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In July 2007 we started work on cleaning and repairing some of the main water pipes that supply customers in parts of Lancashire. At the moment we are working on two pipes in the Lancashire area - the Hodder large diameter trunk main and the Lancashire Conjunctive Use Scheme (LCUS). Between them these pipelines supply up to 219 million litres of water a day to 850,000 people in Lancashire.
Since the pipes were first put in place up to 90 years ago, deposits of iron and manganese which occur naturally in raw water from our upland reservoirs have built up on the inside of the pipes. Although not harmful to health these deposits can result in discolouration of our drinking water.
It is because of these deposits inside of the Hodder large diameter trunk main that we have chosen to repair the pipeline.
Large diameter trunk main is the term we give to the giant water pipes that feed the vast majority of our customers in the main conurbations of the North West. Some sections of these pipes are big enough for an adult to stand up in. The Hodder large diameter trunk mains system consists of two cast iron pipes which run from Hodder water treatment works and Stocks reservoir near the Forest of Bowland to the Fylde coast. The first pipe was laid in the 1920's, and the second in the 1950's. The Hodder pipeline is 84km long and supplies water to customers in the Ribble Valley, Blackburn, Preston, Blackpool and the Fylde coast.
We are cleaning and repairing the Hodder trunk main to remove the build-up of deposits inside the pipes using the most up-to-date technology available. The Hodder pipes have never been cleaned before and this is the first time that work on this scale has been undertaken in the water industry.
We will clean and repair the pipes in five phases between May 2007 and March 2010, using a range of state-of-the art techniques.
We will repair pipes using techniques known as 'sliplining' and 'thin wall lining'.
Sliplining is the term we use for when we insert new plastic pipes into existing cast iron mains. This can be a more cost effective way of replacing or repairing a corroded pipe (and a lot less disruptive) as we don't have to dig up a highway to lay a new one. An access hole is created to gain entry to the existing main and the new pipe is 'inserted' into it.
Thin wall lining is similar to sliplining. A thinner, more flexible polyethylene pipe is inserted inside the existing pipe in a folded position. Once in place water pressure causes the new pipe to open up and create a lining against the inside wall of the old pipe.
After the clean and repair work, we will use CCTV surveys and other tests to make sure we have been successful.
We will be carrying out our cleaning programme using 'pigs'.
The pig is a bullet shaped object made from polyurethane foam, which is pushed through the water pipe using water pressure. As it moves forward, the surface of the pig scrapes away soft deposits from the walls of the pipe. We may need to carry out this process more than once depending on the amount of deposit.
To ensure that we maintain your water supply during this work, we are going to clean one of the Hodder pipes whilst maintaining supplies through the other. It is unlikely that you will notice any change in your water supply as we will continue to use the same water source. Although during peak periods we may use water from boreholes to supplement water supplies in some areas.
Please be assured that the quality of your drinking water will be to the same high standard as you currently receive.
As the work we are doing will be concentrated on the route of the pipelines most customers should not be affected by the work. However if you do live along the route of the pipelines you may notice an increase in traffic and construction related noise.
Occasionally we may also need to divert traffic for short periods. If we need to do this in your area we will let you know in advance.
