Chemigation Regulation Overview
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Chemigation as a Method of Pesticide Application
Chemigation is a method of pesticide application in which pesticides
are injected into irrigation water. Before a pesticide can be chemigated,
it must be labeled to indicate that chemigation is an allowed method
of application. Additionally, the label must contain instructions
on application techniques and on backflow prevention of pesticide
residues from the irrigation system to the irrigation water source.
Currently, chemigation is specified as a method of application for
nearly 30% of the approximately 410 active ingredients contained in
registered products in California, and on over 300 separate pesticide
products.
Chemigation as a Source of Groundwater Contamination
If proper safety measures are not taken, groundwater can be contaminated
when irrigation water containing pesticides is allowed to backflow
into the well supplying the water. Pesticides that flow back into
the well can mix with, and move in the normal flow path of, groundwater. If the well also supplies drinking water, the pesticide residues
will immediately contaminate the drinking water. If the well provides
only irrigation water, pesticide residues can be transported in
groundwater as it flows to drinking water wells.
Chemigation Defined
Chemigation is defined in the California Food and Agricultural Code
Section 13142 (opens in new browser window) as a method of irrigation
whereby a pesticide is mixed with irrigation water before that water
is applied to the crop or to the soil. Section 13142 is part of
the Pesticide Contamination Prevention Act, which is designed to
prevent further pollution of groundwater used for drinking water
supplies from the agricultural use of pesticides.
Chemigation is also defined by the Department of Pesticide Regulation
(DPR) in Section
6000 of Title 3 of the California Code of Regulations (Definitions),
which similarly describes chemigation as the application of pesticides
through irrigation systems.
Product Labels Require Backflow Prevention Devices for Chemigation
The increased use of pressurized irrigation systems, such as macro-sprinkler,
micro-sprinkler, and drip systems, facilitated the injection of
chemicals from a fixed point of application. The prevention devices
listed on the pesticide labels and their approved alternatives are
part of an integrated system that, in addition to preventing backflow
into wellheads, also assures proper metering and application of
pesticides through properly designed irrigation systems.
In 1987, the United States Environmental Protection Agency (U.S. EPA) issued Pesticide Registration (PR) Notice 87-1 (opens in new browser window) to clarify label requirements when chemigation is a method of application. This notice required registrants to revise the labeling of pesticide products registered under the Federal Insecticide, Fungicide, Rodenticide Act (FIFRA) (opens in new browser window) and intended for application through irrigation systems (chemigation) to include "additional use directions and other statements." According to FIFRA , it is unlawful for any person to use any registered pesticide in a manner inconsistent with its labeling. Pesticides not labeled for chemigation applications must contain language indicating that the product cannot be applied through an irrigation system. Thus, it is illegal to apply pesticides by chemigation if "additional use directions and other statements" specific for chemigation are not contained on the label. When using chemigation as a method of application, the user must conform to the requirements for backflow prevention stated on the label, except as provided in U.S. EPA's memorandum listing approved alternatives.
After the initial PR notice, U.S. EPA received comments indicating
a wider range of acceptable devices for backflow prevention. As
a result of this information, the U.S. EPA released a memorandum
listing chemigation equipment that could be used as alternatives.
In some cases, the alternative equipment was less expensive, more
reliable, or more available than some of the equipment initially
approved as acceptable devices. For example, even though a label
specifically states to use an injection pump to chemigate a pesticide,
use of a Venturi system is a legally approved substitute. Any chemigation
equipment that is required on pesticide product labeling that has
no listed alternative(s) is still required as a component of the
chemigation system.
DPR Backflow Prevention Regulations
The DPR regulation for backflow prevention in
3CCR section 6610 states that each service rig and piece of
application equipment that handles pesticides and draws water from
an outside source shall be equipped with an air-gap separation,
reduced pressure principle backflow prevention device, or double
check valve assembly. Backflow protection must be acceptable to
both the water purveyor and the local health department.
This rule, established in 1977, was intended to clarify responsibilities for connection to public water systems, so the language reflected requirements in the Health and Safety Code. The requirement for public water systems is still applicable but connections to non-public water systems, such as domestic and irrigation wells, is now more appropriately covered by U.S. EPA label language requirements. In contrast to public water system wells where there is generally constant pressure, non-public system wells run intermittently, and thus require different backflow prevention components.
In 2001, DPR issued two enforcement letters,
ENF 01-12, PDF and
ENF 01-28 (PDF, 398 kb), to clarify that the EPA label language
is appropriate protection for chemigation systems connected to stand
alone domestic and irrigation wells. These letters affirm DPR's
adoption of the EPA label language and include a list of alternative
components.
Who Is Required to Have Backflow Prevention Devices?
Anyone applying a pesticide through an irrigation system is required to have functional backflow prevention devices installed. The components differ depending on the type of connection. If you are connected to a municipal system and use the water for irrigation, you must conform to California Regulations for Drinking Water for connection to municipal systems. These requirements can also be obtained from local County Environmental Health Departments. If your water source is a stand-alone well, you must comply with the label language for the pesticide product, except when there are alternatives approved by U.S. EPA. For example, a Venturi system can substitute for a positive displacement injection pump. Contact your local County Agricultural Commissioner (California Department of Food and Agriculture page opens in a new browser window) if you have any questions.