Changes

Tool defaults based on STEP recommendations:

Tool defaults based on STEP recommendations:

* Maximum drainage area to surface area ratio of 20:1

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

* Default depth of 0.75 meters.

* Default filter media depth of 1.0 metres to accommodate trees in planting plan.

* Default mulch depth of 75 millimeters.

* Default mulch depth of 75 millimetres.

* An underdrain (minimum 200 mm perforated pipe) is only needed when native soil infiltration is less than 15 mm/hr or infiltration is precluded.

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

===Design Notes===

===Design Notes===

* Designs include [[pretreatment]] through stone diaphragms at [[Curb cuts|curb inlets]]. Pretreatment through settling forebay and vegetated filter strip not included.

* 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 designs 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. The tool adds 10% contingency and additional overhead.

* 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.

* 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.

* 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.

* Unit costs are based on 2018 pricing; the tool automatically adds inflation. See the Assumptions sheet in the tool for further details.

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

* The cost of retrofitting is ~16% higher than the cost of new construction.

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

** Retrofit costs are included in the 'Costs Summary' section and can be added to the Total Construction Cost for increased accuracy.<br>

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

<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>