Addressing Sheet Pile Accelerated Low Water Corrosion on Ohau Diversion Wall

Paper No. 125
R El Sarraf1, W L Mandeno & M Townsend3, Opus International Consultant Ltd1, Aduckland, New Zealand, Opus International Consultants Ltd2,Wellington, New Zealand & Mark Townsend, Bay of Plenty Regional Council3, Rotorua, New Zealand

Abstract

Ohau Diversion Wall is a 1.2km long submerged wall consisting of interlocking sheet piles, and king piles up to 50m into the bed of Lake Rotoiti; that is currently undergoing accelerated low water corrosion due to microbial induced corrosion, after only 10 years of service. Concerns were raised about the continued performance of the wall, and whether it will last the remaining 40 years of its design life. Opus International Consultants, were commissioned by the Bay of Plenty Regional Council to investigate this and develop alternative remediation solutions.

This paper presents the findings of this project to date, and a comparison between the alternative remediation solutions. These included the use of cathodic protection (sacrificial or impressed current), the use of protective coatings, patch repair, and full replacement using vinyl sheet piles or impermeable polymeric screens. An environmental review of the effects of each option, and development of mitigation measures will also be presented. The paper concludes with a net present value cost analysis between the different options, which assisted in determining a preferred solution.