Embracing New

Brenwal’s innovative team are always looking
to new technology to help solve historical

Manhole Refurbishment

Jersey’s sewer network relies on a series of foul pumping stations to carry flows to the central treatment works at Bellozanne.

Night time reductions in flow results in sewage turning septic and producing hydrogen sulphide gas (H2S). The gas dissolves in water to form sulphuric acid which attacks the concrete structures of manholes and pumping stations.

The degradation of the concrete leads to a major loss of the structural integrity of manholes and pumping stations. This has traditionally been treated by means of specialist renders and other cementitious coatings which have proved to have limited effect and durability.

Brenwal were awarded a contract to refurbish a trunk foul sewer which crossed Jersey’s airport. In addition to the relining of some 800m of foul sewer, the project involved the structural restoration of six manholes, one of which was located under the runway.

As previous methods of manhole rehabilitation had proved unsatisfactory, and due to the important (and largely inaccessible) location of the manholes at the airport, Brenwal proposed a solution using a GRP lining system. This has proven to be a great success and Brenwal were asked to utilise this system for the structural restoration of several additional manholes and pumping stations.

As a result of this order, Brenwal have partnered with a German plastics specialist to fabricate bespoke liners for each manhole. Conventional measurement of manholes lacks sufficient accuracy for precise fabrication work to be carried out. So Brenwal utilise a scanning and 3D modelling system to determine the exact shape for the various lining components. Channel and benching units are fabricated from GRP in Germany. They have a polypropylene (PP) circumferential rim that allows the shaft liner to be welded to the base. Soffit and man access liners are also formed from PP and are welded in situ. The entire inside surface of the manhole is effectively sealed with a new lining which is resistant to H2S attack. The annulus between the new lining and the existing structure is injected with grout. The system is versatile and can be used to line structures of any shape and size.

Point cloud from scanner.

Wire frame from point cloud.

Fabrication Concept.

Liner visualisation.

Base units ready for shipping