Dam repairs are often high-risk, expensive, and should only be undertaken when the cause of failure and repair options are well understood.
Repairs should only be attempted on larger, well-constructed dams.
Understanding the dam’s history — who built it, what equipment was used, and how it has performed — is essential before any work begins.
Poor construction, unsuitable materials, inadequate compaction, and soil contamination are among the most common causes of dam failure.
While poor maintenance can contribute, it is rarely the primary factor.
Diagnosing the cause of dam failure can be complex. It is important to determine whether the leak is through the wall or floor of the dam, and whether it is isolated or widespread.
Thorough inspections should ideally be carried out across multiple seasons, including winter, spring and summer.
Where possible, landholders should:
- Inspect the dam bank for seepage, subsidence, cracks, or tunnels.
- Check the waterline for whirlpools or surface turbulence.
- Examine downstream areas for soft ground or lush vegetation, indicating seepage.
- Use a steel probe or crowbar to test soil firmness in suspect areas.
- Watch for unusual signs such as bright yellow or very clear water, which may indicate tunnelling or unsuitable soil.
- Monitor and photograph the site regularly to track changes in water levels or visible issues.
- Inspect the dam after heavy rain to identify potential problems.
- Carefully examine any breach in the dam wall, looking for signs of unsuitable materials like sand, gravel or topsoil.
Soil testing is a crucial part of any repair effort. Testing should include samples from the failure site and surrounding areas, as well as any potential borrow pits.
Basic soil assessments, including texture, aggregate stability, and shrinkage, can be undertaken by landholders using simple guidelines available on the Agriculture Victoria website at tinyurl.com/2wu3t9be
Repair options depend on the location, cause and severity of the failure.
Solutions may include reworking existing materials, sourcing suitable material nearby, or using additives like lime, gypsum, bentonite, or specialised products such as sealants or membranes.
Expert advice should always be sought before using manufactured products, as locally sourced materials are often more effective.
Dam repair works usually involve:
- Excavating the site for safe machinery access.
- Preparing the foundations to optimise bonding.
- Ensuring repair materials are moist and placed in layers not exceeding 100mm.
- Compacting each layer with multiple passes of a padfoot roller.
- Ensuring the total depth/width of repair materials exceed 300mm.
- Shaping final slopes to a maximum gradient of 3:1.
Repairing dams also present significant health and safety risks, including unstable soil, steep slopes, machinery hazards and exposure to dust.
All works should be carried out by qualified and experienced personnel, and safety protocols must be in place, including reliable emergency communication.
Permits or licences may be required to undertake dam repairs. Landholders are encouraged to contact their local council planning officer and water authority for guidance.
– Agriculture Victoria land management executive officer Clem Sturmfels.
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