One of the Department’s responsibilities is to implement regulations to protect groundwater from pesticide and nutrient contamination. Staff identify, 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 analyze nutrient and pesticide impacts to groundwater and to evaluate the effectiveness of the department’s water quality programs.
Private Well Monitoring
Private Well Sampling (Exceedance Survey) DATCP samples private wells statewide to evaluate the presence of pesticides and nitrate in drinking water. In 2014, staff collected and analyzed groundwater samples from 18 private wells where a pesticide had been found (at least once) in excess of its enforcement standard (ES) established under ch. NR 140, Wis. Adm. Code. This Exceedance Survey is conducted annually to check how concentrations change in these wells over time. Most of these wells are in the survey due to the presence of the herbicide atrazine. Since most of the wells are in atrazine prohibition areas, where atrazine can no longer be used, most of them have shown a decrease in atrazine concentrations. Sampling in 2014 revealed that 2 of 18 wells tested (one in Columbia County and one in Sauk County) remain above the ES for atrazine. Both of these wells are located inside the two most recently created atrazine prohibition areas (2011). DATCP staff will collect additional groundwater samples near both of these impacted in 2015 as a part of the Targeted Sampling Program. The Department also tests these wells for nitrate-N. It was also found that 12 of the 18 wells exceeded the ES for nitrate-nitrogen (10 ppm). Additional exceedance well sampling will occur in 2015.
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 2014, testing included nitrate-nitrogen, a suite of common corn and soybean herbicides, and a number of neonicotinoid insecticides.
A total of 69 groundwater samples were collected from four areas as a part of the 2014 targeted sampling effort. Nitrate-nitrogen was detected above the drinking water standard (10 ppm) in approximately 40 percent of the wells sampled. For comparison purposes, the proportion estimate from our most recent random survey of wells statewide revealed that nitrate was found to exceed the 10 ppm standard in about 9 percent of wells in Wisconsin. It is not uncommon for a higher percentage of wells in the targeted sampling program to exceed the nine percent proportion estimate simply because the wells are not selected at random, but rather because they are located within areas having high percentage of agricultural land use.
The two most commonly detected pesticide metabolites in the 2014 targeted sampling project were metolachlor ethanesulfonic acid (ESA) and alachlor ESA, which were detected in approximately 56 percent and 45 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.
Atrazine was detected in 8 of the 69 wells sampled, with a maximum concentration of 5.32 ug/l. Atrazine TCR (atrazine plus its three breakdown products) was detected at low concentrations in 16 of 69 samples collected (23 percent). Atrazine TCR was quantified above the NR140 ES (3.0 ug/l) in just two wells. Drinking water advisories were issued to the owners of these wells. The Bureau also evaluated the need to conduct detailed investigations into the source of contamination at these wells.
Several neonicotinoid pesticides including acetamiprid, clothianidin, dinotefuran, imidacloprid, and thiamethoxam were included in the list of analytical tests performed. Clothianidin was detected in four wells, imidacloprid was detected in eight and thiamethoxam was detected in three wells. All of the wells with neonicotinoid detections were located in the Central Sands growing area. The State currently has no drinking water standards for these compounds. DNR and DHS have joint responsibility for groundwater standards development, and the Department has provided the data to DNR for possible future standards development.
In 2014, staff initiated four groundwater investigations. Two investigations focused on determining the source of the pesticide atrazine in wells, and two focused on the presence of high nitrate nitrogen. The Bureau conducts groundwater investigations to document the use of the pesticides or fertilizer in the area of the impacted well(s) in an attempt 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 staff look for evidence of spillage, illegal disposal, back siphon events, or improper product handling. The results of these investigations will be known in the coming year.
Surface Water Sampling
Between March and December 2014, DATCP assisted the Department of Natural Resources (DNR) with a surface water sampling project to help determine the impact of agricultural pesticides on streams in large watersheds across Wisconsin. During the project, DNR collected the samples and DATCP analyzed them for pesticides through the Bureau of Laboratory Services (BLS).
A total of 111 surface water samples were collected. The most frequently detected compound was metolachlor ESA, a breakdown product of metolachlor, the active ingredient in a number of popular corn herbicides like Dual, Halex GT, Lumax and others. Metolachlor ESA was quantified in almost 80 percent of all samples collected. The second most commonly detected compound was metolachlor oxalamic acid (OA), which was quantified in 23 percent of the samples. This was followed by alachlor ESA (21%), total atrazine (13.5%) and acetochlor ESA (12.6%). Low concentrations of other pesticides detected included 2,4-D, acetochlor OA, alachlor OA, bentazon, imidacloprid, metolachlor, metribuzin, simazine, and thiamethoxam.
The surface water sampling project generally showed that low concentrations of pesticide products enter rivers during or after the primary pesticide application season, likely via storm water runoff events occurring mainly in June and July. The results gathered late in the year suggest that low levels of pesticide metabolites also enter streams via contaminated groundwater base flow.
Only two of the pesticides quantified were present at concentrations exceeding aquatic benchmarks established by U.S. EPA-Office of Pesticide Programs. These included the pesticides metolachlor and atrazine. A sample collected from the Milwaukee River in June revealed an atrazine concentration of 2.66 ug/l, exceeding the benchmark standard of 1.0 ug/l for acute non-vascular plants. The same sample had metolachlor at a concentration of 3.43 ug/l, exceeding the benchmark standard of 1.0 ug/l for chronic effects on invertebrates. The DNR will evaluate the meaning of these results and incorporate all of the pesticide data into their routine reporting of surface water results to EPA.
Monitoring Well Sampling
The primary goal of the groundwater monitoring well sampling project is to identify pesticides that reach shallow groundwater in agricultural use settings. The results are used to set the testing parameters for our potable well testing programs, and to help decide whether additional measures are needed to prevent contamination of groundwater that results from routine applications of pesticides. 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 2014, staff collected 38 groundwater samples from 28 field-edge monitoring well sites and analyzed them for nitrate-N and pesticides of interest. The results show that 15 different compounds were detected in groundwater monitoring wells, but that only nitrate-N exceeded its 10-ppm ES.
Section staff completed a monitoring program on water table monitoring wells located in fields at two state-owned forest seedling nurseries. The results revealed that a metabolite of the pesticide dacthal was impacting the groundwater below one of the nursery sites. While no NR 140 ES was exceeded, staff were able to suggest that the nursery eliminate the use of dacthal at that facility. Once dacthal was eliminated, the concentrations decreased sharply over time. Staff submitted a final letter report to DNR recommending that the sampling program end, and the wells will be abandoned in 2015.
In 2014, Atrazine Use Observations were completed in 12 atrazine prohibition areas (PAs). These observations serve a two-fold purpose. First, as an outreach reminder to growers that atrazine use is prohibited on fields located inside of a PA. And second, as an enforcement tool to deter the potential for misuse of atrazine inside of PAs. In 2014, two violations involving the use of atrazine inside of PAs were discovered as a direct result of performing Atrazine Use Observations. These violations were referred to the Investigation and Compliance Section for enforcement action.
DATCP staff also coordinated with DNR the testing of sediment samples collected from 33 streams across the State for pesticides. Similar to the surface water sampling work, the sediment samples were collected by DNR staff and submitted to DATCP BLS for analysis. BLS will complete the testing in early 2015 and the results will be sent to DNR for inclusion in their reports on surface water quality.
Direction for the Coming Year
In 2015, we will be completing the planning work associated with conducting a statewide survey of groundwater quality in private wells. The planned survey will actually begin in 2016, but there is significant planning involved with this undertaking. As a part of this effort, DATCP Environmental Quality Staff have initiated discussions with staff from the National Agricultural Statistics Service-Wisconsin Field Office to help develop a stratified random sampling design similar to our last survey conducted in 2008. Work to be completed in 2015 includes writing and submitting grant proposals to help fund this significant undertaking, as well as coordinating the effort with DATCP’s Bureau of Laboratory Services.
We also will continue to work with Bayer Crop Science to discuss the possible registration of herbicide products containing isoxaflutole. Isoxaflutole is a selective herbicide for control of certain broadleaf and grass weeds in field corn (and potentially other crops). It is the active ingredient in Corvus Herbicide, Balance Pro and Balance Flexx. Wisconsin originally proposed a restricted registration of isoxaflutole to the registrant in 1990 due to concerns over possible surface and groundwater contamination and effects on non-target plants. The registrant decided to not register their products in Wisconsin at that time, but has begun working with the department again on registration discussions.
For more information about any of the bureau programs you may email the department.
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