Describing a soakwell Installation in Perth, Western Australia
Describing a Soakwell Installation Outline
The initial requirements
The recommended soakwell configuration
Preparation of Soakwell Materials
Preparing the site for soakwell installation
Excavating for soakwells
Laying stormwater pipework
Layered Compaction of Soakwells
Tidying up the site
Roy and I have been installing soakwells for close to two decades. We have accumulated a wealth of expertise over time, dealing with a broad range of stormwater requests, problems and solutions.
In this case, a property was being renovated and we were called in to inspect the site, assess its stormwater requirements and propose a suitable configuration for stormwater runoff. As expected, the best solution would be soakwells to contain the stormwater on site as per council requirements.
But why soakwells?
Soakwells are the best way to drain stormwater away during heavy storms while avoid erosion and damage to your property. Homes without soakwells are tend to have building movements over time, causing cracks throughout the buidling. A far more apparent and tangible consequence of not having soakwells is flooding which can occur if stormwater runnoff builds up around your property. This is especially exacerbated when a property has impermeable areas such as paving, concrete and artificial turf.
The Initial Requirements for Stormwater Disposal
As per photo below, the property located in a coastal Perth suburb, at the rear is downward sloping ( a decline). The client intends on level the entire backyard out in line with the concrete fence posts. This would provide function land at the rear, allow a shed to be built and allow a driveway to head further into the yard. However, as most of this would be concreted, it would also require stormwater drainage. Without proper drainage, the stormwater would clearly run down into the rear neighbour's yard.
Recommended Soakwell Soakwell Configuration
Given that the total area to be drain is around 180 square meters, the council recommendation would be 2000 litres of soakwell capacity in sandy soil. We stipulate sandy soil because clay or rocky soils impede the rate of drainage and would require a larger soakwell capacity.
We recommended the polypropylene soakwell option to the client for ease of installation, the higher rate of drainage compared to concrete soakwells and for being the most cost-effective solution while lasting as long as concrete soakwells.
The soakwells were recommended to be locate at the front and rear of the property to split the front and rear parts of the roof into separate patches of soil which would assist rainwater drainage through the soakwell system.
Written by Jac Davis - Author and Soakwell Veteran - 7th Decemebr 2022
Preparation of Soakwell Materials
Polypropylene soakwell tanks were assembled equating to 2000 litres of drainage.
Fabric was cut and prepared to prevent and soil and sand from entering the system. Our geofabric is a non-woven geotextile which does not degrade over time.
10 lengths of 6 metre Heavy duty stormwater pipes were allocated to the jobs, together with necessary 90mm fittings such as T-Pieces, 90 degree elbows and stormwater grills.
Preparing the Site for Soakwell Installation
Secondly the gates were removed from their hingers in order to allow our excavator to access the property.
Thirdly, all safety signs and cones were placed in visible areas to ensure that any pedestrians and site visitors would be made aware of our presence, excavation and potential hazards.
Excavating for Soakwells
Excavation commenced with two excavators. One being a 2 tonne excavator, another one which I operate being the 1 tonne excavator. As the 1 tonne excavator has a width of only 700mm, it can access narrow passages and access the rear of the property as was the case here.
When digging a hole for soakwells, considerable care must given to the location of underground services, known and unknown. Breaking pipes and cables not only causes a great inconvenience to the customer, but can be hazardous and even fatal to us. This is especially the case with gas pipes and power lines. With the larger excavators we are especially cautious around power poles and overhead powerlines.
Another factor affecting soakwell excavation is the type of soil. If the soil is firm then excavation is efficient and holes remain in the shape they are dug.
In very fine grain soils, more akin to beach sand, the soil just caves in and the walls of the soakwell hole repeatedly collapses. This can prolong the digging process by hours.
Digging Trenches for Stormwater Piping
Digging trenches for stormwater pipes can sometimes be done with an excavator, however in narrow passages it must be done manually to avoid breaking sewer and services.
Trenches are dug from the downpipes to the soakwells. The preferred pattern is digging right angles for ease of connection the trench. Once the trench is a sufficient depth, the stormwater pipes are placed in the trenches, ensuring there is a gradient fall towards the soakwell that is sufficient to cope with a heavy stormwater downpour.
Laying Stormwater Piping
Once the trench is a sufficient depth, the stormwater pipes are placed in the trenches, ensuring there is a gradient fall towards the soakwell that is sufficient to cope with a heavy stormwater downpour.
Suitable 90mm fittings are used to couple pipe pieces together. Our preference is to use offset stormwater grates below the downpipes to prevent flowback into the eaves.
Layered Compaction of Soakwells
Once the soakwells are installed and the piping is complete, we commence the process of backfilling and layered compaction.
If we were to backfill soil over the soakwells without compacting, dips and soil subsidence would occur over time, especially during rainfall. Layered compaction from Perth Soakwells , our team, helps to prevent soil subsidence especially when paving, lawn and artificial turd are used as groundcover.
Tidying Up the Site after Soakwell Installation
After soakwells are installed, pipes are laid and connected, soil compaction and backfill, tidying up commences.
We first tidy and flatten soil with the excavator if possible, flattening out excavated soil unless it's removed from site.
Then for areas that the excavator cannot reach, we use flat head shovels to flatten out the area.
Finally, we use brooms to sweep down the property, paving and driveways to ensure that the customer is happy with the final outcome.
We have demonstrated and discussed in this article, the process of installing soawells in Perth Western Australia. We explain how the initial consult allowed us to determine the stormwater issue. We then explain the reason for our soakwell recommendations.
We continued by explaining the preparation required on site prior to installation.
Finally we discussed the actual installation process of excavation, installation, piping and compaction.
If you require assistance with stormwater and soakwells, please visit us at www.soakwells.com