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Home > Protecting Our Lands & Waters > Clean Water Fund > Groundwater & Drinking Water Protection > Private Well Pesticide Sampling Project > Results and Work Plans

PWPS Results and Work Plans


Pesticide Results
List of All Reports

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.


Homeowner Participation

Table 1: County Response Statistics for the Sampling Effort 2014-2017

County Year PWPS Sampling Invitation Letters Mailed Number of Townships Sampled First Round Township Testing Nitrate Detections Wells Sampled
MDA List 1
2014-2015
Wells Sampled Weck List
2016-2017
Becker 2017 3 104 0 50
Benton 2015 3 307 145 0
Benton 2017 1 118 0 43
Dakota 2014 19 411 256 0
Dakota 2015 12 461 259 0
Dakota 2016 17 496 0 378
Dodge 2017 8 246 0 106
Douglas 2017 9 334 0 134
Hubbard 2017 6 534 0 279
Kandiyohi 2017 6 83 0 32
Morrison 2015 6 191 91 0
Morrison 2016 9 467 0 233
Nobles 2017 4 45 0 12
Olmsted 2015 11 414 183 0
Otter Tail 2016 31 1,009 0 431
Pope 2016 5 67 0 28
Rock 2017 7 154 0 60
Sherburne 2015 5 596 301 0
Sherburne 2016 1 249 0 119
Stearns 2015 14 905 394 7
Todd 2017 9 181 0 74
Wadena 2015 4 112 39 0
Washington 2015 2 313 173 2
Winona 2017 13 602 0 286
Total NA 176 7,903 1,841 2,274

Pesticide Results

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

County Wells Sampled Weck List 2016 Wells Sampled Weck List 2017 Total Pesticide & Pesticide Degradates Detected Total Wells with a Pesticide Detections Detection Frequency Pesticide Health Reference Value Exeedances
Dakota 375 3 31 352 93% 0
Morrison 232 1 31 184 79% 0
Otter Tail 408 23 41 244 57% 0
Pope 28 - 12 13 46% 0
Sherburne 119 - 24 99 83% 1
Stearns 7 - 5 5 71% 0
Washington 2 - 2 2 100 0
Becker - 50 15 23 46% 0
Benton - 43 13 30 70% 0
Dodge - 106 24 75 71% 0
Douglas - 134 15 46 34% 0
Hubbard - 279 31 158 57% 0
Kandiyohi - 32 17 19 59% 1
Nobles - 12 16 11 92% 0
Rock - 60 25 51 85% 0
Todd - 74 27 46 62% 0
Winona - 286 37 232 81% 1
Total 1,171 1,103 60 1,590 70% 3

Table 3: Concentration Statistics and Health Reference Values(pesticide chemicals detected in >5% of samples analyzed in 2016)

Pesticide Analyte Detection Frequency Median (ng/L) 90th Percentile (ng/L) Maximum(ng/L) Health Reference Value (ng/L) Health Reference Value Type
Metolachlor ESA 60% 35 627 6,900 800,000 HRL**
Alachlor ESA 44% <MRL* 990 12,000 50,000 RAA***
Metolachlor OXA 30% <MRL 220 12,000 800,000 HRL
DEDI Atrazine 21% <MRL 170 1,200 3,000 Partent HRL
Atrazine 21% <MRL 57 1,400 3,000 HRL
Acetochlor ESA 18% <MRL 71 2,300 300,000 HRL
Desethylatrazine 17% <MRL 83 930 3,000 Parent HRL
Hydroxyatrazine 10% <MRL <MRL 560 20,000 RA****
Bentazon 9% <MRL <MRL 3,100 30,000 HRL
*  <MRL = concentration was below the method reporting limit from the laboratory;
**  HRL = Health Risk Limit, a promulgated drinking water standard established by the Minnesota Department of Health
***  RAA = Risk Assessment Advice, a non-promulgated drinking water advice level established by the Minnesota Department of Health
****  RA = Rapid Assessment, a non-promulgated value established by the Minnesota Department of Health

Reports

2017 

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.

 

2016

2015


Additional Information

MDA Contact

Jeff Paddock
Hydrologist
jeff.paddock@state.mn.us
651-201-6560