Document ID: EPA-HQ-OPP-2003-0334-0008
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2007-09-20T04:00Z

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<p>CM2<br />
Rm 1126<br />
1921 Jeff. Davis Hwy.<br />
Arlington, VA</p>

<p><strong>On this Page</strong></p>

<ul>
<li><a href="#attendees">Attendees</a></li>
<li><a href="#welcome">Welcome and Introduction</a></li>
<li><a href="#action">Old Action Items</a></li>
<li><a href="#brief">Brief Updates</a></li>
<li><a href="#next">Next Meeting</a></li>
<li><a href="#actions">Action Items</a></li>
</ul>

<hr />

<h2 id="attendees">Attendees</h2>

<table class="table zebra" summary="Attendees">
<thead>
<tr><th scope="col">Name</th><th scope="col">Association</th></tr>
</thead>
<tbody>
<tr><td>Michael Barrett</td><td> OPP/EFED</td></tr>
<tr><td>Dirk Young</td><td>OPP/EFED</td></tr>
<tr><td>Betsy Behl</td><td>OPP/EFED</td></tr>
<tr><td>William Eckel</td><td>OPP/EFED</td></tr>
<tr><td>Ron Parker</td><td>OPP/EFED</td></tr>
<tr><td>Mark Corbin</td><td>OPP/EFED</td></tr>
<tr><td>Lucy Shanaman</td><td>OPP/EFED</td></tr>
<tr><td>Cheryl Sutton</td><td>OPP/EFED</td></tr>
<tr><td>Faruque Khan</td><td>OPP/EFED</td></tr>
<tr><td>Mohammed Rahman</td><td>OPP/EFED</td></tr>
<tr><td>Jim Lin</td><td>OPP/EFED</td></tr>
<tr><td>Nelson Thurman</td><td>OPP/EFED</td></tr>
<tr><td>Donna Randall</td><td>OPP/EFED</td></tr>
<tr><td>Karen McCormack</td><td>OPP/EFED</td></tr>
<tr><td>Christine Hartless</td><td>OPP/EFED</td></tr>
<tr><td>James Hetrick</td><td>OPP/EFED</td></tr>
<tr><td>Norm Birchfield</td><td>OPP/EFED</td></tr>
<tr><td>David Miller</td><td>OPP/HED</td></tr>
<tr><td>Paul Whatling</td><td>Cheminova</td></tr>
<tr><td>Russell Jones</td><td>Bayer</td></tr>
<tr><td>Dean Scott</td><td>BNA Daily Env Report</td></tr>
<tr><td>Piyush Singh</td><td>Valent</td></tr>
<tr><td>Neil Shah</td><td>Inside Washington</td></tr>
<tr><td>Brent Solomon</td><td>Valent</td></tr>
<tr><td>Mary Nett</td><td>WQC</td></tr>
<tr><td>Wenlin Chen</td><td>Syngenta</td></tr>
<tr><td>Paul Hendley</td><td>Syngenta</td></tr>
<tr><td>Scott Jackson</td><td>BASF</td></tr>
<tr><td>Elise McCoy</td><td>FMC</td></tr>
<tr><td>Uwe Wanner</td><td>Crompton</td></tr>
<tr><td>Larry Burns</td><td>NERL/Athens</td></tr>
<tr><td>Mark Cheplick</td><td>Waterborne</td></tr>
<tr><td>Joe Bagdon</td><td>USDA - NRCS</td></tr>
<tr><td>Amanda Harrah</td><td>Toxcel LLC</td></tr>
<tr><td>Maria Ball</td><td>Waterborne</td></tr>
<tr><td>Kevin Armbrust</td><td>MS State/MSCL</td></tr>
<tr><td>Ric Lopez</td><td>EPA/ORD</td></tr>
<tr><td>Anne Neal</td><td>EPA/ORD</td></tr>
<tr><td>Anne Pitchford</td><td>APA/ORD/NERL</td></tr>
<tr><td>Jim Cowles</td><td>Wash State Ag</td></tr>
<tr><td>Cathleen Hapemen</td><td>USDA/ARS</td></tr>
<tr><td>Charlie Crawford</td><td>USGS</td></tr>
<tr><td>Susan H. Youngren</td><td>Burgrean and Campell</td></tr>
<tr><td>Skip Vecchia</td><td>USGS</td></tr>
<tr><td>T.S. Ramanarayan</td><td>Bayer</td></tr>
<tr><td>Stuart Cohen</td><td>Turf Envir. Services</td></tr>
<tr><td>James Breithaupt</td><td>OPP/EFED</td><td></td></tr>
</tbody>
</table>

<p class="pagetop"><a href="#content">Top of page</a></p>
<hr />

<h2 id="welcome">Welcome and Introduction</h2>

<p>Michael Barrett (OPP/EFED) opened the meeting and welcomed the group.</p>

<p class="pagetop"><a href="#content">Top of page</a></p>
<hr />

<h2 id="action">Old Action Items</h2>

<ol>

<li><p>Russell Jones (Bayer) to circulate reference to Piacenza journal with details of the conference proceedings - <strong>done</strong></p></li>

<li><p>Don Wauchope (USDA) to circulate an Excel spreadsheet of combined databases when
available - <strong>still outstanding</strong></p></li>

<li><p>Michael Barrett (OPP/EFED) to consider adding a progress update on the EPA fate database - <strong>to be covered at a future meeting</strong>.</p></li>

<li><p>Dave Jones' group to report on progress on Rice Tier 1 Model at next meeting - <strong>Jim Breithaupt to cover in his presentation today.</strong></p></li>

<li><p>Ron Parker to check on availability of National Dunne Overland Flow data on USGS web site - <strong>Charlie Crawford released this GIS coverage.</strong></p></li>

<li><p>Michael Barrett to add an agenda item to review background to WARP together with initial results from the CWS's for next time (and invite Charlie Crawford) - <strong>see later presentations.</strong></p></li>

<li><p>Paul Hendley to circulate outcome of SDTF meeting on June 11 via list server - <strong>see later update.</strong></p></li>

<li><p>Instructions for accessing and installing the latest version of EXPRESS were made available at the end of the meeting after some people had left.  These will be posted on the Website and a note sent to alert people of their availability - <strong>This is not currently an EPA official model (Please see below).  While a direct link is not currently provided on the EMWG</strong> webpage, a ftp link to a developmental version (close to a Beta Version) can be obtained from Marty Williams or Mark Cheplick at Waterborne Environmental: 
<a href="http://www.waterborne-env.com/modeling/model_topic_przm.html">
http://www.waterborne-env.com/modeling/model_topic_przm.html</a>
<a href="http://www.epa.gov/epahome/exitepa.htm" title="EPA's External Link Disclaimer"><img src="http://www.epa.gov/epafiles/images/epafiles_misc_exitepadisc.gif" width="87" height="13" alt="Exit EPA Disclaimer" /></a></p></li>

<li><p>EFED to post PL4 on Web site - <strong>done.</strong></p></li>

<li><p>EFED will consider adding agenda item on Tier 2 Groundwater needs and conceptual model for September EMWG meeting - <strong>moved to January agenda.</strong></p></li>

<li><p>Russell Jones offered to coordinate presentation of the soils types/setting where PRZM works and why and whether there are any other viable alternative models for the other soils. EFED to consider adding to agenda - <strong>done</strong>.</p></li>

<li><p>Michael Barrett will schedule progress reports on EFED research programs at next EMWG meeting - <strong>possible January item</strong>.</p></li>

<li><p>Michael Barrett will circulate PGW database templates from last meeting and arrange for a discussion topic at the September meeting - <strong>moved to future</strong>.</p></li>

<li><p>Don Wauchope will post the ACS symposium  on soil dissipation (Spring 2004) on the
FIFRA-EMWG Web site - <strong>not done yet</strong>.</p></li>

<li><p>Bill Eckel will give update on half-life calculation policy for pesticide exposure models - <strong>see later update.</strong></p></li>

<li><p>All are recommended to pass information on the algal inhibition technology on to others that they work with who might be interested in herbicide and syngergism screens - <strong>done</strong>.</p></li>

<li><p>Jerry Hannan to post synergism talk on Web site -<strong> not done</strong>.</p></li>

<li><p>Thuy Nguyen to post QA/QC presentation on Web site- <strong>not done yet</strong>.</p></li>

<li><p>It would be useful to get an update on the spatial approach for defining ponds and watershed sizes that EPA's intern is developing - <strong>see later presentation</strong>.</p></li>

<li><p>Jim Carleton may want to share the pond area/watershed ratio for the example HUC to see if there is useful information that can be drawn from the area comparison data sets - <strong>not yet</strong>.</p></li>

<li><p>EPA to post Gail Thelin's presentation after rechecked by USGS on the Web site - <strong>The material is still interim, interested parties should contact Gail directly for more information on her presentation: </strong><a href="mailto:gpthelin@usgs.gov">gpthelin@usgs.gov</a> .</p></li>

<li><p>EPA to check on availability of an orchard spray drift study run in concert with Mexico in the mid to late 90's - <strong>no data available</strong>.</p></li>

<li><p>Dave Valcore and Andrew Hewitt to supply  copies of their presentations to EPA for posting on the Web site - <strong>done</strong>.</p></li>

<li><p>Gerry Laniak to make his slides available via the Web - <strong>not done yet</strong>.</p></li>

</ol>

<p class="pagetop"><a href="#content">Top of page</a></p>
<hr />

<h2 id="brief">Brief Updates</h2>

<ol>

<li><h3>Update on New Half-life Calculations Policy - Bill Eckel  (Hand-out)</h3>

<p>Development of this policy is a continuation of the Input Parameter Guidance for EFED aquatic modeling efforts.  The goal is to harmonize first and second tier risk assessment half-life calculations among EPA reviewers and contractors.  This proposed policy has been drafted and discussed in the technology teams but has not been approved by management.  After the policy is approved, it was agreed that the details should be presented at an upcoming EMWG meeting along with the findings of the FOCUS kinetics group.</p>

<p>In his presentation, Bill Eckel mentioned that:</p>

	<ul>

	<li><p>Although our models use first-order kinetics, EFED recognizes that first-	order may not be appropriate for all situations  As a result, we have tried to find 	the most general method for best first-order fit to data sets.</p></li>

	<li><p>The proposed policy allows either traditional log-linear regression or non-	linear exponential decay analysis without data weighing; all data must be included 	in the regression.</p></li>

	<li><p>This approach avoids over-estimation of half-lives caused by use of log 	linear regression on data sets that are non-linear in log space.</p>  </li>

	<li><p>The reviewer must decide which residues (e.g., bound residues) to include as 	parent based on appropriateness of extraction efforts.</p>  </li>

	<li><p>Fit is determined informally by comparing computed intercept, half-life, and 	3 x half-life to empirical initial concentration, DT50 and DT90, respectively; the 	method that best fits the empirical data is chosen.</p></li>

	<li><p>Chemical concentrations that do not decline below detection and past a 	certain time in the experiment, and are not well-fit by the chosen rate constant, 	are reported for use in other parts of the risk assessment.</p></li>
	</ul>

<p><strong>Questions</strong></p>

<p>Q.  Is this policy linked to the FOCUS kinetics workgroup outputs?</p>

<p>A.  Yes, but at a low level. </p>

<p>Q.  What happens if the policy process results in half-life estimates that continue to be unrealistic?</p>

<p>A.  If an arguable case exists for continuing fitting approaches, this may be acceptable provided there are supporting facts.</p>

<p>Q.  When will this policy be approved by management?</p>

<p>A.  If should be within three months.  After it is approved, we will circulate details and include a discussion at the next meeting.</p>

</li>
<li><h3>SCI-GROW - Michael Barrett</h3>

<p>A new version of SCI-GROW on the EMWG Web site is a Windows version.  It was designed to replicate the code of the existing version and should replicate the model output exactly.  Further changes to improve simulations will not be made until the EFED groundwater group (tech team subgroup) has agreed on a direction for the Tier 2 groundwater model development program.  </p>

</li>
<li><h3>EU Modeling Issues - Russell Jones</h3>

<p>There have not been any  significant changes in the surface water and groundwater scenarios.  There is a new version of PERL which can be downloaded from their Web site.  The Landscape and Mitigation group and a new groundwater group is looking at risk assessments and scenarios.  They  should be finished early next year.  The Kinetics group will meet in December and the first draft report is being reviewed by the group.  Draft reports should be available soon.   </p>

</li>
<li><h3>PRZM-EXAMS/EXPRESS - Larry Burns/Mark Cheplick</h3>

<p>The most recent version of PRZM-EXAMS is on the CEAM Web site.  Mark Cheplick reported
that there are three versions of PRZM with significant use worldwide:</p>

	<ol>
	<li><p>PRZM 3.12.1 - primary user CEAM</p></li>
	<li><p>PRZM 3.12 - primary user OPP</p></li>
	<li><p>PRZM 3.24 - primary user the European Union</p></li>
	</ol>

<p>Syngenta recently funded investigation of a revision of code to take into account variable adsorption/desorption.  Mark has programmed test versions with a drain tile routine into PRZM and some turf thatch routines.  </p>

<p>Currently the following versions are available on the CEAM web pages:</p>

<p>PRZM 3.12.1 (released 8/03) at 
<a href="http://www.epa.gov/ceampubl/gwater/przm3/index.htm">http://www.epa.gov/ceampubl/gwater/przm3/index.htm</a></p>

<p>EXAMS 2.98.04 (released April 2003) at 
<a href="http://www.epa.gov/ceampubl/swater/exams/index.htm">http://www.epa.gov/ceampubl/swater/exams/index.htm</a></p>

<p>The most recent information on the OPP Models is on the web at:</p>

<p><a href="http://www.epa.gov/oppefed1/models/water/index.htm">http://www.epa.gov/oppefed1/models/water/index.htm</a></p>

<p>The following versions are being used by OPP:</p>

<p>PRZM version 3.12 (dated May 24, 2001); not directly available on the web but a link is provided to Dr. Lawrence Burns' email to request this model.</p>

<p>EXAMS 2.98.04 (released April 2003).</p>

<p>The Input Guidance document on the web is outdated and does not currently reflect the current version of EXAMS (it also does not have the correct current version for SCI-GROW):</p>

<p><a href="http://www.epa.gov/oppefed1/models/water/input_guidance2_28_02.htm">http://www.epa.gov/oppefed1/models/water/input_guidance2_28_02.htm</a></p>

<p>EPA/OPP is in the process of funding the development of a users manual for EXPRESS (the test version of EXPRESS currently has capabilities for running any of the three versions of PRZM in current use worldwide as well as running EXAMS 2.98.04).  Paul Hendley announced that an industry group will also be performing a review of EXPRESS.ORD is developing an implementation plan  </p>

<p>PE4V01.pl, a PRZM-EXAMS user shell designed to automate most of the process for single
scenario runs, is currently being used in EPA by OPP (See extensive discussion on the QA/QC process for this in the minutes for earlier EMWG meetings).</p>

</li>
<li><h3>Rice Tier 1 Model - Jim Breithaupt</h3>

<p>Jim Breithaupt was asked to do some incremental refinements of  the rice model.  He is using redox numbers and is incorporating some aerobic soil degradation and water degradation information.    The interim policy for initial estimation of upper bound exposure levels from the rice use is being improved but is still considered pre-Tier 1.  Also, better crop time lines are being used. </p>

</li>
<li><h3>Spray Drift Task Force - Norm Birchfield</h3>

<p>Norm Birchfield reported on a recent meeting between the Spray Drift Task Force (SDTF) and senior EPA people including lawyers on the AgDRIFT model.  Several issues are still in play:</p>

	<ol>
	<li><p>data compensation may be an issue if the use of the model were to take the 	place of spray drift data; risk managers are working on this issue with support 	from EFED;</p></li>

	<li><p>license agreement and transparency - many EPA people are still not 	comfortable with the license agreement; EPA prefers to make the model and code more 	freely available;</p></li>

	<li><p>future ownership of the model and how will improvements be entered; and </p>	</li>

	<li><p>the need to define which version of the model will be used; EPA does not 	think that version control is a pressing issue at this point since the model is not 	in common use.</p></li>

	</ol>

<p>Paul Hendley reported that version 2.08 compiles all the changes made since version 2.04 and includes full documentation of those changes.  The SDTF wants this version to be approved and then renumbered as version 2.10.  The version 2.10 would then form the basis for future development and agreement.  Norm Birchfield stated most AgDRIFT modeling is presently conducted with version 2.01 because this is the last version created under the EPA-USDA-SDTF CRADA.  Later versions have not been reviewed by the Agency.  Later versions, however, do not appear to be substantially different from 2.01.  EPA feels issues 1-3 are more important at the moment.      </p>

</li>
<li><h3>PLUS and CARES - Scott Jackson and Paul Hendley</h3>

<p>Scott Jackson indicated that there is nothing new on PLUS.  For CARES, they are looking at how to move daily water values into CARES.  This needs development of PLUS and a daily surface water model.  An industry  sub work group of CARES</p>

<p>has produced a white paper on how to move the data.  Using different methodologies, you can get daily output and link with CARES.  Betsy Behl asked to have regular updates on this CARES/modeling interface topic at future EMWG meetings.</p>

</li>
<li><h3>EFED Groundwater Team - Betsy Behl  </h3>

<p>Betsy Behl reported on the progress of the groundwater team and efforts to link with other groups outside OPP.  The team has reviewed the open literature and the FIFRA Enviromental Modeling Taskforce (a group which previous evaluated PRZM leaching performance using OPP-required Prospective Ground-Water Monitoring Studies to support pesticide registrations) output and will produce a report by December.  The next action will be to identify models and data sets and make recommendations about Tier 2 models.  Betsy Behl is hoping to report on their progress at the January meeting.</p>

</li>
<li><h3>EFED Fate Database - Michael Barrett</h3>

<p>Don Wauchope is going ahead with his interim database and needs to circulate his spreadsheet version.  Mah Shamim and Larry Liu will try to present their progress at the next meeting.</p>

</li>
<li><h3>Performance of PRZM - Russell Jones</h3>

<p>Russell Jones gave a presentation that will be attached to the minutes.  Larry Burn had asked after his presentation whether a more theoretical based approach that relates to sorption and degradation would be helpful.  Russell Jones replied that he supported a theoretical approach when information is available, but an empirical approach can also be used for laboratory measurements of aged sorption.</p>

</li>
<li><h3>FOCUS - Approach to Foliar Washoff and Dissipation in Surface Water Calculations - Piyush Singh</h3>

<p>Piyush Singh's presented an update on how FOCUS looks at foliar washoff and dissipation for surface water calculation.  His presentation will be posted with the minutes.    It was pointed out that there are differences in the way FOCUS and EPA handle these issues.  EPA participants confirmed the importance of selecting the right chemical application method (CAM) appropriate for a particular use pattern.  Betsy Behl agreed that this topic should be discussed at the next EMWG meeting.  </p>

</li>
<li><h3>Landscape Investigations for Pesticide Studies (LIPS) - Small Water Body (SWB) Study - Donna Randall, Ann Pitchford and Las Vegas ORD Team.</h3>

<p>Donna Randall explained that ORD is helping with the development of the Tier II Refined Risk Assessment model (PRZM/VVM).   ORD is using a RS/GIS approach to develop national, regional and scenario specific values for watershed size to pond volume.  Anne Pitchford reported that after the Mid-Atlantic monitoring program (1999 - 2004) , they will be monitoring between 100-150 small scale water bodies in the Midwest from 2001 - 2007 in collaboration with USGS and others.  In the future, they would like to monitor water bodies in  California (2002 - 2008)</p>

<p>Anne Pitchford described the Indiana pilot program that will be operational from 2003 - 2006.  The objective of this pilot study is to develop statistical distributions for model parameters to drive EXAMS.  The goal of the broad scale analysis is to assess large populations of surface water bodies (SWB's) using RS/GIS.  Then they will conduct surface water (SW) specific analyses to sample representative SWB's followed  by measurements of  diurnal, weekly, and monthly temporal changes in small water bodies (to be done at local universities through STAR grants).</p>

<p>The goal is to look at combining data from the National Wetlands Inventory with National Agricultural Statistics Service annual data at sites where SSURGO data exists along with previous National Water Quality Assessment (NAWQA) monitoring data from the US Geological Survey.  Given these criteria, they looked at the White River basin in Indiana.  They will be sampling four 8 digit HUC's using at least two levels of remote sensing resolution.  The objective is to identify the criteria needed for full census.  The four regions that were selected  represent a range of topographic relief and land-cover techniques.  The plan will result in an RS inspection of 10 - 12% of the basin.</p>

<p>During her presentation, Ann showed examples of 15 m Landsat thematic data and compared this with 30 m TM and 5 m CASI data.  In an earlier study, they looked at 5 m data to identify ponds in a flat area.  They used a 100 m buffer zone around each pond initially, but they may use LIDAR next season to better define small watersheds around static water bodies.</p>

<p>For the pilot study, they will identify 20-30 SWB's using RS/GIS (based on RS determined criteria to be agreed with OPP) and will visit each site for one day and evaluate the sampling method.  They will evaluate the runoff area and key pond parameters for EXAMS in sediment and water column.  The next steps include developing a peer-reviewed Research and Quality Assurance Plan.  The pilot program will run in the Summer of 2004 and then the final (full) study will occur in the Summer of 2005-2006.  </p>

</li>
<li><h3>WARP - Ron Parker</h3>

<p>Ron Parker provided an update on WARP.  </p>

<p>EFED has received Dunne overland flow model estimates for WARP were received from USGS
(for 6300 drinking water watersheds). Delineation of watersheds was difficult (problems with QA/QC), and there are plans to correct some of the data.  Christine Hartless announced that additional verification will be done, and they are finalizing a GIS tool to do this faster. Ron Parker then gave a brief background on WARP.  He explained that after the Food Quality Protection Act (FQPA) was passed, there was a need perform upper level refinements and estimate population-weighted concentration values for drinking water across the US. USGS had a regression model SPARROW which related concentration in surface water to characteristics of watersheds.  This model was originally used to evaluate nitrates.  EPA asked USGS to use the model to look at atrazine, and it worked well. This national-scale regression model methodology was presented to FIFRA SAP meetings at different stages of development on three occasions.  Then after the second SAP meeting, USGS suggested to EPA that the WARP model be used in place of SPARROW.  WARP has been developed from patterns observed in NAWQA monitored pesticide concentration data and provides predictive capabilities by performing a regression against predictors of watersheds that consist of widely available hydrologic, soil, and weather data.  WARP is a compilation of eight regression equations that provides 5th - 95th percentiles.  </p>

</li>
<li><h3>Variography and Kriging - Jim Hetrick/Jim Wolf</h3>

<p>Using 1994-2000 Heidelberg data (Maumee River data only), they demonstrated the differences in time course for different chemicals (atrazine, acetochlor, chlorpyrifos).  Tools included GEO-EAS and Geostatistical Software Library.    Jim Hetrick discussed a variogram approach to analyzing temporal data ( days 100 - 275 for each year).  As an example, he showed the atrazine data from the reservoir monitoring program that showed a range of about four days.  He takes a data set, identifies missing data and uses temporal structure (nearest neighbor approach) to re-estimate data sets in a Monte Carlo approach.  This approach requires a normal distribution so monitoring data sets require  transformation (natural log transforms and normal score).  This technique may be limited by violation of stationarity; also needs to be aware of trends in periodicity and systematic annual effects.</p>

<p>Initial runs for atrazine were done as untransformed but later results used normal score transformed data for atrazine and acetochlor and had a range of about 20 days.  No temporal relationships were determined for chlorpyrifos.  For some years, kriging approaches were useful but for others they were not.  This approach permits temporal correlation and estimates missing values.  However, the approach depends on the quality of the monitoring and does not recognize the underlying transport variables.  The approach will tend to underestimate high occurrence frequency events, and the time series is noisy.</p>

<p>They performed a stochastic simulation analysis of the six years mean time series for atrazine and the 1995 data for acetochlor.  Atrazine simulations looked good for imaging the time series, but acetochlor predictions were less useful.  More work will be required.  They are looking to reevaluate this approach with other data sets and to incorporate other variables such as rainfall distribution and flow rate into co-kriging.</p>

</li>
<li><h3>WARP and Climatic Time Series - Charlie Crawford/Skip Vecchia</h3>

<p>A set of 1800 watersheds should be delineated by the end of the year.  The remainder will be available after QA/QC.  </p>

<p>They used percentiles generated from annual WARP to transform raw concentrations to
approximate normality.  Then they linked with climatic data to explain seasonal variation in transformed concentrations.  Next they developed a time series model for generating residuals from the climatic model on a daily time step and finally reversed the WARP-transformation to obtain generated daily data.</p>

<p>Transformation to achieve approximate normality was achieved based on WARP generated
percentiles for 114 model validation stations.  They examined three methods: 3-parameter log-normal transformation, alternative transformation 1 and alternative transformation 2.  The 3-parameter log normal transformation provided a good fit for high percentiles but was a poor fit for lower percentiles.  Alternative 2, which shows S-shaped behavior, was better for lower percentiles.  Then they interpolated and areally averaged temperature and precipitation data on a monthly basis for each basin.  The monthly climatic data were used to model variation in the transformed concentrations for the model calibration stations (one model); station sin west was excluded because of data paucity.  A non-linear regression was performed; censored concentrations were handled using maximum likelihood (Tobit regression).  Low precipitation went with low values (concentration).  A model was developed to link atrazine data with temperature and precipitation using a seasonal temperature factor (61% atrazine variability was not explained).</p>

<p>No significant seasonality was found between station groups.  Variogram analyses suggested that noise was due to measurement error plus signal was related to drainage area and usage.  Final model fitted fairly well for atrazine and metolachlor.   Metribuzin had a highly censored data set which tended to amplify the variability.  </p>

<p><strong>Conclusions</strong></p>

	<ul>

	<li><p>seasonal variability in herbicide concentrations can be reproduced well 	using available monthly temperature and precipitation data</p></li>

	<li><p>use of more accurate precipitation data may also help</p></li>

	<li><p>easier to predict the annual mean rather that peak values; limits on upper 	bound predictions</p></li>

	<li><p>the proposed model only works well with <15% censored data sets</p></li>

	<li><p>obstacles remain given high censoring rates</p></li>
	
	</ul>

<p><strong>Questions</strong></p>

<p>Q.  Can this tool be used for predictions?</p>

<p>A.  Yes, this is the ultimate objective.</p>

<p>Q.  Would flow be a better variable?</p>

<p>A.  Flow may be a better explanatory variable for concentrations than precipitation, but flow is usually not available at most locations where you want to predict.</p>

<p>Q.  Is there an upper bound or can the predicted data exceed the measured?</p>

<p>A.  Yes, it can.  In some examples, simulated values were higher; no upper bounds</p>

<p>One issue is how to handle tails of distribution - extrapolation (extend relationships into tail).</p>

</li>
<li><h3>EUFRAM Project - T.S. Ramanarayanan</h3>

<p>Ingrid Sunzenauer provided a set of slides that describes the 2001 EUPRA workshop.  Ingrid Sunzenauer serves as EPA's link to the EUFRAM program and is on the EUFRAM steering committee.    EUFRAM has three parts: framework document (guidance, case studies), end-user testing, and strategic network.  </p>

<p>T.S. Ramanarayanan presented Andy Hart's slides on the EUFRAM program.  These slides will be posted on the EMWG Web site.   The ECOFRAM report serves as a starting point and data guidance for EUFRAM.</p>

</li>
<li><h3>Hybrid Model for Upper Tier FQPA Drinking Water Exposure Assessments - Ron
Parker</h3>

<p>The hybrid model approach is being developed by Ron Parker and George Sabbagh. This option for calculating daily pesticide concentration values combines the nine percentiles of the distribution of concentration values at each the drinking water intake sites calculated by the WARP model with daily values calculated by the pesticide fate and transport models now used by OPP. The hybrid assessment is done by performing simulations using both types of models at the same or nearby and then combining the output results. The main advantages of this procedure over other options are </p>

	<ol>

	<li><p>incorporation of application date(s) to provide the time factor needed
	for cumulative assessments</p></li>

	<li><p>capability to simulate daily concentration values of  pesticide parent 	compound along with correctly timed degradates the for cumulative assessments and	</p></li>

	<li><p>capability to better estimate pesticide concentration values at the upper 	end of the distribution (above the 95th percentile) which are not estimated by the 	WARP model and are a function of the environmental fate properties of the chemical.	</p></li>

	</ol>

<p> This approach requires input data for each type of model and involves several steps. For the example presented, both PRZM/EXAMS and SWAT simulations were run for multiple years at sites near to the WARP site and the daily EEC's are sorted and ranked for each year. Then concentration values for multiple years were generated from variations of the 9 WARP percentiles by using the mean and standard error of the WARP estimates.  Finally, values for each percentile were randomly generated for each year and a new set of daily EEC's was recalculated. This approach uses daily ratios of parent to degradate to generate sets of daily data for parent plus degradates. </p>

<p>To estimate higher percentiles than can be done by WARP, this approach calculates the ratio of 99.7th %ile values (annual maximum day) from PRZM/EXAMS to 95th percentile from
PRZM/EXAMS for each year - this ratio is then applied to the WARP 95th percentile to estimate a WARP 99.7th %ile.  In the example presented, this approach did better for parent atrazine than for the degradate desethyl atrazine. This may be due to the fact that a flow component was not included in the PRZM/EXAMS simulation. Of the three approaches described, this one appears to be the most attractive for handling cumulative assessments of multiple active ingredients and degradates and for estimating of peak annual values.</p>

<p>The result of the hybrid is multiple years of daily values for multiple chemicals including degradates at all US surface water intake locations for use in population-weighted cumulative/aggregate FQPA drinking water assessments.  </p>

</li>

</ol>

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<hr />

<h2 id="next">Next Meeting</h2>

<p>The next proposed meeting date is January 8th with the 7th or 6th as alternative dates.  Michael Barrett will confirm availability of Rm 1126 and circulate the final date ASAP.</p>

<p class="pagetop"><a href="#content">Top of page</a></p>
<hr />

<h2 id="actions">Action Items</h2>

<ol>

<li><p>Everyone will review old action items and complete before next meeting, particularly posting of presentations to Web site (Thuy Nguyen, Jerry Hannan, Don Wauchope, Gail, Gerry Laniak).</p></li>

<li><p>EFED will consider adding Tier 2 groundwater needs and conceptual model to January
meeting agenda.</p></li>

<li><p>Mark Cheplick will post details of suggested code changes in PRZM and slides showing impact of changes on the list server.</p></li>

<li><p>Michael Barrett or the new EMWG chair (new chairs are currently being elected for the Water Quality Technical Team in EPA-OPP Environmental Fate & Effects Division, one of the new WQTT chairs will be slated to take over the chair of EMWG) will schedule progress reports on the EFED research programs at the next meeting.</p></li>

<li><p>Don Wauchope will circulate an Excel spreadsheet of combined databases when available - end of the month.</p></li>

<li><p>Don Wauchope to post notice of ACS symposium on soil dissipation on Web site.  </p></li>

<li><p>Ron Parker to update FIFRA EMWG on progress of the FAO comparative model at the next meeting. </p></li>

<li><p>EFED will consider  presenting a demo of  the fate database at the next meeting.</p></li>

<li><p>After management approval, Michael Barrett or the new EMWG chair will add a discussion of the kinetics policy to the agenda of the next meeting.  </p></li>

<li><p>Industry representatives to present the findings of the FOCUS kinetics group at the same meeting.</p></li>

<li><p>All speakers to provide copies of their presentations to Michael Barrett for posting on Web site.</p></li>

<li><p>EPA to consider adding a presentation on internal work on foliar degradation, washoff and extraction factors as well as chemical application method factors for PRZM.</p></li>

<li><p>EPA to examine PLUS and CARES; industry to provide regular updates on
CARES/modeling interface topics at future meetings.</p></li>

<li><p>Michael Barrett to check availability or meeting room for next meeting and circulate final date on list server.</p></li>

</ol>

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