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 characterize groundwater contamination and to evaluate the effectiveness of the department’s water quality programs.
Private Well Monitoring
Private Well Sampling (Exceedance Survey)
In 2011, staff collected and analyzed groundwater samples from 36 private wells that have exceeded groundwater enforcement standards 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 concentration. As of 2011, five wells remain above the atrazine enforcement standard. In 2010 staff prepared a comprehensive report on the results of 15 years of sampling in the Exceedance Survey.
Private Well Sampling (Targeted)
The purpose of DATCP’s Targeted Sampling effort is to collect groundwater samples from potable wells in “environmentally sensitive” areas across Wisconsin and analyze those samples for nitrogen and pesticides. In general, the targeted sampling effort focuses on areas where fewer samples have been analyzed for agrichemicals in the past.
A total of 92 private wells were collected from seven areas that were “targeted” for sampling in 2011. Of the 92 samples analyzed, nitrogen was detected above the detection limit in 77 of the samples, or in approximately 87 percent of the wells. Additionally, nitrate nitrogen was detected above the Wis. Admin. Code NR 140 Enforcement Standard (NR140 ES) of 10 milligrams per liter (mg/l) in 33 of the 92 wells sampled, or in approximately 36 percent of the wells.
Total atrazine was detected in 13 of the 92 samples, or in 14 percent of the samples collected. This is slightly above the estimated statewide average of wells with total atrazine of 11.7 percent. Total atrazine was not detected above the NR140 ES of 3.0 micrograms per liter (ug/l) in any of the wells sampled, so no follow up investigations were conducted.
The two most common pesticide metabolites detected in the 2010 Targeted Sampling project were metolachlor ESA and alachlor ESA, which were detected in approximately 66 percent and 38 percent of the wells sampled, respectively. Metolachlor ethanesulfonic acid (ESA) and alachlor ESA, were also the two most commonly detected in the statewide survey, with approximately 21.6 percent of the wells having detectible concentrations of these pesticide metabolites.
This is the first year that neonicotinoid pesticides, including acetamiprid, clothianidin, imidacloprid, and thiamethoxam, were included on the analytical list for the Targeted Sampling Project.
Monitoring Well Program
The primary goal of the groundwater monitoring well program is to collect data to identify pesticides that have the potential to contaminate groundwater. This information is then used to determine whether additional measures are needed to prevent contamination above applicable groundwater standards. The department also provides information to the land owners at the well sites, the public and other state and federal agencies involved in water resource protection.
In 2011, staff collected 73 groundwater samples from 30 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 seventeen different compounds were detected in groundwater monitoring wells, but only nitrate-N exceeded its groundwater enforcement standard of 10 mg/l. Section staff also monitored groundwater at two forest seedling nursery sites to determine if pesticides used in nursery production could cause groundwater contamination.
In 2011, staff worked on two groundwater investigations at private well sites that exceeded an enforcement standard for atrazine. One of these investigations was in an existing atrazine prohibition area in Adams County and the other one in Dane County will be completed in 2012. At that time it will be determined whether a new atrazine prohibition area will be proposed.
Surface Water Sampling
Between March and September 2011, DATCP, in a cooperative effort with the Department of Natural Resources, conducted a Surface Water Sampling Project to document the impact pesticide use was having on 1) five streams in smaller watersheds, and 2) three streams flowing through largely urban areas in Wisconsin.
A total of 63 surface water samples were collected as a part of this project. Of those samples, the most frequently detected compound was metolachlor ESA, which was quantified in 90 percent of all the samples collected. The second most commonly quantified compound was alachlor ESA, which was quantified in 53 percent of the samples collected, followed by metolachlor oxanilic acid (OA) and acetochlor ESA, which were quantified in 35 percent and 12.7 percent of the samples collected, respectively. Other pesticides detected during this investigation included acetochlor OA, alachlor OA, atrazine, metolachlor, dicamba, and 2,4-D.
The results of the surface water sampling confirmed that low concentrations of pesticide products enter the streams during or after the main 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 as base flow (groundwater) independent of the timing of pesticide application or river stage. Other pesticide metabolites found that are likely being discharged into the streams as a part of base flow throughout the year include metolachlor OA, acetochlor ESA, and alachlor OA.
In 2011, the existing Environmental Quality Section private well and monitoring well databases were combined into one comprehensive database. This was done under a cooperative agreement with the Wisconsin Department of Health Services in order to make the data more usable to various interested parties. In addition, a groundwater results mapping application was developed to allow us to map the results of various reports. These improvements will allow us to better utilize our extensive groundwater quality data. One example is the following map showing all wells in Wisconsin with total atrazine levels above the 3 parts per billion enforcement standard.
In 2011 the groundwater program completed a Survey of Weed Management Practices in Wisconsin’s Atrazine Prohibition Areas. The main purpose of this survey was to evaluate differences in herbicide use and other weed control practices inside and outside of Wisconsin’s atrazine prohibition areas. A specific objective was to determine whether simazine, a triazine herbicide that is similar to atrazine, is used more extensively inside prohibition areas since atrazine is prohibited and if this could become a bigger water quality problem. Information was also collected on how prohibiting the use of atrazine affects the ability to grow corn.
The results of this survey suggest that although many corn growers would like the option to use atrazine in a prohibition area, they have adapted well to growing corn without it. Half of the respondents indicated that they do not find it more difficult to control weeds in a PA without atrazine. Only about eight percent of respondents indicated that it is much more difficult to control weeds in a prohibition area and another 32 percent said it is somewhat more difficult.
Corn growers appear to be split on the question of whether it costs more to control weeds in a prohibition area with 39 percent responding "yes" and 39 percent "no." The 39 percent that said it costs more reported an average cost increase of $13.60 per acre. Only 5 percent of the corn growers surveyed indicated that they had experienced a yield reduction in a prohibition area.
By far the most common alternative to atrazine in prohibition areas was glyphosate-containing products such as Roundup. A comparison of the use of six commonly-used herbicides inside versus outside of prohibition areas showed only minor differences. It was not possible to determine if simazine is used more inside prohibition areas due to low reported use both inside and outside of prohibition areas.
Direction for the Coming Year
We will continue all on-going groundwater sampling programs for monitoring wells and private wells. Sample numbers may be lower than in 2011 due to staff reductions. In 2011, we continued to detect thiamethoxam, clothianidin and imidacloprid from the neonicotinoid class of insecticides in monitoring wells. Depending on how extensively these compounds are found in groundwater and the level at which future enforcement standards are set, the department may have to take specific measures to manage these pesticides.
In 2011 we began the rule making process to update all maps in ATCP 30, Wis. Adm. Code, (Appendix A) using technology that was not available when the original rule was written. A public hearing on the proposed map changes was held on November 8, 2011, and the proposed changes were sent to the legislature for their final review in early 2012. We anticipate the updated maps will become part of the final rule language of ATCP 30, Wis. Adm. Code, during the year.
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