CHICAGO (CBS) — All but one lane of the Clark Street Bridge will be closed for six months starting Monday, while crews make repairs.

Starting at 9 a.m. Monday, the bridge will be reduced to one lane of traffic and one sidewalk so crews can repair the aging structure’s road decks and sidewalks.

The bridge over the Chicago River was built in 1929, and city officials said it’s possible it has not had repairs like this in 25 years.

“We do testing on the bridges periodically, actually on a schedule, and we look at those reports that come back from the bridge inspections, and we determine when the bridges have actually served their useful life,” Chicago Department of Transportation First Deputy Commissioner Randy Conner said.

Repairs will be performed in quadrants so the bridge can remain partially open to cars and pedestrians, and can be opened and closed for boat lifts as needed.

People who normally use the Clark Street Bridge can use Wells Street or State Street as a detour. Conner said 18,000 drivers use the Clark Street Bridge each day.

The bridge work will not force the CTA to reroute any buses that use Clark Street.

Repairs are expected to be finished by late August. The project will cost about $4 million.

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