The foundation work for the two new bridge supports on the A31 widening work will begin next week ahead of the current bridges being demolished.
From 12th April for around six weeks, the retaining walls will be installed to allow the cranes to start work.
This work will be carried out using piling, which is a method of installing foundations, posts and walls.
Large specialist drills and cranes to drill holes that are filled with concrete into the ground will be used to create the retaining walls by pushing piles into the ground using a technique vibratory piling. This uses vibrations to sink the retaining walls into the ground.
National Highways says some of the work will take place during the day, which may be noisy for local residents.
New signs have also been added to advise drivers of the pedestrian crossing on the slip road from Ringwood onto the A31 towards Poulner Hill, and the speed limit has been reduced following concerns.