Method of constructing a large elongate fluid-confining internal structure surrounded by an external structure

A method of constructing an elongate composite structure having an elongate internal fluid confining structure for a fluid supply plant surrounded over substantially its entire length by an external structure, the method comprising the steps of:

• separately constructing at least two composite modules, each of the modules being constructed by joining a section of the internal structure to a corresponding section of the external structure;
• removably joining together the at least two composite modules by joining the sections of the internal structure to each other and by joining the sections of the external structure to each other;
• separating the removably joined composite modules and transporting the separate composite modules to a site where the composite structure is to be erected;
• and
• erecting the composite structure at the site by vertically erecting a bottom one of the composite modules and joining a further one of the composite modules thereto by fluid-tightly and non-removably joining the sections of the internal structure to each other and by joining the sections of the external structure to each other to form the elongate composite structure on the site.