Ground Water Quality in Southeastern Minnesota

Abstract

Water quality of 21 private wells in the karst area of southeastern Minnesota was studied from February 1977 to May 1979. The wells were located within a one-township area and were chosen for study following a questionnaire survey by type of construction and aquifer(s) in which they were completed. Thirteen routine and six runoff samples were collected from each well during the study and were examined for 18 biological, physical and chemical parameters. The parameters measured in samples from wells in the Galena Formation had the most variation with total coliform and nitrate nitrogen concentrations exceeding recommend limits for drinking water in 68 and 72 percent of the samples, respectively. Generally, it was found the median routine concentrations of all parameters studied were lower than the median runoff concentrations. There was evidence that the chemical quality of the water in the deeper aquifers supposedly protected by a major aquitard was affected rapidly by surface runoff. The parameters found to be the best indicators of surface water contamination of the aquifers and therefore indicators of possible health effects as a result of consumption of such water were: bacterial counts (total coliform, fecal coliform, fecal streptococci), nitrate nitrogen, turbidity, conductivity, sulfate, chloride, phosphate, total organic carbon, and sulfate/chloride and nitrate nitrogen/chloride ratios. No acute health effects possibly due to consumption of contaminated ground water were documented among those interviewed during the initial sanitary survey or among study participants during the actual study. However, no attempt was made to ascertain if any sub-acute health effects, due to water consumption, occurred. The results of this study indicate an urgent need to initiate a groundwater monitoring program in southeastern Minnesota for purposes of determining the short and long-term trends in water quality.