Reporoa Organics Processing Facility - Ecogas

The Project  

The Ecogas Reporoa Organics Processing Facility is New Zealand's first large-scale food waste-to-bioenergy facility. The 2-hectare site comprises large and heavy digester tanks, processing building with office block and gas upgrading facility. The extensive development, tight operational deadlines and geologically young and challenging soils created a high pressure and complex project.

Check out the project website here: Reporoa Organics Processing Facility — Ecogas

Our Role

Pioneer Energy engaged us to deliver a consent-ready geotechnical package. Our detailed site investigation and assessment identified challenging ground conditions, including a high risk of liquefaction in the upper sand layers and significant settlement within a thick peat layer interbedded with pumice-rich volcanic soils. To improve accuracy, we calibrated the liquefaction assessment to reflect the behaviour of pumiceous soils, which otherwise led to an overestimation of vertical settlements. The site layout was then modelled in 3D software to evaluate group effects from the widespread, heavy loading and to predict both the magnitude and duration of settlement.

Our assessment predicted up to 250 mm of settlement over 2 years could occur within the peat layer that was located at 15 to 20 m below the ground level.

The Solution

After working with our client and project partners, the final solution involved the design and verification of 21-metre deep driven timber piles below an embankment reinforced with high tensile geotextiles. This solution provided long-term stability while remaining cost-effective and practical to construct. During the trial filling of the tanks, settlement was completely uniform and within the structural tolerances, confirming the system was working as intended.

By leveraging our geotechnical expertise and smart thinking, we helped ensure the successful delivery of a key piece of infrastructure supporting New Zealand’s sustainable waste solutions.