# Consultation on the Two-dimensional Exposure Rainfall-Runoff Assessment (TERRA) Watershed Model and Its Use in the FIFRA Ecological Risk Assessment for Antimicrobial Uses of Copper1FIFRA SCIENTIFIC ADVISORY PANELConsultationOctober 25-26, 2011U.S. Environmental Protection AgencyOffice of Pesticide ProgramsWashington, DC

# EPA Review of the TERRA Model and the Goodwin Creek Scenario as Used in the Antimicrobial Copper Exposure Assessment Dr. Stephen Wente, EPAFIFRA SCIENTIFIC ADVISORY PANELConsultationOctober 25-26, 2011U.S. Environmental Protection AgencyOffice of Pesticide ProgramsWashington, DC2

# Presentation OutlinezEPA’s Review of the TERRA ModelzEPA’s Review of the Goodwin Creek ScenariozExposure Modeling for Antimicrobial Pesticides3

# EPA’s Review of TERRA Model4

# Features and Computational ResourceszFeatures of the TERRA modelFully-distributed watershed modelSmall time-step (1 minute or less) used within individual stormeventsCalibrated to site-specific datazComputational resource requirements are highExtensive GIS data requiredCalibration for site-specific scenarios requiredComputer processing requirements dependent on grid-cellresolution5zLarge grid-cell size (~90m) hinders representation ofengineered water conveyance structureszDesigned to move water away from homes quickly, avoiderosion, and be stable (impervious materials)zContinuous pathway for water from origin of flow towaterbodies of concernShingles to roof gutter to downspout to driveway to streetgutter to storm sewer to pond, stream or ditch6 

# Engineered Water Conveyance Systems

# Engineered Water Conveyance Systems

(cont.)zPrediction quality as urban characteristics increase:Water is more likely to be moved by engineered waterconveyance systemsTherefore, water movement is less related to grid-cell surfaceelevation and more related to finer-scale engineered waterconveyance systems7RuralUrbanSuburbanLess engineeredMore engineeredHydrologyzProportion of watershed inimpervious surfaceszConnectivity of imperviouspixelszArtificial dilution volume(runoff) contributed by largeimpervious pixels8 

# Spatial Resolution Issues90m pixel ~ 2 acres9 

# Proportion of Impervious SurfaceszAveraging propertiesacross grid-cells results infew truly impervious cellszFiner resolution:Reduces averaging acrossgrid-cellsMore accurate distributionof pervious and imperviouscells

# Grid-Cell Connectivity of Impervious SurfaceszContinuous impervious flowpathsAt 2 acres/grid-cell not manycontinuous flow paths could berepresented in watershedFiner resolution would allowmore flow paths10PondSource

# Dilution Water VolumezA 3-cell flow path at 90mresolution (green) occupies6 acreszA 9-cell flow path at 30mresolution (blue) occupies 2acreszFiner resolution reducesarea needed to representan impervious flow path11PondSource

# Resolution and Landscape IssueszNeed finer resolution for:Proportion and distribution of pervious/impervious surfacesConnectivity of impervious surfacesReduction of artificial dilution volumesRepresenting a variety of landscapeszRequires additional computational resourceszFewer impervious flow paths would:Result in more copper infiltration in soilLower predicted copper concentrationszQuestion: Does a lower grid-cell resolution necessarilyproduce lower copper concentrations?12

# EPA’s Review of the Goodwin Creek Scenario13

# How Does Goodwin Creek Compare to Other Watersheds across the US?14WatershedCharacteristicActualSimulatedLand Use60% pasture and25% forest89% Residential and9% open spaceAverage AnnualRainfall55.4 inches62 inchesRunoff Capacity71% C soilCN 71-86Residential (1/8 -1/2)CN 80-90

# Factors Affecting Model-Predicted Estimated Environmental Concentrations15zModel estimate location:watershed terminus vs. loworder streamszLocation of residential structuresand density relative to waterbodieszVegetative buffer configurationzStorm sewersWatershed AreaStream ChannelsMonitoring Stations

# Hydrology Calibration MethodszCalibration based on:Pastured/forested watershed hydrology andSediment load datazApplied to a suburban scenariozQuestion: Are any additional calibration stepsnecessary?16

# Comparison of Model PredictionsModelShinglesTreated WoodEPA Impervious23 μg/L333 μg/LEPA PerviousND μg/L2.2 μg/LTERRA7.1 μg/L16.7 μg/L17zPervious vs. impervious surfaceszQuestion: Does the 90m-resolution TERRA model with theGoodwin Creek scenario produce realistic “high-end”exposure estimates?Dissolve Cu Concentration (ug/L)0 5 10 15 20 25 30

Cumulative Probability0.00.20.40.60.81.0 EPA Impervious

TERRA

EPA Pervious 

# Shingle Model Predictions Compared to USGS Urban Site Dissolved Copper Concentrations18

# Wood Treatment Model Predictions Compared to USGS Urban Site Dissolved Copper

Concentrations19

# Exposure Modeling for Antimicrobial Pesticides20

# Antimicrobial Use Patterns1.Agricultural Premises andEquipment2.Food Handling/StorageEstablishments, Premises, andEquipment3.Commercial, Institutional andIndustrial Premises, andEquipment4.Residential and Public AccessPremises5.Medical Premises andEquipment6.Human Drinking WaterSystems7.Materials Preservatives8.Industrial Processes and WaterSystems9.Antifouling coatings10.Wood Preservatives11.Swimming Pools12.Aquatic Areas21

# Antimicrobial Models: What We HavezMany antimicrobial pesticides tend to enter the aquaticenvironment indirectly via wastewater treatment plant effluentsor from end-uses that lead to direct contact with surface waterzIn addition to OPP-wide models, AD utilizes:E-FAST: Exposure and Fate Assessment Screening Tool•DtD: Down-the-Drain•PDM: Probabilistic Dilution ModelMAM-PEC: Marine Antifoulant Model to Predict EnvironmentalConcentrationsPRZM/EXAMS22

# Antimicrobial Models: What We NeedzAntimicrobials Division is in need of models that canfully characterize surface water exposure fromantimicrobial pesticides with land uses. Looking formodel(s) with ability to:Model environmental exposure fromresidentialuses oftreated wood, 

# i.e.roofing shingles, fences and utility polesModel sporadicruraluses of antimicrobial woodpreservatives, 

# i.e.railroad ties, fences and utility poles23

# Antimicrobial Models: What We Need

(continued)zIdeally, model(s) would include scenarios specific to usepatterns of antimicrobial pesticides. These would account for:Loading from leaching (continuousover the lifetime of the treatedarticle)Variety of runoff pathways from use site including•Direct and indirect runoff to surface water•Degrees of interception of runoff across pervious and impervioussurfaces (rural to urban landscapes)•Interception by water conveyance structuresVariety and density of structures treated with antimicrobialpesticides2425 

# Questions