is the liquid of life, and clean water is a critical component of
Vermont, we expect drinking water to be inexpensive, plentiful, and
safe. Maintaining high-quality water supplies depends on our ability
and commitment to protect sources of drinking water and to learn about
the health effects of drinking water contaminants.
learned more about the potential health effects of several contaminants
during the past year, particularly arsenic, which was in the news
due to a U.S. Environmental Protection Agency decision in early 2001
to step back from a proposed, strict arsenic standard of 10 parts
per billion (ppb) in drinking water. Like many other contaminants,
the potential health effects of arsenic can arise from acute (short-term)
or chronic (long-term) exposure. Although arsenic can exert toxic
effects after acute exposure, such effects from drinking water in
Vermont are unlikely. Arsenic levels in our states public water
sources are typically below those that would trigger acute health
the effects from acute exposure to high concentrations of arsenic
have been known for some time, the effects from chronic exposure to
low concentrations have not been understood as well. Scientific analyses
in recent years, however, revealed increased risks of skin lesions
and lung and bladder cancer from drinking water with arsenic concentrations
below the federal standard of 50 ppb, which has been in effect since
1942. Following further study and release of a report by the National
Academy of Sciences urging the lower standard, the EPA reversed itself
again in late October and announced that it would reduce the maximum
arsenic level in drinking water to 10 ppb as of 2006 the same
standard proposed by Vermont in March.
occurs naturally in bedrock. Drinking water from bedrock wells (also
called drilled or artesian wells) and, less frequently, from dug wells
may contain arsenic. As groundwater slowly moves through the bedrock
fractures of an aquifer, erosion of the rock can contribute arsenic
to the water.
application of herbicides and pesticides, mining, wood treatment,
and several other human activities can contaminate water with arsenic.
Predicting whether a well has elevated arsenic is generally not possible.
Even at high concentrations, arsenic has no smell, taste, or coloration
when dissolved in water. Only water quality testing can determine
the presence and concentration of arsenic in well water. Public community
and non-transient non-community water systems (see box below ) test
for a suite of inorganic chemicals, which includes arsenic, at least
once every three years. Private well owners and homeowners can have
their water tested for arsenic, as well as other contaminants, at
the Vermont Health Department Laboratory or at private laboratories
certified for drinking water analysis. (The Agency recommends that
all private well owners get their well water tested at least once.)
Community Water System: A public water system that serves
at least 15 service connections used by year-round residents
or regularly serves at least 25 year-round residents.
Non-Transient Non-Community Water System: A public water
system that regularly serves at least 25 of the same individuals
more than 6 months per year, such as schools and businesses.
Transient Non-Community Water Systems: A public water system
that serves 25 or more people more than 60 days per year, such
as restaurants and campgrounds.
risk levels for chronic exposure to contaminants such as arsenic are
based on the assumption that an individual drinks two liters of water
a day for 70 years. Many people have difficulty identifying with such
long time spans. Instead, events with more immediate consequences
tend to attract our attention. One such event occurred in Canada in
May 2000. In Walkerton, Ontario, bacterial contamination was responsible
for the death of 7 people and hospitalization of 900 others. Inadequate
disinfection of water from a poorly constructed well during heavy
spring rains caused the tragedy.
water systems in Vermont rely on several mechanisms to help prevent
such tragic events: conducting routine tests for coliform bacteria,
assessing the systems susceptibility to viral and bacterial
contamination, disinfecting the system, and providing public notification.
of potential drinking water contamination is an important mechanism
to help protect human health. Fortunately for Vermonters who rely
on public water systems, information is readily available. Public
community systems distribute to their customers annual consumer confidence
reports that list the highest detected level for each contaminant
that has a water quality standard.
water systems must provide more immediate notices for situations that
pose a health risk. If a contaminant with the potential to damage
human health exceeds its standard, public water systems must notify
their customers. For situations with potential acute health repercussions,
systems must notify their customers within 24 hours.
water withdrawals in Vermont, including drinking water, are estimated
at some 45 million gallons per day. This demand is met by both groundwater
and surface water withdrawals from public and individual water systems.
this demand is not always easy. The summer of 2001 produced little
rainfall, with precipitation nine inches below average in some places.
Correspondingly, surface water and groundwater levels were also below
normal. As a result, 25 public community water systems reported water
shortages during 2001, and possibly another 10 systems experienced
the City of Montpelier, concerns regarding the communitys water
system were bittersweet in 2001. With the completion of Montpeliers
water filtration plant in 2000, all 32 Vermont municipal water systems
that draw from surface waters were in compliance with the federal
Safe Drinking Water Acts filtration requirements. For the operators
of the Montpelier system, however, water quantity rather than quality
became their major issue in 2001. Water levels in the citys
sole water source, Berlin Pond, fell three feet during the dry summer
months, prompting local officials to call for water conservation across
shortages at Vermonts public water systems were well managed
in large part because of the 1,100 individuals who operate these systems.
Certified water system operators responded to the challenge by measuring
and assessing water use, encouraging water conservation, identifying
and fixing leaks, and in some cases by hauling water. Their commitment
to providing safe, plentiful drinking water was reflected by their
desire stay current with the latest technical knowledge; approximately
half of the states operators attended educational opportunities
in the past year.
many individual water sources serving single families simply ran out
of water. Springs and dug wells, dependent on
shallow recharge, were among the first water sources to lose their
water due to the dry weather. Drilled wells, on the other hand, rely
on greater quantities of water held in aquifer storage, and these
sources respond more slowly to droughts. Since 1966, about 85,000
drilled wells (Figure 1) have been reported to the state. An additional
2,000 to 3,000 new wells are reported each year.
wells serve most public and private water systems in Vermont. Of all
drilled wells, an estimated 20 percent are sand and gravel wells,
and the remaining 80 percent are bedrock wells. Together, these groundwater
sources provide drinking water to about 64 percent of the states
bedrock wells must encounter water-bearing fractures to yield a given
amount of water. Fractures are simply cracks or fissures in the rock
that provide pore spaces or voids to store and transmit water. In
Vermont, yields can range from zero to more than 100 gallons per minute.
that provide water can also transmit liquid waste. Wells as much as
a mile away from a hazardous waste site can become contaminated. Fracture
zones can also connect multiple wells. Interconnected fractures between
wells may cause water outages from one well due to the pumping of
another. Practical considerations, such as distance from nearby leach
fields, property boundaries, and driveways, are factors that should
determine a wells location.