The Eastern Interceptor is a large diameter reinforced concrete cast in-situ pipe following a 19km long path from Orakei to the Mangere wastewater treatment plant. It delivers two thirds of the total wastewater flow
processed by the Manukau Wastewater Treatment Plant. The interceptor was constructed between 1957 and 1962 using a combination of conventional tunnel, and cut and cover techniques. WaterCare Services
carried out detailed investigations into the condition of the pipe and established that some sections had been significantly affected by biogenic corrosion of the concrete. In some sections, the concrete has been
degraded to depths of up to 90mm, significantly reducing the durability and performance of the sewer at these locations. Critical sections were identified and repairs were undertaken where the biogenic corrosion
of the concrete had extended to the depth of the reinforcing steel. AVS provided fresh air and extracted toxic gases during this rehabilitation.