Acid rain from a proposed $200m  cement plant at Weston poses a major threat to North Otago, and Oamaru’s historic buildings "could dissolve before our eyes", a public meeting was warned last night. 
 
The meeting at Weston was called by the Waiareka Valley Preservation Society, which is opposing Holcim (NZ) Ltd’s investigations into the Weston plant as one of four options to meet a growing demand for cement in New Zealand. Holcim will not make a decision on the plant until 2008, but will file resource consent applications early next year.
 
Last night’s meeting, attended by about 130 people, was the first called by the society and its spokesman, Rodney Jones, presented information the group had so far on the risks from the planned plant. 
 
Mr Jones said part of the difficulty about providing that was the lack of information from Holcim, something the society hoped to put right in a meeting with the company today. 
 
He said acid rain from the cement plant represented an extreme threat both to Oamaru’s historic precinct, and to the large number of historic limestone homes, barns and other buildings in the broader Oamaru and Waiareka Valley area. 
 
"Historic Oamaru is now recognised as being a key part of our national heritage as New Zealanders. This will all be threatened if Holcim - a foreign company with no significant New Zealand shareholders - are granted resource consent to construct their cement plant," he said. 
 
With a planned capacity of 1 million tonnes a year, the Holcim cement plant would emit up to 600kg to 700kg of nitrogen oxide (NO2) and sulphur dioxide (SO2) an hour. The exact amounts would depend on the pollution control equipment at the plant and the sulphur content of the Ngapara coal that Holcim intended to use. 
 
"Irrespective, the volumes of oxides emitted would be extraordinarily large, reaching up to or in excess of 6 million kg per annum," Mr Jones said. 
 
When sulphur dioxide was in the atmosphere, it became sulphuric acid as it joined with hydrogen atoms in the air and fell back to the earth as acid rain. 
 
Evidence from the United States and Canada suggested a high proportion of the acid rain would occur within a 15km radius of the cement plant. This included Oamaru, and its historic limestone buildings, only 7.5km from the smokestack. 
 
Acid rain falling on buildings that had had no exposure to acidic rain in 120 to 130 years, would cause them to deteriorate with extraordinary rapidity. 
 
"If the Holcim cement plant is granted consent, historic Oamaru will quite literally begin to dissolve before our eyes," Mr Jones said. 
 
Oamaru had survived with its Victorian architecture intact because of the lack of heavy industry. To introduce heavy industry emitting sulphur dioxide and nitrogen oxide now would quickly destroy all that was precious to the community, he said.