Monitoring groundwater production bores
Sampling and analysis for a wide range of chemical and microbiological contaminants is conducted annually for all groundwater production bores. Since 1974, 130 bores have been found to contain well below the respective MRLs for potable water. However a significant proportion of the samples have been found to contain pesticides at levels in excess of EPA criteria…Many of the numbers … contain more than one pesticide level in excess of the EPA criteria. For example, in the 1987 sampling, a total of 42 individual pesticide levels exceeded the EPA criteria.
These levels are not of concern with respect to the quality of the water for human consumption (the highest level found was 0.011 ug/L). However, they are useful as indicators of the possible increasing contamination of Metropolitan groundwater from organochlorine insecticides. DDT and dieldrin provide most excessive levels with 45 and 34 respectively; only 8 heptachlor and 3 chlordane levels exceed the EPA criteria. As Perth’s groundwater is recharged by direct infiltration of rainfall over the coastal plain (Ventriss 1988), these pesticide levels are likely to have originated from their previous agricultural and urban use, and to a much lesser extent, from the rainfall itself.
P45/46 Monitoring Pesticides – A Review – A Report to the Environmental Protection Authority by Peter A Rutherford. Environment Protection Authority. Perth Western Australia. Bulletin 407. December 1989.