The State Water Board’s Division of Drinking Water (DDW) plays a critical role in ensuring the safety and reliability of drinking water for communities across the state. With regulatory authority over public drinking water systems, the DDW is responsible for enforcing both state and federal drinking water standards under the Safe Drinking Water Act. This includes overseeing water quality monitoring, permitting, and compliance for thousands of water systems, ranging from small rural providers to large urban utilities. The division also works to protect public health by addressing emerging contaminants, supporting infrastructure improvements, and providing technical assistance to water systems.
The November meeting of the California Water Quality Monitoring Council included several presentations from staff from the State Water Board’s Division of Drinking Water. These presentations provided an overview of the division’s role, explored the complexities of drinking water data, and addressed the challenges posed by wildfires to the safety and reliability of drinking water systems. This article focuses on the Division of Drinking Water, while part two will delve into the impacts of wildfires on drinking water safety and reliability.
The Division of Drinking Water, originally established in 1915 as the Bureau of Sanitary Engineering under the Department of Public Health, was created in response to waterborne disease outbreaks, including a typhoid outbreak in Santa Ana.
The Division oversees public water systems, defined as those that provide water for human consumption through pipes or other constructed conveyances. These systems must have at least 15 service connections or regularly serve a minimum of 25 individuals daily for at least 60 days per year. The term “public” in this context refers to serving the public, regardless of whether the system is privately or publicly governed. For example, private water companies that provide water to the public are still classified as public water systems.
Public water systems are divided into two main categories:
- Community water systems: These include municipal water systems and large utilities that serve residential populations.
- Non-community water systems: These include systems at businesses or schools, as well as transient water systems, such as those found in state parks, roadside restaurants, or gas stations, where individuals typically visit for short periods.
This distinction is significant because community water systems are subject to comprehensive water sampling due to the long-term exposure of residents. In contrast, transient water systems are not tested for certain substances because individuals are only exposed to the water for short periods.
Certain county environmental health departments serve as designated Local Primacy Agencies (LPAs), responsible for regulating water systems with fewer than 200 connections. Examples of these counties include Contra Costa, Plumas, and Kings, among others. These counties are highlighted in blue on the slide.
State Small Water Systems (SSWS) are smaller-scale water systems that typically serve between 5 and 14 connections. While they provide drinking water, they do not meet the size thresholds required for classification as larger public water systems. These systems often supply water to rural areas, mobile home parks, or small subdivisions. County environmental health departments oversee State Small Water Systems and may also have additional regulatory requirements for domestic wells.
As part of the Safe and Affordable Funding for Equity and Resiliency (SAFER) program, the Division of Drinking Water (DDW) developed the aquifer risk map to identify potential contaminants that may be present in the groundwater used by state small water systems and domestic wells. This map is shared with county environmental health teams to provide insight into possible groundwater risks within their areas.
It is important to note that the aquifer risk map highlights contaminants that might be present in the groundwater based on available data, but it does not confirm their presence. Testing is required to verify whether these contaminants are actually present in the groundwater.
Division of Drinking Water Organization
The Division of Drinking Water (DDW) is organized into five branches, each with distinct responsibilities to ensure safe and reliable drinking water across California:
Resiliency and Data Branch: This branch focuses on data management, mapping tools, needs assessments, and the SAFER program. It includes:
- Quality Assurance Section: Ensures the accuracy, validity, and legal defensibility of data within drinking water management systems.
- SAFER Drinking Water Section: Works to provide safe, affordable, and accessible drinking water to all Californians by utilizing funding tools and collaborating with water systems and communities to address water quality issues.
Program Management Branch: This branch oversees technical operations, recycled water programs, and the Environmental Laboratory Accreditation Program (ELAP). It includes:
- Environmental Laboratory Accreditation Program (ELAP): Evaluates and accredits environmental testing laboratories.
- Technical Operations Section: Supports the development and implementation of regulations and standards to ensure an effective drinking water program and public health protection.
Field Operations Branches (Northern, Central, and Southern California): Divided into Northern, Central, and Southern California regions, these branches enforce the federal and California Safe Drinking Water Acts (SDWAs) and oversee approximately 7,300 public water systems. Responsibilities include emergency response, inspections, permitting, enforcement, reviewing water quality data, and promoting drought preparedness and water conservation. Field staff also conduct source water assessments, evaluate recycled water projects, and support water system security.
California’s public drinking water systems
The Division of Drinking Water oversees a network of approximately 7,300 public water systems across California, each playing a vital role in delivering safe drinking water to communities.
These systems break down into three main categories:
- Community water systems: Around 2,800 systems serve residential areas, ranging from massive utilities to tiny neighborhood co-ops. Notably, just 226 of these systems supply water to 33 million Californians, highlighting the scale of some of the state’s largest providers. On the other end of the spectrum, about 1,400 community systems have fewer than 100 connections, often run by small mutual water companies or local well-sharing groups.
- Non-transient water systems: Approximately 1,450 systems serve places like rural elementary schools and business parks, where people rely on the water daily but don’t live on-site.
- Transient water systems: Nearly 3,000 systems serve short-term visitors at locations such as gas stations along remote highways or state parks.
California’s water system landscape is as diverse as its geography, from sprawling urban networks to tiny rural setups, all working to keep the state hydrated.
“Once upon a time, some of these were maybe more sustainable than they are now, when there wasn’t contamination, when it was just a well and maybe a chlorinator,” said Michelle Frederick, Assistant Deputy Director, Central CA Branch, Division of Drinking Water. “But over the years, it has become harder and harder for our small water systems to meet all the regulations and to do all the monitoring. The vast majority of our violations occur in these smaller groups.”
The Division of Drinking Water has a boundary mapping tool that displays the service areas of water systems. The map uses a color-coded system: green indicates compliance, yellow signals potential risk, and red highlights systems currently in violation. While the map does not include the largest water systems, it provides valuable insights into smaller systems, helping to identify areas where compliance issues may exist.
Regulatory framework for water quality
Water quality samples are collected from two primary locations: at the water source or post-treatment, and at distribution system sampling points. The sampling location depends on the potential source of contamination. For example, if contamination is suspected from volatile organic compounds (VOCs) or groundwater, samples are typically collected at the source and, if applicable, after treatment.
Sampling at the water source and/or post-treatment includes tests for bacteriological contaminants (such as total coliform and E. coli), inorganic chemicals (like nitrate and arsenic), VOCs and semi-volatile organic compounds (SVOCs), radiological chemicals, turbidity, and disinfectants. In contrast, distribution system sampling focuses on lead, copper, and disinfection byproducts.
When drinking water systems start failing MCLs, a number of actions are taken. First, there is public notification: if there is a problem, they want people notified. The Division of Drinking Water will also take enforcement action, including issuing compliance orders and imposing fines. Larger systems are usually not out of compliance because they have a large customer base to spread the costs over. So with smaller systems, they take a softer approach, sometimes working to find funding for upgrades.
“There is a balance for us between collaboration and enforcement because we really need our water systems to proactively call us,” she said. “I don’t want to wait until they are in violation and people are drinking bad water; I want them to be comfortable calling me beforehand, so that we can really get there and fix things ahead of time.”
Drinking water quality regulation is constantly evolving, with new contaminants and regulatory standards regularly emerging. Upcoming changes include new Maximum Contaminant Levels (MCLs) and updated regulations for substances such as lead and copper, hexavalent chromium, manganese, per- and polyfluoroalkyl substances (PFAS), microplastics, and harmful algal blooms (HABs). For more detailed information and updates on regulations, visit this page.
Drinking water data: Why data is important
The Division of Drinking Water (DDW) collects extensive data to maintain a comprehensive understanding of public water systems, ensure compliance with regulatory requirements, and verify that systems are performing effectively to provide safe drinking water to the public.
This data includes chemical, physical, biological, and radiological water quality information, as well as detailed public water system data, including system characteristics, population served, service connections, and infrastructure. These insights help assess the status of each system and ensure that regulatory requirements are applied appropriately.
DDW also gathers compliance and monitoring data, including information on treatment effectiveness, violations, enforcement actions, and Consumer Confidence Reports. As new contaminants become regulated, DDW focuses on ensuring that treatment processes are functioning as intended. Additionally, the division oversees enforcement of violations and supports public reporting efforts, such as the annual Consumer Confidence Reports provided to communities.
“There’s a whole host of data that we collect in many different ways to support public water systems and ensure the people of California are protected,” said Karen Nishimoto, Section Chief, Quality Assurance.
Water quality data
Water quality monitoring frequencies are determined by regulations and are based on the characteristics of each water system. For example, community water systems, which pose higher exposure risks due to long-term use, are subject to more frequent monitoring. In contrast, non-transient or transient systems, such as gas stations or offices where people have limited exposure, have less stringent monitoring requirements under the regulatory framework.
Regulations establish baseline monitoring expectations for all systems. However, the Field Operations Branches further tailor the monitoring approach by issuing permits and including additional provisions specific to the needs and conditions of each water system. Additional permit provisions are designed to address risks and the potential for system failure. For systems with acute risks, such as elevated nitrate levels, monitoring frequencies are increased to ensure that any issues are identified and addressed promptly. Monitoring schedules also account for factors such as source variability and seasonal effects. Certain contaminants may become more prevalent during specific times of the year, prompting heightened monitoring during those periods to capture worst-case scenarios. This targeted approach helps create a robust, effective monitoring schedule tailored to each water system’s unique needs and risks.
“This is to make sure that while we have our baseline monitoring and we don’t go below that, we can go above for system-specific situations, especially where there may be complicated treatment or different combinations of different water,” said Ms. Nishimoto. “We want to make sure that the monitoring is really appropriate to understand the water that is being provided by that water system.”
The primary monitoring location for water quality is at the water source or the entry point to the distribution system. This allows for an assessment of source water quality and helps determine the necessary treatment processes. Monitoring also focuses on treatment processes and effluent from treatment plants to ensure that the water produced meets regulatory standards, that the treatment systems are functioning as intended, and that the overall treatment process is optimized.
Additional monitoring occurs within the distribution system. While most chemical monitoring is conducted at the source and treatment plants, the distribution system is monitored for bacteriological contaminants, lead and copper, disinfection byproducts, and, in specific cases such as post-fire events, benzene. This comprehensive approach ensures water quality is maintained throughout the entire system.
Submitting water quality monitoring data
Water quality monitoring data is submitted through multiple reporting methods.
- The primary method for receiving water quality data is the California Laboratory Intake Portal (CLIP), where accredited laboratories submit test results. High contaminant levels are flagged, allowing staff to address issues promptly. This data is entered into databases and eventually made publicly available.
- Additional monitoring data is submitted directly to regulatory offices across the state. This includes treatment process data, field measurements such as chlorine residuals, and data from field instruments or online analyzers that are not processed through accredited labs but are essential for evaluating treatment effectiveness.
- The U.S. EPA also collects water quality data through the Safe Drinking Water Accession and Review System (SDWARS 5). This system focuses on unregulated contaminants under evaluation for potential future regulation based on occurrence and other criteria.
Routinely reviewing monitoring data is essential to ensure that the water provided to the public is safe, meets all treatment requirements, and protects public health, as some of the most harmful contaminants in drinking water are not visible
“You can’t see things like nitrate or TCP in the water,” said Ms. Nishimoto. “A good, robust monitoring schema is important to identify these invisible contaminants, so that acute and chronic concerns can both be identified and addressed. It’s important that the public gets notified of potential risks so they can make informed decisions about their own health.”
Where to find water quality data
- Data Publication – https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/EDTlibrary.html
- Public Drinking Water Watch – https://sdwis.waterboards.ca.gov/PDWW/
- Consumer Confidence Reports – An annual summary of a community’s drinking water provided by the water supplier
Coming soon: The Water Technical Access Portal or Water TAP
DDW is working to reenvision how drinking water data is managed and to develop a new system called the Water Technical Access Portal (Water TAP). It is still in the early stages of development, but it will be a one-stop shop with role-based user controls.
“What that means is it’s being designed first for the regulators so that they can manage water systems, but also it’s the single point of access for water systems to report to us and our partner agencies to get data, for academia and NGOs to get our Water data, and even for the public to be able to access and see what’s going on, all in one spot with the drinking water view,” said Ms. Nishimoto. “This will really help move us towards not only statewide consistency, but also transparency, of being able to show the whole flow of water from the source to the distribution system and being able to show what water quality is truly being provided to the public.”
The Environmental Laboratory Accreditation Program: Ensuring reliable data for public health
Christine Sotelo serves as the program manager for the State Water Board’s Environmental Laboratory Accreditation Program (ELAP), leading a team of 27 chemists, scientists, and microbiologists. This program is responsible for regulating environmental laboratories across California and conducting investigations into potential fraud or improper laboratory practices.
ELAP accredits approximately 500 laboratories, both within and outside of California, that produce data for various state regulatory agencies. The program conducts thorough inspections of laboratories to ensure they produce reliable, defensible data for state agencies’ programs and regulatory decisions. Regular evaluations assess the quality system, staff expertise, facilities, equipment maintenance, test method proficiency, and report accuracy to confirm the lab’s capability to deliver high-quality data.
The 1974 Safe Drinking Water Act granted states the authority, known as “primacy,” to enforce federal drinking water regulations and oversee public water systems. Later amendments required the primacy agencies to operate a Laboratory Accreditation Program to retain enforcement authority over drinking water programs and to ensure that data used to make regulatory decisions come from accredited laboratories. The Act also required that the inspectors, also known as assessors, be certified EPA drinking water certification officers. Laboratory certification officers must pass a rigorous test in Ohio covering disciplines such as inorganic chemistry, organic chemistry, and microbiology. With a low passing rate, the test ensures only highly qualified individuals are certified to work in laboratories.
However, to implement those federal regulations, California had to adopt its own regulations, so the state adopted the Environmental Laboratory Accreditation Act in 1988. In addition to drinking water testing, the Act established a program for all environmental testing throughout California for other regulatory agencies. These include CalEPA, the Water Boards, the Department of Water Resources, the Department of Toxic Substances Control, the Department of Fish and Wildlife, the Department of Pesticide Regulation, and others.
“This unified the oversight of laboratories in California,” said Ms. Sotelo. “Before the Environmental Laboratory Accreditation Act, every agency put requirements on how they wanted their laboratories to operate and what the requirements were, so the Act strengthened and made consistent oversight of lab accreditation in California.”
She noted the accreditation is only for regulatory purposes, such as permits, policies, orders, or plans. “We only accredit laboratories that run analyses that are tied to this regulatory purpose,” she said. “It’s not for research purposes. It doesn’t extend to a laboratory that might be doing some novel exploratory method, or any research labs outside of the regulatory framework.”
For example, work is being done to standardize eDNA testing, and there is a water quality monitoring workgroup for eDNA, but the labs doing that work are not required to be accredited because it’s not in any agency’s regulatory framework.
“This is an important distinction, because we really are there to safeguard the regulatory compliance integrity,” said Ms. Sotelo. “We don’t want to inhibit any innovation and any research work that’s done in those laboratories to help look for that latest contaminant of emerging concern, or onboard the new method that a laboratory has developed. We want all of that to happen, so we don’t want to inhibit that work.”
During emergencies, laboratories must balance routine compliance testing with urgent environmental emergency samples, activating response plans to meet increased demands. All drinking water samples must be accredited by ELAP, allowing flexibility to contract with any of California’s 500 accredited labs. This network provides surge capacity, ensuring reliable, defensible data during crises.
During emergencies, laboratories face the dual challenge of maintaining routine compliance testing while addressing urgent environmental samples, often under rushed, high-pressure conditions. Emergencies, such as fires, can disrupt or even shut down laboratory operations, further complicating their ability to meet these demands. To support labs during such crises, ELAP collaborates with the State Water Boards’ Emergency Management Program to track affected laboratories and ensure continuity of service. Using geolocation mapping, ELAP identifies laboratories within emergency zones, providing rapid situational awareness and enabling a coordinated response. This approach helps pinpoint which laboratories can continue routine water compliance sampling and intake emergency samples, ensuring critical testing is not interrupted. By leveraging California’s network of 500 accredited laboratories, which all maintain quality systems, ELAP ensures regulatory monitoring continues despite disruptions, safeguarding public health and providing reliable, defensible data during crises.
The Environmental Response Laboratory Network (ERLN) is a national network established to provide critical chemical, biological, radiological, nuclear, and analytical support during emergencies. Participation in the ERLN requires a rigorous application process, including accreditation by the laboratory’s home state and the implementation of a robust quality system to ensure reliability and accuracy. Currently, 11 California laboratories are part of the ERLN, contributing to the network’s surge capacity and enhancing the state’s ability to respond effectively to environmental crises.
Ms. Sotelo concluded by commending the trusted network of ELAP-accredited laboratories across California, which ensures the production of reliable and defensible data. She highlighted California’s strong environmental preparedness, emphasizing the state’s ability to support monitoring across multiple matrices and environmental programs, extending well beyond drinking water.
“To me, accreditation is like a safety vest,” she said. “I see it as your way to defensible and reliable data. Especially during high-stakes emergency situations, we have that network in place. I’m really proud of our network of 500 laboratories. They don’t know that they’re there for surge capacity, but it’s really a default.”
