Innovations on the Himatangi Beach Community Sewerage Scheme

Himatangi Beach is a small settlement on the Manawatu coast, with a mix of permanent residents and holiday homes. The Himatangi Beach Community Sewerage Scheme (HBCSS) is a project to provide a low pressure sewerage reticulation and centralised wastewater treatment plant to replace on-lot private septic tanks with ground discharge. Like other low pressure sewerage schemes, capital and operating cost were vital to the project being accepted by the community.

Recognising this, the client incentivised connection to the voluntary scheme for residents, and sought innovation through the tender process. The project was awarded as a Design and Build contract, with several key innovations which delivered approximately 15% in capital cost savings. These innovations included sharing a single pump station unit (PSU) between two properties where possible, and to provide the electrical connection from overhead power lines in the street frontage, instead of connecting to the house switchboard. 

This paper details the collaborative design approach undertaken for the HBCSS pressure sewerage system, including constructability and operability reviews. It also discusses including the innovative use of dynamic modeling to develop the design.