About 1,500 people in Union County rely on private domestic water supplies, primarily wells. The Ohio River alluvium is the best source of groundwater in the county. In the northern and western edges of the county, nearly all drilled wells up to 150 feet deep in the Ohio River alluvium are adequate for domestic use. Most wells yield more than 50 gallons per minute; some yield as much as 1,000 gallons per minute. In over half of Union County, most wells shallower than 300 feet penetrating sandstone are adequate for a domestic supply. In the southeastern highlands of the county, in the old Camp Breckinridge area and in the Grundy Hill area southwest of Uniontown, only a few wells yield enough water for a domestic supply. In a thin, highly faulted zone running east-west across the county between the towns of Givens and The Rocks, yields to drilled wells are unpredictable because of faulting. Generally, groundwater is hard to very hard, and iron and salt may be present in objectionable amounts. Often groundwater becomes saltier with depth.