THIS vast underground cavern normally has a staggering 130 million litres of water sloshing around its concrete bowels.
Today it is empty, following the decision by North West Water to splash out £1.5 million on giving the 1960s structure a complete facelift.
Casual observers walking across the green fields which surround the company's Lostock Wastewater Treatment Works will not see any difference to the landscape.
But 20 feet beneath the surface lies a reservoir which, when full, could fill 1.5 million baths.
It took 12 days to drain the reservoir, allowing a team of five dedicated cleaners to begin the refit work.
One of them is Mick Taylor, from Heywood.
Dressed in a protective suit and donning a hard hat, he uses a huge hose to painstakingly blast the concrete surface of the cavern.
The work removes all of the dirt and grime that has built up since the last facelift more than two years ago.
And it is a job which sees him underground for eight hours a day with only small lamps lighting his way.
Mr Taylor said: "It can be quite tiring at times but it's worth it and it needs to be done.
"You find you can only hold up the hoses for about 10 minutes at a time because your arms start to ache then."
The lamps cast huge shadows upon the large, reddish walls and create a slightly eerie effect which would not look out of place in a Hollywood blockbuster.
The work is set to take about three weeks to complete.
Then the water will be allowed to pour back in from Thirlmere Aquaduct, in Cumbria, to be put to use in supplying drinking supplies to homes primarily in Manchester and some parts of Bolton.
It was initially drained in two parts, the water being redirected to other reservoirs in the area.
Asset manager Julian Cox said: "The reservoirs' facelift ensures we will continue to provide people in Greater Manchester with the best possible quality water." The man-made reservoir lies 20 feet below the surface.
It has concrete sides and contains metal pillars to hold up the roof.
The actual cavern is seven metres high.
Water ceases to be pumped in when it reaches the six metre mark.
A new hi-tech roof was recently placed on the reservoir boasting a waterproof membrane
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