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1 1

2 

# Guidance on Modeling Offsite Deposition of 3



# Pesticides V i a Spray Drift for Ecological and 4 

# Drinking Water Assessments 5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20



## Katrina White, Ph.D.

, Faruque Khan, Ph.D.

, 21



## Charles Peck, Mark Corbin , M.S. 22

23



## Environmental Fate and Effects Division 24



## Office of Pesticide Programs 25



## U

. S

. Environmental Protection Agency 26

27

28

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2 ACKNOWLEDGEMENTS 29

30

The authors would like to acknowledge the input from two key former EFED workgroups, the 31

Endangered Species R egistration Review Workgroup and Litigation Steering Committee

. 32

Additionally, this document was reviewed by representatives of other technical teams in EFED

, 33

including Kristina Garber, Nicholas Mastrota, Gabe Rothman, Michael Davy, and Greg Orrick. 34

35

36

37

38

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3 Table of Contents 39

40

1. Purpose of Guidance

................................ ................................ ................................ ............. 4 41

2. Offsite Deposition of Pesticides and Spray Drift Distance

................................ ................ 4 42

2.1. Initial Inputs/Setup for AgDRIFT for Terrestrial and Aquatic Assessments

.................. 5 43

2.2. Modeling Exposure to Terrestrial Organisms Off the Field

................................ ........... 7 44

2.2.a Estimating Exposure off the Field

................................ ................................ .............. 7 45

2.2.b Estimating the Terrestrial Spray Drift Distance

................................ .......................... 7 46

2.3. Modeling Exposure to Aquatic Organisms Off the Field

................................ ................ 9 47

2.3.a Estimating the Aquatic Spray Drift Fraction for Use in PRZM/EXAM S at a 48

Specified Distance from the Edge of the Field

................................ ................................ ..... 10 49

2.3.b Estimating the Aquatic Spray Drift Distance

................................ ............................ 12 50

2.4. Reporting on Modeling Procedures, Results, and Uncertainties

................................ . 16 51

52

List of Appendices 53

54

Appendix A. Comparison of Results from Tier I, Tier II, and Tier III AgDRIFT Analysis U sing 55

the ASAE V ery F ine to F ine DSD and Fine to Medium DSD

............................... 18 56

Appendix B. How to Determine the Aquatic and Terrestrial Spray Drift Fraction for an 57

App lication Rate in AgDRIFT for Ecological Assessments

................................ .. 21 58

Appendix C. Calculation of the Spray Drift Fraction for Drinking Water Assessments Using the 59

Index Reservoir.

................................ ................................ ................................ ..... 27 60

Appendix D. Example and Validation of Terrestrial Spray Drift Distance Approach

................ 29 61

62

63

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4 1. 

# Purpose of Guidance 64

65

During the application of pesticide s

, a n appreciable amount of applied chemical can drift beyond 66

the intended target site to non

- target receptors and their habitats or surface water sources

. The 67

purpose of this document is to provide guidance on modeling offsite deposition of pesticides 68

through spray drift for ecological and drinking water assessments

. Additionally, this guidance 69

provide s standard default assumptions for quantifying pesticide deposition from spray drift to 70

terrestrial and aquatic environments and information on the characterization of spray drift buffers 71

used to mitigate identified risks for non

- listed species

. The A genc y is in the process of 72

evaluating its approach for assessing offsi te deposition impacts to listed species , given the 73

recommendations outlined in the recent National Academy of Sciences publication “ Assessing 74

Risks to Endangered and Threatened Species from Pesticides ” (NAS, 2013)

. Once the A gency, 75

the Fish and Wildlife Service, and National Marine Fisheries Service agree on a common 76

approach for the ecological risk assessment process for listed species

, this document will be 77

revised accordingly. This docum ent does not provide guidance regarding off

- site transport 78

through other mechanisms such as vapor drift, wet and dry deposition, long

- range transport

, as 79

well as surface water runoff and downstream movement of a compound

. 80

2. 

# Offsite Deposition of Pesticides a nd Spray Drift Distance 81

82

Exposure to spray drift is assessed for agricultural and residential spray applications of liquid 83

formulations, except for applications with hand held or back pack sprayers. EFED does not 84

currently have a method to quantify spray drift from other application methods and materials 85

such as applications of dry materials

, drip chemigation , and for applications with hand held or 86

back pack sprayers ; therefore, spray drift is assumed to be negligible

. AgDRIFT 1 

### can be used to 87

model spray drift in the following ways : 88

89

• E stimate the spray drift fraction for inputs into PRZM/EXAMS for estimating aquatic 90

exposure in drinking water and ecological risk assessments 91

• E stimate exposure of plants to spray drift in ecological risk assessments 92

• E stimate the fraction of applied pesticide , used in assessing exposure for terrestrial organisms 93

located off the application site

, including for applications directly to water 94

• D etermine the maximum distance from the edge of the area where the pesticide is directly 95

applied (also known as the initial area of concern ) to the point where levels of concern 96

( LOCs ) are no longer exceeded for both terrestrial and aquatic organisms

. 97

98

In addition to AgDRIFT, the following models may be needed to estimate spray dr ift distances 99

for terrestrial and aquatic organisms: 100

101

• Terrestrial Residue Exposure model (T

- REX) 2 

### 102

1 Spray Drift Task Force Spray Software. AgDRIFT ( Version 2. 1. 1 ). Available at G: \ Models_Repository \ AgDRIFT

2 USEPA 2008. Terrestrial Residue Exposure Model. Available at

http://www.epa.gov/oppefed1/models/terrestrial/trex/t_rex_user_guide.htm

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5 • Terrestrial Herpetofaunal Exposure Residue Program Simulation (T

- HERPS) 3 

### to estimate the 103

spray drift distance for terrestrial organisms 104

• Pesticide Root Zon e Model (PRZM) 4 

### and the Exposure Analysis Modeling System 105

(EXAMS) 5 

### 106

107

Spray drift distances are distances from the edge of the field where LOCs may be exceeded and 108

they are important in determining possible options for mitigating risk. For screening level 109

assessments, spray drift analysis should be limited to the Tier I module in AgDRIFT unless the 110

label specifies certain application parameters to limit spray drift potential. For example, use of a 111

helicopter or applications at wind spee ds of 15 mph would require use of Tier II or III modeling 112

in AgDRIFT. Tier II and III modules are only ava ilable for aerial applications

. Tier II and II I 113

module s allow the user to modify many variables pertinent to spray drift to make the scenario 114

more re presentative. 6 

### In general, Tier II and III modules are used for refining geographic extent 115

of risk and mitigating risk. The assessor may consider using both the Tier II and III modules in 116

AgDRIFT on a case

- by

- case basis. The maximum spray drift distance using Tier I and II 117

analys e s is 997 feet and the maximum spray drift distance using Tier III analysis is 2608 feet. 118

Aquatic and terrestrial assessment results for Tier II and III analyses are similar to the results 119

from Tier I analysis with the ASAE (Am erican Society of Agricultural Engineer s ) 7 

### V ery F ine to 120

F ine drop size distribution (DSD) across a range of target deposition values (Appendix A). Tier 121

II and III analyses will require justification when using input parameters that deviate from the 122

default parameters. T he AgDRIFT module for modeling multiple applications should not be 123

used

. 8 

### Consult the Fate Tech Team and Water Quality Tech Team for guidance on modeling 124

ultra low volu me (ULV) applications 9



### . 125

2.1. 

## Initial Inputs/Setup for AgDRIFT for Terrestrial and Aquatic 126



## Assessments 127

128

• Open AgDRIFT and choose the appropriate Tier for your assessment. 129

• Unless parameters are specified on the label, select the appropriate default input para meters 130

3 USEPA 200 8. Terrestrial Herpetofaunal Exposure Residue Program Simulation. Available at

http://www.epa.gov/oppefed1/models/terrestrial/therps/t_herps_user_guide.htm

4 USEPA 2006. Pesticide Root Zone Model. Available at http://www.epa.gov/oppefed1/models/water/# przm

5 USEPA 2005. Exposure Analysis Modeling System. Available at

http://www.epa.gov/ceampubl/swater/exams/index.html

6 Tier II allows the user to modify drop size distribution (DSD), nonvolatile application rate, active application rate,

spray applicat ion rate, carrier type (water or oil), wind speed, temperature, relative humidity, aircraft type, boom

length, boom height, number of swaths, swath width, and swath displacement. The Tier III module allows the user

to access all model inputs including the Spray Drift Task Force (SDTF) spray materials evaporation library, wind

direction, the SDTF aircraft library, nozzle positioning, surface roughness, and access to the Spray Block Statistics

calculator for inferring swath width, Coefficient of Variation (C OV), and mean deposition within the spray block for

input conditions specified to the model.

7 ASAE has been replaced by the American Society of Agricultural and Biological Engineers (ASABE); however,

AgDRIFT is still using the ASAE abbreviation. In the f uture, labels may list ASABE standards rather than ASAE.

8 Note that PRZM/EXAMs will assume spray drift with each application, and multiple applications are also

considered in T

- REX to arrive at the target fraction of applied. So while EFED does not use t his module, exposure

to multiple spray drift events is considered in the risk assessment.

9 An ultra low volume application is a method of dispensing liquid pesticides at the rate of one half gallon or less per

acre.

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6 as shown below. 131

132

Agricultural, Golf Courses, and Residential Scenarios 133

134

a. Tier I Ground Applic ations: high boom height 10 

### , ASAE V ery F ine to F ine D rop Size 135

D istribution (DSD) , a 90 th 

### percentile data percentile, do not a ccess extended 136

settings 137

b. Tier I Aerial Application: u se ASAE Fine to Medium DSD 11 

### 138

c. Tier I Orchard/Airblast: Sparse (Young/Dormant) 12 

### : do not access extended settings 139

140

• Click on Toolbox and choose aquatic assessment for the aquatic environment or terrestrial 141

assessment for the terrest rial environment. 142

143

Current d efault assumptions for aerial applications in AgDRIFT include the following: 144

• a wind speed of 10 mph, 145

• 60

- foot swath width, 146

• release height of 10 feet, 147

• b oom l ength: 76.3 % , and 148

• s wath d isplacement d efinition: f raction of s wath w idth 0.3702

. 149

150

If the label specifies that aerial application parameters beyond Tier I may occur ( e.g

. , higher 151

wind speeds or release heights) , use Tier II or Tier III, whichever is applicable. I f these best 152

management practices are not followed and are not on the label, spray drift may be greater than 153

that predicted using default input parameters and Tier I analysis

. This information should be 154

include d in the risk assessment. If the evidence indicates that applications will likely not be 155

consistent with the default assumptions (for example, the ASAE Fine to Medium DSD) , the 156

expected application parameters should be modeled in AgDRIFT. 157

158

Generally, a ny changes made to the se initial input parameters sho uld be based on enforceable 159

statements on labels. When a buffer distance is specified on a label, the number is placed in the 160

“Distance to Water Body from Edge of Field” in the AgDRIFT aquatic or terrestrial assessment 161

screen to estimate the spray drift f raction for inputs into PRZM/EXAM S or inputs into T

- REX if 162

assessing risk off the field ( e.g ., for an aquatic application)

. If different labels have different use 163

restrictions, ensure that the input parameter(s) modeled is the most conservative ( e.g ., res ults in 164

the highest percentage of spray drift or longest spray drift distance) or show the range that is 165

representative of all labeled directions. 166

10 In AgDRIFT, a low boom is 0.508 m or 20 inches in height and a high boom is 1.27 m or 50 inches in height. The

assumed swath width is 45 ft.

11 The Very Fine to Fine DSD results in higher spray drift deposition than the ASAE Fine to Medium DSD

assumption. If evidence is available indicating that the Very Fine to Fine DSD is likely to be used and it is allowed

on the label, this DSD may be modeled instead of the ASAE Fine to Medium DSD.

12 The orchard/airblast provides an estimate of the 50 th percentile of drift. The empirical data supporting the

development of airblast exposure was very limited

, and a 90 th percentile estimate is not available at this time.

Therefore, the orchard airblast exposure estimate is not an upper bound exposure esti mate. Use of other

orchard/airblast modules should be used carefully since the current estimate of exposure may not be conservative.

EFED plans on developing a methodology to provide a conservative exposure estimate for airblast uses in the future.

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7 2.2. 

## Modeling Exposure to Terrestr ial Organisms O ff the Field 167

2.2.a 

## Estimating Exposure off the Field 168

169

T

- REX estimate s exposures to terrestrial animals from residues on potential food items found at 170

the site of application ( i.e ., on the field) . For determining potential risk to terrestrial animals 171

from dietary exposure off the site of application ( e.g ., including for applications made directly to 172

water)

, T

- REX can be used in conjunction with spray drift models ( e.g ., AgDRIFT). For 173

terrestrial animals, under Terrestrial Assessment in AgDRIFT

, select Point Deposition and input 174

the buffer distance specified on the label under “Distance To Point or Area From Edge of Field

. ” 175

The “ Fraction of Applied ” for ground and aerial applications will give you the fraction of the 176

application rate that organisms will be exposed to at the specified distance. Multiply the 177

application ra te by the F raction of A pplied for aerial and ground applications and use the product 178

of the two as the input for the application rate in T

- REX. For applications directly to water, T

179

REX will be used to assess risk to terrestrial animals based on the conse rvative assumption that 180

exposure at the edge of the field will be iden tical to exposure on the water body . For bare 181

ground applications, use T

- REX to estimate exposure on the field and explain that the EECs for 182

seeds and insects reflect exposure on the fi eld and exposure to residues on plants

, which will 183

mainly occur at the edge of the field. 184

185

TerrPlant 13 

### estimates exposure to plants adjacent to the site of application

. The next section 186

discusses how to estimate a d istance from the edge of the field wher e terrestrial plants may be 187

exposed to spray drift at levels that could result in a Level of Concern (LOC) exceedance ( e.g ., a 188

spray drift distance). 189

2.2.b 

## Estimating the Terrestrial Spray Drift Distance 190

191

Below are instructions for calculating a spray drift dist ance or the distance from the edge of the 192

field where LOCs may be exceeded for terrestrial organisms. All spray drift distances should be 193

rounded to a whole number. 194

195

Terrestrial Animals: Calculate the target 14 

### “Fraction of Applied” 15 

### for terrestrial animals based 196

on risk quotients that are generated using T

- REX or T

- HERPS, acute and chronic terrestrial 197

animal endpoints

, and the appropriate LOCs. Risk quotients should be calculated using the 198

maximum application rate and the maximum num ber of applications. 16 

### For sublethal effects 199

endpoints, the LOC is not established for acute sublethal effects and is assumed to be one in the 200

13 USEPA 2009. TerrPlant. Available at http://www.epa.gov/oppefed1/models/terrestrial/

14 The target refers to that “fraction of applied” that will result in RQs being below LOCs.

15



### Quotient Risk Concern of Level Applied of Fraction Target ns Applicatio Ground and Aerial 

### =

0.5

Quotient Risk Concern of Level Applied of Fraction Target ns Applicatio Airblast × 

### =

16 While conceptually this ca lculation results in combining an RQ based on multiple applications in T

- REX with a

single exposure event for spray drift, the resulting spray drift distance will mitigate risk for both a single application

and multiple applications. See Appendix D for validation of this approach.

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8 calculation of the target Fract i on of Applied as specified in Footnote 15

. 17 

### Under Terrestrial 201

Assessment

, select Point Deposition and input the target Fraction of Applied. Click on “Calc

. ” 202

Figure 1 shows an example calculation. Inputs are “Point Deposition” and the “Fraction of 203

Applied

. ” The output is the “Distance to Point or Area Average from Edge of Field

, ” and it 204

represents the terrestrial spray drift distance. In Figure 1 , the spray drift distance is 26 feet. 205

206

207

208

Figure 1

. Example calculation of the terrestrial spray drift distance using the target 209

“Fraction of Applied” as the input for a ground application. The input s are “P oint 210

D eposition ” and the “Fraction of Applied

. ” The output is the “Distance to Point or Area 211

Average from Edge of Field

, ” and it represents the terrestrial spray drift distance. In this 212

calculation, the spray drift distance is 26 feet. 213

214

Terrestrial Plants: Under Terrestrial Assessment, select “Point Deposition

, ” input the maximum 215

single application rate in pounds active ingredient per acre into the “Active Rate” and the 216

appropriate toxicity endpoint into “lb/ ac” under “Initial Average Deposition” for ground and 217

aerial applications and click on “Calc

. ” Figure 2 is a screenshot from AgDRIFT using this 218

method. This assessment does not consider spray drift deposition from multiple applications. 219

17 This calculation applies to sublethal effects that do not have a corresponding LOC, such as acute sublethal effects.

Ther e are some chronic growth and reproductive endpoints for which the chronic LOC of one is commonly used.

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9 The EC 25 

### values for the most sensitive tested monocot and dicot species from either seedling 220

emergence or vegetative vigor tests are used to define the toxicity of the pesticide for non

- listed 221

species

. 222

223

224

Figure 2

. Example calculation o f the terrestrial spray drift distance using the “Active 225

Rate” and “Initial Average Deposition” in “lb/ac” as the input. The output is the “Distance 226

to Point or Area Average from Edge of Field

, ” and it represents the terrestrial spray drift 227

distance. In this calculation, the spray drift distance is 26 feet. 228

229

2.3. 

## Modeling Exposure to Aquatic Organisms Off the Field 230

231

Aquatic model s cenarios run without spray drift represent aq uatic concentrations due to run off 232

only, e.g ., assuming no drift due to spray drift b uffer setback. Comparing concentrations with 233

and without drift gives an estimate of the contribution of drift to aquatic concentrations and 234

information on whether a buffer may be used to mitigate risk to aquatic organisms. The relative 235

importance of runo ff and drift in PRZM/EXAM S scenarios is dependent on application 236

parameters, the climatic conditions of the scenario and the timing of application. Table 1 237

provides an example of the percentage of the exposure estimates due to spray drift for one 238

chemical for a set of California sites . Run off accounted for a wide range of the total estimated 239

environmental concentrations (EEC). For example, run off accounted for a high percentage of 240

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10 the EEC in the forestry and nursery scenarios (71

– 9 8%) and a very low pe rcentage of the EEC 241

for the fruit and melon scenarios (2

– 12%)

. 242

243

Table 1. Estimated a mount of the EEC that is d ue to r unoff ( t he h igher the p ercentage the 244

l ess the EEC was influenced by s pray d rift)* 245

Scenario Runoff

- only (EECs) / Runoff plus Drift EECs (Percent)

Peak 21 Day 60 Day

CAnurserySTD 98% 90% 85%

CAColeCropRLF 81% 52% 44%

CAcotton_WirrigSTD 66% 38% 32%

CAtomato_WirrigSTD 30% 11% 9%

CA almond WirrigSTD 26% 17% 20%

CAfruit_WirrigSTD 12% 6% 5%

CAMelonsRLF 6% 3% 2%

*A ll model runs involved the same compound and same input parameters, except for spray drift. When drift was 

### 246

included in the scenario

, the drift fraction was assumed to be 0.01 or 0.05, depending on whether an aerial or ground 

### 247

application was modeled. These percentages would be different if these default values were not used. 

### 248

249

One important caveat for this analysis is that the spray drift analysis should also include an 250

evaluation of the most sensitive toxicological endpoint. Even for scenarios where runoff 251

contributes substantially to an EEC , a highly sensitive taxa with a low toxicity endpoint ( e.g

., 252

having a high toxicity) could yield a large spray drift buffer for mitigat ing exposure to spray 253

drift

. The aquatic spray drift distance could result in a greater spray dr ift distance than the 254

terrestrial spray drift distance. Therefore, if LOCs are exceeded

, a spray drift distance may be 255

calculated regardless of whether runoff or spray drift are driving aquatic EECs. 256

257

In general, buffers that are vegetated and well main tained to prevent channelized flow have been 258

shown to be best for reduc ing pesticide loading. The document titled “ Conservation Buffers to 259

Reduce Pesticide Losses ” describes how to maintain buffers in a manner to prevent concentrated 260

flow and to maxim ize pesticide trapping (USDA, 2000). T he Agency does not currently have an 261

approved tool to model the impact of various buffer distances and types on runoff loading. If 262

channelized flow occurs in buffers, pesticide loadings in runoff to a water body can be 263

s ignificant. Additionally, many agricultural areas and golf courses have installed drainage that 264

flows directly into water bodies (Wright and Sa nds 2001; Haith and Rossi 2003). 265

2.3.a 

## Estimating the Aquatic Spray Drift Fraction **for Use in PRZM/EXAM S**  266



## at a Specified Distance from the Edge of the Field 267

268

When estimating aquatic exposure using PRZM/EXAMS, e stimate the spray drift fraction using 269

AgDRIFT

, starting with deposition at zero feet from the edge of the field . For ecological risk 270

assessments, the “EPA Defined Pond” is used as the water body in AgDRIFT. Appendix B 271

provides instructions for estimating the spray drift fraction using AgDRIFT and provides tables 272

of the spray drift fraction for different distances for the “EPA Defined Pond,” which is used to 273

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11 estimate aquatic exposure in ecological risk assessments. For drinking water assessments, the 274

spray drift fraction is calculated as specified in Appendix C

. 18 

### The Application Efficiency is 275

0.95 for all aerial applications and 0.99 for all ground a pplications

, including orchard airblast 276

applications, regardless of the spray drift fraction. 19 

### For granular applications and other 277

applications methods , EFED assumes negligible drift ; therefore, the spray drift and application 278

efficiency should be set to 0.00 and 1.0

, respectively

. Table 2 provides example spray drift 279

inputs at zero f ee t from the edge of the field using AgDRIFT Tier I default assumptions

. All 280

other input parameters should follow the Guidance for Selecting Input Parameters in Modeling 281

the Environmental Fate and Transport of Pesticides 20



### . 282

283

Table 2. PRZM/EXAMS Default and Additional Inputs for Percent of Spray Drift for 284

Applications of Liquids w ithout Any Spray Drift Limitations (Estimated U sing AgDRIFT 285

Version 2. 1. 1 ) 286

Type of Application Drop Size Distribution (DSD) Percent of Spray Drift for Runoff

and Drift EEC w ithout Buffer d

Ecological Risk Assessment Using EPA Farm Pond

Aerial V ery F ine to F ine 24.2

Fine to M edium (default) c 12. 5

Medium to Coarse 8.9

Coarse to Very Coarse 6.8

Ground (High boom) 1 Very F ine to F ine (default) c 6.2

Ground (Low boom) 1 Very F ine to F ine 2.7

Ground (High boom) 1 Fine to Medium/Coarse 1.7

Ground (Low boom) 1 Fine to Medium /Coarse 1.1

Airblast (Sparse: young , dormant) Aerosol to Very Fine c 4.2 a

Airblast ( D ense) Aerosol to Very Fine 1.5 b

Airblast (Vineyard) Aerosol to Very Fine 0.2 b

Airblast (Orchard) Aerosol to Very Fine 2.2 b

Drinking Water Assessments Using Index Reservoir b

Aerial V ery F ine to F ine 25.8

Fine to M edium (default) c 13.5

Medium to Coarse 9.7

Coarse to Very Coarse 7.6

Ground (High boom) Very F ine to F ine (default) c 6.6

Ground (Low boom) Very F ine to F ine 2.7

Ground (High boom) Fine to Medium/Coarse 1.7

Ground (Low boom) Fine to Medium/Coarse 1.1

Airblast (Sparse: young , dormant) Aerosol to Very Fine c 4.8 b

Airblast ( D ense) Aerosol to Very Fine 1.7 b

Airblast (Vineyard) Aerosol to Very Fine 0.3

Airblast (Orchard) Aerosol to Very Fine 2.5

a This is a 50 th percentile drift estimate and is not a conservative (high

- end) estimate of possible exposure. 

### 287

b Estimated using calculations shown in Appendix C. 

### 288

18 An example of these calculations is shown in Appendix C for 15 mph wind speeds, a limitation commonly

observed on labels.

19 The spray drift fraction is a fraction of the application rate, while the application efficiency is the fraction of the

total applied that reaches the field. These fractions are not expected to sum to a value of one.

20 U.S. EPA 2009. Guidance for Selecti ng Input Parameters in Modeling the Environmental Fate and Transport of

Pesticides . Version 2.1 October 22, 2009. Environmental Fate and Effects Division. Office of Pesticide Programs.

Available at: http://www.epa.gov/oppefed1/models/water/input_param eter_guidance.htm

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12 c This is a default input for estimating exposure in the Environmental Fate and Effects Division. The defaul t is used 

### 289

in exposure modeling unless there is a reason to deviate from the default assumption. 

### 290

d These defaults are based on the current model of AgDRIFT 2.1.1. These defaults should be updated as the model 

### 291

is updated. 

### 292

293

2.3.b 

## Estimating the Aquatic Spray Drift **Distance** 294

295

The following steps explain how to determine whether spray drift is an important component of 296

the estimated aquatic exposure and how a spray drift distance is estimated for aquatic organisms. 297

298

1. Determine PRZM/EXAMS EECs with drift fractions

, as described in Section 2.3.a

. 299

300

2. Determine whether to estimate a spray drift distance. Figure 3 is a flow chart that gives an 301

overview of when to determine the aquatic spray drift distance. The following points should 302

be considered: 303

304

a. If the PRZM/EXAMS EEC r esulting from both runoff and drift does not result in aquatic 305

LOC exceedances

, then no additional spray drift analysis is needed. 306

307

b. If there are LOC exceedances, determine PRZM/EXAMS EECs without drift ( e.g ., the 308

spray drift efficiency is set to 0). If the runoff only EEC from PRZM/EXAMS results in 309

LOC exceedances

, reducing spray drift will not mitigate the risk as estimated by 310

PRZM/EXAM S

. When discussing the impact of a spray drift buffer to the risk manager, 311

indicate that while a spray drift buffer wi ll not mitigate risk it will reduce risk. E stimate a 312

spray drift distance looking at exposure to spray drift alone using AgDRIFT and only 313

considering acute risk as specified in Section 4 a on Page 16

. This analysis provides 314

information on whether acute ex posure to spray drift alone could result in risk. 315

316

c. If there are LOC exceedances when both runoff and spray drift are considered and no 317

LOC exceedances for runoff only EECs , estimate a spray drift distance, as described in 318

Section 4 b on Page 17

, using AgDRIFT and PRZM/EXAM S

. Also estimate a spray drift 319

distance looking at exposure to spray drift alone

, using AgDRIFT and only considering 320

acute risk as described in Section 4 a on Page 16

. This analysis provides information on 321

whether acute exposure to sp ray drift alone could result in risk. 322

323

324

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13 325

326

Figure 3 . Flow Chart on When to Determine the Aquatic Spray Drift Distance 327

328

329

330 Determine PRZM/EXAMs

EECs without drift a. Do not calculate a

spray drift distance

because there is no risk

c. Calculate a spray drift distance

that considers risk due to exposure

to both runoff and spray drift as

described in Section 4b on Page

17. Estimate a spray drift distance

as described in Section 4a on Page

16. Runoff only EEC does not result

in LOC exceedance, but the EEC

that considers both drift and

runoff does result in an LOC

exceeda nce No LOC Exceedance

Runoff Only EEC

Results in LOC exceedance

b. Risk cannot be mitigated using

a spray drift buffer; however, any

buffer used will help reduce risk.

Estimate a spray drift distance

using Section 4a on Page 16. Determine PR ZM/EXAMS EECS

with Drift

Calculate RQs and

Compare to LOCs

LOC Exceedance

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14 3. When appropriate, c alculate the ratio of runoff

- only EEC to the runoff plus drift EEC. A 331

qualitative evaluation of the relative importance of drift to total loading can be made

, but no 332

quantitative criteria exist to determine how important drift is for a given chemical and use 333

setting. 334

335

Fraction of EEC due to Run off = Runoff

- only EEC / Runoff plus Drift EEC 336

337

This inf ormation may be used in the characterization of exposure and in explaining the results. 338

339

4. An aquatic spray drift distance may be calculated by only considering spray drift and acute 340

exposure using AgDRIFT

, described under Section a below and by considerin g acute and 341

chronic exposure to both runoff and spray drift using PRZM/EXAMS and AgDRIFT 342

(described under Section b below )

. 343

344

a. To calculate the aquatic spray drift distance that considers only exposure to spray drift 345

from a single application and acute risk to aquatic organisms

, run AgDRIFT as described 346

in Section 2 .1. Under the “T oolbox ” menu

, choose “A quatic A ssessment

. ” Select “ EPA

347

Defined Pond ” and input the target “Initial Average Concentration

. ” The initial average 348

concentra tion is defined by AgD RIFT as “t he average concentration within a defined 349

water body, in nanograms per liter or parts per trillion.” Therefore, the input for initial 350

average concentration is the concentration in water that will not result in an LOC 351

exceedance. Figure 4 shows the inputs and outputs in AgDRIFT. 352

353

Aquatic Animals : 354

Target initiation average concentration = LC 50 

### × LOC 355

Aquatic plants: 356

Target i nitial average concentration = EC 50 

### ( for non

- listed plants ) 357

358

The following is an example of spray drift distance calculations considering 359

exposure spray drift only ( e.g ., excluding runoff) from a single application. The 360

example would apply to a label that specified use o f a very fine to fine DSD. 361

362

Tier I, Aerial Application, V ery F ine to F ine DSD 363

Application Rate = 0.25 lbs a.i./A 364

Non

- l isted Species LOC = 0.5 365

LC 50 

### = 4 μg/L 366

367

Estimated spray drift d istance for an aquatic animal based on spray d rift only 368

369

Initial Average Concentration = LC 50 

### × LOC 370

= 4 μ g/L × 0.5 = 2 μ g/L or 2 00 0 ng/L 371

372

The estimated spray drift distance is 105 feet. 373

374

### Draft for Comment

Version

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15 375

Figure 4

. Example calculation of the aquatic spray drift distance using the “Active Rate” 376

and “Initial Average Concentration” as input s . The output is the “Distance to Point or 377

Area Average from Edge of Field

. ” In this calculation, the spray drift distance is 105 feet. 378

379

380

b. To estimate the spray drift distance considering exposure to both runoff and spray drift

, 381

use PRZM/EXAM S to find a spray drift fraction that mitigates risk and then use 382

AgDRIFT to find the corresponding spray drift distance . Using trial and error, c hange 383

the spray drift fraction input in PRZM/EXAM S and find a value that will mitigate risk to 384

both acute and chronic exposure s . Once you find the spray drift fraction that will 385

mitigate risk, use AgDRIFT to find the corresponding buffer distance to the i dentified 386

spray drift fraction. To do this, o pen AgDRIFT and under the “Toolbox” menu, choose 387

“Aquatic Assessment

. ” Select “EPA

- Defined Pond” and input the spray drift fraction 388

that will mitigate risk into the “Fraction of Applied

. ” The output will be “ Distance to the 389

Water Body f rom Edge of Field

, which will mitigate risk to aquatic organisms. 390

391

5. Round all spray drift distances to a whole number. Report all inputs and outputs used for 392

modeling in the risk assessment. 393 Select

Input

Input Output: Aquatic

Spray Drift Distance

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16 2.4. 

## Reporting on Modeling Procedures, Res ults, and Uncertainties 394

395

This section provides some example language that may be used to discuss both aquatic and 396

terrestrial spray drift distances. The purpose of the language is to provide an example discussion 397

of the uncertainty involving one and multi ple applications and involving a situation where a 398

greater than value occurs for a spray drift distance. The language is very basic and should be 399

edited as needed to summarize the spray drift distance results in an assessment, especially with 400

regard to di rect and indirect effects. Tables 3 and 4 show some example results for terrestrial 401

spray drift distances. In the example, the maximum spray drift distance would be greater than 402

997 feet. 403

404

Table X shows the spray drift distances estimated using LOCs divided by risk quotients 405

(calculated based on multiple applications) as the “Fraction of Applied” in AgDRIFT to 406

estimate the spray drift distance for terrestrial animals. Based on AgDRIFT 21 

### , pot ential direct 407

effects from exposure to spray drift may occur at greater than 997 feet from the use site for 408

multiple applications. 409

410

The distance estimated for plants is based on one application and does not reflect possible 411

cumulative exposure from multiple applications. It is recognized that a species could receive 412

exposure from multiple applications , in which case, this distance may underestimate risk. The 413

distance estimated for aquatic and terrestrial animals for multiple applications may occur when 414

wind is blowing consistently in one direction for all applications or when wind is blowing in 415

different directions during different applications as long as the organism is downwind in each 416

case and regardless of whether it is mobile or stationary

. Th is may result in an overestimation 417

of exposure for aquatic and terrestrial organisms whose spray drift distances are based on 418

exposure to the maximum number of applications and who are not downwind of every 419

application. Exposure to multiple applications i s more likely to occur when agricultural 420

fields/use areas are on multiple sides of an aquatic or terrestrial area of interest and when local 421

wind direction is not variable. 422

423

Table 3. Example of Spray Drift Distances Calculated for Terrestrial Animals, A ssuming 424

Aerial Application* 425

Taxa Type of

Endpoint Highest Risk

Quotient LOC ** Fraction of Applied

= LOC/RQ Spray Drift Distance

(feet)

Birds Acute 25 0. 5 0.02 479

Chronic 6.9 1 0.14 69

Mammals Acute 16.7 0. 5 0.03 312

Chronic 136.23 1 0.01 >997

RQ=risk quotient 

### 426

* A spray drift estimation of zero may result when the highest RQ exceeds the LOC because the model used to 

### 427

estimate spray drift exposure is a different model from th e model used to estimate terrestrial EECs. In this case, the 

### 428

spray drift distance needed to mitigate risk is expected to be very small. 

### 429

**The LOCs shown are for non

- listed species

. 

### 430

431

21 Modeled using the following input parameters for AgDRIFT : maximum application rate, Tier I Terrestrial

Assessment, aerial application, ASAE Fine to Medium DSD, and assuming a single application

.

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17 Table 4. Example of Spray Drift Distance for N on

- listed Terrestrial Plants 432

Taxa EC 25 (lbs

ai/A) Maximum Application

Rate in (lbs ai/A) Spray Drift Distance for One

Application (feet)

Terrestrial

Plants 0.0067 4 >997



### 433

Literature Cited 434

435

Haith, D. A. and F. S. Rossi. 2003. Risk assessment of pesticide runoff from turf. Journal of 436

Environmental Quality 32: 447

- 455. 437

438

National Academy of Sciences. 2013. Assessing Risks to Endangered and Threatened Species 439

from Pesticides . The National Academies Press. Washington DC. Available at 440

http://www.nap.edu/catalog.php?record_id=18344 (Accessed September 26, 2013). 441

442

USDA, NRCS. 2000. Conservation Buffers to Reduce Pesticide Losses. March 2000. Natural 443

Resources Conservation Service. United States Department of Agriculture. Fort Worth, 444

TX. Available at http://www.in.nrcs.usda.gov/technical/agronomy/newconbuf.pdf 445

(Accessed May 28, 2013). 446

447

Wright, J., & Sands, G. 2001. Planning an Agricultural Subsurface Drainage System . BU

448

07685. 2009. Agricultural Drainage P ublication Series: Soil Water Concepts. 449

University of Minnesota. Available at 450

http://www.extension.umn.edu/distribution/cropsystems/DC7685.html (Accessed 451

October 28, 2010). 452

453

454

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18 Appendix A

. Comparison of Results from Tier I, Tier II, and Tier III AgDRIFT Analysis U sing the ASAE V ery F ine to F ine

DSD and Fine to Medium DSD

Table A1. Comparison of the Distances from Edge of Field to P oint Downwind from Tier I, Tier II, and Tier II I AgDRIFT

Terrestrial Assessments Using the Default Input Parameters Specified in Section 2.1 and the Specified DSD

Fraction of

Applied

Deposited at

Point

Downwind Spray Drift Distance (Feet)

ASAE Very Fine to Fine DSD ASAE Fine to Medium DSD

Tier I Tier II Tier II÷

Tier I Tier III Tier III÷

Tier I Tier I Tier II Tier II÷

Tier I Tier III Tier III÷ Tier

I

0.01 Out of

Range Out of

Range na na na Out of

Range Out of

Range na 1387.78 na

0.02 Out of

Range Out of

Range na na na 479 479 1.00 479 1.00

0.03 Out of

Range Out of

Range na na na 311.68 311.68 1.00 314.96 1.01

0.04 Out of

range Out of

Range na 1076.1 na 236.22 232.94 0.99 236.22 1.00

0.05 741.46 708.65 0.96 741.46 1.00 183.72 183.72 1.00 187.01 1.02

0.06 577.42 557.74 0.97 577.42 1.00 160.76 160.76 1.00 160.76 1.00

0.08 400.26 390.42 0.98 400.26 1.00 121.39 121.39 1.00 121.39 1.00

0.1 305.11 295.27 0.97 305.11 1.00 98.42 98.42 1.00 98.42 1.00

0.2 124.67 121.39 0.97 124.67 1.00 32.81 32.81 1.00 32.81 1.00

0.3 52 52.49 1.01 52.49 1.01 16.4 16.4 1.00 16.4 1.00

0.4 16 13.12 0.82 16.4 1.03 6.56 6.56 1.00 6.56 1.00

0.5 3 0 0.00 3.28 1.09 0 3.28 na 0 na

0.6 0 0 na na 0 0 na 0 na



### na=not applicable

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19 Table A 2 . Comparison of Distances from Edge of Field to Water Body from Tier I, Tier II, and Tier II I AgDRIFT Aquatic

Assessments Using the Default Input Parameters Specified in Section 2.1 and the Specified DSD

Initial Average

Concentration (ng/L)

in Water Body with

Active Rate of 0.2505 Spray Drift Distance to Water Body (Feet)

Very Fine to Fine DSD Fine to Medium DSD

Tier I Tier II Tier II÷

Tier I Tier III Tier

III÷

Tier I Tier I Tier II Tier II÷

Tier I Tier III Tier

III÷

Tier I

3300 7 3 0.5 7 1 0 0 na 0 na

3000 23 20 0.86 23 1 0 0 na 0 na

2000 105 102 0.97 108 1.03 0 0 na 0 na

1000 367 354 0.96 367 1 55.77 55.77 1.00 55.77 1.00

950 397 381 0.96 400 1.01 62.34 62.34 1.00 62.34 1.00

800 522 499 0.96 522 1 85.3 85.3 1.00 85.3 1.00

700 646 617 0.95 646 1 104.99 104.99 1.00 104.99 1.00

600 850 804 0.95 853 1 134.51 131.23 0.98 134.51 1.00

556 994 938 0.94 1001 1.01 150.92 147.64 0.98 147.64 0.98

550 Out of

range 955 na 1020 na 150.92 150.92 1.00 150.92 1.00

540 Out of

range 994 na 1063 na 154.2 154.2 1.00 154.2 1.00

530 Out of

range Out of

range na 1106 na 160.76 157.48 0.98 160.76 1.00

257 Out of

range Out of

range Out of

range 2605 na 433.07 423.22 0.98 433.07 1.00

200 na na na na na 623.35 610.23 0.98 626.63 1.01

157 na na na na na 990.8 967.84 0.98 997.36 1.01

156 na na na na na Out of

Range 980.96 na 1010.49 na

155 na na na na na Out of

Range 994.08 na 1026.89 na

154 na na na na na Out of

Range Out of

Range 1043.29 na

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20 Initial Average

Concentration (ng/L)

in Water Body with

Active Rate of 0.2505 Spray Drift Distance to Water Body (Feet)

Very Fine to Fine DSD Fine to Medium DSD

Tier I Tier II Tier II÷

Tier I Tier III Tier

III÷

Tier I Tier I Tier II Tier II÷

Tier I Tier III Tier

III÷

Tier I

100 na na na na na Out of

Range Out of

Range 1952.08 na

64 na na na na na Out of

Range Out of

Range 2595.11 na

63 na na na na na Out of

Range Out of

Range Out of

Range na



### na=not applicable

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21 Appendix B

. How to Determine the Aquatic and Terrestrial Spray Drift Fraction for an

Application Rate in AgDRIFT for Ecological Assessments

1. Select the default input parameters for Tier I analysis as described in Section 2.1

.

2. Select "Tool box" and then "Aquatic Assessment" or “Terrestrial Assessment ”

.

3. Select the appropriate water body f rom the following choices:

For an aquatic assessment, select:

a. “EPA

- Defined Pond”: Pond with a depth of 2 meters (6.56 ft) and a downwind

width of 63.61 m (208.69 ft) and flight line width of 157.21 m (515.78 ft for a 1

ha pond)

.

For a terrestrial asses sment, select point deposition.

4. Enter the maximum application rate for t he use being evaluated in the "Active R ate"

window. This input does not change the fraction of applied pesticide distributed to the

water body.

5. Enter a “Distance to Point or Water Body f rom Edge of Field” ( Figure B 1 ). If a distance

is not specified on the label, the “Distance to the Point of Water Body from the Edge of

Field ” is zero for aquatic ecological risk assessments and one foot for terrestrial

assessments. For Drinking Water Assessments, see Appendix C

. Click the “ Calc”

button. The model then reports the “Fraction of Applied

, ” which is the estimated spray

drift fraction or fraction of pesticide application rate that will enter the water body or will

be deposited at a p oint off the field for a terrestrial assessment. 1 

### Tables B 1

- B6 provide

some example output s for standard spray drift fractions associated with different

distances.

### Draft for Comment

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22 Figure B 1. Example of the AgDRIFT input and output screen used to determine the spray

drift fraction. The input is the “Distance to Water Body f rom Edge of Field” shown in red

and the output is the “Fraction of Applied” or spray drift fraction

.

Table B1 . Fraction of Applied Pesticide at Different Distances from the Edge of the Field

to the Water Body that will be Distributed into the EPA Pond with Ground Application

(Calculated using Tier I Model in AgDRIFT version 2.1.1 )

Distance from Edge of

Field to Water B ody

(feet) Fraction of Applied or Spray Drift Fraction

High Boom Low Boom

ASAE V ery

F ine to F ine ASAE F ine to

M edium/ C oarse ASAE V ery

F ine to F ine ASAE F ine to

M edium/ C oarse

0 0.0616 0.0165 0.0268 0.0109

1 0.0572 0.0137 0.0231 0.0086

5 0.0455 0.0104 0.0167 0.0065

10 0.0376 0.009 0.0136 0.0056

25 0.0267 0.0071 0.01 0.0045

50 0.0194 0.0056 0.0076 0.0036

100 0.013 0.0042 0.0054 0.0028

150 0.0098 0.0034 0.0043 0.0023

200 0.0078 0.0028 0.0036 0.0019

250 0.0064 0.0024 0.0031 0.0017

300 0.0053 0.0021 0.0027 0.0015

350 0.0046 0.0019 0.0024 0.0013

400 0.0039 0.0017 0.0021 0.0012

450 0.0035 0.0015 0.0019 0.0011 

### Input

Output: Fraction

Spray Drift Select

### Draft for Comment

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23 Distance from Edge of

Field to Water B ody

(feet) Fraction of Applied or Spray Drift Fraction

High Boom Low Boom

ASAE V ery

F ine to F ine ASAE F ine to

M edium/ C oarse ASAE V ery

F ine to F ine ASAE F ine to

M edium/ C oarse

500 0.003 0.0014 0.0017 0.001

550 0.0027 0.0013 0.0016 0.0009

600 0.0024 0.0012 0.0015 0.0009

650 0.0022 0.0011 0.0013 0.0008

700 0.002 0.001 0.0012 0.0008

750 0.0018 0.0009 0.0012 0.0007

800 0.0017 0.0009 0.0011 0.0007

850 0.0015 0.0008 0.001 0.0006

900 0.0014 0.0008 0.001 0.0006

950 0.0013 0.0007 0.0009 0.0006

997 0.0012 0.0007 0.0009 0.0006

998 Out of range Out of range Out of range Out of range



### Table B 3 . Fraction of Applied Pesticide at Different Distances from the Edge of the Field

to the Water Body that will be Distributed into the EPA Pond with Aerial Application

(Calculated U sing Tier I Model in AgDRIFT V ersion 2.1.1 )

Distance from Edge of F ield

to the Water Body (feet) Fraction of Applied or Spray Drift Fraction

ASAE V ery F ine to F ine ASAE F ine to

M edium ASAE M edium to

C oarse

0 0. 242 1 0. 12 54 0. 08 85

1 0. 240 5 0. 12 76 0. 0 866

5 0. 234 0 0. 11 6 0. 0 789

10 0. 22 66 0. 10 82 0. 07 13

25 0. 20 76 0. 09 16 0. 0 564

50 0. 182 1 0. 07 3 3 0. 04 28

100 0. 14 46 0. 05 03 0. 0 271

150 0. 1 196 0. 03 85 0. 0 197

200 0.10 2 3 0. 03 14 0. 0 154

250 0. 0 889 0. 02 66 0. 01 26

300 0. 080 4 0. 023 1 0. 01 08

350 0.073 0 0. 02 05 0. 009 5

400 0.067 0 0. 0 186 0. 00 86

450 0. 062 2 0. 017 2 0. 008 1

500 0. 058 2 0.016 0. 007 4

550 0. 05 49 0.015 0.007

600 0. 052 0. 014 4 0. 006 6

650 0. 049 5 0. 013 8 0. 006 3

700 0. 047 4 0. 013 2 0. 006 1

750 0. 045 5 0.0128 0. 00 58

800 0. 04 39 0.0124 0. 005 6

850 0. 042 5 0.012 0. 005 5

900 0. 041 2 0.0117 0. 005 3

950 0. 040 1 0.0114 0. 005 2

997 0. 039 2 0.0111 0. 005 1

### Draft for Comment

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24 Distance from Edge of F ield

to the Water Body (feet) Fraction of Applied or Spray Drift Fraction

ASAE V ery F ine to F ine ASAE F ine to

M edium ASAE M edium to

C oarse

998 Out of range Out of range Out of range



### Table B 4 . Fraction of Applied Pesticide at Different Distances from the Edge of the Field

to a Terrestrial Point with Aerial Application (Calculated U sing Tier I Model in AgDRIFT

V ersion 2.01)

Distance from Edge of F ield

to Terrestrial P oint Fraction of Applied or Spray Drift Fraction

ASAE V ery F ine to

F ine ASAE F ine to

M edium ASAE M edium to

C oarse

0 0. 500 1 0. 5 0.5

1 0. 491 6 0.4808 0. 47 68

5 0. 45 72 0.4 0. 38 42

10 0. 42 34 0. 33 47 0.3

25 0. 3 61 0. 22 07 0. 1 698

50 0. 30 11 0. 17 09 0. 11 08

100 0. 22 36 0. 097 8 0. 05 72

150 0. 17 56 0. 06 27 0. 034 5

200 0. 140 1 0. 04 56 0. 024 5

250 0. 11 59 0. 03 67 0. 018 4

300 0. 10 01 0. 03 06 0. 01 46

350 0. 08 86 0.026 0. 012 2

400 0. 079 6 0. 02 27 0. 01 06

450 0. 072 5 0. 02 03 0. 009 4

500 0. 06 66 0. 01 85 0. 008 5

550 0. 062 1 0. 017 1 0. 00 79

600 0. 058 3 0.016 0. 007 4

650 0. 05 48 0.015 1 0.007

700 0. 051 8 0.0146 0. 006 6

750 0.0494 0. 013 7 0. 006 3

800 0. 047 4 0. 013 2 0. 006

850 0. 045 5 0.0128 0. 00 58

900 0. 04 39 0.0124 0. 005 7

950 0. 042 5 0.012 0. 005 5

997 0. 041 3 0.0117 0. 005 3

998 O ut of range O ut of range O ut of range



### Table B 5 . Fraction of Applied Pesticide at Different Distances from the Edge of the Field

to a Terrestrial Point with Ground Application with a High Boom (Calculated U sing Tier I

Model in AgDRIFT V ersion 2.1.1 )

Distance from Edge of F ield to

Terrestrial P oint (feet) Fraction of Applied or Spray Drift Fraction

ASAE V ery F ine to

F ine ASAE F ine to

M edium/ C oarse

0 1.06 1.01

1 0.8564 0.3731

### Draft for Comment

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25 Distance from Edge of F ield to

Terrestrial P oint (feet) Fraction of Applied or Spray Drift Fraction

ASAE V ery F ine to

F ine ASAE F ine to

M edium/ C oarse

5 0.4475 0.0889

10 0.2595 0.0459

25 0.104 0.0208

50 0.05 0.0119

100 0.0248 0.007

150 0.0164 0.0051

200 0.012 0.004

250 0.0093 0.0033

300 0.0075 0.0028

350 0.0062 0.0024

400 0.0053 0.0021

450 0.0045 0.0019

500 0.0039 0.0017

550 0.0034 0.0015

600 0.003 0.0014

650 0.0027 0.0013

700 0.0024 0.0012

750 0.0022 0.0011

800 0.002 0.001

850 0.0018 0.0009

900 0.0017 0.0009

950 0.0015 0.0008

997 0.0014 0.0008

998 O ut of range O ut of range



### Table B 6 . Fraction of Applied Pesticide at Different Distances from the Edge of the Field

to a EPA Pond with Airblast Application (Calculated U sing Tier I Model in AgDRIFT

V ersion 2.01)

Distance from edge

of field to water

body (feet) Fraction of Applied or Spray Drift Fraction

Normal (Stone and

Pome Fruit,

Vin e yard) Dense

(Citrus, Tall

Trees) Sparse

(Young,

Dormant) Vineyard Orchard

0 0.0011 0.0145 0.0416 0.0024 0.0218

1 0.0011 0.014 0.0395 0.0023 0.0208

5 0.001 0.0122 0.0323 0.0018 0.0175

10 0.0009 0.0106 0.0258 0.0014 0.0145

25 0.0007 0.0074 0.015 0.0009 0.0093

50 0.0005 0.005 0.0077 0.0006 0.0056

100 0.0003 0.003 0.0031 0.0003 0.0031

150 0.0002 0.0022 0.0017 0.0002 0.0021

200 0.0002 0.0017 0.001 0.0002 0.0016

250 0.0002 0.0014 0.0007 0.0001 0.0013

300 0.0001 0.0012 0.0005 0.0001 0.0011

350 0.0001 0.0011 0.0004 0.0001 0.0009

### Draft for Comment

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26 400 0.0000978 0.001 0.0003 0.0000881 0.0008

450 0.0000863 0.0009 0.0002 0.0000765 0.0007

500 0.0000769 0.0008 0.0002 0.0000672 0.0007

550 0.0000629 0.0007 0.0002 0.0000596 0.0006

600 0.0000626 0.0007 0.0001 0.0000533 0.0005

650 0.0000571 0.0006 0.0001 0.000048 0.0005

700 0.0000523 0.0006 0.0000898 0.0000435 0.0005

750 0.0000482 0.0005 0.0000771 0.0000397 0.0004

800 0.0000446 0.0005 0.0000668 0.0000363 0.0004

850 0.0000414 0.0005 0.0000583 0.0000334 0.0004

900 0.0000386 0.0005 0.0000513 0.0000309 0.0004

950 0.0000361 0.0004 0.0000453 0.0000286 0.0003

997 0.0000339 0.0004 0.0000405 0.0000267 0.0003

998 Out of Range Out of Range Out of

Range Out of Range Out of

Range



### Table B 7 . Fraction of Applied Pesticide at Different Distances from the Edge of the Field

to a Terrestrial Point with Airblast Application (Calculated U sing Tier I Model in

AgDRIFT V ersion 2.1.1 )

Distance from edge of

field to water body (feet) Fraction of Applied or Spray Drift Fraction

Normal (Stone

and Pome

Fruit,

Vin e yard) Dense

(Citrus, Tall

Trees) Sparse

(Young,

Dormant) Vineyard Orchard

0 0.0089 0.1155 0.4763 0.0376 0.2223

1 0.0081 0.1078 0.4385 0.0324 0.2046

5 0.0058 0.0834 0.3218 0.0195 0.1506

10 0.0042 0.0631 0.2285 0.012 0.108

25 0.0023 0.033 0.1007 0.0047 0.0503

50 0.0012 0.0157 0.0373 0.0019 0.021

100 0.0006 0.0065 0.0103 0.0008 0.0074

150 0.0004 0.0038 0.0044 0.0004 0.004

200 0.0003 0.0026 0.0023 0.0003 0.0026

250 0.0002 0.002 0.0014 0.0002 0.0019

300 0.0002 0.0016 0.0009 0.0002 0.0015

350 0.0002 0.0014 0.0006 0.0001 0.0012

400 0.0001 0.0012 0.0005 0.0001 0.0011

450 0.0001 0.0011 0.0004 0.0001 0.0009

500 0.0000965 0.0009 0.0003 0.000087 0.0008

600 0.0000765 0.0008 0.0002 0.0000667 0.0006

700 0.0000625 0.0007 0.0001 0.0000531 0.0005

800 0.0000523 0.0006 0.0000889 0.0000434 0.0005

900 0.0000446 0.0005 0.0000665 0.0000363 0.0004

997 0.0000387 0.0005 0.0000514 0.000031 0.0004

998 Out of Range Out of Range Out of

Range Out of Range Out of

Range

### Draft for Comment

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27 Appendix C

. Calculation of the Spray Drift Fraction for Drinking Water Assessment s

Using the Index Reservoir

.

The index reservoir scenario is used to model simulations to estimate drinking water exposure

and is intended as a replacement of the “standard pond

, ” which is used to estimate wildlife

exposure in aquatic ecosystems. The scenario is developed based on the Shipman City Lake in

Shipman, Illinois. It includes epheme ral and perennial streams that run into a reservoir. For

detailed information on use of the index reservoir in drinking water assessments

, refer to

Guidance on Development and Use of the Index Reservoir in Drinking Water ( USEPA, 2010 )

. The spray drift fraction for the index reservoir is calculated using AgDRIFT by adding the spray

drift fraction of the reservoir (82

- m width , 640

- m length, 2.7

- m average depth, no buffer ) to the

spray drift fraction of all streams (4

- m width, 1500

- m lengt h, variable depth, 4

- m buffer )

n ormalized to the index reservoir as follows :

Normalized Spray Drift Fraction for Streams (unitless)

=

Reservoir of Area Surface Streams All of Area Surface Streams all of t Fraction Spray Drif ×



### Adjusted Spray Drift Fraction for Index Reservoir (unitless) =

Reservoir of Fraction Drift Spray Streams for Fraction Drift Spray Normalized +



### Table C 1 provides the estimated spray drift fraction of the application rate for the index reservoir

and the ou t puts from AgDRIFT used to make this calculation

. At 10 mph wind speeds, t he spray

drift fraction of the application rate for the index reservoir is 14 % for aerial applications, 7 % for

ground applications, and 14 % for airblast applications

, using the default spray drift inputs as

specified in Section 2.1 and Tier I AgDRIFT version 2.1.1

. The corresponding spray drift

fraction at 15 mph wind speeds is 16 % for aerial applications.

Table C 1. Estimate the Spray Drift Fraction for Drinking Water Assessments Using Tier I

(10 mph wind speed) or Tier II (15 mph wind speed) Analysis in AgDRIFT Version 2.1.1

Scenario Spray Drift Fraction Estimated from AgDRIFT Normalized Spray Drift Fraction

Aerial, F ine to

M edium DSD 1 Ground 3 ,5 Airblast 4 Aerial, F ine to M edium

DSD 1 Ground 3 ,5 Airblast 4

10 mph (4.47 m/s) Wind Speed

Reservoir 0.106 0.05 0.0326 0.106 0.05 0.0326

All Streams with 4

-

m buffer 0.2531 0.1406 0.1353 7 0.0289 0.0161 0.0155

Index Reservoir 0.1349 0. 0661 0.048

15 mph (6.71 m/s) Wind Speed

Reservoir 0.1537 NA 5 NA 5 0.1537 NA 5 NA

All Streams with 4

-

m buffer 0.408 NA 5 NA 5 0.0466 NA 5 NA

Index Reservoir 0.2003 NA 5 NA

1 Assumed F ine to M edium DSD.

2 Assumed V ery F ine to F ine DSD.

3 Assumed V ery F ine to F ine DSD, high boom, and 90 th data percentile.

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28 4 Assumed sparse, young dormant orchard.

5 Ground and airblast applications are not adjusted for windspeed.



### USEPA. 2005. Clarification of Plant Evaluation Guidance . Memorandum From S. Bradbury to

Environmental Fate and Effects Division. October 4, 2005. Office of Pesticide Programs.

United States Environmental Protection Agency.

USEPA. 2010. Guidance on Development and Use of the Index Reservoir in Drinking Water

Exposure Assessments . September 14, 2010. Environmental Fate and Effec ts Division.

Office of Pesticide Programs. United States Environmental Protection Agency. Available

at http://www.epa.gov/oppefed1/models/water/index_reservoir_dwa.pdf (Access ed

December 9, 2010).

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29 Appendix D

. Example and Validation of Terrestrial Spray Drift Distance Approach

Calculation of Risk Quotients (output from T

- REX v 1.4.1)

Acute a

Kenaga

Chemical Name: 

### The ma

Use 

### both the

Formulation

Application Rate 1 lbs a.i./acre 

### RQs re

Half-life 35 days 

### <0.01 i

Application Interval 7 days 

### figure

Maximum # Apps./Year 5

Length of Simulation 1 year

Mallard duck LD50 (mg/kg-bw) 500.00

Bobwhite quail LC50 (mg/kg-diet) 200.00

Mallard duck NOAEL(mg/kg-bw) 10.00

Bobwhite quail NOAEC (mg/kg-diet) 10.00

500.00

200.00

10.00

10.00

Kenaga

Values

Short Grass 927.00

Tall Grass 424.88

Broadleaf plants/sm Insects 521.44

Fruits/pods/seeds/lg insects 57.94 

### Upper Bound Kenaga Residues For RQ Calculation



## Dietary-based EECs (ppm) NOAEL (mg/kg-bw)

NOAEC (mg/kg-diet) 

## Mammals LD50 (mg/kg-bw) Chemical X

Corn

Product X



### Endpoints

LC50 (mg/kg-diet) 

## Avian

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30 Avian Results

Avian Body Ingestion (Fdry) Ingestion (Fwet) % body wgt FI

Class Weight (g) (g bw/day) (g/day) consumed (kg-diet/day)

Small 20 5 23 114 2.28E-02

Mid 100 13 65 65 6.49E-02

Large 1000 58 291 29 2.91E-01

20 5 5 25 5.06E-03

Granivores 100 13 14 14 1.44E-02

1000 58 65 6 6.46E-02

Avian Body Adjusted LD50

Weight (g) (mg/kg-bw)

20 259.61

100 330.50

1000 466.84

small mid large

20 100 1000 20 100 1000

Short Grass 1055.76 602.04 269.54

Tall Grass 483.89 275.94 123.54

Broadleaf plants/sm Insects 593.87 338.65 151.62

Fruits/pods/seeds/lg insects 65.99 37.63 16.85 14.66 8.36 3.74

20 100 1000

Short Grass 4.07 1.82 0.58

Tall Grass 1.86 0.83 0.26

Broadleaf plants/sm insects 2.29 1.02 0.32

Fruits/pods/seeds/lg insects 0.25 0.11 0.04

Seeds (granivore) 0.06 0.03 0.01

Acute Chronic

Short Grass 4.64 92.70

Tall Grass 2.12 42.49

Broadleaf plants/sm Insects 2.61 52.14

Fruits/pods/seeds/lg insects 0.29 5.79 Avian Classes and Body Weights (grams) 

### Dose-based EECs

(mg/kg-bw) Granivores(grams)

Avian Acute RQs

Size Class (grams) 

## Dose-based RQs

(Dose-based EEC/adjusted LD50)

RQs 

## Dietary-based RQs

(Dietary-based EEC/LC50 or

NOAEC)

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31 pp g



### Mammalian Results

Mammalian Body Ingestion (Fdry) Ingestion (Fwet) % body wgt FI

Class Weight (g bwt/day) (g/day) consumed (kg-diet/day)

15 3 14 95 1.43E-02

Herbivores/ 35 5 23 66 2.31E-02

insectivores 1000 31 153 15 1.53E-01

15 3 3 21 3.18E-03

Grainvores 35 5 5 15 5.13E-03

1000 31 34 3 3.40E-02

Mammalian Body Adjusted Adjusted

Class Weight LD50 NOAEL

15 1098.92 21.98

Herbivores/ 35 889.14 17.78

insectivores 1000 384.58 7.69

15 1098.92 21.98

Grainvores 35 889.14 17.78

1000 384.58 7.69

15 35 1000 15 35 1000

Short Grass 883.83 610.84 141.63

Tall Grass 405.09 279.97 64.91

Broadleaf plants/sm Insects 497.15 343.60 79.66

Fruits/pods/seeds/lg insects 55.24 38.18 8.85 12.28 8.48 1.97

15 grams 35 grams 1000 grams

Acute Chronic Acute Chronic Acute Chronic

Short Grass 0.80 40.21 0.69 34.35 0.37 18.41

Tall Grass 0.37 18.43 0.31 15.74 0.17 8.44

Broadleaf plants/sm insects 0.45 22.62 0.39 19.32 0.21 10.36

Fruits/pods/lg insects 0.05 2.51 0.04 2.15 0.02 1.15

Seeds (granivore) 0.01 0.56 0.01 0.48 0.01 0.26

Acute Chronic

Short Grass 4.64 92.70

Tall Grass 2.12 42.49

Broadleaf plants/sm insects 2.61 52.14

Fruits/pods/seeds/lg insects 0.29 5.79 

### Dose-based RQs

(Dose-based EEC/LD50 or NOAEL) Granivores(grams) Mammalian Classes and Body weight



### Dose-Based EECs

(mg/kg-bw) Herbivores/ insectivores (grams)



### Dietary-based RQs

(Dietary-based EEC/LC50 or

NOAEC) Mammal RQs Small mammal Medium mammal Large mammal

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32 Table D 1. Summary of the Calculation of Fraction of Applied.

Taxa Type of

Endpoint Highest Risk Quotient LOC Fraction of Applied =

LOC/RQ

Birds Acute Oral 4.07 0. 5 0. 12

Acute Dietary 4.64 0. 5 0. 11

Chronic 92.70 1 0.01 1

Mammals Acute Oral 0.80 0. 5 0. 6 25

Acute Dietary 4.64 0. 5 0. 11

Chronic 92.70 1 0.01 1



### The spray drift distance that corresponds to 0.01 is out of range or greater than 997 feet. To verify that the fraction of applied would

reduce the risk quotient to a value below LOCs, the Fraction of Applied is multipl i ed by the a pplication rate and that is used as an

input in T

- REX. Note that all RQs are below LOCs in the T

- REX output shown below. Also, note that this method will be applicable

to both single and multiple applications.

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33

### Draft for Comment

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34 Avian Results

Avian Body Ingestion (Fdry) Ingestion (Fwet) % body wgt FI

Class Weight (g) (g bw/day) (g/day) consumed (kg-diet/day)

Small 20 5 23 114 2.28E-02

Mid 100 13 65 65 6.49E-02

Large 1000 58 291 29 2.91E-01

20 5 5 25 5.06E-03

Granivores 100 13 14 14 1.44E-02

1000 58 65 6 6.46E-02

Avian Body Adjusted LD50

Weight (g) (mg/kg-bw)

20 259.61

100 330.50

1000 466.84

small mid large

20 100 1000 20 100 1000

Short Grass 10.56 6.02 2.70

Tall Grass 4.84 2.76 1.24

Broadleaf plants/sm Insects 5.94 3.39 1.52

Fruits/pods/seeds/lg insects 0.66 0.38 0.17 0.15 0.08 0.04

20 100 1000

Short Grass 0.04 0.02 0.01

Tall Grass 0.02 0.01 0.00

Broadleaf plants/sm insects 0.02 0.01 0.00

Fruits/pods/seeds/lg insects 0.00 0.00 0.00

Seeds (granivore) 0.00 0.00 0.00

Acute Chronic

Short Grass 0.05 0.93

Tall Grass 0.02 0.42

Broadleaf plants/sm Insects 0.03 0.52

Fruits/pods/seeds/lg insects 0.00 0.06 Avian Classes and Body Weights (grams) 

### Dose-based EECs

(mg/kg-bw) Granivores(grams)

Avian Acute RQs

Size Class (grams) 

## Dose-based RQs

(Dose-based EEC/adjusted LD50)

RQs 

## Dietary-based RQs

(Dietary-based EEC/LC50 or

NOAEC)

### Draft for Comment

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35 pp g



### Mammalian Results

Mammalian Body Ingestion (Fdry) Ingestion (Fwet) % body wgt FI

Class Weight (g bwt/day) (g/day) consumed (kg-diet/day)

15 3 14 95 1.43E-02

Herbivores/ 35 5 23 66 2.31E-02

insectivores 1000 31 153 15 1.53E-01

15 3 3 21 3.18E-03

Grainvores 35 5 5 15 5.13E-03

1000 31 34 3 3.40E-02

Mammalian Body Adjusted Adjusted

Class Weight LD50 NOAEL

15 1098.92 21.98

Herbivores/ 35 889.14 17.78

insectivores 1000 384.58 7.69

15 1098.92 21.98

Grainvores 35 889.14 17.78

1000 384.58 7.69

15 35 1000 15 35 1000

Short Grass 8.84 6.11 1.42

Tall Grass 4.05 2.80 0.65

Broadleaf plants/sm Insects 4.97 3.44 0.80

Fruits/pods/seeds/lg insects 0.55 0.38 0.09 0.12 0.08 0.02

15 grams 35 grams 1000 grams

Acute Chronic Acute Chronic Acute Chronic

Short Grass 0.01 0.40 0.01 0.34 0.00 0.18

Tall Grass 0.00 0.18 0.00 0.16 0.00 0.08

Broadleaf plants/sm insects 0.00 0.23 0.00 0.19 0.00 0.10

Fruits/pods/lg insects 0.00 0.03 0.00 0.02 0.00 0.01

Seeds (granivore) 0.00 0.01 0.00 0.00 0.00 0.00

Acute Chronic

Short Grass 0.05 0.93

Tall Grass 0.02 0.42

Broadleaf plants/sm insects 0.03 0.52

Fruits/pods/seeds/lg insects 0.00 0.06 

## Dose-based RQs

(Dose-based EEC/LD50 or NOAEL) Granivores(grams) Mammalian Classes and Body weight



### Dose-Based EECs

(mg/kg-bw) Herbivores/ insectivores (grams)



## Dietary-based RQs

(Dietary-based EEC/LC50 or

NOAEC) Mammal RQs Small mammal Medium mammal Large mammal