Section 64423 - Routine Sampling(a) A public water system shall collect routine bacteriological water samples as follows: (1) The minimum number of samples for community water systems shall be based on the known population served or the total number of service connections, whichever results in the greater number of samples, as shown in Table 64423-A;(2) The minimum number of samples for nontransient-noncommunity water systems shall be based on the known population served as shown in Table 64423-A during those months when the system is operating;(3) The minimum number of samples for transient-noncommunity water systems using only groundwater (not GWUDI) and serving 1000 or fewer persons a month shall be one in each calendar quarter during which the system provides water to the public;(4) The minimum number of samples for transient-noncommunity water systems using groundwater (not GWUDI) and serving more than 1000 persons during any month shall be based on the known population served as shown in Table 64423-A. For any quarter the system serves 1000 or fewer persons in each month and uses only groundwater (not GWUDI), and if the criteria in subsections (c)(2)(A) and (B) are met, the system may submit a request to the State Board to monitor in accordance with paragraph (3). The request shall include: (A) Historical data that demonstrates the system has served 1000 or fewer persons in each month of the calendar quarter for which the request is being made; and(B) A revised bacteriological sample siting plan with an updated sampling schedule;(5) The minimum number of samples for transient-noncommunity water systems using approved surface water shall be based on the population served as shown in Table 64423-A. A system using groundwater under the direct influence of surface water shall begin monitoring at this frequency by the end of the sixth month after the State Board has designated the source to be approved surface water;(6) The minimum number of samples for seasonal systems, and in lieu of paragraphs (2) through (5), shall be based on the population served as shown in Table 64423-A during those months when the system is operating;(7) Samples shall be collected at regular time intervals throughout the month, except that a system using only groundwater (not GWUDI) which serves 4,900 persons or fewer may collect all required samples on a single day if they are taken from different sites;(8) At least the minimum number of samples shall be taken even if the system has had an E. coli MCL violation or has exceeded the coliform treatment technique triggers in Section 64426.7; and(9) More than the minimum number of samples may be taken provided the samples are included in the bacteriological sample siting plan developed pursuant to Section 64422.(b) In addition to the minimum sampling requirements, all public water systems using approved surface water which do not practice filtration in compliance with Sections 64650 through 64666, shall collect a minimum of one sample before or at the first service connection each day during which the turbidity level of the source water exceeds 1 NTU. The sample shall be collected within 24 hours of the first exceedance and shall be analyzed for total coliforms. If the system is unable to collect and/or analyze the sample within the 24-hour time period because of extenuating circumstances beyond its control, the system shall notify the State Board within the 24-hour time period, submit a request to the State Board for an extension, and comply with an alternative sample collection schedule specified by the State Board. Sample results shall be included in determining if the coliform treatment technique trigger in Section 64426.7 has been exceeded.(c) A transient-noncommunity water system monitoring pursuant to subsection (a)(3): (1) Shall, in the month following the occurrence of any of the following events, increase monitoring to one sample each month: (A) The system triggers a Level 2 assessment or two Level 1 assessments in a rolling 12-month period;(B) The system has an E. coli MCL violation;(C) The system has a coliform treatment technique violation; or(D) The system has two bacteriological monitoring violations or one bacteriological monitoring violation and one Level 1 assessment in a rolling 12-month period. For purposes of this subparagraph, failure to conduct bacteriological monitoring under Section 64423, 64423.1, 64424, or 64425 is a bacteriological monitoring violation;(2) If monitoring pursuant to paragraph (1) and if all the following criteria are met, may submit a request to the State Board to return to routine monitoring pursuant to subsection (a)(3): (A) Within the last 12 consecutive months, the system shall have a completed sanitary survey, site visit, or voluntary Level 2 assessment by the State Board and be determined by the State Board to be free of sanitary defects and have a protected water source; and(B) Immediately prior to the request, the system shall have a clean compliance history for a minimum of 12 consecutive months; and(3) Shall, in the month following one or more total coliform-positive samples (with or without a Level 1 treatment technique trigger exceedance), collect at least three routine samples. The system may either collect samples at regular time intervals throughout the month or may collect all required routine samples on a single day if samples are taken from different sites. If the system stops supplying water during the month following the total coliform-positive(s), at least three routine samples shall be collected during the first month the system resumes operation.(d) A public water system in violation of the routine 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. Table 64423-A
Minimum Number of Routine Total Coliform Samples
| Monthly Population Served1 | Service Connections | Minimum Number of Samples Per Month |
| 25 to 1000 | 15 to 400 | 1 |
| 1,001 to 2,500 | 401 to 890 | 2 |
| 2,501 to 3,300 | 891 to 1,180 | 3 |
| 3,301 to 4,100 | 1,181 to 1,460 | 4 |
| 4,101 to 4,900 | 1,461 to 1,750 | 5 |
| 4,901 to 5,800 | 1,751 to 2,100 | 6 |
| 5,801 to 6,700 | 2,101 to 2,400 | 7 |
| 6,701 to 7,600 | 2,401 to 2,700 | 8 |
| 7,601 to 8,500 | 2,701 to 3,000 | 9 |
| 8,501 to 12,900 | 3,001 to 4,600 | 10 |
| 12,901 to 17,200 | 4,601 to 6,100 | 15 |
| 17,201 to 21,500 | 6,101 to 7,700 | 20 |
| 21,501 to 25,000 | 7,701 to 8,900 | 25 |
| 25,001 to 33,000 | 8,901 to 11,800 | 30 |
| 33,001 to 41,000 | 11,801 to 14,600 | 40 |
| 41,001 to 50,000 | 14,601 to 17,900 | 50 |
| 50,001 to 59,000 | 17,901 to 21,100 | 60 |
| 59,001 to 70,000 | 21,101 to 25,000 | 70 |
| 70,001 to 83,000 | 25,001 to 29,600 | 80 |
| 83,001 to 96,000 | 29,601 to 34,300 | 90 |
| 96,001 to 130,000 | 34,301 to 46,400 | 100 |
| 130,001 to 220,000 | 46,401 to 78,600 | 120 |
| 220,001 to 320,000 | 78,601 to 114,300 | 150 |
| 320,001 to 450,000 | 114,301 to 160,700 | 180 |
| 450,001 to 600,000 | 160,701 to 214,300 | 210 |
| 600,001 to 780,000 | 214,301 to 278,600 | 240 |
| 780,001 to 970,000 | 278,601 to 346,400 | 270 |
| 970,001 to 1,230,000 | 346,401 to 439,300 | 300 |
| 1,230,001 to 1,520,000 | 439,301 to 542,900 | 330 |
| 1,520,001 to 1,850,000 | 542,901 to 660,700 | 360 |
| 1,850,001 to 2,270,000 | 660,701 to 810,700 | 390 |
| 2,270,001 to 3,020,000 | 810,701 to 1,078,600 | 420 |
| 3,020,001 to 3,960,000 | 1,078,601 to 1,414,300 | 450 |
| 3,960,001 or more | 1,414,301 or more | 480 |
1 For a transient-noncommunity water system, monthly population served shall be based on the average number of persons served per day in a month.
Cal. Code Regs. Tit. 22, § 64423
1. Repealer and new section filed 7-1-92; operative 7-31-92 (Register 92, No. 28).
2. Amendment of subsections (a)-(b) 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 subsections (a)-(b) 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 subsections (a)-(b) 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)(1)-(2), (a)(4)-(5) and (b) 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 and 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, 116385, 116400 and 116450, Health and Safety Code.
1. Repealer and new section filed 7-1-92; operative 7-31-92 (Register 92, No. 28).
2. Amendment of subsections (a)-(b) 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 subsections (a)-(b) 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 subsections (a)-(b) 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)(1)-(2), (a)(4)-(5) and (b) 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 and Note filed 5-28-2021; operative 7/1/2021 (Register 2021, No. 22).