Atrazine is the most common herbicide found in American drinking water, and most small systems meet it for the first time through a laboratory report, not a customer complaint. It has no smell and no taste at the concentration that matters. The federal maximum contaminant level is 0.003 milligrams per liter (3 parts per billion), set in 40 CFR 141.61 as a synthetic organic chemical. That makes atrazine a hard health-based compliance limit, not a secondary taste guideline. If you run a surface-water system in farm country and do not know what your last synthetic-organic-chemical sample showed, check your water system's compliance status free at orevant.com before you read on.
What the 0.003 mg/L MCL means
An MCL is the enforceable federal ceiling for a contaminant in finished drinking water. For atrazine it is 0.003 mg/L, and because the number is so small the laboratory reporting unit and the compliance calculation both matter. A detection near the limit is not automatically a violation, and a result below it is not automatically a clean pass; your primacy agency applies the sampling rules and rounding. But a confirmed running annual average above the limit is a health-based compliance event. See how MCLs differ from action levels for the regulatory distinction.
See exactly what your system is up against
Search by system name or PWSID and get your EPA violation history, open requirements, and upcoming deadlines in under a minute. Free, no account, no obligation.
Why atrazine shows up in surface water
Atrazine is a herbicide used on corn, sorghum, and sugarcane, applied mostly in spring. It runs off fields and into rivers, streams, and reservoirs during and after rain. That is why atrazine is primarily a surface-water problem, and why the systems that must watch for it are the ones pulling from rivers and reservoirs in agricultural watersheds, not the ones on deep groundwater.
The monitoring schedule you owe
Synthetic organic chemicals are not monitored continuously. Surface-water systems follow a schedule: initial quarterly sampling, then reduced monitoring if results stay reliably below the MCL. A confirmed detection can pull a system back to more frequent sampling, and the agency usually requires a confirmation sample before a violation is final. The points that matter are the sampling frequency your system is assigned, the sample location, and whether your most recent result was below the limit.
What to do after a high result
- Confirm the laboratory result and unit. Keep the laboratory report, chain of custody, sample location, and collection date together.
- Call the primacy agency before selecting a response. The correct next step depends on your source, your monitoring status, and the level of the detection.
- Confirm the sample. A single detection is usually confirmed before a violation is final, so do not skip the confirmation step.
- Evaluate treatment. Granular activated carbon is the standard treatment for atrazine, and it is a capital decision, not an afternoon fix.
What Orevant closes the gap on
A checklist tells you what to watch. It does not tell you what is already open on your system's public EPA record, what your current atrazine result is, or what your next sampling deadline is. That is the gap the scan closes.
Prefer to see the public record first? Check your water system free at orevant.com.
FAQ
Is 3 parts per billion a hard limit?
Yes. Atrazine's federal MCL is 0.003 mg/L, which is 3 parts per billion. It is a health-based primary standard, not a secondary taste guideline.
Does atrazine affect groundwater systems?
Less often. Atrazine is mostly a surface-water contaminant because it enters water through field runoff. Some shallow wells in agricultural areas can still be affected, which is why your assigned monitoring schedule, not an assumption, is what counts.
If I have a high result, am I automatically in violation?
No. A single detection is normally confirmed with a second sample, and the compliance calculation is applied by your primacy agency. But a high result is the signal to start the response now, not to wait.
What treatment removes atrazine?
Granular activated carbon is the standard, effective treatment. It is a system-level capital decision, so evaluate it with your engineer and your state before committing.