United States
Environmental Protection
Agency
Nitrate Monitoring Requirements
Community and Non Community Water Systems
What if my system is new and has never sampled for nitrate?
If your system is new and has never sampled for nitrate before, contact your primacy agency. You must conduct initial sampling to determine
whether your system is in compliance with the MCL.
Routine Monitoring: Sampling must be completed at every entry point to the distribution system
Sample result at entry point is
less than 5 mg/L (as N):
Sample result at entry point is at
or above 5 mg/L (as N) but at or
below 10 mg/L (as N):
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Sample result at entry point
is at or above 10 mg/L (as N):
Continue to sample once per year
at that entry point.
Besides sampling, what else are
we required to do?
There are also requirements on what you report
to the primacy agency every month, and require-
ments on how and when to notify your customers if
you have a violation. Contact your primacy agency
to make sure you are providing them with all the
information that is required.
Where can I find more information on
Nitrate monitoring?
You can find more information on nitrate monitoring
by calling EPA's Safe Drinking Water Hotline at:
1.800.426.4791 or by contacting your primacy agency.
Starting the next quarter, begin quarterly
sampling at that entry point.
How can I go back to
sampling once per year?
Surface water systems and systems designated by
the primacy agency as being underthe direct influ-
ence of surface water can return to annual moni-
toring after 4 consecutive quarters of samples that
are less than 5 mg/L (as N). Ground water systems
can return to annual monitoring after 4 consecutive
quarters of samples that are reliably and consis-
tently below the MCL, as defined by the primacy
agency.
Once you return to annual monitoring, take annual
samples in the quarter during which you had the
highest nitrate result during quarterly monitoring.
Take a confirmation sample at that entry point
within 24 hours after being told about the sample
result or immediately notify your customers.
How do I know if my system is in violation of the MCL?
•The nitrate MCL is 10 mg/L (as N).To see if you are in violation, you must
calculate the mean of the original nitrate sample result and the confirma-
tion sample (add the two together and divide the sum by two).
• If the mean of the original sample result and confirmation sample is above
the MCL, your system is in violation of the MCL.
• If the mean of the original sample result and confirmation sample is 10
mg/L (as N) or less; your system is not in violation of the MCL.
Example: The original sample is 11 mg/L and the confirmation sample is 13
mg/L.
11 + 13 = 24
24/2 = 12 mg/L
This result is above 10 mg/L (the MCL).
This is an MCLviolation.
Primacy Agency.
(contact name and phone number)
Office of Water (4606M)
EPA816-F-08-008
www.epa.gov/safewater
January, 2008
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