Dust threat for six homes in hydro work

Dust whipped up by construction of TrustPower's proposed Wairau hydro scheme will make six homes uninhabitable for up to three weeks and cause health problems for up to 40 households in the Wairau Valley.

Air quality specialist Andrew Curtis, of URS New Zealand Ltd, yesterday told the Environment Court panel considering TrustPower's application to build the scheme that six houses might not be habitable for two or three weeks.

He said people living less than 50 metres from the construction zone should be offered alternative places to stay and their homes cleaned before they returned.

Anyone who declined to move could instead have 10m windbreaks installed around their house. Crusting agents could be added to water used to lay dust and work done only in still conditions. Mr Curtis said there was no need to offer accommodation to residents of 14 homes between 50m and 100m from construction sites, despite this being a condition of a Marlborough District Council-appointed panel's prior approval for the scheme.

In Mr Curtis' opinion, the 20 houses between 100m and 300m from construction sites should not be seriously affected by dust. In his evidence, Mr Curtis said TrustPower had negotiated access agreements with 21 of the 40 residents likely to experience dust problems.

Conditions aimed at minimising dust included a requirement to stop work upwind of a house if wind speed exceeded 36kmh and planting canal banks. Wind speed would be measured at a single monitoring site at Hartley Hills, said Mr Curtis. When work was done closer to the exposed riverbed there could be an argument for contractors to monitor wind speed on-site.

Dust should be monitored during construction to check levels met standards set by the Ministry for the Environment, he said.

Save the Wairau lawyer Mike Hardy-Jones said the monitoring proposed by Mr Curtis would not pick up very fine dust which if inhaled posed the greatest health threats. These superfine particles were carried a lot further by wind than coarser dust and concentrations could be especially high indoors as they tended to float rather than settle, he said. Mr Hardy-Jones said the relocation would have a major effect on families. "If you went home to your wife and said we will be out of here for six weeks you would need a crash helmet on," he told Mr Curtis.

Public health physician Francesca Kelly said silica and asbestos were unlikely to be found in the Wairau Valley but they would be monitored.

The dust produced by TrustPower's construction work would most likely affect people with asthma, emphysema or chronic bronchitis, Dr Kelly said. Anyone with such conditions confirmed by their doctor could be relocated during the earthworks or measures could be taken such as screening their house, wetting dust and stopping work when windy. Dr Kelly was satisfied TrustPower's plans for monitoring of dust levels at affected sites and responding quickly to any problems should protect people's health.

She recommended that a house by house rather than "line on the map" approach be taken when planning construction, taking into account people's health conditions and willingness to be relocated.

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