On a Manukau multi-unit site where shallow drainage invert levels ruled out deep tanks, APD StormSlab® delivered 46m³ of detention using two 300mm deep tanks per lot, certified as standard for 10-tonne driveway loading.
GJ Gardner Manukau required a 46m³ stormwater detention and retention system for a multi-unit residential development. On-site testing revealed extremely shallow drainage invert levels, ruling out traditional deep underground tanks because there was no gravity fall to work with. Spatial constraints also ruled out an above-ground alternative.
The shared access way layout added a second requirement: a subsurface system that could carry medium vehicle traffic across the driveway zones. The development needed underground pumps as well, to keep operational noise away from neighbouring properties, ideally without the footprint of dual distribution chambers.
Alternative tank systems were considered for the project. One could not work with the shallow connection levels on site. Another could not certify the 10-tonne load the shared access way required without moving to a custom solution. StormSlab® could meet both the shallow profile and the loading, which is why it was selected.
The deciding factor was the access way loading. APD’s PS1 covered the 10-tonne load the shared access way required, so the trafficable zones were certified without any custom engineering. That, paired with the shallow tank profile, let one system run across the whole site.
| Attribute | Specification |
|---|---|
| System type | StormSlab® Tank System |
| Application | Stormwater detention and retention |
| Total capacity | 46m³ across the development |
| Tank dimensions | 300mm H x 4,700mm L |
| Capacity per tank | 1,435 litres |
| Tanks per house lot | Two |
| Load rating | 10-tonne traffic load (covered by project PS1) |
| Pump configuration | Single-chamber integrated submersible pump |
| Bowers & Son | Concrete |
Specifying two 300mm deep StormSlab® tanks per house lot kept the excavation shallow and the volume covered. Each lot was excavated, installed and backfilled within an hour and a half, managed by the project manager on site to fit a tight construction timetable.
The same system worked across the access way, driveway and garden zones on the one site. The PS1 covering the 10-tonne loading gave the development the capacity it needed where it mattered, and the single-chamber pump kept operational noise away from neighbouring units. GJ Gardner reported a great result that met all the client’s requirements.
A high council connection point and a trafficable access way are the kind of constraints that force a redesign or rule out density. Here they did not. The site was built as planned.
Finding the perfect section of land in Auckland isn’t easy but APD’s DnP solution was able to help this family build their dream home on a not so perfect plot. A pumping station was needed on a property situated down a steep driveway in Blockhouse Bay. It needed to be able to capture and remove up to 1,200L of waste water but gravity posed an issue.
We were asked to provide a tank that could capture up to 1,200L of waste water from the house and pump it up hill to join with the council system located at road height. APD had worked with Max Plumbing before so they already knew we had the perfect solution.
The DnP waste water pump – an underground tank and pump that would provide everything required. The reasons they chose this solution were:
DnP is made of PE which has a longer lifespan than concrete solutions
Right from the beginning our team listens to your needs and requirements before building the tank to order. By the time it gets to site it is ready to into the ground and connect up to the properties waste water system. Leading to a straight forward, time saving installation without messy concrete or complicated instructions. Don’t worry if you do get stuck though, our helpful team are available to support you if you need it.
Meaning that they were able to build their dream home on a peace of land that otherwise would have struggled to support the plumbing requirements of a family home.
APD StormLite® Detention and Retention tanks can be installed under house or decks where space permits. Key requirements for this type of installation are for the tanks to not undermine any of the structural support of the building or for the tanks to be placed anywhere that a surcharge load can be applied to them by the building structure.
If the tanks are not to be completely buried then the minimum burial depth for the tanks is half the height of the cylindrical tank diameter. The tank shown in these images is a 1000mm diameter tank and it has been buried to a height of 500mm from the tank invert.
This small site where the 4 Block NZ villas stand, rests at the foot of Mount Albert. When the engineers determined that the site coverage of the villas would require detaining 15,200L of storm water they knew they couldn’t dig down and they didn’t have space for above ground tanks.
We calculated that the most suitable and cost effective solution would be to position 2x 2,000L Stormlite® tanks* under villas 1,2 & 4 and to place two slightly smaller tanks under villa number 3 (which had the greatest space restrictions in the foundation layout). Concrete beds would form the base for the tanks to rest on and special PE strips were used to position the tanks without scraping or damage. Access hatches to the Stormlite® tanks were included in the deck designs to allow for straightforward maintenance while the tanks remained discretely out of sight, as seen in the final photo on the right. *The choice to split into two tanks was to work within spaces between the foundation piles.
Meaning that the block builders could have peace of mind and focus on everything else they needed to deliver.
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