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Infiltration Chamber: Life Cycle Costs (view source)
Revision as of 16:30, 20 December 2022
, 2 years agoCreated page with "[[File:Infiltration trench Honda.PNG|thumb|500px|Infiltration trench located at the Honda Campus, Markham, ON. Read about the performance of this practice in the [https://sustainabletechnologies.ca/app/uploads/2015/07/Honda_TechBrief_July2015.pdf technical brief] (Source: STEP, 2015)<ref>Hydrologic Assessment of LID Honda Campus, Markham, ON - TECHNICAL BRIEF. Accessed Dec 19 2022. https://sustainabletechnologies.ca/app/uploads/2015/07/Honda_TechBrief_July2015.pdf</ref>...."
[[File:Infiltration trench Honda.PNG|thumb|500px|Infiltration trench located at the Honda Campus, Markham, ON. Read about the performance of this practice in the [https://sustainabletechnologies.ca/app/uploads/2015/07/Honda_TechBrief_July2015.pdf technical brief] (Source: STEP, 2015)<ref>Hydrologic Assessment of LID Honda Campus, Markham, ON - TECHNICAL BRIEF. Accessed Dec 19 2022. https://sustainabletechnologies.ca/app/uploads/2015/07/Honda_TechBrief_July2015.pdf</ref>.]]
{{TOClimit|2}}
==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].
==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>
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.
* 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)
* Designed with an impervious drainage area to treatment facility area ratio of between 5:1 and 20:1.
** A maximum ratio of 10:1 is recommended from facilities receiving road or parking lot runoff.
* 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]].
* Facilities cannot be located on natural slopes greater than 15%.
* 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===
* Designs include [[pretreatment]] through hydrodynamic separator ([[Oil and Grit Separator]]).
* Operation and maintenance cost estimates assume rehabilitation of the filter media bed surface is required after 25 years of operation.
* 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.<br>
==Construction Costs==
[[File:ConstructionTable InfilTrench Full Infil.PNG|thumb|left|615px|'''Construction Costs Per Unit Drainage Area (CAD$/m<sup>2</sup>) - Full Infiltration Design, 25 mm Treatment''']]
[[File:ConstructionTable InfilTrench Partial Infil.PNG|thumb|center|615px|'''Construction Costs Per Unit Drainage Area (CAD$/m<sup>2</sup>) - Partial Infiltration Design, 25 mm Retention''']]
<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 trenches|Infiltration Trench: Full Infiltration]]
#[[Infiltration trenches|Infiltration Trench: Partial Infiltration]]
As can be seen, regardless of design configuration, Material & Installation expenses represent the largest portion of total construction costs (75 to 76%).
==Life Cycle Costs==
Below are capital and life cycle cost estimates for the two [[Infiltration trenches|infiltration trench]] 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 38% of total life cycle costs over the 25-year evaluation period, and increase to 51% of total life cycle costs over the 50-year period, due to increased levels of litter removal, replacement of filter cloth and disposal of collected sediment (every 4 - 8 years), cleaning out the catchbasin and the [[Oil and Grit Separator|Oil and Grit Separator/Hydrodynamic Separator]] annually, as well as flushing the internal pipes every 10 years.
===25-Year life cycle cost break down===
[[File:25yr LCCT InfilTrench Full Infil.PNG|thumb|left|615px|'''Infiltration Trench: Full Infiltration''']]
[[File:25yr LCCT InfilTrench Partial Infil.PNG|thumb|center|615px|'''Infiltration Trench: Partial Infiltration''']]
<small>'''Note:''' Click on each image to enlarge to view associated life cycle cost estimate.</small><br>
===50-Year life cycle cost break down===
[[File:50yr LCCT InfilTrench Full Infil.PNG|thumb|left|615px|'''Infiltration Trench: Full Infiltration''']]
[[File:50yr LCCT InfilTrench Partial Infil.PNG|thumb|center|615px|'''Infiltration Trench: Partial Infiltration''']]
<small>'''Note:''' Click on each image to enlarge to view associated life cycle cost estimate.</small><br>
==Cost Summary Tables==
Total life cycle cost estimates for the two [[Infiltration trenches|infiltration trench]] configurations vary substantially with the [[Infiltration trenches|Infiltration Trench: Partial Infiltration]] design being highest ($85,288.88), followed closely by the [[Infiltration trenches|Infiltration Trench: Full Infiltration]] design being ($69,805.90).<br>
It is notable that a sensitivity analysis was conducted in 2019 to compare construction cost estimates generated by the tool to actual costs of implemented projects. '''The analysis found that tool estimates were typically within ±14% of actual construction costs'''<ref>Credit Vally Conservation (CVC). 2019. Life-cycle costing tool 2019 update: sensitivity analysis. Credit Valley Conservation, Mississauga, Ontario. https://sustainabletechnologies.ca/app/uploads/2020/04/LCCT-Sensitivity-Analysis_March2020.pdf</ref>
===Full Infiltration===
[[File:North Dakota State U infiltration trench.jpg|800px|thumb|Good use of geotextile, being limited to preventing fines from entering the trench from above. Read more about the performance of this feature in comparison to [[bioretention]]] BMPs in Vaughan, ON. (Source: STEP, 2016<ref>Performance Comparison of Surface and Underground Stormwater Infiltration Practices - TECHNICAL BRIEF. Low Impact Development Series. https://sustainabletechnologies.ca/app/uploads/2016/08/BioVSTrench_TechBrief__July2015.pdf</ref>)]]
[[File:Design Table InfilTrench Full Infil.PNG|700px]]<br>
</br>
===Partial Infiltration===
[[File:Design Table InfilTrench Partial Infil.PNG|700px]]<br>
</br>
==References==
{{TOClimit|2}}
==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].
==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>
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.
* 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)
* Designed with an impervious drainage area to treatment facility area ratio of between 5:1 and 20:1.
** A maximum ratio of 10:1 is recommended from facilities receiving road or parking lot runoff.
* 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]].
* Facilities cannot be located on natural slopes greater than 15%.
* 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===
* Designs include [[pretreatment]] through hydrodynamic separator ([[Oil and Grit Separator]]).
* Operation and maintenance cost estimates assume rehabilitation of the filter media bed surface is required after 25 years of operation.
* 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.<br>
==Construction Costs==
[[File:ConstructionTable InfilTrench Full Infil.PNG|thumb|left|615px|'''Construction Costs Per Unit Drainage Area (CAD$/m<sup>2</sup>) - Full Infiltration Design, 25 mm Treatment''']]
[[File:ConstructionTable InfilTrench Partial Infil.PNG|thumb|center|615px|'''Construction Costs Per Unit Drainage Area (CAD$/m<sup>2</sup>) - Partial Infiltration Design, 25 mm Retention''']]
<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 trenches|Infiltration Trench: Full Infiltration]]
#[[Infiltration trenches|Infiltration Trench: Partial Infiltration]]
As can be seen, regardless of design configuration, Material & Installation expenses represent the largest portion of total construction costs (75 to 76%).
==Life Cycle Costs==
Below are capital and life cycle cost estimates for the two [[Infiltration trenches|infiltration trench]] 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 38% of total life cycle costs over the 25-year evaluation period, and increase to 51% of total life cycle costs over the 50-year period, due to increased levels of litter removal, replacement of filter cloth and disposal of collected sediment (every 4 - 8 years), cleaning out the catchbasin and the [[Oil and Grit Separator|Oil and Grit Separator/Hydrodynamic Separator]] annually, as well as flushing the internal pipes every 10 years.
===25-Year life cycle cost break down===
[[File:25yr LCCT InfilTrench Full Infil.PNG|thumb|left|615px|'''Infiltration Trench: Full Infiltration''']]
[[File:25yr LCCT InfilTrench Partial Infil.PNG|thumb|center|615px|'''Infiltration Trench: Partial Infiltration''']]
<small>'''Note:''' Click on each image to enlarge to view associated life cycle cost estimate.</small><br>
===50-Year life cycle cost break down===
[[File:50yr LCCT InfilTrench Full Infil.PNG|thumb|left|615px|'''Infiltration Trench: Full Infiltration''']]
[[File:50yr LCCT InfilTrench Partial Infil.PNG|thumb|center|615px|'''Infiltration Trench: Partial Infiltration''']]
<small>'''Note:''' Click on each image to enlarge to view associated life cycle cost estimate.</small><br>
==Cost Summary Tables==
Total life cycle cost estimates for the two [[Infiltration trenches|infiltration trench]] configurations vary substantially with the [[Infiltration trenches|Infiltration Trench: Partial Infiltration]] design being highest ($85,288.88), followed closely by the [[Infiltration trenches|Infiltration Trench: Full Infiltration]] design being ($69,805.90).<br>
It is notable that a sensitivity analysis was conducted in 2019 to compare construction cost estimates generated by the tool to actual costs of implemented projects. '''The analysis found that tool estimates were typically within ±14% of actual construction costs'''<ref>Credit Vally Conservation (CVC). 2019. Life-cycle costing tool 2019 update: sensitivity analysis. Credit Valley Conservation, Mississauga, Ontario. https://sustainabletechnologies.ca/app/uploads/2020/04/LCCT-Sensitivity-Analysis_March2020.pdf</ref>
===Full Infiltration===
[[File:North Dakota State U infiltration trench.jpg|800px|thumb|Good use of geotextile, being limited to preventing fines from entering the trench from above. Read more about the performance of this feature in comparison to [[bioretention]]] BMPs in Vaughan, ON. (Source: STEP, 2016<ref>Performance Comparison of Surface and Underground Stormwater Infiltration Practices - TECHNICAL BRIEF. Low Impact Development Series. https://sustainabletechnologies.ca/app/uploads/2016/08/BioVSTrench_TechBrief__July2015.pdf</ref>)]]
[[File:Design Table InfilTrench Full Infil.PNG|700px]]<br>
</br>
===Partial Infiltration===
[[File:Design Table InfilTrench Partial Infil.PNG|700px]]<br>
</br>
==References==