The development of Deposits C and D at West Angelas, 130km northwest of Newman, will expand the site by 4100 hectares to 26,700ha.

The EPA held roundtable discussions with Rio regarding the impact to Karijini National Park of pumping up to 14 gigalitres per annum of groundwater and the EPA recommended a condition for managed aquifer recharge to maintain groundwater levels.

Rio will also have to monitor surplus water discharge into Turee Creek East under an environmental management plan.

The EPA also recommended contributions to the Pilbara Environmental Offset Fund to offset the impact of additional clearing on flora and fauna, including the endangered ghost bat.

"This assessment work and recommended conditions constitute a comprehensive approach to management of environmental impacts, following a proactive approach by the proponent and extensive consultation with the EPA," EPA deputy chair Robert Harvey said.

Minister for environment Stephen Dawson will have the final say after a two-week public appeal period closes on May 27.

In October last year, Rio and its Robe River joint venture partners Mitsui and Nippon Steel & Sumitomo Metal approved $1.55 billion in sustaining capital at West Angelas and Robe Valley to maintain production.