Waimangaroa Bridge – Waimangaroa

Moore Construction was contracted to pile the existing Waimangaroa Bridge in Westport on the South Island’s West Coast. This consisted of 1050mm DIA casings installed to 22.5m DIG. Each pile casing was 16mm wall, driven utilising Moore Constructions CKE800 (80 ton) crawler crane and BSP CX110 NZ Crane Mounted Impact Hammer. Each pile was then cleaned out with the EK110 drill rig in Kelly mode. A positive hydrostatic pressure head was maintained within the pile casing during the excavation, to minimize the risk of flushing of base material around the pile or having material hydraulic up from within the pile casing. The excavated piles were cleaned with airlift. Moore Constructions ZX360 (35 ton) excavator was on site to assist with piling and maintain river diversion for the duration of the piling. Before starting works Moore Construction supplied the client with SSSP, ITP and GRLWEAP 14 assessment of drivability for the casing in the given ground conditions.

Moore Construction ensured an underwater camera was available on site for the duration of the project, along with equipment and chemicals for cleaning of the water (Airlift and Coagulant). This allowed for a visual inspection of the casing toe as it was advanced.

The river diversion entailed working within the resource consent, cutting a diversion channel down the south side on the riverbed. Installing sheet pile across the top side of the working platform and access road down to the riverbed. The Waimangaroa river is a very volatile river, to maintain our working platform needed constant management with use of a 35-ton excavator and dumper.

Reinforcing was supplied by Complete Reinforcing Ltd and transport to site was self-performed by Moore Construction. Cages where suppled in 11m lengths, spliced on site and lowered into each excavated casing. 75mm Heavy Duty Pile Cage wheels used and pile cage feet, to ensure side and bottom cover was maintained.

Concrete was wet tremie poured using a closed cell foam go-devil tremie separator. Moore Construction has a selection of tremie kits for a range of projects. Prior to concrete pour commencing the base of the pile was cleaned with a flat base cleaning bucket. Once all large debris has been removed, an air lift was used to lift fines and cuttings from the base of each pile. Flocculant was then added via an airline and a resting period provided, to allow settling of fine particles. A final air lift was then completed.

The Waimangaroa Bridge Piling project illustrates Moore Constructions ability to construct large diameter bored piles within a marine environment, meet tight contractual programmes, produce quality work and familiarity with local geological formations and soil conditions.