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Riverside Drive Bridge Underpass, Aberdeen

After full consideration, our specialist technical staff confirmed a flood defence project was entirely feasible, however given the nature of the environment; a completely bespoke flood gate design would be required.


As well as an initial site survey, a category B service survey, a site measurement survey and a surrounding area survey was also undertaken. SUMO and Betts Ecology also undertook an eco-systems survey to check that no wildlife or eco systems were in danger during site works.


When designing the gate, which measures 4m high by 5m wide, there were several things for our specialist technical staff to take into consideration. The gate needed to be held open at 120 degrees, so the space between the gate leaf and the wing of the bridge is wide enough to not cause entrapment of a person. Bespoke posts were designed to secure the gates open at this angle.

In addition, to fulfil the client’s requirement to enable full closure of the underpass, sealing was incorporated at the head of the gate, to provide full height protection. A bespoke, removable channel also was designed which allows for seals to be removed and replaced as and when necessary without the need to remove the gate from its hinges

Throughout the design development process, there were regular face to face design meetings so that both our specialist technical staff and the council team could consider and review all construction drawings.

The Manual Flood Gate designed by our specialist technical staff and was manufactured by a Worcestershire steel specialist, with manufacture taking 10 weeks. The gate was finished in bottle green anti-corrosive paint (RAL colour 6007), as specified by Aberdeen Council.


To ensure the location where the flood gates were to be installed was structurally sound, appropriate civils works were undertaken by an experienced on site team.

All finished surface levels were completed to allow water to run off towards the river away from the gate. A soakaway allows excess water to drain naturally into the ground and stop any ponding under the bridge.

To remove any run off water and to cover any small leakage rate through the gate, a drainage channel was installed and connected to two sump & pump units to discharge any water back onto the river side of the gate.

To house a power supply connector for the sump & pumps generator, a bespoke connection cabinet was made and installed at a safe level on the bridge top. In order to maintain the integrity of finished surfaces, the core surfacing between the underpass and the nearby cycle path was reinstated.


Working in such a demanding environment with a busy road running above the site presented a number of challenges.

Due to the location of the bridge, site lifting would be difficult. To overcome this, our specialist technical staff appointed a highly experienced transport company, Vic Haines. Using swivel lifting eyes and an experienced site team, all lifting was carried out effectively with great precision.

During initial site excavation, old drainage pipes were uncovered near the Flood Gate. These were investigated further to ensure there was no connectivity to the protected side of the gate.

Our specialist technical staff was in regular communication with the design team to ensure no snags occurred on site. Any changes or modifications throughout the process were coordinated with the on-site team, to ensure successful delivery of the project.


In its role as principal contractor, our specialist technical staff took on full responsibility for co-ordinating the safety management of the construction activities and sub-contractors as required by the CDM Regulations 2015.


Upon completion of installation, the gates were water tested up to 600mm using the council’s water bowsers. Pumps were also tested to ensure that the pipe work pumped water efficiently.

A training session was carried out with the client’s workforce to demonstrate how to operate the gate effectively in both open and closed positions. They were also fully briefed on the gate testing process and how to make regular maintenance check-ups on site. Our specialist team had the necessary experience and knowledge to deliver on time and within budget to the clients’ satisfaction.

Our specialist technical staff utilised and managed several support contractors on this project. They included; JR Donald (tarmac), Leiths Group (concrete), Reilly Concrete Pumping Ltd (concrete pump), Garic (welfare and fencing), Ramsey & Chalmers (reinforced concrete), Vic Haines (lifting and transport).