Wet Sink Pollution


I have recieved the below message from Tim Nichols of GSS:
Dear All

We believe that sometime Saturday 25th and Sunday 26th of March there has been a break in the pipe that takes the sewage from Joyford pumping station up Joyford Hill to the Lonk. This means the sewage has nowhere to go besides the limited tank storage before it overflows down the CSO that feeds Dry Sink. The water then enters Wet Sink, some at the inlet just before Cross Stream Junction, with the bulk entering at the Cascade.

We identified this during a trip on Sunday. We knew something was amiss as the Joyford Hill road was closed and sewage disposal tankers were at the pumping station. The CSO was running freely and increased in discharge between entering the cave at 10am and exiting at ~4.30pm. It did however appear to be running clear, unlike in the past when we have seen it coloured grey.

We abandoned any thoughts of going downstream from Cross Stream Junction due to the smell which amplified considerably at the Cascade.

We met with sub-contractors of Welsh Water after our trip who told us tankers were coming regularly and that there was a break in the pipe and they hoped to fix it within a day or two.

Paul Taylor kindly followed up on this with a visit today with Gareth and his updated message is below.

"Gareth and myself visited the site today. After 14 hrs of digging yesterday they failed to find the break in the pipe. Further digging in
various locations looked like the break was located and a new section of pipe put in.
Yet to be confirmed.
A tanker was operating today removing approximately 3000 gallons per load.
However, this amount removed only dropped the level briefly below the overflow level to the CSO for a very short period of time before the
incoming flow brought it back up to the Overflow Level. Hence the reason why the CSO was continuing to flow. I took photos and video today.

Initially the WW chap that we met at Joyford Mill tried to say that it was a Storm Overflow that was running. However, once I explained the
system to him (He did not fully know how it worked) He had to admit that I was correct in saying that what was coming out of the CSO was in fact
the overflow from the tank.

They would need multiple tankers to remove a large qty to get to a situation where the CSO would not flow during the time that the tankers
were off site.

I am going to make a complaint about this.

Also following my phone call this morning to WW I received a call back from WW to say that they had no trace of any incident at Joyford in the

This seems pretty poor to me that it was not flagged up.

I am not 100 % sure but there is a strong suggestion that the leak started on Saturday afternoon.

Although I was not able to see for myself but I was told that the screens were doing a very effective job of keeping out any solids from the
overflow and it was only liquid. I appreciate that this is not ideal but better than we have had in the past.

I was also told today that the Joyford and I believe Lonk Pumping Stations are both due for Major Refurbishments with new pumps etc etc.
Again this is not ideal but it is another step forward."


Active member
As an update. The pipe was finally fixed on Monday afternoon 28th March. Heavy rains followed on 31st and the CSO was flowing on 2nd April. This time we made it to Kuwait. Stream way smelled bad but otherwise OK. The pump filters seem to be doing their job. A return downstream on 5th April, all good - no smell. FoDCCAG will be investing in weather and pollution monitoring and we hope to make this information publically available. If anyone is planning a visit, don't let these posts put you off. The cave system is a UK classic. Please PM me if you have any queries if planning a trip. Please contact Andy Clark for access key as per usual.