Steven P. Roy, Associate Director

Tetra Tech, Inc., 10306 Eaton Place, Suite 340, Fairfax, VA 22030

E-mail: royst@tetratech-ffx.com

Source Water Assessments will require states and water utilities to compile and review large volumes of information related to water system operation, hydrogeology, hydrology, potential contamination sources, and water quality. Many state and federal environmental databases exist in electronic formats that can provide valuable information for states and water utilities conducting source water assessments. Easy linkage to databases supported by the U.S. Environmental Protection Agency and the U.S. Geological Survey can supply vast amounts of data related to water quality, point source discharges, solid and hazardous waste facilities, soils, geology, topography, land use, in stream water quality violations, etc. EPA’s Index of Watershed Indicators and Surf Your Watershed can provide information on potential source water pollution on a geographic basis. This paper will describe some of the data requirements necessary to conduct a source water assessment and how accessing existing federal databases can form the basis of a source water assessment.

Public water supply development, delivery, and management is a locally driven effort in the United States. Because of the diverse nature of drinking water management, source water assessments will be most effective when initiated locally. Most public water supplies that have experienced water quality contamination have identified either nonpoint sources of contamination or unregulated activities such as spills, leaks, or illegal disposal as the source of contamination. However, a contamination assessment would not be complete without first identifying those potentially polluting activities that are permitted.

The following sections describe the nature of public water supply in the United States, review the source water assessment requirements, identify federal contaminant data sources and systems, and presents possible systems that could be used by states to assist in conducting source water assessments.

There are over 180 thousand water systems in the United States that serve over 250 million people (USEPA, 1997a). This estimate includes community water systems, transient noncommunity water systems, and nontransient noncommunity water systems (Table 1). This number is important for source water assessment purposes because each of these systems must have an assessment completed within a window of 3-1/2 years. Another way to look at this volume of work is 51,532 assessments per year, or 277 assessments per day, or 5.3 assessments/state/day. This workload points to the need for some level of automation.

Fifty-three percent (53%) of the U.S. population obtains its drinking water from groundwater sources (USEPA, 1997b). Groundwater is the predominant source of supply for community water systems. Close to 80% of the community water systems rely upon groundwater as their primary source (Table 2), and most of these systems (85%) are small, serving less than 3,300 persons each.

Water utilities, local governments, state governments, and the federal government share the responsibility for developing measures and programs to protect drinking water quality. Drinking water suppliers have been guided in their efforts due primarily to source protection provisions of The Safe Drinking Water Act (SDWA). The SDWA requires the USEPA to set standards for maximum contaminant levels (the maximum permissible level of contaminant in water delivered to any user of a public water supply system) in public drinking water supplies, regulate underground injection of wastes into groundwaters, and establishes public water supply protection programs. In 1986, Amendments to the SDWA were passed increasing the authority and responsibility for drinking water protection. The Amendments created the Sole Source Aquifer Demonstration Program and the Wellhead Protection Program. Subsequent amendments in 1996 further strengthened drinking water protection with the establishment of the Source Water Protection Program.

The 1996 Amendments to the Safe Drinking Water Act (SDWA) created the requirement that all 180 thousand public water supplies be covered under a source water protection program (SWAP). The basic assumption for the implementation of source water protection programs is that multiple-barrier protection of public water supplies will provide for high quality water supplies and protect public health. The establishment of multiple barriers that include source water protection, treatment, distribution system maintenance, and monitoring, are proposed to protect the quality and safety of drinking water supplies. Source water assessment and protection represents the first step in protecting public water supplies.

Source water assessments are the centerpiece of the new SDWA’s focus on prevention. Source water assessments identify the potential threats to the source of a community’s drinking water. States can use the assessments to issue monitoring waivers for many chemicals regulated under the Act. Over the next four years, the States are directed to develop source water assessments for all public water supplies which will include the following:

Section 1453 (2)(A) of SDWA requires that the states delineate the boundaries of the source water protection areas (SWPA) from which one or more public water systems receives its drinking water supply. U.S EPA’s Source Water Protection Final Guidance Document specifies the following delineation approaches:

For surface water systems, the SWPA should include the entire watershed area upstream of the Public Water System’s (PWS) intake, up to the state border. The states can choose to segment large watersheds into sub-basins or buffer zones to provide for more cost-effective contaminant source inventories and susceptibility analyses (EPA, 1997c, d, e).

For ground water systems, delineations should be conducted using one or more of the following methods: (1) arbitrary radii; (2) calculated fixed radii; (3) simplified variable shapes; (4) analytical methods; (5) hydrogeologic mapping; and (6) numerical flow/transport models (EPA, 1987, EPA, 1997a).

States are required to identify the sources of contaminants regulated under SDWA for which monitoring is required (or any unregulated contaminants selected by the State that may present a threat to public health). These contaminants include those regulated under the SDWA (contaminants with a maximum contaminant level (MCL), contaminants regulated under the SWTR, and the microorganism Cryptosporidium.) A variety of both regulated and unregulated contaminant sources are found within source water protection areas, including aboveground and underground storage tanks; animal feedlots; agricultural chemicals, underground injection wells; chemical processing facilities; transportation and road maintenance facilities; septic systems; pipelines; and waste transport, storage, and disposal facilities.

Contaminant source inventories of permitted facilities can be conducted using existing data sources (e.g., U.S. EPA’s Envirofacts data base), land record searches, and local surveys or canvassing efforts.

Susceptibility assessments are the least understood aspect of source water protection, yet the most important. Assessments are intended to identify the contaminant sources that pose the greatest threat to the drinking water supply so that they can be targeted for management. Assessment methodologies include simple, analytical techniques such as hydrogeologic and hydrologic mapping to identify the relative vulnerability of ground water and surface water supplies, as well as complex contaminant transport models linked to risk assessment matrices. Once a source water’s susceptibility is assessed, a vulnerability determination must be produced and made available to the public.

Implementation of management controls is not required under the SDWA amendments of 1996, however many water suppliers and local governments are actively controlling existing contamination sources and preventing new contamination sources from threatening drinking water quality, through the implementation of various management controls.

Under Section 1453 (2) (B) of the Safe Drinking Water Act, states are required to identify the sources of contaminants regulated under the Act for which monitoring is required (or any unregulated contaminants selected by the State that may present a threat to public health). To the extent practical, the state must identify the source of the contaminants within the SWPA to determine the susceptibility of the public water systems to contamination.

A variety of both regulated and unregulated contaminant sources are found within SWPAs. These include aboveground and underground storage tanks; animal feedlots; underground injection wells (especially Class V wells); agricultural chemical storage and processing facilities; transportation and road maintenance facilities; septic systems; pipelines; and waste transport, storage, and disposal facilities. The range of potential contaminants and contaminant sources are described in several EPA publications (EPA, 1990; EPA, 1991a; EPA, 1991b).

Because of the wide variety of potential contaminant sources that may be found in SWPAs, a hierarchical approach to source identification is appropriate and most cost effective. The information sources available to support this approach are summarized below.

The U.S. EPA Envirofacts Warehouse allows for on-line retrieval of environmental information from Seven EPA databases on Superfund sites (Comprehensive Environmental Response, Compensation, & Liability Information System, CERCLIS), drinking water (Safe Drinking Water Information System, SDWIS), toxic and air releases (Toxic Release Inventory, TRI), hazardous waste (RCRIS), and water discharge permits (Permit Compliance System, PCS), and grants information. As a result, an Envirofacts search allows for rapid identification of existing and abandoned waste management facilities within the SWPA and other ongoing hazardous substance releases to the air, land, or water. In addition, certain states may maintain additional searchable data on underground injection wells and underground storage tanks. The U.S. EPA is currently working on improving and enhancing many of its environmental databases. During 1998 and 1999, many significant changes in these systems will result in easier assess for the public and better locational information.

Information can be collected from local government records, including operating, discharge, and disposal, construction, and other permitting information; zoning records; real estate titles and transactions; and health department records. Maps, aerial photographs, telephone directories, and historic records can be used to locate particular land uses that have been or are continuing to threaten the SWPA.

Because many sources, such as product storage facilities, failing septic systems, or abandoned underground storage tanks, may not be tracked at the local level, additional information collection is often needed to adequately characterize threats to the PWS. Such information can be collected by door-to-door canvasing within the SWPA, windshield surveys, mail surveys, or general public education and outreach to request and gather new information. A number of communities have successfully used local volunteers to collect such information.

EPA (1991b) provides worksheets to help target more significant contaminant sources based on the type and volume of materials managed at the sources and the proximity and vulnerability of the drinking water intake. For those sources that are deemed most significant, the accuracy and reliability of the gathered information should be verified. Ground-truthing or field-checking the data will help support the SWPA susceptibility analysis.

Vulnerability and susceptibility assessments are perhaps the least understood concept related to source water protection. Many states and water utilities have developed approaches to assess the vulnerability of drinking water sources to contamination. Methodologies have ranged from risk matrices to complex contaminant transport models.

Many states have prepared methods to assess ground water vulnerability. Many of these methods address a specific contaminant or hydrogeologic setting. The EPA is currently considering a decision-tree approach to predict microbial contamination in ground water systems. Surface water assessments have relied on predictive models such as Qual2E, and SWMM. Packaged assessment products such as Better Assessment Science Integrating Point and Nonpoint Sources (BASINs) developed by EPA, Office of Science and Technology present a new method to incorporate both point source and nonpoint source pollution into source water assessments.

BASINS supports the development of total maximum daily loads (TMDLs), which require a watershed-based approach that integrates both point and nonpoint sources. BASINS can support this type of approach for the analysis of a variety of pollutants. It can also support analysis at a variety of scales, using tools that range from simple to sophisticated. BASINS was originally released in September, 1996 (BASINS 1.0), version 2.0 is scheduled for release in the summer of 1999. The foundation of BASINS is the interrelated components essential for performing watershed and water quality analysis. These components are grouped into four categories:

1. Databases with local data import tools;
2. Assessment tools (TARGET, ASSESS, and Data Mining) that address needs ranging from large-scale to small-scale;
3. Watershed and water quality models including NPSM (HSPF), TOXIROUTE, and QUAL2E; and
4. Post-processing output tools.

BASINS was used to query the type and number of facilities within the drainage area of Lake Harsha in Clermont County, OH. The results include: 5 wastewater discharge facilities; 3 toxic release inventory sites; 28 water quality monitoring stations; and 11 bacteria monitoring stations. This query resulted in the ability to access a large amount of actual water quality monitoring data, as well as identify the location and type of potential point sources of pollution. A good first step in conducting a source water assessment for Lake Harsha.

States, local governments and water suppliers face a significant challenge to implement the source water assessment requirements of the SDWA. Tools are available to assist in the first step of identifying water quality information and point source discharge information. Envirofacts and BASINS provide information and map tools to initially assess threats and vulnerability of public water supplies to contamination. These tools should only be used as an initial evaluation approach, supplemented with more detailed state and local information. Nonpoint sources of pollution including septic systems and agricultural impacts can not be derived from these systems. Locally-derived information is critical to conduct accurate source water assessments. Completed source water assessments will provide the opportunity for the synthesis, analysis, and central display of public water supply water quality and potential water quality threats. A mechanism must be developed to ensure that source water assessments are integrated with other monitoring and assessment efforts.

U.S. Environmental Protection Agency. 1985. Protection of Public Water Supplies from Ground-Water Contamination, Seminar Publication. EPA 625-4-85-016. Center for Environmental Research Information.

U.S. Environmental Protection Agency. 1987. Guidelines for Delineation of Wellhead Protection Areas. EPA 44016-87-010. Office of Ground-Water Protection.

U.S. Environmental Protection Agency. 1988. Developing a State Wellhead Protection Program: A User’s Guide to Assist State Agencies Under the Safe Drinking Water Act. EPA 440/6-88-003. Office of Ground-Water Protection

U.S. Environmental Protection Agency. 1989. Wellhead Protection Programs: Tools for Local Governments. EPA 440-6-89-002. Office of Water.

U.S. Environmental Protection Agency. 1990. A Review of Sources of Ground Water Contamination from Light Industry. EPA 440/6-90-005.

U.S. Environmental Protection Agency. 1991a. Guide for Conducting Contaminant Source Inventories for Public Drinking Water Supplies. EPA 570/9-91-014.

U.S. Environmental Protection Agency. 1991b. Managing Ground Water Contamination Sources in Wellhead Protection Areas: A Priority Setting Approach. EPA 570/9-91-023. Office of Ground Water and Drinking Water.

U.S. Environmental Protection Agency. 1993. Wellhead Protection: A Guide for Small Communities, Seminar Publication. EPA 625/R-93/002. Office of Research and Development and Office of Water.

U.S. Environmental Protection Agency. 1997a. The 1995 Community Water Supply Survey. Office of Water.

U.S. Environmental Protection Agency. 1997b. Water on Tap: A Consumer’s Guide to the Nation’s Drinking Water. EPA 815-K-97-002. Office of Water.

U.S. Environmental Protection Agency. 1997c. State Source Water Assessment and Protection Programs—Final Guidance. EPA 816-R-97-009. Office of Water.

U.S. Environmental Protection Agency. 1997d. Guidelines for Wellhead and Springhead Protection Area Delineation in Carbonate Rocks. EPA 904-B-97-003. Region 4, Groundwater Protection Branch.

U.S. Environmental Protection Agency. 1997e. Delineation of Source Water Protection Areas, A Discussion for Managers; Part 1: A Conjunctive Approach for Ground Water and Surface Water. EPA 816-R-97-012. Office of Water.

Internet Web Sites to Support Source Water

http://www.epa.gov/OST/BASINS