AUGUSTA -- Field work by the Maine Geological Survey has revealed that a number of private wells in greater Augusta contain dangerous levels of arsenic, uranium, and radon. The culprit, said Maine State Geologist Robert Marvinney, is not human pollution, but Mother Earth herself.

The bedrock into which these wells are drilled can dissolve these organic poisons into the well water over time, Marvinney said, making it unhealthy to drink.

Marvinney and his associates have spent the last three summers trying to better understand the relationship between bedrock -- the layer of solid rock that underlies the soil -- and groundwater quality in the greater Augusta area.

As his assistants have collected well samples across a swath of land from Purgatory to China and sent them off to a Columbia University labratory for analysis, Marvinney and several other geologists contracted by the Maine Geological Survey have profiled the various outcrops of bedrock that fleck the region's topography.

As a result, the geologists have been able to learn much about the area's bedrock: how it fits together, what it's made of, why it formed the way it did, and what it reveals about the history and evolution of the Maine's landscape.

But perhaps of more immediate concern to private well users, they have been able to better understand why 31 percent of the 800 wells sampled last summer contained poisoned water.

The scourge, it seems, are organic processes that occur below our feet.

"Rainwater goes through the soil into these cracks," he explained last week, pointing to vertical fractures lining the glittering face of an outcrop on the western bank of the Kennebec River. "A (well) driller will drill down into those solid rocks until they hit cracks that are well-connected with the waterflow. So the nature of the rocks affects the water quality directly."

There are certain types of rock, Marvinney said, that dissolve harmful elements -- such as arsenic, uranium, and radon -- into water. Several miles east of the river, near Maine Route 3, the geologist pointed out an outcrop of rusty red rocks.

Easily cracking off a chunk with his rock hammer, he pointed to its shimmering interior and explained that this bedrock was pyrite, otherwise known as "fool's gold" for its resemblance to the precious metal. Pyrite, he said, is an iron sulfide, and can contain arsenic.

If this bedrock were drilled for a well, Marvinney said, the contaminant could seep into the water and affect the health of those who drink it.

Marvinney said he wasn't too surprised to find that some area wells contained unhealthy doses of arsenic. Iron sulfides are present in much of the state's bedrock, and he said that between 10 percent and 15 percent of wells in the state exceed the threshold prescribed by the Environmental Protection Agency.

Still, he said, the rate of contaminated wells in greater Augusta was about twice the statewide rate, according to last summer's data. Additionally, a handful of wells west and southwest of the city contained dangerous levels of uranium and radon.

The Maine Geological Survey is collecting the water quality data for a global Columbia University study on the prevalence of contaminants in groundwater. Although the study is several years from completion, Marvinney said he shares the lab results with local well owners so they know as soon as possible whether their water is safe to drink.

Augusta residents benefit from a clean public water supply, Marvinney said, but about half of Maine residents use private well water. He recommended that all well-users get their wells tested.

Maine State Toxicologist Andrew Smith said that, according to a recent formal survey, about 75 percent of private well owners reported having their wells tested for contaminants. However, only 40 percent of those who had the tests knew whether they evaluated arsenic levels.

Therefore, "Only about a third of well owners statewide know that they have tested their wells for arsenic," he said. "It's important to make sure that your testing is comprehensive."

Across Maine, Smith said, he has received some reports of elevated contamination levels that are truly staggering. While the EPA has deemed unhealthful water with 10 parts per billion or higher, testers have detected arsenic at concentrations as high as 5,000 parts per billion in some wells. Uranium and radon also haveo been measured at many times the acceptable level, Smith said.

According to the World Health Organization, drinking arsenic-rich water can lead to skin, lung, bladder, and kidney cancers. Because arsenic is not easily absorbed through the skin, WHO says it is fine to use such water for bathing, hand-washing, and laundry.

The good news is that people who draw their water from contaminated wells can mitigate health risks by installing filtering equipment, which is comercially available. The bad news is that this technology can be pricey.

"Point of use" filters, which attach to a single fixture such as a faucet, can run from several hundred dollars to almost $2,000, Smith said, while "Point of entry" filters, which regulate all water passing from a well to a home, can cost anywhere between $3,000 and $5,000, depending on make and model.

"Our general recommendation is that consumers approach this as they would buying any appliance," he said, and advised that buyers research their options at the National Sanitation Foundation's Web site, www.nsf.org, and compare brands and designs to see what fits best with the needs of their well.

"If you ask me what are some of the environmental health issues I am most concerned with," said Smith, "they are the ones related to the presence of naturally occurring contaminants in well water."

By focusing on the more visible threat of pollution, he said, some Mainers forget to consider that their drinking water may be jeopardized without human interference.

To spread awareness, the Maine Center for Disease Control and Prevention's Department of Environmental and Occupational Health has sent posters and brochures to 46 town offices around the state.

There is also a page on the state's Web site instructing well owners how to identify and fix contamination problems. But in order to insure the safety and health of their families, the well owners will have to do the necessary legwork.

"If you're talking about a private well, that responsibility lies solely on the household," Smith said. "There is no state program dedicated to private well-related health issues in the same way that there is for public water."

Steve Kolowich -- 861-3811 ext. 472

skolowich@centralmaine.com

WELL WATER QUALITY

-Over the last three summers, the Maine Geological Survey has been testing private wells in greater Augusta for arsenic, uranium, and radon.

-Last year, it found that 31 percent of the wells tested contained arsenic at levels exceeding the EPA's 10 parts per billion threshold. Some wells registered the poisonous element at up to 5,000 parts per billion.

-Statewide, between 10 percent and 15 percent of private wells are estimated to have unhealthy arsenic levels. Fifty percent of Maine homes draw their water from private wells.

-The contaminants are naturally occurring and are suspected to have come from the bedrock into which the wells are drilled.

Source: Maine Geological Survey.

NATURAL CONTAMINANTS

Arsenic: Lacking a distinct smell or taste, it is difficult to tell whether water or food contain arsenic without administering a formal test. Authorities have said that ingesting water with arsenic concentrations of 10 parts per billion or higher can be unhealthful. Long-term exposure to elevated levels of arsenic in drinking water have been linked to several types of cancer.

Uranium: A commonly occurring radioactive element, the uranium-238 isotopes found in bedrock are less potent than the enriched uranium used in nuclear power plants and nuclear weapons and are therefore less likely to cause cancer. Still, authorities have said that ingesting water with uranium concentrations of 30 parts per billion or higher can be unhealthful. It is estimated that about five percent of private wells in Maine contain elevated levels of uranium.

Radon: An odorless, radioactive gas, radon is produced when uranium decays. Because it is a gas, radon is primarily an indoor air quality concern. Well water can bring radon particles into the home. Long-term exposure to elevated levels of radon, defined as 4,000 pCi/L (picoCuries per liter) has been linked to several types of lung disease, including cancer.

Sources: Agency For Toxic Substances and Disease Registry, Maine CDC.