Water samples were also collected from the southern branch of the Collie River and from a stream site called Darrell. The samples were analysed for both atrazine and hexazinone… The treatment site area drained directly into the Collie River…
The concentrations of atrazine observed in the river on 24 July were very high and exceeded what would normally be considered as a safe limit for the maintenance and preservation of aquatic ecosystems…, but were unlikely to be sufficiently high to kill aquatic fauna.
The samples were taken in a wet period during a suddent heavy fall of rain (18mm) from the side of the river and directly downstream of the application area…
Grimwade Site: Hexazinone 4.4ug/L highest level 28/7/89, Atrazine 0.8ug/L highest level 28/7/89.