[Code of Federal Regulations]

[Title 40, Volume 22]

[Revised as of July 1, 2005]

From the U.S. Government Printing Office via GPO Access

[CITE: 40CFR141.30]



[Page 389-391]

 

                   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.

    (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



[[Page 390]]



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 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



[[Page 391]]



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, 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]