Report - - The Cavern CSO – Accrington – July 2019 | UK Draining Forum | 28DaysLater.co.uk

Report - The Cavern CSO – Accrington – July 2019


Loyal to the Drain
Regular User
After a lovely Sunday service in a nearby town, I knew the M65 would lead me right past Accrington and that it would be a shame not to have a quick wander down one of the many underground spaces that the town has to offer.

I was aware that this place had undergone some improvement work so was keen to see what the changes looked like.

What I like about this rock blasted and spraycreted CSO is the sheer size of it, plus the fact that it lies 22 metres below the field above!
It is not just a CSO but also an 85 metre long by 4 metre wide storm water detention tank and sewer overflow chamber with a 3m weir height.

Now it must rain like hell in Accrington on occasions because high up in the chamber, many feet above the top of the weir are plenty of signs that the water fills this place right up to the roof despite an 8ft overflow tunnel to the nearby river. There are wet wipes hanging from the lights and the ubiquitous tiny polystyrene balls are stuck all over the ceiling.

The sewer enters the chamber as a massive 10ft tunnel and leaves via a little 2ft pipe at the end of the detention tank.

In 2011, the services of a Cornish company were employed to supply and install 10 large hydraulically powered self-cleaning screens to filter out debris from entering the river when the sewer overflowed.

As part of the 2011 project to install the screens, a new shaft was sunk down to the level of the CSO chamber. Here you can see the hydraulic lines coming down from the power packs in the control kiosk located high up at ground level.
At the bottom of the shaft, 20 hydraulic hoses neatly snake the wall to service each of the screens; one for flow and another for return.

Whilst the installation of these screens have reduced the sewer litter going into the river, they haven’t stopped it completely but it's a big improvement. There are still plenty of unpleasantries ‘decorating' the new handrails above the screens and also on the hydraulic hoses attached to the wall. Further evidence is wrapped around the outfall grille within the river basin.

However, the future for the river looks brighter as work is currently underway to intercept the storm spills from this chamber just before they reach the river and divert them into a new 7500 square metre detention tank which will return the sewage to the sewer when the levels recede.















It wasn’t until I got back home and checked back through my photos that I realised it was 11 years ago since I first set foot in this CSO.
These final six photos show what the chamber looked like back in 2008 when climbing up these ladders was a bit quicker and easier!









28DL Wood Burner
28DL Full Member
Nice! Loving the addition of that big shaft.

Wasn't this the one that filled up while you & @Ojay were in it?


Loyal to the Drain
Regular User
That is rather odd Ojay. Perhaps another sewer was diverted upstream for maintenance or maybe they pulled the plug at the local swimming pool to change the water!


28DL Full Member
28DL Full Member
Rode all under there on our bikes as kids, from one side of the town to the other. This was in the 1970s lol. Could go from the aquaduct in the center and end up behind the Bridge pub up church street. Great photos and a great report.