01.01.07
Ashwood pumping station emergency work
Source: Rail Technology Magazine Dec/Jan 2007
It was August, and three failures due to turbidity had occurred at Ashwood, forcing emergency action to be taken.
The turbidity was due to iron, but there was no iron in the boreholes or the contact tank they supplied. This meant that the suction mains to the booster pumps had to be the culprit. Pipe samples were taken from the few exposed and accessible places, and limited CCTV surveys carried out through the holes where the samples were taken. These showed no one bad area : the whole booster suction main would have to be replaced. A daunting enough task if it could be replaced in a planned way but this had to be done quickly. Not only had the turbidity problem to be overcome to satisfy the DWI, but Prestwood pumping station refurbishment loomed and Ashwood threatened an unacceptable delay.
The scheme kicked off with a morning meeting between production, IWS, UPLS and capital investment delivery, which resulted in a high level design to lay new 600 & 400mm mains along the shortest distance, knocking through the walls to take advantage of the basement access this would give. In addition, the rusted bell mouth inlet and outlet pipework to the contact tank would be taken away, blasted, coated and refitted. A programme was agreed which would carry out the work just in time to start Prestwood on the scheduled date in the first week of December.
The first trial holes quickly uncovered a four foot tall, three foot wide brick structure which was thought to be a large culvert.
It turned out to be an old flue from when the works was steam driven, which by then had caused two precious days delay. Fortunately the team turned it around with UPLS using the structure to form part of the mains route and saving enough digging time to pull back the programme.
The design was to knock through an external wall and two inner walls to allow short and easy access to the booster pumps. However, each wall was up to four feet thick and made of engineering bricks which were extremely strong. Instead of being a simple knock through, the job now required lintels to be placed before the holes could be knocked out. The conditions inside the basement were particularly unpleasant and UPLS work for over a week to knock through the three holes.
Next, grey asbestos was found in the tunnels, and work had to be stopped until it was removed. Only after the event was it proven to be a safe type and no one was at risk.
Whilst UPS were under pressure in and around the pump house, IWS were beginning to understand the joys of removing substantial pieces of pipework from a small contact tank.
Firstly the rusted bellmouths had to be unbolted and then manhandled to the opening. At initial design stage we had missed the fact that there was only one opening, above the outlet, so the inlet bell mouth had to be dragged to that end, and then hauled out with a crane. During some of this work, both sister companies worked together to provide enough manpower muscle to get the job done. The bellmouths had to wait for days inside the workshops until dry enough to shot blast and coat, and all the time the clock was ticking.
IWS fabricated the booster to main connections and again worked hand in hand with UPLS to work effectively. Other minor snags arose, stairs had to be moved, plates had to be coated. Nothing was easy.
By this time, the station looked like a real building site. Not only were there trenches everywhere but rain had made the small working areas very sticky. The team persevered, and production did a sterling job commissioning the pipework as soon as was possible. Then disaster struck again. A bacti failure showed up problems both with the drainage and the well heads. Production, water quality, capital investment delivery, IWS, and UPLS all played a part in turning round an exceptionally quick two day fix enabling Ashwood to go back into supply and the Prestwood scheme to begin just a week late. The site now looking the professional works it is.
A quality job finished on time and a really big well done to every one involved.
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