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 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.  

* 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.  

* 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)

* 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)

* Designed with a trapezoidal or triangular cross section.

* Designed with a trapezoidal or triangular cross section.