1998 – 2001: Gumeracha Weir (SA). Pesticides detected: Simazine, Endosulphan, Heptachlor..

Gumeracha Weir Pesticide Detections (SA Water)

1998 September 25 Simazine 1.25ug/L

2000 June 22 Endosulphan Sulphate 0.08ug/L

2000 June 28 Simazine 0.6ug/L

2000 July 3 Simazine 0.5ug/L

2000 July 19 Simazine 0.9ug/L

2001 May 18 Heptachlor 0.06ug/L

State Water Monitoring Coordinating Sub-committee Nov 2000

p11 Pesticides

Contamination of the Warren catchment and the Warren, South Para and Barossa Reservoirs by atrazine and hexazinone had been featured in media reports in 1998. Through 1999 and 2000 the concentrations of the two pesticides decreased gradually in the reservoirs. Although activated carbon was used at the Barossa Water Treatment Plant to remove the pesticides low concentrations were detected in some samples.

By September 1999 concentrations at the inlet to the Barossa Water Treatment Plant were consistently below 1.6ug/L and the use of activated carbon was discontinued. The health related guideline value for atrazine was 20ug/L and for hexazinone is 300ug/L. In the latest samples collected in mid August 2000 the concentrations were below detection limits at most most locations and including the inlet and outlet of the Barossa Water Treatment Plant.

There were occasional detections of pesticides throughout the period. The most common were of:

* simazine which was detected in four samples from Gumeracha Weir and in single samples from Little Para River and Reservoir, Torrens Gorge Weir and Tod Reservoir; and

*hexazinone which was detected in single samples from Little Para River and the River Murray at Murray Bridge, Mannum, Lock 9 and Loxton.

* Atrazine was detected in one samples of product water from the Hope Valley Water Treatment Plant, endosulfan sulfate in one sample from Gumeracha Weir and dieldrin which is no longer registered for use was detected in one sample from Mt Bold Reservoir.

The detection of atrazine and hexazinone in product water from the Barossa Treatment Plant, atrazine, in product water from the Hope Valley Treatment Plant (0.5ug/L), dieldrin in Mt Bold Reservoir (0.07ug/L) and the concentrations of hexazinone detected in the Little Para River (5.9ug/L) and the River Murray at Mannum (2.5ug/L) and Lock 9 (2.1ug/L) represented Type 1 incidents. However, the concentrations detected were well below the health related guideline values (atrazine 20ug/L; dieldrin 0.3ug/L; hexazinone 300ug/L) and DHS considered in each case that there was no risks to human health. Except for the results from the Barossa Treatment Plant the pesticide detections were gnerally isolated samples.

The remaining detections represented Type 2 incidents.

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