US Patent 10458093 On-site manhole casting system

A permanent on-site manhole casting system comprising a top, a main barrel, and a base. Each component consists of a ribbed plastic outer barrel and a ribbed plastic inner barrel with a plurality of plastic tie strips used to connect the said outer and inner barrels. A coupling mechanism consisting of a plastic outer coupling ring and a plastic inner coupling ring is welded to the coupling ends of the top, main barrel and base which connects the top, main barrel and base components. A concrete mixture is poured into the space between the coupled outer and inner barrels where the concrete is then allowed to set and cure and the filled form is then completely buried.