Some local boat owners operating out of Penarth Marina and Cardiff Bay are now saying there’s a significant build-up of mud in the undredged waters of the Bristol Channel.
There’s always been a large area of mud off the shore of Cardiff and Penarth which is exposed at low tide, but it’s being said an increasing number of boats are unexpectedly going aground – apparently because of an increase in mud levels .
The official dumping ground for “spoil” (dredged mud) – including allegedly ‘nuclear’ mud dredged from the Hinkley Point nuclear complex is the Cardiff Grounds Spoil Disposal Site – a mile offshore from Penarth.
Now however a well known local skipper has warned that the existing plateau of mud at the Cardiff Grounds is becoming higher . He says the addition of thousands of tons of mud from the Hinkley Point site may mean there may no longer be sufficient depth of water at all states of the tide to cover the Cardiff Grounds . In that case the mud could become exposed to the air at low water.
The increase in the level of mud on the sea bed is unlikely to have been affected yet by the mud from the Hinkley Point nuclear complex.
So far only a small fraction of the 320,000 tonnes due to be deposited there from Hinkley Point has yet been dumped at the site .
However the Cardiff Grounds dumping site is also used by Associated British Ports to dump mud dredged from the approach channel to Cardiff Docks.
It’s thought at least some of this mud is being re-distributed by tidal action and is increasing the height of local tidal mud banks as well as the Cardiff Grounds disposal site itself .
A local boat-owner David Watts of Cardiff Bay Yacht Club has filed a comment on the Welsh Anti Nuclear Alliance website saying that he recalls getting stuck on the Cardiff Grounds mud dumping site some 4 years ago at about 30 minutes before Low Water Springs [ when the tidal range is at its greatest].
He says that the area “dried out at low water and was exposed to atmosphere.” That was in 2014 . Now the depth of water is even less..
The Cardiff Grounds spoil-disposal site is supposed to be constantly covered with sea water at all states of the tide – but Mr Watts says that’s not the case .
Mr Watts says “Traditionally the spoil ground was intended to provide a disposal area for mud and sea bed constituents dredged from the Wrach Channel and entrance to Cardiff Docks system together with Cardiff Bay. This practice continues on an annual basis and it is likely the Spoil Ground has received even more spoil than I observed in 2014.”
He says “In any event, the dumping of a further 300,000 tons at that location would deny similar capacity to be available for the true intended purpose ie to receive spoil arising future dredging at Cardiff. “