1961 March: Tongala (Vic). Weed Control in Drains. Pesticide: Amitrole – highest level 19,500ug/L

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State Rivers and Water Supply Commission

Details of Testing and Results

1961. In the period 14/3/61 – 23/3/61 various formulations (Weedazol 50, Weedazol Total, Weedazol T1) were applied to water couch in 12 miles of drains at Tongala, and 77 samples were taken from drains to indicate the pattern and extent of contamination. Flow velocities in the drains varied from 0 – 0.9 MPH. Sampling at the outfall of this system gave a maximum of 0.70 p.p.m., but a more representative figure would be 0.30 p.p.m.

Samples taken 100 yards – 3/4 mile downstream of operating spray teams showed levels in the range of 0 – 19.5 p.p.m. The average contamination level was 0.25 p.p.m., representing 20% of applied material. There was no indication of reduction of contamination with distance downstream, or any consistent loss of activity with storage over three months…