Water in Lake Maraetai is back to normal after a spill of treated sludge from the Kinleith paper mill earlier this month.
Environment Waikato says it has had calls from lakeside home owners preparing to come to the area for the holidays who were concerned about water safety for swimming.
However extensive monitoring had shown very little environmental damage from the spill of thousands of cubic metres of treated sludge on December 10.
Heavy rain over topped a temporary sludge storage dam at the mill site after the company’s temporary sludge dam failed. About three quarters of the loss was dam sediment rather than sludge. The sludge was organic and consisted of the ‘bodies’ of organisms that digest the waste in the treatment system. While some dead fish had been found elsewhere in Lake Maraetai following the spill, they were not thought to be a result of the spill.
Environment Waikato Processing Industry Programme Manager David Stagg said sampling by both Kinleith and Environment Waikato had found similar results.
At the time of the spill contaminants were measured in the discharge, the results of analysis are now available. Some metals concentrations were elevated and above guidelines, but chemicals such as PCP were well below guidelines, along with trace organics.
No lasting contamination was visible in the lake, which would be safe for swimming.
Medical Officer of Health Dr Dell Hood said the tests showed the river was now safe for contact recreation. The river water is unsafe for drinking unless treated, because of normal arsenic levels from geothermal sources.
A report on the spill and its effects will be made to the Council’s Regulatory Committee in the new year.