Environment Waikato, Hamilton City Council and the Waikato District Health Board are planning a more integrated surveillance and management strategy for the Waikato River after last month’s bacterial contamination upstream of Hamilton.
This week’s Environment Waikato Environment Committee meeting heard that the marked increase in E. Coli bacteria found in the River downstream of Cambridge in early April was a surprise. Although there had previously been increases as the River passed through Hamilton, the levels observed in early April were higher than usual.
Water scientist Bill Vant said in the 1950s the section of the River downstream from Cambridge had very high levels of faecal bacteria. However major improvements in the treatment of sewage and industrial wastewater meant that since the late 1970s levels of bacteria had usually been much lower, although still periodically too high for safe swimming.
The Council had two programs that routinely monitored levels of faecal bacteria in the River -- monthly monitoring at 10 sites between Taupo and Tuakau and weekly monitoring every second summer at 14 sites. Levels of faecal bacteria had been increasing at sites in the lower half of the River in recent years.
On April 5 the Waikato Medical Officer of Health reported high bacteria levels, and special surveys were done on April 7,18 and 30. The discharge was traced to the dairy factory at Hautapu and it was presumed that bacteria had got into a clean water vat and grown over time. By May 6 all levels had dropped well below safe swimming levels, and the Council was confident it had tracked the source.
An investigation into the matter would be reported to the Regulatory Committee next month and four River surveys were planned at weekly intervals this month.
Medical Officer of Health Dr Dell Hood said the Region had a high incidence of food and waterborne diseases, possibly related to farming and other animal contact, consumption of raw milk, consumption of untreated drinking water, and poor food handling.
It appeared many people were not aware of the well-documented risk of bacterial pollution in water. Warning signs currently in place correctly described the real risk of swimming as drowning, but there was no public information about the possibility of bacterial pollution.
She was meeting with local authorities to ensure a consistent approach to warning signs, and there was a long-term plan to put together a better communications process.
Chairman Lois Livingston said she was pleased that the source of the bacteria had been identified and that the river was back to its usual levels.
“The public is interested in water quality and we must respond,” she said.