Water is the liquid of life, and clean water is a critical component of good health.

In 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.

Americans 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 state’s public water sources are typically below those that would trigger acute health effects.

While 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.

Arsenic 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.

The 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.)

Acceptable 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.

Public water systems in Vermont rely on several mechanisms to help prevent such tragic events: conducting routine tests for coliform bacteria, assessing the system’s susceptibility to viral and bacterial contamination, disinfecting the system, and providing public notification.

Awareness 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.

Public 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.

Domestic 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.

Meeting 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 brief shortages.

For the City of Montpelier, concerns regarding the community’s water system were bittersweet in 2001. With the completion of Montpelier’s 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 Act’s 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 city’s sole water source, Berlin Pond, fell three feet during the dry summer months, prompting local officials to call for water conservation across the city.

Water shortages at Vermont’s 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 state’s operators attended educational opportunities in the past year.

Meanwhile, 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.

Bedrock 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 state’s population.

Useful 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.

Fractures 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 well’s location.