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Line 10: − + − + − * Maximum contributing flow path length across adjacent impervious surfaces should not exceed 25 metres. + − * Impervious surfaces draining to a filter strip should not have slopes greater than 3%.+ − * The flow path length across the vegetated filter strip should exceed the maximum flow path length across the impervious surface draining to it. − * Have a flow path length of at least 5 metres. +
Vegetated Filter Strip: Life Cycle Costs (view source)
Revision as of 20:07, 10 January 2023
, 1 year ago→Design Assumptions
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:
* 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.
* Filter strip length of 5 metres.
* 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 acceptable impervious drainage area to pervious footprint area ratio of 4:1.
* Swale (0.3 m depth) and ditch inlet catch basin connected to storm sewer as outlet.
* Operation and maintenance (O&M) cost estimates assume annual inspections, removal of trash and debris twice a year, removal of sediment from outlet catch basin annually, mowing five times a year, removal of weeds twice a year, and core aeration of filter strip surface every 5 years. Verification inspections are included every 5 years to confirm adequate maintenance.
===Notes===
===Notes===
* Design includes [[pretreatment]] through stone diaphragms at [[Curb cuts|curb inlets]].
* 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.