Why dam repairs often fail is a critical question for East Gippsland farmers currently looking to secure their water storage capacity.
According to Agriculture Victoria land management extension officer Clem Sturmfels, dam repairs are often high-risk and expensive, and they should only be undertaken when the cause of the failure and the repair options are thoroughly understood.
Mr Sturmfels advises that repairs should only be attempted on larger, well-constructed dams. Understanding the dam’s history, including who built it, what equipment was used, and how it has performed over time, is essential before any work begins on the property.
Poor construction, unsuitable materials, inadequate compaction, and soil contamination are among the most common causes of dam failure. While poor maintenance can contribute to the issue, it is rarely the primary factor. Diagnosing the exact cause can be complex, requiring landholders to determine whether the leak is through the wall or the floor, and whether it is isolated or widespread. Thorough inspections should ideally be carried out across winter,
spring, and summer.
Where possible, landholders should inspect the dam bank for seepage, subsidence, cracks, or tunnels, and check the waterline for whirlpools or surface turbulence. Examining downstream areas for soft ground or lush vegetation can also indicate seepage. Landholders can use a steel probe or crowbar to test soil firmness in suspect areas, and watch for unusual signs such as bright yellow or very clear water, which may indicate tunnelling or unsuitable soil. Monitoring and photographing the site regularly will track changes in water levels, and careful examinations should be made of any breach in the dam wall for signs of unsuitable materials like sand, gravel, or topsoil.
Soil testing is a crucial part of any repair effort, and samples should be taken from the failure site, surrounding areas, and 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.
Repair options depend heavily 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, and ensuring repair materials are moist and placed in layers not exceeding 100 millimetres. Each layer must be compacted with multiple passes of a padfoot roller, ensuring the total depth and width of repair materials exceed 300 millimetres, with final slopes shaped to a maximum gradient of 3:1.
Repairing dams also presents 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 with safety protocols and reliable emergency communication in place. Permits or licences may also be required, and landholders are encouraged to contact their local council planning officer and regional water authority for guidance before commencing works.
