A growing practice in many areas of the country is the application of pesticides through irrigation systems, often termed "chemigation". Although there are systems specifically designed for chemigation, in most cases an existing irrigation system is modified to mix the chemical with irrigation water. Fertilizers are generally stored in large tanks located near wells drawing ground water for irrigation. Fertilizers flow from the storage tanks into the irrigation water.
Concerns about ground water contamination from this practice arise from the
fact that accidental backflow or siphoning of chemicals into the well can occur
when the irrigation pumping system shuts down unexpectedly. Unless the pesticide
user's equipment meets the following conditions set by the EPA, it will be in
violation of FIFRA.
Rules For Chemigation Equipment
- The system must contain a functional check
valve, vacuum relief valve, and low pressure drain appropriately
located on the irrigation pipeline to prevent water source
contamination from backflow.
- The pesticide injection pipeline must contain a
functional, automatic, quick-closing check valve to prevent the flow of
fluid back toward the injection pump.
- The pesticide injection pipeline must also
contain a functional, normally closed solenoid-operated valve located on
the intake side of the injection pipe and connected to the system
interlock to prevent fluid from being withdrawn from the supply
tank when the irrigation system is either automatically or manually
shut down.
- The system must contain functional interlocking
controls to automatically shut off the pesticide injection pump when
the water pump motor stops.
- The irrigation line or water pump must include a
functional pressure switch, that will stop the water pump motor when the
water pressure decreases to the point where pesticide distribution
is adversely affected.
