Wisconsin Department of Agriculture, Trade and Consumer Protection 

March 2008 

Final Report on DATCP Evaluation of Renewed Use of Atrazine 

in Atrazine Prohibition Areas 
1 

Final Report on DATCP Evaluation of Renewed Use of Atrazine 

in Atrazine Prohibition Areas 

Background 

Introduction

The DATCP Evaluation of Renewed Use of Atrazine in Atrazine Prohibition Areas 

(hereafter referred to as the Atrazine Reuse Study) was conducted between 1998 and 

2005. The purpose of the study was to gather information to help the department 

determine if it should consider repealing atrazine prohibition areas. More specifically, 

the main objective of the study was to determine the impact of atrazine use, in 

compliance with the Wisconsin atrazine rule, on shallow groundwater in atrazine 

prohibition areas (PAs). 

Groundwater Standard for Atrazine

The Wisconsin groundwater enforcement standard (ES) for atrazine total chlorinated 

residues (TCR) is 3 ug/l (equivalent to parts per billion). This standard includes atrazine 

and its three chlorinated metabolites deethyl atrazine, deisopropyl atrazine and diamino 

atrazine. The preventive action limit (PAL) for atrazine TCR is 0.3 ug/l. 

The Wisconsin Atrazine Rule

The atrazine rule, ch. Ag 30, Wis. Adm. Code (now Ch. ATCP 30, Wis. Adm. Code), 

was created in 1991 to address atrazine contamination in Wisconsin's groundwater. This 

rule restricted the use of atrazine on a statewide basis and established PAs where atrazine 

contamination in groundwater exceeded the ES of 3 ug/l. Over the years, as additional 

testing found more drinking water wells contaminated by the use of atrazine, additional 

PAs were established. Currently there are 102 PAs in the state covering over 1.2 million 

acres. 

Repeal Process for Atrazine Prohibition Areas

The original atrazine rule did not contain a provision to repeal PAs after they were 

created. In 1998, a change was made to the atrazine rule that allows the department to 

consider repealing PAs where atrazine levels in groundwater have improved. The 

department must evaluate the following three conditions as it considers whether to repeal 

a PA: 
2 

• Tests on at least three consecutive groundwater samples, drawn from each well 

site in the prohibition area at which the atrazine concentration previously 

exceeded the groundwater enforcement standard, show that the atrazine TCR 

concentration at that well site has fallen to and remains at not more than 50% of 

the enforcement standard. The three consecutive samples must be collected at 

intervals of at least six months, with the first sample being collected at least six 

months after the effective date of the prohibition area. 

• Tests conducted at other well sites in the prohibition area reveal no other atrazine 

TCR concentrations that exceed 50% of the enforcement standard. 

• The department determines, based on credible scientific evidence, that renewed 

use of atrazine in the prohibition area is not likely to cause a renewed violation of 

the enforcement standard. 

To evaluate the first condition, the department tests wells in atrazine PAs that have 

exceeded the ES as part of an annual survey called the Exceedence Survey. For the third 

condition, the department conducted a seven year study to evaluate the impacts on 

groundwater of renewed atrazine use in PAs. This study, called the Atrazine Reuse 

Study, is the focus of this report. The second condition will only be evaluated if the 

department determines that conditions one and three have been met. 

Study Design 

With the help of the Atrazine Technical Advisory Committee, the department designed a 

study to evaluate the third repeal condition. The basic design was to conduct 

groundwater monitoring at representative agricultural fields in atrazine PAs where 

atrazine use was allowed on an experimental basis. Seventeen growers with fields in 

older (1993 or 1994) PAs throughout the state (see figure 1) provided the sites for the 

study. These growers agreed to grow corn and use atrazine on the fields selected for the 

study. The fields that were selected met soil, topographic and geologic conditions that 

allowed the study to be completed in a relatively short timeframe and at a reasonable 

cost. The groundwater beneath the selected fields was tested quarterly for five to seven 

years utilizing three shallow monitoring wells located within each of the fields. 

The soils of the study fields were grouped into coarse and medium texture categories 

following the scheme in the atrazine rule for determining maximum application rates. 

Candidate fields had to meet the following selection criteria: 

• slope less than 5% 

• water table in unconsolidated materials 

• unsaturated zone of equal or greater permeability than the overlying soil 
3 

• depth to groundwater less than 30 feet 

• water table not within the root zone of the crop being grown 

The growers agreed to use atrazine on the monitored field at least three times during the 

study and were encouraged to use the highest legal use rate in Wisconsin. Herbicide 

products containing cyanazine or simazine were not allowed to be used during the study 

since they produce two of the same chlorinated triazine metabolites as atrazine. Other 

pesticides and fertilizers were applied as needed. The growers selected the tillage and 

application method best suited for their operation. 

Figure 1. Location of the Seventeen Study Sites in the Atrazine Reuse Project 

Since the study fields were located in atrazine PAs, the size of the area where atrazine 

could be used under a research permit was limited to 10 to 40 acres. Three monitoring 

wells were installed in a line within the area to be treated with atrazine. Each well had a 

10 foot screen with 3-4 feet of open interval below the water table. Wells were sampled 

following established sample collection procedures designed to minimize the possibility 

of cross contamination. Department chain-of-custody requirements were followed to 

ensure adequate documentation of laboratory results. 
4 

Of the 17 sites in the study, one was excluded from the analysis for not disclosing the 

presence of a septic drain field in the study field and for not following other study 

protocols. Of the remaining 16 sites, seven did not meet the requirement of applying 

atrazine at least three times during the course of the study because of changes in the 

planned crop rotation or other reasons. These seven sites with only one or two 

applications of atrazine are considered separately in the analysis presented in Tables 2b 

and 3b. Results from the three wells at all the sites are shown in graphs in Appendix A. 

Sample Analysis

Syngenta, a manufacturer of atrazine, performed the laboratory analyses for the study. 

The limit of quantitation (LOQ) for atrazine, deethyl atrazine, deisopropyl atrazine, and 

diamino atrazine was 0.10 ug/l. DATCP confirmed the analyses by collecting split 

samples annually for analysis at the department’s laboratory. 

Study Results 

Table 1 summarizes the results for the 16 sites in the atrazine reuse study. Atrazine TCR 

was detected at all the sites and the 3 ug/l ES was exceeded at 12 out of 16 sites. The 

median atrazine TCR concentrations for the 16 sites ranged from 0.3 to 9.36 ug/l. It 

appears that cyanazine or simazine use at eight sites in the three years prior to the study 

had a significant impact on the atrazine TCR results during the study at those sites. 

Table 1. Summary of results from the atrazine reuse study 

Site 

Name County Soil Texture 

# of 

samples 

# of samples 

over ES for 

TCR 

# of 

wells 

over ES 

for TCR 

Concentration 

Range 

(ug/l) 

Median 

Concentration 

(ug/l) 

09A Chippewa medium 65 7 3 0.69-3.89 2.2 

13C Dane medium 83 38 2 0.45-10.4 2.8 

13J Dane medium 84 10 2 0-11.36 1.24 

23I* Green medium 72 72 3 4.28-18.5 9.36 

24H Gr. Lake coarse 72 20 3 0-5.69 1.69 

27B* Jackson medium 63 20 1 0.17-8.9 1.2 

29L Juneau medium 65 10 2 0-23.6 1.41 

39K* Marquette coarse 66 64 3 0.58-12.7 5.52 

45F* Outagamie coarse 66 25 3 0.54-6.13 2.9 

50M* Portage coarse 71 0 0 0-2.6 1.06 

50N* Portage coarse 84 2 1 0.11-4.12 0.98 

56R St. Croix medium 68 1 1 0.28-3.16 1.13 

65D Walworth coarse 72 0 0 0-0.46 0 

69P* Waupaca coarse 72 55 3 1.15-12.6 3.86 

70G* Waushara coarse 66 0 0 0-0.83 0.3 

70Q Waushara coarse 59 0 0 0-1.25 0.12 

* these sites received cyanazine or simazine in one or more of the three years before the 

start of the atrazine reuse study 
5 

Results by Site

Tables 2a and 2b summarize the results by study site. Two conditions are evaluated in 

these tables: First, did any of the three wells at a site exceed the ES for atrazine TCR 

during the study? Second, for the sites where all three wells started below the ES, at how 

many sites did one or more wells go above the ES after renewed use of atrazine began? 

Table 2a. Results by site for the nine sites with at least three applications of atrazine 

Condition Number of Sites 

One or more wells at the site had at least 

one result over the ES during the study 9 of 9 

All wells started below the ES at the site, 

with one or more wells later above the ES 4 of 4 

Table 2b. Results by site for the seven sites with one of two applications of atrazine

Criteria Number of Sites 

One or more wells at the site had at least 

one result over the ES during the study 3 of 7 

All wells started below the ES at the site, 

with one or more wells later above the ES 1 of 5 

Wells at some of the sites started out above the atrazine TCR enforcement standard even 

though atrazine had not been applied for at least five years before renewed use of atrazine 

began. This is likely due to the long half-life of atrazine in soil and water or the use of 

cyanazine or simazine, which produce two of the same metabolites as atrazine, in the 

years prior to the study. Eight of the sixteen study sites had documented use of cyanazine 

or simazine in the three years before the study began. 

Results by Well

Another way to summarize the results is by well instead of by site. These results are 

presented in Tables 3a and 3b. Two conditions are evaluated in these tables: First, how 

many wells that started below the ES later exceeded the ES? Second, for wells that 

started over the ES, how many increased by at least three μg/l (the amount of the ES) 

once renewed use of atrazine began? The results for these conditions are also presented 

by soil texture. 
6 

Table 3a. Results for 27 wells at the nine sites with at least three applications of atrazine 

Condition Number of Wells 

Wells that started below the ES and later 

exceeded the ES 9 of 16 

Wells that started above ES and later increased 

by at least 3 μg/l 9 of 11 

Wells at sites with medium texture soil that 

started below the ES and later exceeded the ES 6 of 11 

Wells at sites with coarse texture soil that 

started below the ES and later exceeded the ES 3 of 5 

Table 3b. Results for 21 wells at the seven sites with one or two applications of atrazine 

Condition Number of Wells 

Wells that started below the ES and later 

exceeded the ES 5 of 19 

Wells that started above ES and later 

increased by at least 3 μg/l 1 of 2 

Wells in medium texture soil that started 

below the ES and later exceeded the ES 3 of 5 

Wells in coarse texture soil that started below 

the ES and later exceeded the ES 2 of 14 

Conclusions 

Based on the results of the study, the department concluded that renewed atrazine use in 

PAs would likely lead to exceedences of the enforcement standard. Because of this 

finding, the department determined that condition three of the repeal process had not been 

met and decided not to consider repealing any PAs at that time. 
7 

Appendix A. Site Graphs for the 16 Sites in the Atrazine Reuse Study 

Site 09A - Medium Soil Texture (soil test coarse)

In Prohibition Area Since 1995

0

1

2

3

4

5

6

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003

Date

TCR ug/l

09A1 09A2 09A3 Atrazine Application Enforcement Standard

Site 13C - Medium Texture Soil

In Prohibition Area Since 1995

0

1

2

3

4

5

6

7

8

9

10

11

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003 12/30/2004

TCR ug/l

13C1 13C2 13C3 Enforcement Standard Atrazine Application
8 

Site 13J - Medium Texture Soil

In Prohibition Area Since 1995

0

1

2

3

4

5

6

7

8

9

10

11

12

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003 12/30/2004

TCR ug/l

13J1 13J2 13J3 Atrazine Application Enforcement Standard

Site 23I - Medium Texture Soil

In Prohibition Area Since 1996

0

5

10

15

20

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003

TCR ug/l

23I1 23I2 23I3 Enforcement Standard Atrazine Application
9 

Site 24H - Coarse Texture Soil

In Prohibition Area Since 1993

0

1

2

3

4

5

6

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003

TCR ug/l

24H1 24H2 24H3 Enforcement Standard Atrazine Application

Site 27B - Medium Texture Soil

Used Atrazine on Field in 1996

0

1

2

3

4

5

6

7

8

9

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003

TCR ug/l

27B1 27B2 27B3 Enforcement Standard Atrazine Application
10 

Site 29L - Medium Texture Soil

In Prohibition Area Since 1994

0

5

10

15

20

25

30

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003

TCR ug/l

29L1 29L2 29L3 Enforcement Standard Atrazine Application

Site 39K - Coarse Texture Soil

In Prohibition Area Since 1993

0

2

4

6

8

10

12

14

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003

TCR ug/l

39K1 39K2 39K3 Enforcement Standard Atrazine Application
11 

Site 45F - Coarse Texture Soil

In Prohibition Area Since 1995

0

1

2

3

4

5

6

7

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003

TCR ug/l

45F1 45F2 45F3 Enforcement Standard Atrazine Application

Site 50M - Coarse Texture Soil

In Prohibition Area Since 1994

0

1

2

3

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003

TCR ug/l

50M1 50M2 50M3 Enforcement Standard Atrazine Application
12 

Site 50N - Coarse Texture Soil

In Prohibition Area Since 1994

0

1

2

3

4

5

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003 12/30/2004

TCR ug/l

50N1 50N2 50N3 Enforcement Standard Atrazine Application

Site 56R - Medium Texture Soil

In Prohibition Area Since 1994

0

1

2

3

4

1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003 12/30/2004

TCR ug/l

56R1 56R2 56R3 Enforcement Standard Atrazine Application
13 

Site 65D - Coarse Texture Soil

In Prohibition Area Since 1993

0

1

2

3

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003

TCR ug/l

65D1 65D2 65D3 Enforcement Standard Atrazine Application

Site 69P - Coarse Texture Soil

In Prohibition Area Since 1994

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003 12/30/2004

TCR ug/l

69P1 69P2 69P3 Enforcement Standard Atrazine Application
14 

Site 70G - Coarse Texture Soil

In Prohibition Area Since 1993

0

1

2

3

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003

TCR ug/l

70G1 70G2 70G3 Enforcement Standard Atrazine Application

Site 70Q - Coarse Texture Soil

In Prohibition Area Since 1993

0

1

2

3

1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003

TCR ug/l

70Q1 70Q2 70Q3 Enforcement Standard Atrazine Application