California Code of Regulations
Title 22 - Social Security
Division 4 - Environmental Health
Chapter 15 - Domestic Water Quality and Monitoring Regulations
Article 3 - Primary Standards-Bacteriological Quality
Section 64424 - Repeat Sampling
Current through Register 2024 Notice Reg. No. 38, September 20, 2024
(a) If a routine sample is total coliform-positive, a public water system shall collect a repeat sample set as described in paragraph (1) within 24 hours of being notified of the positive result. The repeat samples shall all be collected within the same 24-hour time period. A single service connection system may submit a request to the State Board to allow the collection of the repeat sample set over a three-day period.
(b) Unless the condition for using alternative sampling locations or dual purpose sampling locations in Table 64424-A or B, respectively, is met, when collecting the repeat sample set, a public water system shall collect at least one repeat sample from the sampling tap where the original total coliform-positive sample was taken. Other repeat samples shall be collected within five service connections upstream or downstream of the original site. At least one sample shall be from upstream and one from downstream unless there is no upstream and/or downstream service connection. If a total coliform-positive sample is at the end of the distribution system, or one service connection away from the end of the distribution system, the system shall still take all required repeat samples. The system may submit a request to the State Board to use an alternative sampling location in lieu of the requirement to collect at least one repeat sample upstream or downstream of the original sampling site. Except as provided in Table 64424-B, a system required to conduct triggered source water monitoring under 40 CFR 141.402(a), which is incorporated by reference under Section 64430, shall take groundwater (not GWUDI) source sample(s) in addition to repeat samples required under this section. If monitoring pursuant to Table 64424-B and in violation of the E. coli MCL, the system shall comply with the additional Ground Water Rule requirements in Table 64424-C.
Table 64424-A
Alternative Sampling Locations
| Type of Water System | Sampling Requirement |
| Public water system | The system may propose repeat monitoring locations to the State Board that the system believes to be representative of a pathway for contamination of the distribution system. The system may elect to specify either alternative fixed locations or criteria for selecting repeat sampling sites on a situational basis in a standard operating procedure (SOP) in its bacteriological sample siting plan. The system shall design its SOP to focus the repeat samples at locations that best verify and determine the extent of potential contamination of the distribution system area based on specific situations. |
Table 64424-B
Dual Purpose Sampling Locations
| Type of Water System | Sampling Requirement |
| Public water system using only a single groundwater (not GWUDI) well, serving 1,000 or fewer persons, and required to conduct triggered source water monitoring under 40 CFR 141.402(a), which is incorporated by reference under Section 64430 | The system may propose repeat sampling locations to the State Board that differentiate potential source water and distribution system contamination (e.g., by sampling at entry points to the distribution system). The system may submit a request to the State Board to take one of its repeat samples at the monitoring location required for triggered source water monitoring (dual purpose sampling) under 40 CFR 141.402(a), which is incorporated by reference under Section 64430, if the system demonstrates to the State Board that the bacteriological sample siting plan remains representative of water quality in the distribution system. If approved by the State Board, the system may use that sample result to meet the monitoring requirements in both 40 CFR 141.402(a), which is incorporated by reference under Section 64430, and this section. |
Table 64424-C
Additional Ground Water Rule Requirements
| Results of Dual Purpose Sampling that Constitutes an E. coli MCL Violation | Public Water System Action Required |
| A repeat sample taken at the monitoring location required for triggered source water monitoring is E. coli -positive | The system shall comply with 40 CFR 141.402(a)(3), which is incorporated by reference under Section 64430. If the system takes more than one repeat sample at the monitoring location required for triggered source water monitoring, the system may reduce the number of additional source water samples required under 40 CFR 141.402(a)(3), which is incorporated by reference under Section 64430, by the number of repeat samples taken at that location that were not E. coli -positive. |
| A system takes more than one repeat sample at the monitoring location required for triggered source water monitoring and more than one repeat sample is E. coli -positive | The system shall comply with 40 CFR 141.403(a)(1), which is incorporated by reference under Section 64430. |
| All repeat samples taken at the monitoring location required for triggered source water monitoring are E. coli -negative and a repeat sample taken at a monitoring location other than the one required for triggered source water monitoring is E. coli - positive | The system is not required to comply with 40 CFR 141.402(a)(3), which is incorporated by reference under Section 64430. |
(c) If one or more samples in the repeat sample set is total coliform-positive, a public water system shall collect and have analyzed an additional set of repeat samples as specified in subsections (a) and (b). The system shall repeat this process until either no total coliforms are detected in one complete repeat sample set or the system determines that a coliform treatment technique trigger specified in Section 64426.7 has been exceeded as a result of a repeat sample being total coliform-positive and notifies the State Board by the end of the day on which this is determined. If a treatment technique trigger identified in Section 64426.7 is exceeded as a result of a routine sample being total coliform-positive, the system is required to conduct only one round of repeat monitoring for each total coliform-positive routine sample.
(d) A public water system in violation of the repeat sample monitoring requirements of this section shall notify the State Board within 10 days after it learns of the violation and notify the public pursuant to Sections 64463, 64463.7, and 64465.
(e) A public water system in violation of the reporting requirement in subsection (d) to notify the State Board shall notify the public pursuant to Sections 64463, 64463.7, and 64465.
1. New
section filed 7-1-92; operative 7-31-92 (Register 92, No. 28).
2.
Amendment of subsection (d) filed 9-8-94 as an emergency; operative 9-8-94
(Register 94, No. 36). A Certificate of Compliance must be transmitted to OAL
by 1-6-95 or emergency language will be repealed by operation of law on the
following day.
3. Amendment of subsection (d) refiled 1-3-95 as an
emergency; operative 1-3-95 (Register 95, No. 1). A Certificate of Compliance
must be transmitted to OAL by 5-3-95 or emergency language will be repealed by
operation of law on the following day.
4. Amendment of subsection
(d) refiled 4-26-95 as an emergency; operative 4-26-95 (Register 95, No. 17). A
Certificate of Compliance must be transmitted to OAL by 8-24-95 or emergency
language will be repealed by operation of law on the following
day.
5. Certificate of Compliance as to 4-26-95 order transmitted to
OAL 5-5-95 and filed 6-19-95 (Register 95, No. 25).
6. Change
without regulatory effect amending subsections (a), (a)(2) and (c)-(d)(2) and
amending NOTE filed 6-2-2015 pursuant to section
100, title 1, California Code of
Regulations (Register 2015, No. 23).
7. Amendment of section, new
Tables 64424-A through 64424-C and amendment of NOTE filed 5-28-2021; operative
7-1-2021 (Register 2021, No. 22).
Note: Authority cited: Sections 116271 and 116375, Health and Safety Code. Reference: Sections 116375 and 116450, Health and Safety Code.
