Tony Gee carried out the design of all temporary works associated with the box installation, as well as independent checks on other temporary works.
The A23 carriageway is designed to pass under the Tattenham Corner Branch Line at Smitham Station. It was vital that the station and the railway remained operational throughout construction, so an engineering solution was required that avoided closures. The box was constructed offline and jacked into position while trains continued to run overhead.
Before excavation of the jacking pit could begin, a piled concrete slab was constructed to maintain access to the south of Smitham Station. 46 steel tubes were then anchored into the slab. These tubes, in conjunction with a tunnelling shield, provided the temporary support necessary to enable the railway to remain operational.