The Merseylink construction consortium of FCC, Kier and Samsung C&T, which is building the £600m crossing for Halton Borough Council, has completed the trestle bridge – a temporary bridge that will act as an access platform for construction teams to work from when building the new structure.
It is the first bridge to be built over the River Mersey in Halton since 1961, when the nearby Silver Jubilee Bridge was opened.
The trestle bridge is used by construction vehicles but is not open to public traffic. A lifting section, which can be raised to allow boats to pass, will be installed shortly.
Merseylink project director Richard Walker said: "Completion of the trestle bridge marks another important milestone for the Mersey Gateway project. It will provide us with full access to the river, enabling work to start on the central cofferdam."
The trestle bridge will be dismantled and removed completely when the new Mersey Gateway Bridge is in place, expected to be in 2017.
Thomas Duncalf, from Runcorn, was one of the first workers to walk across the new trestle bridge. He said: "I'm excited to be working on the project. It's a great opportunity. My grandad worked on the Silver Jubilee Bridge and it's an important part of my family history. I feel honoured to be part of the team building the new Mersey Gateway bridge."