Pont Colbert

Dieppe, a charming port town in Normandy, France, is home to one of the most fascinating pieces of engineering in Europe – the Pont Colbert. This late 19th-century swing bridge, constructed from puddled and laminated iron, is not only a functional marvel but also a historical gem that continues to captivate both locals and visitors alike. Commissioned in 1889, the Pont Colbert stands as the last major swing bridge in Europe still operating in its original configuration, earning it a spot on the list of historical monuments in 2017 and a classification in September 2020.

The Genesis of Pont Colbert

The idea for a bridge in Dieppe's port to connect the Pollet district to the town center emerged in the 1880s. This was part of a grand initiative to improve national communication routes and ports, spearheaded by Charles de Freycinet, then Minister of Public Works. Dieppe was among the priority projects, and in April 1880, a law was enacted to enhance and expand the port. This development led to the creation of a new 40-meter-wide channel through the fishing district of Pollet, resulting in the demolition of 173 buildings and splitting the neighborhood in two. To reconnect the divided sides, the municipality, led by Mayor Alexandre Anquetin, approved the construction of a swing bridge in 1883.

Construction and Early Years

The construction of the port continued with the excavation of commercial basins in 1887, followed by the assembly of the bridge in just four months in 1888. Designed by architect and engineer Paul Alexandre, the superstructure and deck were built by the Society of Bridges and Iron Works, while the mechanism was crafted by the Société Fives-Lille Cail, known for the lifting bridge on Rue de Crimée in Paris. The Pont Colbert was inaugurated on January 1, 1889, after successful trials. With a span of 70.5 meters, it broke the previous record for swing bridges, held by the Victoria Bridge in Leith, Scotland, since 1874.

Initially, the bridge had no official name and was colloquially known as the Grand Pont, Pont Neuf, or simply Pont qui tourne (the bridge that turns). It wasn't until 1925 that it was officially named Pont Colbert, in honor of Jean-Baptiste Colbert, who had visited Dieppe in 1672 and had previously expanded the port.

Modernization and Wartime Challenges

In 1929, the bridge's steam engines were replaced with electric machines, and in 1938, cantilevered sidewalks were added, and the central strip was removed. During World War II, the bridge was partially destroyed by the German army in 1944, but it remained largely intact. The pivot was damaged, but the mechanism survived. The Allies reinforced the quay, and the lost structure was rebuilt identically after the war. The bridge was back in service by July 1946, becoming the only swing bridge in the port as the nearby Ango Bridge was rebuilt as a bascule bridge.

Further modifications included the removal of the central machinery in 1961, the replacement of the wooden deck with a metal grating in 1980, and the addition of a surveillance system in 1986. In 1989, the bridge's centenary was celebrated with a grand event, including the issuance of a commemorative postal flame. The metal structure underwent renovation in 1999.

The Battle for Preservation

In the late 2000s, plans to demolish the bridge and replace it with a modern structure were proposed by the Dieppe port authority. This sparked an outcry among the local population, leading to the formation of the Committee for the Preservation of Pont Colbert. The committee collected 4,000 signatures in a petition and succeeded in getting the bridge listed as one of Europa Nostra's seven most endangered European heritage sites in 2016. The demolition project was eventually shelved in favor of renovation.

In November 2016, the regional heritage and sites commission recommended listing the bridge as a historical monument, a decision signed by Prefect Nicole Klein in February 2017. In September 2020, the bridge was classified as a historical monument, opening the door for state funding for its renovation. The Dieppe Port Authority plans to dismantle the bridge in 2024 for a complete renovation and automate its operation by 2025.

The Mechanics of Pont Colbert

The Pont Colbert is an impressive iron structure with a deck length of 70.5 meters, 47 meters of which span the channel. Originally weighing 810 tons, the bridge's mass increased with the addition of sidewalks in 1938 and decreased slightly when the wooden deck was replaced with a metal grating in 1980.

The bridge's turning mechanism is hydraulic, utilizing water from the channel. The water is pumped, and the mechanism is driven by two large cylinders that move a heavy chain around the pivot. The operation requires two technicians: one in the control cabin and another managing traffic with flashing lights and barriers. The process takes between 2 to 3 minutes, or as little as 90 seconds if needed.

To prevent the mechanism from freezing in winter, wooden casings filled with horse manure are installed around the pipes and cylinders. If temperatures drop below -6°C, a coke brazier is lit near the pivot, with the heat from the manure protecting the bridge down to -10°C. These labor-intensive operations, involving ten people for two nights a year, are expected to cease with the hydraulic system's insulation in 2025.

The Pont Colbert is not just a bridge; it is a testament to engineering ingenuity and historical resilience. Its preservation efforts highlight the community's dedication to maintaining this unique piece of Dieppe's heritage, ensuring it continues to turn and serve for many more years to come.