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How
To Keep Your Water ‘Well’
Just
as above the earth, small drops form and these join others, till finally
water descends in a body as rain, so too we must suppose that in the earth
the water at first trickles together little by little and that the sources
of rivers drip, as it were, out of the earth, and then unite.—Meteorologica,
Aristotle (384–322 B.C.)
Since
the beginning of time, the search for water has guided the formation of
kingdoms. History tells us its presence both sparked development and spurred
devastation.
People searched for water, fought for water, and even died for it. It
is nourishment—without it, life cannot exist.Yet today, most of us
take it for granted—the clear, thirst-quenching liquid that flows
effortlessly from our kitchen and bathroom fixtures. We turn the faucet
on, and there seems to be no end to this precious resource.
With such convenience, it is not surprising that the U.S. uses more water
than any other country. The average individual uses 40 to 50 gallons of
drinking water per day. Although it is labeled “drinking water,”
only a small portion is actually used for drinking. The majority is used
for other purposes, such as toilet flushing, bathing, cooking, cleaning,
and lawn watering.
The quality of our water reflects our general quality of life as a society.
Whether we retrieve our water from a public treatment system or private
well, all of the water we use comes from either surface water or groundwater.
Surface water sources include rivers, lakes, and reservoirs while most
groundwater comes from rain and melting snow, which soaks through the
ground getting trapped in spaces between rocks and soils. These underground
water formations, called aquifers, may be only a few miles wide or may
encompass the areas of many states.
The majority of private drinking water supplies draw groundwater from
wells, but some households obtain water from streams and cisterns (rain
water collected from rooftops). In addition to individual home wells,
there are also community wells that serve entire towns.
Large-scale water supply systems, found mostly in populated areas, are
likely to rely on surface water sources, while small water systems, found
in rural populations, tend to use groundwater as their source.
According to the U.S. Environmental Protection Agency (EPA), more than
half of the U.S. population (53 percent or 151 million people) receives
its drinking water from groundwater sources with approximately 8 percent
or 23 million Americans retrieving their drinking water from private wells.
Keeping wells free from contaminants requires careful planning, especially
when an onsite system is in use nearby.
According to 1990 census data, nearly one out of every four homes in the
U.S. relies on some form of onsite system to treat and dispose of their
household wastewater.
Because septic tank effluent contains bacteria, viruses, and high levels
of nitrates from human waste, contamination is a major concern in the
incidences of waterborne pathogens in
private wells in the U.S.
It is estimated that septic tanks may have contaminated 1 to 2 percent
of the nation’s usable aquifers. With 800 billion gallons of water
per year being discharged to the subsurface in the U.S. via septic systems,
contamination of wells is an important problem to address.
Groundwater Quality
By
nature, all water contains some impurities. Contrary to what you may read
on bottled water labels, there is no such thing as naturally pure water.
As water flows through rivers and streams and filters through soil and
rock, it absorbs many of the substances it touches. The water quality
in an aquifer depends on the nature of the rock, sand, or soil in the
aquifer and what contaminants are in the area.
The dissolved minerals and gases and the amount of suspended matter determines
water quality. Some contaminants are harmless, but some compounds may
make the water unpalatable and even unsafe.
One basic measurement of water quality is the total dissolved solids (TDS),
a reflection of the total amount of solids remaining when a water sample
is evaporated.
Water is made up of major constituents, such as chloride, sulfate, carbonate,
and bicarbonate, and minor constituents, like iron, manganese, fluoride,
nitrate, strontium, and boron. In addition, trace elements, such as arsenic,
lead, cadmium, and chromium may be present. The trace elements are extremely
important in determining water quality.
Prior to 1974 each state had its own drinking water program, setting the
standards that had to be met. Standards were minimal at best. Since 1974,
when Congress passed the original Safe Drinking Water Act, EPA has set
uniform nationwide minimum standards for
drinking water.
A process called risk assessment is used to set quality standards. EPA
has issued more than 80 maximum contaminant levels (MCLs) for safe drinking
water standards.
A Deep Subject
Private wells are not a new technology. People have been digging wells
for centuries—long before modern technology was there to help. Primitive
people would simply hand dig a hole deep enough to reach the water table.
When the water filled the bottom of the hole, they would lower a bucket
on a rope down to haul the water out.
Dug wells, which rarely exist today, are prohibited by many states because
they are very susceptible to contamination from surface runoff.
Today most well drilling companies use large, truck-mounted rotary drills
or auger bits. Wells may range up to 1,000 feet deep. There are three
common types of wells—bored, driven, and drilled.
Bored wells are constructed with an auger. After the water table is reached,
the hole typically is lined with steel pipe. The lower part of the well
is provided with a screen to keep sand and other material from entering
the water. Like dug wells, bored wells are subject to contamination unless
the casing is sealed with grout and the well is at least 15 feet below
ground surface.
Driven wells are made with a series of pipes fitted with a well point
on the end. The well point is forced through the ground by a series of
blows on the pipe or by using water pressure, especially in sandy soils.
When the point reaches the water table, water flows into the pipe through
screened openings on the well point. Driven wells are useful when the
water table is no deeper than 50 to 60 feet.
Drilled wells, the most common today, are used when the water table is
at a greater depth, volume, or diameter or when the ground is too hard
to use a well point. Drilled holes are lined with steel or plastic well
casing.
Many experts recommend that the well casing extend to a depth greater
than 25 feet or 10 feet below the static water level in sand and gravel
formations.
Location, Location…
Placement of wells in relation to septic tank systems is an imperative
factor in preventing contamination. Setback standards for wells and septic
tank systems vary widely from state to state, most ranging from 50 to
100 feet. (Contact your local health department for your particular setback
regulations.)
Those setback distances may increase should limiting factors exist, such
as the presence of limestone, karst, or fractured bedrock in the soil
formation.
Table
1 presents the minimum horizontal separations required
by the state of Washington from their onsite regulations.
Click herer for PDF version
of Table 1
Design and operating standards are meant to ensure that a septic system
does not malfunction. Most wastewater treatment experts recommend that
a septic tank be pumped out every three to five years, depending on the
size of the tank. Onsite owners also should inspect their system annually
to make sure it is operating properly.
The minimum lot size per typical household septic system varies from 0.5
to 5 acres, depending on the state or municipality.
Still, contamination may occur when inadequately treated effluent rapidly
infiltrates the unsaturated or vadose zone and reaches the water table.
The likelihood of septic tank contamination seems to be higher in areas
where there is a high density of homes with septic tanks, the soil layer
over permeable bedrock is thin or extremely permeable, and the water table
is within a few feet of the land surface.
Having a well that is more than 10 years old or less than 50 feet deep
increases the chance for contamination. In order for a septic system to
function properly, it must be properly sited, designed, installed, and
maintained.
But even if the septic system is functioning properly and within proper
setback limits, another factor to be considered is the placement of septic
leachfields.
Since leachfields are generally located in areas where wastewater percolates
through soil as part of the treatment process, placing leachfields close
to a drinking water source can cause problems.
If your well tests positive for indicator organisms (e.g total coliforms
or fecal coliforms), or chemical contaminants, but there are no septic
systems nearby, public sewage treatment lines may be to blame. Leakage
from sewer lines, which carry untreated raw sewage and may contain industrial
waste, can introduce chlorides, microorganisms, organics, trace metals,
and other chemicals.
Identification of Contaminants
In addition to failing or improperly sited septic tanks, a variety of
human activities impact water quality. Pollution sources can range from
industry, landfills, pesticides, fertilizers, livestock wastes, storm
water runoff from agricultural and urban sources, and household wastes.
The EPA recommends that private water wells be tested annually for indicator
organisms and nitrate to detect contamination problems. Indicator organisms
are not harmful in themselves, but their presence indicates that other
pathogenic organisms, such as E coli, Giardia, Cryptosporidium, or hepatitis,
could have survived
The water also should be tested for other potentially dangerous contaminants,
such as pesticides and radon.
In addition to the above annual tests, many water experts recommend a
broad range of water tests should be done every 5 to 10 years.
Homeowners can access a list of certified laboratories from their state
or local health department. Some health departments will conduct the tests
for free. The average cost of a private laboratory test for nitrate and
bacteria samples will typically range between $10 to $20.
Contamination Happens
According to the EPA, in 1993 and 1994 there were 30 reported disease
outbreaks associated with drinking water, 23 associated with public drinking
water supplies, and seven with private wells.
(See Contamination
Factors)
Although no definite statistics are available to document the potential
contamination threat onsite systems may pose to drinking water, several
cases of infectious disease outbreaks have been documented.
In Polk County, Arkansas, a 1971 outbreak of viral hepatitis was traced
to a well that was contaminated by seepage from a septic tank located
95 feet away. In 1972, Yakima, Washington, experienced a typhoid outbreak
that was attributed to well water from driven well points. Septic tank
wastewater from the home of a typhoid carrier was discharged into the
ground 21 feet away from the contaminated well. Similarly, a septic tank
located 50 feet above the spring supplying drinking water to a resort
camp in Colorado was found to be the cause of 400 cases of gastroenteritis.
Possible signs of contamination may include:
• water that tests positive for coliform,
• unexplained illnesses, such as gastrointestinal problems, hepatitis
A, or typhoid, and
• neighbors finding septic system contaminants in their water.
Septic system effluent containing nitrates can pose a health hazard to
infants, in particular. Nitrates have been shown to cause methemoglobinemia,
known as “Blue Baby Syndrome.” Many health officials recommend
testing well water in the vicinity of septic systems more frequently when
children or pregnant women are present.
Signs
that suggest you should test your well (Sidebar)
Education a Key Component
Homeowner education is a key component in coordinating the management
of private water supplies and wastewater treatment systems.
A study that was published in the1998 Journal of Soil and Water Conservation
illustrates the need for increased education programs. The study evaluated
the water quality habits and beliefs of the approximately three million
residents living in upstate New York who rely on groundwater to supply
their drinking water and the 1.5 million households there with onsite
wastewater treatment systems.
The study surveyed 244 homeowners in three counties. Drinking water was
tested, and water supplies and onsite systems were inspected. An average
of 32 percent of the drinking water tested positive for coliform. Nitrate
levels varied with only two samples having concentrations greater than
the current drinking water standard of 10 mg/L.
Despite these statistics, 82 percent of those questioned were satisfied
with their water supply although 31 percent of those satisfied had coliform
in their drinking water.
Routine maintenance was also listed in the study as a problem since nearly
half of the residents had not tested their drinking water and more than
one third had never pumped their septic system.
The study concluded that “a general lack of homeowner knowledge suggests
the need for increased educational programs targeted to the rural audience,
as well as additional research to better understand what influences homeowner
perceptions and management practices.”
What
the EPA reccomends (Sidebar)
The Final Word
Septic systems and drinking water wells can, and do, coexist harmoniously
if the proper precautions are taken. Ultimately, the responsibility is
left up to the homeowner.
David Pask, engineering scientist with the National Small Flows Clearinghouse
(NSFC), has some additional advice for homeowners who may find that their
well supply is contaminated by an existing or new septic system despite
compliance with codes.
He said it might be possible to eliminate the problem by installing additional
well casing to extend the depth of pumping to below any shallow septic
effluent.
If the well casing was sufficiently below the static water level, it would
be advisable to reduce the flow of the well pump by a throttling valve
or to install a pump of low capacity. However, a water storage tank may
be necessary to allow for sporadic high water demand under a constant
low pumping rate.
If all of the compliance regulations have been met and the homeowners’
water still persistently tests positive for coliform and other contaminants,
they may need to install filtration and disinfection device in the well
system for proper treatment.
Sidebar
Information
- The
risk of contamination depends on several factors, including:
- Signs
that suggest you should test your well include:
- The
EPA recommends thefollowing steps to protect groundwater supplies:
- Minimum
Horizontal Separations Table
For
more answers to your drinking water questions, feel free to contact the
National Drinking Water Clearinghouse (NDWC), our sister program.
The NDWC offers On Tap, a quarterly magazine; more than 250 free
products; a bibliographic database; and RESULTS (Registry of Equipment Suppliers of Treatment Technologies for Small Systems) data base. For
more information, call (800) 624-8301 or visit their Web site at www.ndwc.wvu.edu.
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