Restoration of the Auxerre cofferdam

The Auxerre cofferdam, originally built in the 19th century, historically consists of:

• A 102-meter-long spillway, constructed of dry stone masonry and sealed upstream by a masonry facing.
• A 40-meter-long movable sluice gate with needle valves and trusses.

The technology of these structures relies on fully manual operation. Their replacement with modernized structures is necessary to optimize the hydraulic management of the rivers and their environment and to ensure safe working conditions for operating personnel. The project involves rehabilitating the automated movable dam, reinforcing the fixed weir, and constructing a fish pass. The selected solution consists of replacing the existing dam with an inflatable water dam, reinforcing the spillway through grouting, and constructing a fish pass on the left bank.

The project entrusted to BRL Ingénierie involves full project management, including:

Preliminary Design, Detailed Design, Construction Drawings, Building Permit, Final Design, Construction Supervision, and Final Acceptance

The rehabilitation of the structure specifically included:

• Demolition of the existing manual dam,
• Reconstruction of a movable dam with water-inflated gates,
• The creation of a fish pass,
• The reinforcement of the sill by grouting,
• The construction of a technical room housing the control, command, and supervision equipment,
• The development of the riverbanks,
• Addressing issues related to retaining structures and the proximity of the road and the SNCF railway line on the right bank,
• Managing waterproofing in conjunction with existing structures,
• Preserving heritage assets, particularly the central “pumpkin-shaped” pier,
• Managing the phasing and temporary structures required to carry out the work (cofferdams, pumping, access, flood management, concurrent river and land operations, etc.).

MC1, preparation of administrative procedure documentation

All regulatory procedures were handled internally by our expert environmental assessment team in consultation with our infrastructure team. The integrated approach—balancing structural development constraints with environmental considerations at every phase of the project—allowed us to minimize the overall impact of this project.

MC2, visitor information, communication

Highlighting the heritage value of the old dam through a permanent public exhibition at the lock site, featuring truss elements and needle gates salvaged from the dam, as well as information panels explaining the history and design principles of needle-gate dams.

MC3, external site inspections