Difference between revisions of "Infiltration Chamber: Life Cycle Costs"

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==Overview==
 
==Overview==
[[Infiltration chambers]] include a range of proprietary manufactured, modular structures installed underground (embedded in clean, crushed angular [[stone]]) to create large void spaces that temporarily store and infiltrate runoff into the underlying native soil. Typically installed under parking or landscaped areas, they can be used in various configurations. They are well suited to sites where available land area is limited, or where it is desirable for the facility to have a minimal surface footprint. They can be designed with enough load bearing capacity to support the weight of structures above them, meaning that they can be installed below parking lots, sports fields, etc. STEP has prepared life cycle costs estimates for each design configuration, based on a 2,000 m<sup>2</sup> road drainage area, runoff control target of 25 mm depth and 72 hour drainage period, for comparison which can be viewed below. To generate your own life cycle cost estimates customized to the development context, design criteria, and constraints applicable to your site, access the updated [https://sustainabletechnologies.ca/lid-lcct/ LID Life Cycle Costing Tool (LCCT) here].
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[[Infiltration chambers]] include a range of proprietary manufactured, modular structures installed underground (embedded in clean, crushed angular [[stone]]) to create large void spaces that temporarily store and infiltrate runoff into the underlying native soil. Typically installed under parking or landscaped areas, they can be used in various configurations. They are well suited to sites where available land area is limited, or where it is desirable for the facility to have a minimal surface footprint. They can be designed with enough load bearing capacity to support the weight of structures above them, meaning that they can be installed below parking lots, sports fields, etc.
 +
STEP has prepared a life cycle cost estimate for infiltration chamber systems located on highly permeable native soil (Full Infiltration design) for comparison. Cost estimates are based on a 2,000 m<sup>2</sup> asphalt drainage area, runoff control target of 25 mm depth and 82 hour drainage period, which can be viewed below. To generate your own life cycle cost estimates customized to the development context, design criteria, and constraints applicable to your site, access the updated [https://sustainabletechnologies.ca/lid-lcct/ LID Life Cycle Costing Tool (LCCT) here].
  
 
==Design Assumptions==
 
==Design Assumptions==
Infiltration chambers are an ideal technology for installing below any type of surface or landscape and for receiving and infiltrating large volumes of water. Components include: washed 25 or 50 mm diameter crushed angular stone to create a suitable storage reservoir, proprietary chambers, vaults, crates or perforated pipes that provide large water storage volume per unit area, [[geotextile]], [[underdrain|perforated pipe or underdrains]] and access structures. <br>
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Infiltration chambers are an ideal technology for installing below any type of surface or landscape suitable for receiving and infiltrating large volumes of stormwater. Components typically include proprietary chamber system parts that provide large water storage volume per unit area, [[Reservoir aggregate| clear stone aggregate]] to construct base and embed chambers, [[Geotextile| geotextile]], [[Pretreatment| pretreatment devices]], and structures to access inlets, outlets, pretreatment devices and the chambers themselves for operation and maintenance. Optional components include a flow restrictor to control the release rate of the facility, and surface drains to safely convey flows in excess of the storage capacity of the design.<br>
  
Design and operation and maintenance program assumptions used to generate cost estimates are based on tool default values and the following STEP recommendations:
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Design and operation and maintenance program assumptions used to generate cost estimates are based on tool default values and the following STEP recommendations:
* Native soil infiltration rates for Full, Partial and No Infiltration Design scenarios were assumed to be 20 mm/h, 10 mm/h and 2 mm/h, respectively, and a safety factor of 2.5 was applied to calculate the design infiltration rate.  
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* Native soil infiltration rates for Full Infiltration Design scenarios were assumed to be 20 mm/h, and a safety factor of 2.5 was applied to calculate the design infiltration rate.  
* Operation and maintenance (O&M) cost estimates assume annual inspections, removal of trash and debris twice a year, removal of sediment from pretreatment structures annually, and removal of weeds twice a year (where applicable). Verification inspections are included every 5 years to confirm adequate maintenance, and every 15 years to confirm adequate drainage performance through in-situ surface infiltration rate testing (where applicable)
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* Operation and maintenance (O&M) cost estimates assume annual inspections, removal of trash and debris twice a year, and removal of sediment from pretreatment structures annually. Verification inspections are included every 5 years to confirm adequate maintenance, and every 15 years to confirm adequate drainage performance through in-situ chamber system water level monitoring during natural storm events.
* Designed with an impervious drainage area to treatment facility area ratio of between 5:1 and 20:1.
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* Infiltration chamber system length of 5 metres and composed of 22 chambers in total.
** A maximum ratio of 10:1 is recommended from facilities receiving road or parking lot runoff.
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* Infiltration chamber height of 0.762 metres.
* Facilities receiving road or parking lot runoff should not be located within the two year time-of-travel of [[Source Water Protection|wellhead protection areas]].
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* 50 mm dia. clear stone aggregate bedding depth (below and above chamber system) of 152 millimetres.
* Facilities cannot be located on natural slopes greater than 15%.
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* Two (2) maintenance holes providing access to infiltration chamber system inlet and outlet structures.
* The bottom of the facility should be vertically separated by one metre from the seasonally high water table or top of bedrock elevation.
 
* Facilities should be setback a minimum of four metres from building foundations.
 
* Pretreatment device options include leaf screens for roof runoff, and [[vegetated filter strips]], [[enhanced swales|grass swales]] or [[oil and grit separators]] for road runoff.
 
* The tool automatically includes an OGS for facilities receiving road runoff.
 
* The [[inlet]] and [[Overflow|overflow outlet]] to the facility should be installed below the maximum [[Winter Management|frost penetration depth]] to prevent freezing.
 
* The overflow outlet can be the pipe inlet that backs up when capacity's reached (discharging to pervious area), or it can be a pipe connected to a storm sewer.
 
* Outlet pipes must have capacity equal to or greater than the inlet.
 
* Capped and vertical non-perforated pipes connected to the inlet and outlet pipes are recommended for inspecting and flushing as part of routine maintenance.
 
* Manholes and inspection ports should be installed in infiltration chambers to provide access for monitoring and maintenance activities (Tool defaults).
 
* Compaction, erosion and sediment control are main concerns during construction.  Facilities are vulnerable to failure during the construction phase. Construction sediment can clog the excavation if construction instructions incorrectly followed.
 
  
 
===Notes===
 
===Notes===
* Designs include [[pretreatment]] through hydrodynamic separator ([[Oil and Grit Separator]] and A "Sediment Trap" or Isolated chamber row).
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* Design include [[pretreatment]] through hydrodynamic separator ([[Oil and Grit Separator| i.e., oil and grit separator]]) and isolated chamber row.
 
* The tool calculates costs for new (greenfield) development contexts and includes costs for contractor overhead and profit, material, delivery, labour, equipment (rental, operating and operator costs), hauling and disposal.  
 
* The tool calculates costs for new (greenfield) development contexts and includes costs for contractor overhead and profit, material, delivery, labour, equipment (rental, operating and operator costs), hauling and disposal.  
 
** Land value and equipment mobilization and demobilization costs are not included, assuming BMP construction is part of overall development site construction.
 
** Land value and equipment mobilization and demobilization costs are not included, assuming BMP construction is part of overall development site construction.
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* All cost estimates are in Canadian dollars and represent the net present value (NPV) as the tool takes into account average annual interest and discount rates over the 25 and 50 year operating life cycle periods.
 
* All cost estimates are in Canadian dollars and represent the net present value (NPV) as the tool takes into account average annual interest and discount rates over the 25 and 50 year operating life cycle periods.
 
* Unit costs are based on 2018 RSMeans standard union pricing.
 
* Unit costs are based on 2018 RSMeans standard union pricing.
* Cost for piping from roof to system, parking lot to system and overflow from system are not included in this costing. 
 
* Costs of the control manhole and overflow, and pre-treatment via an OGS (when the facility takes road runoff) are included.
 
 
* Additional costs associated with retrofit or redevelopment contexts is assumed to be 16% of the cost estimate for new (greenfield) construction contexts.
 
* Additional costs associated with retrofit or redevelopment contexts is assumed to be 16% of the cost estimate for new (greenfield) construction contexts.
 
** Retrofit construction cost estimates are included in the 'Costs Summary' section for comparison.<br>
 
** Retrofit construction cost estimates are included in the 'Costs Summary' section for comparison.<br>
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==Construction Costs==
 
==Construction Costs==
  
[[File:ConstructionTable InfilChamb Full Infil.PNG|thumb|left|610px|'''Construction Costs Per Unit Drainage Area (CAD$/m<sup>2</sup>) - Full Infiltration Design, 25 mm Treatment''']]
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[[File:ConstructionTable InfilChamb Full Infil 2023.PNG|thumb|center|900px|'''Construction Costs Per Unit Drainage Area (CAD$/m<sup>2</sup>) - Full Infiltration Design, 25 mm Retention''']]<br>
  
[[File:ConstructionTable InfilChamb Partial Infil.PNG|thumb|center|615px|'''Construction Costs Per Unit Drainage Area (CAD$/m<sup>2</sup>) - Partial Infiltration Design, 25 mm Retention''']]
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<small>'''Note:''' Click on image to enlarge to view associated construction cost estimates.</small><br>
 
 
 
 
<small>'''Note:''' Please click on each image to enlarge to view associated construction cost estimates.</small><br>
 
 
 
 
 
Above you can find a cost breakdown of a 1000m<sup>2</sup> in two different configurations:<br>
 
#[[Infiltration chambers|Infiltration Chamber: Full Infiltration]]
 
#[[Infiltration chambers|Infiltration Chamber: Partial Infiltration]]
 
  
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Above you can find a breakdown of construction costs by expense type.<br>
 +
<br>
 
As can be seen, regardless of design configuration, Material & Installation expenses represent the largest portion of total construction costs (75%).
 
As can be seen, regardless of design configuration, Material & Installation expenses represent the largest portion of total construction costs (75%).
  
 
==Life Cycle Costs==
 
==Life Cycle Costs==
Below are capital and life cycle cost estimates for the two [[Infiltration chambers|infiltration chamber]] configurations over 25- and 50-year time periods. The estimates of maintenance and rehabilitation (life cycle) costs represent net present values. Operation and maintenance costs are predicted to represent 36% of total life cycle costs over the 25-year evaluation period, and increase to 48% of total life cycle costs over the 50-year period, due to increased levels of litter removal, clean out and disposal of collected sediment from the Isolated chamber row (every 4 - 8 years), cleaning out the catchbasin and the [[Oil and Grit Separator|Oil and Grit Separator/Hydrodynamic Separator]] annually.  
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Below are capital and life cycle cost estimates for the [[Infiltration chambers|infiltration chamber]] design scenario over 25- and 50-year time periods. The estimate of maintenance and rehabilitation (life cycle) cost represents net present values. Operation and maintenance costs are predicted to represent 37% of total life cycle costs over the 25-year evaluation period, and increase to 49% of total life cycle costs over the 50-year period, due to cost associated with removal of sediment from the isolated chamber row pretreatment devices every 8 years.
 
 
  
 
===25-Year life cycle cost break down===
 
===25-Year life cycle cost break down===
  
[[File:25yr LCCT InfilChamb Full Infil.PNG|thumb|left|615px|'''Infiltration Trench: Full Infiltration''']]
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[[File:25yr LCCT InfilChamb Full Infil 2023.PNG|thumb|center|900px|'''Infiltration Trench: Full Infiltration''']]<br>
  
[[File:25yr LCCT InfilChamb Partial Infil.PNG|thumb|center|615px|'''Infiltration Trench: Partial Infiltration''']]
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<small>'''Note:''' Click on image to enlarge to view associated life cycle cost estimate.</small><br>
 
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</br>
 
 
<small>'''Note:''' Click on each image to enlarge to view associated life cycle cost estimate.</small><br>
 
  
 
===50-Year life cycle cost break down===
 
===50-Year life cycle cost break down===
  
[[File:50yr LCCT InfilChamb Full Infil.PNG|thumb|left|615px|'''Infiltration Chamber: Full Infiltration''']]
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[[File:50yr LCCT InfilChamb Full Infil 2023.PNG|thumb|center|900px|'''Infiltration Chamber: Full Infiltration''']]<br>
 
 
[[File:50yr LCCT InfilChamb Partial Infil.PNG|thumb|center|615px|'''Infiltration Chamber: Partial Infiltration''']]
 
 
 
  
<small>'''Note:''' Click on each image to enlarge to view associated life cycle cost estimate.</small><br>
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<small>'''Note:''' Click on image to enlarge to view associated life cycle cost estimate.</small><br>
  
 
==Cost Summary Tables==
 
==Cost Summary Tables==
Total life cycle cost estimates for the two [[Infiltration chambers|infiltration chamber]] configurations are the exact same with the total being ($60,831.76).<br>
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Total life cycle cost estimate over the 50 year evaluation period for [[Infiltration chambers|infiltration chamber system]] on highly permeable native soil design scenario is $123,670.89.<br>
  
 
===Full Infiltration===
 
===Full Infiltration===
[[File:East Gwillimbury.png|800px|thumb|Example of "crate style" [[Infiltration chambers]] being installed in East Gwillimbury. Photo credit: [https://www.makeway.ca/products/stormwater-management-systems/ Make-Way Environmental Technologies Inc.]]
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[[File:East Gwillimbury.png|400px|thumb|Example of "crate style" [[Infiltration chambers]] being installed in East Gwillimbury. Photo credit: [https://www.makeway.ca/products/stormwater-management-systems/ Make-Way Environmental Technologies Inc.]]
  
[[File:Design Table InfilChamb Full Infil.PNG|700px]]<br>
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[[File:Design Table InfilChamb Full Infil 2023.PNG|830px]]<br>
 
</br>
 
</br>
===Partial Infiltration===
 
[[File:Design Table InfilChamb Partial Infil.PNG|700px]]<br>
 
 
</br>
 
</br>
  
 
==References==
 
==References==

Latest revision as of 16:12, 6 March 2023

Read about the performance of infiltration chamber systems in the STEP technical brief (STEP 2015)[1] and full report (Young et al. 2013)[2]).


Overview[edit]

Infiltration chambers include a range of proprietary manufactured, modular structures installed underground (embedded in clean, crushed angular stone) to create large void spaces that temporarily store and infiltrate runoff into the underlying native soil. Typically installed under parking or landscaped areas, they can be used in various configurations. They are well suited to sites where available land area is limited, or where it is desirable for the facility to have a minimal surface footprint. They can be designed with enough load bearing capacity to support the weight of structures above them, meaning that they can be installed below parking lots, sports fields, etc. STEP has prepared a life cycle cost estimate for infiltration chamber systems located on highly permeable native soil (Full Infiltration design) for comparison. Cost estimates are based on a 2,000 m2 asphalt drainage area, runoff control target of 25 mm depth and 82 hour drainage period, which can be viewed below. To generate your own life cycle cost estimates customized to the development context, design criteria, and constraints applicable to your site, access the updated LID Life Cycle Costing Tool (LCCT) here.

Design Assumptions[edit]

Infiltration chambers are an ideal technology for installing below any type of surface or landscape suitable for receiving and infiltrating large volumes of stormwater. Components typically include proprietary chamber system parts that provide large water storage volume per unit area, clear stone aggregate to construct base and embed chambers, geotextile, pretreatment devices, and structures to access inlets, outlets, pretreatment devices and the chambers themselves for operation and maintenance. Optional components include a flow restrictor to control the release rate of the facility, and surface drains to safely convey flows in excess of the storage capacity of the design.

Design and operation and maintenance program assumptions used to generate cost estimates are based on tool default values and the following STEP recommendations:

  • Native soil infiltration rates for Full Infiltration Design scenarios were assumed to be 20 mm/h, and a safety factor of 2.5 was applied to calculate the design infiltration rate.
  • Operation and maintenance (O&M) cost estimates assume annual inspections, removal of trash and debris twice a year, and removal of sediment from pretreatment structures annually. Verification inspections are included every 5 years to confirm adequate maintenance, and every 15 years to confirm adequate drainage performance through in-situ chamber system water level monitoring during natural storm events.
  • Infiltration chamber system length of 5 metres and composed of 22 chambers in total.
  • Infiltration chamber height of 0.762 metres.
  • 50 mm dia. clear stone aggregate bedding depth (below and above chamber system) of 152 millimetres.
  • Two (2) maintenance holes providing access to infiltration chamber system inlet and outlet structures.

Notes[edit]

  • Design include pretreatment through hydrodynamic separator ( i.e., oil and grit separator) and isolated chamber row.
  • The tool calculates costs for new (greenfield) development contexts and includes costs for contractor overhead and profit, material, delivery, labour, equipment (rental, operating and operator costs), hauling and disposal.
    • Land value and equipment mobilization and demobilization costs are not included, assuming BMP construction is part of overall development site construction.
    • Design and Engineering cost estimates are not calculated by the tool and must be supplied by the user.
    • The tool adds 10% contingency and additional overhead as default.
  • All cost estimates are in Canadian dollars and represent the net present value (NPV) as the tool takes into account average annual interest and discount rates over the 25 and 50 year operating life cycle periods.
  • Unit costs are based on 2018 RSMeans standard union pricing.
  • Additional costs associated with retrofit or redevelopment contexts is assumed to be 16% of the cost estimate for new (greenfield) construction contexts.
    • Retrofit construction cost estimates are included in the 'Costs Summary' section for comparison.

Construction Costs[edit]

Construction Costs Per Unit Drainage Area (CAD$/m2) - Full Infiltration Design, 25 mm Retention


Note: Click on image to enlarge to view associated construction cost estimates.

Above you can find a breakdown of construction costs by expense type.

As can be seen, regardless of design configuration, Material & Installation expenses represent the largest portion of total construction costs (75%).

Life Cycle Costs[edit]

Below are capital and life cycle cost estimates for the infiltration chamber design scenario over 25- and 50-year time periods. The estimate of maintenance and rehabilitation (life cycle) cost represents net present values. Operation and maintenance costs are predicted to represent 37% of total life cycle costs over the 25-year evaluation period, and increase to 49% of total life cycle costs over the 50-year period, due to cost associated with removal of sediment from the isolated chamber row pretreatment devices every 8 years.

25-Year life cycle cost break down[edit]

Infiltration Trench: Full Infiltration


Note: Click on image to enlarge to view associated life cycle cost estimate.

50-Year life cycle cost break down[edit]

Infiltration Chamber: Full Infiltration


Note: Click on image to enlarge to view associated life cycle cost estimate.

Cost Summary Tables[edit]

Total life cycle cost estimate over the 50 year evaluation period for infiltration chamber system on highly permeable native soil design scenario is $123,670.89.

Full Infiltration[edit]

Example of "crate style" Infiltration chambers being installed in East Gwillimbury. Photo credit: [https://www.makeway.ca/products/stormwater-management-systems/ Make-Way Environmental Technologies Inc.

Design Table InfilChamb Full Infil 2023.PNG


References[edit]

  1. Sustainable Technologies Evaluation Program (STEP) 2015. Evaluation of Underground Stormwater Infiltration Systems. Technical Brief. Toronto and Region Conservation Authority. Toronto, Ontario. https://sustainabletechnologies.ca/app/uploads/2015/04/UndergroundInfiltrationSystems_TechBrief_April2015.pdf
  2. Young, D. Van Seters, T., Graham, C. 2013. Evaluation of Underground Stormwater Infiltration Systems. Toronto and Region Conservation Authority. Toronto, Ontario. https://sustainabletechnologies.ca/app/uploads/2013/03/Infiltration-Chambers-and-Trenches_2013-Final.pdf