Why no fuel dump for AWE751 ?


I’m not a pilot, just an aviation interested person. So pardon me if I don’t use the right words.

I notice that US Airways AWE751 had a technical problem and decided to return to the airport of origin (Brussels). There is was in a holding pattern for more than 2 hours, probably because it was too heavy to land (according to this article (in Dutch) standaard.be/cnt/dmf20141023_01337880 )
I am just wondering: why didn’t they dump fuel while returning over the sea? Or fly back to the sea and dump fuel there? Technical reasons? Ecological reasons? Other reasons?

Interesting speed graph by the way:
flightaware.com/live/flight/AWE7 … L/tracklog

Thanks for your help.