1,559
edits
Changes
Jump to navigation
Jump to search
→Construction Costs
Line 13:
Line 13:
Line 46: Line 48:
Design and operation and maintenance program assumptions used to generate cost estimates are based on tool default values and the following STEP recommendations:
Design and operation and maintenance program assumptions used to generate cost estimates are based on tool default values and the following STEP recommendations:
* Maximum impervious drainage area to permeable surface area (I:P area) ratio of 20:1.
* 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)
*Maximum impervious drainage area to permeable surface area (I:P area) ratio of 20:1.
* Length to width ratio of bioretention area is 10:1.
* Length to width ratio of bioretention area is 10:1.
* Default filter media depth of 1.0 metres to accommodate trees in planting plan.
* Default filter media depth of 1.0 metres to accommodate trees in planting plan.
Line 23:
Line 25:
* Operation and maintenance cost estimates assume rehabilitation of the filter media bed surface is required after 25 years of operation.
* 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.
* 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.
** Mobilization and demobilization costs are not included, assuming BMP construction is part of overall development site construction with equipment needed already on-site.
** 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.
** 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.
** 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.
* 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.
* Additional costs associated with retrofit or redevelopment contents is assumed to be 16% higher than the cost for new (greenfield) development 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>
Line 46: Line 48:
#[[Bioretention: Full infiltration]]
#[[Bioretention: Full infiltration]]
#[[Bioretention: Partial infiltration]]
#[[Bioretention: Partial infiltration]]
#[[Stormwater planters| Bioretention: No infiltration]],
#[[Stormwater planters| Bioretention: No infiltration]]
As can be seen, regardless of design configuration, Material & Installation expenses represent the largest portion of total construction costs (75 to 79%).
As can be seen, regardless of design configuration, Material & Installation expenses represent the largest portion of total construction costs (75 to 79%).