The plan for the new Walterdale Bridge is shown in this image provided by the city. City of Edmonton

Keeping the old Walterdale Bridge in place after the new bridge is built was deemed redundant and costly by city staff in a new report released Thursday.

Administration have determined it would cost $20 million to convert and maintain the existing bridge for use by cyclists and pedestrians, an idea raised by some Edmonton city councillors earlier this year.

Mayor Stephen Mandel suggested that cost savings achieved by not having to dismantle the old bridge could pay for a fourth lane on the new one.

The report states an initial $8 million would need to be spent to address structural fatigue on the existing structure. Ongoing maintenance would cost city taxpayers approximately $12 million over the next 50 years.

The new $132 million bridge has a deck for cyclists and pedestrians on one side, which would make the old bridge redundant, the report adds.

"Administration believes the funds required to rehabilitate the existing bridge for use may be better used for enhanced pedestrian corridors on the new bridge such as a wider promenade-style trail averaging six metres in width or lookouts," the report says.

Leaving the old bridge up could also detract from the appearance of the new one, the report adds. The report also dismisses the idea of dismantling the old bridge and moving it to the other location for being "labour intensive and costly."

Councillors on the transportation and infrastructure committee will discuss the report next week.

Construction on the new bridge is expected to start in 2013.