During development of enclosures which have a structural role, the design engineer has to evaluate all the forces acting, i.e. their direction and magnitude.

The walls are subject to compression forces from the earth surrounding the chamber which increases with depth. Ground water conditions impose a potential for crushing the chamber and may add buoyancy. The dead load of the overfill and any vehicular load or other imposed stresses act upon the chamber. The chamber may contain liquid or be subject to hydraulic or pneumatic internal pressure.

The verification process includes manual calculation and/or finite element analysis which is vital in defining the design and manufacturing parameters for such products.