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1km rail tunnel named after the nearby village of White Ball built by Brunel (opened 1844 on the Great Western Main Line). Victorian brick-arch lining, which has deteriorated over the years including weathering and chemical reaction from the sulphurous steam trains. A refurbishment scheme was required to make it fit for purpose which was planned through various phases. The early phases of the project involved installation of the RAM Arch System and wire mesh to prevent loose bricks from falling on to the tracks. In latter phases of the refurb - the subject of the CAT3 check - sprayed concrete applied to cover the RAM Arch system coupled with rock bolts with butterfly plates were used to hold the concrete lining.

The Thames Tideway Tunnel is an under-construction 25km tunnel running mostly under the tidal section of the River Thames through central London. It will provide capture, storage and conveyance of almost all combined raw sewage and rainwater that currently overflow into the river. Once constructed, the main tunnel will have an internal diameter of 7.2m and will run from -30m at Acton, West London for over 25km under central London down to -70m at Abbey Mills in the East. It will connect 34 of the most polluting combined sewer overflows (CSOs), via transfer tunnels. The tunnel will transfer the captured sewage to the Stratford to East Ham part for onward delivery to Beckton Sewage Treatment Works.

The Puerto Suello Tunnel is a 400 m long single-track rail tunnel in San Rafael, California and was constructed in 1879. The 4.9 m wide and 6.8 m high tunnel was partially destroyed by a fire in 1961, was rebuilt for freight service in 1967 and closed in the mid-1980s. The tunnel was acquired by SMART in 2003, who retrofitted and then reopened it for commuter rail service in 2017.

The ground overburden above the tunnel reaches a maximum of 45 m and the tunnel was constructed using cut-and-cover and mined construction methodologies.

The East Side Access (ESA) project provides new Long Island Rail Road services to the east side of Manhattan, supplementing the existing service to Penn Station on Manhattan's west side and Atlantic Terminal in Brooklyn. ESA will serve approximately 162,000 customers a day, providing a faster and easier commute to the east side of Manhattan in a new 8-track terminal and concourse below Grand Central Terminal. The project encompasses more than 13 km of tunnelling.

The East Side Access (ESA) project provides new Long Island Rail Road service to the east side of Manhattan, supplementing existing service to Penn Station on Manhattan's west side and Atlantic Terminal in Brooklyn. ESA will serve approximately 162,000 customers a day, providing a faster and easier commute to the east side of Manhattan in a new 8-track terminal and concourse below Grand Central Terminal. The project encompasses more than 13 km of tunnelling.

Ottawa's Confederation Line runs from Tunney's Pasture station in the west to Blair station in the east, is 12.5 km long and includes 15 stations. The central piece is a 2.5 km long tunnel, running under the central business district of the city and including three underground stations. The twin track running tunnel and the three underground stations were constructed using the mined construction method in order to minimise surface disruption. The underground stations are located directly adjacent to existing, sensitive and historic buildings and required strict adherence to design and risk mitigation processing during construction. The Dr. G. Sauer & Partners on site team supported the contractor to meet these requirements.

The Relief Line South was a proposed expansion to the TTC Line 1 subway with five new stations planned from Osgoode to Pape Station undertaken by the TTC. The project has since been passed on to a new owner (Metrolinx) and further developed as the Ontario Line. Our role on the assignment included the 15% and 30% design for tunnel geometries, excavation and temporary support of two stations and one crossover. Tasks included production of 3D models, drawings, design reports and finite element analysis based on the SEM approach to tunnelling large caverns keeping surface disruption in urban areas to a minimum.