Helmet Fire,
It was that question I was alluding to in the first paragraph of my response; yes you could have a fuel dump alternate which could be any landing area qualifying as a heliport.
Heliport. An aerodrome or a defined area of land, water or a structure used or intended to be used wholly or in part for the arrival, departure and surface movement of helicopters.
Note that this definition comes directly from Annex 6 Part III and should therefore be usable in any Contracting State - unless it is 'masked' by a local requirement. It has been adopted and used in JARs.