epri environmental sector meetings optimal routing and corridor analysis for electric transmission...

EPRI Environmental Sector Meetings

Optimal Routing and Corridor Analysis for Electric Transmission Line Siting

Procedures for Infusing Stakeholder Perspective in Identifying Optimal Route Alternatives

Joseph K. BerryUniversity of Denver, Geography

Christy JohnsonGeorgia Transmission Corporation

Water & Ecosystem Area Council MeetingBoston, MA — September 29, 2004

In 2002, The Electrical Power Research Institute (EPRI) and Georgia Transmission Corporation (GTC) entered into a Tailored Collaboration Project to examine and refine GTC’s existing Overhead Electrical Transmission Line Siting

Methodology. The scope of the project was to develop new transmission line siting tools, techniques and procedures for GTC that are objective, quantitative, predictable, consistent, and defensible and to prepare a Overhead Electrical Transmission Line Siting Methodology Report that explains and documents the process. Among the longer-term goals of this project is

exploration of the prospects and opportunities of standardizing the decision process for overhead electrical transmission line siting for the electrical industry.

http://www.epri.com/

Presentation Topics

Understanding the Basic Routing Process

Identifying Optimal Route and Corridor Generating Alternative Routes

Applying Process to Electric Transmission Line Routing

Macro Corridor Identification Alternative Corridor Generation Development of Alternative Routes within Alternative Corridors Alternative Route Analysis Selection of the Preferred Route


Simplified Example

Criteria – the transmission line route should…

Avoid areas of high housing density

Avoid areas that are far from roads

Avoid areas within or near sensitive areas

Avoid areas of high visual exposure to houses

Houses

Roads

Sensitive Areas

Houses

Elevation

Goal – identify the best route for an electric transmission line that considers various criteria for minimizing adverse impacts.

Existing Powerline

Proposed Substation


Routing Model Flowchart (Model Logic)

Model logic is captured in a flowchart where the boxes represent maps and lines identify processing steps leading to a spatial solution

Far from Roads

In or Near Sensitive Areas

High Visual Exposure

High Housing Density

Avoid areas of…

Fact Judgment

Levels ofAbstraction


Routing Model Flowchart (Model Logic)

Step 1

Identify overall Discrete Preference (1-9 rating)

Step 1

Three sub models– 1) Discrete Preference, 2) Accumulated Preference and 3) Most Preferred Route

Step 2

Generate an Accumulated Preference surface from the starting location to everywhere

Step 2

Start

CalibrationWeighting

Step 3

Identify the Most Preferred Route from the end location

Step 3

End

End

Start


Discrete Preference Surface (Step 1)

HDensity

RProximity

SAreas

VExposure

CalibrationWeighting


Accumulated Preference Surface (Step 2)

Splash Algorithm – like tossing a stick into a pond with waves emanating out and accumulating costs as the wave front moves


Most Preferred Route (Step 3)


Identifying an Optimal Corridor (Nth Best Routes)


Real World Application (Processing Schematic)

B E N

B E N

B E N (avg)

B E N

Built Engr. Natural

CriteriaCriteria

3) The categories on each Criteria Map are calibrated to a range of 1=best to 9= worst for siting a transmission line

ExcludedStakeholderStakeholder

GroupsGroups4) Relative importance weights

for the Criteria Maps within each group are used to

calculate an overall preference map

CategoriesCategories 2) Information that influence transmission line siting are identified

1) Locations that prohibit siting are eliminated

from consideration

ExclusionsExclusions

SlopeHydro-graphy

Flood-plane

PublicLands

ExistingUtilities

Trans-poration

LandCover

ProximityExcluded

ProximityBuildings

etc. etc. etc.

BuildingDensity

VisualExposure

ProximitySchools

Weighting

Calibration

SimulationsSimulations

5) The best route and corridor is determined for conditions

favoring each group’s perspective and one where all

are equally weighted–

Four alternative routes reflecting different perspectives


Real World Application (Results)

Weighting one stakeholder group over the others derives alternative routes that emphasize their particular concerns

Combining alternative corridors identifies the decision space reflecting various perspectives

…routing decision space


Model Calibration and Weighting

Avoid areas of…

High Housing Density

Far from Roads

In or Near Sensitive Areas

High Visual Exposure

…but what is “high” housing density and how important is it?

Ratings– relative preference among categories within a single map layerWeights– relative preference among map layers


Calibrating Map Layers (Delphi)

Model calibration refers to establishing a consistent scale from 1 (most preferred) to 9 (least preferred) for rating each map layer…

The Delphi Process is used to achieve consensus among group participants. It is a structured method involving iterative use of anonymous questionnaires and controlled feedback with statistical aggregation of group response.

1 for 0 to 5 houses…group consensus is that low housing density is most preferred

Fact Judgment

(See www.innovativegis.com/basis, select Column Supplements, Beyond Mapping, September 03, Delphi)


Delphi Process (Spreadsheet)

…the process is repeated until there is “acceptable” consensus on the calibration ratings

Each participant identifies their cut-off values

1=good to 9= bad (avoid)

Summary statistics are computed and used to stimulate discussion about differences in opinions

Information on each data layer is presented and discussed by the group

…structured method involving iterative use of anonymous questionnaires and controlled feedback


Weighting Map Layers (AHP)

Model weighting establishes the relative importance among map layers (model criteria) on a multiplicative scale…

The Analytical Hierarchy Process (AHP) establishes relative importance among by mathematically summarizing paired comparisons of map layers’ importance.

HD * 10.38

R * 3.23

SA * 1.00

VE * 10.64

…group consensus is that housing density is very important (10.38 times more important than sensitive areas)

(See www.innovativegis.com/basis, select Column Supplements, Beyond Mapping, September 03, AHP)


Calculating the Relative Weights (Expert Systems)

Each participant completes questions comparing the relative importance of the data layers--

“…avoiding locations of high visual exposure is _____ more important than avoiding areas close to sensitive areas”

1=same to 9= extremely more important

Responses are entered into the pairwise comparison matrix and it is solved for the relative weight of each map layer

…statistics for logical consistency and degree of agreement are used to determine consensus

…establishes relative importance among by mathematically summarizing paired comparisons of map layers’ importance


Summary of the Basic Routing Process

A quantitative process for establishing objective and consistent weights is critical in developing a robust and defendable transmission line siting methodology. The Delphi and Analytic Hierarchical Process (AHP) are well-established technologies for leveraging expertise and collective wisdom that assist in establishing siting preferences. Theses advanced procedures are used to logically organize suitability problems and derive a set of consistent ratings and weights by systematically structuring stakeholder group input.

GIS-based approaches for siting electric transmission lines utilize relative ratings and weights in considering factors affecting potential routes. The calibration and weighting of numerous factors, such as housing density, visual exposure and proximity to roads and sensitive areas are established for each grid cell location, and then analyzed for the overall “least cost path” (LPC) …optimal route. In practice, the weight set is altered to identify a set of alternative optimal corridors and routes for consideration.

…the result is a routing procedure that is objective, quantitative, predictable, consistent, and defensible


Presentation Topics






Corridor Analysis Funnel

Overview of Methodology


Macro Corridor Identification

Using Geographic Information Systems (GIS), a high level analysis of the project area is performed to identify Macro Corridors.

Macro Corridors are generated using land use/land cover data from 30 meter satellite imagery and existing statewide GIS datasets.

Macro Corridors are areas of least impact to communities and the environment. These Corridors are used to define the outer boundaries of the project study area.

Identifying Macro Corridor (Project Area Extents)


…composite of several data layers—land cover, roads and existing

transmission lines

Macro Corridor GIS Database


Macro Corridors are used to define the project study area for further data collection, which is site-specific, more detailed, and at a higher resolution.

By focusing data collection on the Macro Corridors time, money, and effort are saved.

Data Collection Area


Presentation Topics






Alternative Corridors are generated within the Macro Corridors.

These Alternative Corridors are modeled using criteria that producea standardized set of alternatives.

Built Environment PerspectiveProtecting people places and cultural resources

Engineering Requirements Perspective Minimizing costs and schedule delays

Natural Environment Perspective Protecting water resources, plants and animals

Simple Average Perspective A composite of the Built, Natural and Engineering Perspective

Alternative Corridor Generation


Alternative Corridor Model Structure

Avoidance Areas

CriteriaLayers

Perspectives


Floodplain (6%)Streams/Wetlands (21%)Public Lands (16%)Land Cover (21%)T&E Species Habitat (36%)

Natural Environment

Wt. AverageNatural

Alternative Corridor Model

Avoided Areas

Routing Criteria: Engineering Natural Built

Overall Preference Surface

CombinedAvoidance Areas

Avoidance Areas

Buildings + BufferSpecial PlacesSensitive AreasPhysical Barriers

Discrete Preference Surface

Can’t go there…

Avoid if possible…

Alternative Corridor Criteria and Weights

Wt. AverageCRITERIA

(1)

(1)

(1)

Wt. AverageBuilt

Built Environment

Proximity Buildings (12%)NRHP Historic (14%)Building Density (37%)Proposed Development (6%)Spannable Waterbodies (4%)Land Use (19%)

Perspectives

Wt. AverageEngineering

Engineering Requirements

Linear Infrastructure (48%)Slope (9%)Intensive Ag (43%)

Layers


AvoidanceAreas

Avoidance Areas

Non – SpannableWater bodies

Church Parcels

State andNational Parks

Airports

Wild and ScenicRivers

CemeteryParcels

City and CountyParks

WildlifeRefuge

Ritual ImportanceSchoolParcels

EPA Superfund

Sites

MilitaryFacilities

Building+ Buffers

DaycareParcels

Mines andQuarries

NRHPHistoric

Sites

NRHPHistoricDistricts

NRHPArchaeology

Sites

NRHPArchaeology

Districts

USFSWilderness

Area


BuiltEnvironment

Eligible NRHPHistoric

Structures

Background

1500’ Buffer

Major PropertyLines

Landlots

Edge of Field

Background

ProposedDevelopment

ProposedDevelopment

Background

Spannable LakesAnd Ponds

SpannableLakes and

Ponds

Background

0 – 300’

Proximity toBuildings

Background

600 – 900’

300 – 600’

900 – 1200’

Land Use

Residential

Non-Residential

Other

Built Environment Perspective

BuildingDensity

4 – 25Buildings/

Acre

0.05 – 0.2Buildings/

Acre

0.2 – 1Buildings/

Acre

0 – 0.05Buildings/

Acre

1 – 4Buildings/

Acre


NaturalEnvironment

Floodplain

100 Year Floodplain

Background

Public Lands

WMA –State Owned

WMA –Non-State

Owned

OtherConservation

Land

Background

USFS

Streams/Wetlands

TroutStreams +

Reg. Buffer

Streams< 5cfs + Reg.

Buffer

Rivers/Streams5cfs + Reg.

Buffer

Non-ForestedWetlands + Reg. Buffer

Non-ForestedCoastal Wetlands

+ Reg. Buffer

Background

ForestedWetlands + Reg.

Buffer

Managed PinePlantations

Land Cover

RowCrops And

Horticulture

DevelopedLand

HardwoodAnd Mixed

Forest

Open Land

Wildlife Habitat

NaturalAreas

Species of ConcernHabitat

Background

Natural Environment Perspective


Engineering

LinearInfrastructure

SlopeIntensive

Agriculture

Background

CenterPivot

Irrigation

Slope 0–15%

Slope 15-30%

Slope > 30%

ParallelExisting T/L

ParallelRoad ROW

Parallel RailroadROW

ParallelInterstate ROW

RoadROW

Scenic HighwayROW

Future GDOTPlans

RebuildExisting T/L

ParallelGas Pipeline

Background

FruitOrchards

PecanOrchards

Engineering Requirements Perspective


Calibrating Criteria: Use Delphi Process

Rate each category of from

1 (best) to 9 (worst)

Weighting Layers: Use Analytical Hierarchy Process

Pairwise Comparison

Calibrating Criteria and Weighting Layers

Layers

Criteria

Delphi Form

AHP Form

Group Interaction


Linear Infrastructure 48.3% Floodplain 6.2% Proximity to Buildings 11.5%Rebuild Existing Transmission Lines 1 Background 1 Background 1

Parallel Existing Transmission Lines 1.4 100 Year Floodplain 9 900-1200 1.8

Parallel Roads ROW 3.6 Streams/Wetlands 20.9% 600-900 2.6

Parallel Gas Pipelines 4.5 Background 1 300-600 4.2

Parallel Railway ROW 5 Streams < 5cfs+ Regulatory Buffer 5.1 0-300 9

Background 5.5Non-forested Non-Coastal Wetlands a+ 30' Buffer 6.1

Eligible NRHP Historic Structures 13.9%

Future GDOT Plans 7.5 Rivers/Streams > 5cfs+ Regulatory Buffer 7.4 Background 1

Parallel Interstates ROW 8.1Non-forested Coastal Wetlands + 30' Buffer 8.4 0 - 1500 9

Road ROW 8.4 Trout Streams (50' Buffer) 8.5 Building Density 37.4%Scenic Highways ROW 9 Forested Wetlands + 30' Buffer 9 0 - 0.05 Buildings/Acre 1

Slope 9.1% Public Lands 16.0% 0.05 - 0.2 Buildings/Acre 3

Slope 0-15% 1 Background 1 0.2 - 1 Buildings/Acre 5

Slope 15-30% 5.5 WMA - Non-State Owned 4.8 1 - 4 Buildings/Acre 7

Slope >30% 9 Other Conservation Land 8.3 4 - 25 Buildings/Acre 9

Intensive Agriculture 42.6% USFS 8 Proposed Development 6.3%Background 1 WMA - State Owned 9 Background 1

Fruit Orchards 5 Land Cover 20.9% Proposed Development 9

Pecan Orchards 9

Open Land (Pastures, Scrub/Shrub, etc…) 1 Spannable Lakes and Ponds 3.8%

Center Pivot Agriculture 9 Managed Pine Plantations 2.2 Background 1

Row Crops and Horticulture 2.2 Spannable Lakes and Ponds 9

Developed Land 6.5 Major Property Lines 8.0%Hardwood/Mixed/Natural ConiferousForests 9 Edge of field 1

Wildlife Habitat 36.0% Landlots 7.9Background 1 Background 9

Species of Concern Habitat 3 Land Use 19.1%Natural Areas 9 Undeveloped 1

Non-Residential 3Residential 9

Engineering Natural Environment Built Environment

Criteria Ratings and Map Weights


Presentation Topics






The Alternative Corridors are the top 3% of the best routes within the Macro Corridors.

Alternative Corridor Generation

…recall the “flooding” technique using the combined Start and End accumulation

surfaces to derive optimal corridors


Additional detailed data is gathered within the Alternative Corridors.

Alternative Route Development


Alternative Route Development

Within each of the Alternative Corridors, the Siting Team develops Alternative Routes.


Developing Alternative Routes

Less Suitable

More Suitable

Standardized Alternative

Routes

Built

Natural

Engineering

Simple


Presentation Topics






Alternative Route Evaluation

Evaluate Alternative Routes using

data summarizing: Built Environment Natural Environment Engineering Requirements

Compare Alternative Routes Select Preferred Route


Alternative Route Analysis

ROUTE A ROUTE B

FARMLAND54%

COMMERCIAL23%

INDUSTRIAL6%

RESIDENTIAL12%

FORESTS21%

FARMLAND30%

RESIDENTIAL29%

COMMERCIAL26%

INSTITUTIONAL5%

INDUSTRIAL10%


Evaluating Alternative Routes


Presentation Topics






Alternative Route Statistics

…the relative merits of top few routes based on the alternative route evaluation information are discussed by the siting team then ranked to identify the best route.


Conclusions and Discussion

In 2002, The Electrical Power Research Institute (EPRI) and Georgia Transmission Corporation (GTC) entered into a Tailored

Collaboration Project to examine and refine GTC’s existing Overhead Electrical Transmission Line Siting Methodology. The

scope of the project was to develop new transmission line siting tools, techniques and procedures for GTC that are objective, quantitative, predictable, consistent, and defensible and to prepare a Overhead

Electrical Transmission Line Siting Methodology Report that explains and documents the process. Among the longer-term goals of this project is exploration of the prospects and opportunities of

standardizing the decision process for overhead electrical transmission line siting for the electrical industry.

Joseph K. BerryUniversity of Denver, Geography

[email protected]

Christy JohnsonGeorgia Transmission Corporation

[email protected]


Further Reference

This PowerPoint is posted at…http://www.innovativegis.com/basis/EPRI_GTC/

Online Papers

GeoWorld magazine feature article on the EPRI_GTC project…http://www.geoplace.com/gw/2004/0404/0404pwr.asp

GeoTec Conference paper on general approach…http://www.innovativegis.com/basis/present/GeoTec04/GIS04_Routing.htm

Online book chapter on Routing and Optimal Paths…http://www.innovativegis.com/basis/MapAnalysis/, Topic 19

White Paper on Delphi for GIS modeling…http://www.innovativegis.com/basis/Supplements/BM_Sep_03/T39_3_DELPHIsupplement.htm

White Paper on AHP for GIS modeling… http://www.innovativegis.com/basis/Supplements/BM_Sep_03/T39_3_AHPsupplement.htm


epri environmental sector meetings optimal routing and corridor analysis for electric transmission...

Documents

decision process

movesmost preferred

corridor analysis

basic routing process

electrical industry

map layerthe delphi

stakeholder group

tailored collaboration