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About 40 percent of Maine Residents
rely on their own sources of drinking water, such as wells, cisterns, and springs.
Although people have been using wells since ancient times, most are not familiar
with how they work.
A water well is a hole, usually vertical, drilled into an aquifer to bring water
in the ground to the surface from the water-saturated zone above the bedrock.
Ground Water - The Source
Ground water accounts for 90% of all the fresh water in the world (excluding polar
ice caps).
Ground water is the water that soaks into the soil from rain or other precipitation
and moves downward to fill cracks and other openings in beds of rocks and sand.
An aquifer is a geologic unit (sand and gravel, sandstone, limestone, or other rock)
where the amount of water is sufficient to yield usable amounts to a well or spring.
Those living outside a municipality or in an area not served by public water, will
typically get their water from a private well. Water wells are usually installed
by professional well-drillers, with the plumbing handled by a plumbing contractor.
There are two basic types of wells - shallow
and deep.
Shallow
Wells:
A shallow well is used when the water table (top surface of the ground water) is
high - anywhere from 10 feet to 100 feet below the surface.
Shallow wells are less expensive to dig, but rapid or large changes in water levels
can be expected during periods of heavy rains. The well may go dry during a drought
when the ground water table drops. They are also more likely to be contaminated
from surface contaminants.
There are three types of shallow wells - dug,
driven, and
bored.
Dug Wells
A "dug well" is the oldest type of water well. A hole is dug in the ground using
a shovel or backhoe until incoming water exceeds the digger's bailing rate.
Typically dug wells are found next to older homes, dug before drilling equipment
was readily available or when drilling was considered too expensive.
Most hand-dug wells are from 3 to 6 feet in diameter (large enough for a person
to work in), and shallow, usually 10 to 30 feet deep.
Brick tile, stones or other material are used to line the well, to prevent collapse
while allowing water to enter. Then the hole is covered with a cap of wood, stone,
or concrete.
If you have a dug well on your property and are using it for drinking water, check
to make sure it is properly covered and sealed.
Being so shallow, dug wells have the highest risk of becoming contaminated.
To minimize the likelihood of contamination, a dug well should have features to
prevent contaminants from traveling along the outside of the casing or through the
casing and into the well.
- The well should be cased (lined) with a watertight material
(for example, tongue-and-groove precast concrete) and a cement grout or bentonite
clay sealant poured along the outside of the casing to the top of the well.
- The well should be covered by a concrete curband cap that stands about a foot above
the ground.
- The land surface around the well should be mounded so that surface water runs away
from the well and is not allowed to pond around the outside of the wellhead.
- Ideally, the pump for your well should be inside your home or in a separate pump
house, rather than in a pit next to the well.
Driven Wells
Like dug wells, driven wells pull water from the water-saturated zone above the
bedrock.
Driven wells are generally deeper than dug wells - 30 to 50 feet deep, where the
ground water table is within 15 feet of the ground's surface.
In the proper geologic setting (areas with thick sand and gravel deposits), driven
wells can be easy and relatively inexpensive to install.
Lengths of metal pipes of 2" -3" in diameter are assembled and driven
into the ground.
A screened "well point" located at the end of the pipe helps drive the
pipe through the sand and gravel. This screen allows water to enter the well and
filters out sediment.
The pump for the well can be located in one of two places - on top of the well or
in the house.
An access pit is usually dug around the well down to the frost line. A water discharge
pipe to the house is joined to the well pipe with a fitting.
The well and pit are capped with the same kind of large-diameter concrete tile used
for a dug well. The access pit may be cased with pre-cast concrete.
Although deeper than dug wells, driven wells are still relatively shallow and have
a moderate-to-high risk of contamination from nearby land activities.
To minimize this risk, the following steps should be taken:
- The well cover should be a tight-fitting concrete curb and cap with no cracks and
should sit about a foot above the ground
- Slope the ground away from the well so that surface water will not pond around the
well
- If there's a pit above the well, either to hold the pump or to access the fitting,
you may also be able to pour a grout sealant along the outside of the well pipe.
- Protecting the water quality requires that you maintain proper well construction
and monitor your activities around the well.
Bored
Wells
Bored wells are the modern equivalent of hand dug wells. These wells are dug using
an auger, scoop, dragline, or some similar machine, and are relatively large in
diameter (2 to 4 feet).
Bored wells are typically constructed where aquifers (water bearing geologic formations)
are both shallow and low-yielding, 20 to 100 feet deep.
To compensate for these low-yielding aquifers, large diameter bored wells serve
as storage reservoirs to provide water during periods of high demand.
Older bored wells are commonly lined with sections of clay pipe; newer bored wells
are usually lined with concrete pipe.
If properly constructed and covered, they can provide a satisfactory water supply
and present no special hazard. Abandoned, they are as dangerous as dug wells and
cisterns, and should be plugged.
Deep (Drilled)
Wells
Drilled wells are deep wells - penetrating 100-400 feet into the bedrock. To serve
as a water supply, a drilled well must intersect bedrock fractures containing ground
water.
The casing is usually metal or plastic pipe, six inches in diameter that extends
into the bedrock to prevent shallow ground water from entering the well.
By law, the casing has to extend at least 18 feet into the ground, with at least
five feet extending into the bedrock. The casing should also extend a foot or two
above the ground's surface.
A sealant, such as cement grout or bentonite clay, should be poured along the outside
of the casing to the top of the well. The well is capped to prevent surface water
from entering the well.
Submersible pumps, located near the bottom of the well, are most commonly used in
drilled wells. Wells with a shallow water table may feature a jet pump located inside
the home. Pumps require special wiring and electrical service. Well pumps should
be installed and serviced by a qualified professional registered with your state.
Sanitary Features
Most modern drilled wells incorporate a pitless adapter designed to provide a sanitary
seal at the point where the discharge water line leaves the well to enter your home.
The device attaches directly to the casing below the frost line and provides a watertight
subsurface connection, protecting the well from frost and contamination.
Older drilled wells may lack some of these sanitary features. The well pipe used
was often 8-, 10- or 12- inches in diameter, and covered with a concrete well cap
either at or below the ground's surface. This outmoded type of construction does
not provide the same degree of protection from surface contamination. Also, older
wells may not have a pitless adapter to provide a seal at the point of discharge
from the well.
Almost all states license or register water-well installers. Most also have construction
standards for residential wells. In addition, some city and county health departments
have local rules and permitting.
While deep wells are less likely to be contaminated, routine testing of the water
supply is needed. Water testing and inspection of the well and equipment is the
responsibility of the well owner.
Abandoned Wells
An abandoned well is any water well that is no longer used to supply water, or is
in such a state of disrepair that the well has the potential for transmitting contaminants
into an aquifer or otherwise threatens the public health or safety.
Underground water is constantly moving. It flows through pores in the soil and through
cracks and crevices in the rock. As water moves, it picks up pollutants with which
it comes in contact.
Abandoned wells are a hazard to the water we all drink, even for those who use municipal
water.
If a well is left unsealed, the natural underground aquifer can become polluted.
If the shaft of the well is left open or the well casing cracks and deteriorates,
pollutants such as sewage, pesticides, fertilizers, organic or other hazardous materials
can seep into underground water making it harmful to drink.
Pollution is difficult to detect, difficult to control and may last for years. The
water for everyone in the surrounding area, whether from public or private wells,
can become contaminated.
Most states require that abandoned wells be properly sealed within 30 days of connection
to a public water supply or notification from the health department. A permit is
generally required.
SEALING A WELL
Abandoned dug wells and cisterns can be plugged by pushing in the upper few feet
of well lining, and filling the well to within two feet of the surface with chlorinated
clean fill such as course gravel or rock, varied-sized agricultural lime, or sand.
The remainder of the well should be filled with clay or clay-rich soil. Soil should
be mounded slightly at the top and compacted to help offset settling.
If a dug well is quite shallow, it can be pumped out and then destroyed with a bulldozer.
The average cost of sealing a well varies depending on well construction and location.
When the well is sealed, the driller must send an affidavit to the County Health
Department stating the work has been completed.
Another means of correction is to place the well back into service. If the municipality
you live in allows the continued use of the well it may be possible to continue
using it as a supplemental well.
Supplemental Wells
A supplemental well provides water for purposes other than drinking. Watering the
lawn or garden, filling a pond or a swimming pool, washing the car, are examples
of supplemental well use.
Supplemental wells, just like potable wells, are vertical pathways into this groundwater
supply. If the supplemental well is not properly maintained, it can act as a direct
channel for contaminating the aquifer.
Some areas have regulations that prohibit the use of supplemental wells.
If your city, municipality, or other public water provider does not object to the
use of supplemental wells, you may apply to the County Health Department to keep
the well.
The Health Department will inspect the well and well components, and collect a water
sample. The well must be of approved construction and must produce water that is
safe for human consumption.
CONVERTING TO A SUPPLEMENTAL WELL
Typically a supplemental well must provide approved backflow protection for the
well system.
Generally this means having hose bib vacuum breakers on outside faucets, a reduced
pressure zone backflow device for a buried sprinkler system, and/or an approved
fixed air gap for pond leveling wells.
As owner of the well, you must maintain the well in compliance with all state and
county well regulations. This includes completing and recording a Notice of Supplemental
Well form (where required) and allowing the Health Department access to the well
for inspection and sampling.
A Notice of Supplemental Well filed with the County Recorder of Deeds is required
in some areas. This is simply a notice that states that although your property is
served by a public water supply, there is also a water well on the property.
The Mechanicals (Pumps/ Pressure Tanks/
Filters/ Treatment)
Once the well has been drilled, the water in the well is available for use, but
it must be extracted from the well and delivered under pressure to the building.
This is accomplished by means of a well pump and a pressurized tank. The pump pressurizes
the system as it extracts the water from the well and conveys it to the tank. The
tank acts as a pressure regulator to the system by maintaining a constant outlet
pressure.
Well
Repairs, Buried Wells, and Wells in Pits
If repairs are needed to make the well operational or to bring it into compliance
with the Private Water Supply Ordinance, you may be required to obtain a repair
permit from the Health Department. The work must be completed within a specified
time, usually 30 days from when your well was inspected and the problem noted.
If you have a buried seal well or a well in a pit, it must be upgraded to meet the
provisions of the Private Water Supply Ordinance. This type of work requires a well
repair permit from the Health Department.
Provisions in the Private Water Supply Ordinance mandate that supplemental wells
must meet code requirements or be sealed. Water well sealing must be done by a state
licensed water well contractor, or may be done by the owner-occupant with prior
approval from the County Health Department.
Water
Well Problems
Many homeowners tend to forget the value of good maintenance until problems reach
crisis levels. That can be expensive. Maintain your well, find the problems early,
and correct them in order to protect your well's performance.
Keep up-to-date records of well installation and repairs plus pumping and water
tests. Such records can help spot changes and possible problems with your water
system. If you have problems, ask a local expert to check your well construction
and maintenance records. He or she can see if your system is okay or needs work.
The safety of any water supply is largely dependent on the construction and maintenance
of the water system. Below is a list of common well system problems that can spell
trouble if their symptoms are ignored:
Most Common Water Well Problems/Causes:
- Well Pump Turns On When Water Is In Use
Water System Leak
Check the inside plumbing for leaks.
If none are found, check outside for wet spots in the yard between the well and
the house.
Consult with a well contractor if you cannot determine the source of the leak.
- Well Pump Turns On And Off Continuously When Used
Pressure Tank Is Waterlogged
Draining and repressurizing the pressure tank may correct the problem. If you do
not know how to do this, you may need to contact a well contractor.
- Poor Water Pressure
Improper Pump Setting On The Pressure Switch
Most pressure switches are set to turn the well pump on at 30 p.s.i. (pounds per
square inch) and off at 50 p.s.i. Contact a well contractor to adjust the pressure
switch accordingly.
Water
quality
As ground water moves through the ground, it dissolves some of the minerals that
it comes in contact with. Those dissolved minerals give ground water its chemical
character or quality. Many bottled waters come from ground water reserves.
Ground water is naturally filtered by the earth that holds it. It can, however,
be contaminated by pollutants that come into contact with the earth's surface.
Proper well construction and continued maintenance are keys to the safety of your
water supply. Your state water-well contractor licensing agency, local health department,
or local water system professional can provide information on well construction.
WELL CONSTRUCTION
- The well should be located so rainwater flows away from it.
Rainwater can pick up harmful bacteria and chemicals on the land's surface. If this
water pools near your well, it can seep into it, potentially causing health problems.
- To keep your well safe, you must be sure possible sources of contamination are not
close by.
Experts suggest the following distances as a minimum for protection
- Septic Tanks, 50 feet
- Livestock yards, Silos, Septic Leach Fields, 50 feet
- Patroleum Tanks, Liquid-Tight Manure Storage and Fertilizer Storage and Handling,
100 feet
- Manure Stacks, 250 feet
NOTE: State and local regulations will vary. Contact your County
Health Department for compliance standards in your area.
- Water-well drillers and pump-well installers should be bonded and insured.
Make certain your ground water contractor is registered or licensed in your state,
if required. If your state does not have a licensing/registration program contact
the National Ground
Water Association.
- Protect your own well area.
Be careful about storage and disposal of household and lawn care chemicals and wastes.
Good farmers and gardeners minimize the use of fertilizers and pesticides. Take
steps to reduce erosion and prevent surface water runoff. Regularly check underground
storage tanks that hold home heating oil, diesel, or gasoline. Make sure your well
is protected from the wastes of livestock, pets, and wildlife.
Bacteria, Minerals Or Other Impurities
Underground water is constantly moving. It flows through pores in the soil and through
cracks and crevices in the rock. As water moves, it picks up pollutants with which
it comes in contact.
Protect your water supply by carefully managing activities near the water source.
For households using a domestic well, this includes keeping contaminants away from
sinkholes and the well itself. Keep hazardous chemicals out of septic systems.
Periodically inspect exposed parts of the well for problems such as:
- Cracked, corroded, or damaged well casing
- Check the electrical wiring to the well.
Ideally, the wires should be enclosed in metal conduit between the well and ground,
and between the basement wall and the pressure switch. If the electrical system
appears to be damaged, call a well contractor to repair it immediately.
- Broken or missing well cap
If the well casing extends above the ground, make sure the cap fits tightly onto
the casing and is in good condition. If the cap is loose, tighten it. If it is damaged,
replace it.
- Settling and cracking of surface seals.
- Slope the area around the well to drain surface runoff away from the well.
- Install a well cap or sanitary seal to prevent unauthorized use of, or entry into,
the well.
- Have the well tested once a year for coliform bacteria, nitrates, and other constituents
of concern.
- Keep accurate records of any well maintenance, such as disinfection or sediment
removal, that may require the use of chemicals in the well.
- Hire a certified well driller for any new well construction, modification, or abandonment
and closure.
- Avoid mixing or using pesticides, fertilizers, herbicides, degreasers, fuels, and
other pollutants near the well.
- Do not dispose of wastes in dry wells or in abandoned wells.
- Do not cut off the well casing below the land surface.
- Pump and inspect septic systems as often as recommended by your local health department.
- Never dispose of harsh chemicals, solvents, petroleum products, or pesticides in
a septic system or dry well.
Installing a water-conditioning unit can reduce water hardness and iron content.
Other water quality problems may sometimes be solved through disinfection of the
well water distribution system.
High mineral or iron content may require the need for a whole house water filter.
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