Project Details

Grout fill was installed in the 564m long anulus between a new 1600mm outer-diameter HDPE intake line and an existing, abandoned 1797mm inner-diameter steel intake line. Filling the space between the two pipes prevents the HDPE from possible collapse during under-pressure conditions. A custom, highflow grout mix was developed for this purpose. Prior to the successful slip-line installation of the new HDPE intake, divers broke through concrete cover over the existing intake line and cut grout ports through the steel pipe. The offshore and onshore accesses were then bulkheaded closed. Three barges were involved in the grouting operations. A flat-deck material barge carried the 1t totes of dry, pre-blended grout mix as well as the concrete batch plant and the grout pump. A large spud barge held the material/pump barge in place as the grouting operations advanced between ports.

A second spud barge housed the divers, a support crane and means to seal off the grout ports as given stations were filled and the pumped grout advanced between stations. Grouting operations started at the offshore end of the site, progressing towards shore. The 1t grout totes were fed to the batching plant, mixed, transferred to the grout pump and then pumped through the 50mm grout line. At each grout port, the grout hose was inserted down to the invert of the anulus prior to grout delivery. Grout pumping then commenced and the grout/water interface would progress towards the shore as the volume of grout in the anulus increased. When a port became visibly full, that port was sealed and the diver walked the grout hose to the next port. This operation was repeated until the entire length of the anulus was filled with grout. Grouting commenced on September 9, 2021 and continued uninterrupted until its successful completion on September 11, 2021.