A ballast system is provided for use with least partially buried pre-formed chamber, the system having at least one ring formed of a plurality of interlocking ballast block ring segments; each ring segment being configured with at least one male interconnect and at least one female interconnect, each said female interconnect being configured to receive a corresponding male interconnect, each ring segment comprising a containment form shell and cast mass; and corrosion resistant locking pins whereby each female interconnect is secured to a corresponding male interconnect.