Nitrate/Nitrite Rule
The nitrate rule applies to all classes of Public Water Systems (PWS) that use surface or ground water.
- The Nitrate Rule is referenced in the Administrative Rules of Montana (ARM)
- 17.38.216, which adopts Code of Federal Regulations (CFR) 40.141.23.
- Testing and Sampling Records and Reporting Requirements are described in 17.38.234.
- a. post in conspicuous locations
- b. hand or direct delivered
- c. radio
- d. television
What are nitrates?
Nitrate (NO) is a molecule made up of nitrogen and oxygen. Nitrate is formed when nitrogen from ammonia or other sources combines with oxygenated water.
What are organic sources of nitrogen?
Nitrate and nitrites are by-products of septic systems. It is a naturally occurring chemical that is left after the breakdown of animal or human waste.
What are inorganic sources of nitrates and nitrites?
Nutrients from fertilizers such as potassium, phosphate or nitrate are discharged into surface water run-off.
What are nitrites?
Nitrites (NO2) are composed of nitrogen and oxygen. When nitrates are taken into the body, they are converted to nitrites.
What are the public health risks of nitrate and nitrite exposure?
Infants under 6 months are most vulnerable to high nitrate levels. In the body, nitrates are converted to nitrites which interfere with the oxygen carrying capacity of the blood. High levels of nitrates in drinking water have caused serious illness and sometimes death. Symptoms of this condition – called Methomethoglobinemia are shortness of breath and blueness of the skin.
Long term exposure to levels above the Maximum Contaminant Level (MCL) can cause diuresis, increased starch deposits and hemorrhaging of the spleen. EPA Nitrate Basic Information
When are surface and ground public water systems required to sample for nitrates?
Before water is served to the public, every new source of water, both surface and ground must be sampled for nitrate and nitrite.
After the initial test, every public water system must sample for nitrate annually.
What are the nitrate sampling requirements for surface water systems?
Surface water systems must collect one sample at every entry point to the distribution system after any application of treatment or in the distribution system at a point which is representative of each source after treatment. (ARM 17.38.216 adopts CFR 141.23 (a)(2)).
Where and when are nitrate and nitrite samples collected by ground water systems?
"Groundwater systems shall take a minimum of one sample at every entry point to the distribution system which is representative of each well after treatment beginning in the initial compliance period." (ARM 17.38.216 adopts CFR 141.23 (a)(1))
What is the Maximum Contaminant Level (MCL) for nitrate and nitrite?
10 mg/L of combined nitrate and nitrite. The maximum contaminant level for nitrite is 1 mg/L.
What if the nitrate concentration is equal to or greather than fifty percent (5 mg/L or greater) of the maximum contaminant level?
The repeat monitoring frequency for groundwater systems is quarterly for at least one year and until samples demonstrate that the level is reliably and consistently below the maximum contaminant level.
What is the maximum contaminant level (MCL) for nitrates and nitrites?
The MCL for nitrate is 10 mg/L and 1 mg/L for nitrites. The MCL for combined or total nitrate and nitrite is 10 mg/L (ARM 17.38.203).
Nitrate MCLs are not calculated on a running annual average. A public water supply may not continue to operate when nitrates exceed 10 mg/L. An MCL requires the corrective actions of removing the source of contamination, developing a new source of water or treating the source. The PWS should consult with a Montana DEQ rule manager or engineer about which corrective actions may be appropriate.
If a new public water supply exceeds a maximum contaminant or action level what is required?
The Montana Department of Environmental Quality (MT DEQ) may require further sampling or corrective action.
When can a water supply return to annual monitoring?
When nitrate and nitrite results are reliably and consistently below 5 mg/L for at least 2 consecutive quarters, a water supply may qualify for annual monitoring.
If a sample result exceeds the maximum contaminant level, what is required on behalf of the Public Water Supply?
The Public Water Supply should take a confirmation sample within 24 hours of being notified of the analytical results. The initial and confirmation samples are averaged to determine compliance.
If the average exceeds the MCL of 10 mg/L and a system is unable to comply with the 24-hour confirmation sampling requirement what course of action must it take?
A maximum contaminant level violation with a Tier 1 Public Notice is issued by MT DEQ.
What is a Tier 1 Public Notice for a Nitrate and Nitrite exceedance?
A Tier 1 Public Notice (PN) informs customers not to give the water to infants 6 months of age and younger. The PN provides a physical address at which bottled water can be obtained and advises against boiling the water.
One of the following methods should be used to deliver the Public Notice to customers
What rule governs the operation of a PWS that exceeds an MCL?
The Montana Code Annotated
How are corrective actions approved by Montana DEQ?
"Commence construction, alteration, extension, or operation of a system of water supply or water distribution that is intended to be used as a public water supply system . . .before the person submits to the department necessary maps, plans, and specifications for its review and the department approves those maps, plans, and specifications;…"
For more information:
Contact the appropriate Rule Manager for Assistance, pr call DEQ PWS at (406) 444-4400.
