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Panama Canal installs last lock gate in critical step toward completion of expansion

  • Construction crews work on the the Panama Canal expansion project new set of locks, while the last rolling gate is installed in Cocoli, near Panama City, Tuesday, April 28, 2015. The Panama Canal Authority supervised the installation of the last of 16 giant lock gates that are a key part of the waterway's multibillion-dollar expansion. The construction of the third set of locks will allow the passage of Post-Panamax vessels or container ships much too big to fit through the Panama Canal's old locks. (AP Photo/Arnulfo Franco)

    Construction crews work on the the Panama Canal expansion project new set of locks, while the last rolling gate is installed in Cocoli, near Panama City, Tuesday, April 28, 2015. The Panama Canal Authority supervised the installation of the last of 16 giant lock gates that are a key part of the waterway's multibillion-dollar expansion. The construction of the third set of locks will allow the passage of Post-Panamax vessels or container ships much too big to fit through the Panama Canal's old locks. (AP Photo/Arnulfo Franco)  (The Associated Press)

  • Cars move inside the Panama Canal expansion project site while the last rolling gate is installed in Cocoli, near Panama City, Tuesday, April 28, 2015. The Panama Canal Authority supervised the installation of the last of 16 giant lock gates that are a key part of the waterway's multibillion-dollar expansion. The construction of the third set of locks will allow the passage of Post-Panamax vessels or container ships much too big to fit through the Panama Canal's old locks. (AP Photo/Arnulfo Franco)

    Cars move inside the Panama Canal expansion project site while the last rolling gate is installed in Cocoli, near Panama City, Tuesday, April 28, 2015. The Panama Canal Authority supervised the installation of the last of 16 giant lock gates that are a key part of the waterway's multibillion-dollar expansion. The construction of the third set of locks will allow the passage of Post-Panamax vessels or container ships much too big to fit through the Panama Canal's old locks. (AP Photo/Arnulfo Franco)  (The Associated Press)

  • Caution tape keeps unauthorized personnel away as employees work on the Panama Canal expansion project new set of locks while the last rolling gate is installed in Cocoli, near Panama City, Tuesday, April 28, 2015. The Panama Canal Authority supervised the installation of the last of 16 giant lock gates that are a key part of the waterway's multibillion-dollar expansion. The construction of the third set of locks will allow the passage of Post-Panamax vessels or container ships much too big to fit through the Panama Canal's old locks. (AP Photo/Arnulfo Franco)

    Caution tape keeps unauthorized personnel away as employees work on the Panama Canal expansion project new set of locks while the last rolling gate is installed in Cocoli, near Panama City, Tuesday, April 28, 2015. The Panama Canal Authority supervised the installation of the last of 16 giant lock gates that are a key part of the waterway's multibillion-dollar expansion. The construction of the third set of locks will allow the passage of Post-Panamax vessels or container ships much too big to fit through the Panama Canal's old locks. (AP Photo/Arnulfo Franco)  (The Associated Press)

The Panama Canal is installing the last of 16 giant lock gates that are a key part of the waterway's multibillion-dollar expansion.

Tuesday's installation of the 4,232-ton gate at the Pacific Ocean entrance to the waterway means the most critical phase of the expansion can start in coming weeks: the flooding of the locks.

Panama in 2006 decided to build a wider canal to accommodate vessels capable of carrying 2.5 times the number of containers held by ships currently using the canal.

The expansion has been beset by a nasty battle over cost overruns with European builders and delays that have pushed back its expected opening by a year to April 2016.