Private wells in Belknap County have a high rate of the gasoline additive methyl tertiary-butyl enter (MtBE), according to a recent study on MtBE prevalence in public and private wells in New Hampshire conducted by the United States Geological Survey.

The study, released earlier this year, revealed that, while MtBE has been banned in New Hampshire for more than a year, the chemical compound still lingers in low levels in public and private wells in the state.

According to the Geological Survey, the study, which entailed the sampling of more than 800 wells between 2005 and 2006, represents the first comprehensive evaluation of MtBE in untreated groundwater from public and private drinking-water wells in the state.

The study revealed that MtBE well contamination is widespread, having been found in 18 percent of the public wells and nine percent of the private wells tested.

Though pervasive, levels of the gasoline additive were generally low, with a majority of wells tested having MtBE levels of less than one ppb when 13 parts per billion is the state drinking water standard. About two percent of the public wells and one percent of the private wells sampled had levels greater than 13 ppb.

There are no federal standards for MtBE; states set their own levels.

The Environmental Protection Agency states that drinking water with MtBE levels of between 20 and 40 parts per billion will not cause an unpleasant taste or odor and will not cause a significant health risk.

According to the EPA, the majority of research done on MtBE has focused on effects associated with its inhalation. Animals that inhaled high concentrations of MtBE developed cancer or experienced other health effects, such as kidney and liver damage.

The EPA's Office of Water has concluded that existing research is adequate to estimate the potential health risks of low-level MtBE exposure in drinking water; but some research supports the conclusion that MtBE is a potential human carcinogen at high doses.

Fred McGarry, assistant director of the Waste Management Division of the New Hampshire Department of Environmental Services and a co-author of the USGS study, said that, in Belknap County, 27 samples were taken from public water supply wells and 19 samples were taken from private wells.

Out of the public well samples, 7.4 percent had MtBE levels above 2 ppb. Out of the private well samples, 26.3 percent had levels above 2 ppb.

McGarry said the USGS report's findings for Belknap County are notable for two reasons, the first being that they show the county has the second-highest rate of MtBE in private wells in the state. The county with the highest rates for both public and private wells is Rockingham County, at 26.5 percent.

The second reason is that Belknap County is the only county in the state where a greater number of private wells as opposed to public well had MtBE. McGarry said he is not sure why the county is unique in that respect.

He did say the study's results show homeowners and potential homeowners with well water should be testing for MtBE because the results of the study show MtBE is still in groundwater.

While levels are not expected to get any higher because of the ban on MtBE, McGarry said it can sometimes take 20 to 40 years for MtBE to completely dissipate from some water supplies, depending on water flow and geological conditions.

McGarry said most homeowners do not test their MtBE anymore because it is not part of standard well testing and because the extra test (called a VOC or Volatile Organic Compound Test) costs approximately $150.

For those who discover they do have MtBE in their wells, the money is well-spent, McGarry said, especially if levels hovering around or above the 13 ppb drinking water standard are detected.

For private homeowners who have drinking water with MtBE levels at or above 13 ppb, DES can provide a filtration system free of charge. The treatment system is paid for through a fee on gas and oil in the state, McGarry said, noting that the systems can cost anywhere from $3,000 to $10,000, depending on whether the water has just MtBE or whether it also has other contaminants that need to be filtered out.

Joseph Ayotte, a hydrologist based at USGS's New Hampshire-Vermont Water Science Center in Pembroke and another co-author of the six-person study, said he also was perplexed by the finding.

"Belknap County is virtually tied with Rockingham County, which has by far the highest rate of accumulation of MTBE in private wells in the state," Ayotte said. "We don't know why that is."

The county with the highest rates of MtBE in public wells is Hillsborough County with a rate of 39.5 percent.

Ayotte said that, while they can't pinpoint the exact reason there are higher MtBE concentrations in some areas, researchers have identified a number of likely factors, including greater population density, proximity to fuel sources and the density of fuel sources. The rate of flow of groundwater also can affect MtBE levels, Ayotte said, noting that fast-flowing groundwater dissipates MtBE more quickly while still allowing it to build up.

All public drinking water supplies in New Hampshire must be tested annually for MtBE and other possible contaminants, McGarry said, adding that any drinking water samples that have MtBE levels of five ppb or above must be tested quarterly.

The city of Laconia gets most of its drinking water from Paugus Bay, which is an inlet to Lake Winnipesaukee, so, although that public water supply was not part of the USGS study, the city's Water Department closely monitors levels.

Seth Nuttelman, superintendent of Laconia Water Works, said MtBE was a growing problem during the early part of the current decade.

In August 2001, untreated water in Paugus Bay registered the highest level of MtBE it had ever had, which was 5.2 parts per billion.

Nuttelman said that, although the level was less than half of the maximum level of 13 parts per billion, the state requires any water supplier to notify its customers when levels reach five parts per billion or above.

Nuttelman said the MtBE was coming from boat fuel and was especially concentrated in the summer.

Because MtBE is so soluble, Nuttelman said, it is hard to separate it from the water once it's in, so, although the Laconia Water Department has a state-of-the-art filtration system, it couldn't remove much of the MtBE.

"The 5.2 parts per billion of MtBE that was in Paugus Bay in 2001 was similar to what was in people's water," Nuttelman said.

Since that high reading, Nuttelman said, the Laconia Water Department has talked with area marinas which agreed to use fuel without MtBE.

Since 2001, the city has continued to test the water in Paugus Bay for MtBE monthly from May to October and officials report that levels have consistently decreased.

Over the last two years, Nuttelman said, MtBE has been below detection level in Paugus Bay.

Nuttelman said the New Hampshire Department of Environmental Services recently granted a waiver which will allow the water department to test MtBE levels in the bay just once a year.

McGarry said the Department of Environmental Services does not plan to increase or change its testing procedure as a result of the study.

Since MtBE was banned in New Hampshire and in other states, MtBE levels have dropped.

"We've seen a significant falloff in the concentration of MtBE," McGarry said.

McGarry also noted that other states began banning MtBE in 2005 and 2006 so that, by 2006, MTBE ceased to be manufactured in the United States.

It was banned in New Hampshire in 2007.

A lawsuit is still pending in Merrimack County Superior Court, filed by the State Attorney General's Office against the major oil companies for MtBE contamination cleanup.

The only state in New England that has yet to ban MtBE in Massachusetts, McGarry said, but passing a law would be unnecessary now.

MtBE was used starting in 1979 as an octane booster, replacing lead. In 1995, blending the additive with gas to make it burn cleaner became a requirement to reduce air pollution. Scientists soon discovered that, although it reduced pollution in the air, MtBE is a pervasive water pollutant and spreads quickly.

Now most fuel distributors are using Ethanol, a clean-burning, renewable grain alcohol, as an additive.

Public water systems can use existing technologies such as air stripping, granular activated carbon (GAC) and advanced oxidation to remove MtBE contamination. Some home treatment units can also remove MtBE in tap water.