Changes

Table below provides guidance on rehabilitation and repair work specific to vegetated/grass filter strips and soil amendments organized according to BMP component.

Table below provides guidance on rehabilitation and repair work specific to vegetated/grass filter strips and soil amendments organized according to BMP component.

   

   

[[File:Levelspread.jpg|thumb|430px|This clever design incorporates a level spreading device after a [[curb cut]] has narrowed the flow path. This kind of treatment train approach would provide an opportunity to provide [[pretreatment]] at the point of concentration. This repair helps to limit the potential of erosion occurring within the feature. Photo credit: [https://www.pca.state.mn.us/featured/when-it-rains-it-flows (MPCA, 204)]<ref>Minnesota Pollution Control Agency. 2014. When it rains, it flows. 6 May 2014. Accessed 156 July 2022. https://www.pca.state.mn.us/featured/when-it-rains-it-flows</ref>]]   

[[File:Levelspread.jpg|thumb|440px|This clever design incorporates a level spreading device after a [[curb cut]] has narrowed the flow path. This kind of treatment train approach would provide an opportunity to provide [[pretreatment]] at the point of concentration. This repair helps to limit the potential of erosion occurring within the feature. Photo credit: [https://www.pca.state.mn.us/featured/when-it-rains-it-flows (MPCA, 204)]<ref>Minnesota Pollution Control Agency. 2014. When it rains, it flows. 6 May 2014. Accessed 156 July 2022. https://www.pca.state.mn.us/featured/when-it-rains-it-flows</ref>]]   

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]] (LCCT) to assist stormwater infrastructure planners, designers and asset managers with planning and preparing budgets. <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]] (LCCT) to assist stormwater infrastructure planners, designers and asset managers with planning and preparing budgets. <br>

For [[vegetated filter strips]] and [[Absorbent landscapes|soil amendment areas]], life cycle cost estimates have been calculated for two level-of-service scenarios: the minimum recommended frequency of inspection and maintenance tasks , and a high frequency scenario to provide an indication of the potential range. The LCCT has assumptions for [[vegetated filter strips]] and [[soil amendment areas]] based on an impervious to pervious area (I:P) ratio of 2.5:1 and inspection and maintenance recommendations for enhanced swales, for relevant components.  

For [[vegetated filter strips]] and [[Absorbent landscapes|soil amendment areas]], life cycle cost estimates have been calculated for two level-of-service scenarios: the minimum recommended frequency of inspection and maintenance tasks , and a high frequency scenario to provide an indication of the potential range. The LCCT has assumptions for [[vegetated filter strips]] and [[Absorbent landscapes|soil amendment areas]] based on an impervious to pervious area (I:P) ratio of 2.5:1 and inspection and maintenance recommendations for enhanced swales, for relevant components.  

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[[File:Veg filter LCCT.JPG|thumb|center|1000px|The life cycle cost estimates for vegetated filter strips and soil amendments are presented in the above table. No design variations scenarios were examined, therefore the Minimum Recommended and High Frequency maintenance scenarios  are the only two scenarios examined for this BMP. It is assumed that no rehabilitation work will be needed to maintain acceptable drainage performance over a 50 year time period (TRCA, 2016)<ref>Toronto and Region Conservation Authority (TRCA). 2016. Low Impact Development Stormwater Management Practice Inspection and Maintenance Guide. Prepared by the Sustainable Technologies Evaluation Program. Vaughan, Ontario. https://sustainabletechnologies.ca/app/uploads/2016/08/LID-IM-Guide-2016-1.pdf</ref>]]<br>

[[File:Veg filter LCCT.JPG|thumb|center|1000px|The life cycle cost estimates for vegetated filter strips and soil amendments are presented in the above table. No design variations scenarios were examined, therefore the Minimum Recommended and High Frequency maintenance scenarios  are the only two scenarios examined for this BMP. It is assumed that no rehabilitation work will be needed to maintain acceptable drainage performance over a 50 year time period (TRCA, 2016)<ref>Toronto and Region Conservation Authority (TRCA). 2016. Low Impact Development Stormwater Management Practice Inspection and Maintenance Guide. Prepared by the Sustainable Technologies Evaluation Program. Vaughan, Ontario. https://sustainabletechnologies.ca/app/uploads/2016/08/LID-IM-Guide-2016-1.pdf</ref>]]<br>

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Assumptions for the above costs are based on the following:

 

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).

*The annual average maintenance cost represents an average of routine maintenance tasks, as outlined above in [[Inspection and Maintenance: Vegetated Filter Strips#Routine Maintenance - Key Components and I&M Tasks|Routine Maintenance - Key Components and I&M Tasks]] All cost value estimates represent the NPV as the calculation takes into account average annual interest (2%) and discount (3%) rates over the evaluation time periods.

*The CDA has been defined as 2,000 m² of impermeable pavement (e.g., road or parking area) which drains by sheet flow to a vegetated filter strip that is approximately 800 m² in area (I:P ratio of 2.5:1), 70 m long, 11.4 m wide and situated along the long edge of the paved area. The side slope is defined as 12.5:1 (8%). Water enters the BMP as sheet flow from a gravel diaphragm flow spreading device along the edge adjacent to the pavement. The BMP surface is planted with grass and does not include check dams, nor any pipes or culverts.

*Estimates of the life cycle costs of vegetated filter strips and soil amendment areas in Canadian dollars per unit CDA ($/m²) are presented above. The [[Cost analysis resources|LCCT) 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. <br>

*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: Bioretention & Dry 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 bioretention and dry 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 bioretention and dry 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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'''Notes:'''

'''Notes:'''

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#Estimated life cycle costs represent NPV of associated costs in Canadian dollars per square metre of CDA ($/m2).

#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.

#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.

#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.

#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.

#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>

#Maintenance and rehabilitation costs over a 25 year time period are estimated to be 3.52 to 5.42 times the original construction cost, for the Minimum Recommended and High Frequency maintenance scenarios respectively.

#Maintenance and rehabilitation costs over a 50 year time period are estimated to be 6.16 and 9.57 times the original construction cost for the Minimum Recommended and High Frequency maintenance scenarios respectively.</small>

 

 

Feel free to '''download''' (downward facing arrow on the top righthand side) and '''print''' (Pinter emoticon on top right hand side) the following [[Vegetated filter strips]] and [[Absorbent landscapes|Soil amendments]] 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 [[[Vegetated Filter strips]] and [[Absorbent landscapes|Soil amendments]]  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>

 

[[File:Filterstrip toronto 2021.JPG|thumb|340px|Example of a plan drawing and appropriate construction specifications for [[Vegetated filter strips]] designed and implemented within Toronto's, municipal bounds (City of Toronto, 2021)<ref>City of Toronto. 2021. Construction Specifications and Drawings for Green Infrastructure. T-850.151 Vegetated Filter Strip – Section. Developed by: Engineering and Construction Services. https://www.toronto.ca/wp-content/uploads/2021/08/9646-ecs-specs-gi-dwgs-T-850.151-Rev0-Sep2021.pdf</ref>]]

 

<pdf width="900" height="800">File:Fitler strips inspection sheet.pdf</pdf>