Taunton & Somerset NHS Foundation Trust
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Pipefix have been involved in this project for several years since the initial discussion and development of the concept with the consultants Houghton Greenlees & Associates, the Hospital Estates team and Wessex Water.
Technical Elements:
- Thrust Boring 180mm tunnel under access road
- Pipe Ramming 250mm steel duct under new building
- Electro Fusion welding MDPE pipe
- Deep excavations up to 3m
- Jointing to existing 100m Galvanised Steel pipework
- Heat tracing external pipework
- Waterproof PIB insulation work
Musgrove Park Hospital in Taunton is a large site that originally drew water for the whole site from a single main at the perimeter. Whilst this in itself is not a problem, it meant that in the event of a problem with the water supply system on the furthest parts of the site they might have to shut off the water supply to the whole hospital to deal with it. This had been identified as a significant operational risk and contingencies were sought.
After reviewing the Wessex Water distribution zones in the area another Wessex Water main was identified on the other side of the site that could be accessed fairly easily if a link main of about 40 metres could be installed.
The new link main would be constructed using 180mm and 125mm diameter MDPE barrier pipe, jointed using electro-fusion fittings. The new pipe would be connected to the existing water distribution system at various points using bolted flange adapters.
The additional water supplied by the new connection would make the management of the water distribution on site more flexible and reduce the risk of the whole site ever being out of water, increasing the security of the supply significantly.
There was a major logistical challenge presented by the scheme, which was that the new link main would have to cross the primary access road into the hospital (pictured). This road is the only route into the site that can be used by the emergency services, which meant that closing the road to dig a trench across would never be allowed.
We presented two options to get the pipe across the road:
Option 1.
Close half the road at a time, install traffic light management and excavate across the carriageway. This would be a high risk approach and incredibly difficult to manage whilst meeting all of the site protocols. It would also add thousands of pounds to the job to cover the traffic management system and reduce efficiency on site. The paperwork to get it done would have taken hundreds of man hours, and the contingency plan, if implemented, involved some extraordinary measures, including setting up an alternative landing site for the air ambulance!
Option 2.
Thrust bore a 180mm tunnel underneath the road from one side to the other using a 180mm mole and pull the new 125mm pipe through. This would require real skill to avoid the existing services and cables under the road, and success with thrust boring is never guaranteed.
Naturally with all that was involved in Option 1 we agreed with the project manager to attempt Option 2 to thrust bore the supply under the road first
The pictures show what a 180mm mole looks like. It’s not hard to imagine the damage that one of these would do to anything that gets in its way – cables, gas pipes, drains – nothing is going to stop this except solid rock or concrete. The risks are evident.
After several hours of careful site preparation our engineers successfully bored the hole under the access road. Our client was absolutely delighted that the plan had worked, saving them a lot of administration, headaches and expense.
There were other technical challenges involved in the project. Part of the 180mm section of link main also had to go under a brand new 5 metre wide corridor called the Jubilee Link. Pipefix used a tool called a ‘Grundoram’ (pictured) to ram a 250mm diameter steel duct under the building. This technique is similar to thrust boring – a hydraulic ram head is attached to the hollow steel duct and it hammers the duct through the soil like an apple corer. The head is removed once the pipe has been rammed in, then new sections are added one at a time and the ramming repeated until the desired length of duct has been reached. The soil within the duct is jet washed out, enabling pipes and cables to be pulled through.
The operation went very smoothly and the 180mm pipeline was successfully pulled through under the new Jubilee link building.
The link main then travelled underground across an open courtyard, rising out of the ground up on to a flat roof area where it was connected to the existing galvanised 4” steel pipework on the roof. All the external steel pipework was heat traced and insulated with PIB waterproof insulation.
The link main, valves and connections are all complete, and at time of writing we have just been asked to price a second batch of works on site to install a further link elsewhere.
‘Another seamless operation by Pipefix. Well Done!’
Martyn Frampton – Partner – Houghton Greenlees & Associates Ltd
Experience
We have a strong track record of delivering difficult projects for commercial and public sector clients. Most recently these have included diverting water mains for a new hospital building, the link main described in this article, and a water mains and sewer diversion around a new prison building.
Further information
Website www.pipefix.co.uk
Email ben.fredriksen@pipefix.co.uk
Phone 01305 230465
