Dublin Bay was designated a UNESCO Biosphere in 2015 because of the rare habitats and species of wildlife it contained.

But this year its waters have been described as “filthy brown – somewhere between dark chocolate and milk chocolate” by local diving instructor Peadar Farrell of Curragh Sub Aqua Club, in a letter published in the Irish Times.

Farrell stated that the Dublin Port Company had been “dredging, bed-levelling and dumping its waste into Dublin Bay just off the Baily lighthouse almost non-stop since September 2017”.

In its natural state the port would be 3m deep but it was being deepened to 10m at the lowest tide to accommodate the biggest container ships, with two sea lanes dredged to that depth over some eight miles to allow the vessels to access the port. Regular maintenance-dredging would be required to keep the lanes clear.

According to Farrell the Dublin Port Company’s current permit does not allow dredging at this time of year, so it was relying instead on a permit first applied for in 2007.

With dredged silt being dumped at a shallow site ranging from 6-20m depth, he claims that it is dispersed across the bay almost immediately by wave action: “As a diver, I see the lobsters, crabs and other life walking around with an overcoat of silt on their backs.”

Farrell also pointed out that the dump-site lies in a Special Area of Conservation designated to protect its reefs and harbour porpoise population: “Where else in the world would a dump-site be allowed in such a protected area?”

Dublin Port Company confirmed to the Irish Times that it was using two dumping permits issued at different times but claimed to operate both “to the highest standards”.

“Extensive monitoring specified by the Environmental Protection Agency shows no impact of the dredging activity in Dublin Bay,” it said, claiming that the bay was “naturally prone to high levels of suspended solid within the waters”.

The Irish Underwater Council confirmed that its members had had to cancel all planned dives in Dublin Bay this year and said that the port's using the older dumping permit to extend its dredging season was “legal, but hardly correct”.

*  A 50-YEAR-OLD British man died at Malta’s Cirkewwa site after getting into difficulties on a group-dive on Tuesday afternoon (8 May). He was taken ashore where attempts were made to resuscitate him, but died later in hospital. Police are investigating.

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