Wellhead Protection
NATURAL RESOURCES
CORNELL COOPERATIVE EXTENSION
Water and the Soil
by
Nancy M. Trautmann and Keith S. Porter
Center for Environmental Research
and
Robert J. Wagenet
Dept. of Agronomy
Cornell University
Groundwater, the source for wells and springs, supplies drinking water to more
than half of the people in this country and more than 90 percent of the
residents in rural areas. Of the population served by public water supplies,
close to 40 percent rely on groundwater.
Although traditionally groundwater has been assumed to be free from
contamination, numerous discoveries in recent years of toxic chemicals in well
water have proven this assumption to be false. Groundwater contamination from
chemical dump sites tends to attract the greatest public attention, but
contamination from other sources such as septic systems, pesticides, and
underground storage tanks also can be significant.
The 1986 Amendments to the Safe Drinking Water Act established a federal program
to protect the quality of groundwater used in public water supply systems. This
program, called the Wellhead Protection Program, is designed to protect the
surface and underground areas through which contaminants are likely to pass
before reaching a public water system well or wellfield (a group of wells within
a common geographic location). The goal of the program is to delineate the
wellhead protection area for each public water supply well, identify sources of
contaminants within these.areas, and develop management strategies to prevent
well water contamination.
There are many ways to define a wellhead protection area. This must be done,
however, with the understanding that wellhead protection does not end with the
definition of a boundary. To protect the quality of well water supplies, careful
thought and planning must be devoted to identifying and controlling contaminants
within the wellhead protection area boundaries.
Wellhead protection requires the consideration of three factors:
- the nature of potential contaminant sources
- the geographic location of potential sources in relation to the well
- the appropriate management options
Sources with the greatest potential for groundwater degradation should be
subject to the most stringent controls. Similarly, the geographic areas most
vulnerable to well water contamination should be managed more restrictively than
areas at lower risk.
Before developing a wellhead protection program, local officials and water
suppliers should familiarize themselves with the existing state regulations and
programs for groundwater protection. These may include programs related to water
quality, solid wastes, hazardous materials, mineral resources, and many others.
Following an assessment of existing programs and a determination of local goals
and needs, a preliminary conceptual plan can be drawn up for the types and forms
of possible new local management efforts. This plan can help save both time and
money by basing wellhead protection area delineation and management on an
assessment of the local needs and the appropriate degree of technical
sophistication.
A Few Definitions
Water percolates through the soil to become groundwater in a process called
recharge. The amount of water recharged in any particuiar location depends on a
number of factors, including climate, land use, topography, and geological
conditions.
Groundwater moves through the ground, below the place where it first enters the
soil to the area where it later resurfaces (fig. 1. See fact sheet). Flow rates
typically are measured in inches or feet per day, although they can be much
faster in coarse gravel or in bedrock with large openings or crevices.
Groundwater tends to move in parallel paths, with little vertical mixing between
layers (fig.1. See fact sheet). Geological formations that yield significant
amounts of groundwater are called aquifers.
Aquifers can be divided into two basic types. Unconfined aquifers have an upper
water surface that is free to rise and fall depending on the volume of
groundwater present. The groundwater surface in an unconfined aquifer is called
the water table. The level of water in a well tapping an unconfined aquifer is
the same as that of the surrounding water table (fig. 2. See fact sheet).
Confined or artesian aquifers contain groundwater that is trapped under a layer
of impermeable material such as clay. Hydraulic pressure causes water in an
artesian well to rise above the top of the aquifer (fig. 3. See fact sheet).
Some aquifers consist of porous media such as sand and gravel. Others occur
where groundwater fills cracks and openings in bedrock or where groundwater has
dissolved caverns in limestone or gypsum bedrock. These aquifers may have high
rates of flow and little filtering of contaminants compared with aquifers in
porous media.
Groundwater movement is affected by the pumping of wells. When water is
withdrawn from a well, the water table around the well is lowered, and
groundwater from surrounding areas flows toward the well to compensate. The
lowered water table around a well is called the cone of depression (fig. 4. See
fact sheet). The size and shape of the cone of depression depend on many
factors, including the rate and duration of pumping, the rate of groundwater
recharge, and the geology of the aquifer.
The area at the land surface lying directly over the cone of depression is
called the zone of influence (fig. 4. See fact sheet). Although the zone of
influence indicates the area in which the water table elevation is affected by a
well, it does not necessarily coincide with the land area contributing recharge
water to the well. This area, called the zone of contribution, usually is larger
than the zone of influence. It may include parts of the zone of influence or
extend miles from the well location, depending on the type of aquifer being
tapped.
Groundwater Contamination
Whether well water is taken from individual wells or large community wellfields,
the concepts behind its protection remain the same. The concept of utmost
importance is that groundwater originates at the earth's surface, so its quality
is determined by land uses and chemical management practices such as
fertilization, chemical waste disposal, or petroleum storage. Groundwater
contamination typically results from activity on, or just below the land
surface. As water percolates through the soil, it may pick up contaminants and
carry them downward to groundwater.
Most human-caused groundwater contamination results from the interaction of
recharge water with chemicals at or just below the land surface. Chemicals may
be deliberately placed in or on the soil for a specific reason; for example,
pesticides are sprayed to protect crops, and gasoline is stored in underground
tanks for later use. Waste chemicals may be inadvertently spilled or
deliberately applied to land for disposal.
Soluble chemicals, which readily dissolve in water, move with groundwater as it
flows. Insoluble chemicals do not mix fully with groundwater, and their flow
patterns depend on their densities relative to water. The rates of movement and
degradation of the compounds depend on a variety of chemical, physical, and
biological processes.
Knowledge of groundwater flow patterns is important in preventing the
contamination of zones of groundwater tapped by water supply wells. Tracing
groundwater flow backward (upgradient) from a well to its recharge area on the
land surface makes it possible to identify and prevent potential contamination
problems.
Delineation of Wellhead Protection Areas
Wellhead protection means the protection of the land area around a well. The
Safe Drinking Water Act defines a wellhead protection area as the surface and
subsurface area through which contaminants are likely to pass before reaching a
well or group of wells used for public water supplies.
A wellhead protection area can be divided into zones to allow for varying
degrees of management relative to the sensitivity of each zone to groundwater
contamination. For example, the outer boundaries might be drawn to protect all
recharge water to a particular well, based on the zone of contribution (fig. 4.
See fact sheet). Within these outer boundaries, inner zones could be delineated
using any of various methods, criteria, or thresholds for wellhead protection.
The zone requiring the most restrictive management, for example, could be
designated as the area immediately surrounding the well or the area from which
groundwater is expected to reach the well within a relatively short time.
The criteria used to delineate wellhead protection areas depend on the type of
aquifer and the degree of protection desired. Criteria commonly used include:
- distance from the well
- drawdown of the water table
- flow boundaries
- time of travel
- assimilative capacity
Each of these delineation techniques is discussed below. Other considerations
also are important, including the existing degree of development, the local
goals for groundwater protection, and the existing regulatory system for
controlling potential contaminants.
Distance from the Well. The simplest method of delineating an area for
wellhead protection involves drawing a circle around the well, with the idea
that the land area closest to the well is in greatest need of protection. The
radius of such a circle typically extends up to several thousand feet from a
well.
Depending on the properties of the well and the contributing aquifer, the land
immediately surrounding a well may or may not be part of the area from which the
well's recharge is derived. Even in the case of a distant recharge area,
however, protection of the land surrounding a well can help prevent well water
contamination. If well casings are not properly sealed, for example,
contaminants introduced at the land surface could leak into the aquifer along
the well casing.
Drawdown of the Water Table. A slightly more sophisticated approach to
protecting the land surrounding a well is to delineate the zone of influence, or
the land area under which the water table is lowered by well pumping (fig. 4.
See fact sheet). Drawdown of the water table is greatest at the well and
diminishes with increasing distance.
Although protection of the area immediately surrounding a well will help prevent
contamination from bacteria and viruses, it is unlikely to provide complete
protection from chemical contaminants. Since many chemicals can be transported
long distances underground without being filtered out or degraded, keeping them
out of well water requires keeping them out of any recharge water that will
eventually reach the well.
Delineation of wellhead protection areas based on distance from the well or on
drawdown of the water table is most appropriate for shallow wells in unconfined
aquifers. For artesian wells or wells tapping deep aquifers, a different
approach may be required because the recharge areas may extend far from the well
location. Even in such cases, however, protection of the land surrounding the
well may help prevent problems such as the penetration of contaminants down the
well casing.
Flow Boundaries. For the most thorough protection of a particular well,
the wellhead protection area should encompass all the land from which recharge
water is derived (the zone of contribution, fig. 4. See fact sheet). All water
recharging the aquifer within the zone of contribution is eventually drawn to
the well by pumping. If the rate or duration of pumping changes, then the size
of the zone of contribution changes as well. Weather conditions also may affect
the zone of contribution. During a drought, for example, the rate of recharge
diminishes, so the area drawn upon by a well increases.
In some cases the wellhead protection area is expanded to include land areas
that are not directly within the recharge area of a well, but which send
overland runoff into the recharge area. Some of this runoff may seep into the
ground in the recharge area, along with any contaminants that have been carried
along.
Time of Travel. Another approach to designating wellhead protection areas
is to base the boundaries on the estimated time of travel of groundwater or
contaminants to the well. For example, a line can be drawn around the area from
which groundwater is expected to reach the well within a month, a year, or any
other chosen period. Since the rate of contaminant travel is likely to be equal
to or lower than that of groundwater, using groundwater travel times provides a
conservative estimate of contaminant travel times as well.
Assimilative Capacity. Wellhead protection areas can also be designated
based on assimilative capacity, the degree to which contaminants are degraded or
diluted as they travel to and through groundwater. The idea is to protect a
sufficiently large area around a well so that any contaminants entering with
recharge water will be diminished to acceptable concentrations by the time the
groundwater reaches the well. An example of well protection based on
assimilative capacity is the use of density criteria for planning houses with
septic systems.
Because the rate at which groundwater contaminant concentrations will diminish
depends on the contaminant, the soil type, and groundwater flow conditions,
assimilative capacity must depend both on the specific site conditions and on
the properties of the specified contaminants. This approach therefore has
limited use, confined to areas in which relevant data are available.
Aquifer Protection. All the above methods delineate wellhead protection
areas based on providing protection to specific identified wells. In New York
State, a broader definition of wellhead protection areas is used. Because state
law calls for a level of protection that ensures groundwater meets drinking
water standards, the wellhead protection areas encompass entire aquifers or
aquifer segments rather than recharge areas for specific wells. In this way,
protection also is provided for future, as yet undetermined, well sites. Within
these broadly defined wellhead protection areas, smaller areas are delineated
for extra protection of individual public water supply wells.
In upstate New York, most of the highly productive aquifers consist of
relatively thin layers of glacial deposits in river valleys that are generally
less than one or two miles wide(fig.5. See fact sheet).The state has defined the
wellhead protection areas to encompass these aquifers in entirety, with smaller
areas to be delineated for additional protection to the land surrounding each
public water supply well.
On Long Island, the deep-lying Magothy and Lloyd aquifers underlie the entire
island and supply a large number of wells, some of which are far removed from
the recharge areas (fig. 6. See fact sheet). The shallower Upper Glacial aquifer
also is tapped by many wells, both public and private. Wellhead protection on
Long Island therefore has two goals: protection of the land that provides
recharge water to the two deep aquifers, and protection of the area immediately
surrounding each public water supply well. (For further information on wellhead
protection in New York State, contact the Groundwater Management Section, New
York State Department of Environmental Conservation, 625 Broadway, Albany, NY
12233-3508.)
Protection Techniques
As part of the process of delineating wellhead protection areas, decisions need
to be made about how these areas will be protected. Based on a determination of
local goals for groundwater protection and an evaluation of existing mechanisms
for controlling potential contaminant sources, local officials can decide what
additional management or enforcement is needed.
Tables 1 and 2 outline some of the regulatory, nonregulatory, and legislative
approaches to wellhead protection. Options vary greatly in the level of
protection attained. The highest level of protection is provided by public
purchase of the recharge area so that the land can be kept in its natural state.
In many cases this is infeasible, either because of prohibitive expense or
because the area already has been developed. Then the choice becomes one of how
to control contaminants from existing, historical, and expected future land
uses.
An inventory of potential contaminant sources should include ongoing sources,
sources from the past, and expected sources from projected land uses. It should
also include a review of existing regulatory programs that might address such
sources.
Mapping existing land uses and taking an inventory of chemical disposal
practices provide information about current contaminant sources. Protective
measures might include the exclusion, containment, or treatment of selected
potential contaminants, depending on the properties of the site, the existing
regulatory framework, and the chemical characteristics of the contaminants of
concern.
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Table 1. Regulatory Techniques for Wellhead Protection 1
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Regulatory Technique Description
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ZONING ORDINANCES
Down-zoning For land that is zoned for intensive use but not yet
developed, "down-zoning" can ensure a less intensive
eventual use.
Phase-ins If existing development is incompatible with wellhead
protection, new zoning requirements may be "phased
in" over time.
Large-lot zoning In residential areas with septic systems, large-lot
zoning preserves open spaces and provides dilution
for the effects of septic system leachate on
groundwater.
Conditional zoning Certain land uses are allowed, while others are
allowed only under specified conditions (often used
in conjunction with Site Plan Review).
Floating zones Floating zones are defined by specified land
conditions, not necessarily delineated on a zoning
map. Developers must demonstrate that proposed
projects conform to whatever specifications are
required.
Cluster zoning Zoning density requirements are altered to allow
residential planned unit development to cluster into
one section of the site, leaving the remainder as
open space.
Incentive or bonus Clustered zones are promoted by allowing extra
zoning development in the clustered area in exchange for
preserving the remainder of the site as open space.
Overlay zoning An existing zoning map is overlaid with additional
zoning, which imposes special regulations for
wellhead protection areas.
SUBDIVISION Subdivision ordinances apply when a land parcel is
ORDINANCES divided into lots for sale or development. They may
be included in zoning or used where no zoning
ordinance is in effect.
SITE PLAN REVIEW Proposed development projects are reviewed by a local
authority for compatibility with existing land uses
and environmental considerations.
DESIGN OR Standards covering features such as drainage,
OPERATING recharge basins, or chemical storage facilities can
STANDARDS be imposed on the design and operation of new
development projects.
SOURCE The storage or use of dangerous materials is
PROHIBITIONS prohibited from a defined area.
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1 More information on these techniques can be found in Wellhead Protection
Programs: Tools for Local Governments (U.S. Environmental Protection Agency,
1989).
Because most groundwater moves very slowly, a contaminant may not appear in a
well until many years after it enters groundwater with recharge water. For this
reason, an inventory of potential contaminant sources must also include
historical information. From an analysis of historical aerial photographs taken
at intervals through the years, professionals can identify potential problem
areas such as:
- abandoned dumps or landfills
- pits or lagoons used for chemical disposal
- stockpiles of barrels or other hazardous waste containers
- fuel or chemical storage tanks, or prior industrial sites
If potential contaminant sources such as these are found, remedial measures can
be devised for containment or treatment.
Future contaminant sources can be analyzed by asking what would happen if the
land within the wellhead protection area were developed to the maximum extent
allowed by existing zoning or other regulatory statutes. One common contaminant
used for planning purposes is nitrate, which is added to groundwater by septic
systems and by the leaching of fertilizers. By determining the sources and fates
of nitrogen at a specific site, decisions can be made about which land uses and
fertilization practices will be able to attain specified water quality goals.
For example, various densities of unsewered residential development can be
analyzed to determine which will provide acceptable levels of nitrate in
groundwater recharge (see, for example, Hughs and Pacenka 1985, Hughes and
Porter 1983, Hughes et al. 1985, Pacenka et al. 1984, or Trautmann et al. 1983).
The limitation of this approach is that it does not take into account other
contaminants, many of which do not act in the same manner as nitrate.
Within a wellhead protection area, some land areas may be given higher priority
than others because of their greater vulnerability to groundwater contamination.
Using overlay maps of soil type, permeability, and depth to groundwater, the
land areas in greatest need of protection can be identified. Maps can be drawn
identifying zones such as these:
- the land immediately surrounding each public water supply
- the area supplying recharge water to each public well
- the recharge area for the entire aquifer, or the part of the aquifer located
within the community's boundaries
Land use regulations and ordinances can then be tailored to the specific
vulnerability of each site. Zoning ordinances, for example, can be used to
direct new development primarily to areas outside the wellhead protection
boundaries. If zoning already is in place, additional wellhead protection zones
can be superimposed using overlay zoning, in which special restrictions are
applied to development in key areas. Cluster zoning can be used to cluster
developments beyond wellhead protection area boundaries, reserving the prime
recharge areas for open space uses.
Another means of limiting development in key areas is through the restriction of
major capital improvements such as roads, sewers, and water mains, which are
essential for intensive development. In some cases, however, sewers carrying
wastewater away from the wellhead protection area make more sense than septic
systems within its boundaries.
Educational programs are a key to community understanding of and support for
groundwater protection programs. One topic of primary concern is the proper
handling of hazardous materials, by homeowners as well as commercial and
industrial establishments. Communities can facilitate the voluntary use of
proper disposal practices by providing lists of acceptable disposal methods for
various chemicals and reputable hazardous waste haulers. (See, for example,
Disposal of Hazardous Waste, a fact sheet produced by Cornell Cooperative
Extension, New York State College of Human Ecology, and available from:
The Resource Center
PO Box 3884
Ithaca, NY 14852-3884
Fax: 607-255-9946
Email orders: resctr@cornell.edu
Online orders:
http://www.cce.cornell.edu/store)
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Table 2. Nonregulatory and Legislative Techniques for Wellhead Protection 1
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Technique Description
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NONREGULATORY
PURCHASE OF PROPERTY OR DEVELOPMENT RIGHTS
Acquisition of fee Fullest control over land uses is
achieved by public interests
acquisition. Publicly owned wellhead
protection areas can be restricted to
public access or used for park land.
Acquisition of partial interests Communities can purchase development
rights, conservation easements, or
restrictive covenants limiting what
uses can be applied to the land.
GROUNDWATER MONITORING Developers may be required to monitor
groundwater quality downgradient from
their development.
HAZARDOUS WASTE COLLECTION To promote safe disposal of household
hazardous waste materials, communities
can sponsor hazardous waste collection
days.
PUBLIC EDUCATION Communities can sponsor public
education relating groundwater quality
to topics such as the proper handling
and disposal of household hazardous
waste, septic system maintenance, or
fertilization and pesticide
application practices.
LEGISLATIVE
REGIONAL WELLHEAD PROTECTION For protection of regional aquifer
AREA DISTRICTS systems, states can create legislative
districts to transcend existing
jurisdictional boundaries.
LAND BANKING State governments can empower local
governments to impose a tax on land
sales, with the revenues to be used to
acquire and protect land within
wellhead protection areas.
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1 More information on these techniques can be found in Wellhead Protection
Programs: Tools for Local Governments (U.S. Environmental Protection Agency,
1989).
Conclusion
The traditional assumption that groundwater provides a source of pure water is
not valid unless deliberate steps are taken to ensure the quality of this
supply. Groundwater contaminants typically are invisible, often tasteless, and
may take years to travel from their source to a water supply well. Once it has
occurred, groundwater contamination may be infeasible to clean up, and expensive
alternative water supply measures may be required. Primary emphasis, therefore,
must be on preventing contamination at its source rather than on treating the
problem after contaminants are discovered in public water supply wells.
Groundwater originates from water seeping downward through the soil from the
land surface. Groundwater quality, therefore, is determined by land uses and
chemical management practices, and efforts to protect groundwater supplies must
rely on keeping contaminants out of the recharge water.
Wellhead protection areas can be designated using maps of groundwater flow to
wells, and site-specific management plans can be developed designating the most
appropriate protective measures for each wellhead area. These protective
measures vary widely, ranging from community education about proper chemical use
and disposal to public acquisition and management of critical recharge areas.
Land development and the use of toxic chemicals are steadily increasing in this
country, as is our reliance on groundwater supplies. Clearly, protective
measures will become ever more critical to ensure the availability of high-
quality groundwater for both present and future uses.
For Further Reference
Freeze, R.A., and J.A. Cherry. 1979. Groundwater. Englewood Cliffs, N.J.:
Prentice-Hall, Inc.
Frimpter, M.H., J.J. Donohue, and M.V. Rapacz. 1990. A Mass-Balance Nitrate
Model for Predicting the Effects of Land Use on Ground-Water Quality. Boston,
Mass.: U.S. Geological Survey, Open-File Report 88-493. (Available from Books
and Open File Reports Section, U.S. Geological Survey, Box 25425, Federal
Center, Denver CO 80225.)
Hughes, H.B.F., and K.S. Porter. 1983. Land Use and Ground Water Quality in the
Pine Barrens of Long Island. Ithaca, N.Y.: Water Resources Program, Cornell
University. (Available from New York State Water Resources Institute, Wing Hall,
Cornell University, Ithaca, NY 14853.)
Hughes, H.B.F., J. Pike, and K.S. Porter. 1985. Assessment of Ground-Water
Contamination by Nitrogen and Synthetic Organics in Two Water Districts in
Nassau County, N.Y. Ithaca, N.Y.: Water Resources Program, Cornell University.
(Available from New York State Water Resources Institute, at address above.)
Hughes, H.B.F., and S. Pacenka. 1985. BURBS: A Simulation of the Nitrogen Impact
of Residential Development on Groundwater. Microcomputer software for use with
Lotus 1,2,3 on an IBM-compatible computer. Ithaca, N.Y.: Center for
Environmental Research, Cornell University. (Available from Northeast Regional
Agricultural Engineering Service, Riley Robb Hall, Cornell University, Ithaca,
NY 14853.)
Pacenka, S., M.J. Heather, K.S. Porter, K. Hoover, B. Silverman, and L. Maller.
1984. Protecting Ground-Water Supplies in River Valley Communities. Ithaca,
N.Y.: Cornell Cooperative Extension, Miscellaneous Bulletin 131. (Available
from:
The Resource Center
PO Box 3884
Ithaca, NY 14852-3884
Fax: 607-255-9946
Email orders: resctr@cornell.edu
Online orders:
http://www.cce.cornell.edu/store)
Raymond, L.S. Jr. 1988. What Is Groundwater? WRI Bulletin No. 1 . Ithaca, N.Y.:
Water Resources Institute. (Available from The Resource Center, at address
above.)
Raymond, L.S. Jr. 1988. Groundwater Contamination. WRI Bulletin No. 2. Ithaca,
N.Y.: Water Resources Institute. (Available from The Resource Center, at address
above.)
Raymond, L.S. Jr. 1986. Chemical Hazards in Our Community: Options for Community
Action. Ithaca, N.Y.: Water Resources Institute. (Available from Water Resources
Institute, 468 Hollister Hall, Cornell University, Ithaca, NY 14853.)
Trautmann, N.M., K.S. Porter, and H.B.F. Hughes. 1983. Southold Demonstration
Site: New York State Fertilizer and Pesticide Demonstration Project. Ithaca,
N.Y.: Water Resources Program, Cornell University. (Available from New York
State Water Resources Institute, at address above.)
U.S. Environmental Protection Agency. 1989. Wellhead Protection Programs: Tools
for Local Governments. EPA 440/6-89-002. Washington, D.C.: U.S. Environmental
Protection Agency.
U.S. Environmental Protection Agency, Office of Ground-Water Protection. 1987.
Guidelines for Delineation of Wellhead Protection Areas. Washington, D.C.: U.S.
Environmental Protection Agency.
U.S. Environmental Protection Agency, Office of Ground-Water Protection. 1987.
Surface Geophysical Techniques for Aquifer and Wellhead Protection Area
Delineation. EPA 440/12-87-016. Washington, D.C.: U.S. Environmental Protection
Agency.
U.S. Environmental Protection Agency, Office of Ground-Water Protection. 1987.
Wellhead Protection, A Decision-Makers' Guide. EPA 440/6-87-009. Washington,
D.C.: U.S. Environmental Protection Agency.
Other fact sheets in this series include:
Modern Agriculture: Its Effects on the Environment (400.01) Nitrate: Health
Effects in Drinking Water (400.02) Pesticides: Health Effects in Drinking Water
(400.03) Groundwater: What It Is and How to Protect It (400.04) Water and the
Soil (400.05) Nitrogen: The Essential Element (400.06) Pesticides and
Groundwater: A Guide for the Pesticide User (400.07)
These fact sheets are available from:
The Resource Center
PO Box 3884
Ithaca, NY 14852-3884
Fax: 607-255-9946
Email orders: resctr@cornell.edu
Online orders:
http://www.cce.cornell.edu/store
Acknowledgments: Illustrations were drawn by Lucy Gagliardo, and Mary Jane
Porter served as production assistant. Funding was provided by the New York
State Farmers' Fund. Special thanks go to the following individuals for their
review of preliminary drafts: Eugenia Barnaba, Ann Lemley, June Fessenden
MacDonald, Steven Pacenka, Lyle Raymond, R. David Smith, Linda Wagenet, and Mark
Walker, Cornell University; Norbert Dee and John Malleck, U.S. Environmental
Protection Agency; Kevin Roberts and Al Tedrow, New York State Department of
Environmental Conservation; and John Williams, U .S. Geological Survey.