| <small>'''Note''': All practice cost estimates are based on a Contributing Drainage Area (CDA) of 2000 m<sup>2</sup>, runoff retention or treatment depth of 25 mm, and a drainage period of 72 hours. For infiltration practices, 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.</small> | | <small>'''Note''': All practice cost estimates are based on a Contributing Drainage Area (CDA) of 2000 m<sup>2</sup>, runoff retention or treatment depth of 25 mm, and a drainage period of 72 hours. For infiltration practices, 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. Operation and maintenance 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.</small> |