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 Soakwells Perth | Stormwater Installation in Perth Street

by Jacques Davis - Perth Soakwells
Published 28th March 2016
Copyright 2019 - Perth Soakwells Pty Ltd

Perth Soakwells Pty Ltd installation of stormwater drainage soakwells in Perth roadway.

We are pleased to discuss the latest soakwell installation contracted to Perth Soakwells Pty Ltd for road stormwater drainage by the City of Joondalup for Sorrento, Western Australia. The below articles discusses the process from planning the soakwell installation, delivering the required stormwater materials to site as well the execution of the soakwell installation. This is a civil works project. We also provide residential soakwells installations, industrial soakwells & stormwater as well as soakwells for new homes in Perth, Western Australia.

Soakwells Perth | Scope of works for Civil and road drainage in Perth, Western Australia

The City of Joondalup requires three drainage points consisting of 4 soakwells. 
The points where stormwater drainage is required are marked below:

The original request arises from consistently identified drainage weak points in the Perth street way where the surrounding resident experience stormwater flooding. The stormwater flooding is due to the slope of the street and the lack of drainage points. The results are flooding of the residential homes which receive the bulk of undrained stormwater runoff. There have been consistent complaints of these issues and the City of Joondalup has approved drainage works to alleviate the problem. Our hope is that the installation will result in the complete diversion of stormwater so that the surrounding properties are no longer subjected to the additional runoff.
As a residential property owner, your property is charged with retaining stormwater on site through soakwells where the natural groundwater can be re-charged. However, with the streets being impermeable bitumen and asphalt, the water does not drain and rushes into the private properties, creating the excess stormwater runoff many times the expected volume of a simple residential dwelling.
The solution for this situation is the installation of stormwater drainage in the form of Soakwells, installed by Perth Soakwells Pty Ltd.

Soakwells Perth | Soakwell & Stormwater Preparation

This particular stormwater project requires a combination of concrete soakwell products, soils, cements and machinery.

Stormwater materials required:

Soakwell Lid - Trapped Road Gully or Smart Grate / D Class 

1050x900 Premium Concrete Soakwell - Watercorp approved concrete with base and weephole

1800x1800 Premium Concrete Soakwell - Watercorp approved concrete with base and weephole
[Untrapped Road Gully Detail]


Stormwater Safety management and soakwell traffic control

The soakwell project is based in two residental streets. Swinging a 6 tonne excavator around would not be traffic friendly, therefore precautionary management steps are put in place to ensure both vehicle and pedestrian traffic safety during the soakwells Perth installation.

Road base and Cement for Soakwell Perth Installation

Road base is delivered to the site to ensure that backfilling will be performed with soil that will compact well and not be susceptible to movement. The road base backfill is to be compacted every 300mm to ensure that air pockets and subsidence does not occur days, weeks, months or even years down the track. Perth Soakwells Pty Ltd ensures that soakwell installations are conducted according to specifications required by the City of Joondalup.
Cement is mixed with the top 500mm of soil to ensure a hardening once the first rains mix with the stormwater roadies beneath the new asphalt. This is an over and above precautionary measure to ensure the long term soundness of the stormwater system.

Stormwater Geotextile Fabric / Geofabric for Soakwells Perth

Many soakwell installations occur without geofabric. The long term effects are quite serious as the soakwell may leach sand back into the stormwater system. Ultimately this will cause subsidence in the street with dips or potholes forming. The fabric prevents any sand from entering the soakwell ensuring a sealed system with stormwater water acceptance and dispersion only.

Stormwater Piping

In the first stage of the stormwater drainage for the City of Joondalup, there are two soakwell tanks interconnected between the 1800x1800 soakwell and the 1050x900 soakwell with a smart grate. The piping is required to be 300mm in diameter.  We acquired 330mm piping with a 19mm thick wall. The weight bearing capacity is 1000kg directly applied. The stormwater pipe will however not be subject to any vehicle traffic, even though the capacity is well qualified for such and application.

Soakwells Perth Installation | Perth Soakwells Pty Ltd

Soakwell Excavation

Perth Soakwells arrives at 7am to prepare the site. We set up the excavator, bobcat and vehicles. Safety cones, pedestrian signs and traffic controls are set in place prior to the stormwater installation to ensure a safe and successful soakwell Perth process.
We first break through the street curb which allows us to position the excavation for the soakwell. Our first task is to safely excavate for the 1050x900 stormwater tank or 900x900 soakwell tank. This is the tank which will be exposed with a grated lid. The lid will need to be set at the slope and gradient of the street as well as the matching height to restore the asphalt upon completion.
We clear away the old road asphalt and commune excavation for the Soakwells. The digging presents a challenge as the soil appears to be hard due to the presence of limestone. We change to a tooth bucket to expedite digging and make efficient progress.

Soakwell Installation 

Once the hole is excavated to the right height, checked via laser level, we run a string line across the asphalt to measure the gradient of the sloping street. The stormwater needs to drain through the soakwell grate, hence the level and angle of the soakwell lid needs to be accurate within 5mm. 
Perth Soakwells lowers the concrete soakwell base which measures at 150mm thickness.  The base needs to be set at the level and angle that the lid needs. Once the base is factored in and the height works, Perth Soakwells lowers the soakwell body into the excavated hole.
Once the 1050x900 soakwell is on the soakwell base, we make provision for the 300mm stormwater pipe. The stormwater pipe extends into the second soakwell which is a 1800x1800 stormwater tank. This means the excavation needs to extend to the second soakwell. Therefore we commence soakwell excavation for the 1800x1800 in the same fashion. The soakwell hole is  dug open with the excavator and the base and soakwell are installed. The 300mm stormwater connection between the two soakwells is installed and filleted with concrete on the inside to ensure the system is free from surrounding silt and for future maintenance.
The soakwell lids are capped onto the soakwells and the lids are rotated to reflect the necessary direction required to be parallel to the street curb. The soakwells are in and set, ready for stabilisation, backfilling and compaction.

Backfilling and Compaction

The original soil excavated from the soakwell Perth holes is not suitable for backfilling due to the presence of rocks, pebbles and limestone. Therefore road base is used to back the majority of the city around the soakwell. With every 300mm layer, the road base is compacted with a vertical rammer or vertical jackhammer. This reduces any cavities in the sand and ensure stability around the soakwells, even during heavier rainfall where the soil will reach 100% saturation.

Stormwater Installation Finishing 

No job would be complete unless we clean up after ourselves ;)
Once the soakwells are backfilled and completed, the clean up process starts. Excess soil needs to be removed from the street and the area is swept up. Machines are loaded, materials and equipment packed up. Lastly we removed the safety signs for the streets where the soakwells are now installed.


We demonstrated clearly how soakwells are required in areas such as this in Perth where stormwater runoff which is not drained creates flooding issues for residential homeowners. 
Perth Soakwells Pty Ltd was contracted to install the soakwells for two streets in the City of Joondalup.

We explained in details the soakwell preparation required, the stormwater materials needed as well as the soakwell designs and specifications.
Finally we discussed how the soakwell site was excavated, levelled and compacted. We then explained how the soakwells Perth were installed and backfilled, then finally compacted with road base and cement mix.

If you require Soakwells Perth, contact Perth Soakwells Pty Ltd on +61411955921 or email us at
Perth Soakwells

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