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When private wells are tested, contamination is found routinely.

The N.C. State Laboratory of Public Health, in Raleigh, tests for bacteria in more than 500 private well-water samples that county health departments send each month. Those tests show that water from public systems is safer than water from private wells.

For the past seven years, almost 30 percent of the tests of private wells have been positive for total coliform bacteria. With a few exceptions, these bacteria are harmless micro-organisms, but their presence indicates that the water might have been contaminated with feces from humans or other warm-blooded animals.

When a test is positive for total coliform, the state lab follows up with a test that looks for fecal coliform and its most common member, E. coli. A positive fecal/E. coli test means the presence of bacteria or viruses that might sicken or kill. Then it's time to start boiling the water.

Over the years, the state lab has found fecal/E. coli in about 1 of every 30 private well samples. During that same period, labs that test samples from public water systems have found fecal/E. coli in about 1 in every 780 samples.

The private well samples tested by the state lab are not random. Some samples came from wells where members of a family already were sick, and some from wells flooded after a hurricane. But while the number of samples analyzed varied widely from year to year, the ratio of E. coli-positive samples has never dropped below 1 in 45.

Tests of new wells in Wake County reveal the same problem: about 1 in 80 are contaminated with E. coli.

Bill Holman, former secretary of environment and natural resources and now executive director of the state's Clean Water Management Trust Fund, says North Carolina's failure to protect either groundwater quality or private wells is "one of the biggest missing gaps" in its health system.

A creeping danger

Some contaminants, such as bacteria, can sicken or kill a family within days.

Of the 14 counties that require testing of private wells, only four look for anything other than bacteria. But scores of other contaminants, over time, are just as dangerous. Most are colorless, odorless and tasteless, so there's no warning. Like cigarette smoke, they kill so slowly that people don't notice.

The danger comes both from man-made sources and the curses of nature. The state has documented more than 25,000 known soil and water contamination sites, including contaminants such as the 1,2-Dichloropropane that poisoned the Prices' well off Poole Road near Raleigh. And there are natural killers such as arsenic, which exists in soil and minerals and can dissolve into well water.

Charles G. Pippin is a hydrogeologist in the state Division of Water Quality's office in Mooresville. He calculates that the chances of drilling a well in the Triangle and getting water with a detectable -- and therefore dangerous -- level of arsenic ranges from 2 percent in Franklin to 38 percent in Chatham.

In the two most arsenic-prone counties in the state, Stanly and Union, Pippin says the chances of finding arsenic in well water are more than 50 percent.

Radiological contaminants leaching from granite can also poison groundwater; in North Carolina, eastern Wake County is ground zero. Uranium and radium show up in public water systems in east Wake far more often than anywhere else.

Private well owners should take that as a warning, says William E. Grantmyre, former president of Heater Utilities Inc. in Cary. Heater owned about 480 public water systems -- 175 in Wake County -- prior to its sale in 2004.

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