Napier City Council



Contract Type

Construct only


Aug 2013



Napier WWTP Concrete Structure Coating

The harsh environment in waste water treatment plants can cause significant damage to internal concrete structures over time. Napier City Council engaged Pipeworks to coat and line tanks and concrete structures in its Awatoto Wastewater Treatment Plant to protect them from Hydrogen Sulphide and other corrosive gases. 

Pipeworks used a two-stage rehabilitation process to protect the wet wells, effluent channels and grit channels, chambers and outlet channels.  First a layer of fibreglass was glued and bonded to the existing concrete surface. Then a chemical resistant epoxy Novolac lining system was applied to provide a smooth and durable finish.

The rehabilitation works will extend the life of the waste water treatment plant by at least 50 years.

Unique Aspects
  • Works in wet wells and effluent channels required careful planning and special equipment due to the confined space. 
  • The epoxy liner and fibreglass sheets were applied from a scaffold, and entry to the chambers was via a small 800mm x 800m opening.
  • Following completion of the works, the coated areas were tested using high voltage “Holiday Testing” to detect pinholes and other minor defects.
  • The epoxy liner was applied in most areas with a spray gun; where a thicker application was required, a trowel was used.


Project Partners

Name Napier City Council

Role Engineer