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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, and Partial Infiltration Design scenarios were assumed to be 20 mm/h and 10 mm/h respectively, and a safety factor of 2.5 was applied to calculate the design infiltration rate.  
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* Native soil infiltration rates for Full Infiltration Design scenarios were 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, 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.
 
* Infiltration chamber system length of 5 metres and composed of 22 chambers in total.
 
* Infiltration chamber system length of 5 metres and composed of 22 chambers in total.

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