"Treatment plant operation in a rock cavern occurs in almost constant 
temperature conditions throughout the year, so the winter problems 
associated with the open tanks of surface plants are completely eliminated. 
Helsinki’s old treatment plants were located near the coast in weak soil areas. 
Settlement of the foundations had caused maintenance problems. 
There are no such problems in rock caverns. Being located near the coast, 
the treatment plant sites have already been planned and developed, mainly as residential areas." 
Office Manager Armas Kämppi