Project overview

The Thames Barrier is one of the world’s largest and most prestigious moveable flood defence structures. It was designed by Rendel who also supervised the construction of one Europe’s largest civil engineering projects undertaken between 1975 and 1985. The Barrier protects London from North Sea surges which, when combined with high astronomic tides and heavy fluvial flows, could result in flooding over large areas to effectively take London out of action for up to six months.

The structure covers the entire width of the River Thames at Woolwich, with four primary openings of 61m to permit navigation and six subsidiary gated openings.

A novel feature is the 19m high, 3,400 tonne Rising Sector Gates (RSG’s) in the navigational openings, which lie in recessed sills in the river bed when not in use to allow unobstructed passage of river traffic through the Barrier. Each gate is pivoted and supported between concrete piers, which contain the operating machinery and control equipment, with primary controls located on the south bank.

All gates are designed to withstand a design surge differential head of 8.4m from the downstream side. When a flood threat is imminent, the gates are swung up through 90 degrees to a vertical position and form a continuous barrier across the river.

Initial Studies (1960’s)

Following the disastrous tidal flooding and loss of life in the Thames Estuary and east coast, studies were under taken to estimate the potential levels and frequency of tidal surges and the impact these could have on the Thames Estuary and London. Various schemes and locations were considered before Rendel recommended a unique form of structure – a Rising Sector Gate – located at Woolwich Reach, with several gates of differing sizes completing the closure of the 520m river width.

Design Phase (1970 – 1974)

In 1970 The Greater London Council, instructed Rendel to proceed with their recommendation and, given the uniqueness of the scheme, the design was accompanied by considerable research and development. The novel concept of the RSG’s had to be tested structurally and hydrodynamically. Rendel directed the testing at Imperial College London, and Manchester and Cambridge Universities. Design criteria were agreed between the Executing Agent and Consultants, based on the earlier studies and required the design to withstand a 1,000-return surge tide, covering the conditions pertaining to the year 2030. A key parameter in the design approach was to ensure unimpeded navigation of the river during construction.

The project involved rebuilding the Apremont “needle” dam on the Saône in the Haute-Saône district near Gray.

Built in 1860 and then modernized from 1982 to 1984, the Apremont dam constitutes a retaining reservoir to supply a diversion canal (navigable) whose entrance is located about 200m upstream from the dam.

This dam consists of a fixed part 55m long (spillway) and a mobile part (needle dam) 51m long with 4 passes of 12m. A hydroelectric plant is located on the right bank.

The purpose of the project is to:

• to replace the existing “needle” dam with a functional and automated structure (2 main passes of 21m – flap gate solution and “Obermeyer” type hydro-gates solution),
• realize the restoration of the spillway, the existing structures of the dam which will remain in place and the protection against scouring,
• to build a fish pass of the 10 successive basins type, adjoining the right-hand side,
• to build an eel pass and a canoe pass,
• the construction of a dual-use footbridge, public and technical, on the dam.

EDF is the operator of the hydroelectric plants on the Rhine bays of Marckolsheim, Rhinau, Gerstheim and Strasbourg and, as consequence, in charge of the maintenance and upkeep of the banks on these reaches.

The work carried out consisted in protecting the internal side of the dikes, by preventing erosion by installing new riprap in order to:

• restore mechanical protection in weakened areas;
• re-establish banks with regular profiles (below and above the water level).

The underwater works were carried out from a floating pontoon equipped with a mechanical shovel. The external works were carried out from the crest of the dike.

The works lasted three years, on the left and right banks (on the German side).

To check and validate the works and define the work to come, the water level was lowered by about 1 m at the end of 2010

Ingerop is in charge of the BIM project management of lots 2 and 4 within an engineering grouping, for a 25% share of the fees.

The missions handled by Ingérop are:

• Design (feasibility studies, final design, assistance to the client at work contract phase)
• Supervision of the works
• Preparation of the environmental authorisation dossier
• Eco-design
• Project management (management of interfaces, costs, deadlines and risks, consultation)

The technical subjects handled directly by Ingérop concern:

• Layout of the canal and the restorations
• Earthworks (large earthworks) and related earth movement (problems of large earth surpluses)
• Engineering structures (canal bridges, bowstring bridges, double girders, PICF, etc.)
• Network re-establishment

BIM coordination

Repair and refurbishment of 120m of 500mm diameter outlet pipe. Slope stabilization of 2500m2 vertical cliff face over spillway. Raise the existing lay core of the dam by 2.5m in order to comply with dam safety requirements.

Ingeop South Africa have been involved from the application of funding from the MWIG to the preliminary and final design and finally up to construction supervision stage of the repair and refurbishment works to Lomati Dam. Investigation into the repair and refurbishment works began as far back as 2008, with construction commencing in November 2013. Once the dam safety requirements of Lomati Dam have been met, ISA will commence work investigating the raising of the dam wall in order to increase the dam yield. This will involve the possible use of fuse-gates at the existing spillway.