The Safe Drinking Water Act and decentralized/onsite wastewater.

Protecting drinking water from source to tap is essential to the health of the public and the economic health of communities. The Safe Drinking Water Act (SDWA), originally passed by Congress in 1974, established two major protection programs with missions to prevent contamination of groundwater that is used or could be used as a source of drinking water: the Source Water Assessment and Protection Program (SWAP) and the Underground Injection Control (UIC) Program. This technical brief summarizes these programs and the minimum federal requirements under the SDWA for the discharge of decentralized-system wastewaters.

Source Water Assessment and Protection Program

As of 2003, approximately 161,000 public drinking-water systems have the responsibility of providing the nation with clean and safe water to drink. Almost half the population of the United States relies on groundwater for drinking water, and more than 90 percent of rural residents obtain their water from groundwater. Congress, recognizing the need to protect sources of drinking water, amended the SDWA in 1996 to authorize the establishment of the SWAP Program.

The SDWA amendments outline six steps for prevention programs to protect and benefit public drinking-water systems. Together, these steps form the basis of comprehensive drinking-water source protection. Source water assessment and protection consists of six steps:

1. delineating protection areas for the source waters of public drinking-water supplies;

2. identifying potential sources of contaminants within these areas;

3. determining the susceptibility of the water supplies to contamination from these potential sources;

4. making the results of the assessments available to the public;

5. implementing management measures to prevent, reduce, or eliminate risks to drinking-water supplies; and

6. developing contingency-planning strategies that deal with water supply contamination and service interruption.

The SWAP Program is one of several provisions of the SDWA amendments aimed at protecting source water by encouraging states to form voluntary, mutually beneficial partnerships to develop source water protection strategies for each water supply on the basis of results from their source water assessments. SWAPs may vary from state to state, according to each state's priorities and the degree to which groundwater resources were managed at the program's inception.

Assessments for many water systems, such as those in rural areas, are likely to inventory onsite wastewater treatment systems located in delineated source water areas and possibly to identify some of these as priority pollution threats. Communities are encouraged to consider information from the assessments as a factor in deciding what level of management is necessary to protect their drinking-water sources from such threats. States are making progress on their SWAPs and are at various levels of completion. At the end of 2003, states reported that they had completed the source water assessments for about 70 percent of their public drinking-water systems. The U.S. Environmental Protection Agency (U.S. EPA) anticipates that all source water assessments will be complete by the end of 2006. For more information on the status of specific source water assessments, contact your state source water program liaison. Contact information can be found on the U.S. EPA Web site at www.epa.gov/safewater/source/contacts.html.

Underground Injection Control Program

Facilities across the United States discharge more than 750,000 billion gallons of hazardous and nonhazardous fluids into more than 800,000 injection wells. In 1974, the SDWA authorized the Underground Injection Control (UIC) Program to establish minimum federal requirements for the protection of underground drinking-water sources from the various underground injection practices. The federal regulatory classification for injection wells consists of five classes (classes I-V), ranging from deep (classes I-III) to shallow (classes IV and V). The Class V well category encompasses a wide variety of wells that are typically shallow, percolating systems, such as dry wells, leach fields, and similar types of drainage wells that overlie underground sources of drinking water. To date, 33 states have obtained primary enforcement authority (primacy) for all classes of injection wells. Seven states share primacy with U.S. EPA. For the remaining states, U.S. EPA directly implements the UIC programs. State and tribal UIC programs can have more stringent requirements above and beyond the minimum federal requirements discussed here.

Since 1980, an onsite wastewater treatment system has been considered a Class V well that must fulfill UIC Program regulatory requirements (state and federal) if it meets one of the following conditions:

1. The system receives solely sanitary waste from multiple family residences or a nonresidential establishment and has the capacity to serve 20 or more people per day (a system of this type is also known as a "large-capacity septic system").

2. The system receives any amount of industrial or commercial wastewater (a system of this type is also known as an "industrialwaste disposal well").

The majority of Class V wells, including large-capacity septic systems, are "authorized by rule" provided they meet these minimum federal requirements:

1. The injectate does not endanger underground sources of drinking water, and

2. the owner or operator submits basic inventory information to the state or U.S. EPA regional UIC program.

"Authorized by rule," means that an individual permit is not required, unless requested by the UIC program director in the state. Inventory information includes facility name and location, legal contact name and address, ownership information, nature and type of injection well(s), and operating status.

The non-endangerment standard prohibits injection that allows the movement of fluids containing any contaminant into an underground source of drinking water if the presence of that contaminant may cause a violation of any primary drinking-water regulation or adversely affect public health. The point of compliance at which large-capacity septic systems must meet this non-endangerment performance standard is determined on a case-by-case basis depending on a variety of site-specific factors such as soil and hydrogeology, wastewater characteristics, and system design. U.S. EPA acknowledges that the soil is an integral part of an onsite wastewater treatment system that receives solely sanitary waste. A conventional system (meaning an onsite wastewater treatment system that consists of a septic tank and a drainfield) receiving industrial wastewater without pretreatment might, however, be required to comply with drinking-water or other healthbased standards (e.g., maximum-contaminant levels) at the point of injection or be prohibited entirely because these systems are not designed to treat industrial wastewaters.

The majority of states and regional UIC programs work in partnership with their local health departments to ensure that these minimum federal requirements are met before a large-capacity septic system is permitted. This cooperative relationship ensures that, locally, all large-capacity systems are regulated in a consistent manner regardless of size. In addition, the UIC Program works internally with other offices in U.S. EPA and with external stakeholders like NEHA to improve the management and performance of large-capacity septic systems.

As the nation continues to grow over the next 20 years, millions of new homes and business will be built outside of existing urban and suburban areas, creating a need for more onsite wastewater treatment systems. Communities need to make decisions about how best to manage development to ensure safe and sustainable water supplies and cost-effective wastewater treatment systems. When properly managed, onsite systems can be the wastewater treatment option of choice for local communities. They need, however, to be considered in the context of a fully integrated water supply and treatment framework that meets regulatory requirements and evaluates water quality needs and potential water quality impacts.

For more information on the Safe Drinking Water Act and its programs, visit U.S. EPA's Web site at www.epa.gov/safewater.

(This technical brief was prepared by Suzanne Kelly, Prevention Branch, U.S. Environmental Protection Agency [4606M], Washington, DC 20460, and presents views that are not necessarily the policies of the U.S. Environmental Protection Agency.)