The three-year extensions replace Sedgman's existing agreements at the mines, continuing parent company CIMIC Group's longstanding relationship with QCoal.
CIMIC Group CEO Juan Santamaria said CIMIC had a strong history of delivering consistent outcomes for QCoal, through its companies Sedgman and Thiess.
"Sedgman's expertise in minerals processing and focus on maximum resource recovery will help drive even greater efficiencies at these mines," he said.
Sedgman managing director Grant Fraser said the contracts were testament to the partnership it had forged with QCoal over many years, and the integration of its engineering design, project delivery and operations teams.
Sedgman undertook the engineering design, construction and commissioning of the coal handling and preparation plant at Sonoma in 2007, and has continued to optimise and expand the facility, operating it since 2007.
Sedgman delivered engineering, procurement, construction and commissioning services for a train loadout facility and processing plant at Byerwen in 2017, and the engineering, procurement, construction and commissioning of a duplication of the coal handling and processing plant in 2018 and has been operating it since then.