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Multnomah County officials plan to reduce the weight and speed limits on the Morrison Bridge in an effort to keep the bridge in service until the deteriorating lift span is replaced.

The gross weight limit on the bridge will be reduced starting April 18 from 80,000 pounds to 20,000 pounds. Also, the speed limit on the bridge will be reduced from 35 miles per hour to 25. New speed limit signs are scheduled to be installed this week.

The limits will help keep the bridge operational following a botched project three years ago in which the span’s steel grating was replaced with a polymer deck that started falling apart shortly after it was installed, according to county officials.

鈥淭he deterioration of the fiber-reinforced polymer deck on the Morrison Bridge lift span has reached a point where the county needs to reduce vehicle weight and speed limits in order to keep the bridge open,鈥� a county notice to freight industry groups said. 鈥淥ur analysis has led the county engineering staff to conclude that keeping heavy vehicles off the bridge and reducing the impact of the high-speed vehicles is best to extend the life of the deck until it can be replaced.鈥�

County engineers are working with consultant David Evans and Associates to determine the best replacement material for the deck; design is scheduled to start this year. The county is set to receive $4.4 million in damages that will help pay for the project; it sued the contractor, engineer and the manufacturer and distributor of the polymer decking panels that were installed on the Morrison Bridge between 2011 and 2012.

In the meantime, county workers are wrapping up deck repairs that have closed two traffic lanes on the bridge. Both lanes will reopen next month, when the weight limits will take effect.