10.2 Surface Water, Groundwater, Anti-Siphon, and Rule 40-23
Key Takeaways
- GDA’s Agricultural Pest Control page lists Agriculture Rule 40-23 as Prevention of Ground and Surface Water Contamination; opened, the chapter is definitions, anti-syphon device specs, and a $1,000 penalty—not aquifer percentages.
- O.C.G.A. § 2-1-4 requires any irrigation system designed or used to apply fertilizer, pesticide, or chemicals to have a check valve and low pressure drain in the supply line between the irrigation pump and the injection point; using an unequipped system is unlawful.
- Rule 40-23-2-.01 adds a vacuum relief valve, a ≥3/4-inch low-pressure drain on the bottom of the pipe between the check valve and the pump with the outlet ≥2 inches above grade, a level horizontal check valve with replaceable disc, and a ban on gate valves that defeat the drain.
- Rule 40-23-3-.01 and the statute both cap the Commissioner’s administrative penalty at $1,000 per violation after hearing, including a device that is installed but not in operating condition.
- National Core Chapter 7 teaching still applies: mix and load at least 50 feet from wells and surface water when practical, keep an air gap of at least twice the fill-pipe diameter, and treat back-siphoning at a wellhead as point-source contamination.
10.2 Surface Water, Groundwater, Anti-Siphon, and Rule 40-23
Georgia’s pesticide program treats water as a primary environmental receptor. The Georgia Department of Agriculture (GDA) Agricultural Pest Control page lists two water-protection authorities side by side: the Georgia Anti-Syphon Device Act (O.C.G.A. § 2-1-4) and Agriculture Rule 40-23 (Prevention of Ground and Surface Water Contamination). Open Rule 40-23 and you will not find a Floridan Aquifer percentage, a statewide well-setback table, or a general “do not pollute” essay. You will find three subjects: definitions (40-23-1), anti-syphon devices (40-23-2), and penalty (40-23-3). That is what the rule actually says. National Core Chapter 7 still supplies the hydrology you need—runoff versus leaching, point source versus nonpoint source, soil texture, organic matter, and water-table depth—and the label still supplies well and water buffers. Do not invent numbers the rule does not publish.
Surface water versus groundwater
Surface water is the water you can see: ditches, streams, rivers, ponds, lakes, and the storm-drain network that dumps urban turf runoff into creeks. It is a drinking-water source for many systems, a fishery, and the first place a soluble insecticide goes after a wash-off.
Groundwater occupies cracks and pore spaces below the water table. The saturated zone is the layer in which those spaces are full of water. An aquifer is a geologic formation that can yield groundwater to wells and springs. South Georgia agriculture sits over productive aquifers, including the Floridan in much of the Coastal Plain. This chapter does not invent a percentage of Georgia drinking water that comes from any named aquifer. What you must know operationally is simpler: once groundwater is contaminated, cleanup is slow, expensive, and sometimes impossible, so prevention is the control.
Surface water and groundwater are not sealed from each other. Runoff can enter a losing stream or a sinkhole and drop into groundwater. That is why a “surface” spill at a mix/load pad can become a well problem.
Runoff versus leaching, and the soil that sits in between
Runoff is overland flow. Risk rises with slope, intense rain, saturated or frozen ground, little vegetative cover, and pesticide sitting on hard surfaces (granules left on a Marietta driveway after a Category 24 application). Runoff carries dissolved product and eroded sediment.
Leaching is downward flow with percolating water. A pesticide is more likely to leach when it is highly soluble, weakly adsorbed, and persistent, and when the soil is sandy, low in organic matter, and the water table is shallow. Clay and organic matter add binding sites and slow water. Macropores—cracks, worm holes, root channels—can short-circuit even a clay soil. Highly permeable geologic layers (gravel, some limestone) pass water and dissolved pesticide more freely than tight clay layers.
| Site factor | Higher leaching risk | Lower leaching risk |
|---|---|---|
| Texture | Sand (fast percolation, few binding sites) | Clay / silt (slower water, more binding sites) |
| Organic matter | Low OM | High OM holds water and adsorbed pesticide in the root zone |
| Water table | Shallow (short filter path) | Deep (more soil for adsorption and degradation) |
| Geology | Gravel, sinkholes, direct conduits to wells | Tight, low-permeability layers |
Do not mix and load beside a well because you “only have a general-use product.” Wells—especially poorly capped or abandoned wells—are direct pipes to groundwater.
Point source versus nonpoint source
Point-source contamination comes from an identifiable location: a spill into a storm drain, back-siphoning into a well while filling a tank, dumping rinsate in a sinkhole, repeated drips at the same mix/load site, wash water at a cleanup pad, leaks at storage, or leftover concentrate poured down a well.
Nonpoint-source contamination comes from a widespread treated area: a broadcast herbicide on cotton or soybeans, a right-of-way spray, or a city turf program, followed by rain that moves a little product from many acres.
Exams love to reverse these. Leaching after a broadcast application is typically nonpoint. Back-siphoning at one wellhead is point source—and it can move a large quantity of concentrate fast.
Mix, load, and back-siphoning (National Core BMPs—not extra Rule 40-23 text)
National Core Chapter 7 tells applicators to mix and load as far as practical from wells and surface water—at least 50 feet is the distance taught in Core—and to prefer the application site or a sealed pad. Keep pesticides out of well pits.
Back-siphoning is reverse flow from the tank into the fill hose and then into the water supply when pressure drops. It happens when the hose end is submerged in the spray mix. Prevent it with:
- An air gap of at least twice the diameter of the discharge pipe between the hose outlet and the liquid surface, and/or
- A backflow prevention device (check valve) on the fill line.
Never put the fill hose in the tank. Never leave a nurse-tank hose sitting in a mix. Outdoor product labels also carry the generic environmental-hazard statement: do not apply directly to water except as labeled, and do not contaminate water when cleaning equipment. Groundwater advisories on sandy-soil products are label law even though they are not copied into Rule 40-23.
What Rule 40-23 actually contains
Rule 40-23-1-.01 defines the four words the rest of the chapter uses:
- Chemical — any substance, natural or synthetic, soluble or insoluble, organic or inorganic, solid or liquid, intentionally added to water for agricultural purposes.
- Fertilizer — a plant nutrient regulated under the Georgia Plant Food Act of 1970.
- Irrigation system — a device or combination of devices with a hose, pipe, or other conduit that connects directly to any source of ground or surface water and applies that water for agricultural purposes. It does not include a handheld hose sprayer or similar device built so that an interruption in water flow automatically prevents backflow to the source.
- Pesticide — insecticide, fungicide, rodenticide, herbicide, desiccant, plant regulator, or other substance regulated under the Georgia Pesticide Control Act of 1976.
If you inject fertilizer, pesticide, or agricultural chemicals through an irrigation system plumbed to a well or a surface source, you are inside this chapter. A handheld hose that breaks siphon when you shut the water off is outside the irrigation-system definition.
O.C.G.A. § 2-1-4 (the Anti-Syphon Device Act)
The statute is short and exam-friendly:
(a) Any irrigation system designed or used for fertilizer, pesticide, or chemicals must be equipped with an anti-siphon device adequate to protect the water supply. That device shall consist of a check valve and a low pressure drain in the irrigation supply line located between the irrigation pump and the point of injection. Systems that complied with the law in effect on January 1, 1982 are deemed in compliance with this subsection.
(b) It is unlawful to use such a system that is not equipped as required.
(c) The Commissioner may adopt rules on device requirements and placement.
(d) After a hearing under the Georgia Administrative Procedure Act, the Commissioner may issue an administrative order imposing a penalty not to exceed $1,000.00 for each violation. Penalties go to the state treasury. The penalty is concurrent, alternative, and cumulative with other civil or criminal remedies.
Memorize the hardware location: pump → drain and check valve on the supply line → injection point. Injection upstream of the check valve is the failure mode the Act exists to stop.
Rule 40-23-2 hardware (the rule is more specific than the two-part statute list)
Rule 40-23-2-.01 requires an anti-syphon device with these components:
(a) Functional check valve. Replaceable disc; serviceable with conventional tools; in the supply line between the irrigation pump and the injection point; installed on a horizontal plane and level.
(b) Low pressure drain. At least three-fourths inch in diameter; on the bottom of the horizontal pipe between the functional check valve and the irrigation pump; level; must not extend beyond the inside surface of the bottom of the pipe; outside opening at least two (2) inches above grade.
(c) Vacuum relief valve. Included as part of the drain or as a separate valve. A separate valve must be at least three-fourths inch and sit on the top of the same horizontal pipe section as the drain.
(d) No defeat devices. You may not alter the drain or vacuum relief—including adding a gate valve—in any way that makes the anti-syphon system inoperative or that would allow someone to make it inoperative.
Rule 40-23-2-.02: check valves, drains, and vacuum relief valves must be kept free of corrosion or buildup and operative at all times during operation of the system. A rusted-shut drain is not “installed.”
Rule 40-23-2-.03: place the components as shown in the rule’s Diagram 1.
Rule 40-23-3-.01: using an irrigation system for fertilizer, pesticide, or chemicals without the required device or without it in operating condition is subject to a maximum penalty of $1,000.00 after hearing.
| Authority | What it actually requires |
|---|---|
| O.C.G.A. § 2-1-4(a) | Check valve and low pressure drain between pump and injection point |
| Rule 40-23-2-.01 | Adds vacuum relief, 3/4-inch minimums, 2 inches above grade, level horizontal check valve, no defeat valves |
| Rule 40-23-2-.02 | Devices must work whenever the system runs |
| Rule 40-23-3-.01 / § 2-1-4(d) | Up to $1,000 per violation administrative penalty |
[!WARNING] Chemigation of a peanut or cotton field from a center pivot on a well is the classic Georgia fact pattern. The statute names two parts (check valve plus low-pressure drain). The GDA rule adds vacuum relief, dimensions, orientation, maintenance, and a ban on shutoff valves that defeat the drain. Answer with the rule when the question is about Georgia irrigation equipment.
Worked Georgia site
A Category 21 grower in Colquitt County injects a labeled insecticide through a well-supplied pivot. The injection pump sits on the supply line. If the check valve is downstream of injection, or if someone piped a gate valve onto the low-pressure drain “so we can winterize it,” the assembly does not meet Rule 40-23-2-.01. Using that system is unlawful under § 2-1-4(b) and is a $1,000-class administrative violation under both the Act and Rule 40-23-3-.01—even before any well test shows contamination.
Under O.C.G.A. § 2-1-4, an irrigation system designed or used to apply fertilizer, pesticide, or chemicals must have which anti-siphon equipment in which location?
A GDA inspector measures the anti-syphon assembly on a Georgia chemigation pivot. Which low-pressure drain installation matches Rule 40-23-2-.01?
Which event is a classic point-source pathway to groundwater rather than nonpoint-source field runoff?