Located in the South Island town of Geraldine, Coulter Place is a small, no-exit residential street that runs adjacent to State Highway 79. At the end of the street, a footpath connects Coulter Place to SH79, forming the lower side of a small, tree-lined park, bordered by another residential road on the upper side. When the concrete slab wall supporting the slope along the pathway began to fail, residents had limited walking access to their homes and pedestrians were forced to cross the busy highway to use the footpath on the other side of the road.
At the time, Timaru District Council were looking for a robust retaining wall solution on a range of projects around the region. They liked the look of MagnumStone as it offered a variety of design solutions, while other options, such as a timber piled wall, would have meant much greater traffic management and interruption, as well as the use of large machinery and clearing of debris.
DESIGN
Running along the upper side of the new pavement, this 107m MagnumStone gravity wall was designed to support the gentle slope as it rose toward MacDonald Street. As there were no loadings to consider, a smaller wall was designed. Ranging from 0.6m up to 1.8m, the lower layer of blocks was embedded into the bank, with MagnumStone’s short extenders to be placed along the entire length of the embedded layer. At 650kg each, the top two MagnumStone layers would simply rest on top of each other. The wall would also have a slight return at the sharp corner entering MacDonald Street from SH79.
INSTALLATION
Because MagnumStone can be placed in such a tight space, there was minimal excavation required. Once a at platform was created, the embedded layer with extenders was placed using a small excavator, causing minimal diversion for traffic along the main road. This was also helpful to avoid nearby power lines. With access into the site coming from the end of Coulter Place, contractors were easily able to excavate, place the blocks and extenders and refill the site using layers of drainage aggregate wrapped in geotextile and existing site material, with the entire slope covered in BioCoir for further vegetation.
Owing to MagnumStone’s versatility and aesthetics, Timaru District Council were able to quickly build an attractive, robust retaining wall without disrupting business traffic heading into town. Local residents now have easy access to their homes, with safe pedestrian access leading into town.
The MagnumStone system used provided the following benefits to the project:
- Can be installed using minimal crew
- Can be installed without using heavy machinery
- Causes limited interruption to traffic when placed within tight spaces
