Statement of Work

Exploratory investigation of statistical confidence on the upper quantiles and “peak” concentrations of currently available Atrazine moni toring data

Syngenta contact: Wenlin Chen, Email: Wenlin.chen@syngenta.com , Tel.: 336-632-2015

Peter Hertl, Email: peter.hertl@syngenta.com , Tel.: 336-632-6483 RTI contact: Roy W. Whitmore, Email: rww@rti.org , Tel.: 919-541-5809

Objectives

The objectives of this exploratory work are to dete rmine

a) What sample size is sufficient, under simple random sampling, to have a specified level of confidence, say 95%, that the ma ximum value observed in the sample exceeds a specified upper population qua ntile, say the 99 th percentile? b) What are the upper quantile values (95 th , 99 th and 99.9 th ) and their two-sided confidence limits based on the available data:

a. Safe Drinking Water Act data b. Syngenta Voluntary Monitoring Program data and the Atrazine Monitoring Program data

c. The USDA PDP dataset d. Combined data sets, where feasible c) How do the upper quantile values and confidence lim its vary across various temporal analysis domains (to be defined by RTI and Syngenta).

Note: RTI will compute statistical analysis weights for each analysis dataset to account for temporal sampling. The weight for a sample will be based on the time period from that sample to the next sample from the same CWS. Extrem e weights will be reviewed and may be truncated.

Data

Data will be provided by Syngenta in Excel format ( see attached example spreadsheet headers at end of this document). For information, a brief description of the data sets is provided below.

1. SDWA data: These data were generated by state agen cies under the Safe Drinking Water Act and cover the time frame beginning in 199 3 to the most recent 2008 with available data. The SDWA requires monitoring of fi nished drinking water at all CWS in the United States. Only surface water SDWA data will be used in this analysis. For atrazine, sampling frequencies are predominantl y quarterly or annually for most CWS drawing raw water from surface water sources.

2. Syngenta Voluntary Monitoring Program (VMP): This p rogram was initiated in late 1993 and full year data were available from 1994 to 2002. The program monitored both raw and finished water. Sampling frequency typ ically exceeded 20 samples per year and collected up to a maximum 30 raw and finis hed water samples per year. Atotal of 120+ CWS participated in the program. The CWS were invited to join the program when the SDWA annual average concentration approached 3 ppb.

3. Atrazine Monitoring Program (AMP): This data set wa s initiated in 2003 and continues to date. CWS for this program were select ed based on past annual average concentrations in SDWA monitoring. All sites exceed ing 1.6 ppb atrazine as an annual average at least once since 1997 participate in the program for a minimum of 5 consecutive years. Up to 151 CWS have participated in the program since 2003 . A high sampling frequency regime (32-35 samples/year for raw and 32-35 for finished water) was adopted, with typically four sampling ev ents per month (approximately weekly) in April, May, June, and July, and twice pe r month (biweekly) for the remainder of the year.

4. USDA PDP data: EPA will help to obtain monitoring d ata from finished water samples of community water systems.

Scope of work

RTI will perform the analyses necessary to accompli sh the objectives set out above on the timeline specified in the table below.Schedule of deliverables

Deliverable Due Date

RTI receives all datasets from Syngenta 12/23/2009

RTI reviews the datasets and prepares them for anal ysis, including temporal analysis weights 01/15/2010

RTI and Syngenta define temporal analysis domains 0 1/22/2010

RTI delivers preliminary estimates to Syngenta 01/2 9/2010

RTI receives Syngenta’s comments regarding the prel iminary estimates 02/05/2010

Draft report delivered to Syngenta 02/12/2010

If requested, RTI can participate in a meeting with EPA and Syngenta to discuss the results No later than 02/26/2010

Final report delivered to Syngenta 10 working days after EPA meeting

Respond to comments from EPA and Syngenta From the EPA meeting through 06/30/2010Example spreadsheet headers of the monitoring datasets.PWSID CWS Name StateSourceTypeWaterMovement Program YearWaterType Comment LOQ MethodSamplingDateAtrazine(ppb) Water BodyKS2020508 Altoona KS S Flowing AMP 2004 F <MDL 0.10IA 20-Dec-2004 0.05VerdigrisRiverKS2020508 Altoona KS S Flowing AMP 2005 F <MDL 0.10IA 4-Jan-2005 0.05VerdigrisRiverKS2020508 Altoona KS S Flowing AMP 2005 F <MDL 0.10IA 19-Jan-2005 0.05VerdigrisRiver