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

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

SAFE DRINKING WATER
What is the best source of water?
Where does the water come from?
How do I site a well?
How much water will I need?
Well installation checklist
What can go wrong
Water quality problems and solutions
Sources of information and assistance

ARE YOU…

• Planning to build a new home on a site that is not served by a community water supply?
• Replacing your existing water supply with a new well?
• Considering using a nearby spring, lake, or stream for your home's water supply?

Forty percent of Maine households obtain water from their own water supply. (This does not include seasonal homes or businesses.) Such private sources include water from drilled wells, dug wells, lakes, streams, and springs.

We are fortunate in Maine in having abundant clean water. However, all sources pose potential hazards. A safe, reliable water supply is important to the health of your family and the value of your home. This digest may help you to determine the best location for a new well and work with a well-driller to construct a new well. This digest also contains information on how to select water tests and interpret the results of a water test.

WHAT IS THE BEST SOURCE OF WATER?
Groundwater is the best source of drinking water for your home. Surface water sources (lakes, streams, and springs) are no longer considered suitable because they are vulnerable to contamination and may contain harmful bacteria or algae. Although it is possible to purify water taken from surface sources, it is a costly process to buy and maintain the necessary equipment. Dug wells, too, are easily contaminated and often have insufficient water during drought. In order to have a reliable source of safe water, the Maine Department of Human Services recommends that only drilled wells be considered for private water supplies.

WHERE DOES THE WATER COME FROM?
Several factors will influence the development of a new drinking water well. The local geology will affect how deep you will have to go to get a dependable supply and will determine the potential for future contamination. Knowledge about the geology and groundwater at your site will help you work with a well driller to construct a new well.
How do you learn more about the local geology? People knowledgeable about local geology may include neighbors, local builders, septic system site evaluators, well drillers, geologists, soil scientists, and town officials. Discussions with these people may help you determine:

• the nature of the overburden (underground layers of clay, sand, and/or gravel);
• overburden thickness;
• bedrock composition (for example: shale, schist, or granite); and
• bedrock quality (density of fractures and ability to hold water).

Well construction varies depending on the type of overburden. Unless you have a thick deposit of sand and gravel, most wells involve running steel casing through the overburden and sealing it to the bedrock. This is done to prevent surface contamination from getting into your water supply.

Sandy soil is porous and allows water to move through it easily. In some situations a good well can be constructed in thick sand and gravel deposits. Most of Maine is covered by till deposits. Till is a dense mixture of silt, sand, and cobbles left behind by glacial ice. Till does not allow water to move easily but forms a seal over the bedrock. Deposits of clay are found in some coastal areas and along major river valleys. Clay is very impermeable to water flow and can make water cloudy (turbid). In general, till and clay deposits do not make suitable water sources.

In bedrock, water is found in cracks and fractures. The more fractured the rock, the greater the potential for water. In a bedrock well, groundwater flows along the fractures into the well. In Maine, the bedrock is often most fractured within 500 feet of the surface. The number of fractures, the connections between fractures and to the surface, and the size of the fracture openings determine the amount of water that flows into the well. It can take many years for water to move from the land surface through fractures into a well; however, if the fractures are connected to a shallow water source, water can enter a well quickly. The amount of water flow depends upon the type of bedrock and the land-surface features that recharge the bedrock fractures.

HOW DO I SITE A NEW WELL?
Most homeowners do not have enough land or open space to provide many options for a new well location. However, there are a few siting regulations that must be followed. The general guidelines listed here will help you get the best results from your new well.

Protection of a well from possible contamination is largely a matter of good judgment. Maine requires a well to be located at least 100 feet from a septic system. (A smaller setback distance can be used if other control measures, such as deeper well casing, are used.) By law, a well driller must make every reasonable effort to determine the location of all septic system components on your property and any adjacent properties of concern.

In addition to this statewide regulation, you should check with your local Code Enforcement Officer for local well location rules.

Keep the following points in mind when selecting a new well location:

• Be sure you are within your property lines.
• Site the well in an area accessible for maintenance and repairs.
• Avoid siting the well in a flood-prone spot or in the bottom of a hollow to prevent surface water from flooding the well.
• Stay as far away as possible--and uphill--from potential sources of contamination, including septic systems.
• The well site must be accessible by a drill rig.

HOW MUCH WATER WILL I NEED?
The amount of water that can be removed from a well is called yield. Yield, measured in gallons per minute, is the combination of water recharge into the well and storage within the well itself. Many bedrock wells that recharge at less than one gallon per minute have enough water stored in the well itself to supply household needs.

A family of four typically uses about 300 gallons of water per day. Water use is not uniform throughout the day; use is higher in the morning and evening. Water stored in the well makes up for the difference between high demand and low recharge.

Well storage depends upon the diameter and depth of the well. A six-inch drilled well stores 1.5 gallons per foot of depth. A well with 250 feet of standing water, for example, can store 375 gallons of water exclusive of recharge. Even if water flows in at a fraction of a gallon per minute, there is enough water stored to supply the average household. This ability of deep wells to store large amounts of water is why recharge rates of deep wells do not need to be as great as those of shallower wells.

The State of Maine recommends a certain combination of well recharge rate and total depth to make sure that the well will have adequate yield. Table 1 should be considered a minimum guideline. Your needs may be different depending on water-use habits or family size, lawn or garden watering, and the depth to water.

Sometimes obtaining the best yield must be balanced against well installation costs. A well driller may complete a well to an agreed maximum depth, only to find the yield is too low. The homeowner must then either drill deeper or relocate. Some home-loan companies may require a certain well yield as a condition of lending.

In some areas of the state, low well yields are common and you may have to live with a low yielding well. A household could get by with yields below the recommended values if well costs rule out a new or deeper well. However, water use would need to be carefully monitored and controlled with water-conservation fixtures such as low-flow toilets and showerheads.

WELL INSTALLATION CHECKLIST

• Is the well driller licensed? Contracts with well drillers are required by law and well drillers must be licensed by the state. The well driller you select should describe the type of well to be installed, the expected depth of the well, how the well will be prepared for use, and how the well will be connected to your house.
• Is the driller responsible for guaranteeing a certain quantity of water? This needs to be determined from the well yield desired, the minimum acceptable yield, and the maximum depth to drill without getting sufficient water.
• Is the driller responsible for guaranteeing the quality of water used for drinking? It is the responsibility of the well driller to install a sufficient length of well casing into bedrock, and to affect a proper seal in order to prevent surface water and shallow ground water from transmitting gravel, sand, silt, clay, and bacteria into the casing. However, the driller has no control over the natural quality of the water, and cannot be held responsible for water quality that is not related to well construction.
• Have you been provided with cost estimates of
  • drilling and well casing material per foot;
  • well seal (such as grout and drive shoe) if the well extends into bedrock;
  • sanitary well seal at the top of the casing;
  • well screen (per foot) if the well does not extend into bedrock;
  • disinfecting/testing the well after completion;
  • ditching for piping and power between the well and the house; and
  • installing a pump in the well, plumbing the pump to the house, installing a pressure tank and connecting the well to interior plumbing.
• Does the agreement include the driller's right of access and do you accept necessary disruption to land and vegetation, including drilling and trenching debris?
• What minimum construction standards will be met with respect to:
  • well diameter (six inches is typical);
  • well angle (vertical is normal); and,
  • material and equipment to be used?
• Will the contractor provide future well maintenance?
• Is the contractor insured for liability and worker's compensation? Is the contractor free of liability for injuries not cause by contractor's negligence?

Drilling and Development
Once a location for the well has been chosen, a hole (typically six inches in diameter) is drilled through the soil overburden into bedrock until water bearing fractures are found. Drilling continues until the desired well yield is reached. A minimum of twenty feet of casing is required, and ten feet of casing into bedrock is recommended. The well is developed by blowing air or water into the well to remove fine rock particles. Finally, the well is disinfected after drilling and before water quality testing.

Disinfection
The disinfection procedure is routinely performed by qualified well drillers. A chlorine chemical disinfectant is mixed with the standing water in the well to provide a concentration of 50 parts per million and allowed to stand for at least four hours. Liquid chlorine is preferred since tablets do not always dissolve completely. The chlorine solution must be removed from the well before water quality samples are collected.

Testing
A water quality test must be performed before you start drinking water from your new well to insure that the well water is safe to drink and contains neither bacteria nor unsafe contaminants.

All new wells must be tested, and existing wells should be tested every one to five years. Where a new well is being drilled, the well driller will help you arrange for such testing. The Maine Health and Environmental Testing Laboratory has three designations for private well tests. The tests include:

Test B is the standard test for new wells. It is the minimum test required by home loan agencies. It covers coliform bacteria and other contaminants commonly encountered in Maine.

Test C is a more complete test for new wells. It includes testing for contaminants that may be a problem because of the location of the well or the physical condition of people in the household.

Test A is the test recommended for yearly rechecks after more complete testing. It includes testing for coliform bacteria and nitrate/nitrites.

A number of other tests may be performed if there are potential contaminants of special concern:

• contaminants from nearby industrial waste sites and landfills;
• iron, bacteria, and algae;
• organic chemical compounds, such as gasoline, kerosene, fuel oils, solvents, degreasers, and wood preservatives;
• pesticides and herbicides commonly used in forest, crop, and weed spraying; and
• radon

A list of certified private laboratories is available from the Division of Health Engineering. These labs are able to perform the standard water tests. In addition to the tests described above, the Maine Health and Environmental Testing Lab is able to carry out other specialized tests that may be beyond the capability of the private labs.

WHAT CAN GO WRONG

Well locations may be poorly planned within neighborhoods.
One homeowner putting in a new well and septic system may make it difficult for neighbors to meet spacing requirements when they put in wells or septic systems at a later time.

The well may be dry or have inadequate flow.
Sometimes a drilled well will intercept too few water-bearing structures, and the yield will be inadequate. Continued drilling may be justified, but it is sometimes necessary to drill a new well at a different location.

A dug well may go dry during drought periods.
The dug well should be replaced by a new drilled well.

Bacterial contamination can occur during the well construction process.
This could occur simply through handling equipment or through entry of contaminated surface water during construction. All new wells should be disinfected and tested after the pump is installed and before well water is used. The plumbing system and the well should be disinfected after installation and before occupancy.

An extended power outage may shut off the electrical pump.
The homeowner may own or borrow a temporary generator to keep the pump operating, however, the generator would need to be powerful enough to operate the submersible pump. (Most pumps being installed now operate at 220 volts.) A licensed electrician should make the installation.

The pipe connecting the outdoor well with indoor plumbing may freeze.
Where water lines have to be placed at shallow depths under paved areas or under bare, compacted soils, the pipes should be put within a pipe sleeve of larger diameter, surrounded on top and sides by slabs of polystyrene foam, and backfilled with sand or fine gravel.

The well may encounter saltwater.
Salt enters groundwater from two sources: intruding ocean water and road salt contamination. If you live on the coast or islands, rising sea levels can cause ocean water to enter fractured bedrock aquifers. Road salt application and salt piles can also contaminate groundwater. If you live inland and suspect road salt contamination of your well, call your town if you live on a town road, otherwise contact the Department of Transportation.

The water may have unsatisfactory quality.
The water test made at completion of the well may identify natural contaminants that usually can be remedied by various treatment methods. There are numerous conditions that can cause well water to have objectionable taste, odor, or appearances, or even be unsafe to drink. In Maine, water quality often is not satisfactory because of natural groundwater conditions that can lead to elevated arsenic, radon, and uranium levels. All wells should be tested for arsenic and radon because of concerns about its health effects. Other natural contaminants include iron and manganese, which may impart a metallic taste or rusty color, and salt, that can enter wells in coastal areas.

In some cases, the problem is temporary. Turbid (somewhat cloudy) water will often clear up within a few days following completion of a well. It is common, too, for water to be brown for a day or two following disinfection of the well with a chlorine solution.

The water may become contaminated as a result of human activities.
The sources of such contamination may include:

• a nearby septic system;
• a leaking underground gasoline or heating oil tank;
• heavily salted roads, a sand/salt storage pile, or site where there was such a site many years ago;
• agricultural chemicals or livestock wastes;
• an old dump, existing landfill, or industrial waste site;
• pesticides and fertilizers used on lawns and landscaping.

Because wells may become contaminated by these and other sources, well water should be tested every one to five years. If significant change is noticed (in taste, color, or odor), the water should be tested immediately. Do not drink the water until it has been tested.

WATER QUALITY PROBLEMS AND SOLUTIONS

SOURCES OF INFORMATION AND ASSISTANCE
The State of Maine requires that well drillers be licensed. A list of contractors is available from the Well Drillers Commission at the Division of Health Engineering. In addition, many well drillers belong to the Maine Ground-water Association, an independent professional association. The Division of Health Engineering can tell you who to contact for a list of members of that association.

Names of local well drillers can be found in the yellow pages (under well contractors or water well drillers) and by inquiries to friends, neighbors, and town officials. A competent well driller can be a partner in helping you select the best well location.

For more information:
Drinking Water Program
161 Capitol Street, 11 State House Station, Augusta, ME 04333-0011
tel/tty: 207/287-2070 • fax: 207/287-4172
http://www.medwp.com

Maine Health & Environmental Testing Laboratory
221 State Street, 12 State House Station, Augusta, ME 04333
tel: 1-866-292-3474 (in Maine) • tel: 207/287-2727 • fax: 207/287-6832

Maine Groundwater Association
c/o Patricia Pratt
280 Litchfield Rd, Bowdoin, ME 04287

For information on road salt, petroleum and other hazardous chemical contaminants, contact:
Department of Environmental Protection
207/287-3901

University of Maine Cooperative Extension also has resources and information on drinking water wells:
207/581-3241 • www.umext.maine.edu.

Original prepared by: Sherman Hasbrouck and John Peckenham
Revisions by: Catherine Schmitt and Ruth Hallsworth
May 2004