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The PWPS Project is one component of the MDA's Monitoring and Assessment for Agriculture Chemicals in the Environment program. The larger program includes the monitoring of groundwater and surface water in the state.
Table 1: County Response Statistics for the Sampling Effort 2014-2017
During the 2014-2015 sampling, pesticides were detected above the Minnesota Valley Testing Lab method reporting limits in six of the private drinking water well samples (0.3%). The wells with pesticide detections were located in a single well from Benton, Olmsted, Sherburne, and Stearns County and two wells in Washington County. Complete pesticide results can be found in the 2014-2015 Private Well Pesticide Sampling Project Report (PDF: 321 KB / 14 pages).
Based on the results of the 2014-2015 sampling, the Minnesota Department of Agriculture contracted with a different laboratory capable of analyzing at least 125 pesticides and pesticide degradates at lower detection levels (Weck List). Homeowners who had their well sampled from 2014-2015 will be given the opportunity to have their wells resampled using the new laboratory methods.
Approximately 1,171 wells were sampled in 2016 and 1,103 wells samples in 2017 (Table 1) were analyzed for 126 pesticide and pesticide degradates. Results indicate that pesticides or pesticide degradates were detected in 70% of the wells tested. There were a total of 60 different pesticides and degradates found (Table 2). Consistent with the MDA's ambient network monitoring, metolachlor ESA (a corn herbicide degradate) was the most frequently detected compound (Table 3). Three wells exceeded a drinking water reference value (for diuron- an herbicide, methyl parathion- an insecticide, and cyfluthrin- an insecticide).
Table 3 documents concentration statistics and health reference values for pesticide chemicals detected in greater than 5% of the samples analyzed in 2016 and 2017. All concentrations are reported in ng/L, which is equivalent to parts per trillion (ppt).
Table 2: Total Pesticide Detections by County
Table 3: Concentration Statistics and Health Reference Values(pesticide chemicals detected in >5% of samples analyzed in 2016)
The 2018 Private Well Pesticide Sampling Project Work Plan is available electronically upon request. Please see MDA Contact information below.
The 2016 Private Well Pesticide Sampling Project Results report is currently under review.