Following a review of plants’ Resource Consent, an upgrade to the treatment process was needed, primarily to ensure a higher level of disinfection.

LDE provided geotechnical investigation, earthworks design and specifications for a proposed biofiltration plant located within the existing Wastewater Treatment Ponds.  These comprised 3 oxidation ponds and a small adjacent wetland.  The determination of differential settlement was a critical component of this work.

The geotechnical investigation aimed to identify a suitable site for various sized above-ground tanks.  These required an allowable bearing capacity, negligible settlement, and a 4m surrounding buffer for vehicle access.  One of the ponds also required partial infilling as it took up almost most of the proposed subject site.

The earthworks design and specification were for the placement of engineered fill at the site to create a bund across the existing maturation pond, thereby forming a smaller emergency storage pond and creating an area for the filter system.  

The works were part of a wider upgrade to the treatment plant and required considerations for potential significant settlement and differential settlement which were addressed in our design. 

Our specifications were site-specific, including the proposed methodology and fill material. 

Location: Kāeo, Northland
Client: Far North District Council