Most private water wells in Clark County appeared to be contaminated by bacteria, apparently entering the wells from surface water seepage. Eighteen to 24% of the wells investigated were positive for fecal contamination. Deeper wells were less often contaminated. More than one-half of the wells sampled exceeded recommended limits of inorganic chemicals for safe potable water. High concentrations of iron and manganese were most common, exceeding recommended limits in more than 40% of the wells
Conine, S.; Cox, D.; Mitchell, K.; Kuyper, Clark; and Bragg, Jimmy D.
"Bacterial Quality of Private Water Wells in Clark County, Arkansas,"
Journal of the Arkansas Academy of Science: Vol. 43
, Article 6.
Available at: http://scholarworks.uark.edu/jaas/vol43/iss1/6