Groundwater nitrate contamination costs: A survey of private well owners

Abstract

Groundwater is an important source of drinking water in Minnesota and nation-wide. In Minnesota, 5% to 10% of drinking water wells have nitrate (NO₃) concentrations that exceed health standards. Well owners incur direct costs associated with the presence of NO₃, including costs related to treatment systems, well replacement, and purchasing of bottled water. The objective of this study was to quantify actual amounts spent by private well owners when NO₃ levels are elevated, regardless of whether the owners are aware of the contamination. Survey questionnaires asking about well characteristics, NO₃ testing, and costs of actions taken in response to elevated NO₃ were mailed to 800 private well owners in the central sand plains of Minnesota. Sixty percent of recipients returned surveys and then were sent water sampling bottles, of which 77% were returned. Nitrate was determined in the returned water samples. About 6% of wells tested greater than the US Environmental Protection Agency health standard maximum of 10 mg L^-1 (10 ppm) nitrate-nitrogen. Less than one-third of respondents had tested their water for NO₃ within the past three years. Average remediation costs were $190 y^-1 to buy bottled water, $800 to buy a NO₃ removal system plus $100 y^-1 for maintenance, and $7,200 to install a new well. Of well owners with nitrate-nitrogen over 10 mg L^-1, 24% bought bottled water, 21% installed treatment systems, 24% installed new wells, and 31% were unaware of the contamination and took no actions. Water resource planners can compare the costs described in this study to the costs of preventing aquifer contamination through education and technical and financial support. This study also demonstrates a method for representative sampling of private wells without on-site visits, and the continued need for educational programs related to routine testing.