Hi thunberg
I would send a mail to one/any of the staff/persons listed under Technics and Maintenance here http://www.gotakanal.se/en/artiklar/Kontakt/Contact-AB-Gota-kanalbolag/
They do this kind of work for a living, and in a excelent way, so they would be able to tell you precicly what to do, and not to do, for a permanent fix.

Nice place you got there

cheers


PAUL