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Canal Wall Failure – A Growing Concern

Canal Wall Failure – A Growing Concern

by November 7, 2015 0 comments

It is Your Legal Obligation. Owners of waterfront properties are legally responsible for the care and maintenance of their own canal walls. This change of law in the majority of local councils has been in place for several years. Despite this, most owners are unaware of this obligation and the requirement by law to ensure their wall is serviceable.

Since 2013, buyers and sellers of waterfront property on the Gold Coast have been subject to Local Law 17. Under this law, a contract of sale involving any property that has ‘prescribed work’, such as a revetment wall, jetty or pontoon, must have a particular clause that includes a disclosure obligation specifying certain matters about the operation of the Local Law. If the contract does not contain such clause, the buyer may be able to terminate the contract and obtain a refund. Further, the Local Law requires the responsible person for the specified prescribed work to maintain and keep the specified prescribed work in a safe condition, and of good working order, repair and condition. A responsible person includes a person who owns the property on which a prescribed work is located or who receives the benefit of the prescribed work.

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What’s the Big Deal?

When walls fail, the expense in removing and replacing them can hit the pocket hard. Sadly, unsuspecting owners can wake up to a fallen wall and wonder how this could even happen, being completely blindsided to the potential financial burden they have now placed themselves under.

All walls age and deteriorate. With maintenance and repair, the wall’s life can be extended and kept viable for many years.

The symptoms and signs of wall failure and wall aging are clear. Know the symptoms, monitor the wall and save yourself the heartache.

Signs and Symptoms

Greg Sweetman, owner of Gold Coast Barges says, ‘Firstly, the wall owner needs to regularly attend to visual inspections and act quickly when changes are evident. Cracking, widening of cracks and subsidence on your property behind the wall are signs of problems arising. If caught early, walls can be corrected. Preventative maintenance is key in canal wall health.’

Exposed Toe: When a wall is built, it is engineered to withstand tide and flood. The base of the wall is engineered to be covered and supported. Over time the toe of the wall can be uncovered and this can destabilise the wall, causing leaning and twisting. This causes cracks to occur, and the wall may slump and eventually will fall over.

Concrete spalling or concrete cancer occurs when saltwater causes corrosion of the steel reinforcing inside the wall. Sometimes this is due to poor construction—where the steel was too close to the surface—and the steel has been affected early by the salt being absorbed into the concrete. Sometimes, it occurs when saltwater penetrates through hairline cracks in the concrete. As the steel corrodes, it expands and causes the surrounding concrete to crack. In bad cases, the concrete falls away further exposing the steel and exacerbating the problem. This can be corrected if detected early.

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Deterioration of Construction Joints: Revetment walls are built with construction joints to allow them to expand and shrink with temperature changes. Usually, these joints are sealed with a rubber material to prevent water and soil from being lost through them. Over time, the rubber deteriorates, especially below the high tide line. (Crabs seem to love it!) When the rubber deteriorates, sand and soil can be lost through the joint causing subsidence behind the wall.

Blocked and Failing Weepholes: Weepholes are designed to allow water to flow from behind the wall relieving pressure. Over time, these block and prevent water from escaping putting pressure on the wall from behind. Ongoing maintenance of weepholes is required for the wall to remain healthy. Weepholes should have a geotextile fabric (geofabric) behind them which allows water through, but prevents washing out of the sand and soil. Many walls have been poorly built without this protective feature. Also, early forms of geotextile fabric had a limited lifespan particularly in the marine environment. In many cases, the fabric has deteriorated and is now letting soil through. Crabs also love tearing the old geofabric out so they can dig a home behind the weephole. This is an issue which requires regular maintenance and vigilance.

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PHOTO: The geofilter behind the wall has failed allowing the material from behind the wall (sand and gravel) to escape through the weephole. Over time this will cause subsidence.

Subsidence: When material is lost from behind the wall, subsidence occurs. This is very obvious when grass slumps, fences become uneven, concrete and paving become uneven or crack. The concrete pathway behind your wall may be concealing a very big problem. Pools and retaining walls on your property close to the revetment wall may crack or move long before the revetment wall fails. Subsidence is a wakeup call for owners of canal walls. The wall is no longer adequately protecting the property.

Healthy Wall or Sick Wall? Call The Doctor!

Gold Coast Barges rectify walls before they fail. There are several solutions and they ensure you get the right advice and the professional service you require.

Recognising the need for a team dedicated to ensuring the health of canal walls in South East Queensland, Gold Coast Barges have deployed, ‘The Canal Wall Doctor’. This team specifically target the maintenance and ongoing checking of canal wall health.

Greg Sweetman says, ‘We can take the worry out of canal wall ownership. Our annual inspections provide a report that gives the property owner an understanding of the arising issues and the steps to correct before it is too late. With scheduled annual inspections and maintenance, owners can rest easy knowing their walls are being checked and maintained. The pairing of The Canal Wall Doctor and Gold Coast Barges gives the canal wall owner a comprehensive care package. Gold Coast Barges provide the support when the wall needs ‘intensive care’ to sort the big issues and the Canal Wall Doctor attends to the maintenance and health check-up every year to ensure your wall, though aging is monitored, maintained and functional.”

Gold Coast Barges will protect your wall with qualified inspections, reports, repairs and maintenance. Ph: 0427949163 www.canalwalldoctor.com.au

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