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May 25, 2024 10:03PM
May 25, 2024 22:03PM

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Water Quality Regulations

Understanding State and Federal Water Quality Regulations

State and federal water quality regulations are complicated and often not well understood. To help our customers understand the scientific research behind water quality regulations, we put together an information sheet that details both the safety of IRWD drinking water and explains the different types of health standards and goals.


IRWD Drinking Water is Safe

IRWD is confident that the drinking water we provide to homes, businesses and schools is safe and meets all quality standards set by both the state and federal government. IRWD water quality experts continuously monitor water supply and conduct hundreds of laboratory tests each year from water taken from sample points throughout the IRWD service areas.


Scientific Data Comparisons are often Inaccurate

Because of the many levels of regulations and scientific research, some may incorrectly interpret different water quality related standards and goals. For example, some have tried to compare the data against Public Health Goals (PHG) for contaminants rather than legally regulated Maximum Contaminant Levels (MCL). Using this method, the resultant analysis would present an inaccurate and misleading interpretation of the safety of drinking water.


What are Maximum Contaminant Levels?

The U.S. Environmental Protection Agency (USEPA) and the California State Water Resources Control Board Division of Drinking Water establishes science-based standards that limit the amount of certain contaminants in water provided in public water systems. These limits are called maximum contaminant levels (MCLs). An MCL is the maximum amount of a contaminant that can be present while still ensuring that the water meets state and federal standards. MCLs are designed to ensure that drinking water is safe to consume. MCLs are based on stringent scientific research and are evaluated and set through a very public process. An MCL is different from a Public Health Goal.

In California, MCLs are adopted as regulations. They are health protective drinking water standards to be met by public water systems such as IRWD. MCLs take into account not only chemicals' health risks but also factors such as their detectability and treatability, as well as costs of treatment. California Health & Safety Code §116365(a) requires a contaminant's MCL to be established at a level as close to its Public Health Goal (see below) as is technologically and economically feasible, placing primary emphasis on the protection of public health. Along with the MCL, a regulated chemical also has a detection limit for purposes of reporting.


What are Public Health Goals?

Public Health Goals are established by the California Office of Environmental Health Hazard Assessment (OEHHA). PHGs are concentrations of drinking water contaminants that pose no significant health risk if consumed for a lifetime, based on current risk assessment principles, practices, and methods. OEHHA establishes PHGs pursuant to California Health & Safety Code §116365(c) for contaminants with MCLs, and for those for which MCLs will be adopted. Public water systems such as IRWD use PHGs to provide information about drinking water contaminants in their annual Consumer Confidence Reports.

Once OEHHA establishes or revises a PHG for a contaminant with an existing MCL, the California State Water Resources Control Board determines whether the MCL should be considered for possible revision. For chemicals so designated, an in-depth risk management analysis is conducted to determine whether or not to propose a revision. For more information, see MCL review status.


IRWD Report on Water Quality Relative to Public Health Goals

The California Health and Safety Code, Section 116470 requires public water systems with more than 10,000 service connections to prepare a brief written report that provides information regarding the detection of any contaminants above the PHGs adopted by the OEHHA or the MCLs set by the USEPA. This report is intended to provide information to the public in addition to the Consumer Confidence Report (see below). This report is presented to the IRWD Board of Directors in a publically noticed hearing. You can download a copy of the most current report here.


Annual Consumer Confidence Report

Public water agencies such as IRWD are required to provide annual Consumer Confidence Reports (CCRs) to their customers that detail local water quality information. The reports are prepared in accordance with state and federal regulations and include information about the sources of drinking water supplies, what contaminants if any are in those supplies, and how those contaminants may affect public health. The reports also indicate how a district's water supplies compare with state and federal standards. More information about CCRs can be found on the EPA's website at

Click here to read and download a copy of IRWD’s Consumer Confidence Report.