Changes

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 rate for Full Infiltration Design scenario was assumed to be 20 mm/h, and a safety factor of 2.5 was applied to calculate the design infiltration rate.  

* Native soil infiltration rate for Full Infiltration Design scenario was assumed to be 20 mm/h, and a safety factor of 2.5 was applied to calculate the design infiltration rate.

* Ditch inlet catch basin structure located at furthest downgradient end, with connection to storm sewer pipe, included as the 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, and removal of weeds twice a year. 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.

* 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, and removal of weeds twice a year. 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.

* Impervious drainage area to pervious swale footprint area of 10:1 (tool default value).

* Impervious drainage area to pervious swale footprint area of 10:1 (tool default value).