Kijlstra pre-cast units on the manchester metro link

Over the past two yeasr Kijlstra has supplied around 500 pre-cast concrete manholes and 200 drawpits to the Manchester Metro Link project.

No fewer than five types of drawpit, ranging in size from 600mm x 600mm to 1.25 m x 1.25 m, and three sizes of manhole, from 1,000mm x 1,000mm to 1.25 m x 1.25m, have been supplied. The total value of this equipment is in the region of £600,000.

The main challenges facing Kijlstra have been in the complexity of the design and installation details. Each drawpit can have connections on one, two, three or all four sides and there have so far been about 20 different duct layouts to accommodate, ranging from a single duct to as many as 32 on any one side of the drawpit.

To ensure  the connections for every drawpit were correct, Kijlstra coordinated an approval process to check and sign off every unit. This required very close liaison between the production team and site.

Deliveries also had to be very carefully coordinated to a number of drop locations around the Manchester area.

All units were supplied on timber bearers to allow off-loading by forklift and with edge surrounds for crane off-loading. This gave each site two options for handling – a major benefit as machines could be spread over various sites.

A major advantage was that the Kijlstra 1,200mm x 900mm manhole fits snugly between the Metro Link railway tracks. Kijlstra formulated a bespoke design modification that included a 1,200mm x 600mm chimney unit which reduced the manhole at the surface to allow the tight fit between the tracks.

This modification was made without compromising the capacity in the manhole below and while still allowing push fit connections for pipework up to 600mm in diameter

The main benefits of employing Kijlstra manholes and drawpits are speed and quality of the finished product.

All units are pre-cast in factory conditions and are therefore of a quality and precision that cannot be achieved in-situ.

Delivered to site on a just-in-time basis, the units are very quickly installed with virtually no need for any work to be carried out below ground. This means a major improvement in site health and safety management.

Nearly all connections are precision push-fit designs and are therefore quick to install and leak-free in operation.

But perhaps the most impressive advantage is speed of installation. It takes literally 20 – 30 minutes per manhole compared to one to two days for a traditional manhole, depending on the size. This is a significant factor and has helped keep drainage installations on schedule throughout the project.