This summary provides a broad overview of current and future drinking water quality standards which public water systems in Oregon must meet through the year 2010 and beyond. It is organized in two major sections – Section I: Current Standards, and Section II: Future Standards. The summary of current standards is for reference only, and is not a substitute for the actual statutes and regulations that govern public water supply in Oregon. Future standards described here are still under development at the national level, and are subject to change.


Types of Drinking Water Contaminants

The sources of drinking water, both tap water and bottled water, include surface water (rivers, lakes, ponds, reservoirs), and groundwater (wells and springs). As water travels over the surface of the land or through the ground, it dissolves naturally-occur- ring minerals and in some cases natural radioactive materials, and can pick up substances from the presence of animals or from human activities.

Drinking water contaminants are any substances present in drinking water that could adversely affect human health if present in high enough concentrations. All drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants. The presence of contaminants does not necessarily mean that the water presents a health risk.

There are now drinking water quality standards for 95 different contaminants. They can be grouped into the following general categories:

● Microbial Contaminants – such as viruses, bacteria, and parasites which can come from sewage treatment plants, septic systems, agricultural and livestock operations, and wildlife.

● Disinfectants and Disinfection By-Products – chemical disinfectants used in water treatment to kill harmful microbes, and the

chemical by-products formed from the reaction of disinfection treatment chemicals with natural substances in the water.

● Inorganic Chemicals – such as salts or metals, which can be naturally-occurring or can result from urban storm water runoff, industrial or domestic wastewater discharges, oil and gas production, mining, or farming. Includes lead and copper leached into the water from household plumbing and fixtures.

● Organic Chemicals – Pesticides and herbicides which may come from a variety of sources, such as agriculture, urban storm water runoff, and residential uses. Also includes synthetic and volatile chemicals which are used in industrial processes and petroleum production and can come from gas stations, urban storm water runoff, and septic systems.

● Radiologic Contaminants – Naturally occurring or resulting from oil and gas production or mining operations.


Every drinking water supply is vulnerable to microbial or chemical contaminants of one type or another from a variety of sources. Disease-causing

microorganisms from human or animal feces (bacteria, viruses, parasites) can be present in surface water or from groundwater. Microorganisms can also enter the water system through pipe breaks or cross connections. Organic chemicals (industrial solvents, pesticides) are mainly man- made and can enter drinking water supplies from chemical production, storage, use, or disposal in the water source area. Inorganic chemicals can be introduced by human activities (nitrate from fertilizer) but more often result from natural occurrence in rocks, soils, and mineral deposits (radon, arsenic). Drinking water treatment which is essential to remove microbes and chemicals can also add or form contaminants in drinking water, such as disinfectant chemicals themselves, byproducts of disinfectants reacting with other substances in the water, and treatment chemicals used in filtering water. Finally, water storage tanks, pipes, and household plumbing that are in direct contact with water can contribute contaminants from either the material used in the tanks and pipes or from internal coatings used to protect the materials from contact with the water.

Drinking Water Standards and Health Protection

To protect health, national regulations set by the US Environmental Protection Agency limit the amounts of certain contaminants in tap water provided by public water systems. Other regulations set by the federal Food and Drug Administration establish limits for contaminants in bottled water which must provide the same level of protection of public health.

In order to be regulated under the Safe Drinking Water Act, a drinking water contaminant must meet certain criteria. The contaminant must be one which:

● may have an adverse effect on the health of persons,

● is known or likely to occur in public drinking water systems with frequencies and levels of health concern, and

● where regulation presents a meaningful opportunity for health risk reduction for persons served by public water systems, considering feasibility and cost.


Drinking water standards take several forms:

● Maximum Contaminant Level Goal (MCLG) – The level of a contaminant in drinking water below which there is no known or expected risk to health, allowing for a margin of safety. All regulated contaminants must have a MCLG, although the MCLG is not enforceable.

● Maximum Contaminant Level (MCL) – The highest level of a contaminant allowed in drinking water, set as close the MCLG as feasible using the best available treatment technology. Most MCLs are expressed in concentration units called “milligrams per liter” (mg/L), which for drinking water is the same as parts per million (ppm). MCLs can be expressed


in a variety of other measurement units.

● Treatment Technique (TT) – A required treatment process intended to reduce the level of a contaminant in drinking water. For any contaminant that can not be effectively measured or detected in drinking water, the standard may be a treatment technique requirement instead of an MCL. This means that all water systems at risk of the contaminant must provide continuous water treatment to remove the contaminant at all times. Performance Standards (PS) are used to determine whether or not a water system is meeting a specific treatment technique requirement. Performance Standards are measurements of water quality parameters related to specific treatment processes, such as turbidity, disinfectant residual, pH, or alkalinity.

● Action Level (AL) – The concentration of a contaminant, which when exceeded, triggers treatment or other requirements which a water supplier must follow. Public water suppliers and bottled water producers must sample for contaminants routinely to ensure that standards are met, and report the results of that sampling to the regulatory agency. Sampling frequencies for public water systems vary by the type of drinking water contaminant. Contaminants that are associated with immediate health impacts, like bacteria and nitrates, must be sampled as often as every month, quarter, or year. Contaminants that are associated with health effects that could develop from very long-term exposures, like arsenic, are sampled less frequently, such as every three or four years or more.

Some people may be more vulnerable to drinking water contaminants than the general population. Immune-compromised persons, such as persons with cancer and undergoing chemotherapy, per- sons who have undergone organ transplants, people with HIV/AIDS or other immune system disorders, some elderly, and infants can be particularly at risk from microbial infections.

These people should seek advice from their health care provider. USEPA and the federal Centers for Disease Prevention and Control (CDC) developed guidelines on appropriate measures to lessen the risk of infection by Cryptosporidium and other microbial contaminants. These are available from the USEPA at


Public Drinking Water Regulatory Program

The first national public drinking water standards, called the National Interim Primary Drinking Water Regulations (NIPDWR), were adopted on December 24, 1975, by the US Environmental Protection Agency (USEPA) under the 1974 Safe Drinking Water Act. By 1986, drinking water quality standards were in place for 23 different contaminants. The 1986 Safe Drinking Water Act mandated USEPA to set standards for 83 contaminants within 3 years, and 25 more contaminants every three years thereafter. The 1996 Safe Drinking Water Act significantly redirected this standard-setting schedule to focus on the highest remaining risks to health.

In Oregon, public drinking water systems are subject to the Oregon Drinking Water Quality Act (ORS 448 – Water Systems). The primary purpose of the 1981 Oregon Act is to “assure all Oregonians safe drinking water”. According to the Oregon Act, safe drinking water means water which is “sufficiently free from biological, chemical, radiological, or physical impurities such that individuals will not be exposed to disease or harmful physiological effects”. Under the Oregon Act, the Department of Human Services has broad authority to set water quality standards necessary to protect public health through insuring safe drinking water within a public water system. To accomplish this, the Department is directed under the Act to require regular water sampling by water suppliers. These samples must be analyzed in laboratories approved by the Department, and the results of laboratory tests on those samples must be reported by the water supplier to the Department. The Department must investigate water systems that fail to submit samples, or whose sample results indicate levels of contaminants that are above maximum allowable levels. Water suppliers who fail to sample the water or report the results, or whose water contains contaminants in excess of allowable levels must take corrective action and notify water users.

Since 1986, the Department has exercised primary responsibility for administering the federal Safe Drinking Water Act in Oregon, an arrangement called

Primacy. The Department adopts and enforces standards that are no less stringent than the federal standards, and in return, the USEPA gives the Department the regulatory responsibility for public drinking water systems and partial financial support for the Oregon program operation.

In practice, the Oregon drinking water standards match the national standards established under the Safe Drinking Water Act by the USEPA. This is because setting maximum levels for drinking water contaminants to protect human health involves considerable development of health effects information and other scientific research that is best carried out at the national level. The Department of Human Services concentrates its efforts on implementing the national standards at Oregon public water systems.


Oregon Public Water Systems

Today, there are 2,756 public water systems in Oregon subject to regulation under the federal Safe Drinking Water Act. They serve 25 or more people at least 60 days per year. Of these, 898 are community water systems, which means the systems serve at least 15 connections used by year-round residents. These systems perform the most frequent water sampling for the greatest number of contaminants, because the people served have the most ongoing exposure to the drinking water. Community water systems in Oregon serve a total of about three million people and range in size from 15-home subdivisions and mobile home parks up to and including the City of Portland.


Non-transient non-community water systems serve nonresidential populations consisting of the same people every day, such as a school or workplace with its own independent water supply system. There are 345 of these in Oregon.

Transient non- community water systems serve transient populations. Examples are campgrounds, parks, or restaurants with their own independent water supply systems, and there are 1,513 of these in Oregon. There are many small water systems in Oregon. About 87% of the public water systems in Oregon serve 500 or fewer people each.

Oregon public water systems get their water either from wells or springs (called groundwater) or from rivers, lakes, or streams (called surface water). Of the 2,756 public water systems in Oregon, 2,459 get their water exclusively from groundwater. 297 water systems get their water in whole or in part from surface water supplies.

Generally speaking, surface water requires much more treatment and processing to ensure safety for drinking than does groundwater. An additional 939 very small systems, serving 10-24 people each, are subject only to the Oregon Act, serving a total of nearly 17,300 people.

About 400,000 Oregonians get their drinking water from individual home wells, which are not subject to either state or federal public drinking water standards.


For More Information

Visit the Oregon Drinking Water Web Page for drinking water information and publications ( Use the “Data Online” feature to look at past and current water sample test results and regulatory compliance status information for any Oregon public water system. In addition, contact names and phone numbers of state and county program staff are listed. You can use “links” at this site to access many other sources of drinking water information.

For example, a comprehensive schedule of federal drinking water standards implementation can be found at



County staffs are responsible for community water systems serving 3,300 people or fewer and using groundwater sources, and all non-transient non-community and transient non-community systems.

Questions about these systems should be directed to the respective county health department.

Department staff are responsible for all community water systems serving more than 3,300 people and all community systems that use surface water sources. In counties without drinking water programs, Department staff are responsible for all public water systems. Department staff also serve as a technical resource for county drinking water programs as needed.

Compliance with drinking water standards is summarized for each calendar year on a statewide basis in the Oregon Annual Compliance Report, which is prepared in June and distributed via the PIPELINE newsletter shortly thereafter. Each community water system must distribute to users an annual Consumer Confidence Report, detailing the levels of contaminants detected in the water system and their significance, listing any violations of standards or sampling requirements that occurred, and providing information on the water sources used by the community.