* Operation and maintenance (O&M) cost estimates assume annual inspections, removal of trash and debris twice a year, and removal of sediment from pretreatment structures annually. Verification inspections are included every 5 years to confirm adequate maintenance, and every 15 years to confirm adequate drainage performance through in-situ chamber system water level monitoring during natural storm events. | * Operation and maintenance (O&M) cost estimates assume annual inspections, removal of trash and debris twice a year, and removal of sediment from pretreatment structures annually. Verification inspections are included every 5 years to confirm adequate maintenance, and every 15 years to confirm adequate drainage performance through in-situ chamber system water level monitoring during natural storm events. |