“In collaboration with a Geotechnical Engineer, BeneTerra has developed standard repair procedures for different types of defects likely to be encountered on dams such as capping defects, erosion features & HDPE liner defects”
Dams present a potential risk to downstream residents and properties. By law, they must be maintained to mitigate the risk of a breach . The embankments of earthen dams built in Central Queensland are often constructed with dispersive subsoil which makes them especially susceptible to rill and tunnel erosion. Establishment and maintenance of healthy grass cover and intact HDPE liners are key to successful, long-term operation.
The BeneTerra team provided annual dam maintenance services to maintain the integrity of these assets for coal seam gas operators in the Bowen Basin. The team employed skills in project management, civil engineering, bulk earthworks, soil science, agronomy and HDPE welding. In collaboration with a geotechnical engineer, BeneTerra has developed standard repair procedures for different types of defects likely to be encountered on dams such as capping defects, erosion features and HDPE liner defects. This ensures the quality of the repairs undertaken is controlled by standards set out by the certifying engineer.
These turkey’s nest dams or ponds had been in service for about 10 years and had been fairly well maintained. Yet, there were tears in the HDPE liners, sinkholes and rill erosion in the embankments.
The process began with an inspection by a geotechnical engineer and a site supervisor. They walked each dam and made a detailed assessment of any defects or needed improvements. These were geolocated and marked as needed. The project manager created a proposed scope of work and submitted that to the client for approval. Once the approval was given, the team commenced that campaign in November 2022. The works were completed in 42 days and then inspected by an independent geotechnical engineer who certified that the works completed met the original dam design intent.
The work consisted of:
- Slashing or mowing the vegetated downstream embankments
- Application of fertiliser to the vegetated downstream embankments
- Remediation of 22 sinkholes
- Repair of erosion along anchor trenches
- Repair of erosion on the upstream embankment (inside) of an unlined dam
- Installing rub sheets beneath inlet pipes to protect HDPE liners
- 84 HDPE liner repairs using fusion and extrusion welding
- Marking of the design storage allowance and mandatory report levels
- Replacing fauna egress devices
- Repairing dam compound fencing
- Replacing damaged or deteriorated life rings
- Soil amendment, seeding and application of an erosion prevention polymer to disturbed areas
