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Maine’s Source Water Protection Program is administered by:
Drinking Water Program
Department of Human Services Division of Health Engineering
11 State House Station, 161 Capital Street, Augusta, ME 04333-0011
tel: 207/287-2070 • tty: 207/287-5550 • fax: 207/287-4172
http://www.medwp.com
This digest is a publication of:
Senator George J. Mitchell Center for Environmental and
Watershed Research
5710 Norman Smith Hall, Orono, ME 04469-5710
tel: 207/581-3244 • fax: 207/581-3320
PROTECTING MAINE'S GROUNDWATER SUPPLIES: MAINE'S SOURCE WATER
PROTECTION PROGRAM
Groundwater basics
Wellhead protection and source water
protection
Delineation
Potential contamination sources within the
source water protection area
Contingency planning and security
Managing wellhead protection and source water
protection areas
Roles of public water suppliers, governments, and
organizations
Public water systems
Contacts for additional information
 More
than 60% of Maine citizens rely on groundwater for their public and
private drinking water supplies. Various land uses and activities
threaten the quality of this valuable natural resource. Once
groundwater is contaminated, it is difficult and expensive, and
sometimes impossible, to clean up. Protecting groundwater from
contamination is the most effective method to ensure abundant
sources of clean drinking water. Land development has been
identified as the dominant threat to public water supplies, and
controlling land use through purchase, easement, or ordinance is the
greatest challenge facing public water systems.
The goal of Maine's Source Water Protection Program is to protect
the state's 2,100+ public water systems from the threat of
contamination. As required by the Federal Safe Drinking Water Act
Amendments of 1986, the Wellhead Protection Section of the program
focuses on public water supply wells rather than private wells. The
public wells serve more people and thus their management is more
practical than that of thousands of private wells. This digest
focuses on groundwater, but it does apply to surface water supplies
since groundwater can be a significant input to surface water
sources. Up to one-third of the water in rivers and lakes can be
from groundwater input, therefore protecting surface water quality
also requires protection of the groundwater component.
This digest is organized in two parts: 1) a summary of important
groundwater principles that are fundamental to source water
protection and 2) a discussion of the key elements of the Maine
Wellhead and Source Water Protection Program.
GROUNDWATER BASICS
Groundwater is the source of water for wells and springs, and is
found beneath all land in Maine. Groundwater occurs within the
cracks or fractures in bedrock, and in spaces between soil
particles. The zone in which all of these fractures and spaces are
filled with water is called the saturated zone. The upper
surface layer of the saturated zone is the water table
(Figure 1).
Figure 1. Divisions of Subsurface Water
Groundwater is part of the hydrologic cycle (Figure 2).
Water falls as rain or snow to the land surface and infiltrates the
soil or flows over land into streams, rivers, lakes, and oceans.
Some of this water evaporates back into the air from wet surfaces or
is released by growing plants. Water entering the soil fills open
spaces in the unsaturated zone, and infiltrating water percolates
downward to the water table and replenishes (recharges) the
groundwater.
Figure 2. The Hydrologic Cycle
Only a fraction of total precipitation ends up as groundwater.
The amount of precipitation that enters the soil as potential
groundwater recharge depends on several factors including soil type
(Table 1), slope of the land surface, and vegetative cover. For
example, although Maine receives an average 42 inches of
precipitation per year, only two to five percent of this
precipitation recharges groundwater in areas underlain by fractured
crystalline bedrock.
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Table 1.
Recharge Potential for Typical Maine Geological Deposits |
| Surficial Deposit |
Avg. Annual
Recharge Rage
(% of annual precipitation) |
Equivalent Gallons
per Acre |
| Sand and gravel |
40% - 50% |
478,000 to 597,900 |
| Clay/silt |
5% - 15% |
59,700 to 179,200 |
| Thick silty glacial till |
5% - 15% |
59,700 to 179,200 |
| Thick course-grained till |
15% - 35% |
179,200 to 298,700 |
| Thin sandy glacial till over bedrock |
5% - 20% |
59,700 to 238,900 |
| Fractured bedrock |
2% - 5% |
23,900 to 59,700 |
Areas that supply water directly to a groundwater source are
called recharge areas. Recharge areas occur primarily in
upland areas (Figure 3). Gravity causes groundwater to move
downgradient (downhill) from recharge areas to lower regions where
it discharges as surface water in springs, seeps, lakes, and rivers.
In Maine, where only a thin layer of soil and broken rock overlies
bedrock, groundwater follows the slope of the land surface, moving
from hilltop to valley.
Figure 3. Recharge and Discharge Areas in a Groundwater Flow
System
Geologic deposits are generally classified as either aquifers,
which contain water, or confining layers. An aquifer is a
subsurface layer of earth or permeable rock that yields useful
quantities of groundwater to wells and springs. There are two types
of aquifers in Maine: surficial and bedrock. Surficial or
unconfined aquifers receive groundwater recharge directly from
precipitation, and consist of a mixture of soil and broken rock
deposited by glaciers. Sand and gravel aquifers, which can yield up
to 50 gallons of water per minute, are a kind of surficial aquifer
formed thousands of years ago by melting glacial ice. Glacial
meltwater streams drained toward the ocean, depositing sand and
gravel along valleys in southern and eastern Maine. In bedrock
aquifers, water is stored in tiny cracks and fractures in the
solid rock below surficial deposits.
Confining layers are low-permeability deposits (such as clay
or unfractured bedrock) that restrict the movement of groundwater
between aquifers. An aquifer that underlies a confining layer and is
completely filled with groundwater (under pressure) is considered a
confined aquifer. In Maine, confinement is usually the result
of fracture patterns in the bedrock. Such an aquifer may receive its
water from locations some distance away. Whether an aquifer is
surficial or confined has important implications for wellhead
protection because the wellhead protection area for confined
aquifers is more difficult to identify.
"Water table" wells tap surficial aquifers, and the water
level in these wells is the same as the surrounding water table. In
wells drilled into confined aquifers, sometimes called "artesian
wells", the water level rises above the top of the aquifer (but
not necessarily to the land surface) to match the water pressure
within the aquifer. It is common to refer to all wells drilled in
bedrock as artesian, although many are not. True artesian wells are
free-flowing: water trapped in deep-lying rock develops considerable
pressure, which when tapped by a well is enough to cause the water
level to rise above the land surface.
How much water a well can yield depends on the nature of the
overlying material and the number and size of fractures in the
bedrock. Thick sand and gravel deposits are excellent aquifers for
public water supplies, and some yield from 10,000 to over one
million gallons per day. Most of Maine's larger groundwater-based
water systems tap sand and gravel aquifers.
Surface water bodies can influence water supply to a well. Wells
near major lakes and rivers often induce recharge from these rivers
and lakes; such wells are considered "groundwater under the
influence of surface water". When recharge is below normal, such as
during a drought, the contribution of surface water to a well can
increase.
Most Maine households consume a few hundred gallons of water per
day. For planning purposes, public water suppliers estimate that
each person consumes approximately 60 gallons per day. A public
water system supplying 2,000 persons would require approximately
120,000 gallons per day to satisfy residential demands. The water
requirements of the commercial sector would depend on both the
number and types of businesses. A manufacturing business or a
restaurant may require substantially more water than a clothing
retail store, for example.
WELLHEAD PROTECTION and SOURCE WATER
PROTECTION
All groundwater is vulnerable to contamination. The 1986 Amendments
to the Safe Drinking Water Act required the states to develop
Wellhead Protection programs to define and protect the source
protection area around public groundwater wells. Each state was also
required to identify and rank activities in the source protection
area that may threaten water quality.
A decade later, the 1996 Amendments to the Safe Drinking Water Act
required public water systems to evaluate all public water systems
as part of a Source Water Assessment Program. Similar to the
Wellhead Protection Program, Maine's Source Water Assessment Program
assessed the current and future threats to water quantity and
quality of Maine's public water supplies. The EPA requires that each
assessment include a delineation of the source water protection area
(which for groundwater is the same as the wellhead protection area),
an inventory of potential sources of contamination within the source
water protection area, and an assessment of the susceptibility of
the supply to those threats. For groundwater systems, most of this
information was already submitted as part of the previous Wellhead
Protection Program, and the Source Water Assessment Program
emphasizes predicting and preventing contaminant threats.
The Maine Wellhead Protection Program is a voluntary program.
Participating water systems are eligible for waivers to some water
tests and monitoring; because of this incentive, most of the larger
systems are involved in the program. Systems involved in the
Wellhead Protection Program were required to develop the following
information: delineation of the protected area, an inventory of
potential sources of contamination, a management plan to mitigate
current threats and prevent future threats, and a contingency plan
to deal with emergencies that affect service from a well.
What are the benefits of having a Wellhead Protection Plan? Without
wellhead protection, public water suppliers must rely solely on
enforcement of existing regulations for groundwater protection. The
major benefit of developing a wellhead protection plan is the
ability to control and prevent contamination specifically within the
local source protection area and to effectively implement cleanup
measures if an accidental spill occurs. By identifying the source
protection area and performing an inventory of the potential
contamination sources, the public water supplier can more
effectively educate the public and enlist public participation for
resource protection.
DELINEATION
A source protection area delineation maps the likelihood that well
water is derived from a particular area of the land surface.
Ideally, a source protection area includes all of the land area
which contributes groundwater recharge to a well; this area is
called the recharge area (also referred to as the zone of
contribution or contributing area).
The source of water to a well is influenced by the regional flow of
groundwater in the area. In an aquifer with no flow, a well would
draw water equally from all directions.
In reality, the geometry of the aquifer and regional flow through
the aquifer influence where the well obtains its water. In many sand
and gravel aquifers, the gradient is relatively flat under
non-pumping conditions. The gradient is usually parallel to the
topographic slope, and this slope is used to approximate the
regional groundwater flow gradient.
The recharge area is different from the cone-shaped depression,
commonly called the cone of depression or the zone of influence,
which develops in the water table around a pumping well. The cone of
depression extends laterally from a well so that the rate of ground
water recharge to the well equals the rate of pumping or withdrawal.
Under idealized aquifer conditions with a flat water table, the
recharge area is equivalent to the zone of influence; more often the
two areas overlap but do not coincide. In order to be effective,
programs to protect groundwater quality focus on the recharge
process because recharge controls both the quantity and quality of
water reaching a well. Delineating a recharge area can help water
suppliers target land for special protection measures.
Groundwater systems in the Wellhead Protection Program were required
to delineate a protection area around each well or group of wells.
For transient systems, the source protection area was delineated as
an arbitrary circle around the well with a fixed radius of 300 feet
(Figure 4). For other small systems, a calculated fixed radius
method was used, with areas ranging from 300 to 2,500 feet in
radius, based on population served or pumping rate. In many cases,
this was probably the only feasible approach given the cost of
determining a more geologically reasonable protection area.
Figure 4. WHPA Delineation Using the Arbitary Fixed Radius
Method
The Drinking Water Program, in cooperation with several other
agencies including the Maine Geological Survey, has refined wellhead
protection area delineations for the 139 sand and gravel well
sources serving more than 250 people. The 200-day and 2,500-day
time-of-travel zones for sand and gravel wells were analyzed using
geologic maps, pump test data, groundwater level monitoring data,
and computer modeling (Figure 5). Computer model simulations were
then used to estimate groundwater flow paths and capture zones for
the individual public water systems. The models simulate groundwater
flow through the geological materials around the well, calculate
recharge areas, and estimate time-of-travel to the well.
Figure 5. Example of Multiple Wellhead Protection Zones Based
on Time-of-Travel Concept
The Drinking Water Program, with Maine Geological Survey, has
also evaluated and refined delineations of the contributing areas to
public water supplies utilizing bedrock aquifers. Most public water
systems lack adequate hydrogeologic data and resources to invest in
extensive hydraulic testing and investigations of their water supply
wells. Yet for bedrock wells, a fixed radius circle is a poor
representation of the zone of contribution. A combination of
hydrogeologic mapping and groundwater flow modeling was used to
determine recharge zones of bedrock wells. The resulting recharge
areas do not take the form of a fixed-radius circle (Figure 6).
Figure 6. Example of recharge area delineations for a bedrock
well
POTENTIAL CONTAMINATION SOURCES
WITHIN THE SOURCE WATER
PROTECTION AREA
Once the source protection area was delineated, potential
groundwater contamination sources within the area were identified
and mapped. Participating systems submitted an inventory to the
Drinking Water Program, based on a list of 76 potential contaminants
and contaminant sources (Table 2). Inventories were revised as part
of the Source Water Assessment Program; it is the public water
supply manager's role to periodically review and update the
inventory of potential contaminant sources.
Hundreds of chemical and biological substances that are used or
generated by agriculture, industry, or households are potential
contaminants. Accidental releases of contaminants to soil and
groundwater are widespread and common. Contaminants often found in
Maine groundwater include petroleum compounds, cleaning solvents,
pesticides, heavy metals, nitrate, chloride, sodium, and bacteria.
Potential contaminant sources are also ranked based on the relative
risk they pose to the water supply.
CONTINGENCY
PLANNING and SECURITY
What happens if a chemical spill occurs in the source protection
area or the water supply is declared unsafe to drink? The final
step for completing a wellhead protection program will be a
contingency plan for emergencies. While detailed contingency
plans will only be required of threatened Category III and all
Category IV systems, all public water supplies should be
prepared to deal with accidental and intentional disruptions of
water quantity or quality. In addition, the EPA requires every
public water system that serves a population greater than 3,300
to complete a vulnerability assessment and develop an emergency
response plan based on the assessment.
A contingency plan should encourage the quickest emergency
response possible and minimize the amount of contaminant
released. Planning involves knowing whom to call in an
emergency, but also making sure local law enforcement and County
Emergency Planning Commissions know to notify the water supplier
if and when the water supply is threatened. Other components of
a contingency plan include an efficient and effective process
for alerting the water system customers and identification of
back-up water supplies. An alternative water supply should be
outside of the source protection area and brought on-line within
24 hours of system contamination or failure.
Public water systems experiencing an active threat to the water
supply should follow the Security Response Protocols developed
by the Drinking Water Program. |
MANAGING WELLHEAD PROTECTION AND
SOURCE WATER PROTECTION AREAS
All public water systems have received a copy of their Source Water
Assessment Program report from the Drinking Water Program, which
will aid in development of a management plan. The reports are also
available on the Drinking Water Program website. The Source Water
Assessment ranks the risks identified in the inventory based on well
type and site geology, and existing and future risk of
contamination. A good management plan includes steps a system can
take to eliminate or reduce existing threats and a long-term plan
for protection of the groundwater well.
Very few public water sources have high levels of protection in
place. Public water systems are not in control of land use
activities in the surrounding communities. Most do not own the
entire recharge area for their source, and local governments have
been reluctant to adopt protective zoning or other ordinances to
reduce the risk of development in these areas. The Source
Water Assessments have identified future growth in source protection
areas as the dominant risk factor threatening public water supplies.
Controlling growth through land purchase, easement, or ordinance
is the greatest challenge facing water systems, towns, and the
Drinking Water Program.
Limiting the potential contaminant sources listed in Table 2 is the
most effective source water protection strategy. A management plan
that includes land acquisition, easements, local ordinances and
zoning, and enforcement of existing land use regulations will reduce
the threat of contamination and water quality degradation. Best
management practices (BMPs) may also be included in a management
plan, especially in areas with agricultural land uses.
The Drinking Water Program advocates that public water suppliers
utilize the following management techniques:
- Information and education;
- Land use regulations; and
- Capital improvements, especially land purchase and easement.
1. Information and Education Tools
- Post signs identifying the source protection area boundary
along roadways and at stream crossings.
- Notify local, state, federal officials of the source
protection area location. Post a map in town office buildings.
- Educate the public through the local media (press releases,
public service announcements, newspaper articles). Provide
information on BMPs for land-use activities, water conservation,
and actions citizens can take to reduce threats to water quality.
Household hazardous waste collection programs will reduce threats
to water quality and educate citizens.
- If the municipality has a Comprehensive Plan, work with
citizens and government officials to include source water
protection measures.
2. Working with existing regulations
- Work with local officials to develop a municipal source water
protection ordinance to define the land use activities that can
occur within the source protection area and the associated
performance and design standards.
- The Drinking Water Program has authority to require additional
water quality monitoring where threatening activities are located
within the source protection area (e.g., landfills and industrial
facilities).
- Special provisions can be attached to local, state, and
federal building and siting permits issued for activities within
the source protection area.
- Target the source protection area for local and state
environmental inspection and enforcement.
- Notify local officials of Public Law 761, which requires that
a public water supplier be notified of public hearings on proposed
commercial and residential development in the source protection
area.
- Enforce existing ordinances that have provisions for
groundwater protection.
3. Capital Improvements
- Negotiate land-use control easements or land acquisition
within the source water protection area.
- Install or extend public sewer.
- Secure or remove potential contaminant sources (e.g., manure
piles, junk yards, underground storage tanks).
- Secure back-up supplies.
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Table 2.
Land uses that are potential sources of groundwater contaminants |
| Above/Underground chemical or fuel storage
tanks |
Transportation corridors (highways and
railroads) |
Automobile service stations and autobody shops |
| Chemical drum storage areas |
Floor drains in repair garages & industrial
facilities |
De-icing salt storage piles and loading areas |
| Stormwater runoff, catchbasins and drains |
Land application/storage of sludge & manure |
Laundry & dry-cleaning facilities |
| Manufacturing facilities |
Open dumps and landfills |
Petroleum pipelines |
| Septic systems and sewer systems |
Construction projects |
Fertilizer application |
| Junkyards |
Laboratories |
Metal-plating facilities |
| Pesticide application and storage |
Printing and publishing facilities |
Airports |
| Fueling operations |
Graveyards |
Military Facilities |
ROLES OF PUBLIC WATER SUPPLIERS,
GOVERNMENTS, and ORGANIZATIONS
The public water supplier has the primary responsibility for
protecting drinking water sources from contamination. This
responsibility applies whether the public water supplier is a
corporation, municipality, or water district. But protection areas
and assessments are merely a tool for further management efforts,
and must be locally driven to be successful. Federal and state
agencies, municipalities, and the public have supporting roles in
land acquisition and development of land use ordinances.
Public Water Supplier
- Monitor and update the inventory of potential contaminant
sources.
- Review the Source Water Assessment Program report and develop
a management plan.
- Communicate with the Drinking Water Program, local officials,
and customers.
- Actively seek opportunities to improve land use management and
control in the source protection area.
Drinking Water Program
- Work with the water suppliers to select and develop
appropriate management options.
- When water supply testing results exceed drinking water
standards, work with the water supplier to develop and implement
corrective actions.
- Review and approve the wellhead protection management and
contingency plans that water suppliers submit.
- Coordinate the efforts of the Source Water Protection Program
with other state agencies, Indian tribes, and Canadian provinces.
Department of Environmental Protection
- Permit and license certain development and land use
activities; proposed activities within the source protection area
must comply with rigorous groundwater protection provisions and
performance standards.
- Regulate use, storage, and disposal of petroleum and hazardous
chemicals, provide emergency response for chemical and petroleum
spills, and coordinate spill cleanup and groundwater remediation;
enforcement and response activities within the source protection
area are given priority.
- Coordinate wellhead and source protection with other watershed
protection, habitat restoration, and water quality efforts.
State Planning Office
- Train and certify municipal code enforcement officers.
- Assist towns with comprehensive planning.
- Provide expertise on development and implementation of
management options.
- Coordinate wellhead and source protection with other land
conservation programs.
Department of Agriculture, Food, and Rural Resources
- Coordinate agricultural land conservation programs, such as
the federal Conservation Reserve Program and Wetlands Reserve
Program.
- Regulate pesticides application through the Board of
Pesticides Control.
- Develop BMPs for activities that have potential to degrade
water quality (e.g., pesticide and fertilizer application, manure
spreading and storage) and work with farmers to develop solutions
and implement BMPs.
- Work with the county Soil and Water Conservation Districts to
implement nutrient and pesticides management plans in priority
watersheds.
Department of Transportation
- Cover or move state-owned sand-salt storage piles that are
located within the source protection area.
- Provide funds to municipalities to help construct sand-salt
storage buildings.
- Reduce or prohibit pesticide and herbicide application.
- Retrofit DOT maintenance facilities to comply with groundwater
protection standards and practices.
- Require strict application of groundwater protection BMPs for
highway construction projects and maintenance activities.
- Provide notification signs for state roads that cross source
water protection area boundaries.
Maine Geological Survey
- Distribute maps and information on surficial and bedrock
geology and sand & gravel aquifers.
- Provide hydrogeological expertise to state agencies and public
water suppliers.
Municipal Governments
- Code enforcement officers pay special attention to
construction activities in the source protection area.
- Planning boards give special consideration to groundwater
protection issues during their deliberations on development
applications and zoning.
- Planning boards notify public water suppliers of development
proposals for land in the source protection area.
U.S. Environmental Protection Agency
- Administer the Safe Drinking Water Act and other laws that
affect groundwater and wellhead protection.
- Fund state programs that support the Drinking Water Program,
and regulations that control potential groundwater contaminants.
The Public
Development and implementation of a successful source water
protection plan is part technical, part educational, and part
political. However, success may ultimately depend on the
effectiveness of the educational component and how well the water
customers, the affected municipality, and landowners understand
basic groundwater concepts and the importance of restricting
potential contaminant sources. Understanding and addressing the
public's concerns early will help gain acceptance of a program and
participation in groundwater protection.
Wellhead Protection Grant Program
Community and non-profit non-community public water systems are
eligible for funding to plan or implement groundwater protection
projects. Possible projects include developing or implementing a
wellhead protection plan, developing public educational materials,
or developing useful base maps.
PUBLIC WATER SYSTEMS
The Wellhead Protection and Source Water Protection Programs
apply to public water systems: systems that provide water to at
least 15 service connections or 25 people daily for at least 60
days a year. There are two main types of public water systems,
each regulated based on the type of population it serves.
- Community water systems provide
water to 25 or more people or 15 or more service connections
with a residential population on a year-round basis.
- Non-community water systems provide
water to a non-residential population of workers, students, or
customers. There are two types of non-community systems:
a) Non-transient non-community systems, like schools and
factories, regularly serve the same population at least four
hours a day, four or more days a week, six or more months a
year;
b) Transient non-community systems serve water to different
individuals, and serve at least 25 persons daily for more than
30 days a year (e.g., a restaurant).
Each type of public water system has
different protection needs related to the volume of water pumped
and the number of people at risk if the source becomes
contaminated. Each system falls into one of four Wellhead
Protection categories with different degrees of protection and
program development effort depending on the size of the water
system.
- Category I is the least protective
and applies to non-community transient systems.
- Category II applies to non-community
non-transient systems serving water to employees or students
during working hours and small community systems serving less
than 250 people and or pumping less than 14,500 gallons per
day.
- Category III applies to community
and non-transient non-community systems serving between 250
and 1,200 people or pumping between 14,500 and 72,000 gallons
per day.
- Category IV applies to large
community systems serving more than 1,200 people and pumping
more than 72,000 gallons per day.
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For more information contact:
Drinking Water Program, Source Protection Section
11 State House Station, 161 Capital Street, Augusta, ME 04333-0011
tel: 207/287-2070 • tty: 207/287-5550 • fax: 207/287-4172
http://www.medwp.com
For guidance on developing a source water protection plan, see the
publication
Source
Water Protection, available as a pdf document.
Original digest prepared by: Sherman Hasbrouck
Revisions by: Catherine Schmitt and Ruth Hallsworth
May 2004
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