State of the Art in Wind Siting: A Seminar...State of the Art in Siting Seminar Pre-Publication Copy...

STATE OF THE ART IN WIND SITING:

A SEMINAR

Pre-Publication Copy

MEETING PROCEEDINGS October 20-21, 2009

Washington, DC

Photo credit: Tom Maves, Ohio Energy Office

State of the Art in Siting Seminar Pre-Publication Copy of 43

Meeting Proceedings October 20-21, 2009

Table of Contents

Table of Contents .................................................................................................................. 2

Meeting Purpose ................................................................................................................... 3

Welcome and Introductions................................................................................................... 3

Session I: Visual Impacts ........................................................................................................ 4

Visual Considerations: Public Perception, Regulatory Environment and Assessment Methods in the

Eastern U.S. ................................................................................................................................................... 4

Visual Resource Management ...................................................................................................................... 6

Visual Considerations: FAA Obstruction Lighting and Marking for Wind Turbine Farms ............................ 9

Session II: Acoustic Considerations ...................................................................................... 11

Wind Turbine Sound ................................................................................................................................... 11

Sound Propagation...................................................................................................................................... 12

Calibration Studies and Sound Modeling .................................................................................................... 14

Questions for the Acoustics Panel .............................................................................................................. 15

Panel Discussion on Research Priorities Relating to Visual and Acoustic Impacts ..................................... 16

Session III: Radar Interference ............................................................................................. 18

Introduction to the Issues ........................................................................................................................... 18

Federal Agency Perspectives and Research ................................................................................................ 20

Candidate Solutions .................................................................................................................................... 24

Research Needs Identified by Panel ........................................................................................................... 28

Session IV: Property Values ................................................................................................. 29

Questions on Property Values .................................................................................................................... 31

Session V: Icing Considerations ............................................................................................ 32

Appendix A: Seminar Agenda............................................................................................... 34

Appendix B: Seminar Participants ........................................................................................ 38

Appendix C: Meeting Sponsors ............................................................................................ 43



Meeting Purpose

The National Wind Coordinating Collaborative (NWCC) teamed with the National Renewable Energy

Laboratory (NREL) and the Idaho National Laboratory (INL) to convene leading researchers, developers,

policymakers and regulators in a discussion about the state-of-the-art in wind energy siting.

Welcome and Introductions

Abby Arnold, NWCC Facilitator, welcomed attendees to State of the Art in Wind Siting. She explained

that this meeting aimed to provide an update on the information presented in 2005 at Technical

Considerations in Siting Wind Developments1 and to examine emerging issues in relation to wind siting.

Ms. Arnold encouraged attendees to take advantage of the wealth of knowledge and experience present

in the room. She highlighted opportunities for participant discussion following each session in which

attendees would be able to enrich the conversations begun during speaker panels. Ms. Arnold also

noted that attendees represented a variety of sectors and capabilities and, by working together, could

identify additional research and coordination needs and mutual solutions for many of the problems that

would be discussed during the meeting.

After participant introductions, Ms. Arnold noted that the workshop would examine five primary topics

in wind siting:

Visual impacts

Acoustic impacts

Radar interference

Property values

Icing

1 Proceedings from Technical Considerations in Siting Wind Developments are available at:

http://www.nationalwind.org/assets/blog/FINAL_Proceedings.pdf.

http://www.nationalwind.org/assets/blog/FINAL_Proceedings.pdf



Session I: Visual Impacts

Visual Considerations: Public Perception, Regulatory Environment and

Assessment Methods in the Eastern U.S.

Matt Allen, Saratoga Associates, is a landscape architect who has worked with visual

impact assessment for over twenty years. His experience has focused primarily in the

Northeast and Mid-Atlantic regions of the United States.

Mr. Allen noted a few factors that impact how wind facilities are viewed in the eastern U.S. Open

spaces are valued at a premium because of land scarcity. Much of the east has been highly developed,

leaving less scenic open space proximate to cities. Additionally, wind development tends to be closer to

residential areas in the eastern U.S., where population density in counties where wind projects are

located is much greater than wind development areas in the western or central portions of the U.S.

Mr. Allen noted a conflicting land ethic in the East: there is a significant presence of “NIMBYism.”2 To

many, wind turbines are perceived as an unwanted "industrialization" of the landscape. Mr. Allen

suggested that this perception may differ by personal values and land ethic. That is, those who visit

rural areas or own rural property to escape over-developed urban conditions often view wind turbines

as an unsightly disturbance to a pastoral landscape. On the other hand, those who reside full time in

rural areas may view the landscape as a working landscape – to be used for agriculture and other uses;

to these people, renewable energy development visible on the landscape is a positive sign of economic

growth.

Conflicts pertaining to claims of visual effects often arise in the early stages of the project development,

before facts concerning project visibility are known. Wind energy developers are often put on the

defensive by unsubstantiated claims of adverse visual impact resulting in controversy and delay. Mr.

Allen suggested that developers might avoid these delays by engaging the local community in

conversations about visual impacts earlier in the development process. He encouraged developers to

provide the public with factual information at an early stage in planning. This should include clear

predictions of the expected impacts, allowing the public to determine whether concerns exist. Such

early consultation removes the guesswork and speculation that often plagues late-stage visual

assessment. In addition to providing factual information in a timely manner, Mr. Allen encouraged

developers to solicit feedback in a public forum and work with the local community to address concerns.

2 “NIMBY,” short for “Not In My Back Yard,” is a term that is used negatively to characterize opposition by residents to a

proposal for new development within the proximity of their homes or places of work.

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Siting policy differs by locale in the eastern U.S. Developers are usually required to conduct a visual

resource assessment (VRA) in order to receive permits from the state and county. Mr. Allen explained

that questions a VRA’s should address include:

What is being proposed?

In what visual context will it be located?

From where will it be visible?

What visually sensitive places will be affected?

What will it look like?

Will the project will blend in with or be in contrast to the current landscape?

A VRA must also identify mitigation opportunities, including decommissioning3 and consideration of

visual offsets4.

However, few states or counties prescribe a particular method for VRA’s. Furthermore, methodologies

for VRA’s are generally based on research from the 1970s and 1980s that fails to consider the unique

impact of wind facilities; additional research is needed to adapt these methodologies for wind

development.

Mr. Allen highlighted some of the recent technological advancements available to predict visual impacts.

He explained that pairing geographic information system (GIS) technology with databases of land cover

information has enabled more realistic modeling of impacts. Previous modeling resulted in a “bare

earth” analysis, which did not take into account the ability of tree cover to minimize view shed impacts.

Mr. Allen also reported that Light Detection and Ranging (LIDAR) technology helps to resolve accuracy

issues associated with more traditional analyses.5 LIDAR produces more accurate assessments of

structure and vegetation dimensions. Unfortunately, the use of LIDAR is currently limited by a

somewhat prohibitive cost associated with the acquisition of data, costs will likely decrease in the

future.

Local communities often express interest in previewing impacts prior to development. Video

animations can be time- and cost-intensive to produce, but provide a very realistic prediction of

impacts. Animation made through a video composite method, where wind turbines are modeled onto

existing video footage, is available to developers. This type of animation removes the need to model

the existing landscape and can be produced more quickly and cheaply.

Questions on Visual Considerations in the Eastern U.S.:

Question: Simulations are useful, but what can a developer do to address the concerns of stakeholders

who just don’t like the way a proposed facility will look?

3 Removal of structures and restoration of landscape at the end of useful life of the project.

4 Correction of an existing unsightly condition.

5 Mr. Allen included visualizations using traditional technology and LIDAR in slides 20 and 21 to illustrate the improvement

LIDAR offers.



Answer: In these circumstances, it is important to examine local guidance or regulations on the

importance of the landscape. Landscapes of statewide importance should be privileged over an

individual’s backyard view.

Question: Has improved visualization technology had any impact on rates of public acceptance of

proposed wind facilities?

Answer: It does provide better data and improves the communication between developers and

communities. Communities appreciate data they can trust. However, improved data does not always

lead to increased permitting.

Visual Resource Management

John McCarty, Bureau of Land Management, is the BLM’s Chief Landscape Architect

and the national lead on Visual Resource Management (VRM).

Mr. McCarty explained that Bureau of Land Management (BLM) manages 256 million surface acres of

Western landscape and 700 acres of subsurface mineral estate in the United States. BLM administers

surface use under a multiple-use management mandate, among them: recreation, forestry, livestock

production, energy development, mineral mining, and communications. Mr. McCarty noted that the

variety of uses can occasionally generate conflict. Further, as communities continue to expand, the

buffers between urban and federal land shrinking with increasing populations that be sensitive to

changes to the BLM landscapes. As a result, the development of renewable energy (wind, solar,

geothermal) on rural BLM landscapes has generated levels of public concern. With respect to wind

energy development, the Wind Energy Programmatic Environmental Impact Statement (PEIS) found that

approximately 20 million acres of BLM land were potentially suitable for wind energy development.

Subsequent PEISs have or are in the process of evaluating potential for geothermal and solar energy

development that will substantially add to the acreage disclosed in the Wind Energy PEIS.

BLM’s VRM program maintains four principles:

Inventory and describe the existing visual environment

Designate and comply with visual resource management objectives

Utilize good design principles to minimize visual contrast of new development in natural settings

Conduct an visual assessment of the proposed changes, document visual contrast and mitigate

impact to meet the designated Visual Resource Management Class objectives

The Federal Land Policy and Management Act, 1976 (FLPMA) requires the BLM to manage for and

protect scenery values. In response, the BLM structured the VRM policy and procedures, which all

permitted surface disturbing land use is subjected to, including wind energy development. The BLM

manages scenery through inventorying visual values and then designating prescriptive management

objectives. Inventoried visual values are defined within Visual Resource Inventory (VRI) Classes I – IV

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http://www.nationalwind.org/assets/blog/John_McCarty.pdf



with Class I and II having the highest value, Class III moderate value, and Class IV lowest value. These

classifications serve as information used in land use decision making and baseline data for analyzing

impacts.

Visual Resource values are inventoried through evaluating scenic quality, sensitivity level, and distance

zones. Scenic quality is based on visual variety within the landscape by measuring factors such as

landform, color, vegetation, scarcity, cultural modifications, influence from adjacent scenery, and

presence of water. Sensitivity levels are determined by considering the presence of recreational

settings, important cultural or historic landmarks, legally protected landscapes, travel corridors, users,

amount of users, adjacent land uses and more. The VRI also considers visibility at various distances

from where people customarily view the landscape. Visibility distance ranges are divided into

foreground/middle-ground (out to 5 miles); background (5 to 15 miles); seldom seen (beyond 15 miles

or hidden landscapes within the other distance ranges).

The VRI values, land uses and desired outcomes are all considered when designating Visual Resource

Management (VRM) Classes, which are determined during the land use planning process. VRM Classes

dictate the prescriptive visual management objectives. The classifications range from VRM Class I to IV,

with VRM Class I being the most constraining and VRM Class IV as the least.

Mr. McCarty made the point that the BLM does not judge the subjective aesthetics of wind energy

development, but instead objectively measures the visual contrast. Conformance of proposed

developments (wind energy or other) to the VRM Class objectives is determined through measuring

their potential contrast with the landscape setting. Contrast rating procedures follow the BLM’s

systematic process outlined in Handbook 8431-1 “Visual Resource Management - Contrast Rating” that

compares the design elements (form, line, color, texture, scale) of the project with the characteristics of

the landscape. This analysis considers ten factors that may influence the visibility of landscape

modifications: distance, angle of observation, length of viewing time, size and scale, season of use, light

conditions, recovery time, spatial relationships, atmospheric conditions, and motion. With these factors

in mind, the analysis then evaluates the contrast created within the landform, vegetation and other

structures found within the landscape and ranks the contrast as none (VRM Class I), weak (VRM Class II),

moderate (VRM Class III) or strong (VRM Class IV).

Typically, the more scenic and publically sensitive the landscape, the more protection within the BLM

land use plans. The more scenic landscapes are often composed of vegetative and topographical

variations including a series of ridgelines defining the visual horizons. These ridgelines may also be

suitable locations for optimal wind turbine placement creating potential conflict between resource uses.

Consideration for both protecting visual values and advancing wind power development within high

valued settings will lead to challenging land use decisions. If determined to adjust the VRM Class

through a land use plan amendment or revision from a more protective designation to one that permits

significant visual change of the landscape, the BLM still has a legislated obligation to require projects to

be visually mitigated to reduce visual contrast.



While landscapes with more variety are typically inventoried to have higher visual values, these same

landscapes may also provide an opportunity for facility concealment. Distance from viewers is a key

factor in visibility and contrast assessment. Mr. McCarty stressed the need to reassess the relevance of

the BLM’s VRM distance ranges (foreground/middle-ground; background; seldom seen discussed

earlier) for large vertical scale development such as wind turbines and other similar scaled facilities. He

indicated that BLM is currently investigating how distance influences visual discernment of large scale

vertical development and define more practical ranges. These findings are intended to help both the

BLM and industry better understand the influence of distance on visibility, which can be factored into

land use management decisions, project site selection and facility design.

The BLM is evaluating new methods for mitigating visual impacts associated with wind energy

development. For instance, BLM is currently collaborating with the Federal Aviation Administration

(FAA) evaluating the suitability of a technological alternative that may allow color treating turbines to

help reduce visual contrast while still allowing FAA to achieve its mission of air safety. Additionally, BLM

is developing and evaluating the application of advanced camouflage technology that may help reduce

visual contrast of other smaller scale ancillary wind energy facilities. Mr. McCarty also noted that

preservation of existing vegetation or implementing adaptive landform grading and appropriate

revegetation strategies can be utilized to mask lower profile ground installations.

BLM will soon begin collaborating with the U.S. Department of Energy and Argonne National

Laboratories to develop a visual risk assessment methodology. BLM has already developed a Visual

Resource Management/Inventory data standard and geodatabase. For more information, contact him

at: [email protected].

Questions on Visual Resource Management:

Question: What training is available for BLM field offices regarding the Visual Resource Management

methodology?

Answer: BLM offers two 5-day courses a year and numerous on-demand 2-day short courses throughout

the year. These 2- or 5-day courses are typically limited to 35 people. Training is available to BLM

employees, other agencies personnel, federal contractors, industry and industry consultants. Feel

free to email [email protected] for updates on scheduled training opportunities.

Question: Has BLM begun discussions about how it will handle the development of transmission on BLM

lands in the West?

Answer: BLM has completed a West-wide Programmatic EIS establishing corridors in which transmission

development would have the least visual impact. While transmission developers are not required to

site within these corridors, approval decisions will be expedited more rapidly within the corridors. All

transmission right of way permit applications are subject to NEPA with decisions based on

environmental impact analysis.

Question: Some landscape architects believe that structures moving with nature are more visually



acceptable than static structures. Does BLM use this to evaluate the visual impact of wind turbines?

What about static transmission?

Answer: BLM does factor movement into its analysis, but has found that movement appears to attract

attention. Transmission may be more visually acceptable, depending on its location. Collocating

transmission lines along natural lines within the landscape will help reduces visual contrast, as well as

placing lines where there is a landscape backdrop and color treating transmission towers to visually

blend with the background.

Question: How are birds affected when turbines or transmission is camouflaged?

Answer: It is not likely that multiple color camouflage technology would be applied to wind turbines,

but rather to the lower profile ancillary facilities associated with wind energy development.

However, the BLM is evaluating single color application to help large vertical development to visually

recede more into the background, which may be used for wind turbines and transmission towers.

Appropriateness is considered on a case by case basis, and with collaboration with FAA on facilities

that fall within their authority.

Visual Considerations: FAA Obstruction Lighting and

Marking for Wind Turbine Farms

Jim Patterson, Federal Aviation Administration, is an Airport Safety Specialist with the

Federal Aviation Administration’s Airport Safety Technology Research and Development

Sub-Team at the FAA’s William J. Hughes Technical Center in Atlantic City, NJ. He

manages research projects in visual guidance, aircraft rescue and firefighting, airport design safety, and

operation of new large aircraft.

Mr. Patterson noted that an FAA approved lighting and marking plan is required for any structure

exceeding 200 ft. in height. He reflected that, a few years ago, the FAA realigned its standards and

process for wind facility assessment. Previously, FAA had required that each turbine in a wind facility be

outfitted with two lights (the redundancy served as a precaution in the event that one of the bulbs

burned out). However, lighting requests from developers and other agencies were very inconsistent –

some projects used red lights, some used white, and others used flashing lights. FAA developed a new

standard that was published in an FAA Technical Note in 2006, and later adopted in 2007 that efficiently

and effectively lights wind facilities while addressing the needs of the other parties involved.

The FAA conducted airborne evaluations of 11 facilities with varying patterns of turbines. This survey

concluded that:

Safety requires that the outer turbines be lit, but the interior clusters do not pose any threat to

aviation.

The separation gap for unlit turbines should not exceed ½ statute mile.

Simultaneous flashing or strobe lights (either red or white) are preferable.

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http://www.nationalwind.org/assets/blog/Patterson_Public.pdf



Red flashing lights (L-864) of 2,000 candelas are the most preferred.

If requested, white strobe lights should be used alone (and not with red lights).

Meteorological towers often provide optimum placement for lighting.

Daytime lighting can be omitted if the turbines are painted white.

As long as the site is regularly maintained, there is no need for a second bulb backing up each

light.

Light fixtures that are mounted to the turbine should be placed on the turbine housing, where

the tower cannot block the light in any direction.

To test these conclusions, FAA permitted a wind facility in Lawton, Oklahoma, utilizing these criteria.

The new approach proved to be an improvement and was implemented into the 2007 FAA guidelines.

Mr. Patterson also shared some current FAA activities. FAA recently announced approval to use Audio

Visual Warning Systems for obstruction lighting on a case by case basis. Using these systems, a project

could remain unlit except when the radar component of the system identifies an airplane in the vicinity.

When an airplane is observed, the system begins to flash the facility’s lights and also broadcasts a radio

warning to the approaching plane.

In addition, the FAA has begun working with the wildlife community to evaluate obstruction lighting

standards for other infrastructures, including communications and met towers. He also noted a joint

project with West Point designing a turbine that may reduce or avoid radar interference issues.

Because of time restrictions, questions for Mr. Peterson were saved for the joint visual/acoustic panel

following Session II.



Session II: Acoustic Considerations

Wind Turbine Sound

Mark Bastasch, CH2M Hill, is a registered acoustical engineer with CH2M HILL. Mr.

Bastasch’s acoustical experience includes preliminary siting studies, regulatory

development and assessments, ambient noise measurements, industrial

measurements for model development and compliance purposes, mitigation analysis,

and modeling of industrial and transportation noise.

Mr. Bastasch provided some background on acoustical considerations associated with wind power. He

began with the basics, explaining that sound is a pressure fluctuation above and below atmospheric

pressure. Because sound spans many orders of magnitude in terms of energy and pressure, sound is

measured in decibels, a logarithmic unit of measurement. To illustrate this point, Mr. Bastasch shared a

chart illustrating a range of noises and their corresponding decibel and energy measurements (slide 3).

Mr. Bastasch then distinguished between sound pressure and sound power. He explained that the

pressure of a given sound will fluctuate depending on the recipient’s distance from the source, while

power is independent of distance.

The threshold of hearing for low frequency noise is louder than high frequency noise (a low frequency

noise needs to be louder to be heard – for example, 30 dB at 1000 Hz is equally as loud as 65 dB at 40

Hz). However, once above the hearing threshold, a smaller increase in low frequency noise is required

to achieve a similar increase in loudness (for example: an increase of 10 phons, a measure of loudness,

a 10 dB increase in volume is required at 1000 Hz, where as only 5 dB is required at 40 Hz). Louder

turbines require larger setback distances to achieve the same sound level, which can affect the potential

size and productivity of a facility. Therefore, developers have an economic incentive to utilize quieter

turbines.

Blade movement causes the dominant source of noise at wind facilities. This source of noise is referred

to as “aerodynamic generation,” and is generally proportional to tip speed. Mechanical sources,

including the gearbox, generator, yaw drives, and cooling fans also contribute to the overall noise

produced by the facility. Traditional sound mitigation approaches (e.g. a barrier surrounding the

turbine) cannot be implemented because most would also hamper energy production.

Many organizations – both public and private – have begun researching the issue of aerodynamic noise.

Some of these organizations are listed on slides 12 and 13 of Mr. Bastasch’s slides. Additionally, several

locations in the U.S., Denmark, and the Netherlands have acoustical test facilities.

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As they plan facilities, developers will identify noise sensitive areas, such as homes and schools. They

will also note setback requirements associated with roads, property lines, and protected areas. These

constraints will be overlaid on a wind resource map to begin constructing the initial turbine layout.

Using this layout, along with sound power level data for the proposed turbines, a developer will then

develop an acoustical model to determine whether predicted sound levels will create trouble for the

noise sensitive areas. The results from these predictions inform the iterative refinement process of

turbine layout.

Mr. Bastasch explained that turbine vendors can use a number of tools to measure sound at the

proposed facility, including acoustic arrays, parabolic microphones, and International Electrotechnical

Commission (IEC) methods. However, he noted that long-term environmental measurements require

different methods, for which he recommended the use of oversized or secondary windscreens to collect

wind speed data near ground level and hub height.

Mr. Bastasch encouraged developers to engage with the local community during this time of planning.

He noted that such engagement would allow developers to understand concerns, including non-acoustic

factors, in the community. He suggested that a field trip to an operating wind facility could help

community members understand potential effects and also noted that it is important to recognize that

silence is not a realistic expectation nor is it required from other sources of environmental sound.

Interacting with communities can also allow for full communication of benefits associated with a facility.

It will also permit developers to coordinate start-up and construction stages to avoid conflicts with the

community. Mr. Bastasch also encouraged developers to remain responsive to the community following

the completion of the facility. For instance, complaints may indicate a malfunction or maintenance

need.

Mr. Bastasch suggested that additional effort is needed to develop certified equipment or standardize

measurement approaches. A uniform standard of practice would improve comparability of data.

Questions for Mr. Bastasch were held for the end of the panel and follow Mr. Kaliski’s presentation.

Sound Propagation

Bo Søndergaard, DELTA, is a senior consultant in DELTA’s Acoustics Department. He

possesses more than 20 years of experience as a consultant on environmental noise

measurements, predictions and assessment. Mr. Søndergaard discussed:

Results from his research on low-frequency noise produced by turbines

An overview of his work on the IEC methods

A new noise propagation method

Wind shields

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Mr. Søndergaard has been investigating low-frequency noise produced by turbines. Larger wind

turbines turn more slowly than smaller turbines, meaning that all the rotating parts turn more slowly.

The gear box transfers the slow rotation of the rotor into the faster rotation of the generator. The gear

box generates noise at discrete frequencies, which are heard as tones (this can cause annoyance). For

smaller wind turbines, these tones were at frequencies around 400 Hz. For modern wind turbines, these

tones occur at frequencies below 200 Hz. The sound spectrum (the distribution of high and low

frequencies) does not seem to differ between large and small turbines.

Some controversy exists about the potential health effects of infrasound (sound at frequencies lower

than 20 Hz). Infrasound is inaudible to the human ear unless there is very high sound pressure (this

does not occur for modern wind turbines).

There are three steps involved in predicting low-frequency noise: obtaining reliable measurements,

modeling noise propagation, and measuring sound insulation at nearby homes. For the first step –

obtaining reliable measurements – Mr. Søndergaard recommended using the IEC methods for sound

emission mentioned by Mr. Bastasch. This involves using an extra wind shield on the microphone to

reduce wind induced noise in the equipment. The IEC 61400-11 standards, which were developed in

1998 and revised in 2002, help to measure the tonality of wind turbine noise and provide results at

integer wind speeds from 6-10m/s. Amendments to the standards were finalized in 2005. Future

changes include replacing a regression analysis with a bin-analysis, using hub-height wind speed as the

reference wind speed, and shortening averaging time, among other changes. There are not consistent

standards for sound immission (which the European Environment Agency defines as “The introduction in

the environment of noise deriving from various sources that can be grouped in: transportation activities,

industrial activities and daily normal activities”).

For the second step in predicting low-frequency noise -- modeling noise propagation -- Mr. Søndergaard

suggested using the NORD 2000 method, as many other propagation measures are ineffective for low-

frequency sound. The ISO 9613-2 model is typically used to predict wind facility noises, but this model is

best suited to sources closer to the ground than wind turbines. It is also best suited for low wind

speeds. Finally, it offers only two input options for modeling the terrain (hard or soft). Mr.

Søndergaard instead recommended using the NORD 2000 model, which can take complex terrains into

account. Since terrain can cause the predicted decibel level to significantly vary (more than 5 decibels),

this is an important component for predictive accuracy. The NORD model can predict both upwind and

downwind noise propagation, unlike the ISO model, which is best for downwind conditions. The NORD

model can also predict propagation under a number of weather conditions, rather than assuming one

fixed weather condition.

For the third step -- measuring sound insulation at nearby homes -- Mr. Søndergaard suggested using

the ISO standards for microphone positioning. These measurements also help to identify possible

options for mitigating noise inside individual homes.



There is significant motivation to improve prediction capabilities, especially for sound propagation. This

motivation stems from an increase in the size and number of wind facilities. Because of these increases,

more people are exposed to noise from turbines.

Mr. Søndergaard also discussed new technologies with wind shields. He explained that wind shields

remove the noise that is generated solely by the presence of the measuring equipment (much like wind

in one’s ear changes sound depending on a person’s position). They can also reduce the skewed

measurements that occur in response to low frequency pressure variations in wind. Wind shields do

cause some loss of acoustical noise, but explained that appropriate adjustments can be made to

compensate for this loss.

Questions for Mr. Søndergaard were held for the end of the panel and follow Mr. Kaliski’s presentation.

Calibration Studies and Sound Modeling

Ken Kaliski, RSG, Inc., is Director of Resource Systems Group's Environmental Services

Division. He has been consulting on the noise impacts of wind energy systems for over

15 years. He is a licensed professional engineer, is Board Certified through the Institute

for Noise Control Engineering (INCE), and serves as Vice President for Board Certification at INCE. He is

also a member of the Acoustical Society of America and his firm is a member of the National Council of

Acoustical Consultants.

Mr. Kaliski explained that developers often use modeling in the pre-development stages to assess

potential acoustical impacts from turbines. However, standard algorithms for measuring sound were

not originally designed to assess turbines, creating some difficulty in accurately predicting acoustic

impacts at wind facilities. To improve predictions, studies have been done to improve predictions done

using the ISO standards. In addition, other models have been developed in Europe, as previously

discussed by Bo Søndergaard. These models contain adjustments for wind speed and direction, as well

as atmospheric stability.

Because the ISO model assumes that wind speeds are between 1-5 meters per second, Mr. Kaliski

explained that calibration is needed for higher wind speeds. The ISO method gives standard errors for

sound propagation with sources up to 30 meters from the ground, which does not accurately assess

sound produced by the industrial turbines commonly used by developers today, which can exceed 80

meters in height at the hub. Because wind sound can be refracted in different directions depending on

wind shear, temperature, and wind direction, variations in these must also be taken into account.

Ground softness and humidity levels can account for some absorption of noise, creating yet another

consideration in the assessment phase. Although calibration can be done for different levels of ground

hardness, the ISO method does not account for the inversion of noise which occurs over water, meaning

that this method may need to be adjusted when measuring noise at offshore sites.

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presentation





Mr. Kaliski discussed a calibration study in Kansas in which 67 turbines were modeled during 162 10-

minute increments in the evening and early morning, when sound impacts are usually greatest due to

increasing temperatures and less background noise generated by other activities. The downwind terrain

was flat and porous, but the total area contained numerous terrain types. The study found that the ISO

method can significantly underestimate impacts if soft ground parameters are used. However,

adjustments to the ground and meteorological factors included in the model can account for this

concern.

In addition to this research, Mr. Kaliski showed how sound can be modeled not just for one hour, but

over the course of the year, by using actual meteorological data (e.g. temperature, wind speed and

direction, cloud cover, and wind shear). The data showed that annual impacts are related to not only the

number of turbines, but how they are situated around a property.

Mr. Kaliski also offered a few recommendations for further research:

Additional calibration studies are needed

Directly measuring ground impedance to understand how much sound terrain absorbs. Testing

this methodology over other terrain types, monitoring sound over a large range of wind speeds,

and conducting calibration studies on new models like Harminoise and Nord 2000.

Questions for the Acoustics Panel

Question: Do meteorological assessments typically include humidity?

Answer: Most met towers do not measure humidity but could be outfitted to do so.

Question: Given the new Nord 2000 model and Mr. Søndergaard’s reassessment of the ISO model,

should current setback distances be changed? Also, do these studies offer insight into who might be

most affected by noise/most likely to complain?

Answer: The ISO model has pretty accurately predicted noise at shorter distances, which affects

setbacks. However, the model has struggled more with predicting perceived noise at larger distances.

The studies do not directly identify who might be most affected, since annoyance is multi-faceted.

Investigations into complaints about noise often reveal annoyances about other issues.

Question: Are there recommendations about how to mitigate noise level impacts on wildlife?

Answer: There is some concern about how noise might affect bird leks (areas where male birds

congregate to attract females). However, impacts are very species specific; for instance, large

mammals tend to habituate to the impacts. When assessing noise impacts and potential mitigation

strategies, it is important to consider other potential industrial activity in the area and the impacts

from that. Peter Stiles at Keele University has done some good work developing measurements for

evaluating ground vibration effects at a nuclear test ban monitoring facility.



Question: What is the reaction to communities asking about health impacts?

Answer: Some people have raised concerns, but there has also been some misunderstanding of the

technical literature and the metrics used, especially regarding infrasound and low frequency noise.

It’s important to keep in mind the broader noise level from other sources. It’s worth noting that the

topic of health impacts from turbine noise brings together two very disparate worlds – medical

science and engineering. Medical scientists do not appreciate acoustical engineers making definitive

statements about medicine and vice versa. These two worlds could benefit from collaboration. This

collaborative opportunity must be facilitated, because it is unlikely to happen on its own.

Panel Discussion on Research Priorities Relating to Visual and Acoustic

Impacts

Matt Allen (Saratoga Associates), Mark Bastasch (CH2M Hill), Ken Kaliski (RSG, Inc.), John McCarty

(Bureau of Land Management), Mike Pasqualetti (Arizona State University), and Bo Søndergaard (DELTA)

Mike Pasqualetti, Professor in the School of Geographical Sciences and Urban Planning at Arizona State

University, began the panel with a short presentation on social barriers to wind energy development.

Pointing to some experiences of protest against wind facilities around the world, Mr. Pasqualetti asked

whether “we are worrying about the right things?” He explained that quality of life issues generally

comprise the root of protests against wind.

Panel participants then discussed priority research needs and best practices:

Mr. Bastasch encouraged the expansion of community involvement as a way of gaining social

acceptance. He explained that communities need to feel that developers understand their

concerns and appreciate community input.

Mr. Søndergaard noted a need for more annoyance studies similar to those in Sweden and

Holland. He recommended that these be improved and expanded, with an emphasis on

acoustics.

Mr. Kaliski asserted the need to conduct more dose-response studies, in which observed health

impacts are tied to the levels of noise the subject encounters. He also recommended additional

calibration studies to enhance model accuracy.

Mr. McCarty suggested that there is a great need for improved education within regulatory

agencies, the industry, and the public. He noted the importance of consistency in educating

these sectors to improve communication between them.

Mr. Allen reflected that many consider “aesthetics,” as it relates to wind, to include only the

appearance of wind facilities and turbines. He suggested that, instead, that term should also

include the improved air quality associated with the use of clean renewables when displacing

the use of fossil fuels.



Mr. Pasqualetti encouraged research into the social and behavioral aspects of energy use. He

noted a recent Congressional bill that would, if passed, establish a new post at the U.S.

Department of Energy to look at behavioral aspects of energy use and demand.

Audience members also suggested the following:

Simulations of predicted sound levels would be useful to communities seeking information

about a potential wind project in their area.

Developers and regulators need to think about how to communicate with the public about

shared benefits.

At present, only the owner of the property where the turbines are sited profits from the

turbines. However, those on adjacent land plots may experience some visual or acoustic effects.

Direct and indirect benefits should be experienced more equally.



Session III: Radar Interference

Gary Seifert, Idaho National Laboratory, moderated the session on radar interference from wind

facilities. Mr. Seifert is a senior program manager at the laboratory, where he has worked since 1979.

He has responsibility for multiple technical tasks for the U.S. Air Force, U.S. Department of Energy, U.S.

Navy, and NASA. Mr. Seifert is also currently involved in studies for multiple Department of Defense

wind projects and leads a technical wind radar interaction project for the U.S. DOE.

The panel would cover current research on wind-radar interaction and current collaboration needs. The

panelists would attempt to identify the concerns of their respective agencies and highlight technical

solutions under development.

Introduction to the Issues

Mr. Seifert introduced Geoff Blackman, Westslope Consulting, who consults with many of the national

laboratories, wind developers, and the American Wind Energy Association on wind-

radar issues. Mr. Blackman works with developers who are seeking approval to

construct wind farms that are on hold because they have the potential to interfere

with radar and/or air traffic control operations. This work involves identifying impacts, outlining

mitigation techniques and strategies, modeling, simulation, data analysis, optimization, and defining and

testing software and/or hardware changes. Mr. Blackman has also provided support to Idaho National

Laboratory to further the understanding of impacts and existing and potential mitigation techniques and

to the Air Force during the ARSR-4 wind turbine interference and mitigation testing at King Mountain,

TX.

Mr. Blackman explained that the rapid rate of wind energy expansion has highlighted coordination

needs relating to wind and radar. In 2008, approximately 4,000 turbines (totaling 830,000 MW in

capacity) were installed, and 2009 was on track to double that installation. However, developers also

noted that a significant portion of planned wind facilities have been held up, deferred, or abandoned

due to concerns about interference with Federal Aviation Administration (FAA), Department of Defense

(DOD), Department of Homeland Security (DHS), and National Oceanic and Atmospheric Administration

(NOAA) radars.

Goals from the U.S. Department of Energy, which has proposed a scenario in which 20% of the nation’s

electricity could be obtained from wind energy by 2025, would require installation of up to 16,000

turbines per year. The President has proposed an even stronger goal – 25% wind by 2025. Mr.

Blackman asserted that this degree of growth cannot occur without addressing the issues that create

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the above hold-ups, deferrals, and abandoned projects. He suggested that these issues can only be

resolved through coordination between the industry and federal agencies.

Mr. Blackman explained that wind facilities visible to radar can prevent detection of weather or planes

flying over the facility. Turbines can also appear as false indications that can be misconstrued as real or

threat aircraft. Finally, wind facilities can result in corrupt data, especially weather data, in which

turbines can appear as weather patterns or mask actual weather. These potential impacts cause

concern for sensitive areas or when large areas will be affected. Yet, Mr. Blackman noted that there is

no standard for what constitutes acceptable vs. unacceptable impacts. For this reason, decisions to

delay, defer, or reject a project are highly subjective.

When proposed projects are expected to cause interference, developers and regulators may consider

mitigation measures. However, the criteria for what constitutes sufficient mitigation are also quite

subjective. Furthermore, mitigation options are somewhat limited at present, with many promising

technologies not expected to be market-ready for another decade. Other possible measures are

obstructed by limited funding and agency staffing.

The project approval process also poses a challenge, with regulators entering the conversation during

late stages of wind facility planning. Mr. Blackman indicated that a standardized method of engaging

agencies early in the process would assist the industry in its planning. Additional needs include:

Modeling capabilities that would provide objective and timely evaluations;

Sufficient numbers of trained agency personnel;

Standardized operational requirements to help distinguish between acceptable and

unacceptable impacts and to justify decisions to defer or terminate the project; and

Funding for mitigation research and development.

Mr. Blackman offered a brief history of the recent U.S.-based efforts to address wind-radar issues. In

2005, the U.S. Congress mandated a Department of Defense (DOD) study on the subject. The

subsequent report was limited in its analysis of radar types and proposed mitigation strategies, but

committed DOD to conduct additional research. Beginning in 2007, the FAA and DHS collaborated to

provide online information on long-range radar systems, NEXRAD, and DOD flight paths to help industry

in its planning. A series of other forums and problem-solving workshops have included industry and

government representatives, including:

The annual WINDPOWER conference conducted by the American Wind Energy Association

(AWEA)

The 2008 FAA Competition for the Skies Conference, at which a number of agencies and the

industry mutually agreed to collaborate on research and development of mitigation options

A 2009 meeting between U.S. and British industry and agency counterparts to discuss the recent

UK Memorandum of Understanding between British agencies and industry, which established a

mechanism for early agency screening of proposed facilities

And a number of other examples (see slides 7-11)



Federal Agency Perspectives and Research

Kevin Haggerty, Federal Aviation Administration, is the Air Traffic Organization’s Manager of

Obstruction Evaluation and is responsible for determining the effect that objects have on navigable

airspace. In 2004, he served as the U.S. State Department’s FAA liaison to the Republic of Iraq’s General

Establishment for Civil Aviation. During his service, he helped to establish Iraqi control of the Baghdad

International Airport and to enable civilian, reconstruction, and humanitarian flights to and from Iraq.

Mr. Haggerty began with a series of examples of wind-radar conflicts. In one instance in Illinois, U.S.

Senators delayed approval of FAA and DOD political appointments in response to a delay by those

agencies in approving a proposed wind facility. He noted, with some optimism, that this instance did

raise awareness of wind-radar concerns within the leadership of the two agencies. He explained that

buy-in by agency leadership is key to enabling programmatic changes to FAA’s approach to evaluating

wind facilities.

Mr. Haggerty noted that many types of radar are affected by wind energy. He asserted that

collaboration will be necessary to understand and address the full scale of the issue, which will only

increase given aggressive goals for renewable energy development. He explained that the FAA has

expressed interest in creating an advisory workgroup consisting of representatives from agencies and

industry. He envisions that the workgroup would develop a memorandum of understanding identifying

key research needs and funding resources to accomplish that research.

Mr. Haggerty expressed optimism that the leadership of agencies like FAA and DOD will provide the

support and direction required to sufficiently address the issues.

Russell Wright, Department of Homeland Security, shared information about DHS’ work on wind-radar

interference. Mr. Wright serves as a Program Manager under the Executive Director, Operations, within

Customs and Border Protection, Office of Air and Marine (OAM). He is assigned to the Long-Range

Radar Joint Program Office (JPO) located at Langley AFB, VA, where he supports the office’s mission to

ensure that reliable primary long-range radar systems and associated air navigation, surveillance, and

communications systems are maintained.

Mr. Wright explained that the JPO consists of DHS and DOD staff, since both organizations face similar

mandates regarding long-range radar. He asserted that both organizations support renewable energy

development but noted that DOD and DHS’ mandate – to enhance detection and monitoring capabilities

for “low and slow observables”—sometimes competes with the nation’s goals for expanding renewable

energy production

The agency reviews projects within two different contexts – technical and operational. While a radar

facility might face a major technical impact from a proposed wind project, mitigation might be feasible if



impact to overall radar operations is minimal. Conversely, a proposed wind facility might pose a

minimal technical threat to existing radar, but might be rejected because the radar is already

compromised by other obstacles.

Mr. Wright responded to the common belief that next generation radar technologies will eradicate

many of the current wind-radar issues. He argued that these technologies are unlikely to be available in

the near future or in the quantities needed. If the nation is to accomplish its renewable energy

development goals, agencies must determine methods for mitigating wind-radar impacts without

relying on next generation technologies.

Mr. Wright also noted that the recent change in Administration has created the need to repeat efforts

to raise the issue with and garner support from agency leadership. He argued that support from

leadership is critical to providing the direction, support, and authority needed for effective change in

agencies. Without direction from the top, penetration of the many agency layers is nearly impossible,

Mr. Wright said. Further, only leadership from the top can create a sense of ownership and guarantee

the budget needed to address these issues.

Mr. Wright noted that DHS has begun efforts to develop standardized criteria to help identify actual

impacts. He explained that these criteria will allow DHS to objectively quantify impacts, assisting in the

identification of needed mitigation methods. Furthermore, he said, the better the certainty about

impact assessments, the more willing DHS will be to release nearby land for wind energy development.

Mr. Wright announced that DHS would soon release a Request for Proposals (RFP) for the development

of an assessment tool.

Mr. Wright asserted that, while there have been a number of efforts made within individual agencies,

there remains a real need for coordination between agencies. Without this, he warned, agencies will

lack the necessary sense of shared ownership and joint benefit from the tools developed.

Ken Kingsmore, Department of Defense, serves as the DoD leadership within the Long-Range Radar JPO,

where he works with Mr. Russell Wright of the Department of Homeland Security. He also manages the

Joint National Airspace System Defense Planning Group (JNDPG) serving as the DoD leader since 1985.

Mr. Kingsmore was a fighter pilot in the U.S. Air Force, retiring after more than 28 years of service.

Mr. Kingsmore elaborated on some of the concerns about radar interference from wind facilities. He

explained that the Department of Defense faces some obstacles in testing interference mitigation

options as there are few “sterile” areas left. Due to the large scale of residential and industrial

development surrounding military bases (which are often a boon for local economic development), few

bases remain on which potential solutions can be tested.

He echoed the proceeding speakers’ comments encouraging cross-agency collaboration. He asserted

that the primary method for resolving conflicts about deferred, delayed, or rejected wind facility



proposals, which entails Congressional involvement on a case-by-case basis, is not sustainable. Mr.

Kingsmore concluded by expressing a strong desire for the wind industry and the radar industry to

collaborate with agencies toward a technical solution for radar interference from wind energy.

Ed Ciardi, National Oceanic Atmospheric Administration (NOAA), discussed concerns

about wind energy’s interference with weather radar and shared information about

some of the agency’s mitigation research initiatives.

Mr. Ciardi is a meteorologist at the Next Generation Weather Radar (NEXRAD) Operations Center in

Norman, Oklahoma, where he has worked for 16 years. The Center provides operational support,

depot-level hardware and software maintenance, configuration management, and logistics support to

the 166 NEXRAD radars within the U.S.’ national network.

Mr. Ciardi explained that while radars can filter out stationary objects, the movement of turbine blades

makes wind facilities highly visible to radar. Turbine blades are reflective and can appear on weather

radars as thunderstorms, resulting in the inaccurate but automatic calculation of derived products like

estimated precipitation. When forecasters must rely on these radars for weather forecasts, they can

inaccurately perceive a flash flood. Since much of the nation’s best wind resource occurs in the

Midwest, aka “tornado alley,” there is concern that a forecaster might be unable to accurately

understand weather conditions at a facility, even in the event of a severe weather event.

This is also a problem for the Department of Defense, as military pilots use these radars to identify safe

flight paths avoiding major storms. It is inefficient for these pilots to “fly around ghosts,” and unsafe to

risk missing a real weather event because of interference.

He explained that moving or adjusting radar angles to avoid interference from wind facilities would

cause coverage gaps and blind spots. However, Mr. Ciardi acknowledged that re-siting or re-orienting

wind turbines also represents a loss for developers and energy production. For that reason, NOAA is

looking at alternative mitigation options, such as operational curtailment – turning off the turbines

during weather events in which an accurate forecast is especially important. This option is somewhat

attractive to developers; because wind turbines shut down automatically at severely high wind speeds,

weather-related curtailment requirements would not likely result in significant loss for developers.

Additionally, NOAA is interested in working with developers to utilize the meteorological tower data

collected by developers at wind facilities. Information about temperature, wind speed, and

precipitation, when provided to local forecasting offices, could compensate for the contamination of

precipitation estimates discussed above.

Mr. Ciardi also shared that NOAA is collaborating with DHS to develop a radar and wind interaction

model. He noted that NOAA is working with the University of Oklahoma to develop an automatic wind-

turbine filtration system for weather radar. NOAA is also collaborating with the University on a study of

signal processing identification, but explained that this solution is many years in the future.

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In the future, Mr. Ciardi believes that the industry can contribute to decreased interference by

remaining a reasonable distance away from radar facilities and by incorporating tools like stealth

designs, curtailment options, and met-data sharing. For the agencies’ part, improved modeling tools,

better forecaster training, and alternative radar arrays hold promise as potential contributions to a

common solution. He feels that a MOU between industry and federal agencies (such as the UK MOU

discussed by Mr. Blackman) would also benefit all involved and enable better collaboration. Finally, he

said, developers need a “one stop shop” – an opportunity for early consultation with representatives

from all applicable agencies to screen out the most problematic sites and to highlight issues that need to

be mitigated before the project can be approved.

Note: The following section is still undergoing technical review and is not final.

Mr. Seifert provided an overview of the Department of Energy’s (DOE) activities relating to radar

interference DOE is at the center of the many overlapping circles of wind industry and other agencies.

DOE is responsible for supporting the national renewable energy development goals, but as a

government agency, it must avoid interference with the mission of other agencies.

Mr. Seifert noted that DOE has approached wind-radar issues by focusing primarily on research and

development of mitigation options. It has also worked aggressively over the past years to improve

education on the issues and potential mitigation strategies to developers and other agencies, as well as

internally. This has resulted in awareness by developers of the need to approach FAA early in the

planning process.

However, of the total megawatt capacity of wind energy proposed for development in 2008, a larger

portion was affected by radar issues than was installed. This trend poses a problem for meeting national

renewable energy goals; in order to reach those goals, development will have to double each year until

2025.

Comments, Questions & Answers

Comment (by AWEA): From the perspective of the wind industry, a suite of mitigation options will allow

for the most efficient use of wind resources. The industry wants to use caution in identifying which

options should be on the table – for instance, curtailment may affect income streams – but does want to

offer a number of options. The industry also appreciates the efforts by agencies to coordinate with

developers and to keep developers informed.

Response: In return, it would be useful to agencies if the industry shared results of its own technological

developments and mitigation tests.

Question: When developers notify the National Telecommunications and Information Administration of

proposed facilities, are those plans distributed to all agencies for review?



Answer: FAA has the best process for distributing that information; by notifying both NTIA and FAA, a

developer could ensure that all appropriate agencies are informed of plans.

Question: Are other European countries interested in following the UK MOU model or is it perceived to

pose a threat to national security?

Answer: The UK is seen as a leader in this realm. It experienced many of these problems well in advance

of the U.S.; we can learn from their history of exploring and attempting to address the issues.

Question: The idea of operational curtailment during major storms seems appealing to developers.

However, what do grid operators think? It is difficult to transition from high bursts of energy (which the

grid would experience immediately prior to curtailment) to low energy.

Answer: Grid operators are starting to require meteorological data within wind farms. They can use this

information while still protecting proprietary information. Incidentally, developing relationships with

grid operators is an additional need.

Candidate Solutions

Geoff Blackman, Westslope Consulting, reviewed some of the impacts from wind energy to primary and

secondary radar systems. He explained that current technological solutions are

limited, with radar unable to filter out wind facility “clutter” and turbines lacking the

ability to minimize the amount of energy reflected back to radar. He asserted that

both turbines and radar must be updated to minimize the impacts. Solutions should be considered for

turbines, wind facilities, radar systems, and automation or command and control systems.

Mr. Blackman explained that older radars have limited mitigation options and will need to be replaced,

but newer radar might suffice with additional upgrades. However, solutions for one type of radar may

not work for others. As the UK MOU states, “There is no universal solution to mitigating the effects of

wind turbines on radar.” Therefore, a toolbox of options is needed. Mr. Blackman explained that the

UK collaborative developed by MOU will research options relating to different types of radar, including

holographic and in-fill radar, as well as stealth options for turbines (e.g., Vestas and QinetiQ have

developed stealth blades). In addition, the collaborative will develop a web-based site screening tool

incorporating criteria from each relevant agency. Mr. Blackman argued that the U.S. would benefit from

similar efforts. Collaboration would enable the development of common understandings of impacts,

issues, existing mitigation options, and potential solutions.

Mr. Blackman discussed the current radar systems in the U.S. and reviewed the state of knowledge on

each:

Long-range radar – the backbone of primary surveillance in the U.S

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FPS-20 series and ARSR 1/2s – Comprised of 65 systems, these radars were deployed in the late

1950s and early 1960s and upgraded in the early 1980s. Mr. Blackman explained that this

upgrade improved the performance, but noted that it is a crude fix in relation to wind facilities.

He went on to say that a Long Range Radar Service Life Extension Program (LRR SLEP) was

currently underway, which will modify the architecture and significantly increase the capability

of these radars. The changes to the architecture will provide a foundation that is both flexible

and scalable to allow for future hardware and software improvements. Potential mitigation

options for these radars include adding a high beam to the antenna (thereby allowing radar to

see over the turbines), implementing concurrent beam processing, and passing additional target

report information to military command and control systems.

ARSR-3 – Deployed in the late 1970s and upgraded in the 1980s, there are 13 of these systems

in the U.S. These need to be somewhat desensitized in order to avoid the false signals projected

by wind facilities, but caution is needed to avoid over-desensitizing them and losing data. Mr.

Blackman anticipates that a prototype modification, the Advanced Runlength Process, will be

relatively inexpensive. Mr. Blackman explained that this modification would be an interim

solution and that the aforementioned LRR SLEP would present a short term solution

ARSR-4 – There are 43 ARSR-4 systems in the U.S., deployed in the 1990s. To mitigate impacts

to these systems, Mr. Blackman recommends possibly adding Doppler processing to upper

beams and enhancing map clutter processing, but notes that there is concern about making

alteration to the hardware as it would require redesign of its many dedicated components.

TARS – 7 TARS systems were deployed in the early 1980s. Mr. Blackman recommends

conducting field trials with SPE-3000.

Air Traffic Control

ASR-8 – There are 38 of these systems, which were deployed in the 1970s. Mr. Blackman

suggests upgrading them with a digitizer, such as a TDX-2000 or newer SPE-3000, or replacing

them with an ASR-11 or similar.

ASR-9 – 135 of these systems were deployed in the mid 1980s. For these, Mr. Blackman

recommends retro-fitting them with as part of a service life extension program or replacing

them with ASR-11s.

ASR-11 – The 110 ASR-11 systems began to deploy in the late 1990s. Mr. Blackman suggests

implementing concurrent beam processing for these radars and/or integrating gap-fillers (see

below).

Gap-Fill Radar

Many technologies of gap-fillers exist, including options produced by Cambridge, DeTect,

Harrier, OCAS, Raytheon, and more. These radars are sited to offer a different and unimpeded

view of an area of interest. In the case that a wind facility blocks important visibility for a radar,

a gap-filler could be installed on the opposite side of the wind facility to provide a

supplementary view of the area of interest. These radars are capable of observing a range of

detail, from bats, to hang-gliders, to tornadoes. When fused with existing radar systems, it is

important that observers be able to distinguish aircraft among the other data.



Next Generation – long term solutions

Automation systems are typically limited to one radar only to control traffic. Multi-radar

trackers to fuse data from various radar offers a simple solution to the effects of wind facilities

when coverage is overlapping.

Mr. Blackman notes that existing signals from radar could be utilized to detect aircraft over wind

facilities via bi-static/passive radar technologies.

Two other options currently being considered to replace long range and weather radar includes

MPAR and CASA. Requirements should be incorporated to mitigate wind facility “clutter”.

Weather

WSR-88D – Mr. Blackman referred attendees to Mr. Ciardi’s presentation in relation to this

technology, which was deployed in the late 1980s and comprises 159 systems. He highlighted

that current research on interpolation schemes (which measure movements) might aid in

distinguishing turbines from other data.

Mr. Blackman summarized by acknowledging that a number of candidate solutions to radar interference

have been presented. The current task is to cull the best options from the many candidates and

prioritize funding to the most-needed solutions. He reiterated the need for collaboration between

industry and government agencies. He also recommended coordinating with the UK and other

international working groups to avoid redundancy and to build on lessons learned.

Francis Lok, Raytheon Company, discussed improved radar system possibilities. Mr. Lok received his

B.Sc. and Ph.D. degrees in Electronic Engineering from the University of Sussex, U.K. He has

been with Raytheon Company since 1985. He worked on various Air Traffic Control radar

systems including ASR-10, ASR-11, the U.S. Army Mobile Air Traffic Control, and Precision

Approach Radar system. His recent assignment is Technical Director for the Long-Range Radar Service

Life Extension Program.

Mr. Lok explained that echoes from wind facilities can have similar characteristics to those of an aircraft

and can sometimes be significantly stronger in amplitude. This can result in high alarm rates and missed

aircraft detections. A number of mitigation strategies (listed on slide 3) have been implemented,

proposed, or flagged for additional research for both long-range radar and air traffic control radar.

Mr. Lok examined a case study near Travis Air Force Base in California. The Solano County Wind

Resource Area created a “black hole” for Travis’ air traffic controllers. He shared an illustration (slide 3)

on which the significant number of red dots represent “transponder response only” targets (i.e., targets

that show up on the primary radar but do not send identification verification signals to the secondary

radar). These false alarms were created by the wind facility.

As a potential mitigation method, Raytheon attempted to look over, rather than through, the wind

facility by increasing the angle at which the radar antenna was tilted. Raytheon also chose to extend the

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high beam over the wind farm, transitioning to low beam at a greater distance. Utilizing these methods,

Raytheon was able to increase the average probability of aircraft detection above the wind resource

area from 67.53% to 92.72%.

Raytheon is also using an X-Band gap filler technique to cover targets above the wind farm. Because the

gap filler utilizes a narrow pencil beam radar, the wind farm interference can be avoided entirely, as

opposed to the wider fan beam radars already installed (see slide 16). This, in effect, allows the radar

system to detect the area surrounding, including the area above, the wind facility.

Alternately, X-Band panels could be attached to towers at wind facilities (see slide 18). These panels

would then monitor the area immediately above the turbines. However, growing turbine heights pose a

complication, as the towers on which the panels are mounted must exceed the turbine heights.

In summary, Mr. Lok noted that each site is different and there is no silver bullet. However, he believes

that X-Band offers an important candidate for wide application for wind turbine interference mitigation.

Melissa McCarthy, OCAS, is the General Manager of OCAS Inc. Ms. McCarthy is a

graduate of the United States Military Academy with a degree in engineering

management. She served 6 years in the US military as a Communications Officer rising

to the rank of Captain. After leaving the military, Ms. McCarthy has focused on using her leadership

experience and skills to develop new technologies in the interest of national security, primarily in the

aviation field.

Ms. McCarthy gave a quick presentation on a potential mitigation technique – the audiovisual warning

system. The system incorporates detection radars, placed around the periphery of the wind facility, and

uses them to detect and track aircraft. It assesses the relative position of the aircraft; once the aircraft

crosses a certain threshold, the warning system begins to transmit a radio warning to the approaching

pilot. It also flashes warning lights to illuminate the facility and allow the pilot to avoid all turbines and

other facility infrastructure.

The OCAS system addresses some of the concerns about lighting discussed on Day 1 of the meeting. The

FAA has agreed to approve, on a case-by-case basis, the substitution of such warning systems as

satisfactory for meeting the FAA’s visibility requirements. Rather than utilizing bright lighting at all

hours (or at least at night), the facility could leave the lights off for the majority of the time; they would

only turn on automatically when an aircraft approaches.

The OCAS system could also be used to solve some of the radar interference problems experienced at

wind facilities. With its inherent radar capabilities, OCAS can detect low flying approaching aircraft that

are otherwise lost behind the shadow of the wind farm and relay this data to the other FAA or DOD

radar security systems.

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Research Needs Identified by Panel

As a conclusion to the panel, Mr. Seifert offered a list of research priorities needed for wind-radar

interference issues:

Organizational needs

o Funding for research

o Outreach/education at senior levels of agencies

o “Toolbox” of best practices in siting

Technologies to test:

o Sensor fusion

o Gap fillers

o NEXRAD screening tool

o Improved radar systems

o Advanced software

o Manufacturing (turbines) with stealth filters

Research on potential mitigation strategies:

o Operational curtailment for turbines

o Sharing of met tower data with NOAA



Session IV: Property Values

Ben Hoen, Lawrence Berkeley National Laboratory, shared the results of a

groundbreaking study on impacts to property values at nearby homes resulting from

the development of nearby wind facilities. Mr. Hoen works under contract to the

Laboratory to investigate community responses to different renewable energy sources. In addition to

completing the study presented here, he is currently working on a separate analysis of the impact of

solar energy systems on home selling prices as well as an investigation into public acceptance of

households living near wind turbines. Mr. Hoen has spoken numerous times on the issue of wind energy

and property values, is a graduate of Bard College with a Masters Degree in Environmental Policy, and

holds Bachelors degrees in Finance and Business from University of Maryland.

Mr. Hoen explained that his presentation would focus on the results of a study he has conducted over

the past few years in tandem with colleagues at LBNL, San Diego State University, and Bard College. He

noted that his presentation would not discuss mitigation strategies or next steps. Nor would it attempt

to explain effects, if any. Instead, the study focuses on whether any effects to property values exist.

Because property values have been linked to aesthetics and because aesthetic concerns exist in some

corners regarding wind turbines, LBNL sought to address concerns that the construction and operation

of wind facilities would decrease nearby properties. LBNL distinguished between three categories of

impacts:

Area stigma – Concerns that rural areas will appear more developed

Scenic vista – Concerns over decrease in quality of scenic vistas from homes

Nuisance stigma – Potential health and well-being concerns of nearby residents who might

wonder about sound, flicker, etc.

Basic research questions of the study include:

1. Is there evidence that views of turbines measurably affect sale prices?

2. Is there evidence that proximity to turbines measurably affect sale prices?

3. Do the results change over time and are there other observable impacts?

Plenty of “grey” literature exists on this topic and has generated quite a bit of interest. However, this

literature has not been published in peer-reviewed journals and questions exist about the intentions of

many of the authors. He explained that, after reviewing the literature, the researchers collected data on

sales transactions within multiple sample study areas. They then visited each home in the survey areas

to measure impacts. The researchers used multiple statistical models, relying primarily on the hedonic

pricing model, to measure effects. They tested for the presence of all three stigmas mentioned above.

The results have been peer reviewed and will culminate in an LBNL report and publication in at least one

journal.

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Mr. Hoen illustrated the study’s sample areas (slide 11), which occur in Washington, Oregon, Wisconsin,

Iowa, Texas, Oklahoma, Illinois, New York, and Pennsylvania. He noted that roughly 7500 home-selling

or -buying transactions occurred within these study areas. Most of these transactions occurred after the

construction of the wind facility; others occurred after the facility was announced but before it was

built.

The Hedonic pricing model assumes that homes have various characteristics that a buyer will take into

consideration (e.g. number of bedrooms, bathrooms, etc.) Using the information about a local

marketplace, sellers can assess the marginal value of performing construction or renovations prior to

selling the house. He also stressed that significance levels are important.

In discussing the results, Mr. Hoen began with the scenic vista stigma. He explained that this required

researchers to measure the value of the scenic vista prior to wind facility construction. Each home was

rated in terms of its scenic vista prior to construction, with rating ranging from poor to premium.

Following construction, the dominance of turbines within the view shed was ranked from minor to

extreme dominance (see slide 15). Using the Hedonic model, researchers found that buyers and sellers

both care about scenic vista. The results (statistically significant above the 1% level) showed

comparable homes with poor vistas sell for 21% less than those with an average vista. Similarly, homes

with a premium vista sell for 13% more than those with an average vista.

However, the researchers found (at a 10% statistical significance level) that turbines do not create a

scenic vista stigma. That is, they do not affect selling prices.

To study the area and nuisance stigmas, researchers used geographic information systems (GIS) to

estimate the distance of every home from the nearest turbine. Distances were divided into 5 intervals

(see slide 16). They found that the effects outside of 1 mile are relatively small and statistically

indistinguishable from zero. However, effects within one mile were slightly larger and negative. Mr.

Hoen stressed that no differences in selling prices are statistically significant at the 10% level.

Interest piqued by the nearby impacts, the researchers conducted further investigations and found that

homes within one mile of construction already had a depressed value prior to the announcement of the

wind facility’s construction. (Mr. Hoen hypothesized that this depressed value might coincide with a

rural location that is better suited for wind facilities.) For these homes, values decreased slightly

following the announcement of the construction but increased significantly following construction.

Mr. Hoen briefly reviewed other models contained in the report (see slide 29), including the repeat sales

model, the sales volume model, the orientation model, and the overlap model. The researchers found

that results are consistent across all models.

In summary, the study concludes that: “Although the analysis cannot dismiss the possibility that

individual homes have been or could be negatively impacted, the Berkeley Lab research finds that if



these impacts do exist in the sample of homes analyzed, they are either too small and/or too infrequent

to result in any widespread, statistically observable effect.”

Note: in the final presentation posted to the LBNL and NWCC websites, LBNL offers some

recommendations on additional research needs.

Questions on Property Values

Question: Is there any possibility that the presence of a developer who is shopping around for land could

confound the data?

Answer: There were some qualifications to the types of sales included in the data; sales to corporations

and family members were among the transactions excluded.

Question: Did you test for tax brackets, school quality, and other issues?

Answer: LBNL tested for schools; results were robust. Although they did not test for taxes specifically,

the team examined other microspatial factors, which might include taxes, and found that they did not

affect results.

Question: Do you think there might be effects from high voltage transmission lines? Also, do other

facilities have infrastructure extended more than 1 mile beyond the primary project?

Answer: For some other types of facilities (e.g. Superfund sites), effects can extend for miles. Concerns

about potential health impacts can cause some large effects. Concerns about visual impacts result in

much smaller effects.



Session V: Icing Considerations

Jeff Freedman, Senior Research Scientist at AWS Truewind, LLC, provided an overview

of studies regarding icing considerations. Dr. Freedman possesses both academic and

professional degrees in meteorology and oceanography, atmospheric science and law.

Prior to earning his Ph.D. at the University at Albany, State University of NY, Dr. Freedman was Assistant

Counsel to the New York City Department of Environmental Protection. Dr. Freedman is a Certified

Consulting Meteorologist and was principal for the meteorological consulting firm Atmospheric

Information Services before joining AWS in February 2007.

Mr. Freedman began by differentiating between types of icing. He explained that rime icing occurs

when clouds of supercooled water droplets come into contact with sub-freezing surfaces. Glaze icing

occurs when liquid water (rain or drizzle) freezes on sub-freezing surfaces.

He discussed a high resolution modeled climatology recently developed by AWS to identify icing

frequencies in the U.S. and Southern Canada. Validation of the model used available estimates from

long-term tall towers, high altitude surface observation stations, and previous in-situ mountain studies

at various heights above ground level. For the study, icing frequency was defined as the number of

hours a particular point would be immersed in sub-freezing cloud divided by the total number of hours

in the simulation. Maps illustrating the results at various heights above ground level can be seen on

slides 9-13.

Observed icing areas correlate with the modeled icing areas; however, the persistent freezing of

equipment may skew the degree of icing impact by a factor of 10 or more.

Dr. Freedman also offered some background on general siting considerations associated with icing. He

noted that areas prone to icing require different equipment. Heated sensors allow for the collection of

wind data event during icy weather events. However, although the sensors themselves may work in

extreme conditions, the build up of rime ice on supporting infrastructure may result in blockage of the

airflow in and around the anemometer.

Other icing considerations involve production losses, especially degraded power performance associated

with blade ice. Facilities may also need to shut down to ensure safety and prevent ice throw. In the

event that severe weather prevents maintenance access, a facility might also need to shut down.

Finally, downed power lines can also cause a shutdown. In certain areas, Dr. Freedman said, losses due

to icing can exceed 8%.

Dr. Freedman outlined some areas where additional research is needed regarding icing. First, better

instrumentation and monitoring abilities are needed to enable consistent measurement during actual

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icing events. Additional measurements should also include solar radiation, precipitation, and

precipitation type. Dr. Freedman also noted that he will participate on a project in Vermont to assess

actual impacts to turbines as icing occurs.


Appendix A: Meeting Agenda October 20-21, 2009

Appendix A: Seminar Agenda

Purpose:

Review and discuss existing research, methods, and tools available to address technical issues

associated with siting wind energy facilities. Because the NWCC convenes a separate, biennial

meeting on wildlife concerns associated with wind siting, this meeting will not address that topic.

Examine the state of knowledge on pressing issues for siting wind facilities, and identify research

needs or other next steps that might lead to solutions for those issues.

Develop meeting proceedings which may be used as an unbiased source of technical information for

those engaged in siting and permitting wind facilities.



DAY 1: OCTOBER 20, 2009

12:00 pm Registration and lunch

Location: National Hall,

Washington Plaza Hotel

1:00 pm Welcome, Introductions & Meeting Purpose Abby Arnold, NWCC Facilitator

1:15 pm I. Visual Considerations

The first portion of the Visual Considerations session will examine

issues, regulations, and mitigation methods for visual impacts

from wind facilities.

Eastern U.S. - Assessment methods, public perception and

regulatory environment in the eastern US.

Western U.S.:

o BLM Visual Resource Management methodology

o Research to assist the wind industry in measuring

visual risks early

o Other research initiatives

Matt Allen, Saratoga Associates

John McCarty, U.S. Bureau of

Land Management

2:05 pm Addressing aesthetic concerns and FAA requirements for

lighting and marking

o Agency coordination


Land Management

Jim Patterson, FAA

2:55 pm Q&A

3:10 pm Break

3:30 pm II. Acoustic Considerations

Wind Turbine Sound

o Fundamentals of perception

o Noise generating mechanisms

o Research and planning considerations

Mark Bastasch, CH2M Hill

3:50 pm Sound propagation

o Development of new methods & metrics

o Wind screen techniques

Bo Søndergaard, DELTA

4:10 pm Calibration studies and sound modeling

Ken Kaliski, RSG, Inc.

4:30 pm Q&A

4:50 pm Break



5:00 pm

Panel Discussion – Acoustic and Visual Considerations

o What is the state of knowledge? What conclusions

can be made? What are the implications?

o What outstanding questions need to be answered?

What are the priority research needs?

Moderator: Abby Arnold, NWCC

Facilitator

Mark Bastasch, CH2M Hill

Ken Kaliski, RSG, Inc.

Mike Pasqualetti, Arizona State

University

Bo Søndergaard, DELTA

Matt Allen, Saratoga Associates


Land Management

6:00 pm Q&A

6:15 pm Adjourn to reception Diplomat Room,


DAY 2: WEDNESDAY, OCTOBER 21, 2009

8:30 am Breakfast

National Hall,


9:00 am Welcome and review daily agenda

9:15 am III. Radar Interference

Introduction to the issues

Geoff Blackman, Westslope

Consulting

9:30 am Panel: Federal agency perspectives and research

During this panel, representatives from federal agencies will share

research results and the primary relevant concerns of each agency

o U.S. Department of Homeland Security

o U.S. Department of Defense

o Federal Aviation Administration

o National Oceanic and Atmospheric Administration

o U.S. Department of Energy

Moderator: Gary Seifert, INL

Russell Wright, DHS

Ken Kingsmore, DOD

Kevin Haggerty, FAA

Ed Ciardi, NOAA

10:50 am Q&A

12:10 pm Lunch

Diplomat Room,




1:10 pm Potential Solutions

During this time, speakers will identify some of the potential

solutions and mitigation technologies

o Improved radar systems

o Stealth technology

o “Gap fillers”

o Siting

Geoff Blackman, Westslope

Consulting

Dr. Francis Lok, Raytheon

Melissa McCarthy, OCAS

2:15 pm Q&A

2:25 pm Break

2:45 pm IV. Property Values

Methodology, findings, and implications from recent study

Ben Hoen, Lawrence Berkeley

National Laboratory

3:15 pm Q&A

3:25 pm V. Icing considerations

Frequency of icing and icing events

Siting considerations

o Equipment requirements

o Efficiency impacts

o Safety considerations

Additional research needs

Jeff Freedman, AWS Truewind

4:00 pm Q&A

4:15 pm Adjourn


Appendix B: Meeting Participants October 20-21, 2009

Appendix B: Seminar Participants

Final List of Participants

John Albers

Director, Industrial/Energy Programs

Woolpert

Matthew Allen

Principal

Saratoga Associates

Daniel Ancona

Program Manager

Princeton Energy Resources International

Suzi Asmus

Project Manager

Horizon Wind Energy

Jennifer Banks

Offshore Wind and Siting Specialist

AWEA

Brice Barton

Development Manager

TradeWind Energy

Jeffrey Basch

General Manager

Accio Energy, Inc.

Mark Bastasch

Lead Acoustical Engineer

CH2M Hill

Matthew Behrum

Associate Scientist

Integral Consulting

Geoff Blackman

Principal

Westslope Consulting, LLC

Josh Bohach

Project Manager

Horizon Wind Energy

Travis Bullard

Real Estate Coordinator

Eolian Renewable Energy

Kraig Butrum

President

American Wind Wildlife Institute

Alex Cantu

Meteorologist

enXco

Edward Ciardi

Meteorologist

NEXRAD Radar Operations Center

Rachel Clement

Assistant Project Engineer

enXco

Werner Cook

Research Associate

University of Oklahoma, Oklahoma Wind Power

Initiative



Thomas Cotton

Vice President

Complex Systems

Shannon D’Agostino

Sr. Environmental Project Manager

HDR Engineering, Inc.

Huy Dao

Computer Specialist

Federal Aviation Administration

Tricia DeBleeckere

Energy Facilities Planner

Minnesota Public Utilities Commission

Ed DeMeo

President

Renewable Energy Consulting Services, Inc.

Michael Derby

Wind and Hydropower Technologies Program

Office of Energy Efficiency and Renewable

Energy

U.S. Department of Energy

Michele DesAutels

Communication Specialist

Department of Energy

Robert DeSista

Regulatory Branch Chief

US Army Corps of Engineers

Lynn DiTullio

Wind Energy Center Program Manager

University of Massachusetts Wind Energy

Center

Nick Doss

Meteorologist

Public Utilities Commission of Ohio

Paul Dwyer

Student

U.S. Military Academy

Dept. of Systems Engineering

James Field

Supervisor, NUC/Engineering Plant Support

Sacramento Municipal Utility District

Patricia Fleischauer

Vice President

TRC

Larry Flowers

National Technical Director

National Renewable Energy Labratory

Valerie Franklin

Project Manager

Horizon Wind Energy

Jeff Freedman

Senior Research Scientist

AWS Truewind, LLC

Chris Galazzi

Consultant

Zenergy, Inc.

Emile Ganthier

Software Engineer

Harris Corp

Tim Gehring

Project Manager

RMT, Inc.

Jason Gifford

Consultant

Sustainable Energy Advantage, LLC



Patrick Gilman

Presidential Management Fellow

Wind and Hydropower Technology Program

Energy Efficiency and Renewable Energy

US Department of Energy

Krista Gordon

Business Developer

Iberdrola Renewables, Inc.

Anne-Marie Griger

Environmental Planner

Tetra Tech EC Inc

Kevin Haggerty

Manager


Spencer Hamilton

Owner

Shore Green Energy LLC

Ben Hoen

Subcontractor

Lawrence Berkeley National Laboratory

Laurie Jodziewicz

Manager of Siting Policy

AWEA

Tre Jerdon

Research Associate

American Planning Association

Kenneth Kaliski

Director

Resource Systems Group Inc

Aileen Kenney

National Director - Wind Energy

Tetra Tech EC, Inc.

Kenneth H. Kingsmore

Program Manager

DoD Long Range Radar Joint Program Office

Francis Lok

Engineering Fellow

Raytheon Company

Todd Mattson

Senior Environmental Project Manager

HDR Inc.

Melissa McCarthy

General Manager

OCAS

John McCarty

Chief Landscape Architect

Bureau of Land Management

Michael Musich

Permitting Administrator

Iberdrola Renewables, Inc.

Martin J. (Mike) Pasqualetti

Professor

Arizona State University

School of Geographical Sciences and Urban

Planning

Jim Patterson

Airport Safety Specialist


Rorik Peterson

Project Developer

Horizon Wind Energy

Scott Phillips

Director - Energy Program Development

Tetra Tech EC



Eva Piltch-Boucher

Systems Engineer

SRC

Maria Pirone

Senior Bus Dev Manager

Harris Corporation

Jim Ploger

Regional Coordinator

National Association of State Energy Officials

Lester Polisky

Senior Principal Engineer

Comsearch

Bonnie Ram

Asst. Vice President

Energetics Incorporated

Russell Raymond

Renewable Energy Policy Analyst

Energetics Incorporated

Rio Roland

Resource Assessment Engineer

enXco

Glenn Schleede

[email protected]

Gary Seifert

Senior Project Manager

Idaho National Lab

Bo Sondergaard

Senior Consultant

DELTA

Hong Spores

Hydrogeologist/Project Manager

HDR Engineering

Jennifer States

Energy Specialist

Pacific Northwest National Laboratory

Howard Swancy

GAITS, Inc.

Gunnar Tamm

Instructor


Dept. Civil and Mechanical Engineering

Patricia Temple

Complex Systems

Colonel Timothy Trainor

Professor and Department Head



Kurt Tramposch

Environmental Planner

SuAsCo Watershed Council

Gilbert Velasquez

CTO/Owner

Breeze Energy, LLC

Matthew Wagner

Manager-Wind Site Development

DTE Energy

Wendy Wallace

Energy Analyst

Energetics Incorporate/ Department of Energy

Robert Williams

Environmental Consultant

Dominion Resources Services



Joe Wood

GIS Manager

Ridgeline Energy LLC

Russell Wright

Program Manager

Long Range Radar Joint Program Office

Katharine Wurzbach

Student



NWCC Staff:

Abby Arnold

Vice President and Senior Mediator

Kearns & West

(202) 535-7800

[email protected]

James Damon

NWCC Outreach Coordinator

RESOLVE

(202) 965-6383

[email protected]

Taylor Kennedy

NWCC Associate

RESOLVE

(202) 965-6392

[email protected]


Appendix C: Meeting Sponsors October 20-21, 2009

Appendix C: Meeting Sponsors

The planning and execution of the State of the Art in Wind Siting Seminar and the production of this

document was supported, in whole or in part, by the United States Department of Energy under

Contract No. DE-AT01-07EE11218. Financial support by the Department of Energy does not constitute

an endorsement by the Department of Energy on the views expressed in this document, nor do the

views and opinions of authors expressed herein necessarily state or reflect those of the United States

government or any agency thereof.

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