A key focus for South32's (ASX:S32) Hermosa zinc-lead-silver project in Arizona is project execution, with the ventilation and main shafts expected to reach the primary production level in the December quarter, RBC Capital Markets said in a Thursday note.

As of July, the main shaft was around 70% complete, and the ventilation shaft was around 90% complete.

The firm will host a site visit to its Hermosa project on Sept. 14 to Sept. 15. Hermosa is its largest growth project, and the Taylor deposit at the project includes one of the world's largest undeveloped resources of zinc.

Work is ongoing to extend the Clark decline, providing additional access to the Taylor orebody, increasing ore handling capacity by around 25%. This will potentially increase production above design capacity through plant de-bottlenecking.

South32 is set to provide an update on plans to potentially de-bottleneck the plant to 5 million tonnes per annum, up from the planned capacity of 4.3 million tonnes per annum.

The investment firm retained its outperform rating and AU$5.50 per share price target on South32.