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UNI TED STATES ENVIRONMENTAL PROTEC TION AG ENCY W ASHrNGTO N, D.C

. 20460

OFF ICE OF P REVEN TIO N

, P

ESTI CID ES

, AND T OXI C S U BS T ANCES

Chemical : Sulfometuron methyl PC Code : 122001 DP Barcode : D346169

MEMORANDUM

DATE : November 12 ,2009

S UBJECT : Response to E nvironmental Fate and E ff ects related C o mm ents on Sulfometuron Rere gistration Eligibility Document

FROM :

THRU :

TO : M ichael R. Barr ett ,**Che~i st** **,,-: .-j** **~~ <v** **cg** Keith G. Sappington

, Biolo gi s t C1 !\Jl-

........... ..., E nvironmental Ri sk Branch 5 E nvironmental Fate and Effects Division (7507P)

Mah Shamim

, Branch Chief E nviro nm ental Risk Branch 5 E nviro nm ental Fate and Effects Divi IOn (7507P)

Russell Wasem , C hemi ca l Review Manager Tom Moriarty

, Team Leader Rick Management & Implementation Branch I Pesticide Re-evaluation Divi sion (7 508P) 

### 1/ / / 

# e /0 '7

Attached are the Environmental Fate and Effec ts Division 's (EFED ' s) response to

comments made by s takeholders on the Reregistration E ligibility Document for Sulfometuron.! After compiling the c omments related to propo sed mitigation measures

I Available at: h ttp: / /www

. e pa.g ov / opp OOOO I / rer egi strationlsulfometuron me thyl! The RED i s s pecifically available a t: http : //www.epa .gov / opp OOOOI / reregis tratio nlRED s / su lf ometuron me thyl r ed.pdf Stakeholde r c omments are a vailable at: http : //www .regulatio ns.gov /searc hlRegs ihome .html#docke tDetail ?R EPA

·**HQ** PP

- 2008-0 1 292 including changes to the app lication rates, methods, and sites for sulfometuron methyl, EFED did follow-up modeling of sulfometuron methyl off-site drift which is a major source of exposure with the pot ential for unintended ecologica l effects. Results of the additional modeling, a summary list of environm ental fate and effects related comments, and proposed specific responses to the st akeholder comments are given below.3 

## Part 1: Summary of New Spray Drift Analysis Using the AgDRIFT Model

The stakeholder comments provided several su ggestions for reducing the off-site impact of sulfometuron methyl applica tions and evaluating off-site transport via spray drift for more typical application scenarios. The comm enters (including regi strants, user groups, and other interested parties) provided inform ation as well on the feasibility of specific use restrictions. The following AgDRIFT modeli ng results provide an evaluation of the impacts of these measures.

Due to the fact that the Agency plans to prohibit fixed wing ai rcraft liquid spray applications (most, but not all, of the cu rrent sulfometuron methyl labels already only allow for use of fixed winged aircraft applicatio ns for solid formulations with fertilizers) this assessment focuses on rotary winged (hel icopter) applications and drift from ground applications. Also, because a number of stakehol ders indicated that lo wer application rate limits may be feasible and that improvements in application equipment may now further reduce drift, these factors were also inves tigated. Our analysis s hows that substantial reductions in spray drift are possible w ith the implementation of these newer technologies. The specific modeling results are discussed in the following paragraphs.

In Table 1 the results of modeling are presen ted for various aerial application scenarios with a rotary aircraft (WA SP helicopter2) run with relativ ely conservative assumptions (such as a wind speed of 10 mph and a boom hei ght of 10 feet). Here the main variable tested is the droplet size spectrum. The reduc tions in drift from lowering the application rate are essentially proportional to the ra te applied. The use of equipment delivering coarser droplets can substant ially reduce drift. For exampl e, changing the droplet size spectrum from medium to very course reduc es spray drift by 65.5% at 50 feet, 62.4% at 100 feet, 70.0% at 200 feet, and 73.9% at 900 feet from the edge of the treated area (and if technologies are implemented which deliver very to extremely coarse droplet spectra along with rate reductions, even greater drif t reductions are obtainable, see Table 2 and Table 3 ). Note that the AgDRIFT Tier II default scenario evaluated in the sulfometuron methyl RED assumes a fine to medium dr op size distribution for aerial applications resulting in significantly more drift than each of the scenarios we tested in this

assessment.

Recognizing that in some types of uses a higher boom height may be needed (forestry and rights of way in rough te rrain or with variable ground co ver), we also compared the impact of spray delivered at a boom height of ten feet versus 15 feet for equipment delivering a very coarse spray spectrum (s ee Run IDs 3 and 4) – the higher boom height resulted in a increase in drift of 37.1% at 50 feet, 37.5% at 200 feet, and 50.0% at 900 feet from the edge of the treated area (dri ft amounts were very low, probably rounding error with this value). Note that, even when field conditions would force a rotary winged craft application at a 15-foot boom, the far fiel d drift with a very co arse droplet spectrum

2 The WASP helicopter is the only rotary winged aircraft represented in AgDRIFT.4 delivery is still somewhat lower (15-20%) than a coarse droplet spectrum delivery at a height of 10 feet (compare Run IDs 2 and 4).

Table 1. Estimated amount of sulfometuron meth yl spray drift from rotary aerial applications at various distances from a field treated with the proposed maximum labeled rate of 0.281 or 0.253 lb ai/A, di fferent droplet size spectra, and other mitigation options.

DISTANCE DOWN WIND (FEET) MODE: AERIAL TIER II MODE: AERIAL TIER II MODE: AERIAL TIER II MODE: AERIAL TIER II MODE: AERIAL TIER II MODE: AERIAL TIER II Lbs ai/A [% of rate] Lbs ai/A [% of rate] Lbs ai/A [% of rate] Lbs ai/A [% of rate] Lbs ai/A [% of rate] Lbs ai/A [% of rate]

0 0.1116 [39.70] 0.0769 [27.34] 0.0558 [19.85] 0.0908 [32.29] 0.0502 [19.83] 0.0691 [27.3]

50 0.0336 [11.93] 0.019 [6.77] 0.0116 [4.12] 0.0159 [5.67] 0.0104 [4.10] 0.017 [6.74]

75 0.0218 [7.76] 0.0127 [4.52] 0.0082 [2.9] 0.0111 [3.95] 0.0073 [2.88] 0.0113 [4.49]

100 0.0161 [5.71] 0.0091 [3.23] 0.0058 [2.05] 0.008 [2.83] 0.0051 [2.03] 0.0081 [3.20]

200 0.008 [2.84] 0.0039 [1.39] 0.0024 [0.85] 0.0033 [1.16] 0.0021 [0.84] 0.0035 [1.37]

500 0.0034 [1.21] 0.0016 [0.59] 0.001 [0.36] 0.0013 [0.48] 0.0009 [0.36] 0.0015 [0.57]

750 0.0052 [1.39] 0.0012 [0.44] 0.0007 [0.26] 0.001 [0.37] 0.0006 [0.25] 0.0011 [0.43]

900 0.0023 [0.84] 0.0011 [0.39] 0.0006 [0.23] 0.0009 [0.32] 0.0006 [0.22] 0.0010 [0.38]

Run ID 1 2 3 4 5 6

Key Input Assumptions

Applic. Rate, lb ai / A 0.281 0.281 0.281 0.281 0.253 0.253

Wind Speed, mph 10 10 10 10 10 10 Application height, ft. 10 10 10 15 10 10 Drop size distribution Medium Coarse Very coarse Very Coarse Very coarse Coarse Application Equipment WASP Helicopter WASP Helicopter WASP Helicopter WASP Helicopter WASP Helicopter WASP Helicopter (AgDRIFT Model Runs series 1)

In Table 2 the impact of lowering the applicat ion rate is evaluated and the relative drift from ground applications are compared to the rotary aircraft application. These lower application rates have been tested upon the basis of suggestions by DuPont (please refer to the Docket for comments on the Sulfometuron Methyl RED for a copy of their proposal) and forestry interests. The aerial applications tested here are ones with5 equipment delivering a course droplet si ze spectrum representing a measure of improvement over the types of spray conditions originally modeled in the sulfometuron methyl RED.

As before, lowering the application rate resu lts in a nearly exactly proportional reduction in the amount of drift (Compare Run IDs 2, 7, and 8). Ground application results in much reduced drift compared with coarse sp rays from helicopters: depending on whether a release height of 4.2 or 1.7 feet was chose n, the ground applications resulted in from 82 to 89% less drift at 50 feet, 72 to 82% less dr ift at 200 feet, and 73 to 82% less drift at 900 feet.

Table 2 . Estimated amount of sulfometuron meth yl spray drift from rotary aerial and ground applications at various distanc es from a field treated with reduced application rates.

DISTANCE DOWN WIND (FEET) MODE: AERIAL TIER II MODE: AERIAL TIER II MODE: AERIAL TIER II MODE: GROUND TIER I MODE: GROUND TIER I Lbs ai/A [% of rate] Lbs ai/A [% of rate] Lbs ai/A [% of rate] Lbs ai/A [% of rate] Lbs ai/A [% of rate]

0 0.0769 [27.34] 0.0655 [27.29] 0.0543 [27.27] 0.2845 [101.0] 0.2831 [101.0]

50 0.019 [6.77] 0.0162 [6.75] 0.0133 [6.70] 0.0034 [1.19] 0.0021 [0.74]

75 0.0127 [4.52] 0.0107 [4.47] 0.0088 [4.44] 0.0025 [0.87] 0.0015 [0.55]

100 0.0091 [3.23] 0.0076 [3.19] 0.0063 [3.14] 0.0020 [0.70] 0.0012 [0.44]

200 0.0039 [1.39] 0.0033 [1.36] 0.0026 [1.33] 0.0011 [0.40] 0.0007 [0.26]

500 0.0016 [0.59] 0.0014 [0.57] 0.0011 [0.5t] 0.0005 [0.17] 0.0003 [0.12]

750 0.0012 [0.44] 0.0010 [0.43] 0.0008 [0.42] 0.0003 [0.11] 0.0002 [0.08]

900 0.0011 [0.39] 0.0009 [0.38] 0.0007 [0.37] 0.0003 [0.08] 0.0002 [0.07]

Run ID 2 7 8 9 10

Key Input Assumptions 1

Applic. Rate, lb ai / A 0.281 0.240 0.199 0.281 0.281

Wind Speed, mph 10 10 10 NS 4 NS 4

Application height, ft. 10 10 10 4.17 2 1.67 3

Median Droplet Size (um) 384 384 384 341 341

Drop size distribution Coarse (ASAE) Coarse (ASAE) Coarse (ASAE) Fine to medium coarse (ASAE) – 90 th %ile Fine to medium

coarse (ASAE) - 90 th %ile Application Equipment WASP Helicopter WASP Helicopter WASP Helicopter Ground Ground6 1 Run #2 is repeated from Table 1 ; Run #7 and 8 have identical inputs to Run #2 except for the lower application rates assumed.

2 Select the “high boom” option for AgDRIFT ground application model input.

3 Select the “low boom” option for AgDRIFT ground application model input.

4 NS = Not specified in the AgDRIFT model documentation. The Tier 1 data likely reflect data collected at a wind speed of about 10 mph as this is generally the defa ult assumption used by AgDRIFT.

Finally, Table 3 presents scenarios which represent, based on information received in comments on the RED and additional follow-up communications with stakeholders, the best practical exposure reducti on scenarios for sulfometuron methyl. Specifically, Table 3 presents the impact of using rotary aircraft and spray equipment capable of delivering very coarse to extremely coarse dr oplet size spectra at each of the proposed lower the application rates. Also presented is the relative drift from ground applications at the proposed reduced rate using more typica l spray delivery efficiency (i.e., the 50th percentile drift data from the AgDRIFT empirical model).

The modern technology coarser spra y applications presented in Table 3 result in significantly reduced drift from older technol ogy applications largely portrayed in Table 1 and Table 2. For example, at the rate of 0.199 lb ai/A: compared to the “coarse” spray applications the “very coarse to extremely coarse” applications resulted in 50.5% less drift at 30 feet, 47.4% less drif t at 50 feet, 45.5% less drift at 75 feet, 50.8% less drift at 100 feet, 53.8% less drift at 150 feet, and 54.5% less drift at 900 feet downwind from the treated area.

Table 3. Estimated amount of sulfometuron methyl spray drift from rotary aerial using equipment delivering very coarse droplet size spectra at various distances from a field treated with reduced application rates (also compared with ground applications).

DISTANCE DOWN WIND (FEET) MODE: AERIAL TIER II MODE: AERIAL TIER II MODE: AERIAL TIER II MODE: AERIAL TIER II MODE: AERIAL TIER II MODE: GROUND TIER I

Lbs ai/A [% of rate] Lbs ai/A [% of rate] Lbs ai/A [% of rate] Lbs ai/A [% of rate] Lbs ai/A [% of rate] Lbs ai/A [% of rate]

0 0.0543 [27.27] 0.0394 [19.81] 0.0327 [16.44] 0.0558 [19.85] 0.0463 [16.47] 0.2835 [101.0]

30 0.0208 [10.44] 0.0131 [6.59] 0.0103 [5.16] 0.0186 [6.63] 0.0146 [5.19] 0.0038 [1.37]

50 0.0133 [6.70] 0.0081 [4.08] 0.007 [3.52] 0.0116 [4.12] 0.01 [3.56] 0.0023 [0.83]

75 0.0088 [4.44] 0.0057 [2.84] 0.0048 [2.42] 0.0081 [2.90] 0.0069 [2.47] 0.0016 [0.57]

100 0.0063 [3.14] 0.004 [2.00] 0.0031 [1.56] 0.0058 [2.05] 0.0045 [1.60] 0.0012 [0.44]

150 0.0039 [1.95] 0.0024 [1.20] 0.0018 [0.90] 0.0035 [1.24] 0.0026 [0.93] 0.0009 [0.31]

200 0.0026 [1.33] 0.0016 [0.81] 0.0012 [0.60] 0.0024 [0.85] 0.0018 [0.63] 0.0007 [0.23]

500 0.0011 [0.55] 0.0007 [0.34] 0.0005 [0.25] 0.0011 [0.37] 0.0007 [0.26] 0.0002 [0.09]7 750 0.0008 [0.42] 0.0005 [0.24] 0.0003 [0.17] 0.0007 [0.26] 0.0005 [0.18] 0.0002 [0.05]

900 0.0007 [0.37] 0.0004 [0.21] 0.0003 [0.15] 0.0006 [0.23] 0.0005 [0.16] 0.0001 [0.04]

Run ID 8 11 12 13 14 15

Key Input Assumptions

Applic. Rate, lb ai / A 0.199 0.199 0.199 0.281 0.281 0.281

Wind Speed, mph 10 10 10 10 10 NS 1

Application height, ft. 10 10 10 10 10 4.17

Median Droplet Size (um) 384 476 519 476 519 341

Drop size distribution Coarse (ASAE) Very Coarse (ASAE) Very Coarse to Extremely Coarse (ASAE) Very Coarse (ASAE) Very Coarse to Extremely Coarse (ASAE) Fine to medium

coarse (ASAE) – 50 th %ile Application Equipment WASP Helicopter WASP Helicopter WASP Helicopter WASP Helicopter WASP Helicopter Ground

1 NS = Not specified in the AgDRIFT model documentation. The Tier 1 data likely reflect data collected at a wind speed of about 10 mph as this is generally the defa ult assumption used by AgDRIFT.8 

## Part 2: Environmental Fate and Effects Related Stakeholder Comments and Agency Responses

Stakeholder comments with specific commen ts / suggestions / recommendations are grouped into similar categorie s. A brief summary of the comment(s) is provided followed by the EFED response.

Comment Group 1

. SUMMARY OF COMMENTS: EPA received several comments regarding the te rm “under the forest canopy” noting that the phrase is vague and confusing.

EFED Response # 1

. The forest canopy is language suggested in th e label review manual. SRRD has advised they will take back this language based on th e label review guidance. The language here should follow the standards for other pesticid es which are not registered for aquatic applications. ********

Comment Group 2. SUMMARY OF COMMENTS: The Agency received comments that the cu rrent label language regarding “light sandy soil” does not provide useful application information.

EFED Response # 2

. This language is common among many sulfomet uron methyl labels and is the design of the reregistration process that a ll labels will bear the same language. The objective of this language is to obtain consistency in weed cont rol and reduce off-site transport in areas with erodible soil. The EFED does not believe it is feasible, from a technical or practical standpoint, to precisely define the problem soils exactly on the ba sis of soil textural composition and organic matter content. Ho wever, the EFED agrees that general language, like that provided by the commente r, might be helpful to applicators:

Soils that are subject to wind erosion usua lly have high silt and / or very fine and fine sand textural fractions. Low organi c matter also tends to increase a soil’s wind erosion potential ********

Comment Group 3. SUMMARY OF COMMENTS: The Agency received comments stating that the term “aquatic plants” is too vague and does not provide useful application information.

EFED Response # 3

. The EFED believes that the term “aquatic ve getation” is reasonable and clear. If9 additional clarification is desi red, however, the following text (bolded) may be added to the label for clarification:

“Do not apply within 500 feet of bodies of water containing aquatic vegetation (e.g., submerged and emergent aquatic plants, algae) , water used as an irrigation source and crops.”

Note that the buffer width may be further relaxed with the proposed rate reductions and the emphasis on use of application technol ogy that further redu ces spray drift. ********

Comment Group 4. SUMMARY OF COMMENTS: The Agency received numerous comments re garding the “release height” modeled in the RED and required on the sulfometuron methyl . Commenters noted that in commercial forestry scenarios, a 10 foot re lease height is often unsafe. As an example, it was noted by one respondent that, in Washington state fo restry application areas are “1) located in mountainous terrain and 2) have scattered wildlife trees (req uired by state forest practice rules) in them.” Several co mmenters noted support for langu age that provided for safety without mandating a 10 foot release height.

EFED Response # 4

. The Agency uses AgDRIFT, a peer reviewed pr edictive models that is primarily designed for commercial agricultural scenarios. In this context, a 10-foot release height is achievable and desirable for minimizing off-site transport. However, as pointed out in the numerous comments above forestry uses of ten are in scenarios where the ground cover and/or terrain make such a low release height impractical and unsafe. The use of a 10 or 15 foot release height is the predominantly used range of the AgDRIFT model and has been used to facilitate comparisons by th e Agency between application scenarios with different inputs such as app lication rate, or droplet size.

The EFED recommends that the proposed la nguage regarding the re lease height should be modified to insure that practical and safe methods will be used in forestry, rights of way, or other application situations where the terrain and land cover variation would make a set release height impractical. The la bels should require that spray height be the minimum level that meets safety standards and drift prevention objectives. One example of how this might read is:

Sulfometuron methyl should be applied at a boom height as close to 10 feet as is efficacious and safe (to minimize the zone of drift of potentially ecologically significant amounts of sulfometuron methyl ). Under certain circumstances (e.g., in areas of rough terrain or variable la nd cover) it may be necessary to apply sulfometuron methyl at a gr eater boom height. State and local best management practice guidelines and directives should be consulted and followed.10 The final language chosen should be consistent with other labels for products with drift concerns. The impact of boom height, nozzle ty pe (impact of using nozzles that deliver a coarser spray spectrum such as “rain drop” nozzles) and other factors on off-site drift levels has been discussed in the “Summary of New Spray Drift Analysis Using the AgDRIFT Model” section. ********

Comment Group 5. SUMMARY OF COMMENTS: One commenter noted to the Agency: “The RED fails to provide empirical evidence that use of sulfometuron methyl he rbicides in accordance with the current label causes harm to aquatic vegetation.”

EFED Response # 5

. With respect to aquatic vegetation, the RE D is based on standard risk assessment methods used by the Agency for assessing ecological risk s to non-target ecological receptors, including aquatic plants. Th is methodology, which relies on predicted concentrations in surface water based on maxi mum labeled rates, indicates potential risks to both vascular and non-vascular aquatic plan ts. These findings are consistent with the mode of action of sulfometuron methyl and results from risk assessments of other sulfonylurea herbicides. Cons istent with risk findings for non-target aquatic plants, potential risks were also identified for non- target terrestrial plants. While empirical evidence (e.g., ecological incide nt reports) are considered in the characterization of ecological risks, such reports are likely subj ect to considerable bi as (i.e., underreporting) particularly for ecological receptors for wh ich adverse effects are rarely documented (e.g., aquatic plants). Therefore, lack of empirical evidence (e.g., ecological incident reports) does not supplant findings from ot her aspects of the Agency’s standard ecological risk assessments. As a point of reference, more than a dozen ecological incident reports classified as “probable” were associated with registered uses and effects on terrestrial non-target plants. ********

Comment Group 6. SUMMARY OF COMMENTS: The Agency received several comments rega rding the appropriateness of the AgDRIFT model for this risk assessment. Additional comments were also received regarding the inputs EPA used in the AgDRIFT modeling sc enario, such as wi nd speed, application equipment, or droplet size, noting that th e inputs are overly cons ervative and do not reflect typical appl ication variables.

EFED Response # 6

. A noted above, AgDRIFT is an Agency approved, vetted model that is appropriate for evaluation of the factor s being considered to reduce the impacts of spray drift from sulfometuron methyl use. In response to the RED comments, EFED has modeled a variety of realistic scenarios to determine how the amount of drift at various distances from the treated area can be redu ced. Regarding comments on the application11 equipment (typically fixed wing for applicati ons of fertilizer and sulfometuron methyl and rotary craft for just sulf ometuron methyl), and droplet si ze the Agency has modeled a variety of realistic scenarios to determine how the amount of drift at various distances (based on different input combinations ) can reduce environmental exposure.

EFED has evaluated the reductions in drift fr om applications with coarser droplet size and wind speeds down to 10 mph based upon re commendations from commenters and discussions with stakeholders. Based upon its work, over the years, regarding modeling aerial applications, the Agency does not believ e it is practical to limit applications to wind speeds below 10 mph. The Agency has not evidence that stetting a maximum wind speed of 7 mph (or even less) can be consistently followed. Therefore, the Agency has determined that a maximum wind speed of 10 mph is the lowest wind speed that can be enforced and consequently uses it as the default wind speed for modeling.

We have rerun AgDRIFT with many scenarios using rotary aircraft (helicopter), ground applications, droplet size spectrums ranging to extremely course classifications, etc. We have seen no evidence that setting a maximum wind speed of 7 mph (or even less) can be consistently followed by the end-user; the Agen cy has determined at the current time that a maximum wind speed of 10 mph is the lowe st maximum level that can be enforced.

The Agency will review any additional submitte d spray drift studies that are relevant, and modify the sulfometuron methyl label based upon these data if appropriate. ********

Comment Group 7. SUMMARY OF COMMENTS: This comment stated that the current regul atory studies already “adequately addresses reproductive risk to non-target plants.”

EFED Response # 7

. While toxicity data were available for e ndpoints related to systemic growth, seedling emergence and visual injury, these guidel ine studies are not designed to capture reproductive endpoints. The Agency is aware of evidence to suggest plant reproduction may be affected by sulfonylurea herbicides at levels below effects on vegetative growth or visual injury (Fletcher et al., 1993) 3 . Uncertainty regarding the potential greater sensitivity of terrestrial pl ant reproduction has been di scussed extensively in the environmental fate and effects assessment for chlorsulfuron (D330621). Consistent with the Data Call-In for chlorsulfuron, the Ag ency is requesting a study to address the sensitivity of terrestrial plant re production to sulfometuron methyl.

3 Fletcher, J.S., T.G. Pfleeger, and H.C. Ratsch. 1995. Chlorsulfuron influence on garden pea reproduction. Physiol. Plantarum 94: 261-267.12 

## APPENDIX 1: Text of Comments being responded to in This Document

The relevant excerpts from stakeholder comments on the Sulfometuron Methyl RED being responded to in this document are pr ovided below (the OPP Divisions asked to respond are followed by the docket numbers from which the comments originate are provided in parenthesis).

1. EFED, OGC. (Docket #131, 17, 22, 102, 75) SUMMARY OF COMMENTS: EPA received se veral comments regarding the term “under the forest canopy” noting that the phrase is vague and confusing.

On page 32 of the RED, under Environmental Hazards the term except “under the forest canopy” was added. This term is very vague, open to interpretation, and accomplishes nothing but confusion in the context of the sentence it was added to.

__ The definition of the phrase, "forest canopy" is too broad.

___ On page 32 of the RED, under Environmental Hazards the term except “under the forest canopy” was added. This term is very vague , open to interpretation, and accomplishes nothing but confusion in the cont ext of the sentence it was adde d to. This term should be clarified, dropped or re-worded.

___ The phrase “...under the forest canopy...” v ague, leaving this recommendation open for interpretation and will cause confusion among applicators and regulators alike. Is the intent to allow application to water when working under a forest canopy? What defines a “forest canopy”?

___ Under Environmental Hazards (pg. 32 of 42) the statement “except for under forest canopy” is confusing. How is this meant to be interpreted?

2. EFED, SRRD, RD SUMMARY OF COMMENTS: The Agency received comments that the cu rrent label language regarding “light sandy soil” does not provide useful application information.

Non target plant exposure through soil particle drift wind erosion drift.

“...applications are made to powdery dry soil or light sandy soil.” More specifics could be included here as you are referring to so ils that are subject to wind erosion. Forest soils that have an intact forest floor are not subject to wi nd erosion. “Light sandy soil,”13 is not a soil texture class as defined by the U.S. Department of Agricu lture classification. Soils that are subject to wind erosion ha ve high silt, very fine and fine sand textural fractions. Low organic matter is another factor that can increase a soil’s wind erosion potential.

3. EFED (#131, 17) SUMMARY OF COMMENTS: The Agency received comments stating that the term “aquatic plants” is too vague and does not provide useful application information.

The definition of the phrase, "aquatic plants" is too broad.

__ “Do not apply within 500 feet of aquatic ve getation, water used as an irrigation source and crops.” is not a scientifically based c onclusion and will be very difficult to comply with in practice. For one, define aquatic vegeta tion? By itself, this is a very vague term that only a botanist could defin e accurately. I would interpret this to mean that I would have to put a 500 foot buffer around any fish bearing stream or any intermittent stream or channel that may contain an aquatic plant or something that looks like an aquatic plant? What about a small incons equential ground seep within a 40 acre clear-cut that contains aquatic vegetation. Am I required to identify and protect such areas with a 500 foot buffer? With the preponderance, in Western Oregon, of stre ams and side channels feeding these streams on a se asonal basis, I would interpret this label requirement to mean that I shouldn’t spray with in 500 feet of any of thes e topographic features to avoid a label violation.

4. EFED (#24, 73, 21, 63, 166, 137, 112, 120, 102, 105, 171, 170, 165, 155, 79) SUMMARY OF COMMENTS: The Agency received numerous comments regarding the “release height” modeled and cited on the product label. Comm enters noted that in commerci al forestry scenarios, a 10 foot release height is often unsafe. As an example, it was noted by one respondent that, in Washington state forestry application area s are “1) located in mountainous terrain and 2) have scattered wildlife trees (required by state forest prac tice rules) in them.” Several commenters noted support for language that provided for safety without mandating a 10 foot release height.

The proposed label change requiring a maximu m aerial application height of 10 feet for forestry applications is completely unfeasible for two main reasons. Forestry herbicide application areas in Washington are 1) lo cated in mountainous terrain and 2) have scattered wildlife trees (required by state fore st practice rules) in them. These two factors14 make it impossible and extremely unsafe for pi lots to maintain this height above the ground.

___ We believe that the prohibition on aerial applic ations more than 10 feet above the canopy is not only unnecessary, but can create hazardous operating conditions. Spray nozzle height is only one of many va riables that affect spray drift, and operators should be allowed discretion in determining spray height as long as other conditions are such that drift prevent ion objectives can be met. Retention of tall snags and green trees are often required or encouraged by forest practice re gulations or certification programs. Given the conditions on most forest sites where we prescribe aerial applica tions, we feel that excessive constraints on professional knowle dge and judgment of trained applicators and pilots may create hazardous conditions and be counter-produc tive to effective applications.

___ Your proposed requirement to prohibit applic ation above 10 feet is not achievable with any margin of safety. Terrain that is too steep and/or has obstacles such as small branches will cause accidents fo r any pilots that try to comply with this requirement.

___ The flying height restriction is an unnecessary addition to the label that could also be construed as dangerous. Flying an agricultural aircraft over rugged terrain can be even more hazardous when trying to fly excessively low. There are many small trees, snags and other obstructions that are dangerous to work around in spray treatment areas. Modern spray systems are designed to releas e the droplets at a safe height above the vegetation so that swath deposition is even across the ground. This system was designed for right of way applications and produce mini mal fine droplets. Low flying should not be regulated with label language, le t the pilot decide what is safe, prudent and produces the best application.

=========== We also note that the miti gation measures recognize that the 10-foot maximum does not apply if "a greater height is required for ai rcraft safety." However, the RED establishes 10 feet as the regulatory norm, with the poten tial that deviations will be difficult to justify. We recommend the label require that spray height be th e minimum level that meets safety standards and drift prevention objec tives. Any reference to 10 feet should be limited to level areas of re latively uniform canopy height

.

__ Prohibition of aerial forest ry applications more than 10 feet above the canopy is inherently dangerous. The “canopy” in forestry herbaceous weed c ontrol treatments is virtually ground level. Operators should be al lowed discretion in spray height so long as other conditions allow accurate deposition of the spray mixture. Aerial forestry applications use helicopters. Low airspeed and use of drift control booms and nozzles (e.g. Accu-Flo nozzles) produce coarse droplet sizes with few fine droplets subject to drift. Drift control booms and nozzles do not develop an acceptable spray pattern at 10 feet of altitude. The remedy, use of olde r boom and nozzle technology, would create more fine droplets and negate the perceived benefi t of low altitude. The proposed measure will15 only serve to increase the potential for the gr eatest risk to the en vironment and to safety, an aircraft accident.

___ Safety of our staff and operato rs is paramount to our busines s. The imposition of a fixed 10-foot height above the canopy for aerial applications is hi ghly unsafe under normal application conditions which include flying over trees with heights that vary by much more than 10 feet. In addition to the risk this poses on operators, enforcement and compliance of such a requirement will be challenging. I would encourage the EPA to change this language to include provisions for safety.

We also note that the mitigat ion measures recognize that the ten-foot maximum height during aerial application does not apply if “a greater height is required for aircraft safety.” However, the RED establishes ten feet as the regulatory norm, with the potential that deviations will be difficult to justify. The imposition of a fixed ten-foot flight-height above the canopy for aerial applications would be highly unsafe under normal application conditions, which incl ude flying over trees with he ights that vary by much more than ten feet. We recommend the label re quire that spray hei ght be the minimum level that meets safety standar ds and drift prevention objectives.

___ “Spray must be released at the lowest hei ght consistent with pest control and flight safety. Do not release spray at a height gr eater than 10 feet above the crop canopy unless a greater height is required for aircraft safety.”

___ Flight Height. We note that the mitigation measures recogn ize that the 10-foot maximum does not apply if "a greater height is requi red for aircraft safety ." However, the RED establishes 10 feet as the regulatory norm, w ith the potential that deviations will be difficult to justify. Spray height is only one of many variable s that affect spray drift, and operators should be allowed di scretion in determining spra y height as long as other conditions are such that drift prevention objectives can be met. Moreover, sustainable forestry practices require that individual trees or groups of trees are left on a site for various reasons after harvest. The "canopy" woul d then consist of the growing trees of a uniform height, punctuated by much higher "leave" trees.

___ Finally, we endorse the proposed label l anguage addressing aerial application height (page 34 of the RED) in which operators are allowed to apply sulfometuron methyl at heights greater than 10 feet abo ve the canopy if a greater hei ght is required for safety. Clearly, a requirement for applic ations to be 10 feet or less above the canopy can create hazardous operating conditions in some loca tions. However, we would like to point out that spray height is only one of many vari ables that affect spra y drift, and operators should be allowed discretion in determining sp ray height as long as other conditions are such that drift prevention object ives can be met, even if safe ty is not the primary goal for such an adjustment. Many companies attempt to bunch leave trees (for wildlife) in riparian corridors or other distinct locati ons to allow lower aerial applications of chemicals, but forest sites are often st eep and have significant “roughness, ” which may require applications at greater heights. Cu rrent application methods are resulting in infrequent and minimal delivery of forest he rbicides to streams, including sulfometuron16 methyl.

___ The notion that restriction of ai rcraft to within ten feet of a forest canopy is a recipe for crashing aircraft, and for locally damaging impact both from fuel and concentrated herbicide spill, but also with loss of life and aircraft. It makes no sense, and does not properly reflect any demonstrated improvement in targeting of chemical so long as large drops are specified. Please drop this stipulation.

___ The proposed label restriction for spray releas e height is hazardous. A vast majority of forestry application sites have uneven terrain and numerous standing trees. Aerial application on these sites cannot be safely done under the 10 f oot restriction. Pilots must be allowed flexibility in est ablishing safe release height thresholds and be allowed to employ other suitable methods to reduce drift.

___ EPA’s proposal to prohibit aerial applicati ons more than 10 feet above the canopy is similarly unsupported by the record for the re asons discussed above, is impractical, and will result in hazardous operating conditions. There is no evidence that current spray height practices have created problems or c oncerns (indeed, EPA notes that most of the reported incidents involving this herbicide do not appear to involve aerial application at all, much less being traceable to spray he ight issues). As noted by NCASI and other commenters, forest sites are often charac terized by uneven terrain and varying canopy heights, making it difficult, impractical, and uns afe to attempt to maintain a 10 foot spray height. The fact that the proposed spray heig ht restriction is qualif ied by the statement that it does not apply if “a grea ter height is required for ai rcraft safety” does not resolve this issue. It will still create regulatory pr essure to fly at unsafe low levels, and creates uncertainty and the potential for future disputes over when such a “greater height” would be justified.

___ We also note that the miti gation measures recognize that the 10-foot maximum does not apply if “a greater height is required for ai rcraft safety.” However, the RED establishes 10 feet as the regulatory norm, with the poten tial that deviations will be difficult to justify. Even a flat harvested site will have various snags and other trees remaining that will present hazards at 10 feet. We recommend the label require that spray heig ht be the minimum level that meets safety standards and drift prevention objectives. Any re ference to 10 feet should be limited to level areas of relatively uniform canopy height.

5. EFED. (#132). SUMMARY OF COMMENTS: This comment was received by the Agency: The RED fails to provide empirical evidence t hat use of sulfometur on methyl herbicides in accordance with the current label causes harm to aquatic vegetation.17 6. EFED (#165, 134, 46, 27, 35, 36, 102, 155). SUMMARY OF COMMENTS: The Agency received several comments rega rding the appropriateness of the AgDRIFT model for this risk assessment. Additional comments were also received regarding the inputs EPA used in the AgDRIFT modeling sc enario, such as wi nd speed, application equipment, or droplet size, noting that th e inputs are overly cons ervative and do not reflect typical appl ication variables.

We believe the AgDRIFT model used to estimate spray drift over-predicts drift, and that the input parameters of wind sp eed and droplet size are unrea listic. As a result the model outputs are unrealistic and over estimate drift potential.

--------------- With help, I was able to locate the inform ation about how the AgDrift model was applied to this RED that resulted in 500 foot buffers for aerial spraying. In short, the inputs to the model in no way represent the past 5-10 years re al world use of SMM here in the Pacific Northwest. That is why we have had not had incidents in damaging buffer vegetation, much less damage to aquatic vegetation. Ther efore these huge bu ffers are not needed.

Errors in the AgDrift model parameters 1) In the RED use of the AgDrift model, the first things that are not correct are: the use of a fixed wing aircraft that flies at 2- 3 times as fast as the helicopters that are required to be used by the present label! The only use of fixed wing aircraft on the Oust XP label is for the application of dry fertil izer that has been impregnat ed with Oust XP. Period. For all liquid spray uses, helicopters are required.

2) The nozzle type selected for the AgDrift calculations were characterized as “Fine” droplet generators. While this may be allowed by the label, our usage is exclusively in utilizing nozzles such as the Accu-Flo® nozzl es and others that resu lt in spray droplet spectra which are characterized as Coarse or Ultra Coarse by the American Society of Agricultural and Biological Engineers (ASABE) Standards.

3) The airspeed of the Ag Tractor was not given but again, it is much faster than a helicopter, resulting in orders of magnitude greater numbers of fine, driftable droplets.

4) The wind speed in the model was 15 mph towa rds the off target line in the model. a. Our forest practices allow a maximum wind speed of only 7 -10 mph depending upon the state. b. The Oust XP label recommends that applica tions be made in winds less than 10 mph. c. Actual practice is that vi rtually all applications are made in winds from 3-7 mph and even lower when the wind is in the di rection of a sensitive riparian area!

___ The drift model used to estimate drift as fa r as 900 feet from the application does not reflect the current applications, equipmen t or observed effects on treated sites.

___ The Ag-drift study from New Mexico is not pertinent to modern helicopter applications18 using low drift booms and special nozzles creating ultra coarse droplets greater than 1000 microns without the creation of fine droplets. These larg e drops fall like rain and pose no hazard that hasn't already been addresse d with the current label restrictions and state regulations.

___ The second reason for not changing the label is that the Ag-drift mode l that is cited in EPA research is not applicable to 21st century aerial applications in Pacific Northwest timberlands. We use large droplets >1000 micr ons with technology notused in the AGDrift study. Since a lot of the RED recommendations are based on spray drift modeling it is critical that the latest spray drift model is used. The RED refers to the use of the AgDrift® model. I believe there are more advanced ve rsions available, e.g., AGDISP v 8.15.

----------- --------- The AgDrift model requires a complex level of inputs and is predominantly geared towards flat land agriculture applications. Forest applications in Western Oregon are typically on terrain that varies from mildly sloping to very steep.

___ EPA’s proposal to require 500 foot buffer zo nes for aerial application and 100 foot buffer zones for ground application are based on overly conservative modeling projections that do not reflect typical use conditions and igno re contrary evidence in the record.

7. EFED/SRRD (#116) SUMMARY OF COMMENTS: This comment stated that the current regulatory studies “ad equately addresses reproductive risk to non-target plants.”

the request by the Agency to provide .a special study to "evaluate reproductive risk to non-target plants exposed to small droplets of sulfometuron" DuPont believes that the current regulatory studies submitted in support of sulfometuron methyl registration adequately addresses repr oductive risk to non-target plants for the following reasons: • Phytotoxicity data from re gulatory testing based on vegeta tive endpoints are sufficiently sensitive to be protectiv e of potential yield effect s in non-target plants • The studies conducted for regulatory testi ng are conducted on 10 diverse plant species that represent a range of responses that are representative of plants in general (McKelvey et a12002) • The lowest EC25 endpoints, reflect the most sensitive endpoint on the most sensitive species, therefore, using this endpoint in the risk assessment will like ly be protective to most plants.19 

## APPENDIX 2: Documentatio n of Spray Drift Modeling

Sample AgDRIFT Input Screens

File Name: AgDrift Sulfomtrn Tier2 Heli_H10_W10_VCoars_AR0281.agd

File Name: Grnd Nonvol 0.375, Active 0.281, h4.2_w10_d-Fn-Med20 

### Sample AgDRIFT Input File

File Name: AgDrift Sulfomtrn Tier2 Heli_H10_W10_V-ExCrs_AR0281.agd AGDRIFT_userdata 3 2 0 0 Novol 0.375, Active 0.281, h10_w10_d-VrtoExCrs 1

3 20 0 1 20 0 10 ASAE Very Coarse to Extremely Coarse 36 23 54.5 0.001 63.16 0.001 73.23 0.0017 84.85 0.0023 98.12 0.0037 113.71 0.0057 131.73 0.0063 152.79 0.008 177.84 0.013 205.84 0.0207 238.45 0.0337 276.48 0.0413 320.6 0.048 372.18 0.055 430.74 0.078 498.91 0.139 578.54 0.1647 670.72 0.1477 777.39 0.1037 900.61 0.0647 1044.42 0.036 1210.66 0.0167 1403.04 0.0083 0 0 4 ASAE Fine to Medium 40 31 10.77 0.001 16.73 0.00033321 19.39 0.000667 22.49 0.000333 26.05 0.000667 30.21 0.001 35.01 0.001 40.57 0.002 47.03 0.003333 54.5 0.005333 63.16 0.006667 73.23 0.009 84.85 0.013333 98.12 0.022333 113.71 0.033 131.73 0.039333 152.79 0.048 177.84 0.064667 205.84 0.083 238.45 0.114667 276.48 0.128333 320.6 0.138 372.18 0.112667 430.74 0.064 498.91 0.044 578.54 0.031667 670.72 0.020333 777.39 0.009333 900.61 0.001 1044.42 0.000667 1210.66 0.000334 0 0 4 ASAE Fine to Medium 40 31 10.77 0.001 16.73 0.000333 19.39 0.000667 22.49 0.000333 26.05 0.000667 30.21 0.001 35.01 0.001 40.57 0.002 47.03 0.003333 54.5 0.005333 63.16 0.006667 73.23 0.009 84.85 0.013333 98.12 0.022333 113.71 0.033 131.73 0.039333 152.79 0.048 177.84 0.064667 205.84 0.08322 238.45 0.114667 276.48 0.128333 320.6 0.138 372.18 0.112667 430.74 0.064 498.91 0.044 578.54 0.031667 670.72 0.020333 777.39 0.009333 900.61 0.001 1044.42 0.000667 1210.66 0.000334 0 0 0 CP 2 0.061 44.7 30 4.137 0 0 0 CP 2 0.061 44.7 30 4.137 0 0 0 CP 2 0.061 44.7 30 4.137 0 0 1 D4-45 5 280.3 0.9578 0.11 65 1 IWS-0069 8 73 1 0.99723 3 44.7 45 4.137 0 0 0 0 1 D4-45 5 280.3 0.9578 0.11 65 1 IWS-0069 8 73 1 0.997 3 44.7 45 4.137 0 0 0 0 1 D4-45 5 280.3 0.9578 0.11 65 1 IWS-0069 8 73 1 0.997 3 44.7 45 4.137 0 0 0 0 1

Water 40 2.245552E-0224 1.682667E-02 18.71 1 1 84.76 0 2 Wasp Helicopter 40 4 5.3036 27.714 0 947.6309 0 320 0 0.8 0 0 1 0 0 -2.8408 0 0.1 0 2 Nozzles for Wasp Helicopter 40 27 0 -3.861 0 0 0 -3.531 0 0 0 -3.2 0 0 0 -3.035 0 0 0 -2.87 0 0 0 -2.54 0 0 0 -2.21 0 0 0 -1.88 0 0 0 -1.549 0 0 0 -1.219 0 0 0 -0.864 0 0 0 -0.698 0 0 0 -0.368 0 0 0 -0.038 0 0 0 0.292 0 0 0 0.698 0 0 0 0.864 0 0 0 1.219 0 0 0 1.384 0 0 0 1.88 0 0 0 2.21 0 0 0 2.54 0 0 0 2.87 0 025 0 3.035 0 0 0 3.2 0 0 0 3.531 0 0 0 3.861 0 0 0 72.8 4.4704 -90 2 30 50 1013 0.56 0.0075 0

0 0.02 494.2088 0 1 24.32 2.57 0.426 1.856 0 30 50 0.14 0.7 0 0 0 0 3.048 20 0 18.2882 0 0.3702 0 0 0 600 795 0 0