Planned erosion and sediment spill mitigation for the proposed $2 billion Project Hayes wind farm was questioned during an Environment Court appeal hearing for the development yesterday.
Technical director Graham Levy, of Christchurch, gave evidence as a witness called by the Otago Regional Council.
Mr Levy was asked by several appellants and party lawyers whether planned mitigation of perceived problems on the site would actually work, as the proposed development was unique in size, scale, and location.
Maniototo Environmental Society counsel Mike Holm asked whether measures successful on smaller wind farms would work on the larger Project Hayes site, which was in a more extreme environment than other wind farms on which mitigation had been trialled.
Mr Levy's written evidence stated some Wellington City Council guidelines used at a wind farm at Makara could apply in the case of Project Hayes, although when cross-examined by Mr Holm he admitted he was not familiar with the Makara site, whether such guidelines had been effective, or whether they would work in the same way on the Lammermoor Range.
"The guidelines are widely used and are non-specific so I didn't think it was necessary to apply them to particular sites," he said.
Meridian Energy's 176-turbine wind farm would encompass 92sq km on the Lammermoor Range if consented, and would be the largest such development in the southern hemisphere.
Mr Levy said mitigation should work if applied "rigorously", which would include consent authorities visiting the site at least once a week to inspect construction effects, so long as Meridian Energy carried out all proposed measures as planned.
In response to a question from Mr Holm, Mr Levy said he had been near the proposed site twice, although on both visits he did not he inspect the actual site, but drove along Old Dunstan Rd and to the Logan Burn Reservoir, "observing the area in general".
When cross-examined by Upland Landscape Protection Society counsel Ewan Carr, Mr Levy admitted he did not have experience of earthworks and potential mitigation of such works at a site of the Project Hayes development's elevation.
He said it would be harder to stabilise certain construction areas during winter when earthworks were exposed to snow and frost followed by rain.
"The freeze-thaw process will make the underlying surface more unstable but the top layer should protect it, although it will result in an increased risk of sediment run-off.
"Sediment control ponds are designed to deal with this as they have a certain amount of capacity to take sediment build-up ," Mr Levy said.
During cross-examination by Judge Jon Jackson, deputy commissioner Ken Fletcher and commissioner Heather McConachy, Mr Levy said he had relied on the evidence of other witnesses about revegetation and could not specifically comment on what mitigation might be necessary to aid or allow revegetation after construction.
Judge Jackson said he could see a problem arising if stock were grazed in areas where revegetation of earthworks was attempted, although Mr Levy could not specifically answer the judge's question about the areas of land where stock should be excluded until revegetation was complete.
He said excluding stock from areas of major earthworks and vegetation between turbine sites could be a "helpful alternative but not essential".