Project Summary
Canberra Water, Gas & Air completed a large subsoil drainage installation and rainwater harvesting project at a residential property in Farrer, ACT.
The project involved working in extremely tight access conditions along the side of the home to resolve ongoing water ingress, protect the property from groundwater and install a 5,000-litre rainwater harvesting system for garden irrigation.
The Problem
The customer was experiencing flooding and water ingress beneath the home, with water flowing through the downstairs workshop. This was causing mould growth, along with minor cracking and movement within the house.
The property was built on a sloping block, with very limited access between the home and the boundary. Water was travelling through the site cut created during the original construction of the house and surfacing at the lower end of the property.
The Solution
We attended the property with CCTV diagnostic equipment and carried out a detailed inspection beneath the home. We crawled through the accessible areas to trace where the water was coming from and understand how it was moving through the property.
The investigation confirmed that the issue was caused by subsoil water travelling from the front corner of the property along the full length of the house before surfacing near the lower end and flowing into the downstairs workshop.
We also inspected the existing stormwater drains and confirmed they were flowing correctly. A small section of stormwater drainage was exposed, and roots that were partially restricting the system were removed.
After discussing the customer’s concerns, the history of the property and their plans for the garden, we designed a complete drainage solution. The customer had lived in the home for more than 40 years and was also an avid gardener, so we incorporated a rainwater harvesting system to collect water for the gardens and lawn.
As the sewer line ran along the same side of the property and was still made from ageing clay pipe, we also recommended replacing it while the area was open and accessible.
Works Carried Out
Before work commenced, the required “Dial Before You Dig” paperwork and approvals were lodged.
The works included:
- Temporarily removing the front fence and ducted gas heater to improve access and protect the equipment during excavation.
- Installing protection barriers around the pergola, solar battery system and multiple air-conditioning units.
- Levelling and preparing a solid base for the new rainwater tank.
- Delivering and manoeuvring the 5,000-litre tank into position at the rear of the property.
- Excavating a trench approximately 25 metres long and 1 metre deep using a combination of hand and machine excavation.
- Replacing the existing clay sewer pipe with new PVC pipework. This work took approximately five hours, with the customer using another toilet during the connection process.
- Sealing pipe penetrations through the house footings with concrete to prevent subsoil water tracking beneath the home.
- Installing construction plastic throughout the work area and trench.
- Installing a large sump pit connected to the existing stormwater drainage.
- Installing a sleeved subsoil ag pipe at the base of the trench.
- Installing new stormwater drainage and PVC downpipes along the side of the property.
- Connecting the stormwater system to the new rainwater tank, including an above-ground first-flush diverter and wire-mesh leaf strainer.
- Connecting the rainwater tank overflow to the new sump.
- Installing geotextile fabric to filter the subsoil water.
- Backfilling the trench with approximately eight tonnes of 30 mm washed river pebbles, moved through the tight access area by wheelbarrow and buckets.
- Installing a second layer of geotextile fabric before completing the final layer of washed river pebbles.
- Removing the protection barriers, reinstating the front fence and cleaning the entire worksite.
- Reinstalling the ducted gas heater and servicing it as a complimentary thank-you to the customer.
Outcome
The project was completed over a two-week period despite the very limited access along the side of the property.
Around four months after completion, following a period of heavy rain, we called past the property to check how the new subsoil drainage system was performing. The customer confirmed that not a trickle of water had entered the downstairs workshop.
The project delivered a lasting drainage solution, improved protection for the home and a new rainwater harvesting system to support the customer’s gardens and lawn.
The customer was a pleasure to work with, and the project delivered a quality result and a fantastic outcome.
