[4 October/ Stuff]

A proposed nitrate wall implemented into Silverstream Reserve near Kaiapoi to lower the steam’s high nitrate levels may improve the safety of freshwater and groundwater resources and potentially provide means for farming within water quality limits. The Institute of Environmental and Scientific Research planned to evaluate whether the wall, successfully used with sandy aquifer systems at Waikato and the United States, could have the same outcomes for gravel aquifer systems such as at Silverstream and elsewhere in Canterbury. The Silverstream waterway has high nitrate levels that are over the environmentally sound limit. The study was proposed by ESR Senior Scientist Lee Burbery. The denitrification wall comprises of woodchips, mixed with gravel aggregate, and strips nitrate from groundwater passing through it. Carbon within the wall provides a food source for bacteria to convert nitrate in groundwater to nitrogen gas. ESR Principle Scientist Murray Close hoped the project would begin this summer.