Chapter 17 is where I live professionally. It is the California implementation of every Surface Water Treatment Rule, from the original SWTR through LT2 and the FBRR. If you operate a surface water plant in California, the turbidity limits you monitor, the CT calculations you run, and the filter performance you track are all governed by this chapter.
If you have read the SWTR and IESWTR/LT1/LT2 study guides on this site, the federal requirements will be familiar. This guide focuses on how California implements those requirements within Title 22, including the specific section numbers the exam references, the monitoring frequencies as structured in California's framework, and the design standards for new plants.
What Does Chapter 17 Cover?
Chapter 17 spans sections 64650 through 64666 and implements all five federal surface water treatment rules in California: the SWTR, IESWTR, LT1ESWTR, LT2ESWTR, and FBRR. It applies to all public water systems using surface water or groundwater under the direct influence of surface water (GWUDI).
The chapter is organized into four articles covering definitions, treatment requirements, monitoring, and design standards. The LT2ESWTR is incorporated by reference under section 64650(f).
What Are the California Turbidity Standards?
These are the numbers you operate under every shift. They apply to the combined filter effluent and vary by filtration type.
| Filter Type | 95th Percentile | Maximum |
|---|---|---|
| Conventional/Direct | 0.3 NTU or less in 95% or more of monthly measurements | Never exceed 1 NTU for more than 1 continuous hour or 8 consecutive hours |
| Diatomaceous Earth | 0.5 NTU or less in 95% or more of measurements | Never exceed 5.0 NTU |
| Slow Sand | 1.0 NTU or less in 95% or more of measurements | Never exceed 5.0 NTU |
For systems serving 10,000 or more, continuous turbidity monitoring on each individual filter is required. Any individual filter exceeding 1.0 NTU must be reported. This prevents a single poorly performing filter from being masked when its effluent blends with better-performing filters.
The design goal for new conventional, direct, and DE filtration plants is 0.2 NTU average daily effluent turbidity. That is a goal, not an enforceable limit, but it signals where the regulatory expectation is heading.
The 0.3 NTU standard applies to the combined filter effluent at the 95th percentile of all measurements taken during the month. It does not mean every individual reading must be at or below 0.3 NTU. It means 95% of them must be. The exam tests whether you understand this distinction.
What Are the Log Removal Requirements?
Chapter 17 requires multibarrier treatment (filtration plus disinfection) between raw water and the first customer. The total log removal requirements are the same as the federal rules.
| Pathogen | Total Removal Required |
|---|---|
| Giardia lamblia | 3-log (99.9%) |
| Viruses | 4-log (99.99%) |
| Cryptosporidium | 2-log (99%) through filtration |
These totals are achieved through a combination of filtration credit and disinfection CT. The specific filtration credits by filter type are covered in the SWTR study guide.
What Are the Disinfection Residual Requirements?
The disinfection requirements mirror the federal SWTR framework.
At the entry point to the distribution system, the residual must be 0.2 mg/L or higher. It may not drop below 0.2 mg/L for more than 4 hours. There are no exemptions from this requirement.
In the distribution system, a detectable residual must be present in at least 95% of monthly samples. An HPC result of 500 CFU/mL or less is accepted as an equivalent at sample points with no detectable residual. Distribution residual samples must be collected at the same time and place as total coliform samples.
What Monitoring Is Required?
Chapter 17 specifies monitoring at multiple points in the treatment process.
Raw water: Turbidity at least once per day. Total coliform and fecal coliform or E. coli density at least once per month.
Settled water: Turbidity at least once per day for conventional plants.
Combined filter effluent: Turbidity continuously or at least every 4 hours.
Individual filter effluent: Continuous monitoring required for systems serving 10,000 or more. Report any individual filter exceeding 1.0 NTU.
Disinfection: CT calculations using residual at the measurement point and contact time at peak flow. Residual monitoring at the entry point. Distribution residual at the same time and place as coliform samples.
Disinfection profiling requires systems to retain profile data and submit it to the State Board before making any changes to disinfection practices. This ensures that changes intended to reduce DBPs do not inadvertently reduce pathogen inactivation below safe levels.
The exam may ask about the relationship between disinfection profiling and the DBP rules. The connection is direct: operators who want to reduce disinfectant dose to lower DBPs must first demonstrate through a disinfection profile that the reduction will not compromise microbial protection. Profile first, then change.
What Are the LT2 Bin Classification Requirements in California?
California incorporates the LT2ESWTR by reference under section 64650(f). The bin classification system, source water monitoring, and microbial toolbox requirements are the same as the federal rule, covered in detail in the IESWTR/LT1/LT2 study guide.
The key California-specific detail is the E. coli trigger for source water assessment: 100 E. coli per 100 mL for both lake/reservoir and flowing stream sources.
Uncovered finished water reservoirs must be covered or the water leaving them must be treated to achieve 4-log virus, 3-log Giardia, and 2-log Cryptosporidium inactivation.
What Are the Filtration Avoidance Criteria?
Systems may avoid installing filtration only if all of the following criteria are met simultaneously. Failing any single criterion requires filtration installation within 18 months.
Fecal coliform must be 20 per 100 mL or less (or total coliform 100 per 100 mL or less) in at least 90% of samples over any 6-month period. Source water turbidity must not exceed 5 NTU. The system must maintain a watershed control program and complete an annual on-site inspection. No waterborne disease outbreak can be linked to the system. E. coli MCL compliance must be maintained in at least 11 of the last 12 months. DBP compliance must be current.
Filtration avoidance is all-or-nothing. Meeting five of six criteria is not sufficient. The 18-month installation deadline does not include extensions.
What Are the Design Standards for New Plants?
Article 4 (sections 64658 through 64659) establishes design standards for new surface water treatment plants.
New conventional, direct, and DE filtration plants must be designed to achieve an average daily turbidity of 0.2 NTU in the combined filter effluent. Plants must be free of sanitary hazards and include backflow protection.
Reliability requirements under section 64659 include standby power, redundant treatment capacity, and emergency provisions. These ensure that treatment continues during equipment failures and power outages.
Chapter 17 is the California framework for surface water treatment. If you operate a surface water plant in this state, the turbidity standards, CT calculations, and monitoring requirements in this chapter govern your daily operations. The exam tests these numbers directly, and knowing the California-specific implementation details gives you an advantage over general study materials.
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This guide is for educational purposes and reflects California regulations as of April 2026. Always verify current requirements with your state regulatory agency.
Frequently Asked Questions
What are the California turbidity standards for conventional filtration?
California requires conventional and direct filtration plants to maintain combined filter effluent turbidity of 0.3 NTU or less in at least 95% of measurements each month. Turbidity shall not exceed 1 NTU for more than 1 continuous hour or 8 consecutive hours. Individual filter monitoring is required for systems serving 10,000 or more, with any filter exceeding 1.0 NTU reported.
What monitoring is required for individual filters under Chapter 17?
Systems serving 10,000 or more must continuously monitor turbidity on each individual filter. Any individual filter exceeding 1.0 NTU must be reported. This requirement ensures a single poorly performing filter is not masked by blending with other filter effluents in the combined measurement.
What is the design goal for new treatment plants in California?
New conventional, direct, and diatomaceous earth filtration plants must be designed to achieve an average daily turbidity of 0.2 NTU in the combined filter effluent. Plants must also be free of sanitary hazards, include backflow protection, and meet reliability requirements including standby power and redundant treatment capacity.