At the start of the study by Van Oord and TU Delft, various design concepts were evaluated to determine their suitability for the Dutch North Sea. The assessment considered environmental and hydraulic conditions, along with specific design criteria and requirements. These criteria included factors such as water flow, available space, protection against predation, oyster settlement potential, durability, stability, positioning, structural integrity, ease of installation, manufacturing processes, and transportation logistics.

Ten designs were evaluated and tested to address the three key phases of the structures’ lifecycle: the fall from the vessel during deployment, landing on the scour protection, and maintaining stability on the scour protection over a 30-year lifespan. The study combined predictive behavioural calculations with physical modelling, including tests conducted in the wave flume at the hydraulic engineering laboratory of TU Delft’s Civil Engineering faculty.

Results of the study identified the tetrapod design as the top performer across the evaluated criteria. Van Oord and Ørsted sought to test an alternative to concrete in the project. They selected GEOWALL, a material with concrete-like properties made from dredged sediment and natural binders. Since this material can only be molded into blocks, the reference block was chosen as the second structure for inclusion in the project. It also demonstrated promising results during the study.

Deploying the Droppable Oyster Structures (DOS) requires a simple vessel, such as a Crew Transfer Vessel. These vessels use roller conveyors to guide the structures to the vessel’s edge, where they are released into the water. Monitoring will be conducted through the collection and analysis of ROV video footage.

The structures will remain part of the scour protection and be removed only if the scour protection is decommissioned.