Groundwater Management and Wellhead Protection
Technical Assistance Series

Capital Coastal Council of Governments (CCCOG, February 1991)
(89 Western Ave., Augusta, Maine 04330)

This publication is presented for "Classroom Use Only."  Its intended use is to stimulate and aid in discussion and role playing within a classroom setting.

Groundwater is a community's lifeblood unless it uses a surface water supply. Most municipalities rely on individual wells but a few towns have water districts or water department. Towns or cities with major systems have particular management issues under a new federally-mandated state program, wellhead protection. The protection of all wells is important, no matter how small.

Analysis of groundwater is not just a task within the comprehensive plan or just a checkoff on a subdivision review. A town population that is dependent on individual wells for drinking water, does not want to get into a public water supply system unless it is forced by serious situations or emergencies.

Towns need to anticipate groundwater problems and manage growth so these problems don't happen. A town may see a time when a public water supply will be necessary. In this case the town will need to locate possible town well locations now before the critical well locations are otherwise developed.

Municipalities with public water supply systems that come from groundwater will soon be required to assist the water district or department in in-depth water resource studies and help implement special protection measures to assure that the well systems continue to have good water quality.

Groundwater Protection Issues

Why worry about groundwater management and wellhead protection? The reason lies in protecting groundwater quality and maintaining a good groundwater supply. There is an increased incidence of contamination from: petroleum products leaking into nearby groundwater; hazardous waste spills (or the increased knowledge of the seriousness of these occurrences); old landfill sites; salt storage areas; and, failed septic tank systems. These are the major reasons, but there are other minor situations that affect groundwater. The disposal of waste oil, pesticides, fertilizer, painting materials and cleaning fluids at home, businesses or on farms can also cause problems.

There have been problems with water supply when a coastal aquifer has so many wells pumping that wells begin to draw salt water. Other areas may have too many wells for the size or type of aquifer. Another problem arises where several small residential wells go dry when a major well system is located nearby. The same problem can occur if a gravel mine is mined too deep, which lowers the water level, or the water is contaminated with petroleum products spilled or leaking during mining operations.

Some of these spill situations and low water level occurrences may either go unnoticed or they may take a long time before their effects are known. With spills in a water system's wellfield, the spills may require that the system be shut down, as has happened in one of the Town of Lisbon's wellfields.

Another issue in more long-range planning is that towns that have and are experiencing a great deal of growth and are presently using individual wells may one day be required to have a public water supply. Towns should have contingencies for this possibility. Towns that have areas with failing septic tanks, predominance of poor soils or other areas where wells have been going dry may want to identify future wellfield possibilities.

There are usually discussions about groundwater protection during comprehensive planning meetings. Wellhead protection is another state mandate looming over the horizon.

Groundwater and Aquifers

Groundwater is simply the water beneath the surface of the ground. Groundwater is below the water table that raises or lowers according to local rainfall. Aquifers are permeable water-bearing geologic formations either above bedrock (surficial aquifer) or within the bedrock (bedrock aquifers). Surficial aquifers lie on top of the bedrock. Groundwater is recharged from rainwater and an aquifer's ability to recharge relates to the number of wells that the aquifer can sustain and still remain as a stable source of good water.

Depending on the type of aquifer, groundwater can flow to yet lower ground levels or may flow to outlets, such as a spring, river or to the ocean. Groundwater can be under pressure or confined, if an aquifer is covered by a less permeable geologic bed and water is recharging from a higher elevation. Wells drilled into these formations become artesian wells, when water under pressure rises to the surface without the aid of a pump.

Groundwater in Maine comes from either sand and/or gravel (surficial aquifer) or bedrock aquifers. The type and extent of the aquifers in a municipality depends on the underlying geology. Since Maine was shaped and formed by the actions of glaciers, aquifers can come in many shapes and sizes. Sand and gravel aquifers are formed where sand or gravel are deposited in river deltas, outwash deposits from glaciers or in many other variations. They generally have the higher yielding wells and good recharge potentials.

Bedrock aquifers are in the underlying bedrock and the water flows in the cracks and faults within the bedrock. Wells in bedrock depend on the well crossing a fault or enough faults to provide the necessary amounts of water needed (see figure below). These wells generally produce low yields and are also proving to be more susceptible to contamination.

Most people are aware of the 100-foot setback from septic tanks for potable (drinking) water wells. This setback protects a well from the major contaminants from septic tanks. There is also an increasing concern with nitrate leachate (liquid contaminants) from septic tanks. Nitrate in excessive amounts can cause illness or fatalities in infants. Nitrate runoff from septic tanks can still be at dangerous levels hundreds of feet (to over 1,000 feet) downgrade from a septic tank. This aspect of groundwater pollution will be the major concern in the future when siting septic tanks and designing subdivisions.

A well effects the groundwater level in such a way that it causes a "cone of depression" or "area of influence" (see figure below). The well actually causes this drawdown in the water level as it is operated. The bigger the well system, the larger the cone of depression. If there are multiple wells, the cones interact; and, if there are combinations of large and small wells, the smaller, more shallow wells can be left "high and dry." Groundwater is also affected by droughts and many of the situations mentioned above may not become apparent until a drought occurs.

Comprehensive Planning and Groundwater

The amount of time and energy that should be spent on groundwater issues in comprehensive planning is directly related to both a municipality's dependence on groundwater for drinking water and the availability and quality of the groundwater resources. Some municipalities have serious water quality issues or salt water intrusion and must spend a great deal of time and money to get the information they need for groundwater protection. Most towns can begin to develop a good basis in this comprehensive planning process and build on this with additional information over the next five or ten years.

Aquifers and recharge areas need to be mapped within each municipality. The state has mapped the major sand and gravel aquifers and some recharge areas. There are maps available through the Maine Geological Survey.

All petroleum storage facilities (both above and below ground) need to be mapped. The Department of Environmental Protection has this information (289-2651).

Towns should identify areas with well problems. Other areas that should be identified include areas of salt water intrusion, areas with contamination from salt piles, areas where wells have been known to go dry, and any minor or major water system wellfields.

Some of this information may come from area well drillers or local knowledge. There are also a limited number of state reports available for some areas. The extent of the public water system's wellfield and wellhead areas may be available from the water association, district or department, but detailed information may be difficult to find.

The location of sand and gravel aquifers and recharge areas is an important factor in future land use decisions, subdivisions and zoning districts. For example, a town would not want a radiator shop located in a major recharge area or within the wellhead protection zone.

The comprehensive plan should have guiding policies on groundwater protection, referenced to the municipality's maps and other specific information that would be required with development proposals (subdivisions, site plans). The municipality may want to consider an overlay zone over major aquifers or recharge areas with more stringent performance standards. Future wellhead protection may also require more specific performance standards.

If a town, in a coastal area, has experienced salt water intrusion or wells going dry, then more extensive groundwater studies may be planned within the implementation strategies. A town may want to set aside funds in the third or fourth year of the comprehensive plan for further analysis.

A wellhead is the area within the boundaries of the recharge area to a well. Wellhead protection involves planning and management requirements for public water systems serving 25 or more people, or 15 or more connections. These systems are divided between major and minor systems. A major public water system is one that serves 500 or more individuals and minor systems are those serving less than 500 individuals.

Wellhead protection is a federally mandated program that came out of the Safe Drinking Water Act of 1986. The Department of Human Services, State Planning Office and several other state agencies have been developing a state program to answer the federal mandates over the last several years. Program rules and regulations should be finalized in the next year. It appears that the Department of Human Services will be the lead state agency to deliver this program.

The way the wellhead protection program has developed to date, water districts, systems, etc. that fall under this regulation will have to undertake groundwater studies; identify wellhead protection zones for each well; develop management plans for protecting the wellhead; contingency plans for water supply disruptions; and, plans for dealing with possible contamination problems. Some of the requirements will be less stringent or not apply for minor water systems. Cost estimates for these studies for a major system may be as high as $50,000.

There will also be portions of the wellhead protection requirements directed toward municipalities. The municipalities will be required to cooperate with the public water system and state agencies involved in this program. The municipality will also be involved in the public participation phase of the program to inform the public on the planning and management requirements. Finally, the municipality will be involved in the regulatory implementation of ordinances to protect the wellhead zone and the groundwater resources on which the well depends.

It is important to know your municipality's groundwater resources, to anticipate problems before they become contaminated and to assure future generations of a good and safe groundwater supply. There should be more information on groundwater as the wellhead protection program proceeds and more management techniques as municipalities take more active roles in growth management. It is important for municipalities to understand their groundwater resources and design good planning and management practices to assure the protection of water quality. For more information contact the Capital Coastal Council of Governments at 622-7146.

Ground Water Handbook for the State of Maine, Bulletin 39, by W. Bradford Caswell, Department of Conservation, Maine Geological Survey, 1987.

"Wellhead Protection Groundwater Next On Feds 'Hit List,'" by Geoff Herman, MAINE TOWNSMAN, September 1990.

Maine Wellhead Protection Program (Draft), February 1990.

Groundwater Issues and Comprehensive Planning, The proceedings of a forum held at the University of Southern Maine, Portland, on June 29, 1990, Southern Maine Regional Planning Commission.

IlIustrations for this report are from the Groundwater Project, sponsored by the Massachusetts Audubon Society.

Technical Assistance Series

This is the sixth issue in this series of technical assistance articles for Council members, Selectmen, Planning Board and Board of Appeals members, Code Enforcement Officers and Comprehensive Planning Committee members that apply to problems and needs in municipal planning and management. Please be sure to share appropriate articles with fellow members and any others who may benefit from the information.