HOW ENVIROCON AND INTERBLOC DELIVERED A CENTURY-LONG SOLUTION FOR A CHRISTCHURCH CITY COUNCIL STORMWATER PROJECT
Open waterway channels are a part of Christchurch's stormwater network. When a section of waterway lining on Hills Road required renewal, the design called for single-sided bank stability along a Christchurch City Council open stormwater drain — and Interbloc® proved to be exactly the right fit.
THE CHALLENGE: SINGLE-SIDED, RESTRICTED ACCESS
Waterway lining in Christchurch typically follows a double-sided approach — timber walls on each bank, braced against each other with top and bottom struts. On this project, only one side of the channel required renewal. Without an opposing wall to brace against, a single-sided timber wall would have demanded piles at significant depth to remain stable.
That depth created a practical problem. The waterway runs through established residential land, with homes built near the bank. The heavy plant required to drive deep piles simply could not be accommodated within the available space. Interbloc was specified by Council as the solution: a gravity block wall that could be installed without tie-back sheets or deep piles, using equipment suited to constrained residential sites.
“Interbloc+ offered a 100-year design life”
- Council
WHY INTERBLOC+ CROATIA?
Interbloc’s 100-year design life means the infrastructure installed today serves the next generation without requiring contractors to re-enter private land ahead of schedule.
As a gravity wall system, Interbloc® relies on the mass of its 600mm-deep solid wet cast concrete blocks to resist lateral loads. In some soils and for specific wall heights, a mechanically stabilised earth configuration is not needed, which reduces the excavation behind the wall face. The system's unique interlocking shear key transfers forces between blocks and ensures stability.
Installation is rapid. Interbloc®'s self-aligning, Lego-style block design meaning this 20m section of wall could be built within two days — a meaningful advantage when working within the constraints of a live residential environment.
INTERBLOC CROATIA: STRENGTH WITH A REFINED FINISH
This project specified Interbloc® in the Croatia finish — a sleek, modern texture that brings visual refinement to infrastructure without compromising structural performance. Croatia is the right choice wherever a wall will be seen by the public: clean in appearance, durable over time, and consistent in finish across the full block range.
Croatia blocks are available across every Interbloc® block type — giving designers full flexibility to handle straight runs, curves, corners, and transitions within a single cohesive aesthetic. The Croatia finish retains its character for the full 100-year design life.
For waterway infrastructure that passes through public space — alongside bridges, paths, and roads — Croatia delivers a wall that will look as considered in decades as it does on day one.
A GROWING APPLICATION
Waterway lining is an emerging application for Interbloc®, and the Hills Road project has demonstrated the system's suitability for this context. Gravity block construction created a single sided waterway lining solution which is generally constructable in constrained urban environments, and the 100-year design life aligns directly with the long-term thinking that asset owners and councils increasingly demand from their infrastructure partners.
Envirocon® continues to work with engineers and contractors to develop configurations optimised for waterway conditions. As Christchurch's waterway network continues to be renewed and upgraded, Interbloc® Croatia is another option to maintain this important stormwater infrastructure.
