The Millers Point Gasworks plant contained a range of structures that included tar tanks, gasholders, gasholder annuli, coal stores and other manufacturing buildings. The remediation on the Site is targeting the historic structures that remain in the ground. For example, a ‘tank’ is a section of sandstone that was carved out in order to store coal tar or other wastes, which were generated during gas production. An ‘annulus’ is a ring shaped, underground structure that formed the base of the gasholder that stored gas until it was used. Heavy particles present in the stored gas were captured in annuli.