[Code of Federal Regulations]
[Title 40, Volume 20]
[Revised as of July 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR141.30]

[Page 390-393]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 141_NATIONAL PRIMARY DRINKING WATER REGULATIONS--Table of Contents
 
            Subpart C_Monitoring and Analytical Requirements
 
Sec.  141.30  Total trihalomethanes sampling, analytical and other requirements.

    (a) Community water system which serve a population of 10,000 or 
more individuals and which add a disinfectant (oxidant) to the water in 
any part of the drinking water treatment process shall analyze for total 
trihalomethanes in accordance with this section. For systems serving 
75,000 or more individuals, sampling and analyses shall begin not later 
than 1 year after the date of promulgation of this regulation. For 
systems serving 10,000 to 74,999 individuals, sampling and analyses 
shall begin not later than 3 years after the date of promulgation of 
this regulation. For the purpose of this section, the minimum number of 
samples required to be taken by the system shall be based on the number 
of treatment plants used by the system, except that multiple wells 
drawing raw water from a single aquifer may, with the State approval, be 
considered one treatment plant for determining the minimum number of 
samples. All samples taken within an established frequency shall be 
collected within a 24-hour period.
    (b)(1) For all community water systems utilizing surface water 
sources in whole or in part, and for all community water systems 
utilizing only ground water sources that have not been determined by the 
State to qualify for the monitoring requirements of paragraph (c) of 
this section, analyses for total trihalomethanes shall be performed at 
quarterly intervals on at least four water samples for each treatment 
plant used by the system. At least 25 percent of the samples shall be 
taken at locations within the distribution system reflecting the maximum 
residence time of the water in the system. The remaining 75 percent 
shall be taken at representative locations in the distribution system, 
taking into account number of persons served, different sources of water 
and different treatment methods employed. The results of all analyses 
per quarter shall be arithmetically averaged and reported to the State 
within 30 days of the system's receipt of such results. Results shall 
also be reported to EPA until such monitoring requirements have been 
adopted by the State. All samples collected shall be used in the 
computation of the average, unless the analytical results are 
invalidated for technical reasons. Sampling and analyses shall be 
conducted in accordance with the methods listed in paragraph (e) of this 
section.

[[Page 391]]

    (2) Upon the written request of a community water system, the 
monitoring frequency required by paragraph (b)(1) of this section may be 
reduced by the State to a minimum of one sample analyzed for TTHMs per 
quarter taken at a point in the distribution system reflecting the 
maximum residence time of the water in the system, upon a written 
determination by the State that the data from at least 1 year of 
monitoring in accordance with paragraph (b)(1) of this section and local 
conditions demonstrate that total trihalomethane concentrations will be 
consistently below the maximum contaminant level.
    (3) If at any time during which the reduced monitoring frequency 
prescribed under this paragraph applies, the results from any analysis 
exceed 0.10 mg/l of TTHMs and such results are confirmed by at least one 
check sample taken promptly after such results are received, or if the 
system makes any significant change to its source of water or treatment 
program, the system shall immediately begin monitoring in accordance 
with the requirements of paragraph (b)(1) of this section, which 
monitoring shall continue for at least 1 year before the frequency may 
be reduced again. At the option of the State, a system's monitoring 
frequency may and should be increased above the minimum in those cases 
where it is necessary to detect variations of TTHM levels within the 
distribution system.
    (c)(1) Upon written request to the State, a community water system 
utilizing only ground water sources may seek to have the monitoring 
frequency required by paragraph (b)(1) of this section reduced to a 
minimum of one sample for maximum TTHM potential per year for each 
treatment plant used by the system taken at a point in the distribution 
system reflecting maximum residence time of the water in the system. The 
system shall submit the results of at least one sample for maximum TTHM 
potential using the procedure specified in paragraph (g) of this 
section. A sample must be analyzed from each treatment plant used by the 
system and be taken at a point in the distribution system reflecting the 
maximum residence time of the water in the system. The system's 
monitoring frequency may only be reduced upon a written determination by 
the State that, based upon the data submitted by the system, the system 
has a maximum TTHM potential of less than 0.10 mg/l and that, based upon 
an assessment of the local conditions of the system, the system is not 
likely to approach or exceed the maximum contaminant level for total 
TTHMs. The results of all analyses shall be reported to the State within 
30 days of the system's receipt of such results. Results shall also be 
reported to EPA until such monitoring requirements have been adopted by 
the State. All samples collected shall be used for determining whether 
the system must comply with the monitoring requirements of paragraph (b) 
of this section, unless the analytical results are invalidated for 
technical reasons. Sampling and analyses shall be conducted in 
accordance with the methods listed in paragraph (e) of this section.
    (2) If at any time during which the reduced monitoring frequency 
prescribed under paragraph (c)(1) of this section applies, the results 
from any analysis taken by the system for maximum TTHM potential are 
equal to or greater than 0.10 mg/l, and such results are confirmed by at 
least one check sample taken promptly after such results are received, 
the system shall immediately begin monitoring in accordance with the 
requirements of paragraph (b) of this section and such monitoring shall 
continue for at least one year before the frequency may be reduced 
again. In the event of any significant change to the system's raw water 
or treatment program, the system shall immediately analyze an additional 
sample for maximum TTHM potential taken at a point in the distribution 
system reflecting maximum residence time of the water in the system for 
the purpose of determining whether the system must comply with the 
monitoring requirements of paragraph (b) of this section. At the option 
of the State, monitoring frequencies may and should be increased above 
the minimum in those cases where this is necessary to detect variation 
of TTHM levels within the distribution system.
    (d) Compliance with Sec.  141.12 shall be determined based on a 
running annual

[[Page 392]]

average of quarterly samples collected by the system as prescribed in 
paragraph (b)(1) or (2) of this section. If the average of samples 
covering any 12 month period exceeds the Maximum Contaminant Level, the 
supplier of water shall report to the State pursuant to Sec.  141.31 and 
notify the public pursuant to subpart Q. Monitoring after public 
notification shall be at a frequency designated by the State and shall 
continue until a monitoring schedule as a condition to a variance, 
exemption or enforcement action shall become effective.
    (e) Sampling and analyses made pursuant to this section shall be 
conducted by one of the total trihalomethanes methods as directed in 
Sec.  141.24(e), and the Technical Notes on Drinking Water Methods, EPA-
600/R-94-173, October 1994, which is available from NTIS, PB-104766, or 
in Sec.  141.131(b). Samples for TTHM shall be dechlorinated upon 
collection to prevent further production of trihalomethanes, according 
to the procedures described in the methods, except acidification is not 
required if only THMs or TTHMs are to be determined. Samples for maximum 
TTHM potential should not be dechlorinated or acidified, and should be 
held for seven days at 25 [deg]C (or above) prior to analysis.
    (f) Before a community water system makes any significant 
modifications to its existing treatment process for the purposes of 
achieving compliance with Sec.  141.12, such system must submit and 
obtain State approval of a detailed plan setting forth its proposed 
modification and those safeguards that it will implement to ensure that 
the bacteriological quality of the drinking water served by such system 
will not be adversely affected by such modification. Each system shall 
comply with the provisions set forth in the State-approved plan. At a 
minimum, a State approved plan shall require the system modifying its 
disinfection practice to:
    (1) Evaluate the water system for sanitary defects and evaluate the 
source water for biological quality;
    (2) Evaluate its existing treatment practices and consider 
improvements that will minimize disinfectant demand and optimize 
finished water quality throughout the distribution system;
    (3) Provide baseline water quality survey data of the distribution 
system. Such data should include the results from monitoring for 
coliform and fecal coliform bacteria, fecal streptococci, standard plate 
counts at 35 [deg]C and 20 [deg]C, phosphate, ammonia nitrogen and total 
organic carbon. Virus studies should be required where source waters are 
heavily contaminated with sewage effluent;
    (4) Conduct additional monitoring to assure continued maintenance of 
optimal biological quality in finished water, for example, when 
chloramines are introduced as disinfectants or when pre-chlorination is 
being discontinued. Additional monitoring should also be required by the 
State for chlorate, chlorite and chlorine dioxide when chlorine dioxide 
is used. Standard plate count analyses should also be required by the 
State as appropriate before and after any modifications;
    (5) Consider inclusion in the plan of provisions to maintain an 
active disinfectant residual throughout the distribution system at all 
times during and after the modification.
    (g) The water sample for determination of maximum total 
trihalomethane potential is taken from a point in the distribution 
system that reflects maximum residence time. Procedures for sample 
collection and handling are given in the methods. No reducing agent is 
added to ``quench'' the chemical reaction producing THMs at the time of 
sample collection. The intent is to permit the level of THM precursors 
to be depleted and the concentration of THMs to be maximized for the 
supply being tested. Four experimental parameters affecting maximum THM 
production are pH, temperature, reaction time and the presence of a 
disinfectant residual. These parameters are dealt with as follows: 
Measure the disinfectant residual at the selected sampling point. 
Proceed only if a measurable disinfectant residual is present. Collect 
triplicate 40 ml water samples at the pH prevailing at the time of 
sampling, and prepare a method blank according to the methods. Seal and 
store these samples together for seven days at 25 [deg]C or above. After 
this time period,

[[Page 393]]

open one of the sample containers and check for disinfectant residual. 
Absence of a disinfectant residual invalidates the sample for further 
analysis. Once a disinfectant residual has been demonstrated, open 
another of the sealed samples and determine total THM concentration 
using an approved analytical method.
    (h) The requirements in paragraphs (a) through (g) of this section 
apply to subpart H community water systems which serve a population of 
10,000 or more until December 31, 2001. The requirements in paragraphs 
(a) through (g) of this section apply to community water systems which 
use only ground water not under the direct influence of surface water 
that add a disinfectant (oxidant) in any part of the treatment process 
and serve a population of 10,000 or more until December 31, 2003. After 
December 31, 2003, this section is no longer applicable.

[44 FR 68641, Nov. 29, 1979, as amended at 45 FR 15545, 15547, Mar. 11, 
1980; 58 FR 41345, Aug. 3, 1993; 59 FR 62469, Dec. 5, 1994; 60 FR 34085, 
June 29, 1995; 63 FR 69464, Dec. 16, 1998; 65 FR 26022, May 4, 2000; 66 
FR 3776, Jan. 16, 2001]