States are completing assessments of sources of drinking water for all public drinking water systems as required by the Safe Drinking Water Act. Each state is to define contaminants of concern to drinking water supplies (ground and surface water) and inventory significant potential sources of those contaminants. Each state or local community may have different sources of concern based on local factors, such as existing agricultural or industrial activity and known contaminant occurrence information.

States must include all contaminants regulated under the Safe Drinking Water Act. They may also include other contaminants that pose a threat to the public, such as other microbiological contaminants (e.g., pathogenic viruses and bacteria).

Potential contamination sources for ground and surface waters include:

• Superfund sites
• sites reporting under EPA's Toxic Release Inventory
• sites with a National Pollutant Discharge Elimination System (NPDES) permit
• underground storage tanks (USTs)
• sites regulated under the Resource Conservation and Recovery Act (RCRA)
• sites regulated by other state or federal programs
• anticipated future sources

In addition to these specific potential discrete point sources of pollution, each state is to categorize and rank the potential for contamination from nonpoint sources based on categories of land use. For example, Delaware has ranked the threat from each of nine different categories of contaminants (e.g., nutrients, pesticides, metals) from each of 19 different categories of land uses (e.g., residential, railroads, farmlands) as being either possible, not probable, or not applicable. New York has a somewhat different list of 14 categories of contaminants and 15 categories of land use. The state ranks the potential for contamination on a scale of negligible, low, medium, or high. Delaware ranks the potential for pesticide contamination of groundwater in residential areas as probable and New York ranks it as medium.

States are to also identify how susceptible water systems are to these sources based on such factors as the amounts of contaminants produced, stored, or used, and the likelihood of release, and protective measures in place. Many of the potentially more serious sources of contamination are regulated under various federal, state, or local statutes.

Completing the source inventories can be expensive, so EPA recommends that states work with community volunteers to do some of the inventory work. Volunteer groups might include elderly participants in RSVP programs or younger people such as the Boy Scouts, Girl Scouts, and 4H Club members. Contact your state water agency to find out about opportunities to participate.

More information is available on EPA's Web site (http://www.epa.gov/OGWDW/swp/intro4.html) or through EPA's Safe Drinking Water Hotline (800-426-4791).