PAULSBORO, N.J. (CBSNewYork/AP) — A movable bridge in Paulsboro, N.J., where a freight train derailed last year will be replaced.

Conrail officials told the Courier-Post of Cherry Hill that a new swing bridge over Mantua Creek in Paulsboro should be operational by September 2014. The current span will remain in use until then, but the waterway below it will remain inaccessible to boaters until construction is complete.

The derailment happened in December, as a train with two locomotives, 82 freight cars and a caboose made its way from Camden to the industrial town of Paulsboro, just across the Delaware River from Philadelphia International Airport.

Seven of the train cars detailed. One tanker containing 25,000 gallons of vinyl chloride was sliced open in the accident and some of the gas spewed into the air, while the rest turned into a solid and settled into the bottom of the tanker.

More than 70 people were hospitalized for minor breathing problems. Officials initially thought the air quality was safe, but then at 6 p.m. Friday, officials ordered an evacuation of a 12-block radius surrounding the accident site because of an increase in the level of the vinyl chloride gas.

U.S. Coast Guard officials said about 500 residents were told to pack bags good for three days, and were taken to area hotels. More than 100 people remained out of their homes Saturday.

The bridge usually supported at least three major trains each day serving refineries and other customers in an industrial area along the Delaware River. It was also rebuilt after it buckled in 2009.

The Federal Railroad Administration last inspected the bridge in January 2010 and found no defects. Railroads are required by law to conduct their own inspections. The FRA does not know when Conrail last did one.

Nine cars on a coal train derailed at the moveable bridge on Aug. 23, 2009, in an accident that was attributed to a bridge misalignment.

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