1989 August: Blackwood River (WA). South of Nannup. Pesticide: Hexazinone The Results of Monitoring the Department of Conservation and Land Management Program of Applying Granulated Herbicides by Helicopter. A Report to the Environment Protection Authority. EPA Bulletin 435 June 1990. In 1989 an investigation of the environmental impacts of two herbicides proposed for helicopter application by the Department of Conservation and Land Management (CALM), was carried out by the Environment Protection Authority (EPA)… The environmental impacts of these chemicals on the aquatic environment was also monitored at five sites. The chemicals were leached into adjacent streams and intermittently detected at relatively low concentrations generally, but ranging from 0.8 to 38.0ug/L atrazine and 1.5 to 18ug/L hexazinone. There was no observed effect on aquatic growth in the Blackwood River, however in the streams at two application sites there did appear to be some impact on aquatic invertebrate drift… Folly Site: Hexazinone 2.3ug/L highest level 14/8/89 http://epa.wa.gov.au/EPADocLib/398_B435.pdf