### Page 1 of 39



### Syngenta is providing responses to questions from E PA in the e-mail titled “Triazines: Questions on CWSs” of February 27, 2009. These questions rel ate to Syngenta’s request for waiver of 80 CWS from participation in the Atrazine Monitoring P rogram (AMP). These 80 CWS were submitted previously for waiver since they have met the monitoring requirements as set forth in the Memorandum of Agreement (MOA).
EPA Question Concerning CWS Requiring Privately Contracted Monitoring Firms – “ Can you provide a list of all the CWSs that are refusing to monitor in 2009, and for which you would need to hire a company to monitor the system? “
Syngenta Response Of the 80 CWS included in our current waiver reques ts, 11 systems currently require third party sampling for complian ce with the monitoring program. These are: Hillsboro IL (IL1350300) Bedford IN (IN5247001) Winslow IN (IN5263006) Beloit KS (KS2012301) Burlington KS (KS2003101) Carbondale KS (KS2013914) Maryville MO (MO1010508) McClure OH (OH3500711) Mt. Orab OH (OH0801011) Upper Sandusky OH (OH8800511) Waynoka OH (OH8800511)
The Linn Valley Lakes POA (KS2010712) has is also b ecoming more difficult and may need to go to a third party sampler, though this CWS and all c onnections are within a fully gated community into which we are unable to send a third party to collect samples.
Questions on CWS in the AMP – The following are responses to the questions in the spreadsheet enclosed in EPA’s e-mail of February 2 7, 2009 (M. Biscoe to D. Campbell, subject: “Triazines: Questions on CWSs”). We are initially addressing only the CWS which have met the waiver criteria of the Memorandum of Agreement; add itional information on the other CWS will be provided separately.

### Page 2 of 39



### Analytical Methodology and Data Interpolation - The questions posed by the EPA are centered on concentrations of total chlorotriazines (TCT) in finished drinking water and changes in these levels in certain community water systems over spec ific timeframes. The analytical methodology used in the AMP was upda ted as the program progressed. In 2003 (and even earlier in pre-AMP monitoring programs), a technique known as immunoassay (IA) was used to screen for atrazine residues. If a res ult from IA was greater than or equal to 3 ppb, the sample was specifically quantified using Gas Ch romatography / Mass Spectrometry (GC/MS), which analyzed for parent atrazine, simazi ne, and the 3 chlorinated degradates. When some samples with IA results slightly greater than 3 ppb were reanalyzed by the directmeasurement GC/MS technique, they will at times sho w atrazine (and summed TCT) levels below 3 ppb. Starting in August 2005 (and earlier in certain CWS ), the IA and the GC/MS methodology was replaced with a new analytical method that used dir ect injection of water samples into Liquid Chromatography / Quadruple Mass Spectometry (LC/MS) . This method allowed for direct measurement of all analytes that comprise TCT in a rapid, direct injection method and eliminated the need to screen for residues with the IA method.
For EPA’s calculation of the finished water TCT 90- day rolling averages, it is our understanding that EPA used only data for which atrazine, simazin e and the chlorodegradates were specifically measured by either GC/MS or LC/MS, and did not use the IA screen results. To fill in data gaps between GC/MS or LC/MS measured values, the EPA use d linear interpolation to generate interim 90-day rolling average values. As previous ly mentioned, prior to August 2005 and the routine analysis of all samples by LC/MS, there wer e relatively few data points analyzed by GC/MS, as only those that were higher than 3 ppb by IA were reanalyzed. In the AMP, the large majority of atrazine sample concentrations have bee n less than 3.0 ppb. As a result, sole use of GC/MS data in the early years leads to a partial da ta set that over-estimates 90-day rolling average values, in many cases to a large degree, as illustrated below. In the Atrazine Memorandum of Agreement, EPA provid ed equations for the estimation of TCT from parent atrazine data. Using these equations t o generate a full set of TCT concentrations from all available IA data (plus all available GC/M S data) prior to August 2005 resulted in much lower 90-day rolling averages in most cases when co mpared to calculation using the partial data set selected by EPA. While we acknowledge tha t EPA will not be using the IA TCT result in the cumulative risk assessment, we provide this ana lysis to answer the specific questions concerning perceived decreases in TCT in certain CW S in AMP. Provided below are graphs and data summaries that compare both the full data set (defined here as TCT derived from IA, GC/MS, and LC/MS) to the partial data set (defined as TCT from GC/MS and LC/MS with linear interpolation as selected by EPA) to illustrate the effect of the use of the GC/MS for the higher

### Page 3 of 39



### residue samples. As these graphs and tables show, in many cases the TCT fluctuations and trends that are in question, are primarily a functi on of the rolling averages derived from a partial data set during the period from 2003-05. E ach CWS that has met the criteria for waiver in the Memorandum of Agreement is specifically addr essed below.

### Page 4 of 39



### EPA Question 1: “What caused the substantial drop in TCT levels between the following years?”
Westport, IN, 2003-05
Syngenta Response: The program monitoring data available for Westpor t IN, listed by analytical methodology used, are summarized in Tabl e 1. In 2003, only 3 samples in 2003 had atrazine residues greater than 3.0 ppb by IA which were re-analyzed using the GC/MS method. In 2004, no samples had residues greater than 3.0 p pb, and therefore none of the samples were analyzed by GC/MS. In 2005, 1 sample was confirmed by GC/MS and 19 were analyzed using the LC/MS method. As Figure 1 shows, use of the pa rtial data set selected by EPA (as we understand it) prior to August 2005 resulted in an over-estimation of 90-day rolling TCT levels. Using only the GC/MS analytical TCT data resulted i n a maximum 90-day TCT average value of 16.7 ppb in 2003 (see green trace in Figure 1). Ho wever, when the full data set (i.e. inclusion of TCT calculated from IA results) is used to calculat e 90-day rolling averages, the maximum 90- day TCT in 2003 is 2.55 ppb (trace with black diamo nds). As can be seen in Figure 1, the 90-day rolling averages have remained low (below 5 ppb usi ng the full data set) over the six year period. In Figure 2 the individual TCT sample resu lts have been plotted. Individual atrazine and TCT concentrations have consistently remained below 5 ppb (and most near method detection limits) with the exception of a single sample occur rence in 2003 (corresponding to an atrazine detection of 18.52 ppb on May 6, 2003) and 2 sample occurrences in 2007 (corresponding to simazine detections of 19.24 and 15.69 ppb on June 4, 2007 and June 11, 2007, respectively).

Year Total Samples (n) IA GC/MS LC/MS

2003 24 21 3 0 2004 31 31 0 0 2005 32 12 1 19 2006 32 0 0 32 2007 34 0 0 34 2008 32 0 0 32 Method 

## Table 1 Samples Analyzed by Immuno-assay, GC/MS or LCMS fro m the AMP at the

Westport, IN CWS from 2003-2008Page 5 of 39 0 5 10 15 20 25 30

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-0990-day TCT Rolling Average (ppb) Figure 1 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical Data to MS Method Only Data (With Interpolation), W estport, IN CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)

0 5 10 15 20 25 30

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 2 Individual Sample Atrazine Plus Metabolites, Simazi ne, and Atrazine Plus Metabolites Plus Simazine (TCT) in Finished Water at Westport, IN CWS from 2003-2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)Page 6 of 39



### Carlinville, IL, 2004 – 2005
Syngenta Response: The program monitoring data available for Carlinv ille, IL, listed by analytical methodology used, are summarized in Tabl e 2. Eleven of 25 analyses in 2003 and 6 of 29 analyses in 2004 were greater than 3.0 ppb by IA and re-analyzed by GC/MS. In 2005, 21 of 34 analyses were by LC/MS. When using the partial data set selected by EPA, with extrapolation between GC/MS values, to calculate 90 -day rolling averages, there is a significant overestimation in finished water 90-day TCT average s in 2003 and 2004 (Figure 3, green trace). Using the full data set, 90-day TCT levels remained steady and consistently below 4 ppb in 2003 and 2004 and below 2 ppb from 2005 to 2008 (Figure 3, black and orange traces). Individual sample results, by analytical methodology, are show n in Figure 4. Individual residue values are generally low (rarely above 4 ppb).

Year Total Samples (n) IA GC/MS LC/MS

2003 25 14 11 0 2004 29 23 6 0 2005 34 13 0 21 2006 31 0 0 31 2007 33 0 0 33 2008 30 0 0 30 

## Table 2 Samples Analyzed by Immuno-assay, GC/MS or LCMS fr om the VMP and AMP at the Carlinville, IL CWS from 2003-20 08

MethodPage 7 of 39 0 2 4 6 8 10 12 14

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 3 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical Data to MS Method Only Data (With Interpolation), C arlinville, IL CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)

0 2 4 6 8 10 12 14

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 4 Atrazine Plus Metabolites, Simazine, and Atrazine P lus Metabolites Plus Simazine in

Finished Water at Carlinville, IL 2003-2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)



### Concordia, MO, 2004 – 2005
Syngenta Response: The program monitoring data available for Concord ia, MO, listed by analytical methodology used, are summarized in Tabl e 3. Five of 24 analyses in 2003 and 7 of 31 analyses in 2004 were greater than 3.0 ppb by IA and confirmed by GC/MS. LC/MS methodology was used on 13 of 32 analyses in 2005. Using the partial data set selected by EPAPage 8 of 39



### show a slight over-estimation of 90-day TCT average s in 2003 though the results are generally very similar to the full data set results (Figure 5 ). Over the six year monitoring period (2003- 2008), the yearly maximum 90-day TCT averages varie d between 1 and 4 ppb (Figure 5). Individual data are also plotted and labeled as to analytical methodology (Figure 6).

Year Total Samples (n) IA GC/MS LC/MS

2003 24 19 5 0 2004 31 24 7 0 2005 32 19 0 13 2006 28 0 0 28 2007 24 0 0 24 2008 23 0 0 23 

## Table 3 Samples Analyzed by Immuno-assay, GC/MS or LCMS fr om the VMP and AMP at the Concordia, MO CWS from 2003-2008

Method

0 1 2 3 4 5 6 7

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 5 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical Data to MS Method Only Data (With Interpolation), C oncordia, MO CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)Page 9 of 39 0 1 2 3 4 5 6 7

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 6 Atrazine Plus Metabolites, Simazine, and Atrazine P lus Metabolites Plus Simazine in

Finished Water at Concordia, MO 2003-2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)



### Waynoka Regional Water, OH, 2004 – 2005
Syngenta Response: There were no samples where parent atrazine was g reater than 3.0 ppb, and therefore no GC/MS analyses were performed in 2 003. In 2004, 10 of 21 analyses were confirmed by GC/MS. In 2005, 6 samples were confir med by GC/MS, 15 samples were analyzed using the LC/MS method and 15 were analyzed using I A methodology (Table 4). As shown in Figure 7, the generally higher portion of GC/MS dat a resulted in nearly identical 2004 and 2005 traces using either the partial data set selected b y EPA or the full data set (including TCT calculated from IA results). Individual finished w ater sample results from 2004 to 2008 are provided in Figure 8. The Waynoka CWS uses a backup lake to fill their pr imary reservoir early in the year while surface runoff accounts for the water in the reserv oir later in the year. The backup lake uses water from a small stream called Sycamore Run. As this is a reservoir system, the water turnover is relatively slow compared to a typical strea m system, and the residues occurring in 2004 were slowly dissipated. Individual residue results in Figure 8 show that other than the single peak in 2004 and early 2005, no value has risen abo ve 3 ppb across the 6 year period.Page 10 of 39 Year Total Samples (n) IA GC/MS LC/MS

2003 13 13 0 0 2004 21 11 10 0 2005 36 15 6 15 2006 35 0 0 35 2007 35 0 0 35 2008 35 0 0 35 

## Table 4 Samples Analyzed by Immuno-assay, GC/MS or LCMS fr om the AMP at the Waynoka, OH CWS from 2003-2008

Method

0 2 4 6 8 10 12

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 7 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical

Data to MS Method Only Data (With Interpolation), Waynoka Reg Water, OH 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)Page 11 of 39 0 2 4 6 8 10 12

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 8 Atrazine Plus Metabolites, Simazine, and Atrazine P lus Metabolites Plus Simazine in

Finished Water at Waynoka Reg Water, OH 2003-2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)



### Osawatomie, KS, 2004 – 2006
Syngenta Response: The program monitoring data available for Osawato mie, KS, listed by analytical methodology used, are summarized in Tabl e 6. Six of 20 analyses in 2003 and 3 of 33 analyses in 2004 were above 3.0 ppb using IA and were re-analyzed by GC/MS methodology. In 2005, 3 samples were analyzed by GC/MS, 14 were analyzed using LC/MS methodology and 18 by IA methodology. Using the partial data set s elected by EPA, the 90-day rolling averages are overestimated to a large degree in 2004 when co mpared to the full data set, including TCT calculated from IA data. Results from the full dat a set indicate that 90-day TCT concentrations have remained low and relatively constant over the six year period (2003-2008). Maximum 90- day average TCT concentrations for this CWS have ty pically oscillated between 1 and 4 ppb, on an annual basis. Individual samples also reflect t his well established seasonal pattern from corn herbicide use (Figure 10).Page 12 of 39 Year Total Samples (n) IA GC/MS LC/MS

2003 20 14 6 0 2004 33 30 3 0 2005 35 18 3 14 2006 34 0 0 34 2007 34 0 0 34 2008 34 0 0 34 

## Table 5 Samples Analyzed by Immuno-assay, GC/MS or LCMS fr om the AMP at the Osawatomie, KS CWS from 2003-2008

Method

0 2 4 6 8 10 12 14 16 18

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 9 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical Data to MS Method Only Data (With Interpolation), O sawatomie, KS CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)Page 13 of 39 0 2 4 6 8 10 12 14 16 18

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 10 Atrazine Plus Metabolites, Simazine, and Atrazine P lus Metabolites Plus Simazine in

Finished Water at Osawatomie, KS CWS 2003-2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)



### Iberville Water District #3, LA, 2004 – 2006
Syngenta Response: The program monitoring data available for Ibervil le, LA, listed by analytical methodology used, are summarized in Table 6. Nine of 39 samples in 2003 and 9 of 46 analyses in 2004 were confirmed by GC/MS. In 2005, eight sa mples were confirmed by GC/MS, 21 were analyzed following LC/MS methods and 14 by IA. Using the partial data set selected by EPA, the 90- day rolling averages are overestimated to a large degree in 2003 and 2004 when compared to the full data set. Results from the full data set indicate that 90-day TCT concentrations have re mained low and relatively constant over the six year period (2003-2008). TCT concentrations osc illate annually between 0.5 ppb and 4 ppb following a seasonal herbicide use pattern for this stream-based CWS. Individual samples confirm the oscillating seasonal pattern which foll ows periods of herbicide use (Figure 12). Figure 12 also demonstrates that the seasonal spike s of atrazine have trended lower since 2005. This timeframe also corresponds to a period of regular watershed atrazine label education and mitigation meetings in the Iberville area.Page 14 of 39 Year Total Samples (n) IA GC/MS LC/MS

2003 39 30 9 0 2004 46 37 9 0 2005 43 14 8 21 2006 46 0 0 46 2007 46 0 0 46 2008 44 0 0 44 

## Table 6 Samples Analyzed by Immuno-assay, GC/MS or LCMS fr om the VMP

and AMP at the Iberville, LA CWS from 2003-2008

Method

0 2 4 6 8 10 12 14 16 18

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 11 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical Data to MS Method Only Data (With Interpolation), I berville, LA CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)Page 15 of 39 0 2 4 6 8 10 12 14 16 18

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 12 Atrazine Plus Metabolites, Simazine, and Atrazine P lus Metabolites Plus Simazine in

Finished Water at Iberville, LA 2003-2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)



### Aqua Illinois CWS, 2005 – 2006
Syngenta Response: Available samples for Aqua IL are listed by analy tical methodology in Table 7. Seven of 27 samples in 2003 and 4 of 33 analyse s in 2004 were confirmed using GC/MS methodology. In 2005, 5 samples were by GC/MS (con firmation of IA results), 15 by LC/MS and 15 by IA methodology. Using the partial data set s elected by EPA, the 90-day rolling averages are overestimated between 2003 through the first pa rt of 2005 when compared to the full data set (Figure 13). Results from the full data set in dicate that 90-day TCT concentrations have remained low and relatively constant over the six y ear period (2003-2008). Individual samples confirm the oscillating seasonal pattern which foll ows periods of herbicide use (Figure 14).Page 16 of 39

Year Total Samples (n) IA GC/MS LC/MS

2003 27 20 7 0 2004 33 29 4 0 2005 35 15 5 15 2006 34 0 0 34 2007 34 0 0 34 2008 35 0 0 35 

## Table 7 Samples Analyzed by Immuno-assay, GC/MS or LCMS fr om the VMP and AMP

at the Aqua IL WD, Vermillion Co., IL CWS from 2003 -2008

Method

0 2 4 6 8 10 12 14 16

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 13 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical Data to MS Method Only Data (With Interpolation), A qua IL, Vermillion Co., IL CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)Page 17 of 39 0 2 4 6 8 10 12 14 16

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 14 Atrazine Plus Metabolites, Simazine, and Atrazine P lus Metabolites Plus Simazine in

Finished Water at Aqua IL, Vermillion Co, IL 2003-2 008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)



### Versailles, IN, 2005 – 2006
Syngenta Response: Available monitoring data for Versailles IN are l isted by analytical methodology used, in Table 8. Twelve of 24 analyse s in 2003 and 23 of 31 analyses in 2004 were confirmed using the GC/MS method. In 2005, 22 were by GC/MS (IA confirmation) and 13 by LC/MS. Since there were a relatively high perce ntage of GC/MS method analyses during this time, the use of the partial and full data sets to calculate finished water 90-day TCT concentrations are nearly identical (Figure 15). 9 0-day TCT concentrations in finished water have remained consistently below 2 ppb from mid-200 5 to December 2008. Individual samples indicate a reduction in TCT concentrations after th e 2005 use season (Figure 16). A phone conversation (3/16/09) with the Versailles water plant operator revealed that they began using powdered activated carbon (PAC) approxi mately 3-4 years ago. This change in treatment process corresponds to the drop in TCT le vels observed in finished water beginning mid to late 2005 (Figure 15). The water source for Versailles is an approximately 300 acre reservoir. The water plant operator indicated that sedimentation of the lake is one of their primary concerns. Sedimentation of the reservoir w ill lead to generally poorer water quality and increased levels of eutrophication. These proc esses raise the levels of natural organic matter creating taste and odor problems as well as increased levels of disinfection byproducts. One common treatment process to reduce the disinfec tion byproduct levels is the use of powdered activated carbon.Page 18 of 39 Year Total Samples (n) IA GC/MS LC/MS

2003 24 12 12 0 2004 31 8 23 0 2005 35 0 22 13 2006 29 0 0 29 2007 33 0 0 33 2008 31 0 0 31 

## Table 8 Samples Analyzed by Immuno-assay, GC/MS or LCMS fr om the AMP

at the Versailles, IN CWS from 2003-2008

Method

0 2 4 6 8 10 12 14 16 18

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 15 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical Data to MS Method Only Data (With Interpolation), V ersailles, IN CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)Page 19 of 39 0 5 10 15 20 25 30 35 40 45

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 16 Atrazine Plus Metabolites, Simazine, and Atrazine P lus Metabolites Plus Simazine in

Finished Water at Versailles, IN 2003-2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)



### Osage County RWD #3, KS, 2005 – 2006
Syngenta Response: Available monitoring data for Osage County, KS, a re listed by analytical methodology used in Table 9. Five of 26 analyses i n 2003 and none of the 33 analyses in 2004 were confirmed using GC/MS methodology. In 2005, 2 samples were analyzed by GC/MS, 10 by LC/MS and 23 by IA. In Figure 17, 90-day TCT rolli ng averages are graphed using the partial data set selected by EPA, and the full data set wit h the regression equations used to generate TCT values for IA data. These graphs show that 90- day TCT levels have remained low over the six year period (2003-2008). TCT concentrations te nd to oscillate annually between 1 ppb and 4 ppb following a seasonal herbicide use pattern. In dividual samples also demonstrate the oscillating seasonal pattern which follows periods of herbicide use (Figure 18).Page 20 of 39

Year Total Samples (n) IA GC/MS LC/MS

2003 26 21 5 0 2004 33 33 0 0 2005 35 20 2 13 2006 33 0 0 33 2007 34 0 0 34 2008 30 0 0 30 

## Table 9 Samples Analyzed by Immuno-assay, GC/MS or LCMS fr om the AMP

at the Osage Co, KS CWS from 2003-2008

Method

0 2 4 6 8 10

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 17 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical Data to MS Method Only Data (With Interpolation), O sage Co RWD #3, KS CWS 2003- 2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)Page 21 of 39 0 1 2 3 4 5 6 7 8 9 10

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 18 Atrazine Plus Metabolites, Simazine, and Atrazine P lus Metabolites Plus Simazine in

Finished Water at Osage Co RWD #3, KS 2003-2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)



### Webster Co Water District, KY, 2005 – 2006
Syngenta Response: Available monitoring data for Webster Co, KY, are listed by analytical methodology used in Table 10. Seven of 27 analyses in 2003 and 3 of 33 analyses in 2004 were confirmed using GC/MS methodology. In 2005, 1 samp le was analyzed by the GC/MS method, 14 by the LC/MS method and 21 by IA. Using the par tial data set selected by EPA, the 90-day rolling averages are overestimated between 2003 thr ough the first part of 2005 when compared to the full data set (Figure 19). Results from the full data set indicate that 90-day TCT concentrations have remained low and relatively con stant over the six year period (2003-2008). Individual samples confirm the oscillating seasonal pattern which follows periods of herbicide use (Figure 20). A phone conversation (3/20/09) with the water plant operator revealed that they began using powdered activated carbon (PAC) 3-4 years ago, to b etter control disinfection byproducts. The raw water source for Webster County WD has remained the Green River throughout the monitoring period (wells were used prior to 1999). Ninety-day TCT concentrations in finished water have remained consistently below about 1 ppb from mid-2005 through December 2008.Page 22 of 39 Year Total Samples (n) IA GC/MS LC/MS

2003 27 20 7 0 2004 33 30 3 0 2005 36 21 1 14 2006 35 0 0 35 2007 35 0 0 35 2008 33 0 0 33 

## Table 10 Samples Analyzed by Immuno-assay, GC/MS or LCMS fr om the AMP

at the Webster Co WD, KY CWS from 2003-2008

Method

0 1 2 3 4 5 6 7

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 19 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical Data to MS Method Only Data (With Interpolation), W ebster Co WD, KY CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)Page 23 of 39 0 1 2 3 4 5 6 7

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 20

Atrazine Plus Metabolites, Simazine, and Atrazine P lus Metabolites Plus Simazine in

Finished Water at Webster Co WD, KY CWS 2003-2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)



### Piqua, OH, 2005 – 2006
Syngenta Response: Available monitoring data for Piqua, OH are liste d by analytical methodology used in Table 11. Five of 20 analyses in 2003 and 10 of 33 analyses in 2004 were confirmed using GC/MS methodology. In 2005, 8 samp les were analyzed (confirmed) using the GC/MS method, 17 by the LC/MS method and 9 by IA. Using the partial data set selected by EPA, the 90-day rolling averages are overestimated between 2003 through the first part of 2005, especially in 2004, when compared to the full data set (Figure 21). Results from the full data set indicate that 90-day TCT concentrations ha ve remained low and relatively constant over the six year period (2003-2008). Individual s amples confirm that the results have generally been low with only relatively two short-lived peaks in concentrations in the six year monitoring period (Figure 22).Page 24 of 39 Year Total Samples (n) IA GC/MS LC/MS

2003 20 15 5 0 2004 33 23 10 0 2005 34 9 8 17 2006 34 0 0 34 2007 35 0 0 35 2008 35 0 0 35 

### Table 11 Samples Analyzed by Immuno-assay, GC/MS or LCMS fr om the AMP

at the Piqua, OH CWS from 2003-2008

Method

0 10 20 30 40 50 60

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 21 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical Data to MS Method Only Data (With Interpolation), P iqua, OH CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)Page 25 of 39 0 10 20 30 40 50 60 70

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 22

Atrazine Plus Metabolites, Simazine, and Atrazine P lus Metabolites Plus Simazine in

Finished Water at Piqua, OH 2003-2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)



### Centralia, IL (discussed during teleconference)
Syngenta Response: Available monitoring data for Centralia IL are lis ted by analytical methodology used in Table 12. Eleven of 30 analyse s in 2003 and 10 of 33 analyses in 2004 were confirmed using GC/MS methodology. In 2005, 1 2 samples were analyzed by GC/MS and 20 samples were analyzed LC/MS method. The monit oring results for Centralia are graphically depicted (Figures 25 and 26, below) in the discussi on for Question 2, below. Due to the relatively high number of samples analyzed by GC/MS in 2003 and 2004, the 90-day rolling averages are similar when calculated using either t he partial data set selected by EPA, or the full data set including TCT calculated from IA. Max imum 90-day TCT rolling averages are shown in Figure 25 while the individual analyses are show n in Figure 26. A conversation with Centralia CWS plant personnel ( 3/21/09) suggest that one correlation may be that a, while Raccoon Lake used to be the primar y raw water source, around the time January 2008, the raw water source was switched to Carlyle Lake. The reason given is that this source requires less water treatment chemical input . Carlyle Lake is expected to remain as the primary raw water source for the foreseeable future

.Page 26 of 39

Year Total Samples (n) IA GC/MS LC/MS

2003 30 19 11 0 2004 33 23 10 0 2005 35 3 12 20 2006 34 0 0 34 2007 34 0 0 34 2008 35 0 0 35 

### Table 12 Samples Analyzed by Immuno-assay, GC/MS or LCMS at the Centralia, IL CWS

from 2003-2008 as part of the VMP and AMP

MethodPage 27 of 39



### EPA Question 2: “What caused/is causing the oscillatin g TCT levels in these systems?”



## CWS Name State PWSID Waiver Request Filed? Mt. Olive IL IL1170700 Yes Centralia Water Treatment Plant IL IL1214220 Yes Waverly IL IL1370450 Yes Coulterville Water Treatment Plant IL IL1570150 Yes Bedford Water Department IN IN5247001 Yes Beloit Water Department KS KS2012301 Yes Defiance OH OH2000111 Yes

Questions regarding TCT oscillations in certain CWS are explained mainly by the agricultural herbicide use pattern for corn and sorghum. For ex ample, in studying herbicide concentrations in surface water in the Lake Erie Basin, Baker and Richards 1 

### determined that peak atrazine concentrations were associated with storm events fo llowing herbicide application. Peaks in concentration were of short duration and typically followed by lower levels as the stream flow decreased. However, the peak concentrations are no t necessarily proportional to peak flows of the stream. Atrazine is typically applied once as pre-emergenc e and generally no more than twice, with second being post emergent spray. As t he cropping season progressed peak concentrations were reduced to less than or near de tection limits in the mid to late crop season (Baker and Richards 1989). Precipitation (timing a nd amount, relative to application) also plays a key role in the temporal nature of these observed TCT levels and the relative importance of these effects will vary from year-to-year. This sa me pattern of herbicide transport and pulse in surface water concentrations was also reported and discussed by Thurman et al of the USGS 2

1 Baker, David. B. and Richards, R. P., 1989. Herbic ide Concentration Patterns in Rivers Draining Inten sively Cultivated Farmlands of Northwestern Ohio. pp.103-1 20. Water Quality Laboratory, Heidelberg College, T iffin, Ohio. In: Pesticides in Terrestrial and Aquatic Env ironments, Proceedings of a National Research Confe rence, May 11-112, 1989. Diana L. Weigmann, Editor. Virginia Wa ter Resources Research Center, Virginia Polytechnic Institute and State University.

2 Thurman, E. M., Goolsby, D. A., Meyer, M. T., and Kolpin, D. W. 1991, Herbicides In Surface Waters of the Midwestern United States: The Effect of Spring Flus h. Environmental Science and Technology , October 1991, pp. 1794-1796.Page 28 of 39



### Based on almost ten years of herbicide monitoring a t seven stream/river sites with different sized watersheds in the Lake Erie Basin, Baker and Richards (1989) noted herbicide peak concentrations decreased as the stream order increa sed. In their study, the annual variability in concentrations decreased as the watershed size (and thus stream order increased). As Baker and Richards’ (1989) research showed, the seasonal use and occurrence of atrazine in surface water runoff causes an annual “oscillation” of TCT concentrations in surface water corresponding to spring/early summer runoff events. This is apparent in viewing the 90-day TCT and individual atrazine and TCT concentrations for Mt. Olive IL, Centralia IL, Waverly IL, Coulterville IL, Bedford IN, Beloit KS, and Defianc e OH. As before, we have calculated and graphed 90-day TCT rolling averages in finished wat er using the EPA procedure used in the current EPA analysis as we understand it (GC/MS dat a only prior to August 2005) as well as using the complete data set (TCT calculated from IA , GC/MS and LC/MS data). In most instances, limiting the data set to GC/MS data prod uced an over-estimation of TCT values, and in many case significantly so. Although the oscill ating pattern of TCT concentrations may still be observed, the magnitude of the fluctuation is often less than predicted using the partial data set selected by EPA. This effect is generally more pronounced in community water systems using a stream or river as the primary raw water so urce versus those systems that rely primarily on reservoirs. The following graphs (Figures 23 through 36) repres ent 90-day rolling averages for the CWS in the table above using both the partial data set sel ected by EPA (GC/MS, confirmation data set only with linear interpolation between analyses) an d the full data set (TCT calculated from IA, GC/MS and LC/MS), calculated as previously discusse d. It can be seen that in a few CWS, the oscillation is slightly exaggerated in the early ye ars when the data set is limited to the GC/MS only samples, which as previously discussed tended to over-estimate maximum 90 day rolling averages.Page 29 of 39 0 1 2 3 4 5 6 7 8 9

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09concentration (ppb) Figure 23 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical Data to MS Method Only Data (With Interpolation), M t. Olive, IL CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)

0 2 4 6 8 10 12 14 16 18 20

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 24 Atrazine Plus Metabolites, Simazine, and Atrazine P lus Metabolites Plus Simazine in

Finished Water at Old Lake, Mt Olive, IL CWS 2003-2 008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)Page 30 of 39 0 1 2 3 4 5 6 7 8 9

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-0990-day TCT Rolling Average (ppb) Figure 25 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical Data to MS Method Only Data (With Interpolation), C entralia, IL CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)

0 1 2 3 4 5 6 7 8 9

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 26 Individual Sample Atrazine Plus Metabolites, Simazi ne, and Atrazine Plus Metabolites Plus Simazine (TCT) in Finished Water at Centralia, IL from 2003-2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)Page 31 of 39 0 1 2 3 4 5 6 7 8 9

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 27 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical Data to MS Method Only Data (With Interpolation), W averly, IL CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)

0 2 4 6 8 10 12 14 16 18

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 28 Individual Sample Atrazine Plus Metabolites, Simazi ne, and Atrazine Plus Metabolites

Plus Simazine (TCT) in Finished Water at Waverly, IL CWS 2003-2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)Page 32 of 39 0 1 2 3 4 5 6 7

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 29 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical Data to MS Method Only Data (With Interpolation), C oulterville, IL CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)

0 2 4 6 8 10 12

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 30 Atrazine Plus Metabolites, Simazine, and Atrazine P lus Metabolites Plus Simazine in Finished Water at Coulterville, IL CWS 2003-2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)Page 33 of 39 0 1 2 3 4 5 6 7

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 31 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical Data to MS Method Only Data (With Interpolation), B edford, IN CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)

0 5 10 15 20 25 30

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 32 Atrazine Plus Metabolites, Simazine, and Atrazine P lus Metabolites Plus Simazine in

Finished Water at Bedford, IN CWS 2003-2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)Page 34 of 39 0 2 4 6 8 10 12

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 33 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical Data to MS Method Only Data (With Interpolation), B eloit, KS CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)

0 5 10 15 20 25 30 35 40 45 50

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 34 Atrazine Plus Metabolites, Simazine, and Atrazine P lus Metabolites Plus Simazine in

Finished Water at Beloit, KS CWS 2003-2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)Page 35 of 39 0 1 2 3 4 5 6

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 35 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical

Data to MS Method Only Data (With Interpolation),

Defiance, OH CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)

0 5 10 15 20 25

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) 

### Figure 36 Atrazine Plus Metabolites, Simazine, and Atrazine P lus Metabolites Plus Simazine in Finished Water at Defiance, OH CWS 2003 -2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)



### Question 3: What led to the increase of TCTs in Ma ryville MO from 2004-2005?
Syngenta Response: Available monitoring data for Maryville MO are li sted by analytical methodology used in Table 13. None of 22 analyses in 2003 and 2 of 33 analyses in 2004 were confirmed using GC/MS methodology. In 2005, 7 samp les were analyzed using the GC/MS method, 17 by the LC/MS method and 11 by IA. Using the partial data set selected by EPAPage 36 of 39



### (GC/MS only) in 2004 and early 2005 results in an u nder-estimation of finished water 90-day TCT concentrations in the Marysville CWS (Table 13 and Figure 37). The GC/MS results for the 2 samples in 2004 were below the initial immunoassay results, showing atrazine results of 0.71 ppb on May 17, 2004 and 1.04 ppb on December 6, 200 4. As previously mentioned, the IA method occasionally overestimated residues when. Examining the full data set (TCT calculated from IA, GC/MS and LC/MS) between 2003 and 2008 sho ws an annual maximum 90-day average TCT concentrations in finished water at the Maryville CWS have ranged from 2.4 to 4.4 ppb. Over the six year monitoring period TCT conce ntrations have remained low and relatively constant. Individual finished water TCT concentrat ions have remained below 7 ppb for duration of the six – year monitoring period (Figur e 38). These data do not indicate that there have been significant increases in TCT levels for M aryville over the monitoring period.

Year Total Samples (n) IA GC/MS LC/MS

2003 22 22 0 0 2004 33 31 2 0 2005 35 11 7 17 2006 35 0 0 35 2007 35 0 0 35 2008 30 0 0 30 

### Table 13 Samples Analyzed by Immuno-assay, GC/MS or LCMS fr om the AMP

at the Maryville, MO CWS from 2003-2008

MethodPage 37 of 39 0 2 4 6 8 10

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 37 90-day TCT Rolling Averages in Finished Water Compa ring Use of All Triazine Analytical

Data to MS Method Only Data (With Interpolation),

Maryville, MO CWS 2003-2008

90-day TCT (Full Data Set: IA, GC/MS, LC/MS Sample Results) 90-day TCT (GC/MS and LC/MS Sample Results) 90-day TCT (Partial Data Set: GC/MS and LC/MS with Linear Inte rpolation)

0 1 2 3 4 5 6 7 8 9 10

Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09Concentration (ppb) Figure 38

Atrazine Plus Metabolites, Simazine, and Atrazine P lus Metabolites Plus Simazine in

Finished Water at Maryville CWS, MO CWS 2003-2008

Atz + Metab (IA, GC/MS, LC/MS) Simazine (GC/MS, LC/MS) Atz+Metab+Sim (GC/MS, LC/MS)Page 38 of 39



### EPA Question 4: Why are there no TCT data for 2007 ? Did the source water switch, or is there another reason?
Vermont, IL
Syngenta Response: TCT concentrations for 2007 at Vermont are availa ble and have been previously provided to EPA. They are reported in T able 14 as additional reference. Please note that all 2007 samples were analyzed using LC/MS ana lytical methodology.Page 39 of 39 Date Atz + Metab

(LC/MS) Simazine

(LC/MS) Atz+Metab+Sim

(LC/MS)

01/02/07 0.4 0.05 0.45 01/16/07 0.4 0.05 0.45 01/29/07 0.33 0.03 0.36 02/12/07 0.33 0.03 0.36 02/26/07 0.33 0.03 0.36 03/12/07 0.33 0.1 0.43 03/26/07 0.33 0.03 0.36 04/02/07 0.33 0.03 0.36 04/09/07 0.33 0.03 0.36 04/16/07 0.33 0.03 0.36 04/23/07 0.33 0.03 0.36 04/30/07 2.52 0.03 2.55 05/07/07 2.84 0.03 2.87 05/14/07 1.77 0.03 1.8 05/21/07 2 0.03 2.03 05/29/07 1.44 0.03 1.47 06/04/07 1.52 0.03 1.55 06/11/07 1.29 0.03 1.32 06/18/07 1.08 0.03 1.11 06/25/07 0.98 0.03 1.01 07/02/07 1.35 0.03 1.38 07/09/07 1.77 0.03 1.8 07/16/07 0.66 0.03 0.69 07/23/07 0.83 0.03 0.86 07/30/07 1.12 0.03 1.15 08/13/07 0.89 0.03 0.92 08/27/07 0.7 0.03 0.73 09/10/07 0.63 0.03 0.66 09/24/07 0.63 0.03 0.66 10/09/07 0.42 0.03 0.45 10/22/07 0.61 0.03 0.64 11/05/07 0.92 0.03 0.95 11/19/07 0.95 0.03 0.98 12/03/07 1.04 0.03 1.07 12/17/07 0.55 0.03 0.58 Table 14 Atrazine, Metabolite and Simazine Concentrations in Fi nished Water From the Vermont, IL CWS and the Syngenta AMP, 2007