STRATEGICALLY located, with direct access to the M62, the Kingsway Business Park near Rochdale will be home to one of the largest business parks in the north west of England.
The 170ha site, 114ha of which will be developed, lies on the western slopes of the Pennines. It is on undulating ground and narrow valleys, and is subjected to high rainfall. Consultant White Young Green also faced the problem of waterlogged marshland.
Site geology comprises glacial drift - low to intermediate plasticity sandy clays to extensive volumes of sand and gravel. These overlay interbedded mudstones and shales from the Lower Carboniferous Coal Measures.
Deep coal mining was carried out on the site in the past, but investi tions showed that this would pose no hazard to development. However, desk studies have revealed there may have been shallow mine workings in a small part of the site.
So a rig crew put down a series of rotary-cored boreholes to below the likely depth of the shallow workings. Fortunately for Wilson Bowden Developments and principal contractor Costain, there was no evidence of workable deposits.
To minimise long-term settlement of the soft ground, site workers are selectively placing granular materials beneath buildings earmarked for early development.
Topsoil that needs to be stored temporarily on site will be used as surcharge on these areas to accelerate consolidation settlement and preload the ground.
Extensive remodelling and major improvement of the existing M61 Junction 21, now under way, will provide access to the business park.
This is expected to be ready by the end of 2006.
Work will involve demolishing a farm traffic bridge that will be replaced by a wider-span structure.
Bridge piers and bank seats will found on 600mm diameter, 12m to 20m long bored cast insitu piles bearing on the glacial till.
A 200m long contiguous bored pile-retaining wall next to the new motorway junction roundabout will ensure minimised land take. The wall, made up of 600mm or 750mm diameter bored cast-in-situ piles up to 15m long, will retain a height of 5m, with an 8m slope above.
Other work will include installation of vibro concrete columns under a geotextile reinforced load transfer platform beneath structures sensitive to settlement, with a tapered treatment zone extending beneath adjacent embankments. This will reduce the amount of peat and soft clay that has to be excavated.
The site will also feature a 9m diameter foul-water pumping station, 12m deep, which is envisaged to be built of precast units installed by segmental jacking. Here, tension piles will prevent 'otation.