Prefab Units Speed Up Glasgow Environmental Programme - continued
Precast components can be delivered to site and lifted into place in a few hours, allowing on-site activity to be completed very quickly and the excavation back-filled in typically 3 – 4 days.
Mike Gilmour, a project manager at Scottish Water, said precast has a number of advantages over in-situ construction:
In terms of the main benefits of precast over in-situ, the first is quality. The product is manufactured under factory conditions so the products are consistently of the same quality. Bad weather and unfavourable site conditions don’t affect it. Secondly there are delivery benefits in terms of time and cost
Keith Sinclair, Press Officer at Scottish Water says:.
Quicker projects are possible, using less space as we are not constructing it all using formwork and re-bar on site. This is useful when we are working in close proximity to the public, greatly reducing the impact on our neighbours and customers
Contractor, George Leslie Ltd, working on the Glasgow Environment programme to reduce the risk of flooding is using precast single module Vario CSO where economical to do so.
Steve Gainsley, project manager with Kijlstra said:
At Morriston Street we supplied a panel system for a CSO located in school grounds next to a busy road. The programme timescales were tight as the CSO had to be constructed during the summer holidays and the precast solution allowed the programme dates to be achieved.
Due to it’s speed of construction a two-piece Vario unit also proved the ideal solution in areas where traffic management was a major disruptive factor. Andrew MacLeod, Construction Manager with George Leslie Ltd said:
Reduced time on site is undoubtedly one of the biggest advantages of precast
However, he points out that in some instances in-situ construction is still appropriate.
Depending on the location it might be more economical to use in-situ concrete. There are about 200 CSOs on the Glasgow Environment Programme, and George Leslie Ltd are involved in over 90 of them across the Shieldhall and Dalmuir catchments, but not all will be precast.
Kijlstra’s CSO chambers are essentially modular structures comprising standard components, but they can be supplied as bespoke designs. They range in depth from typically 2 m – 6 m deep. Wall thickness is typically between 300 and 400 mm depending on CSO depth. Precast can typically reduce this by a around 15%.
The concrete mix design complies with Scottish Water specification, which is The Scottish CESWI. Delivery time from order for a single piece (Vario) chambers is 4-6 weeks and panel system chambers 6-8 weeks.
For instance, at Busby Bridge CSO, as access was restricted, we designed the CSO panel system to be installed using a 20 t. wheeled excavator, without the need to use a large hired-in crane
says Steve Gainsley.