Hi,All
I'm in the process to look for a suitable site for duplex development. However, after some discussion with builders and a little bit exploration of council's policies, I get some concerns over the stormwater drainage.
The following is the general requirements of stormwater drainage for a new development.
"If the site for the proposed development is located on the low side of the road, and it is impossible to drain the stormwater from the proposed site by gravity (minimum 1% grade in pipes) to the kerb and gutter, gully pit or Council pipeline located in the road at the front of the site, then the owner must obtain a 1.0m wide stormwater easement through the property at the rear/downstream to allow all stormwater to drain by gravity to the kerb and gutter in the street at the rear/downstream of site."
In the worst case, if a drainage easement cannot be achieved for a low-side property, councils may allow some alternative methods such as on-site absorption system, but they will then impose some limitations to the new development (such as a maximum 35% site coverage, etc). This may not be a big problem for a single dwelling but may be trouble for duplex development which generally has larger roof area and hard surface area.
Therefore, is it better to avoid low-side properties when looking for a possible duplex development site (especially no drainage easement can be achieved)?
Comments or advises are welcome:)
Hi,
The stormwater drain is not always always found at the roadside of the property. It often runs across the rear of the block in an easement (which presents its own problems when building).
Im not sure how you would go getting permission from the rear owner to run a line through their property. But i guess you could negotiate a compensation fee.
Another option is to fit an underground tank and pump system to get the water up to street level. Can be costly though as it needs to be failsafe to prevent the units being flooded out.
Pumpout systems are pretty standard (it is much harder to get one or more of the neighbours to agree to an easement on their land, excavation/reinstatement etc).
Fail safe just means that there are 2 pumps located in a pit at the lowest point of the development. Most plumbers are cluey enough to work out and provide the details (or use an hydraulic engineer when submitting the plans to be on the safe side).
If you are really clued up, you may be able to find a site with stormwater pit in the street which council/water authority may allow you to hook into below street level.
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