Inventorying Potential Sources of Drinking Water Contamination
Barbara C. Cooper, Water Quality Education Specialist
Jane R. Frankenberger, Extension Agricultural Engineer
Fred Whitford, Coordinator, Purdue Pesticide Programs
Clean, safe drinking water is vital to our communities, to our economy,
and to our health. If your ground water becomes contaminated, it may be
lost forever as a water supply or may require very expensive treatment to
remain usable. The best way you can ensure safe water, now and for the
future, is to protect the area around your drinking water supply wells
from potential hazards.
|What Is a Potential Contaminant
|How Do You Conduct a
Contaminant Source Inventory?
|Sources for Maps and Aerial
|Indiana Information Contacts
This publication provides guidance for the public water supply operators
and local wellhead protection planning team members who will guide the
completion of the contaminant source inventory. It explains the process of
identifying regulated and unregulated, present and past, potential
contaminant sources within the wellhead protection area. It assumes that
your wellhead protection planning team has defined and mapped your
wellhead protection area using an appropriate delineation method. (See
"Useful Publications" for Purdue Extension publications offering
information on these topics.)
|Wellhead Protection Planning Overview
|Local planning team
|Delineation of the wellhead protection area
|Identification of potential sources of
|Management of the wellhead protection area
|Public participation, education, and outreach
Why Do a Contaminant Source Inventory?
Indiana's Wellhead Protection Rule (327 IAC 8-4.1) requires community
water supply systems to "complete an inventory of potential sources of
contamination (regulated and non-regulated) within the wellhead protection
area." This rule requires a search of existing databases of regulated
sources, but a database search alone will not reveal all potential sources
of contamination. Volunteers your team recruits must also travel through
the wellhead protection area to do a site inventory. And you should
supplement this information by seeking historical land use data from
long-time community residents.
By knowing what potential contamination sources exist near your drinking
water supply wells, your community can help prevent ground water
contamination through effective management of land activities. Experiences
of other communities have shown that on average, wellhead protection is 27
times less costly than cleaning up a contaminated water source, according
to the Environmental Protection Agency. Not only is wellhead protection a
matter of common sense, it is a good idea from an economic point of view.
What Is a Potential Contaminant Source?
A potential contaminant is anything that might get into your drink-ing
water that you would not want to drink. A source is a facility or land
activity that could release a contaminant. While soil serves as a filter
for many things that might otherwise enter the ground water, it is not
capable of remov-ing everything. So it is important to prevent
contaminants at or near the surface of the ground from seeping into the
The most important potential sources of contamination to identify are
those that are particularly hazardous to health and those occurring in
large volumes. Some obvious potential sources of ground water
contamination are hazardous chemicals that are stored, transferred, or
used in the wellhead protection area.
However, many other things are potentially hazardous to ground water.
Other potential sources include abandoned wells, land-fills, animal feed
lots, storage lagoons, abandoned underground storage tanks, quarries or
mines, and septic systems. Former or abandoned gasoline stations, dry
cleaners, and manufacturing facilities, even though no longer in
operation, might also be potential sources of contamination. The
contaminant source inventory is a list of all potential sources of
contamination within the wellhead protec-tion area.
How Do You Conduct a Contaminant Source Inventory?
To complete an inventory of potential contaminant sources, your
team will need to identify existing regulated and non-regulated
sources, locate and identify them on a map, and tabulate the col-lected
information about the sources. So one of your first tasks is to
get base maps your team can use for organizing this data.
1. Get Maps of the Wellhead Protection Area
Maps are vital throughout the wellhead protection planning process. All
the informa-tion gathered must be both tabulated and displayed on a map in
the wellhead protec-tion plan submitted to the Indiana Depart-ment of
Environmental Management (IDEM). If your area lies at the edge or corner
of an existing map sheet, you may need to obtain more than one published
map to cover your wellhead protection area.
A Note on Map Scale
A map is a representation of features on the land's surface,
a size that can be viewed on a piece of paper. Every
map has a
specified scale that tells the user how much size
reduction has taken
place in the production of the map. An 8"x11"
map of the world would be
a smaller scale (and show less detail)
than an 8"x11" map of your town.
For a wellhead protection plan,
IDEM requires the use of maps in which
one inch on the map
represents between 400 feet and 1000 feet on the
scales within this range will show enough detail to
How do you know if a map or photo is at an acceptable scale for
the contaminant source inventory? Most maps are labeled
with a scale
that is a ratio between one unit of distance on the
map and a
corresponding unit of distance on the ground. It is
written as two
numbers with a colon between. A scale of 1:200
means that one inch on
the map is 200 inches on the ground, or
one centimeter on the map is
200 centimeters on the ground. The
units, whether inches, centimeters,
or something else, do not
matter-the ratio is the significant
information. To comply with
the requirement in Indiana's Wellhead
Protection Rule, the scale
of your map must be between 1:4,800
(equivalent to one inch =
400 feet) and 1:12,000 (one inch = 1000
You will need at least three copies of your base map(s). One copy you will
send to IDEM with your completed plan, one you will keep as a master copy
for yourself, and one you will use as a working map to write and erase on
as changes are made. You will also need to photocopy (and possibly
en-large) the working copy of the base map and divide it into sections for
use by volunteers who will help with the site survey of the wellhead
protection area. The site survey process is described in more detail in a
later section of this publication.
Here are some options for types of maps your team can use as your base
map. IDEM requires that you use either a USGS 7.5 minute topographic
quadrangle or a map at a specific scale. (See the sidebar "A Note on
Scale.") You can find information on where to acquire these maps at the
end of this publication.
* Engineering Map-If you had the wellhead protection area
delineated professionally, you should have received from the consultant a
map of the delineated wellhead protection area at a scale of between
1:4,800 and 1:12,000. (See "A Note on Map Scale.") Depending on the detail
included, your team could reproduce and use this delinea-tion map as the
base map for the contaminant source inventory.
* Topographic Quadrangle Map-If you have a system small enough
(pumping less than 100,000 gallons per day) you are eligible to apply to
IDEM to use the 3000-foot radius as the wellhead protection area. You are
required to submit a topographic quadrangle map showing the delineated
wellhead protection area to IDEM (Figure 1). You can enlarge this map to
double its normal size and use it as your base map.
* Plat Map-Your team can also use a plat map as a base map, if it
is of the appropriate scale. The advantage of using a plat map is that it
already shows property boundaries and land ownership.
* City or County Map-If your wellhead protection area can be
indicated on a city or county map and it is the proper scale
of between 1:4,800 and 1:12,000, your team could use the
city or county map as a base map.
* Aerial Photos-Aerial photography provides an option for the site
survey portion of the contaminant source inven-tory. Because it is often
difficult to get a clear photocopy, it is probably not the best choice for
the base map. However, an advantage of aerial photos is that evidence of
former hazardous land activities and present land activities can be
identified, and that information can be transferred to your base map.
No matter what type base map your team chooses, the delineated wellhead
protection area should be clearly marked on the map (Figure 2). It is
important that the map you choose as a base map is easy to read even when
Once you get a suitable base map, draw the delineated wellhead protection
area on it. The delineated wellhead protection area is the area for which
you will gather infor-mation on potential contaminant sources.
2. Gather Data.
Your team must use two techniques to gather the information needed to
identify potential contaminant sources. These include:
* Reviewing records of regulated potential contamination sources
in federal databases and in state and county databases and files, and
* Traveling through the wellhead protection area observing land
activities that may not be included in any databases.
As you complete each of these data-collection processes, compile the data
collected onto one copy of your map. This publication refers to the map on
which you add or compile information as the "working map." Create a table
to list the information related to each map entry. (See "Organize Data.")
In large communities, there will a correspondingly large volume of data to
be organized. So it is good to organize as you progress rather than
waiting until all the information is collected.
The Records Review
Your database search should locate existing and former potential
contaminant sources that are regulated by some government entity. Many
potential sources of contamination, such as landfills, underground storage
tanks, and pesticide storage sites, are regulated, and the records about
such sites are public information. A search of existing databases will
provide identification of regulated sources.
You can obtain these records using one of two methods: by hiring a private
consultant to complete a database search for your specific area or by
searching the databases yourself using a computer with an Internet
You can hire a consultant to perform the search of federal and some state
databases for hazardous materials, past reported spills, and underground storage
tanks. The price depends on the complexity of the delineated wellhead protection
area and will range between a few hundred and a few thousand dollars. Some of
these providers will plot the data on a map and provide the data in a table,
as necessary for compliance with Indiana's Wellhead Protection Rule. Some consultants
who can provide these services are listed on the Web at http://www.ecn.purdue.edu/SafeWater/.
Whether you hire a consultant or search the databases yourself, be
aware that the databases may not be totally accurate. Through personal
experience, someone on your wellhead protection planning team may
be aware of changes that have occurred which make the information
on the databases inaccurate. So check the database information for
accuracy and consistency.
Federal Database Search
If you or someone on the wellhead protection planning team chooses to search
the databases, visit http://www.epa.gov/enviro/ to find information
about federally regulated facilities.
- Superfund-The federal government locates, investigates, and cleans up
the worst hazardous waste sites throughout the United States. These sites
are designated "Superfund sites." Common Superfund sites include abandoned
warehouses, landfills, and industrial facilities that continually dumped
hazardous waste into the environment before it was regulated.
- TRI (Toxics Release Inventory)-TRI contains information about more
than 650 toxic chemicals that are being used, manufactured, treated,
transported, or released into the environment. Manufacturers of these
chemicals are required to report the locations and quantities of chemicals
stored on-site to state and local governments.
- RCRIS-The database contains an inventory of waste handlers and
information about their waste handling activities. The waste handlers
are classified into three major groups: treatment, storage and dis-posal
(TSD) facilities; waste generators; and transporters.
- Permit Compliance System (PCS)-The Clean Water Act requires
wastewater dischargers to have a permit that establishes pollution limits
and specifies monitoring and reporting requirements. National Pollutant
Discharge Elimination System (NPDES) permits regulate household and
industrial wastes that are collected in sewers and treated at municipal
wastewater treatment plants. Permits also regulate industrial point
sources and concentrated animal feeding operations that discharge into
other wastewater collection systems or that discharge directly into
As you search each of these databases, number and note the facilities you
find in your wellhead protection area on your working map. You might
choose a distinct shape mark to indicate each type of potential pollutant.
If a facility is on a database, but is no longer in operation, indicate
its position on the map, list it in the table, but note its status with a
term descriptive of its condition, like "closed," "abandoned," or
State and Local File Search
State and county files of regulated materials often contain data that has
not been computerized, but recorded on paper in various government
offices. Historic records of land activities and uses may also be
available. These data files must also be searched.
Like the federal databases, the state and local data files can be searched
in two ways, by hiring a consultant to do the search or by doing it
yourself. Someone familiar with the process can search IDEM's files in
three to eight hours. Some consultants who offer this service are listed
on the Safe Water Web site. (See "Indiana Information Contacts.") This
task is not recommended for anyone who is unfamiliar with the process.
However, if you or someone on the planning team chooses to search the
state and local files, you must be aware of the necessary files to include
in your search.
- IDEM's Office of Land Quality maintains files pertaining to landfills,
military bases, dumps, and municipal sewage operations. You may view and
copy this information by visiting the Office of Land Quality file room on
the eleventh floor of the Indiana Government Center North located at 100
North Senate Avenue in Indianapolis. Files are sorted by county and
- IDEM's Office of Land Quality maintains a database known by the
acronym ULCERs. This database contains information on underground storage
tanks, leaking under-ground storage tanks, the Community Right-to-Know
Act, and Emergency Responses to spills. You may use this data-base by
visiting the Office of Land Quality file room on the second floor of the
IDEM office at 2525 North Shadeland Avenue in Indianapolis. These files
are also sorted by county. (NOTE: The Office of Land Quality file room
will be moved to Indiana Govern-ment Center North, 12th floor, by March of
2000.) While your local fire department and Local Emergency Planning
Committee would be another source for Community Right-to-Know data, they
do not have information on underground storage tanks or on emergency
response to spills.
- You can obtain information about pesticides and a request form for
specific county information on pesticide storage in your wellhead
protection area by calling the Office of the State Chemist at 765-494-
1585. This information is on a database that is searched for the area
that you need by personnel in the Office of the State Chemist.
Include the state and county file search information on your working
map. Once the database and file search information is on the map, you
can enlarge sections for your wellhead protection planning team to use
in the site survey for unregulated or otherwise unidentified potential
The Site Survey
Federal and state databases are not 100% accurate, are focused on
facilities using of large quantities of chemicals, and are incomplete with
regard to smaller facilities. Also, the requirement to register
underground storage tanks applies only to those in use after 1986 and only
to those larger than 500 gallons. A facility that closed before current
regulations were in effect could have left behind a source of
contamination. Thus a more thorough survey performed by people who know
the area will offer better protection for your water supply.
This survey is usually completed by community volunteers who drive or walk
through the designated wellhead protection area writing down observations
about the various past and present activities taking place in an area. The
process is often called a "windshield survey" because the observations are
usually made through the windshield of a car. This type of site survey is
the best way to obtain information on non-regulated hazardous materials
that might be in the wellhead protection area.
By getting community members to assist with the collection of this
information you also raise awareness within the community of the
importance of wellhead protection. Try recruiting these volunteers from
local service organizations and retired citizens groups. Try also to get
your local newspaper, radio station, and /or television station to
publicize the event and to communicate the importance of gathering as much
information as possible. For very small communities, posting of fliers and
bulletins can be highly effective. Because successful wellhead protection
depends on cooperation from everyone, educating the public about the goals
and requirements of wellhead protection is essential.
Most hazards to ground water are associated with certain activities. For
example, fertilizer use and pesticide uses are associated with golf
courses, residential and other lawns, and farms and other agricultural
operations. Chemical solvents and oils are associated with machine shops,
auto repair facilities, and certain industrial processes. To clean
clothing, dry cleaning facilities use chemicals that are highly toxic to a
drinking water supply. Armed with the base map showing the delin-eated
wellhead protection area, a few community volunteers can map these and
other unregulated activities that are potentially harmful to a drinking
Historic land use data can be assembled through investigating old Chamber
of Commerce membership files, historical maps and photos, Sanborn
Insurance maps, and Soil and Water Conservation District aerial photos. A
local history buff is a good resource for information. The collective
memory of long-time residents is the best source for historic land use
information, locations of abandoned wells and underground storage tanks,
and other potential contaminant sources. You might also try asking the
local newspaper to run an article requesting people with historical land
use information to contact the local well-head protection planning team.
Steps for Organizing a Site Survey
- Prepare the maps you will need. Enlarged copies of your existing
working map (the map on which you add or compile information about the
sites where regulated use and storage of hazardous materi-als occurs)
should be used for the site survey. The people who will help with this
part of the survey can verify the presence or absence of the regulated
facilities found in the database search while they drive or walk through
their portion of the wellhead protection area. If your wellhead protection
area is large or complex, divide the wellhead protection area into
sections small enough that a couple of people can drive through each
section noting land activities and potential contaminant sources within a
couple of hours. Create a separate map for each section to be surveyed.
- Assemble a group of community volunteers, and divide them into
two-person teams. Try to let each pair choose a section they are familiar
with to survey. Provide each survey pair with a large map of their
specific area (Figure 3) and instructions on how to complete the survey.
(See the "Guide for Wellhead Protection Survey Volun-teers" handout master
copy included at the end of this publication.)
- Have the volunteers complete the survey and return their maps and
notes to the coordinator, the person who will assemble the information
from the various groups. The coordinator should also make sure each
returned map has the names of the surveyors on it, in case there is a
question about the information collected.
- After the coordinator collects the maps and inventory tables, have
one person assemble and organize the information from all the working maps
onto the master map and a master table. Each group of volunteer surveyors
will have numbered the potential contami-nant sources in their particular
section starting with the number "1." This information must be put onto
the master map in a sequence that corresponds to the way it will be
depicted on the table of potential contaminants. It is important that
there is a one-to-one correspon-dence between the map and the table.
- Organize the original inventory sheets according to location, and
keep them as an appendix for your on-site, master copy of the wellhead
protection plan. Later in the wellhead protection planning process, they
may be useful in developing your management strategy.
3. Organize Data
IDEM requires that three things be included in the contaminant source
inventory section of the wellhead protection plan:
- Narrative description of the land uses in the wellhead protection
- Map showing land uses and locations of both regulated and
unregulated potential contaminant sources, and
- Table corresponding to the map.
The Narrative Description
The narrative description you will eventually submit to IDEM with your
completed wellhead protection plan should include background information
on your community water supply system. Include what is known about its
size and age, a description of the size of the wellhead protection area,
and the land activities that are found in the wellhead protection area. As
you can see in the sidebar, "Example of a Narrative Description," this
does not have to be an elaborate or complicated document.
Example of a Narrative Description
The delineated wellhead protection area for Small Town,
IN is an oval
shape extending approximately 2000 feet
to the north and 1200
feet south, east and west of the
well, covering an area of
approximately 200 acres. The
well is six inches in diameter. This well
approximately 150,000 gallons per day and serves a
of 825 people.
Slightly less than half of the delineated wellhead
(approximately 80 acres) is in commercial
usage. The commercial area
includes most of the
downtown area and the country club. There is a
industrial area with a chemical manufacturing company.
is a small residential area on private septic
systems, and the
remainder of the wellhead protection
area is in agricultural land use.
Indiana Highway 32
traverses the wellhead protection area about 1000
south of the wells.
The master map you will submit to IDEM with your wellhead protection plan
should show all the inven-tory information collected for both regulated
and non-regulated contaminant sources from all the working maps.
Double-check to make sure that every potential contaminant source is shown
on the map, and make sure the master map is at the proper scale. (See "A
Note on Map Scale.") Before you send it to IDEM, remember to make a copy
of this master map to keep with your other records.
The Table of Potential Contaminant Sources
The table that you submit to IDEM as the third component of the
contaminant source inventory section of your wellhead protection plan
should list the following information:
Depending on the complexity and size of your wellhead protection area
and on your access to computer resources, you may find it helpful to
use a spreadsheet to keep track of the contaminant source inventory
information. Table 1 shows an example of how the information gath-ered
in the site inventory can be displayed.
- Facility identification number corresponding to the map
- Facility name and address;
- Type of facility;
- Type of potential contaminant;
- Any permit numbers and the organization issuing the permits; and
- Operating status of the facility (open, closed, abandoned, or
Table 1. Example of tabulated information on
potential contaminant sources in the wellhead protection
||Federal and State
||Bill's Service Center
||231 Main St
||gasoline, oil, BTEX
||2994 E. 6th
||gasoline, oil, BTEX
||1337 N 14th St.
||solvent, oil, batteries, antifreeze
||831 Pine St.
||18 River Road
||200 Beck Rd.
||VOC, solvents, bromine
||BJ's Nursery Supply
||321 Juniper Lane
||Circle R Dairy
||250 SR 100 N
||manure, fuel, oil, diesel
|300 SR 100 W
swimming pool chemicals
||State Highway 32
||road salt, gasoline, oil spills from
By completing the contaminant source inventory, your wellhead protection
planning team will have identified the most likely sources of
contamination in your wellhead protection area. At that point, Your team
can begin working on formulating management and contingency plans, and on
developing a program for public education about well-head protection. You
will find information on these topics in future Purdue Extension
publications on wellhead protection planning.
The following Purdue Extension publications provide information
about other aspects of the wellhead protection process.
You may find the following two Purdue Extension brochures to be
useful in your community outreach efforts:
- WQ-2, "What Is Groundwater?"
- WQ-24, "Wellhead Protection in Indiana"
- WQ-28, "Forming the Wellhead Protection Planning Team"
- WQ-29, "A Shortcut to Wellhead Protection Delineation for Some
- WQ-30, "Choosing a Consultant to Delineate the Wellhead
All of the above publications and brochures are available free of charge
through your county Purdue Extension office or by calling 1-888-EXT-INFO.
- "Wellhead Protection: What Every Farmer Should Know About
- "Protecting Your Drinking Water: What Every Citizen Should Know
About Wellhead Protection"
The USEPA has an informative publication, "Wellhead Protection, A Guide
for Small Communities," EPA/625/R-93/002, available free by calling
Sources for Maps and Aerial Photos
- Purdue University (765-496-3209). If you know the name of your quad,
you can send a check for $4 per map, plus $2 for shipping, to LARS, Purdue
University, 1202 Potter Engineering Center Room 376, West Lafayette IN
47907-1202, or e-mail firstname.lastname@example.org. Please include your telephone
number in case more information is needed.
- The Indiana Department of Natural Resources, DNR Map Sales Section,
402 West Washington Street, W-160, Indianapolis, IN 46204- 2742,
(317-232-4180). Maps are $4.20 each, including tax, with a $3.50 shipping
and handling fee.
- The Indiana Geological Survey Publication Sales Office at Indiana
Geological Survey, 611 North Walnut Grove, Bloomington, IN 47405- 2208,
(812- 855-7636). They can determine the proper map to supply if you
provide the name of a town, river, or other named landmark nearby. Maps
are $4 each, plus tax, with a $3 shipping and handling charge.
- Soil and Water Conservation Districts. Most Soil and Water
Conservation Districts have plat maps of counties available for a small
fee. (These maps are usually at a smaller scale than is required and need
to be enlarged.)
- County Clerks, Tax Assessors, and City Engineers. They are other
potential sources for plat maps.
- The State Land Office, 302 W. Washington St., Suite E032,
Indianapolis, IN 46204. Their photos are at a scale of 1 inch equals 400
feet (1:4800) for most of the state, and 1 inch equals 100 feet (1:1200)
for Marion County. Coverage for the whole state is available. The cost is
$3 per sheet (plus shipping). Call James Lewis at 317-232-3335 for
information on how to choose the correct photo-map(s) for your area.
Indiana Information Contacts
- The Purdue Extension office in your county can provide you with
information and resources on water quality protection. Look in the phone
book under county government, or call 1-888-EXT-INFO.
- "Safe Water for the Future" is a Purdue Extension program that
provides resources statewide on wellhead protection and watershed
protection. Call 765-496-6331, or visit our Web site at http://www.ecn.purdue.edu/safewater.
- Indiana Department of Environmental Management, Ground Water
Section, can provide information on Indiana's Wellhead Protection Rule and
compliance. Call the Groundwater Section at 317-308-3321 or 800-451-6027,
ext. 308-3321. Information is also available on the Web at
- Indiana Water and Wastewater Association provides training and
on-site assistance to water supply operators. They can be reached at
1-888-937-4992 or on the Web at
- The Indiana "Rural" Water Association also provides education and
assistance to water supply operators. They can be reached at 812- 988-6631
or (Fax) 812-988-696.
- The EPA Safe Drinking Water Hotline (800-427-4791) is available to
help state and local officials and the public answer questions about
drinking water. The hotline also has information about the National Rural
Water Association's program to assist small communities develop local
drinking water protection plans.
USEPA, 1995, "Benefits and Costs of Prevention: Case Studies of Community
Wellhead Protection-Volume 1," USEPA, EPA 813-B-95- 005.
USEPA, 1993, "Wellhead Protection: A Guide for Small Communities," a USEPA
Seminar Publication, EPA/625/R-93/002.
Whittman, Jack, 1996, "Wellhead Protection Guide," Center for Urban Policy
and the Environment, School of Public and Environmental Affairs,
Witten, Jon and Scott Horsley, 1995, "A Guide to Wellhead Protection,"
Planning and Advisory Service, American Planning Association, PAS Report
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