From parking structures that are built entirely from sustainable materials to floating structures built on artificial islands, we’ve seen some pretty innovative multi-car complexes. But none of them compares to a new submerged parking garage in Brighton, UK. Wait, submerged? As in, under water? Yes.

Built nearly 40 years ago, UK’s Brighton Marina has climbed the marina ranks to become “the largest Marina complex in Europe.” Throughout the years, the marina has expanded to incorporate a village square, complete with shops, restaurants, and residential flats. A 1600-space parking garage, cinema complex, and hotel were later added. But even those additions don’t compare to the marina’s newest endeavors.

The submerged garage, which will house 350 cars safely underwater, is currently under construction. Phase 1 of the £41.5 million ($7.2 Billion, US) “West Quay Development” includes the submerged structure, two iconic towers, and a public promenade; the towers and promenade will be built on top of the parking garage, allowing a perfect view of the marina and surrounding ocean. The parking garage itself will be built with a double-height energy center, which will provide the entire development with power and heat.

When finished, the West Quay Development will include a total of 11 buildings, each composed of different architectural styles and ranging in height from 2 stories to 40. The 40-story tower, built with “slender, sinuous, and distinct composition”, will mark the eastern portal to the marina. All 11 buildings will be arranged around the large public promenade, and all components of the development will be made entirely out of concrete in the hopes that concrete will better withstand the harsh marine environment.

The submerged parking garage and accompanying buildings are being built on top of the seabed within Brighton Marina’s inner harbor. The seabed, which consists of strong, high-density white chalk and flint, provides a stable foundation for the permanently-submerged structure.

 

Building the Garage

The original design for the submerged parking garage called for a 4-sided cofferdam, but a value-engineering study showed that an existing quay, built from a sheet pile cofferdam and filled with concrete, could be used as the fourth side. While interfacing a new, 3-sided cofferdam with an existing one posed extra risk (existing quay is already corroded and wasn’t designed to be watertight), engineers were confident that grout socks would sufficiently connect the new cofferdam with the old one. Once all 4 sides were connected, a propping system within the cofferdam supported the quay to help prevent collapse as the water pressure was removed. De-watering the area took over a month.

 

After the water was removed, 13″-diameter steel tubular piles were vibrated nearly 45 feet into the seabed to provide support for the garage’s foundation. By using small-diameter pipes in closer intervals, developers were better able to pour a foundation with uniform thickness.

The garage is scheduled to be finished by March, 2015.