Southeastern New Hampshire is a rapidly growing region that has been identified as having moderate to high concentrations of arsenic in drinking water from ground-water sources. Southeastern New Hampshire, comprised of Hillsborough, Rockingham, and Strafford Counties, has grown in population by more than 84,500 or 12 percent over the past decade to more than 770,400 (U.S. Census Bureau, 2000). These counties contain 62 percent of the State's population, but encompass only about 22 percent of New Hampshire's land area. More than 37 percent of the population in New Hampshire uses private wells as a source for drinking water (U.S. Census Bureau, 1990). Previous studies have indicated that arsenic in ground water from bedrock wells is more prevalent in southeastern New Hampshire than in other areas of the State. These studies also indicate that the arsenic in ground water probably has geologic origins, but acknowledge that in some areas, arsenic occurrence may be related to present or past land-use practices.