Wind Turbine Assessment

8/9/2019 Wind Turbine Assessment

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DNV Global Energy Concepts Inc.1809 7

thAvenue, Suite 900

Seattle, Washington 98101 USAPhone: (206) 387-4200Fax: (206) 387-4201www.globalenergyconcepts.comwww.dnv.com

Preliminary Survey of Potential Wind

Project Sites in the Town of Duxbury,

Massachusetts

FSRP0074-A

October 27, 2009

Prepared for:

Massachusetts Technology Collaborative

75 North DriveWestborough, MA 01581


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Preliminary Survey of Potential Wind Project Sites in the Town of Duxbury, Massachusetts FSRP0074-A

DNV Global Energy Concepts Inc. i October 27, 2009

Approvals

October 27, 2009

Prepared by Chad Nancarrow Date

October 27, 2009

Review by Michael Drunsic Date

Version BlockVersion Release Date Summary of Changes

A October 27, 2009 Original


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DNV Global Energy Concepts Inc. ii October 27, 2009

Table of Contents

INTRODUCTION......................................................................................................................... 1

AREA DESCRIPTION ................................................................................................................ 2WIND RESOURCE POTENTIAL AND CLIMATE................................................................ 9

SITING CONSIDERATIONS................................................................................................... 14

POTENTIAL OFFSET OF ELECTRICAL LOADS AND ELECTRICAL GRID ACCESS............................ 14

TRANSPORTATION AND SITE ACCESS......................................................................................... 16AVIATION CONFLICTS................................................................................................................ 16

Aviation Systems Report ...................................................................................................... 17VOR ...................................................................................................................................... 17

Radar ..................................................................................................................................... 18

ENVIRONMENTAL ISSUES AND PERMITTING............................................................................... 20

TELECOMMUNICATIONS CONFLICTS .......................................................................................... 25COMMUNITY IMPACTS ............................................................................................................... 26

FOUNDATION CONSIDERATIONS ................................................................................................ 26

SETBACKREQUIREMENTS AND PROJECT SCALE ........................................................................ 27Site 1 - Duxbury High School, Duxbury Middle School, and Alden Elementary School.... 29

Site 2 - Chandler Elementary School.................................................................................... 29

Site 3 - Duxbury Transfer Station, North Hill Golf Course, and Duxbury Town Hall/DPWFacility .................................................................................................................................. 30

ESTIMATED CAPACITY FACTORS ............................................................................................... 31

CONCLUSIONS ......................................................................................................................... 35

SITE 1-DUXBURY HIGH SCHOOL,DUXBURY MIDDLE SCHOOL, AND ALDEN ELEMENTARYSCHOOL ..................................................................................................................................... 35SITE 2CHANDLERELEMENTARY ............................................................................................ 35

SITE 3-DUXBURY TRANSFERSTATION,NORTH HILL GOLF COURSE, AND DUXBURY TOWN

HALL/DPWFACILITY................................................................................................................ 36MET TOWERRECOMMENDATIONS............................................................................................. 37

ADDITIONAL RECOMMENDATIONS............................................................................................. 38


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DNV Global Energy Concepts Inc. iii October 27, 2009

List of Figures

Figure 1. Location of Duxbury, Massachusetts .............................................................................. 4

Figure 2. Topographic Map of the Duxbury Area Showing Potential Development Sites ............ 5

Figure 3. Aerial Image of Site 1 (Duxbury High School, Duxbury Middle School, and AldenElementary School)................................................................................................................. 6

Figure 4. Aerial Image of Site 2 (Chandler Elementary School).................................................... 7

Figure 5. Aerial Image of Site 3 (Duxbury Transfer Station, North Hill Golf Course, andDuxbury Town Hall/DPW Facility)........................................................................................ 8

Figure 6. 70-m New England Wind Map and Proposed Project Locations.................................... 9Figure 7. 70-m New England Wind Map and Weather Stations .................................................. 11

Figure 8. Wind Rose for Duxbury Area........................................................................................ 13

Figure 9. Location of Transmission Lines .................................................................................... 16Figure 10. Results of FAA Long-Range Radar Screening Tool................................................... 18

Figure 11. Results of FAA NEXRAD Screening Tool................................................................. 19

Figure 12. Areas of Environmental and Cultural Significance in the Vicinity ofDuxbury High School, Duxbury Middle School, and Alden Elementary School ................ 20

Figure 13. Areas of Environmental and Cultural Significance in the Vicinity of

Chandler Elementary ............................................................................................................ 21

Figure 14. Areas of Environmental and Cultural Significance in the Vicinity of Duxbury TransferStation, North Hill Golf Course, and Duxbury Town Hall/DPW Facility............................ 21

Figure 15. Important Bird Areas................................................................................................... 24

Figure 16. Location of Microwave Towers in the Area of the Potential Wind Turbine Sites...... 25Figure 17. Site 2 - Potential Turbine Location ............................................................................. 29

Figure 18. Site 3 Potential Turbine Locations ........................................................................... 31

Figure 19. Example of Vegetation at Location 1.......................................................................... 37

Figure 20. View of Location 2 from the Northeast....................................................................... 38

List of Tables

Table 1. Wind Speed Estimates Based on New England Wind Map ........................................... 10

Table 2. Summary of Available Wind Data.................................................................................. 12Table 3. Annual Energy Consumption at the Duxbury Project Sites ........................................... 15

Table 4. Distance of Project Sites to Nearest Microwave Tower................................................. 25

Table 5. Subsurface Conditions of the Proposed Sites ................................................................. 27Table 6. Potential Turbine Models................................................................................................ 28

Table 7. Potential Site 3 Turbine Location Coordinates and Elevation........................................ 30

Table 8. New England Wind Map Weibull Shape Factor and Wind Shear Exponent ................. 32Table 9. Estimated Energy Losses Single Turbine .................................................................... 33

Table 10. Estimated Net Energy Production at Site 2 Chandler Elementary ............................ 33

Table 11. Estimated Net Energy Production at Site 3 Duxbury Transfer Station, North Hill

Golf Course, and Duxbury Town Hall/DPW Facility .......................................................... 34


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DNV Global Energy Concepts Inc. 1 October 27, 2009

Introduction

In May 2009 the Town of Duxbury (the Town) submitted a Municipal Wind Turbine Site Survey

Application to the Massachusetts Technology Collaborative (MTC) to request assistance inevaluating municipally owned property for community-scale wind development potential. MTCretained DNV Global Energy Concepts Inc. (DNV-GEC) to conduct a preliminary feasibility

study on behalf of the Town. On October 8, 2009, DNV-GEC visited properties in Duxbury and

met with members of the Town Energy Committee and members of the Town Administration.This report summarizes DNV-GECs review, identifies potential barriers to development, and

estimates wind resource potential. During this review, DNV-GEC utilized maps, aerial photos,available wind data, information gathered during the site visit, and DNV-GECs in-house

experience and expertise to determine whether sufficient wind development potential exists at

any of the proposed project sites. This high-level report is not intended as a detailed feasibility

study suitable for project financing.


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Area Description

The Town of Duxbury is located in eastern Massachusetts, approximately 30 miles southeast of

Boston off of Highway 3, as shown in Figure 1. According to the Municipal Wind Turbine SiteSurvey Application submitted to MTC, the Town identified the following six sites to consider forpotential municipal wind projects:

Duxbury High School

Duxbury Middle School and Alden Elementary School

Chandler Elementary School

Duxbury Transfer Station

North Hill Golf Course

Duxbury Town Hall and Department of Public Works (DPW) Facility

A topographic map of these potential wind turbine sites is shown in Figure 2. As seen on this

figure, the Duxbury High School site and the Duxbury Middle School and Alden Elementary

School site are situated adjacent to each other. Due to their close proximity, the wind resourceand other wind turbine siting considerations at these two sites are expected to be similar. As

such, these sites were grouped together as a single site for further evaluation in this report.Similarly, the Duxbury Transfer Station site, North Hill Golf Course site, and the Duxbury Town

Hall and DPW site are also situated adjacent to each other. These three sites were also grouped

into a single site for further evaluation. Using these groupings, the following three sites wereconsidered:

Site 1: Duxbury High School, Duxbury Middle School, and Alden Elementary School.The combined Duxbury-owned parcel acreage of these properties is approximately 116 acres

(37 acres for the high school and 79 acres for the middle/elementary school parcels). The siteprimarily consists of school buildings, parking lots, and sports/recreation fields. Wooded

areas and wetlands are situated near the northern end of the high school parcel. Wooded

areas, a pond, and wetlands (draining to the Bluefish River) are also located near the southernportion of the middle/elementary school property. The surrounding properties to the west are

primarily residential; the Bluefish River and residences are situated to the east; wetlands are

to the north; and a golf course is adjacent to the south. Elevations within the site range from

approximately 1 m to 15 m above sea level. An aerial image of the site is shown in Figure 3.

Site 2: Chandler Elementary School. This site consists of a parcel totaling approximately62 acres. The western portion of the parcel contains school buildings, parking lots, and

sports/recreation fields. The eastern portion of this parcel is heavily wooded. The adjacent

parcel to the north-northeast is also owned by Duxbury; however, this parcel is designated asconservation lands (consisting of wooded areas and wetlands) and is excluded from

development. Properties to the northwest, west, east, and south are primarily residential. The

elevation of this property ranges from approximately 26 m to 36 m above sea level. An aerialimage of the area is shown in Figure 4.


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Site 3: Duxbury Transfer Station, North Hill Golf Course, and Duxbury Town

Hall/DPW Facility. This site consists of several adjacent parcels owned by the Town ofDuxbury totaling approximately 386 acres. The parcels which include the golf course and

town hall/DPW facility are mainly contiguous, with the exception of two parcels located

within the interior which are designated as conservation lands (also owned by Duxbury) and

are excluded from development. The transfer station facility is situated across MayflowerStreet from these contiguous parcels, and includes a recycling area, composting area, and a

capped landfill. Aside from the golf course, the site is mostly forested with 15- to 20-m trees,

predominantly conifers. Additionally, there is a hay field in the northeast section of the site,east of the golf course.

During the site visit, only Site 3 was evaluated for the possible placement of a wind turbine. Asdiscussed below, Site 1 was eliminated from consideration due to insufficient area for a wind

project of the scale considered in this analysis; and Site 2 was eliminated due to height

restrictions, proximity to an elementary school, and the relative attractiveness of Site 3 comparedto Site 2.


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Figure 1. Location of Duxbury, Massachusetts


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29 October 2008Projection: Massachusetts Mainland State Plane, Meters, NAD83

Digital Elevation Model: United States National Elevation Data database, 30 m resolution

Property Boundary

Duxbury

High School

Duxbury Middle School

& Alden Elementary

Chandler

Elementary

North Hill

Golf Course

Town Hall &DPW Facility

TransferStation

Figure 2. Topographic Map of the Duxbury Area Showing Potential Development Sites


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Projection: Massachusetts Mainland State Plane, Meters, NAD83Aerial Imagery: Office of Geographic and Environmental Information (MassGIS)Property Boundary: Environmental Partners Group Inc.

Site Boundaries

Parcel Boundaries

Duxbury

High School

Duxbury Middle School

&

Alden Elementary

Figure 3. Aerial Image of Site 1 (Duxbury High School, Duxbury Middle School, and AldenElementary School)


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Chandler

Elementary


Site Boundary

Parcel Boundaries

Conservation Lands

Figure 4. Aerial Image of Site 2 (Chandler Elementary School)


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North HillGolf Course


Site Boundaries

Parcel Boundaries

Town Hall &

DPW Facility

Transfer

Station

Conservation Lands

Conservation Lands

Figure 5. Aerial Image of Site 3 (Duxbury Transfer Station, North Hill Golf Course, andDuxbury Town Hall/DPW Facility)


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Wind Resource Potential and Climate

Wind resource information is available from the New England Wind Map and a number of

weather stations and meteorological (met) towers in the area. This information has been used toestimate the range of possible wind speeds in the area; however, the actual wind resource at aparticular location is highly site-specific. In general, to reduce uncertainty in subsequent energy

estimates, DNV-GEC commonly suggests collection of on-site wind resource measurements

prior to installation of wind turbines at a particular location.

The portion of the New England Wind Map that encompasses the sites under evaluation is shownin Figure 6.

70-m Wind Resource

The New England Wind Map was developed by AWS TrueWind and was sponsored bythe Connecticut Clean Energy Fund, Northeast Utilities Systems, and the

Massachusetts Technology Collaborative.

The wind resource estimates were created using TrueWinds MesoMap, a mesoscaleatmospheric simulation system, at a spatial grid resolution of 200 meters. Estimates

should be confirmed by direct measurement according to wind industry s tandards.

DuxburyHigh School

Duxbury Middle School &Alden Elementary

Chandler

Elementary

North Hill

Golf Course

Town Hall &DPW Facility

Transfer

Station

Projection: UTM, Meters, WGS84Data Layers: AWS TrueWind, USGS Terraserver

Site Boundaries

Figure 6. 70-m New England Wind Map and Proposed Project Locations

The estimated wind resource range at each site, based on the New England Wind Map, includingAWS Truewinds estimated error of 0.6 m/s, is provided in Table 1.


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Table 1. Wind Speed Estimates Based on New England Wind Map

Coordinates1

(MA State Plane Meters, NAD83)

Site Easting Northing

Estimated AnnualWind Speed Range

at 70 m aboveground level (m/s) Class

2Rating

1. High School,Middle School, andAlden Elementary

267885 866722 5.7 to 7.3 2 Marginal

2. ChandlerElementary

263381 865298 5.7 to 7.1 2 Marginal

3. Transfer Station,Golf Course, TownHall/DPW

266381 865742 5.7 to 7.2 2 Marginal

[1] Coordinates at approximately the center of the site

[2] Based on the U.S. Department of Energy National Renewable Energy Laboratorys Wind Power ClassificationSystem for wind power densities at 50 m

The locations of weather stations and meteorological towers in close proximity to the proposedproject sites are shown in Figure 7. Data from the Marshfield, Plymouth, Taunton, and Miltonairport weather stations are maintained by the National Climatic Data Center. Data loggers at

these stations record hourly wind speed and direction data at a height of 10 m (33 ft) above

ground level. Since airports are typically placed in relatively sheltered locations in an area, winddata from these stations are likely to represent the lower end of the potential wind resource range

in the area. Data from Plymouth and Kingston were obtained from met towers installed and

maintained by the University of Massachusetts at Amherst Renewable Energy Research Lab(RERL). Data loggers at these towers recorded 10-minute wind speed and direction data at

various heights above ground level. Met towers are installed for the purpose of determining the

feasibility of a wind energy project; therefore, the towers are typically placed in well-exposed

locations and are likely to represent the high end of the potential wind resource range in the area.Although the data from the RERL met tower sites have not been adjusted to account for long-

term variations in the wind resource, data from the airport weather stations indicate that the

standard deviation of the annual average wind speeds in the Duxbury area is typically about 4%.Therefore, the long-term average wind speed at these locations may be up to 4% higher or lower

than the average wind speed from the measurement period. Wind data for each area weather

station are summarized in Table 2.


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Projection: UTM, meters, WGS84Data Layers: AWS TrueWind, USGS Terraserver

The New England Wind Map wasdeveloped by AWS TrueWind and wassponsored by the Connecticut Clean

Energy Fund, Northeast UtilitiesSystems, and the Massachusetts

Technology Collaborative.

The wind resource estimates werecreated using TrueWinds MesoMap,a mesoscale atmospheric simulationsystem, at a spatial grid resolution of

200 meters. Estimates should beconfirmed by direct measurement

according to wind industry standards.

ASOS & RERL Stations

Site Boundaries

70-m Wind Resource70-m Wind Resource

Figure 7. 70-m New England Wind Map and Weather Stations


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Table 2. Summary of Available Wind Data

Coordinates

(MA State Plane Meters,NAD83)

Location Easting Northing

Elevation(m)

MeasurementHeight (m)

AverageWind Speed

(m/s)Wind

Class3

Plymouth1 270434 854345 41 50 5.6 2

Kingston1

265023 858966 N/A 49 5.8 2

Marshfield(GHG)

2

268492 872287 3 10 2.9 2

Plymouth(PYM)

2

263966 851362 45 10 3.4 2

Taunton(TAN)

2

239761 847408 13 10 2.7 1

Milton(MQE)

2

231790 884688 194 10 5.7 3

[1] Source: University of Massachusetts Amherst Renewable Energy Research Laboratory, based on a 1-year periodof measurement. DNV-GEC has not independently verified the values.

[2] Source: National Climatic Data Center, based on a period of measurement of 7 to 11 years, except for theMarshfield station (based on 2 years of data only)

[3] Based on the U.S. Department of Energy National Renewable Energy Laboratorys Wind Power ClassificationSystem for wind power densities at 50 m

Based on the available wind data, DNV-GEC believes that the New England Wind Map provides

a reasonable range of average wind speeds at each of the sites under evaluation (see Table 1).

The wind rose for Duxbury according to the New England Wind Map is shown in Figure 8. Thewind rose indicates that the prevailing winds are from the south-southwest. The wind rose at the

Plymouth RERL station also indicates a south-southwest prevailing wind direction, and the windrose at the Kingston RERL station indicates prevailing winds from the southwest. Thus, there isacceptable agreement between the wind map and local observations confirming a general south-

southwest prevailing wind direction.


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0%

5%

10%

15%

20%

N

NNE

NE

ENE

E

ESE

SE

SSE

S

SSW

SW

WSW

W

WNW

NW

NNW

Time Pow er

Figure 8. Wind Rose for Duxbury Area

(Source: New England Wind Map)


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Siting Considerations

Potential Offset of Electrical Loads and Electrical Grid Access

Typically, the most cost-effective development scenario for municipally owned wind projects is

net metering. Based on new net metering provisions outlined in the Green Communities Act,

signed into law on July 2, 2008, and detailed in final regulations issued by the MassachusettsDepartment of Public Utilities (DPU) on June 26, 2009, net excess electricity generated during a

given month by a municipally, governmentally, or privately owned wind power project rated at

2 MW or less can be credited to the customers next monthly utility bill at the retail rate, inclusiveof the applicable default service kWh charge, transmission kWh charge, and transition kWh

charge. Municipally and governmentally owned or operated wind projects receive two additionalprovisions: a credit for the distribution kWh component of the retail rate and the ability to net

meter on a per unit basis, rather than per facility.

Net metering allows credits to be carried forward from month to month. Net metering in

Massachusetts also allows the energy output from a qualifying wind power project to be credited

towards several different loads with multiple utility meters, as long as the meters are under the

same distribution company and located in the same ISO-NE load zone. Additionally, the netmetering facility must be installed on the host customers side of the meter.

On August 20, 2009, DPU issued an order approving a model net metering tariff to guide thedistribution companies implementation of the net metering regulations. Conforming net

metering tariffs have been filed by the distribution companies and are expected to go into effect

on December 1, 2009, pending review and approval by DPU. Certain aspects of the net meteringtariffs are still undefined. Of particular importance is the rate at which net metering facilities are

credited for net excess generation as the applicable rate can have a dramatic impact on the

financial viability of a project. It is likely that this issue will be resolved within the next fewmonths but, until then, this remains an area of uncertainty for net metering projects. The

applicable tariff should be reviewed upon approval.

As an alternative to net metering, wind-generated electricity could be sold directly to thewholesale market through a power purchase agreement. However, the wholesale market rate is

likely to be significantly less than the retail rate and will lead to a longer payback period than if

the wind-generated electricity were to be used on site to displace retail electric rates. The sale ofrenewable energy credits (REC), available for either a net metering or wholesale market

purchase scenario, may help to improve project economics; however, the long-term market for

RECs is highly uncertain. Therefore, net metering is likely to be the preferred approach forcommunity-scale projects less than 2 MW.

Each of the sites under consideration in this report has on-site load that could provide a host

meter for a net metering facility. According to the Municipal Site Survey Application, DuxburyMiddle School/Alden Elementary consumes the greatest amount of energy, while the Duxbury

Transfer Station consumes the least (see Table 3). Consumption data were not submitted for the

North Hill Golf Course.


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Table 3. Annual Energy Consumption at the Duxbury Project Sites

Site

Annual EnergyConsumption

(MWh)

Duxbury High School 1,431

Duxbury Middle School & Alden Elementary 1,860

Chandler Elementary 664

Duxbury Transfer Station 98

North Hill Golf Course1

N/A

Duxbury Town Hall/DPW Facility 235

Total2

4,288

[1] Energy consumption not provided as part of the Municipal WindTurbine Site Survey Application.

[2] Does not include North Hill Golf Course.

In addition to net metering, other state or federal incentives may be available for a municipallyowned project, which should be evaluated to determine the economic feasibility of development.

Access to high-voltage transmission lines is a critical component of wind project development.

Publicly available data regarding transmission lines indicate the nearest lines (115 kV) arelocated approximately 1.5 kilometers northwest of the project sites, as shown in Figure 9.

However, a community scale project would likely interconnect to the local distribution grid,

which is at a lower voltage. Interconnection to a three-phase power line would be required for awind project of the scale being considered in this report. If any of the projects move forward,

DNV-GEC recommends that the interconnection and transmission systems be analyzed todetermine where power could be delivered into the grid and what constraints, if any, might exist.

The net metering tariff for the local utility will likely include provisions regardinginterconnection requirements.


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Projection: Massachusetts Mainland State Plane, Meters, NAD83

Data Layer Source: Ventyx (transmission lines); Office of Geographic and Environmental Information (MassGIS)

TransmissionLine (115 kV)

Potential Wind

Project Site

Figure 9. Location of Transmission Lines

Transportation and Site Access

Reasonable access to a potential development area is necessary in order to receive turbine and

tower components and for the mobilization of cranes and other construction equipment.

From Boston, the Town of Duxbury can be reached by Interstate Highway 93 to State Highway3. All sites under consideration are 4 miles or less from the State Route 3 and can be reached via

a combination of State Route 14 or State Route 3A, and local roads. If the sites are accessed fromthe north via Route 14, there is a rotary at the intersection of Route 14 and Lincoln Road just east

of the Route 3 Exit 11 interchange that may pose challenges for delivering large turbine

components or construction equipment. Delivery of components or equipment may be less

challenging from the south via Route 3A.

The accessibility of each site for the delivery and construction of a wind turbine should be

evaluated further if economic analysis indicates benefits of turbine development.

Aviation Conflicts

Wind project sites located close to airports must be installed in a manner that meets federal airspace regulations. The actual effect of a project on air navigation is evaluated on a case-by-case

basis and in consultation with local regulators. Additionally, the Federal Aviation Administration

(FAA) requires that a Notice of Proposed Construction (Form 7460-1) be filed for theconstruction of any object that would extend more than 200 ft above ground level. For each filed

project, the FAA undertakes an initial aeronautical study and issues either a Determination of No

Hazard to Air Navigation (DNH) or a Notice of Presumed Hazard (NPH). If an NPH is issued,


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the FAA will conduct a more extensive analysis to evaluate impacts on air operations. Other

local air space regulations may also apply.

Aviation Systems Report

As an initial step in identifying potential airspace and navigation conflicts, MTC contracted

Aviations Systems, Inc. (ASI) to complete an airspace obstruction evaluation. According to theASI report dated July 6, 2009, the nearest air facility of concern is Marshfield Municipal Harlow

Field; its Runway 06 is located approximately 3.43 nautical miles (NM) from the centerpoint ofASIs 2NM search area. (Note, ASIs search area centerpoint is located at Lat+4202'33.36"/

Lon-7042'21.12" NAD83, near the North Hill Golf Course.) The report also contains a

Maximum Height plot which divided the search area into sectors showing the maximum above

mean sea level (AMSL) height limitations imposed by aircraft and instrument procedures,enroute airways, and radar vectoring altitudes affecting the sector. Based on coordinates

provided in the Municipal Site Survey Application, ASI determined the following maximum

height limitations for turbines that could be erected without incurring a Hazard Determinationfrom the FAA (calculated in accordance with FAR Part 77 and FAA Orders 7400.2 and

8260.3B): Duxbury High School: limited to 324 ft (98.8 m) above ground level (AGL) by the traffic

pattern

Duxbury Middle School and Alden Elementary School: limited to 349 ft (106.3 m) AGLby the traffic pattern

Chandler Elementary School: limited to 170 ft (51.8 m) AGL by the non-directionalbeacon (NDB) primary area

Duxbury Transfer Station: should be approved at 397 ft (121 m) AGL

North Hill Golf Course: limited to 202 ft (61.6 m) AGL by the NDB primary area

Duxbury Town Hall/DPW Facility: should be approved at 397 ft (121 m) AGL

The ASI report also indicates that the North Truro Long Range Radar Site is within 60 NM

(29.19 NM east) of the search area centerpoint and that impact to Air Defense and HomelandSecurity radars is likely. Furthermore, the report concludes that impact is likely to WSR-88D

weather radar operations as the turbines will likely be in the radars line of sight. As such, the

report recommends that further radar impact study may be advisable.

VOR

FAA rules prevent a structure the size of a typical utility-scale wind turbine from being erected

within at least 0.62 mi (1 km) of a VHF Omni-directional Radio Range (VOR) station.

1

In DNV-GECs experience, these FAA-operated radio navigation systems have proven to be a fatal flawwhen in close proximity to a proposed wind development site. Due to the omni-directional nature

of the signals transmitted by these navigation aids, tall structures, such as the turbine towers, in

the vicinity of the VOR may interfere with signal transmittal. DNV-GEC has identified VOR

1Aviation Systems Inc. Airspace Obstruction and Electromagnetic Interference Considerations for Wind Power

Projects. January 2007. Massachusetts Technology Collaborative.


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stations located approximately 25 mi north and 36 mi east of Duxbury. Since these VOR

facilities are located a sufficient distance from the sites, DNV-GEC does not anticipate that thesefacilities will impact turbine development at any of the sites under consideration.

Radar

To supplement the evaluation completed by ASI, DNV-GEC also assessed the potentialinterferences with radar systems. DNV-GEC utilized the FAA online Long-Range Radar Tool

which provides a preliminary estimate of the effect of a wind power project on Air Defense andHomeland Security radar. As shown in Figure 10, the area including and surrounding the Town

are flagged as yellow and red, which are defined as likely (yellow) and highly likely

(red) to impact Air Defense and Homeland Security radars. Although these designations do not

necessarily prohibit wind power development at the sites under consideration, a more detailedaeronautical study, including potential impacts on other types of radar, is required to determine

the extent of the impact and possible mitigation strategies.

Figure 10. Results of FAA Long-Range Radar Screening Tool


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The FAA online NEXRAD (Next Generation Weather Service Radars) tool provides a

preliminary estimate of the effect of a wind power project on weather radar. As shown inFigure 11, the area in and surrounding the Town is flagged as yellow, which is defined as

likely to impact weather radar operations and wind turbine electronics. The NEXRAD Program

guideline advises that the best mitigation technique is to avoid locating wind turbines in the

radar-line-of-sight of a NEXRAD unit. This mitigation strategy may be achieved by distance,terrain masking, or terrain relief and requires case-by-case analysis. The NEXRAD Program

administrators would prefer the wind energy industry provide information on planned projects,

new or expansions, to NEXRAD Program in advance. Due to the potential small-scale nature ofprojects in Duxbury, DNV-GEC does not anticipate that the yellow designation will prohibit

development; however, DNV-GEC recommends consultation with NEXRAD personnel prior to

development.

Figure 11. Results of FAA NEXRAD Screening Tool


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Environmental Issues and Permitting

DNV-GEC completed a geographic information system (GIS) analysis to determine the location

of sensitive habitat relative to the proposed wind project sites. Results of the GIS analysis areshown in Figure 12 through Figure 14.

Projection: Massachusetts Mainland State Plane, Meters, NAD83Data Layer Source: Office of Geographic and Environmental Information (MassGIS)

Protected & RecreationalOpen Space

National WetlandsInventory

Priority Habitat for RareSpecies

Core Habitat

Scenic Landscape

State Register of HistoricPlaces

Site Boundaries


Duxbury High School, Duxbury Middle School, and Alden Elementary School


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Core Habitat

Scenic Landscape


Site Boundaries


Chandler Elementary





Core Habitat

Scenic Landscape


Site Boundaries

Figure 14. Areas of Environmental and Cultural Significance in the Vicinity of DuxburyTransfer Station, North Hill Golf Course, and Duxbury Town Hall/DPW Facility


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Each environmental and cultural data layer described below was obtained from the

Massachusetts Office of Geographic and Environmental Information (MassGIS). These datalayers are made available to the public for planning purposes only. More detailed site-specific

analyses should be completed to verify the accuracy of these data layers.

Areas of Critical Environmental Concern (ACEC), layer last updated March 2007

ACEC are designated by the Secretary of Environmental Affairs as places that receivespecial recognition because of the quality, uniqueness and significance of their naturaland cultural resources. The Hockomock Swamp and the Canoe River Aquifer,

designated as ACEC, are located approximately 25 km west of the properties of interest.

NHESP BioMap Core Habitat, layer last updated June 2002 Core Habitat areas areidentified by the Natural Heritage and Endangered Species Program (NHESP) of the

Massachusetts Division of Fisheries and Wildlife as areas that provide the most viablehabitat for rare species and natural communities in Massachusetts. As shown in

Figure 12 through Figure 14, the northern tip of Site 1 (High School, Middle School, and

Alden Elementary) and approximately the southern two-thirds of Site 3 (Transfer Station,

Golf Course, and Town Hall) are designated as Core Habitat. Large areas north and eastof Site 1 and west of Site 3 also have this designation. Although this designation may not

necessarily prohibit wind development, a proposed project may require an increased levelof environmental review. Consultation with NHESP is recommended to verify this

designation and to determine potential impacts and mitigation strategies.

NHESP Priority Habitats for Rare Species, layer last updated September 2006 Priority Habitats are identified based on observations documented within the last 25 years

in the database of the NHESP, as published in the 12th

Edition of the Massachusetts

Natural Heritage Atlas. The northern and southern ends of Site 1 and approximately thewestern half and the southeastern edge of Site 3 are designated as Priority Habitats.

Significant amounts of land surrounding the project sites also have this designation.

Although this designation may not necessarily prohibit wind development, a proposedproject may require an increased level of environmental review. Consultation with

NHESP is recommended to verify this designation and to determine potential impacts and

mitigation strategies.

National Wetlands Inventory (NWI), layer last updated October 2007 The NWI dataset was created by the U.S. Fish and Wildlife Service to identify the approximate locationand characteristics of wetlands and deepwater habitats. All of the properties of interest

contain areas designated as wetlands within the property boundaries, including the

northern and southern ends of Site 1, a portion within Site 2 near the northeastern end,and numerous areas within the boundaries of Site 3. Several wetlands areas are also

present adjacent to the subject properties. Although this designation may not necessarily

prohibit wind development, a proposed project may require an increased level of

environmental review.

Protected and Recreational Open Space, layer last updated January 2007 This datalayer includes conservation land and outdoor recreation facilities, including parkways,

town parks, playing fields, and walking trails owned by federal, state, county, municipal,

and nonprofit enterprises. As shown in Figure 12 through Figure 14, nearly all of the landwithin the boundaries of each site is designated as Protected and Recreational Open


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Space. Although this designation may not necessarily prohibit wind development, a

proposed project may require an increased level of community review. Areas within Site3 have an active trail system that is used for hiking and biking. Impacts of a wind project

on this recreational resource may pose a significant risk to development. It should be

noted that an error in the MassGIS Protected and Recreational Open Space data file

causes the layer to appear misaligned in some areas. This issue has been taken intoaccount in DNV-GECs setback analysis.

Scenic Landscapes, layer last updated July 1999 Scenic landscapes are identified bythe Massachusetts Landscape Inventory Project in the Department of Conservation and

Recreation. Portions of Site 1 near the northern and southeastern ends are designated asScenic Landscapes. Sites 2 and 3 do not contain areas with this designation. Although

this designation may not necessarily prohibit wind development, a proposed project may

require an increased level of environmental review.

State Register of Historic Places, layer last updated January 2000 This data layer,maintained by the Massachusetts Historical Commission, denotes locations or boundaries

of significant historic properties and sites with legal designations under several specificlocal, state, and federal statutes. The closest Historic Place is the Old Shipbuilders

Historic District, located approximately 0.3 km from Site 1, 1.3 km from Site 3, and over4 km from Site 2.

A map of Important Bird Areas on the south shore of Massachusetts was obtained from theMassachusetts Audubon Society as shown in Figure 15. An Important Bird Area is a site that

provides essential habitat to one or more species of breeding, wintering, or migrating birds.

These sites typically support high-priority species, large concentrations of birds, exceptional bird

habitat or have substantial research or educational value. The potential project sites are locatednear the Plymouth and Duxbury Bays which are each designated as an Important Bird Area for

various species of migratory land birds, water fowl, and seabirds. Consultation with the

Massachusetts Audubon Society is recommended to determine impacts and mitigation strategiesrelated to a potential wind project in the area.


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Figure 15. Important Bird Areas

Wind power projects on public land, such as at the Duxbury sites, might also be affected by

Article 97. This amendment to the Massachusetts Constitution, passed by voters in 1972, grants

its citizens specific environmental rights on publicly owned land equivalent to those of speechand worship. The law requires that any land or easements taken or acquired by the state for

natural resource purposes shall not be used for other purposes unless the Massachusetts

legislature approves the change by a two-thirds vote. The extent to which this law would affectdevelopment at the Duxbury sites is not clear at this time. DNV-GEC recommends further

investigation into the Towns articles of acquisition for the properties under consideration to

determine whether the properties were acquired for natural resource purposes.

Additionally, the Site Assessment Application identified other potential land use restrictions at

each site. Site 1 is within two watersheds: the Black River Watershed (Duxbury High School)

and the Bluefish River Watershed (Duxbury Middle School and Alden Elementary School). Site2 is designated as a Zone 2 aquifer protection area

2. Although this may not prohibit wind

development, a proposed project may require an increased level of environmental review.

The permitting process and implications of each of these environmental designations is notclearly defined and can vary from site to site. A site-specific environmental survey is

recommended in order to address potential conflicts.

2A Zone 2 aquifer protection area is defined as the Massachusetts Department of Environmental Protection (DEP)

approved area of an aquifer which contributes water to a well under the most severe pumping and recharge

conditions that can be realistically anticipated as defined in 310 CMR 22.00.


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Telecommunications Conflicts

Wind turbines, like all tall structures, can create interference or degradation of certain

communication signals if they are located in the line-of-sight of any communications equipmentsuch as microwave, radio, or satellite dishes. A number of microwave communication stations

are located around the potential development areas, as seen in Figure 16. Table 4 provides the

approximate distance from the project site boundary to the nearest microwave communicationstation. Analysis of microwave line-of-sight is beyond the scope of this review. Further analysis

is required, which would take into account the proposed turbine dimensions, turbine location,

and transmittal paths of various types of communication signals in the area.

Projection: Massachusetts Mainland State Plane, Meters, NAD83Data Layer Source: Federal Communications Commission, July 2007; Office of Geographic and Environmental

Information (MassGIS)

MicrowaveTower

Potential WindProject Site

Projection: Massachusetts Mainland State Plane, Meters, NAD83Data Layer Source: Federal Communications Commission, July 2007; Office of Geographic and Environmental

Information (MassGIS)

MicrowaveTower

Potential WindProject Site

Figure 16. Location of Microwave Towers in the Area of the Potential Wind Turbine Sites

Table 4. Distance of Project Sites to Nearest Microwave Tower

Site

Distance to NearestMicrowave Tower

(km)

High School, Middle School, and Alden Elementary 6.8

Chandler Elementary 5.2

Transfer Station, Golf Course, Town Hall/DPW 5.8


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Community Impacts

Primary social impacts of a wind turbine project on a community include noise from the wind

turbine blades and generator and the visual impact of the wind turbine on the landscape.Negative social impacts have the potential to inhibit or terminate wind project development, and

the costs and time required for development may increase significantly.

When operating, wind turbines produce a swishing or whooshing sound as their rotating

blades encounter turbulence in the passing air, as well as some sounds from the mechanical parts

such as the gearbox, generator, and cooling fans. Wind turbines are typically quiet enough for

people to hold a normal conversation while standing at the base of the tower. If mechanicalsounds are significant, it usually means something in the nacelle needs maintenance or repair. At

a distance, the sounds generated by a wind turbine are typically masked by the background

noise of winds blowing through trees or moving around obstacles.

Massachusetts state regulations allow for an increase in noise levels of up to 10 dB over normal

background levels at the property boundary. To minimize the noise impact of a project, a wind

turbine should be placed at a distance from the property boundary of approximately 1.5 to4 times the hub height of the turbine, depending on the background noise levels at the site,

terrain, and the turbine size and type. Due to this variability in sound impact setbacks, DNV-GEC recommends a sound impact study be performed prior to development. For the purposes of

this study, DNV-GEC has taken a minimum noise setback of 1.5 times the turbine tip height

from residences and other occupied structures into account when evaluating the potential project

scale at each site. There are several residences located on Hounds Ditch Lane and along TremontStreet that may potentially be impacted by noise from a wind project at Site 3.

The proposed Cape Wind project in Nantucket Sound, approximately 45 miles southeast of thepotential Duxbury project sites, has received significant public opposition due to concerns about

the aesthetic impact on the landscape. Although a wind project at the Duxbury project siteswould be much smaller in scale, a wind turbine may be highly visible and visual concerns might

cause opposition to the project. Photo simulations of a potential wind project, as well as

informational community meetings, may help to allay these concerns.

Another potential community impact is shadow flicker that can be generated by the rotating

blades of a wind turbine during certain ambient lighting conditions. The shadow of the rotatingblades can cause an annoyance until the sun changes position in the sky. Due to the presence of

residential parcels adjacent to the each of the sites, DNV-GEC recommends a shadow flicker

analysis be completed once turbine dimensions and locations are specified.

Foundation ConsiderationsThe subsurface conditions of the proposed Duxbury sites as described in the Municipal Wind

Turbine Site Survey Application to MTC are summarized in Table 5.


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Table 5. Subsurface Conditions of the Proposed Sites

Site Subsurface Conditions

Duxbury High School sandy

Duxbury Middle School & AldenElementary

sand and clay

Chandler Elementary sandy

Duxbury Transfer Station soil/sandy

North Hill Golf Course soil/sandy

Duxbury Town Hall/DPW Facility soil/sandy

Of the sites under consideration, the Transfer Station is the only site with known subsurfaceconditions that could significantly impact the design and cost of a wind turbine foundation.

According to the Municipal Wind Turbine Site Survey Application, a portion of the Transfer

Station is a capped landfill upon which no construction shall be done.

Setback Requirements and Project ScaleThe Town of Duxbury currently has draft bylaws specifically addressing construction andsetback restrictions for wind facilities. The bylaws state that utility-scale, community-scale,

residential, private and small scale wind facilities shall not be constructed in the following

zoning districts: Flood Hazard Overlay District; Dunes Protection District; and WetlandsProtection Overlay District. The bylaws also state that community-scale and utility-scalewindfacilities shall be no higher than 250 ft (76.2 m) above the current grade of the land. The bylaws

define the height of a wind turbine as the distance measured from natural grade to the tip of the

rotor blade at its highest point. Regarding setbacks, the draft bylaws state the following:

Utility Scale and Community ScaleWind Turbines shall be set back a minimumdistance equal to 1.1 times the overall height of the wind turbine from the nearestproperty line and private or public way and a minimum distance equal to 2 times

the overall height of the wind turbine from the nearest existing residential or

commercial structure. Residential, Private & Small Scale Wind Turbines shall be

set back a minimum distance equal to 1.1 times the overall height of the wind

turbine from the nearest property line and private or public way, but can be

within the minimum distance of 2 times the overall height of the wind turbine from

the nearest existing residential or commercial structure, provided that the nearest

existing residential or commercial structure is owned by the resident or private

property owner seeking to permit the Wind Turbine. The setback zone for Utility

Scale, Community Scale, and Residential, Private & Small Scale Wind Turbines

can fall within the limits of Wetlands Protection Overlay and the Flood HazardOverlay Districts.

DNV-GEC has performed a preliminary analysis of available developable land and project scale

at the potential project sites. For this analysis, DNV-GEC generated a list of utility-sized turbines

that might be used at these sites. Table 6 presents a range of potential turbine models, withcorresponding dimensions, used in our evaluation of potential project sizes. In accordance with

the draft bylaws, only models with maximum tip heights (MTH) less than 250 ft (76.2 m) are


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listed. The availability of these turbine models in small quantity orders would need to be

evaluated, should a detailed feasibility study be performed.

Table 6. Potential Turbine Models

Turbine Model

RatedCapacity

(kW)

RotorDiameter

(m)

HubHeight

(m)

MaximumTip Height

(m)

Americas Wind Energy AWE 52-900 900 52 50 76

Elecon Turbowinds T-600-48DS 600 48 50 74

Enertech E-48 600 48 50 74

Vestas RRB PS600 600 47 50 73.5

Aeronautica Norwin 29-225 225 29 40 54.5

Aeronautica Norwin 47-750 750 47 50 73.5

Northern Power Systems NW100/21 100 21 30/37 40.5/48.5

In addition to the setbacks specified in the draft bylaws described above, DNV-GECrecommends other safety setbacks be applied. Wind turbines, like other forms of energy

generating equipment, are operating pieces of machinery that can experience catastrophic

failures. Although very rare, the potential for fire, structural failure, or control system failuremust be considered in evaluating potential project risks. DNV-GEC considers elementary,

middle, and high school campuses, like other areas highly frequented by the public (sports fields

and recreation areas), to be particularly sensitive locations for potential wind turbine placementfrom a safety and setback perspective. With these factors in mind, DNV-GEC evaluated the

school properties using a safety setback of at least 2 times the MTH from school buildings,parking lots, sports fields, and other school facilities. At the Transfer Station, Golf Course, and

Town Hall/DPW sites, where site access is more controlled, DNV-GEC used a safety setbackequivalent to at least 1.5 times the turbine MTH from site use areas and facilities as well asnearby residences. In all cases, this safety setback area should be clear of occupied buildings,

roads, or other areas frequented by the public and on-site personnel.

As indicated in the draft bylaws, turbines may not be placed in designated wetlands; however,there are no minimum setbacks required from these areas.

As stated previously, Massachusetts state regulations allow for an increase in noise levelsresulting from a wind turbine of up to 10 dB over normal background levels at the property

boundary. As specified in the draft bylaws, a minimum property boundary setback of 1.1 times

the MTH has been applied in this analysis; however, a sound impact study should be performedprior to development.

The potential scale of each site under consideration was evaluated by applying the setbacks

discussed above in conjunction with the maximum height restrictions previously identified byASI in the Aviation Conflicts Section. Following is a summary of each sites potential scale

based on our review of aerial imagery, GIS layers, and the parcel boundaries.


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Site 1 - Duxbury High School, Duxbury Middle School, and Alden ElementarySchool

ASI determined that a turbine placed near the high school would be limited to 98.8 m AGL, anda turbine placed near the middle school/elementary property would be limited to 106.3 m AGL.

As such, any of the potential turbine models listed in Table 6 may be appropriate. Using 76 m as

the MTH, sufficient area exists at Site 1 to accommodate a 100 to 900 kW scale turbine whilemaintaining the minimum setback distance of 1.1 times the MTH (83.6 m) from the site property

boundaries. However, the recommended minimum safety setback distance of 2 times the MTH

(152 m) from the school buildings and recreational fields would not be satisfied. The potentialdevelopment area is further limited by the land designated as wetlands, which occupies most of

the northern and southern ends of the site (as shown in Figure 12). As such, DNV-GEC does not

recommend further evaluation of Site 1.

Site 2 - Chandler Elementary School

ASI determined that a turbine placed near the Chandler Elementary School would be limited to amaximum height of approximately 52 m AGL. As such, the 100 kW Northern Power Systems

NW100/21 turbine with 48.5-m MTH was evaluated for this property. Sufficient area exists atChandler Elementary School to support this 100kW turbine located outside of the designated

wetlands while maintaining the minimum setback distances from the adjacent properties,buildings, and school facilities. A potential wind turbine location with associated setbacks is

illustrated in Figure 17.

Projection: Massachusetts Mainland State Plane, Meters, NAD83

Data Layer Source: Office of Geographic and Environmental Information (MassGIS)


48.5-m MTH x 1.1

Property BoundarySetback

48.5-m MTH x 2 SafetySetback from Buildingsand School Facilities

Potential Turbine

Location

Site Boundaries

Figure 17. Site 2 - Potential Turbine Location


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The proposed wind turbine location was selected based on currently available information on the

project boundary and setback requirements. Additional factors may influence the final windturbine location, such as a surveyors verification of the property boundary, subsurface

conditions, constructability of the site, environmental permitting, FAA restrictions, conflicts with

communications equipment, noise and shadow flicker impact analysis, and others.

Site 3 - Duxbury Transfer Station, North Hill Golf Course, and Duxbury TownHall/DPW Facility

ASI determined that a turbine placed by the north end of the site near the golf course would be

limited to 61.6 m AGL and would linearly increase in height to 121 m AGL toward the south end

of the site near the town hall and transfer station. Given a turbine would likely be placed

somewhere between these ends, DNV-GEC assumed the use of a turbine with 76-m MTH forthis evaluation (i.e., the maximum height per the draft bylaws). Using this MTH, sufficient area

exists within Site 3 to support multiple turbine locations outside of the designated conservation

areas and wetlands while maintaining the minimum setback distances from the adjacentproperties, buildings, and site facilities. According to the Municipal Wind Turbine Site Survey

Application, the Town is currently interested in pursuing a single turbine project. However, thissite may be able to support multiple turbines. Based on the current land use at Site 3, however,community reaction to multiple turbines at the site may be negative due to the impact on

recreation activities on the property. A single turbine project would likely have less impact on

the community and the environment and, therefore, be more likely to be feasible for this site.

During the site visit, two potential turbine locations were identified as shown in Figure 18. The

approximate coordinates and elevation for these locations are shown in Table 7. Both locations

meet the setback parameters used in this assessment. Location 1 is in a forested area just west ofthe DPW Facility, while Location 2 is near the center of a clearing just east of the dumping area

adjacent to the North Hill Golf Course. Although Location 1 is at a higher elevation and may

have a slightly better wind resource, a wind turbine at Location 2 would likely have less of animpact on the recreational use of the property.

Table 7. Potential Site 3 Turbine Location Coordinates and Elevation

Coordinates

(MA State Plane Meters, NAD83)

Location Easting Northing Elevation (m)

Location 1 266698 865628 22

Location 2 266397 866099 13


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76-m MTH x 1.1Property BoundarySetback

76-m MTH x 1.5 SafetySetback from Site Use

Areas and Facilities

Potential TurbineLocation

Site Boundaries



76-m MTH x 1.1Property BoundarySetback

76-m MTH x 1.5 SafetySetback from Site Use

Areas and Facilities

Potential TurbineLocation

Site Boundaries

Figure 18. Site 3 Potential Turbine Locations

The proposed turbine locations were selected based on currently available information on the

project boundary and setback requirements. Additional factors may influence the final wind

turbine location, such as a surveyors verification of the property boundary, subsurfaceconditions, constructability of the site, environmental permitting, FAA restrictions, conflicts withcommunications equipment, noise and shadow flicker impact analysis, and others.

Estimated Capacity Factors

Based on an evaluation of developable area, aviation height restrictions, and setback

requirements, DNV-GEC has estimated the scale of a turbine that each site could accommodate,

and calculated the estimated net annual energy production for sample turbine models. As anexample and for the purposes of this report, DNV-GEC calculated the estimated net annual

energy production for 100 kW to 900 kW turbines as appropriate for Sites 2 and 3. Energy was

estimated at each site for a single turbine project.

To calculate annual energy production, DNV-GEC used an estimated annual average wind speed

range based on the New England Wind Map at a 70-m measurement height, given in Figure 6.

The New England Wind Map provides an estimated Weibull shape factor for each site that wasused to create an annual wind speed frequency distribution. The wind speeds were adjusted to the


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hub heights using the power law3

and an estimated wind shear exponent, calculated from the

average annual wind speeds at various heights provided by the New England Wind Map. Theestimated Weibull shape factor and calculated wind shear exponent for each site is given in

Table 8. Energy calculations are based on the manufacturer-provided power curves at the

standard air density of 1.225 kg/m3.

Table 8. New England Wind Map Weibull Shape Factor and Wind Shear Exponent

Weibull ShapeFactor (k)

EstimatedShear ()

Site [no units] [no units]

Site 2 Chandler Elementary 2.41 0.22

Site 3 Transfer Station, GolfCourse, Town Hall/DPW Facility

2.38 0.22

DNV-GEC estimates aggregate energy losses of 15% for single turbine projects, as listed in

Table 9. Each loss category is independent; therefore, losses are combined by multiplying eachenergy retention percentage. Availability losses account for scheduled and unscheduled

maintenance, faults, and downtime for troubleshooting. Each of these events reduces the time

that the turbine is available to generate energy and, therefore, each is considered a loss.

Transformer and line losses include line losses in the transmission lines between the turbines andthe grid connection point and in the on-site distribution system and transformers. Transformer

and line losses are expected to be low at the sites because of the close proximity of the wind

turbine(s) to the likely interconnection point. Control system and power curve losses account fortimes when the automated operation of the turbine lags frequent changes in wind speed or

direction, causing the turbine to not perform exactly as predicted by the manufacturers power

curve. Blade soiling, which occurs with the accumulation of dirt, insects, or ice, impacts the

aerodynamics of the blades, thus lowering production. Wake losses refer to lost energyproduction caused by nearby obstructions or by turbines located downwind of other turbines

when more than one turbine is present at a site.

3 The power law is defined by the equation VZ = VR(HZ/HR), where VZ and VRare wind speeds at the turbine hub

height HZ and the measurement height HR, respectively (above ground level), and is the dimensionless wind shear

exponent. This is a typical method of describing the extent to which wind speeds change with increasing heightabove the ground.


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Table 9. Estimated Energy Losses Single Turbine

Energy Loss Description Energy Losses

Availability 6%

Transformer/Electric Line 1%

Turbulence/Control System 2%

Blade Soiling/Degradation 2%

Icing/Weather 3%

Power Curve 2%

Wake 0%

Total Losses 15%

The energy production and capacity factor estimates for different wind turbine options are listedin Table 10 and Table 11 for Site 2 and Site 3, respectively. These figures represent our current

best estimate of the range of P504

values. The estimates rely primarily on the estimated range of

wind speeds at the sites, which can have a high degree of uncertainty. Other sources of

uncertainty, such as annual variability in the wind resource, system energy losses, the shape ofthe wind frequency distribution, and other factors are not included in this preliminary analysis

and would further increase the range of possible capacity factor values.

Table 10. Estimated Net Energy Production at Site 2 Chandler Elementary

Turbine ModelNorthern Power Systems

NW100/21

Hub Height 37 m

Hub-Height Wind Speed (m/s) 5.1 6.2

Gross Energy (MWh)1

146 230

Net Energy (MWh) 124 195

Net Capacity Factor 14% 22%

% of On-Site Annual Energy Consumption2

19% 29%

% of Aggregate Annual Energy Consumptionfor all Sites

3

3% 5%

[1] Energy values based on one turbine

[2] Based on energy consumption data provided for Chandler Elementary(664 MWh). See Table 3.

[3] Based on energy consumption data provided for all sites (4,288 MWh),excluding North Hill Golf Course. See Table 3.

4The P50 value represents the average expected value or, the value below which 50% of the outcomes are

expected to be found.


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Table 11. Estimated Net Energy Production at Site 3 Duxbury Transfer Station, NorthHill Golf Course, and Duxbury Town Hall/DPW Facility

Turbine Model AWE 52-900Turbowinds

T-600Enertech E-48

VestasRRB600

AeronauticaNorwin 47-750

Hub Height (m) 50 50 50 50 50

Hub-Height WindSpeed (m/s)

5.5 6.6 5.5 6.6 5.5 6.6 5.5 6.6 5.5 6.6

Gross Energy(MWh)

1298 2085 1056 1669 1037 1643 899 1450 1048 1693

Net Energy (MWh) 1104 1772 898 1419 881 1397 764 1233 890 1439

Net Capacity Factor 14% 22% 17% 27% 17% 27% 15% 23% 14% 22%

% of On-Site AnnualEnergyConsumption

1

332% 532% 270% 426% 265% 420% 229% 370% 267% 432%

% of AggregateAnnual EnergyConsumption for all

Sites

2

26% 41% 21% 33% 21% 33% 18% 29% 21% 34%

[1] Based on energy consumption data provided for the Transfer Station and Town Hall/DPW (333 MWh total). Data notprovided for the golf course. See Table 3.

[2] Based on energy consumption data provided for all sites (4,288 MWh), excluding North Hill Golf Course. See Table 3.

The turbine type and the number of turbines chosen for each site will affect how much of thegenerated electricity might be used on site and aggregated to offset energy consumption at other

Town facilities, as allowed by the new virtual net metering law.

DNV-GEC estimates that Site 2 could potentially accommodate one 100 kW scale turbine, which

could account for approximately 19% to 29% of the annual energy consumption at the site

facility and 3% to 5% of the aggregate annual energy consumption for all sites evaluated (seeTable 10). Net excess electricity would likely not be generated.

DNV-GEC estimates that a single turbine at Site 3 could accommodate a 600 kW to 900 kWscale turbine, which could account for up to approximately 229% to 532% of the combined

annual energy consumption of the Transfer Station and Town Hall/DPW facility and 18% to

41% of the aggregate annual energy consumption for all sites evaluated (see Table 11).

Under the new net metering law, net metering facilities that are owned by a municipal or other

government entity are limited to a maximum capacity of 2 MW per unit which allows fordevelopment of multiple turbine projects, provided that each turbine does not exceed 2 MW. If

multiple turbines are installed at Site 3 the percentage of the annual energy consumption that thefacility would account for would be approximately proportionate to the number of turbines.Under a private ownership scenario, the project would be limited to a total of 2 MW for the

entire facility which may limit the number of turbines, depending on the turbine model.

However, as discussed above, a single turbine project is likely more feasible at this site.


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Conclusions

The Town of Duxbury identified six possible sites for a potential wind power project:

Duxbury High School

Duxbury Middle School and Alden Elementary School

Chandler Elementary School

Duxbury Transfer Station

North Hill Golf Course

Duxbury Town Hall and Department of Public Works (DPW) Facility

Due to the close proximity of the high school and middle school, these two sites were grouped

together and evaluated as a single site. Similarly, the Transfer Station, Golf Course, and TownHall/DPW facility, which are also situated adjacent to each other, were grouped together andevaluated as a single site. Using these site groupings, DNV-GEC completed a desktop review to

identify possible fatal flaws and wind energy development potential for each location.

The potential project sites are estimated to have a Class 2 wind resource, which, based on DNV-

GECs experience, is likely to result in a marginally economic project. The capacity factor isexpected to be in the range of 13% to 29% depending on the site(s) selected, the measured wind

resource, turbine size and model, and other factors. Recent changes in the Massachusetts net

metering law now allow any net excess electricity generated during a given month by amunicipal or government wind power project rated at 2 MW or less per unit to be credited to the

customers next monthly utility bill at the retail rate, and to be credited towards several differentloads with multiple utility meters, as long as the meters are under the same distribution companyand located in the same ISO-NE load zone. As this new law discounts the need for on-site

electrical load, project economics are expected to improve with turbine size.

Below is a summary of development potential for each potential site:

Site 1 - Duxbury High School, Duxbury Middle School, and Alden ElementarySchool

After examination of the available land area, maximum height restrictions, and minimum

recommended setbacks, DNV-GEC estimates that there is insufficient area at Site 1 to

accommodate an industrial scale wind turbine. DNV-GEC recommends this site be removedfrom further development consideration.

Site 2 Chandler Elementary

After examination of the available land area, maximum height restrictions, and minimum

recommended setbacks, DNV-GEC estimates that Site 2 could accommodate up to one 100 kW

scale turbine. ASI determined that a turbine placed near the Chandler Elementary School would


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be limited to a maximum height of approximately 52 m AGL. Therefore, the 100 kW Northern

Power Systems NW100/21 turbine with 48.5-m MTH was evaluated for this property. Based onthe estimated wind speeds at the site and available load data, DNV-GEC estimates one 100 kW

scale turbine could produce 124 MWh to 195 MWh of energy per year, satisfying 19% to 29% of

the annual site energy consumption and 3% to 5% of the aggregate annual energy consumption

for all sites evaluated.

Although a turbine could be located on the school property satisfying minimum recommended

setbacks, DNV-GEC does not recommend installation of a wind turbine at this location for thefollowing reasons:

Potential safety concerns related to operating equipment near areas highly frequented bythe public (particularly children);

Elevated risk the turbine may pose as an attractive nuisance; and

DNV-GEC believes Site 3 (discussed below) offers a better development opportunity interms of energy production, safety, and community acceptance.

As such, DNV-GEC recommends Site 2 be removed from further development consideration.

Site 3 - Duxbury Transfer Station, North Hill Golf Course, and Duxbury TownHall/DPW Facility

After examination of the available land area, current land use practices, maximum heightrestrictions, and minimum recommended setbacks, DNV-GEC determined that sufficient area

exists within Site 3 to support a community scale wind project and has identified two potential

turbine locations. Although there is sufficient area at this site for multiple turbines, a single-turbine project would likely be more feasible at this site primarily due to community acceptance

issues. For a single-turbine project, Site 3 could accommodate a 600 kW to 900 kW scale

turbine, which could account for up to approximately 229% to 532% of the combined annualenergy consumption of the Transfer Station and Town Hall/DPW facility and 18% to 41% of the

aggregate annual energy consumption for all sites evaluated. As permitted by current net

metering laws, net excess generation from a net metering facility can be credited toward the

Towns aggregate utility bill.

DNV-GEC has identified on-site areas characterized as Wetlands, Primary Habitat for Rare

Species, Core Habitat, and Protected and Recreational Open Space according to NHESP

designation. The presence of these designated areas at and near the site may not prohibit wind

power development; however, a proposed project may require an increased level ofenvironmental review. DNV-GEC recommends consultation with NHESP.

DNV-GEC recommends further evaluation of Site 3. In order to verify the findings of thisdesktop study, a site visit is recommended. In addition to field verification of the information

provided in this review, items that should be completed during a site visit include identification

of potential met tower locations, identification of potential obstructions to wind flow, meetingwith local representatives, and gathering other relevant information necessary to perform a

feasibility study.


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Met Tower Recommendations

If the Town desires to move forward with a wind project at this site, DNV-GEC recommends

installation of a meteorological tower at the project site to collect on-site wind resource datanecessary for a detailed feasibility study. DNV-GEC recommends the installation of a 50-m met

tower at Site 3. Ideally a met tower would be placed at the exact location of the future wind

turbine to collect wind resource information for a period of one year. Location 1 is in a forestedarea that would require clearing a significant area for installation of a met tower and access to the

location. Location 2 is in a clearing that is currently accessible with an off road vehicle.

Figure 19 and Figure 20 show the vegetation at Location 1 and Location 2, respectively.

Minimal, if any, clearing would be required for installation of a met tower at Location 2. Due tothe minimal amount of clearing required at Location 2, installation costs for a met tower will

likely be significantly less at Location 2 compared to Location 1. Additionally, environmental

and recreational impacts will be minimal at Location 2 compared to Location 1. For thesereasons, DNV-GEC recommends that the met tower be placed at Location 2. Although Location

2 is at a lower elevation than Location 1, wind resource information collected at Location 2

would be reasonably representative of the expected wind resource at either potential turbine

location.

Figure 19. Example of Vegetation at Location 1


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Figure 20. View of Location 2 from the Northeast

Additional Recommendations

Upon completion of the wind resource assessment phase, the Town would initiate a detailed

feasibility study including:

Revised energy assessment based on measured meteorological data

Additional aeronautical impact study to determine if any air space conflicts would exist atthe proposed turbine locations

Additional communications interference study to determine whether the proposedturbines would cause interference with microwave, radar, and radio signals

A geotechnical investigation to determine the design and cost of turbine foundations

An environmental study to verify the Wetlands, Primary Habitat for Rare Species, CoreHabitat, and Protected and Recreational Open Space designations

A transportation study to confirm site access and constructability


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An interconnect and transmission system analysis to investigate interconnection locationsand determine where power could be delivered into the grid and what constraints, if any,

might exist

Photo simulations from viewpoints of concern and shadow flicker analysis onsurrounding residences

Project financial evaluation including an evaluation of net-metering options and scenarios

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Wind Turbine Assessment

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