ByrneLooby in association with FAEC was commissioned by the RCJ to undertake the detailed design of both bridges, the approach causeways, the marine works including lining the channel, protection for the piers and navigation aids. Detailed assessments included carrying out a detailed study for the form, shape and location of both bridges. The location and height of each bridge were determined considering the existing causeway and bridge remaining in operation until each was opened.
Extensive geotechnical investigations were carried out to ensure the optimum piling solution was found for all piers in varying ground conditions. The long-term settlements of the approach embankments were also taken into consideration. Extensive studies were also done on the possible construction methods for constructing the pile caps and piers in the marine environment. Both bridges were designed using post-tensioned concrete box girders of uniform depth – each carrying 2 lanes of traffic, with inclined piers supporting the spans over water and vertical piers for spans over mudflats.