Blackpool outfall gets new dimension
A three-dimensional image of a new pressure chamber and discharge system at a Blackpool pumping station gave a clearer picture for all parties concerned, writes GHA Livigunn's Chris Edwards
Following the recent refurbishment of the pumping station, a unit located beneath the promenade, an issue with high surge pressures was identified.
As a result, the need for resealing and pressurising the system was highlighted. This would reduce the possibility of premature wastewater discharge on to the beach and promenade during poor weather conditions, and would minimise the likelihood of tidal ingress back into the pumping station.
This challenging project was governed by changing weather and frequently dangerous tidal conditions. MWH, working with United Utilities' Lingley Mere Solutions & Engineering team constructed a new pressure chamber with a buried discharge pipe system.
The pipe system comprises three 1,500mm and one 1,100mm inflowing pipelines with a common 2,540mm discharge pipe connected to the existing land shaft. All pipes are capable of resisting surge pressures.
The design also includes the reinforcement of the associated 30m-deep land shaft to receive the contained pressures.
Although ductile iron was initially considered for the pipework, the specification was upgraded to super duplex stainless steel. This decision was made in order to achieve United Utilities' long design life criteria.
It would provide maximum saline resistance in consideration of the fact that all the pump discharge lines would be encased in concrete and buried beneath the soon to be upgraded promenade.
With the design specification now involving the use of exotic materials, KMI Plus approached GHA Livigunn in November 2006 for specialist engineering and mechanicals advice on the use of super duplex stainless steel.
From KMl's perspective, working with such an exotic material, where thin wall design and special jointing techniques could positively impact on the final cost of the project and more than substantiated the use of 3D visualisation. Through 3D visualisation, all parties involved have gained a greater appreciation of the complex geometry and installation issues than could be achieved using 2D drawings.
It enabled a quicker understanding and appreciation of the works, especially to those not familiar with interpreting 2D engineering drawings. 3D has assisted in calculating precise pipe wall thicknesses, establishing the most suitable areas for pipe jointing, calculating required levels of concrete support and establishing precisely where the project will be at any given point in time.
The need for an emergency bypass channel during the initial construction stages was also highlighted and the ability to show the effect of storms and their impact on the construction sequence has proved useful.
KMI Plus' estimating manager Mark Hurst said: "The higher costs and procurement times associated with super duplex stainless steel meant there had to be absolutely no likelihood of any error in the manufacturing/fabrication of the pipes and fittings.
"Additionally, in light of the highly complex nature of the task, involving working in environments that could be filled with stormwater at a moment's notice and working within tidal cycles, we felt that the numerous different parties involved would have a clearer understanding of how outside influences could lead to a temporary cessation of works if 3D visualisation was employed."