The expansion of the Ord Irrigation Scheme in far north Western Australia has been downsized because of environmental concerns.


Project director Peter Stubbs says changes have been made to the layout of Ord Stage 2 because of the risk of future salinity problems.


"We've trimmed out 300 hectares of what was proposed to be farmland, because soil-sampling showed high levels of boron and it had the greatest propensity for future salinity risk," he said.


"There is a shallow lens of saline water there that we can design out and reduce risk, so that action has been taken, bringing the project down from 8,000 hectares to 7,700 hectares.


"It's an adaptive approach to mitigate any environmental concern and risk."


Mr Stubbs says there are also plans to widen environmental corridors within the layout of Ord Stage 2.


The changes coincide with the closure of the public comment period for phase 2 of the expansion project, with nine submissions being received - four were supportive, while the others raised concerns.


"The submissions that expressed concern were around the known environmental matters that had been of interest to the Commonwealth Government for some time," he said.


"They were issues with the Gouldian Finch population and particularly the management of ground water.


"We'll be addressing those and process our final documentation to the government which will trigger a mandatory 40 day period for the Commonwealth to assess the submission and make a determination."


Construction has already begun on the $220 million expansion of the Scheme, with Phase 1 due to be completed last year.  Rain however delayed the works and there is still four kilometres left to build on the M2 water channel.   Work is expected to resume on phase 1 by the start of June.


Phase 2 is yet to receive Federal environmental approval, which is expected by mid-July.