As early as the 1930s,
new locks were proposed for the Panama Canal to ease congestion and to allow larger ships to pass. The project was abandoned in 1942. On October 22, 2006, the
Panama Canal Authority (with the support of the Electoral Tribunal) held a
referendum for Panamanian citizens to vote on the
Panama Canal expansion project. The expansion was approved by a
wide margin, with support from about 78% of voters. Construction began in 2007, and after several delays, the new locks opened for commercial traffic on 26 June 2016.
Neopanamax Construction of another set of larger locks led to the creation of the "Neopanamax" or "New Panamax" ship classification, based on the new locks' dimensions of in length, in beam, and in depth. With the new locks, the Panama Canal is able to handle vessels with overall length of , beam (increased by the Canal Authority effective 1 June 2018 to , to accommodate ships with 20 rows of containers) and draft, previously, it could only handle vessels up to about . The Neopanamax standard accommodates ships up to 120,000 DWT.
Impact on world ports United States in New York harbor was increased to accommodate New Panamax ships by building a new, higher roadway inside the arch and then removing the lower roadway. Several ports, including the ports of
New York and New Jersey,
Norfolk, and
Baltimore, all on the East Coast of the United States, have already increased their depth to at least to accommodate New Panamax ships; in 2015 the
Port of Miami achieved the same in a project known as the "
Deep Dredge" and is the closest deepwater port to the Panama Canal in the US. In 2017, the
Port Authority of New York and New Jersey raised the clearance of the
Bayonne Bridge to , at a cost of $1.7 billion, to allow New Panamax ships to reach container port facilities at
Port Newark–Elizabeth Marine Terminal. Previously, only
GCT Bayonne, Global Container, could handle the New Panamax ships. As of April 2012, a controversy between
Savannah, Georgia, and
Charleston, South Carolina, over limited federal funding for dredging/deepening projects—including both state and federal lawsuits filed by environmental groups in both states opposing the techniques planned to be used in dredging the Savannah River—also revolves around attracting the business of carriers whose fleets include New Panamax vessels.
Jacksonville, Florida, is pursuing its "Mile Point" project with the prospect of deepening the St. John's River in anticipation of Post-Panamax traffic;
Mobile, Alabama, has completed the deepening of its harbor to for the same reason; and other ports seem likely to follow suit. The American conservative think tanks
The Heritage Foundation and
Cato Institute have cited the
Foreign Dredge Act of 1906 as a factor in constraining American dredging capacity for expanding ports to accommodate post-Panamax ships.
United Kingdom and Canada Liverpool built a new container terminal,
Liverpool2, where ships berth in the tidal river rather than in the enclosed docks, coinciding with the opening of the widened Panama Canal locks. In
Halifax, Canada, a major expansion of the South End Container Terminal was completed in 2012, extending the pier and increasing the berth depth from .
Mexico The port of
Salina Cruz, in the state of
Oaxaca, Mexico, has been expanded to obtain the capacity to receive Post Panamax ships. This expansion forms part of the
Interoceanic Corridor of the Isthmus of Tehuantepec (CIIT) project which the Mexican government has been executing since 2019. This expansion, which began in January 2022, consists of the creation of a new port with an access depth of , a long
breakwater and a wide mouth. This new port is planned to be inaugurated on February 26, 2024.
Impact on existing ships Due to the expansion, demand for Old Panamax ships has plummeted, resulting in ships being traded at scrap value. Some ships only seven years old have been sold for scrap, and others have been widened. ==Comparison of sizes==