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Frequently
Asked Questions
What is a Source Water Assessment?
A source water assessment is a study and report, unique
to each water system, that provides basic information about the
water used to provide drinking water.
What Will My Assessment Tell Me?
- Where My Drinking Water Comes From. Source Water Assessments
identify the area of land that most directly contributes the raw
water used for drinking water.
- What Could Pose a Threat to My Drinking Water Quality.
Assessments identify the major potential sources of contamination
to drinking water supplies. This information is used to determine
how susceptible the water system is to contamination.
Is This Information Available?
The results of an assessment will be provided to the public to help
communities plan for protection activities. Information about the
assessment will be included in the yearly consumer
confidence report you receive from your water utility.
Does My Water System Have a Source Water Assessment?
Every state is moving forward to implement assessments of its public
water systems, as required under a new federal Safe Drinking Water
Act program called the Source Water Assessment
Program (SWAP). Assessments must be completed by 2003 for every
public water system--for major metropolitan areas and the smallest
towns, including schools, restaurants, and other public facilities
that have wells or surface water supplies. Assessments will not
be conducted for drinking water systems that have less than fifteen
service connections or that regularly serve less than twenty-five
individuals, since these are not considered public water systems.
Who is Paying for These Assessments?
Source water assessments and protection measures are eligible uses
of the Drinking Water State Revolving Fund (DWSRF) set-asides. States
may use the funds for a mixture of source
water related local assistance activities. For example,
funds are available for Land Acquisition
and Conservation Easements.
Source
Water Assessments
The source water assessment programs created by states differ since
they are tailored to each state’s water resources and drinking
water priorities. However, each assessment must include four major
elements:
- delineating (or mapping) the source water assessment area,
- conducting an inventory of potential sources of contamination
in the delineated area,
- determining the susceptibility of the water supply to those
contamination sources, and
- releasing the results of the determinations to the public.
These steps are described in more detail below, with information
on how citizens and organizations can join in the assessment process.
More information about the SWAP program
is available. Our SWAP Contact
List has state specific contacts and links to State web sites.
Source Water
Assessment Using Geographic Information Systems: This document
provides guidance to states, municipalities, and public water utilities
for assessing source waters using geographic information system
(GIS) technology.
STEP
1: Delineate the Source Water Assessment Area
For each ground water well or surface water intake that supplies
public drinking water, the land area that could contribute water
and pollutants to the water supply must be delineated, or mapped.
Significant potential sources of contamination will then be identified
in this delineated area during Step 2 of the assessment process.
For ground water supplies, states commonly use information about
the flow of underground water to delineate source water assessment
boundaries. This results in a map of land areas where, if pollutants
are spilled or discharged on the surface, they could filter through
the soil to the ground water and be drawn into a particular well.
Some states may use a simpler mapping approach, by drawing a circle
of a certain radius around the well.
For a community that uses surface water from a stream, river,
lake, or reservoir, the land area in the watershed upstream of
the intake is identified on the map. A watershed boundary is drawn
using a topographic map, and includes the land areas where rain
or melted snow flows over or through the ground and eventually
enters the water source upstream of the water system’s intake.
Some states plan to divide the watershed area into segments--areas
closest to the intake where most types of contamination sources
can impact the water supply, and other more distant areas. The
entire watershed up to the state’s boundaries is required
to be delineated, but the inventory of potential pollution sources
may be more detailed in segments that are closer to the intake.
After the state has completed its assessment for a water system,
the community may decide to undertake protection efforts for targeted
sources of contamination. An initial step could be to expand upon
the state’s delineation process. Particularly for smaller
ground water systems, where states may not have the resources
to conduct a detailed delineation, additional scientific methods
can be used to more accurately delineate the area that contributes
ground water to the well.
Community members can seek assistance from the environmental
sciences, geology, or engineering departments of local colleges,
or from environmental consulting firms to assist in creating more
detailed delineations. Sometimes these services are provided by
professors, graduate students, or local firms for a reduced fee
or none at all. In addition, local water resource information
is often available from other sources such as the federal Natural
Resource Conservation Service, the United States Geological Survey,
and the state’s Cooperative Extension Service.
For more information on delineation see Reliable
Sources - Delineation.
STEP
2: Conduct an Inventory of Potential Sources of Contamination
Community groups can become especially involved in the second
step of an assessment--identifying potential sources of pollutants
that could contaminate the water supply. This inventory usually
results in a list and a map of facilities and activities within
the delineated area that may release contaminants into the ground
water supply (for wells) or the watershed of the river or lake
(for surface water sources).
Some examples of the many different types of potential pollutant
sources include landfills, underground or above-ground fuel storage
tanks, residential or commercial septic systems, storm water runoff
from streets and lawns, farms that apply pesticides and fertilizers,
and sludge disposal sites.
Some states are asking communities to conduct the inventory themselves,
in order to obtain detailed information about potential contaminant
sources. Others will use computer databases and focus the inventory
on land uses and activities that are currently mapped or regulated.
Although this approach may not address sources of contaminants
that are not currently regulated, such as smaller livestock areas
or auto salvage yards, the database inventories could include
industries and sewage treatment plants that discharge wastewater,
hazardous waste sites, mining operations, particular land use
categories (such as industrial, agricultural and urban areas),
and various facilities that have environmental permits.
Community groups such as watershed organizations, local environmental
committees or scout troops can enhance the state’s assessment
by conducting site-specific inventories of potential pollutant
sources that may not be on state databases or maps. Local inventories
may provide information on abandoned dump sites, businesses with
septic tanks or floor drains such as dry cleaners or car repair
shops, pesticide mixing and storage areas, golf courses, and other
land uses that may release pollutants to ground water or surface
water. Community groups can coordinate their local inventory with
the state’s assessment process or can enhance a completed
assessment with a more detailed inventory.
A helpful document to aid community groups is EPA’s "Drinking
Water Contaminant Source Index" which is a list of potential
contaminant sources and the pollutants they can release. Additional
resources about contamination are available at Reliable
Sources - Contaminant Source Inventory.
STEP
3: Determine the Susceptibility of the Water Supply to Contamination
For the susceptibility analysis, the state combines the inventory
results with other relevant information to decide how likely a
water supply is to become contaminated by identified potential
sources of contamination. This critical step makes the assessments
useful for communities, since it provides information that local
decision-makers may use to prioritize approaches for protecting
the drinking water supply. Local information provided to the state
by local community groups about contaminant sources, water resource
characteristics, or environmental management practices may be
used in the susceptibility determination process. Some states
prioritize the potential for contamination from identified potential
contamination sources or specific chemicals that could pollute
the water. Other states assign susceptibility rankings of high,
medium or low to the water sources.
 
For more information on susceptibility see Reliable
Sources - Susceptibility Determination.
STEP
4: Release the Assessment Results to the Public
After a state completes the assessment of a particular water
system, it will summarize the information for the public. Such
summaries help communities understand the potential threats to
their water supplies and identify priority needs for protecting
the water from contamination. States will make the assessment
summaries available to the public in a variety of ways. Some states
plan to convene public workshops, while others will have copies
available in public libraries and from local government offices
or water suppliers. Many also plan to post the assessment summaries
on the Internet. The results of the assessments will also be included
in the annual water quality reports that community water systems
are required to prepare for their customers. Community groups
can convene local meetings to discuss the results and begin the
process of protecting the drinking water source.
For more information on results see Reliable
Sources - Public Availability.
Using
the Assessment
Whether using the state’s assessment or expanding it into
a more detailed local assessment, communities can use information
gathered through the assessment process to create a broader source
water protection program. Community groups and local officials,
working in cooperation with local, regional, and state government
agencies can plan how to manage identified potential contamination
sources and prevent new contaminant threats in the source water
assessment area.
Communities use a wide array of different source water protection
methods to prevent contamination of their drinking water supplies.
One management option involves regulations, such as prohibiting
or restricting land uses that may release contaminants in critical
source water areas. Along with regulations, many communities hold
local events and distribute information to educate and encourage
citizens and businesses to recycle used oil, limit their use of
pesticides, participate in watershed cleanup activities, and a multitude
of other prevention activities. Another aspect of a source water
protection program can be the purchase of land or creation of conservation
easements to serve as a protection zone near the drinking water
source. For an effective protection program, communities should
consider using a variety of prevention measures.
EPA's fact sheet, Community Involvement
in Source Water Assessments, explains the four steps of source
water assessments; how communities can participate in the assessment
process; and how communities can utilize assessment information
for source water protection. A downloadable version (PDF, 180kb)
is available.
Your local water supplier may also have more information about
opportunities to become involved in the source water assessment
process. EPA can provide some local information
about your drinking water system. You can also call the number
on your water bill or contact your local health department for information
on your water supplier.
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