Construction of Reject Dam 2 (RD2) Stage 2 and 3, Cameby Downs Mine

Exact Civil Construction were engaged by Yancoal Australia Ltd (Yancoal) to construct Reject Dam 2 (RD2) over stages two and three at the Cameby Downs Coal Mine, located in Miles, Queensland under a construct-only contract. The mine is situated alongside the Warrego Highway, approximately 16 kilometres northeast of the Miles township and 30 kilometres northwest of the Chinchilla township within the Surat Basin, Queensland.

The scope of works involved several key components, including the construction of complex embankments, controlled placement of materials, construction of drains, batter chutes and emergency spillways. The intricate designs for the complex embankments were meticulously engineered to optimise the flow paths for tailings, ensuring they efficiently reached the return water pumps.

The controlled placement of materials involved 570,000 cubic metres of materials placed across three distinct embankment zones, requiring precise coordination and oversight to ensure materials were delivered to their designated areas accurately.

Construction of drains and batter chutes involved lining drains with 200mm rock and incorporating concrete sills at both the top and midpoint of the drains, of which the design allowed for reuse of concrete boxing across multiple sill locations, enhancing operational efficiency.

The emergency spillway construction was completed on the internal dividing wall which involved excavating and shaping the embankment to create a viable flow path down the wall's face.

To ensure resistance to scour, the spillway and chute were expertly lined with 400mm diameter rock and a concrete levelling sill was utilised at the top of the spillway as the foundation for a return water pipe support bridge. To further support the project's overall success, we efficiently managed the relocation of stockpiled materials from an existing stockpile within the impoundment area.

The Project delivered over 23,000 manhours (worked) without a single Lost Time Injury (LTI), showcasing our commitment to safety; despite facing 26 wet weather delays, the project team maintained an unblemished record with no reported environmental incidents, all while continuing to support the mine's production operations, under challenging stormwater conditions.

Among the project's notable achievements was our ability to maintain production levels, even in the face of a 30-day setback caused by adverse weather conditions over a six-month period. We showcased our expertise by successfully constructing complex embankment shapes to manage tailings flow effectively.

Furthermore, our commitment to collaboration and a harmonious working relationship with the staff at the Cameby Downs Mine was evident throughout the project. Our outstanding performance led to the client awarding us additional topsoil stripping works as the sole invitee, further solidifying our reputation for trustworthiness and capability.

‍Key Achievements

‍Maintained production despite 30 days lost to wet weather in six months.

Successfully constructed complex embankment shapes used to manage tailings flow.

Maintained exceptional relationship with the Cameby Downs Mine personnel and site representatives.

Awarded additional topsoil stripping works by Yancoal, Exact Civil Construction was the sole invitee.

‍“Exact Civil Construction achieved a high level of compliance to the quality specifications and took pride in the quality of the finished product. Exact worked openly and collaboratively with the project team to resolve any quality related issues to achieve good project outcomes.” – Project Quality Assurance/ RPEQ Certifier, Engeny