CIMIC CEO Juan Santamaria said UGL's wins were multi-year contracts providing mechanical, electrical, instrumentation and access services for maintenance, shutdowns and sustaining capital projects, with hundreds of jobs supported.
The work includes civil, structural, mechanical, piping, electrical, communications and instrumentation work for Rio at the Mesa J PP2 rescreening plant. The task will take around 12 months and employ 160 workers.
UGL has also secured a contract extension for scheduled major shutdown services at Rio's alumina refinery.
A further 100 workers will install a run-of-mine crusher and materials handling circuit for Roy Hill, comprising supply, structural, mechanical, electrical and instrumentation works.
UGL has also been appointed to BHP's engineering services panel to provide civil, structural, mechanical, piping, electrical, instrumentation and rail services for shutdowns and sustaining capital projects across its WA iron ore mines, rail facilities and port operations.
The contract comes just days after the CIMIC announced it had signed an exclusivity agreement with funds advised by Elliott Advisors over a potential equity partnership over another subsidiary, Thiess, to raise capital for Thiess' growth options.
CIMIC calls Thiess "the world's biggest mining services company".
A share purchase agreement was expected in the next few weeks.
CIMIC shares last traded at $22.70, valuing it at $7.2 billion.