# Charge Questions presented by: Donna Randall1FIFRA SCIENTIFIC ADVISORY PANELConsultationOctober 25-26, 2011U.S. Environmental Protection AgencyOffice of Pesticide ProgramsWashington, DC

# Charge Question 1: IntroductionFocus: TERRA model’s attributes and the general capabilitiesnecessary for modeling pesticides used in urban settingsThe three most prevalent antimicrobial uses of copper include antifoulantpaints, roofing shingles and wood preservatives. The AntimicrobialsDivision used a basic field scale modeling approach, including maximumuse rates, realistic heavy rainfall events, the assumption of high leachingrates, and storm-water conveyance via impervious surfaces, to estimatepotential high end aquatic exposure from copper’s use as an antimicrobialpesticide in roofing shingles and treated wood. The American ChemistryCouncil (ACC) has proposed the TERRA Model as an alternative andmore refined way to assess aquatic exposure due to the two major urbanantimicrobial uses of copper, inwood preservatives and in roofingshingles, on a watershed scale level.

# Charge Question 1: (a) and (b)Focus: TERRA model’s attributes and the general capabilitiesnecessary for modeling pesticides used in urban settingsa)What does the Panel believe are the advantages and/or limitations ofassessing antimicrobial uses of copper from roofing shingles andwood preservatives with TERRA, a spatially-explicit, watershedscale model? Are there other models that the Panel feels should beconsidered for use by OPP in estimating exposure to copper from itsuse as an antimicrobial pesticide, specifically in roofing shingles andwood preservative?b)In the opinion of the Panel, what attributes of an urban watershedmodel are the most critical and why does the Panel regard theseattributes as critical? Does the TERRA model possess theseattributes?

# Charge Question 1: (c) and (d)Focus: TERRA model’s attributes and the general capabilitiesnecessary for modeling pesticides used in urban settingsc) Please discuss whether TERRA has the modeling capabilitiesnecessary for it to be applied to other urban metal exposureassessments for antimicrobial pesticides as well as whatmodifications, if any, would be needed to assess exposure to othermetals used as pesticides.d) In the opinion of the panel what further development and/orassessment is necessary to prepare the TERRA model for use as anexposure assessment tool by the EPA?

# Charge Question 2: IntroductionFocus: Goodwin Creek Watershed and the national application of thiswatershedEPA employs a tiered strategy to assess aquatic exposure. The first tierfacilitates the rapid screening of pesticide uses for potential risk issues, whilethe second tier refines exposure estimates by utilizing a field scale model andsite specific properties. This process is designed to incorporate additionaldata (e.g., site specific properties) for each progressive tier. EPA hashistorically employed field scale modelsto assess aquatic exposure in supportof national pesticide registrations. The TERRA model, unlike other modelsused by OPP, is a fully distributed, spatially-explicit watershed model. It hasmodel capabilities of distributing differences in hydrology, meteorology, soilproperties, and pesticide uses across a watershed. These model capabilitiesrequire consideration in terms of the proper scale of the exposure assessment.

# Charge Question 2: (a) and (b)Focus: Goodwin Creek Watershed and the national application of thiswatersheda)Are the appropriate pathways (e.g. engineered water conveyancestructures) for modeling urban antimicrobial uses of copper within theGoodwin Creek scenario currently included in the framework of theTERRA model? What, if any, additional pathways are necessary toappropriately assess exposure?b)What are the most important attributes to consider when selecting anddesigning an urban watershed modelingscenario? In the opinion ofthe Panel, where does the Goodwin creek watershed fall within adistribution of the nation’s urban watersheds? Also, given that themodel does not account for storm drains, how does this compare towatersheds nationwide?

# Charge Question 3: IntroductionFocus: CalibrationWatershed-scale models require calibration to account for complexwatershed-dependent hydrology and environmental fate processes. Modelcalibrations have been conducted by altering saturated hydraulicconductivity, Mannings N, soil erodibility factors, land cover factors, andchemical partitioning coefficients. Incontrast, the OPP field-scale modelssuch as PRZM/EXAMS are not calibrated for site-specific hydrology,etc.The TERRA model utilizes a simulated urban watershed that was calibratedto the hydrology and sediment loads of Goodwin Creek. Because theGoodwin Creek watershed is a predominately pastured/forested watershed,the EPA has concerns that the calibration processes may not adequatelyrepresent urban hydrologic and chemical transport processes.

# Charge Question 3: (a) and (b)Focus: Calibrationa)Please discuss the implications of watershed land use patterns onmodel calibration. What types of impacts could these have on theestimated exposure concentrations of copper?b)Please indicate any unique calibration issues that should be consideredwhen simulating an urban, residential watershed.8