The Carlisle Mosquito Online

Friday, October 12, 2007


Carlisle private wells contain more than just water . . .

For more than 250 years the majority of Carlisle residents have used private wells to supply their drinking water. Many take the quality and quantity of their well water for granted, but according to the U.S. Environmental Protection Agency (EPA), no unprocessed water is pure.

The composition of water is such that many materials are easily dissolved upon contact. These dissolved materials are referred to as contaminants. Potential drinking water contaminants can be naturally occurring, such as iron and radon, or can be the result of some past or present human activity, such as bacteria from septic fields or organic chemicals from fertilizers, pesticides, oils, paints, solvents or gasoline.

Local variations

Although well and water filtration technologies have changed over the years and our understanding of hydrology has improved, the quality and quantity of well water remains very much a function of the local geology. Board of Health Chair (BOH) Jeff Brem notes that the glacial nature of this part of New England results in a wide variety of localized soil types and therefore a variety of mineral content in well water. "When you drill a well, you tap into a fissure in the bedrock," Brem explained. "Your neighbor may drill a well to the same depth and hit an entirely different fissure yielding water with different mineral content."

Brem added that some mineral patterns are evident, "Westford has a lot of arsenic and many Carlisle wells have hard water due to high iron content. That's why so many Carlisle households use water softeners." Like well water everywhere, Carlisle's water contains a variety of trace materials, or contaminants. According to BOH Agent Linda Fantasia, the most common naturally occurring contaminants in Carlisle wells include iron and manganese, with radon and arsenic found in a smaller number of wells. Other contaminants, such as sodium, chloride and MTBE (methyl-tertiary-butyl ether) have been found in some wells in the town center.

Public Water supplies

Carlisle does not have a municipal water supply. However there are wells that qualify as "public water supplies," defined by the state as systems which serve 25 or more users for more that 60 days per year. In Carlisle, this includes public buildings such as the school and churches. It will also include the new Coventry oods 40B subdivision. Public water supplies are subject to greater regulation and testing. Annual compliance reports are also required and a certified wll operator must be available to the site at all times

Iron and manganese

Not currently associated with elevated health risks, when found in well water these elements are seen more as a nuisance. Many Carlisle residents fight rusty orange stains in laundry and dishwashers, because, as Fantasia notes, iron and manganese are spread around town. Some wells have exceedingly high levels, requiring filtration systems for clear water, while wells in adjoining lots may show no iron or manganese at all.


Radon is a naturally occurring element often found in areas around granite outcroppings. Radon has been detected in a number of Carlisle residences, both in the gaseous form within the home, as well as dissolved in well water. According to Fantasia, the BOH is not alarmed by the existence of radon in Carlisle homes. "A new screening test, "gross alpha," can be used to detect a variety of radioactive compounds and there are remediation steps that can be taken."

Synthetic organics

Synthetic organic compounds include a variety of manufactured chemicals, many of which were used as pesticides. Testing for these can be more expensive. Fantasia suggests that homeowners investigate the history of the land on which the well has been drilled. If it was used as an orchard or farm, homeowners may wish to test their water for these substances.

Bacteria and nitrates

The presence of bacteria or nitrates in well water poses a more specific problem, as either could indicate that a septic system has contaminated the well. The Board of Health requires that bacterial contamination be reported and monitored.

Recent bacterial contamination of the water supply at Ferns Country Store is believed to have resulted from contamination of a sub-ground-level well head. The well has been treated with chlorine and subsequent testing indicated no bacterial contamination. A six-month follow-up test is due this fall.


According to the EPA, the presence of high levels of lead in drinking water is cause for action. Lead is a metal which can accumulate in the body and is associated with several health issues. Exposure to high levels of lead is particularly dangerous for children and pregnant women. Most often lead leaches into drinking water as a result of corrosion of plumbing materials. Lead pipes, lead-based solder and brass faucets are all possible sources of contamination, particularly in combination with low pH water. For this reason, water samples used to test for lead must be taken from the tap.


One "contaminant" not found in many area wells is fluoride, the substance added to municipal water systems to strengthen dental enamel in children. To compensate, many local pediatricians prescribe sodium fluoride tablets for Carlisle children.

Contaminants in town center

Many wells in the center of Carlisle have experienced high sodium levels in the past, when the Department of Public Works (DPW) stored uncovered salt piles on the site now occupied by the police station. The salt piles were moved, and are now stored in a covered shed behind the transfer station off Lowell Street. The DPW also switched to using potassium chloride in the center to treat icy roads instead of the standard sodium chloride road salt used elsewhere in town. In the years since these steps were taken, salt levels in the water have declined.

A small number of wells near the center have tested positive for MTBE which was used as a gasoline additive until a few years ago. Fantasia noted that currently six private wells are monitored by the BOH for MTBE contamination. All are in the center of town. Three of the wells show levels of MTBE above the state DEP standard of 70 ug/L.

In 1996, the DEP ordered removal of MTBE-contaminated soil from the site of the former gas station next to Ferns Country Store at the intersection of Bedford Road and Lowell Street. The clean-up process spanned several years, and in 2000 the DEP removed 1,500 cubic yards of soil. Monitoring wells were tested by the state for two years, and the state has required that the owners of the former gasoline station pay for filtration systems for each of the affected private wells. A few other wells near the center, mostly in the East Street direction indicate trace amounts of MTBE.

According to Fantasia, "MBTE levels in the wells that we are monitoring still fluctuate." The most recent test results from private and monitoring wells, received about six months ago, have shown decreased levels of MTBE.

Fantasia added, "During a board meeting after the most recent results came in, the BOH agreed that it would be best to test the monitoring wells twice per year during the same seasons each year. This would allow the board to track seasonal fluctuations in the results and to have more confidence in the trends. The question is, who would pay for the testing program? The board has asked town counsel, but has not gotten a firm answer." According to Fantasia, "The Board of Health would like to get a professional assessment and plan for the MTBE status."

In addition, benzene and toluene have been detected on the site of the former gas station, but according to Fantasia, they have not been detected anywhere else.

No routine testing mandated

The town works to protect its water resources in a variety of ways, including instituting and enforcing local water supply regulations, providing well and plumbing inspectors and educating the public via the BOH. However, while the BOH can offer advice, it cannot guarantee the safety of water used from private wells. It is the responsibility of the homeowner to ensure that their well water is safe for drinking.

Optional testing

The BOH does require water quality testing when a new well is created and when property is transferred. However, no routine testing is mandated. The BOH suggests that homeowners test their wells yearly for several contaminants, including bacteria and nitrates; and every three years for other contaminants which are less closely associated with health risks, including sulfates, chloride, iron and manganese. (See

The Board of Health also sponsors a bi-annual voluntary water testing program which will be available again in May of 2008. The board contracts with a testing lab which in turn provides a discount for Carlisle residents who choose to have their water tested during that period. A technician collects samples, and results are reported to the resident as well as to the BOH.

Fantasia noted that this information is used by the board to look for mineral or contaminant patterns in town. She said, "Voluntary water testing has never picked up on any real problem." While a couple of wells have tested positive for bacterial contamination over the years, she said it was usually due to bacteria introduced into the system (e.g. when installing a new pump) and not a problem with the ground water.

Water treatment—do research first

According to Fantasia, most people in this town who treat their water do so to improve the color or odor rather than for health reasons. A few wells are treated to filter out more serious contaminants, such as lead, arsenic or MTBE.

Not all contaminants are associated with health risks. Brem notes that iron, a contaminant common in many Carlisle wells, "is an element that has positive health benefits." A variety of contamination thresholds are listed on the Massachusetts Department of Environmental Protection (DEP) website:

Fantasia added that there are a number of qualified water-treatment companies in the area, and that residents should not be alarmed if they find something in their well water. "Don't immediately run out and treat it," she stated. "Treatment can be problematic in itself. How do you dispose of filters? What is the maintenance cost?" Fantasia encourages residents to bring questions to the BOH.

Public water supplies

Carlisle does not have a municipal water supply. However, there are wells that qualify as "public water supplies," defined by the state as systems which serve 25 or more users for more than 60 days per year. In Carlisle, this includes public buildings such as the school and churches. It will also include the new Coventry Woods 40B subdivision. Public water supplies are subject to greater regulation and testing. Annual compliance reports are also required and a certified well operator must be available to the site at all times.

Too little, too much seasonal variations

Since the mid-1950s, Carlisle has maintained a minimum two-acre lot size in an effort to protect the safety and abundance of its water supply. Board of Health Agent Linda Fantasia notes that in seasons with particularly low levels of rainfall, some residents are faced with decreased water pressure from their wells and three Carlisle households experienced water shortages this year. Most often this occurs with shallow wells, those that are less than 200 feet deep. Most new drilled wells in Carlisle are at least 500 feet deep.

What should one do when the water supply dwindles? Although one resident drilled a new, deeper well this summer, most others wait for increased rainfall. "I think as long as it's only a nuisance, most people just work with it," notes Fantasia. "If you wait long enough, the well usually regenerates. You just can't do three loads of laundry in a row." Fantasia said, "We also see the opposite problem. We have a situation in Buttrick Woods where we have a flowing artesian well. The water pressure is so high that it cannot be capped; an overflow [drywell] system had to be designed."



2007 The Carlisle Mosquito