In Washington State, National Pollutant Discharge Elimination System (NPDES) permits are required for any application of pesticides in or adjacent to water including lakes, rivers, estuaries, and irrigation canals. This includes wetlands with standing water. If the ground is dry and residues will dissipate before the next rain, no permit is needed.
The Washington Department of Ecology (Ecology) developed these permits in 2001-2002 in response to a Ninth Circuit Court decision, Talent Irrigation District v Headwaters, Inc. Ecology has delegated authority from EPA to enforce the Clean Water Act in Washington State.
The following general NPDES Permits have been issued:
Two individual Permits were developed for unique circumstances:
Click here for a list of pesticides allowed under each permit: http://www.ecy.wa.gov/programs/wq/pesticides/regpesticides.html