Divers have said they have abandoned the use of Dublin Bay because of the poor of visibility in the water following dredging by Dublin Port Company.
Clubs and instructors say the levels of silt particles in the water have made it too murky to undertake any diving this year, and lobsters and crabs are walking around with “an overcoat of silt on their backs”.
The port company undertakes periodic "maintenance dredging" to keep shipping channels clear for navigation. However, it has been carrying out "capital dredging" since last October to lower the depth of the bay as part of its Alexandra Basin Redevelopment Project, which was granted planning permission by An Bord Pleanála in July 2015.
As part of this project, which will allow cruise ships to be brought up the Liffey as far as the East-Link bridge and give the port the capacity to accommodate the largest freight vessels in use, the company is licensed to dump the dredged material at sea at the Burford bank, 5km southeast of Howth.
‘Filthy brown’
"The seawater in Dublin Bay at the moment is filthy brown, somewhere between dark chocolate and milk chocolate. None of the local scuba diving clubs have been able to start diving as yet in 2018," diving instructor Peadar Farrell said in a letter to The Irish Times.
The port company had extended its dredging and dumping season this year by using an older dumping at sea permit than the one secured as part of the Alexandra Basin project, Mr Farrell said.
‘Overcoat of silt’
“Every plant, fish, filter feeder and living thing in Dublin Bay is now coated with a fine silt after the months of dumping,” he said. “As a diver I see the lobsters, crabs and other life walking around with an overcoat of silt on their backs.”
When the port company eventually achieves the depth required for the larger ships, it will have to continue regular dredging to prevent the tide restoring the seabed depth, he said. “They are turning Dublin Port into a very unnatural place,” Mr Farrell said.
Monitoring
The port company said it was using two dumping-at-sea permits, issued at different times, but said it “operates both permits to the highest standards”. It said “no contaminated materials” had been dredged during its 2016, 2017 and 2018 activities.
“Extensive monitoring specified by the EPA [Environmental Protection Agency] shows no impact of the dredging activity in Dublin Bay,” it said. “ Satellite images taken prior to the dredging activities show that Dublin Bay is naturally prone to high levels of suspended solid within the waters.”
The Irish Underwater Council, representing some 2,000 divers, said its members had to cancel all planned dives in Dublin Bay this year. It said the use of the older dumping permit to extend the dredging season was technically "legal, but hardly correct".
