One of the department’s responsibilities is to implement regulations to protect groundwater from pesticide and nutrient contamination. Staff identifies, monitor, and analyze problem areas within the state, investigate wells that exceed groundwater standards to identify potential sources of contamination, and conduct statewide sampling surveys to characterize groundwater contamination and to evaluate the effectiveness of the department’s water quality programs.
Private Well Monitoring
Private Well Sampling (Exceedence Survey): In 2013, staff collected and analyzed groundwater samples from 28 private wells that have exceeded groundwater enforcement standards in the past to track how the pesticide and nitrate-N levels in these highly-impacted wells are changing over time. Most of these wells are in atrazine prohibition areas and most have shown declines in atrazine concentrations. As of 2013, five of the 28 wells (three in Columbia Co., one in Sauk Co., and one in Dane county) remain above the NR 140, Wis. Adm. Code, Enforcement Standard (NR 140 ES) for atrazine. Additionally, 22 of the 28 wells exceeded the NR 140 ES (10 ppm) for nitrate-nitrogen in 2013. The majority of these wells are in comparatively newer atrazine prohibition areas.
Private Well Sampling (Targeted): The purpose of DATCP’s Targeted Well Sampling Program is to collect groundwater samples from private wells located in environmentally sensitive agricultural cropping areas across Wisconsin. Samples are analyzed for specific agricultural contaminants to evaluate the need for issuing drinking water advisories or developing groundwater protective measures in an area. In 2013, testing included nitrate-nitrogen, a suite of common corn and soybean herbicides, and a number of neonicotinoid insecticides.
A total of 77 groundwater samples were collected from four areas as a part of the 2013 Targeted Sampling Program. Samples were collected from homes located in the agricultural areas of the state shown on the above figure. In the four targeted sampling areas, nitrate-nitrogen was detected above the drinking water standard of 10 ppm in 65 percent of the wells sampled. The statewide average of wells that exceed the drinking water standard for nitrate nitrogen estimated in our statistically-designed statewide surveys which utilize randomly-selected wells is around 9 percent,.
Early in 2013, the department received a request from the Trempealeau County Health Department to help evaluate the occurrence of high nitrate they discovered in two private wells southwest of Galesville. Upon seeing the sandy environmental setting of these wells, department staff added the area surrounding these private wells to our 2013 targeted sampling program. The department also assisted the County by conducting an investigation into possible point sources of nitrate near the two wells. No point sources of nitrogen were discovered during the investigation near the two wells. It was apparent from the investigation and the targeted sampling in the area that widespread agricultural uses of both chemical and animal waste fertilizers have likely contributed to nitrate exceedences over a broad area of the county.
In the Trempealeau County area, nitrate-nitrogen exceeded the drinking water standard in all thirteen wells sampled. During 2014, staff will discuss the results of the sampling efforts in Trempealeau County with the DNR, the Trempealeau County Health Department, and our own Land and Water Resources Bureau. It is hoped that through these discussions action can be identified and taken to encourage or maybe require best management practices (like nutrient management planning) in an effort to encourage growers to reduce the amount of nitrogen fertilizers used on crops.
The two most commonly detected pesticide metabolites in the targeted well sampling program include metolachlor ESA and alachlor ESA. Each was detected in approximately 57 percent and 69 percent of the wells sampled, respectively. Metolachlor ESA and alachlor ESA were also the most commonly detected compounds in DATCP’s statewide survey of 2007, with approximately 21.6 percent of the wells having detectable concentrations of these pesticide metabolites. No NR 140 ESs were exceeded for either of these compounds, but a well in Waushara County had an Alachlor ESA concentration of 15.7 ug/l, which approaches the NR 140 ES of 20 ug/l for this compound. The department plans to resample this well in 2014.
Atrazine total chlorinated residues (TCR) were quantified in 23 of the 77 wells, or in 30 percent of the samples collected. This is above the predicted statewide average of 11.7 percent. Atrazine TCR was not quantified above the NR 140 ES (3.0 ug/l) in any of the wells sampled. The atrazine NR 140 ES includes atrazine and its three chlorinated metabolites deethyl atrazine, deisopropyl atrazine and diamino atrazine.
Neonicotinoid pesticides, including acetamiprid, clothianidin, imidacloprid, and thiamethoxam were also included on the analyte list for the targeted sampling program. Clothianidin was detected in three wells, imidacloprid in eight, and thiamethoxam was detected in five wells. All of the wells in the Targeted Sampling Program showing neonicotinoid pesticides are located in the Central Sands vegetable growing area of the state. The highest concentration of clothianidin was 3.88 ug/l, the highest concentration of imidacloprid was 1.59 ug/l, and the highest concentration of thiamethoxam was 1.13 ug/l. Drinking water standards do not currently exist for these compounds.
In 2013, staff initiated two pesticide groundwater investigations based on the results of samples collected from the Targeted Well Sampling Program, and the one nitrate investigation requested by the Trempealeau County Health Department (discussed above). The two pesticide groundwater investigations focused on findings of alachlor ESA and metolachlor in private drinking water wells. The groundwater investigations were completed to document the use of the pesticides in the area of the impacted well(s) and to determine if department rules (containment, spills, product handling) have been violated. During an investigation, local growers are interviewed regarding their pesticide and fertilizer use history, and DATCP field staff looks for evidence of spillage, illegal disposal, back siphon events, or product mishandling.
The results of the alachlor ESA investigation showed that, while alachlor had historically been widely used in the area investigated, no alachlor had been used there within the last 10 years. Alachlor ESA is an environmental breakdown product of the parent herbicide alachlor. It was concluded that the alachlor ESA in the impacted well reflects the historic use of a pesticide that is no longer used in the area. The well owner has obtained water from an alternative source.
The metolachlor investigation remains ongoing at this time. Regardless, the impacted well has been abandoned and replaced using financial assistance from DNR’s Well Compensation Program. No other wells sampled in the area showed elevated concentrations of metolachlor.
Surface Water Sampling
Between May and October 2013, DATCP, in a cooperative effort with the Department of Natural Resources (DNR), conducted a Surface Water Sampling project to document the impact pesticide use is having on surface water in large watersheds in the Wisconsin. Departing from our previous sampling efforts, in 2013 samples were collected from eight of the State’s larger drainage basins, including the Mississippi and Wisconsin Rivers.
A total of 47 surface water samples from eight rivers were collected as a part of this project. The most frequently detected compound was metolachlor ESA, which was quantified in 81% of all the samples collected. The second most commonly detected compound was alachlor ESA, which was quantified in 51% of the samples collected. The second most commonly detected compound was alachlor ESA, which was quantified in 51% of the samples collected, followed by acetochlor ESA and metolachlor OA, which were quantified in 32% and 23 % of the samples collected, respectively. Other pesticides detected during this investigation included acetochlor, alachlor, alachlor OA, acetochlor, atrazine dicamba, 2,4-D, and metolachlor.
None of the pesticides quantified had a concentration greater than its U.S. EPA’s Office of Pesticide Program’s Aquatic Benchmark, although the concentration of metolachlor in the Wisconsin River in June sampling event (0.926 ug/l) was very close to the 1.0 ug/l benchmark for chronic impact to invertebrates. No samples contained any pesticide at a concentration approaching an NR 140 Enforcement Standard.
The results of this surface water sampling project again confirmed that low concentrations of pesticide products enter rivers during or after the primary pesticide application season and storm events, mainly in June and July. The results also show that low levels of pesticide metabolites, predominately metolachlor ESA and alachlor ESA, enter the stream through groundwater base flow independent of the timing of pesticide application or river stage. Other pesticide metabolites likely being discharged as a part of base flow include metolachlor OA, acetochlor ESA, and alachlor OA.
Monitoring Well Sampling
The primary goal of the groundwater monitoring well sampling project is to identify pesticides that have the potential to contaminate groundwater. This information is used to determine whether additional measures are needed to prevent contamination above applicable groundwater standards. The department also provides the data collected to the land owners at the well sites, the public and other state and federal agencies involved in water resource protection.
In 2013, staff collected 36 groundwater samples from 28 field-edge monitoring well sites and analyzed them for nitrate-N and pesticides of interest. Table 1 is a summary of the groundwater sample results from the field-edge monitoring well project. It shows that twelve different compounds were detected in groundwater monitoring wells, but only nitrate-N exceeded its ES.
Section staff also monitored groundwater quality at a State-owned forest seedling nursery site to determine if pesticides used in nursery production could cause groundwater contamination. DATCP has narrowed the analytical list at this tree forest nursery to the metabolites of the pesticide “dacthal,” which is the only compound detected there. Upon discussion of past results with DNR staff, the use of dacthal was discontinued. The concentration of dacthal metabolites in groundwater has decreased steadily after 2010 when nursery staff stopped using the product. In 2014, DATCP will again test the nursery wells for dacthal metabolites and will reconsider whether to continue testing in future years.
In 2013, “Atrazine Use Observations” were completed within 12 atrazine prohibition areas (PAs). These observations serve a two-fold purpose: as an outreach reminder to growers that atrazine use is prohibited on fields they have inside of PAs; and, as an enforcement tool to check application records for any possible pesticide misuse inside the PAs. In 2013, no violations involving the use of atrazine inside of PAs was discovered as a direct result of performing these Atrazine Use Observations. However, the department’s response to a reported spill of atrazine product that occurred within a PA lead to the discovery of multiple uses of atrazine on fields located within one prohibition area by one custom application company. Our enforcement staff will finalize the investigation and bring enforcement proceedings against the certified pesticide applicators and the company involved during 2014.
DATCP staff also coordinated with DNR the testing of sediment samples collected from 50 streams across the State of Wisconsin for pesticides. The sediment samples were collected by DNR staff and submitted to BLS for analysis. A final report will be submitted by DNR to U.S. EPA discussing the quality of sediment in the sampled streams.
DATCP and DNR also collaborated on an effort to test a Manitowoc County lake for pesticides as part of a health-related complaint to DNR. DNR field biologists sampled the lake, while DATCP-BLS analyzed the samples for pesticides. Although inconclusive from a health perspective, a low concentration of 2,4-D was detected in the sample.
Direction for the Coming Year
We continue to work with the Agrichemical Technical Advisory Committee (ATAC) to discuss the possible registration of herbicide products containing isoxaflutole, which is the active ingredient in Corvus Herbicide, Balance Pro and Balance Flexx. Isoxaflutole is a selective herbicide for control of certain broadleaf and grass weeds in field corn (and potentially other crops).
Wisconsin originally offered a restricted registration of isoxaflutole to the registrant in 1999. The restrictions were offered in a special order that the registrant would have had to agree to, in order to register their products for use in Wisconsin. At the time, the agency and DNR had significant concerns over possible surface and groundwater contamination and effects on non-target plants. The registrant decided to not register their products in Wisconsin due to the added requirements listed in the special order. The registrant is again seeking registration of the product based on new information and the product use history in other states.
For more information about any of the bureau programs you may email the department.
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