EPA
United States
Environmental Protection
Agency
Surface Water Treatment Rules Monitoring Requirements (SWTR/LT1ESWTR)
Unfiltered Systems Serving <10,000 People
1. RESIDUAL DISINFECTANT
Location
Entry Point to the
Distribution System
In the Distribution
System
Frequency
Continuously monitor
the residual disinfectant
concentration at the
entry point(s) to the
distribution system.
If monitoring equipment
fails, you can take grab
samples every 4 hours
instead, but for no more
than 5 working days.
Monitor the residual
disinfectant concentra-
tion in the distribution
system at the same time
and place as you take
total coliform samples.
Details
The concentration
cannot be less than 0.2
mg/Lfor more than 4
hours.
Record and report to
your primacy agency
the lowest daily value.
Residual disinfectant
concentration must be
detected in at least 95%
of all samples taken
every month, for any 2
consecutive months.
Can I perform grab sampling instead of continuous
disinfectant residual monitoring?
Systems serving 3,300 or fewer people can take grab samples
instead of providing continuous monitoring. Contact your pri-
macy agency for more information.
Do I have to monitor the disinfectant residual in the
distribution system?
You can measure the heterotrophic bacteria concentration
instead. A heterotrophic bacteria concentration of less than or
equal to 500 cfu/mL, measured as heterotrophic plate count, is
considered a detectable residual disinfectant.
2. SOURCE WATER TURBIDITY AND COLIFORM DENSITY
(MONITORING TO CONTINUE MEETING THE FILTRATION AVOIDANCE CRITERIA)
Unfiltered
System Type
Serving < 500 people,
turbidity <1 NTU
Serving 501-3,300
people, turbidity
<1 NTU
3,301-10,000 people,
turbidity <1 NTU
All systems with daily
turbidity >1 NTU
Source Water
Turbidity
Collect grab samples once every
4 hours
Turbidity must be < 5 NTU
You may substitute continuous
monitoring to meet the turbidity goals
Minimum Number of Representative Source Water
Total or Fecal Coliform Density Measurements
1 sample every week
2 samples every week
3 samples every week
At least one sample within 24 hours of each
daily turbidity result that is > 1 NTU
1 Continue to monitor residual disinfectant levels at the entry point(s) to the distribution system
and within the distribution system (see details in the "Residual Disinfection" section). You must
monitor and calculate inactivation at the entry point(s). Contact your primacy agencyfor more
information on these requirements.
1 Monitor any activities identified in your watershed control program that may negatively affect
your source water quality. Work with your primacy agency to meet these requirements.
Besides sampling, what else are we required
to do?
There are requirements on what you must report to your
primacy agency by the tenth day of the following month and
requirements on how and when to notify your customers if
you have a violation. In addition to monitoring and reporting
requirements,there are disinfection and watershed control
program requirements. Contact your primacy agency if
have any questions regarding these requirements.
] control
cyifyou
/ intend to make a change in my treatment
process. Do I need to complete a disinfection profile?
A disinfection profile and benchmark is required if you
make a significant change to your treatment process. Sig-
nificant changes include: changing the point at which you
disinfect, changing the type of disinfectant you use, chang-
ing the disinfectant process, and any other changes that
your primacy agency considers "significant." Consult your
primacy agency before you make any treatment changes.
Where can I find more information on
these requirements?
You can find more information on these requirements
by visiting EPA's website on microbial and disinfection
byproduct rules atwww.epa.gov/safewater/disinfec-
tion, contacting your primacy agency, or by calling
EPA's Safe Drinking Water Hotline at: 1.800.426.4791.
Primacy Agency.
(contact name and phone number)
Off ice of Water (4606M)
EPA 816-F-08-003 www.epa.gov/safewater
January, 2008
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