Changes

Tool defaults based on STEP recommendations:

Tool defaults based on STEP recommendations:

* Maximum impervious drainage area to permeable surface area (I:P area) ratio of 20:1.

* 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.

* 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.

* Default mulch depth of 75 millimetres.

* Default mulch depth of 75 millimetres.

* An underdrain (200 mm diameter perforated pipe) is included in Partial Infiltration and No Infiltration design configurations.

* An underdrain (200 mm diameter perforated pipe) is included in Partial Infiltration and No Infiltration design configurations only.

===Design Notes===

===Design Notes===

* Designs include [[pretreatment]] through stone diaphragms at [[Curb cuts|curb inlets]] and two inlet structure sumps (Rain Guardian bunkers).

* Designs include [[pretreatment]] through stone diaphragms at [[Curb cuts|curb inlets]] and two inlet structure sumps (Rain Guardian bunkers).

* 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 not included, assuming BMP construction is part of overall development site construction. The tool adds 10% contingency and additional overhead.

* Operation and maintenance cost estimates assume rehabilitation of the filter media bed surface is required after 25 years of operation.

* All cost estimates 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.

* 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.

* Unit costs are based on 2018 RSMeans standard union pricing.

** 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 contents is assumed to be 16% higher than the cost for new (greenfield) development contexts.

* Additional costs associated with retrofit or redevelopment contents is assumed to be 16% higher than the cost for new (greenfield) development contexts.

** Retrofit construction cost estimates are included in the 'Costs Summary' section and can be compared to those for new (greenfield) development.<br>

** Retrofit construction cost estimates are included in the 'Costs Summary' section for comparison.<br>

<small>'''Note''': Bioretention (all 3 design scenarios): Includes pretreatment sump at inlet and assumes that rehabilitation of filter media bed is performed at 25 years.</small>

==Construction Costs==

==Construction Costs==