127.7ha sprayed with 510.8kg of Velpar ULW in October 1989. The application was made under an experimental chemical permit obtained from the Department of Agricultural and Rural Affairs. Herbicide was detected at 6.0ug/L, 1 hr after spraying was completed and 7.5ug/L, 6 days after spraying and after light rain had been falling. . . Monitoring was undertaken 2 to 3 km downstream of the treated areas detected trace residues of hexazinone in only three of the 24 samples analysed, the maximum concentration being 1.3ug/L. (See Weed Control in Radiata Pine plantation by aerial application of granulated hexazinone-Lands and Forests Technical Report No. 5. Conservation and Environment 1991).