The Minister of Transport had given priority in the Trunk Road Programme to the Extension of Princess Parkway, in Manchester, through to Bowdon, in Cheshire. This included the proposed Bowdon to Wythenshawe Section of the M56.
Wilmslow Road interchange
The risk of subsidence due to salt mining restricted the location of the motorway to a narrow band north of Rostherne. From a junction with the A556 Trunk Road the route passed to the south of Bowdon and Hale, to a junction with the A538, north-west of Wilmslow. Between this point and a terminal interchange at the junction with the A560, an intermediate interchange was to be built for a dual two-lane carriageway motorway link, directly serving Manchester Airport.
A total of 24 structures was required spanning railways, canals, the River Bollin and various side roads.
The contract for the construction of the 6½ mile section of dual three-lane carriageway motorway began in July 1969.
From the River Bollin, through Wythenshawe, Keuper Marl is close to the surface and the designed profile required a long cutting in this area. The total of 2.5 million cubic yards of earthworks proved to be very difficult, due to the poor quality of the material, and the need to use as much as possible in forming embankments. On one length of embankment an extra layer of cement-bound granular material was laid, in order to strengthen the sub-grade.
Alternative forms of carriageway construction had been offered to tenderers. A semi-flexible base of a 7 inch thickness of dry lean concrete and a 3 inch thickness of dense bituminous macadam was the choice in the lowest tender.
As a major part of the line of the motorway had been located to pass through estate coverts, in order to reduce farm severance, little landscaping treatment was required. In Wythenshawe, however, where the route had been protected against development for many years, unsuitable excavated material was used to form protective mounding. This had the additional advantage of providing noise baffles for adjoining residential property.
This Section of the M56 was completed and opened to traffic in January 1972.