Project overview

Scope $250,000

Date of completion August 2019

This project entailed the fabrication and installation of deck and handrails to form a cycleway bridge for the Department of Conservation, Hokitika

Mahinapua Bridge Repairs

Additionally, it involved repairs to an existing historical rail bridge structure repurposed to a cycleway bridge.

The work was completed in stages as the client's funding became available. It included replacing pile sections (stump piles) and replacing entire piles, a challenging task given the bridge location over a large estuary. To complete this complex piling work, we developed a venturi suction system that hydro excavated the pile toe, advancing the piles and allowing for their successful installation.

In addition to the pile work, we repaired and replaced spilt transoms, A blocks, saddle blocks and wind braces. Corrosion protection of truss rods and preventative maintenance of the structure was undertaken by applying CNE, grouting holes in hardwoods to avoid water pooling and sheet metal capping on beam ends to slow the effects of weather. Access to this bridge required a unique approach due to its estuarine location. Lifting, supporting and propping work had to be man-portable and was carried out using chain blocks, winches and support frames. Our hiab with 25m of boom was also used to lift and lower beams and rods at either end. This minimised the use of helicopters. Rail beams and new transom beams were, however, flown into position using helicopters. The project is located in a nature reserve, so all work was planned and completed with environmental impact as a top priority. Machinery use was kept to a minimum to lessen the impact on the surrounding flora and avoid pugging the ground. Prefabrication meant there were minimal construction materials and debris on site.