns-Fact-Sheet.pdf
  2. Armstrong, M. D., & Csathy, T. I. 1963. Frost design practice in Canada-and discussion. Ontario Department of Highways. https://onlinepubs.trb.org/Onlinepubs/hrr/1963/33/33-008.pdf
  3. Ministry of Transportation. 2013. Pavement Design and Rehabilitation Manual. Second Edition. IBSN: 978-1-4435-2873-3. Published: March 2013. http://www.bv.transports.gouv.qc.ca/mono/1165561.pdf
  4. Armstrong, M. D., & Csathy, T. I. 1963. Frost design practice in Canada-and discussion. Ontario Department of Highways. https://onlinepubs.trb.org/Onlinepubs/hrr/1963/33/33-008.pdf
  5. Ministry of Transportation. 2013. Pavement Design and Rehabilitation Manual. Second Edition. IBSN: 978-1-4435-2873-3. Published: March 2013. http://www.bv.transports.gouv.qc.ca/mono/1165561.pdf