trees and power lines

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Trees and Power Lines:

Minimizing Conicts between Electric Powe

Infrastructure and the Urban Forest

By William Brock Most 1 and Steven Weissman 2

March 10, 2012


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ISSUE BRIEF | March 2012

1. Executive Summary 1

2. Introduction 3

3. Identication of the Problem 4

4. Costs of Conict Between Urban Trees and Power Lines 5

5. Benets of the Urban Forest 6

a. Carbon Sequestration 6

b. Property Value 6

c. Street Safety 6

d. Temperature Moderation and Reduction in Energy Consumption 7

e. Air Quality 7

f. Water Quality, Stormwater, and Erosion 7

g. Electric and Magnetic Field Shielding 7

h. Other General Benets 8

6. History of the Urban Forest in America 9

7. Summary of California Law Affecting Urban Forests 10

a. Basic State Law Provisions 10

b. Power Line Clearances by Utilities 10

c. California Urban Forestry Act of 1978 11d. Urban Forest Protocols 11

e. California Solar Shade Control Acts 11

f. Municipal Tree Ordinances 12

8. The Search for Solutions 13

a. Restating the Problem 13

b. Solution: Revision of Municipal Tree Ordinances 13

c. Solution: Cooperation Between Utilities and Local Governments 14

d. Solution: Tree and Utility Inventories 15e. Solution: Tree Replacement or Preemptive Planting by Utilities and Government 15

f. Solutions: Planning Power Line Placement Around the Urban Forest 16

9. Conclusion 17

Appendix A: Legal Authority for Further Municipal Tree Ordinance Provisions 18

* Much thanks to Eli Weissman for his ideas, time, and guidance.

Table of Contents


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Trees and Power Lines: Minimizing Conicts between Electric Power Infrastructure and the Urban Forest 1

Trees and overhead power lines are not easycompanions in the urban landscape. Cities and theirinhabitants plant trees in order to provide safe andpleasant pedestrian environments, cool the urbanlandscape, improve storm water management, providewildlife habitat, and mitigateclimate change. At the same time,electric utilities spend billionsannually on trimming and (often)removing those same trees toenhance reliability and publicsafety related to electric service.

When trees and power lines sharespace too closely, the result canbe power outages and re. Largetrees planted too close to powerlines inevitably require expensivetrimming or removal. Urbanforests have the potential to beuseful tools in dealing with climatechange mitigation and adaptation,but widespread tree pruning andremoval prevents urban forestsfrom fullling this potential.

In many cities, the vast majority of street trees anda signicant portion of trees on private property arelocated beneath utility lines. Many of those trees requirepruning, and about one in ten of those trees have to betopped. Topping involves removing the trees crown,

damaging it and leaving it open to insect infestationand disease. Such trimming reduces the positivebenets of an urban forest and slows its growth. Theresult is a serious conict between the spatial needsof a valuable urban forest and the needs of the citys

electrical infrastructure.

Conicts between trees andpower lines arise for a number ofreasons, but most fundamentallytrees continue to be plantedunder power lines that will growinto the wires overhead. Thiscontinues despite enormousefforts at public education. Theproblem may be that privateproperty owners do not have anincentive to consider power lineswhen planting new trees. Theydo not bear the costs of pruningor tree removal, which are spreadinstead among all of the utilityselectrical consumers. Existingcity tree ordinances addressmany issues, but rarely dea

with interactions with power lines and when they dothey only cover street trees. The complete absenceof rules guiding planting decisions on private propertyis a substantial gap, considering that trees on privateresidential property comprise nearly half of some majoCalifornia cities urban forests.

1. Executive Summary

Trees and overheadpower lines are not easycompanions in the urban

landscape. Cities and theirinhabitants plant treesin order to provide safeand pleasant pedestrianenvironments, cool the

urban landscape, improve

storm water management,provide wildlife habitat, andmitigate climate change.


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Trees and Power Lines: Minimizing Conicts between Electric Power Infrastructure and the Urban Fores


2

Proposed Solutions

1. RevisionofMunicipalTreeOrdinances

In most of California, there is no law stopping a private property owner from planting a tree of

any type directly under power lines, and almost no law that allows a city or utility to remove newlyplanted, potentially problematic trees. Revising municipal tree ordinances to dene tall-growingtrees planted under powerlines as nuisance trees would allow cities and utilities to replace problemtrees with species more appropriate for the location, and possibly shift the cost of replacement to theperson who caused the problem.

2. CooperationBetweenUtilitiesandLocalGovernments:

Utilities and local governments collaborate only minimally on vegetation management. Cities thathave developed programs to coordinate with utilities have had great success and can be used as amodel.

3. TreeandUtilityInventories

Inventories of trees and utility infrastructure in urban areas could help assess the scope of theproblem and allow for targeting of replanting efforts. Additionally, a more precise quantication ofthe ecosystem service values of urban forests would help local governments and utilities with cost-benet analysis for decisions such as when and where to move power lines underground.

4. TreeReplacementorPreemptivePlantingbyUtilitiesandGovernment

Replacement of potentially problematic trees with more appropriate species pays for itself. A utilitycan recover tree replacement costs in as little as ve years and then produce more than $18,000 inpruning savings per thousand trees per year plus savings from fewer power outages and repairs.

5. PlanningPowerLinePlacementAroundtheUrbanForest

Cities and utilities planning out the location of new transmission lines should take into account theshape of the urban forest, especially when deciding where to place underground power lines.


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Trees and overhead power lines are not easy companionsin the urban landscape. Cities and their inhabitants planttrees in order to provide safe and pleasant pedestrianenvironments, cool the urban landscape, improvestorm water management, provide habitat for birds andsquirrels, and mitigate climate change. At the same time,local electric utilities spend millions on trimming and(often) removing those same trees to enhance reliabilityand public safety related to electric service. When treesand power lines share space, the result can be poweroutages and re. Large trees planted too close to powerlines inevitably require expensive trimming or removal.Urban forests have the potential to be useful tools indealing with climate change mitigation and adaptation,but widespread tree pruning and removal prevents urbanforests from fullling this potential. This paper looks atthe costs of conict between Californias urban forestsand its electrical infrastructure, and possible solutions tomitigate that conict.

California is a particularly good place to look forsolutions to negative interactions between trees andpower lines because of the states focus on addressingclimate change. The last decade in California hasseen increasing attention on climate change issues.In June 2005, Governor Schwarzenegger establishedstate greenhouse gas emissions reduction targets inExecutive Order S-3-05. The Executive Order aims forgreenhouse gas emissions reductions to 2000 levels by2010; 1990 levels by 2020; and 80 percent below 1990levels by 2050. The executive order was followed byAB 32, the California Global Warming Solutions Act of2006, the rst enforceable statewide program to limit

greenhouse gas emissions from all major industries.These were followed by SB 97 in 2007 and SB 375in 2008, which further seek to mitigate the statescontributions to global climate change. Californiarecognized in its Climate Adaptation Strategy that urbanforests can aid in both climate change mitigation andadaptation.3 Urban forests are not merely a sideshowwhen it comes to addressing climate change. Nearlya quarter of the contiguous United States tree canopycover is found in urban forests, which are made up ofmore than 74 billion trees.4

Californias growing urban area encompasses abou5% of its land and 94% of its citizens.5 Those urbanareas are subject to environmental problems aside fromclimate change that can be mitigated by a healthy urbanforest: 36 of its 58 counties received a failing grade forhigh ozone levels under EPA standards and 28% of thestates population live in high threat areas for air pollutionand urban heat.6 Californias cities do not come closeto American Forests recommended average of 25%tree canopy for the dry west.7 Despite the wide rangingbenets of a healthy urban forest, urban forestry is anemerging discipline and is just starting to be recognizedfor its public benets.8 Among other purposes, this papeseeks to create a wider recognition of those benets.

2. Introduction

FIGURE 1 . A San Francisco tree is caught amoelectrical lines of various kinds. Photo by autho


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Trees and Power Lines: Minimizing Conicts between Electric Power Infrastructure and the Urban Fores4

Treesgrowup.Thisisalawofnature.9

Conicts between trees and power lines exist becauseelectricity is conveyed through power lines at highvoltages. High voltage electric current can arc out beyondthe line if grounded by something like a tree, resultingin the possible interruption of service or ignition of re

even without physical contact.10 Power lines come in twobasic types: transmission and distribution. Transmissionlines are large lines on bigger utility poles and towerswith larger insulators between the pole and wire. Theycarry large volumes of power from generation facilitiesto substations in local communities. Distribution linestransmit power down city streets from local substationsto specic buildings. Generally, power lines are thehighest lines on a utility pole and are insulated from thepole.11 Lower down on a utility pole are telephone andcable television lines, which carry just a few volts and willonly cause a problem if direct contact with tree branchesrubs the protective layers off of the wire.12

In some large cities like San Francisco, the vast majorityof street trees and a signicant portion of trees on privateproperty are located beneath utility lines.13 Many of thosetrees require pruning, and about one in ten of thosetrees have to be topped. Topping involves removing thetrees crown, damaging it and leaving it open to insectinfestation and disease.14 Such trimming reduces thepositive benets of an urban forest and slows its growth.The result is a serious conict between the spatial needsof a valuable urban forest and the needs of the cityselectrical infrastructure.

This problem is not new. At the 1947 National ShadeTree Conference H.O. Drennan of the Carolina Power &Light Company said:

This high place of importance given lineclearance will be magnied in the future, sincethe poll also indicated trends toward highervoltages on urban distribution systemsmeaning that the continuity of utility serviceis based on the Arborists ability to providean adequate right-of-way for these wiresand conductors to every user, residential,

commercial, or industrial. This is a realchallenge to the Arborist since every one ofthe other items can be handled by using utilitycrews.15

This problem is also not minor. Despite extensiveefforts to educate about how to choose tree species and

planting sites that minimize conict with power linestall trees continue to be planted below high voltageconductors. In a Phoenix tree inventory, more than 70%of trees counted where planted such that they wouldneed to be removed.16 In Bakerseld, CA, a developerplanted 300 redwood trees directly under power linesand declined to move them when it was pointed outthat they would inevitably have to be pruned back orremoved.17 Furthermore, as climate change causesextreme heat and wind events to increase in frequencypower lines are more likely to contact trees and increasethe frequency of greater power outages and res.18

3. Identication of the Problem

FIGURE 2 . Diagram of Electrical Power Lines.Courtesy ofPG&E.


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One way to assess the scope of the problem is to lookat the costs that are generated when trees and powerlines exist in close proximity. The cost of pruning treesaway from power lines is enormous. For example,Pacic Gas & Electric (PG&E), one of four major utilitiesin California, spends more than $180 million annually

to trim trees.19

PG&Es Vegetation ManagementDepartment patrols and assesses pruning needs ofevery part of its 132,000 miles of line every year.20 Thistask requires more than 350 foresters and more than600 tree crews.21 Furthermore, PG&Es vegetationmanagement budget has grown by about 20% in thelast six years and is nearly triple what it was just morethan a decade ago.22

The vegetation management process requires thepruning or removal of thousands of trees per day,23which has a huge effect on the health of the urbanforest and returns tons of stored carbon back into the

atmosphere.24

Vegetation management also includesthe use of tree growth chemical regulators to slow thegrowth of trees and general herbicides to clear the areasunder power lines and around utility poles.25 Thesechemicals could potentially harm the environment.

Failure to sufciently manage the interface betweentrees and power lines can have devastating results. It

is generally accepted that trees growing into or fallingonto power lines are the single largest cause of electricpower outages.26 The August 2003 blackout in the

American Northeast one of the most widespreadblackouts in history was caused in part by severatransmission lines in Ohio hitting inadequately trimmed

trees and going ofine.27

That blackout resultedin power outages for 50 million consumers and aneconomic impact estimated as high as $10 billionIn addition to electrical outages, power lines close totrees cause res. Power lines are responsible for onlyabout 3% of ignitions in CAL FIRE jurisdiction, but havecaused four of the 20 largest res in California history.28

Fires caused by trees hitting power lines have resultedin settlements in the tens of millions of dollars.29

4. Costs of Conict Between UrbanTrees and Power Lines

FIGURE 3. The Undesirable Method Of Tree PruningAround Power Lines Called Topping. Courtesy of Miller


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In addition to looking at the costs of mismanagement,it is important to look at the value of a healthy urbanforest. According to one estimate, a single streettree returns more than $90,000 of direct benets(not including aesthetic, social and natural) over itslifetime.30 Many of these benets relate to climate

change. Most obviously, carbon sequestration andthe reduction in urban energy consumption contributeto the mitigation of global warming. Other classes ofbenets can aid with adaptation to climate change andthe secondary effects of global warming. Adaptation-related benets include temperature moderation, airquality improvement, and storm water effects,31 as wellas the necessary role urban forests play in allowingtree populations to migrate as local conditions changedue to global warming.32

CarbonSequestration

The most direct process linking trees to climate change

mitigation is carbon sequestration. Global climatechange is caused by high levels of carbon dioxide andother greenhouse gasses in the atmosphere trappingheat from the sun. As trees grow, they absorb carbondioxide (CO

2) and release oxygen (O

2), turning the

carbon into the main substance of their leaves, roots,branches, and trunk. Carbon makes up 45-50% ofthe dry-weight biomass of trees.33 By this process,the growth of trees in an urban forest can reduceatmospheric levels of carbon dioxide and slow theprocess of global heating.

The expansion of urban forests can signicantly aidCalifornia in meeting its climate change mitigationgoals. The California Global Warming Solutions Act of2006 (AB32) requires a reduction in greenhouse gasemissions to 1990 levels by 2020,34 which amountsto a reduction of 173 Mt (million metric tons) per yearfrom the predicted level in 2020.35 Arial photographyof California cities has found 242 million empty treeplanting sites, which if lled with trees would sequester

about 21.78 Mt of carbon dioxide annually.36 This wouldfulll 12.6% of the reductions necessary for the state tomeet its goal.

It is true that carbon dioxide is released through theprocess of tree planting and maintenance throughfuel consumption by vehicles and equipment, butthat release is only 2-5% of the emission reductionsobtained through sequestration and reduced powerplant emissions.37 The carbon sequestration benetsof trees can be lost to decay, mortality, and stress,so it is important to maximize the health of the urbanforest.38

PropertyValue

One U.S. Forest Service estimate suggests that homemarket values are pushed upward by the presence oftrees at rates from 7-20%.39 A similar effect has beenfound in commercial areas, where businesses on treed

streets have been found to have 20% higher incomestreams than those without trees, perhaps becausecool, shady, attractive areas have more of a drawfor customers.40 One study showed that in tree-linedcommercial districts shoppers report more frequentshopping, longer shopping trips, and willingness tospend 12% more for goods.41

StreetSafety

Street trees buffer pedestrians from potentiallyhazardous trafc and provide spatial denition tothe public right-of-way. By creating vertical walls

and a dened edge, trees help motorists guide theirmovement and assess their speed.42 Trees alongstreet curbs have been shown to signicantly affectdrivers perceptions of safety and reduce their drivingspeed.43 Perhaps for these reasons, there are fewerand less severe crashes on streets with streetscapeenhancements.44

5. Benets of the Urban Forest


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TemperatureModerationandReductioninEnergyConsumption

Trees are ideal devices to moderate temperatures incities they cool urban areas when it is hot, and warmthem when it is cold. Cities tend to be warmer thanrural areas by 0.5-1.5 C, requiring extra use of powerintensive air conditioning during summers.45 Trees can

reduce the temperature of urban areas by more than3.5 C.46 Trees cool their environment in several ways.First, they reduce temperatures by intercepting solarradiation (which conveniently occurs only during warmmonths; in the winter, deciduous trees are leaess andallow the sun through). The shade effect of trees caneven lengthen the lifetime of street pavement by 40-60% by reducing the daily expansion and contractionof asphalt, requiring less frequentrepair or resurfacing.47

Additionally, trees cool urbanareas through the process ofevapotranspiration, in which wateris brought up through roots andevaporated off of leaves. Just asthe evaporation of sweat cools thehuman body, evapotranspirationcools a tree and the nearbyenvironment. A single tree cantranspire approximately 88 gallonsof water per day, which providesthe cooling power of ve averageroom air conditioners running 20hours a day.48 Californias 177

million urban trees are estimatedto save 6,400 GWh in annualelectricity use for air conditioning, equivalent to seven100 MW power plants.49 A recent paper estimated thatplanting 100 million trees in residential locations inthe U.S. could save approximately $2 billion dollars inenergy costs per year.50

Trees also warm cities when temperatures are low.Cities primarily cool down by emitting infrared radiationinto the atmosphere at night; trees reduce that heatloss.51 Trees planted in between buildings and coldwinter winds can block the wind and provide insulation

that can help keep the building warm.

The U.S. Forest Service has estimated that well-positioned trees can reduce energy use in conventionalhouses by about 2025% by shading houses insummer and shielding them from wind in winter.52 Thisis particularly important in California, which is likely toexperience signicant energy shortages during futureheat waves.53

AirQuality

California possesses three of the countrys top fourmost polluted cities in the categories of short-termparticulates, long-term particulates, and ozone, plusthe top 11 most polluted counties for ozone.54 Urbanforests can mitigate all these problems.

By reducing urban temperatures tress also reduce theformation of ozone and smog.55 They remove airborneparticles by trapping them and by increasing humidity(which washes particulates out of the air).56 Moreovertrees directly absorb air pollutants like ozone, carbonmonoxide, nitric oxide, and sulfur dioxide.57 Annuallytrees in Sacramento County alone remove about665 tons of ozone and 748 tons of particulate matter

smaller than 10 micrometers.58

Tree cover in urban areas can helpreduce the incidence of respiratorydiseases, which means fewerworkdays lost and a lower burdenon the health care system.59 Treescan even mask unpleasant odorsassociated with city life via directabsorption or by producing moreagreeable foliar or oral scents.60

WaterQuality,Stormwater,andErosion

Urbanization increases theenvironments impermeablesurfaces, creating signicanstorm water management

challenges that the urban forescan ameliorate. Trees absorbthe rst 30% of most precipitation through their leafsystems and up to another 30% of precipitation isabsorbed into the ground and captured by the rootswhich brings it back into the air through transpiration.6

Studies show that tree canopies intercepting rain inSalt Lake City reduce surface water runoff in a 12-hourone-inch rainstorm by about 11.3 million gallons, or17%.62 This stormwater retention capacity is of greatvalue. For example, creating stormwater managemeninfrastructure to replace San Diegos urban forestwould cost an estimated $164 million.63

ElectricandMagneticFieldShielding

Operation of electric power transmission linesintroduces electric and magnetic elds into the urbanenvironment. Electric and magnetic elds underneathoverhead transmission lines may be as high as 12kV/m. The health impacts of electric and magneticelds are not fully understood, but analysis by theNational Academy of Sciences in 1996 suggested that

California possessesthree of the countrys

top four most pollutedcities in the categories ofshort-term particulates,long-term particulates,and ozone, plus the top

11 most polluted countiesfor ozone. Urban forests

can mitigate all theseproblems.


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Recognition that an urban forest is a desirable thing inAmerican cities dates back to the turn of the 19 th century.Prior to that, some cities had no street trees becauseinsurance companies would not insure houses withtrees in front of them.79 Changing values resulted in1807 legislation for the Territory of Michigan requiringtree planting on Detroit squares and boulevards.80Similarly, the commission charged with selecting theMississippi capital in 1821 recommended that the newcapital have every other blocklled with native vegetation or agrove of trees.81 The rst ArborDay was sponsored in 1872 bythe Nebraska Board of Agricultureand involved the planting of morethan a million trees.82 During theearly twentieth century most largecities and many medium sizedcommunities initiated city forestry

programs to plant and care forstreet and park trees. Smallercities and towns engaged intree planting projects, but manydid not establish city forestryprograms until Dutch elm diseaseattacked their tree populations inthe 1950s, 60s, and 70s.83

However, as mass housingbecame the norm beginning in the 1930s, treeswere removed to accommodate construction and notreplaced. This trend didnt begin to reverse until the

late 1960s when home buyers started placing higherpremiums on wooded parcels.84 Federal investment inurban forests began in the early 1970s, with federallyfunded programs in urban forestry at the PinchotInstitute of Environmental Forestry Studies and U.S.Forest Service.85 The Cooperative Forestry Assistance

Act of 197886 authorized the Department of Agriculture

to provide nancial and technical assistance to stateurban foresters, a commitment that was expanded aspart of the 1990 Farm Bill.87 More recently, the 2008Farm Bill tweaked federal involvement in urban forestryby requiring each state to complete Statewide ForesResource Assessment and Strategy that delineatespriority urban forest areas and issues.88 As the resulof state and federal mandates, California performedforest resource assessments in 1979, 1988, 1996

2003, and 2010.89

Currently, tree planting programsacross the country are sponsoredby governments at all levels localstate, and federal. In CaliforniaCAL FIRE provides grants of up to$100,000 for urban tree plantingprojects through its Green Treesfor the Golden State program90 andsmaller grants through the ReLeaUrban Forestry Grant Program.9

CAL FIREs program specicallydeclares ineligible any projecthat will eventually conict withoverhead or underground utilities.92

In Chicago, the Bureau of Forestryplants up to several thousand treesa year along public parkways.93

The program was so successfuthat in 2009 nearly all the available locations had beencovered.94 Even more ambitiously, the ConservationTrees for Nebraska Initiative a program seeking to

plant more than a million trees per year has partnersamong local, state, and federal agencies: local NaturaResource Districts, the Nebraska Forest Service andDepartment of Agriculture, and the federal USDANatural Resources Conservation and Forest Services.95

6. History of the Urban Forest inAmerica

Recognition that an urbanforest is a desirable thingin American cities datesback to the turn of the

19th century. Prior to that,some cities had no streettrees because insurance

companies would notinsure houses with trees in

front of them.


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BasicStateLawProvisions

The California Civil Code outlines the most basicelements of the states tree law, such as dening whoowns a tree96 and how a tree can be bought or sold.97The Civil Code also provides that if an owners treeis wrongfully injured, they are owed three times theactual cost of damage to the tree.98 The penal codeclassies harming anothers tree as a misdemeanor,but exempts trimming for the purpose of protectingor maintaining an electric power line.99 In California,a homeowner has a right to cut back encroachingbranches and roots from a neighbors tree, but as ofa 1994 court ruling that right is no longer absolute: thehomeowner must consider the health of the tree andact reasonably when pruning.100 The legislature hasalso expressed its support generally for aggressivetree planting and methods of pruning that promote thehealth of the trees, requesting that CAL FIRE distribute

information about safe pruning methods.101

PowerLineClearancesbyUtilities

Prior to 1997, utilities were only required to maintaina reasonable clearance between power lines andfoliage. However, large wildres and two majorblackouts caused by vegetation intersecting electricallines caused the California Public Utilities Commission(CPUC) to tighten standards under General Order95. Under Rule 35 of the General Order, utilitiesmust maintain specic minimum clearances of treebranches and vegetation around overhead wires in allareas. Minimum clearances range from 18 inches to15 feet in most situations, depending on the voltageof the power line, exposure to weather, and re riskin the surrounding area.102 Utilities are exemptedfrom meeting clearance requirements if they cannotget permission to access the area around a powerline to trim. Typically utilities require a right to accesspower lines as a condition of service to the consumer,and often they possess an easement for the purposeof maintaining the lines. Consumers have strong

incentives to allow access: utilities do shut off powerif a property owner keeps them out103 and the propertyowner also faces liability for a re if they prevent theutility from clearing a hazard.104 Only 1-3% of propertyowners initially refuse to allow utilities access to trimtrees, and the majority of those refusals are resolved

through negotiation.105

General Order 95 provides a bare minimum clearancefor all areas throughout California for which local reghters are responsible. Areas that are outside cityboundaries fall within the CalFire or U.S. Forest Service

jurisdiction and are more strictly regulated by statelaw and have minimum clearance requirements forhigh voltage lines ranging from 4-10 feet, dependingon voltage.106 Clearance must be sufcient to prevenvegetation from intersecting the power line consideringforeseeable wind velocities, temperatures up to 120degrees Fahrenheit, and character of the vegetation.107

Within city boundaries, municipal tree ordinancescan require additional clearance of power lines, buttypically do not. Utilities are required to keep primaryand secondary power lines clear, but the consumer isresponsible for maintaining service wires the powerlines that bring electricity from a pole to the individuabuilding.108 Failure to make a power line safe fromall exigencies can expose a utility to liability for asubsequent re,109 even if a tree that falls on the powerline stands on private property or is outside of the utilitysright of way.110 As a result, many utilities have internapolicies that require greater minimum clearances than

the General Order, some ranging from 10-25 feet.

11

California regulation of power lines interaction withtrees is substantially stricter than the rest of the nation

as of 2002, the California Public Utility Commissionwas the only utility regulatory body in the U.S. to haveadopted mandatory clearance requirements.112

In addition to line clearance laws, the CaliforniaOccupational Safety and Health Administrationrequires that employees trimming trees near powe

7. Summary of California LawAffecting Urban Forests




lines be qualied and trained properly.113 Further,the Federal Energy Regulatory Commission (FERC)requires utilities to have Transmission VegetationManagement Plans addressing vegetation inspections,clearances, qualications of workers; mitigation plans,and an imminent threat process.114 This standard hasbeen problematic and is currently under revision.

The standard requires that vegetation managementensure system reliability.115 Since only tree removaland not tree trimming can truly ensure that brancheswill never intersect power lines, utilities have beenmore aggressive with their removal activities.116

CaliforniaUrbanForestryActof1978

The Urban Forestry Act of 1978117 guides the state tocreate and maintain sustainable urban forests. Theact is implemented primarily through the CaliforniaDepartment of Forestry and Fire Protections (CALFIRE) Urban and Community

Forestry Program, which aims todevelop a regional and statewidecooperative effort to advancethe development of sustainableurban and community forests.118Under amendments to the Act, adirect link is drawn between urbanforestry projects and the mitigationof climate change.119

Pursuant to the Act, CAL FIREprovides technical assistancefrom seven Urban Forestry FieldSpecialists and gives out grantsof between $2,500 and $500,000for innovative urban forestryor greening projects. Projectsthat can be funded involve treeplanting, tree inventories, urban forest policy andordinance development, education, or any advancesin urban forestry, urban greening, or the managementof urban natural resources.120

Propositions 40 and 84121 provide funding for projectsunder the Act. In the 2009/2010 scal year, CAL FIRE

issued a total of $5,971,453.86 in grants to groupsranging from Adelante High School to the USFSCenter for Urban Forest Research.122 All projectsmust meet certain standards for nursery tree quality,planting procedure, and minimum maintenance, but thestandards do not include any reference to consideringthe location of utility lines when planting.123

UrbanForestProtocols

In 2008, California approved Urban Forest Protocolsdeveloped by the non-prot Climate Action Reserveunder which local governments can account forreport, and verify greenhouse gas emission reductionsassociated with a planned set of tree planting andmaintenance activities.124 The goal of the protocolsis to allow local governments to obtain offset carboncredits for planting trees in urban settings under AB32s cap-and-trade system.125 In February 2010 the

Air Resources Board (CARB) rescinded its previousadoption of the rst version of the Protocols in order totransition to a regulatory offset compliance system inwhich the Protocols will be incorporated by referenceCARBs staff subsequently recommended adoption ofa revised version of the Protocols, but the board hasyet to formally adopt them.126

The Urban Forest Project Protocol does make referenceto negative interactions between

trees and power lines, but onlyspends a few words on the subjectThe Protocol recommends plantingonly small trees under power linesand that planters contact utilitiesfor advice.127

California Solar Shade ControActs

The California Solar Shade ControAct of 1979 was enacted to protectsolar panels from encroachingvegetation that would blockaccess to sunlight.128 It requiredthat no plant may be placedor allowed to grow such that ishades a solar collector, exceptingpreviously existing plants or thei

replacements. The result was that applications toinstall solar panels in residential homes were oftendenied because city street trees would need to betrimmed annually at the citys expense.129

In response to national attention surrounding a casein which two homeowners were criminally prosecuted

under the Act for letting their redwood trees casshade on a neighbors solar panels,130 the Legislatureamended law through the Solar Shade Control Act o2009 (Pub. Res. Code 25981-25985). The 2009

Act exempts trees and replacements of trees thawere planted prior to the solar panel. Trees are alsoexempted that are publically owned, protected byordinance, or required as part of a landscape plan forthe purpose of receiving an entitlement. However, the

The Urban Forest ProjectProtocol does make

reference to negativeinteractions between treesand power lines, but onlyspends a few words on

the subject. The Protocolrecommends planting only

small trees under powerlines and that planterscontact utilities for advice.


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12

2009 Act also increases the potential for legal conictbetween trees and solar panels by expanding thedenition of solar collectors to include panels installedat ground level.

MunicipalTreeOrdinancesApproximately 80% of California cities have municipaltree ordinances.131 There is an enormous diversityamong tree ordinances in California. For example, thetown of Mill Valley declares redwoods to be heritagetrees, giving them legal protection, while nearbySausalito chooses to place a higher value on views,designating the quick growing and tall redwoods asundesirable.132 Some cities regulate all kinds of trees,while others regulate only a single tree (e.g. the cityof Thousand Oaks tree ordinance only applies to oaktrees).133 134 Most cities require that their employees and

contractors follow pruning standards and avoid harmfultopping when trimming trees, but as of 2003 only asmall minority required utility companies or privateindividuals to follow the same standards.135

Tree ordinances cover a variety of topics, includingrequiring tree planting in new development, dealingwith hazardous or nuisance causing trees, protectingdesirable trees, and protecting the urban forest duringdevelopment. In a survey conducted in 2003, most o

the responding city ofcials stated that requiring treeplanting in new residential development is the mosteffective ordinance provision.136 Tree ordinances alsooften regulate pruning by utility companies, requiringthem to observe good arboricultural practices or notifythe city before working on trees.137

Many cities tree ordinances require permits to planttrees on streets or other publicly owned areas. Somecities require clearance from power lines in theirordinances or implementing regulations.138 While somecities require that a planter consider conicts withpower lines when planting street trees, the authors ofthis paper do not know of any cities that have a similarrequirement for planting on private property.

Example: Purposes of the San Francisco Urban Forestry Ordinance

(San Francisco Public Works Code, Article 16, 801)

Optimizing public benets of trees, including climate, abatement of air and noise pollution, reduction

of soil erosion and runoff, enhancement of the visual environment, and promotion of communitypride;

To integrate street planting and maintenance with other urban elements and amenities;

To promote efcient, cost effective management of the Citys urban forest;

To reduce the public hazard, nuisance, and expense occasioned by improper tree selection, planting,and maintenance;

Equitable, sustained, and reliable means of funding urban-forest management;

Enhancing the Citys overall character and sense of place;

Recognizing that trees are an essential part of the Citys aesthetic environment;

Promoting public participation and dialogue about tree removal;

Recognizing that green spaces are vital to San Franciscos quality of life;

Ensuring that landscaping in sidewalk areas maximizes environmental benets, protect public safety,and limit conicts with infrastructure.


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RestatingtheProblem

Conicts between trees and power lines arise for anumber of reasons, but most fundamentally treescontinue to be planted under power lines that willgrow into the wires overhead. This continues despiteenormous efforts at public education. Many utilities

and cities have extensive Right Tree, Right Placeeducation programs that include mass mailing ofinformation to consumers.139 Detailed guidelines existto help consumers make planting decisions,140 includingan extremely impressive and usable online softwarepackage called SelecTree produced by the UrbanForest Ecosystems Institute.141 While these programsmay have helped somewhat, some members of thevegetation management community believe they havebeen largely ineffective,142 and major utilities like PG&Ehave not developed any process for evaluating theireffectiveness.143 The general population has a limited

sense of how hazardous power lines are and howunsafe it is to have trees near high voltage conductors.Perhaps more importantly, few people recognize thedifference between a telephone line and a power line.144

The problem may be that private property owners donot have an incentive to consider power lines whenplanting new trees. They do not bear the costs ofpruning or tree removal, which are spread insteadamong all of the utilitys electrical consumers. Existingcity tree ordinances address many issues, but rarelydeal with interactions with power lines and when theydo, they only cover street trees. The complete absence

of rules guiding planting decisions on private propertyis a substantial gap, considering that trees on privateresidential property comprise nearly half of some majorCalifornia cities urban forests.145 Generally, when citiesthemselves plant trees they are required to considerutility infrastructure when selecting location and treetype. More than ninety percent of the time, however,it is the developer rather than the city or homeownerwho pays for and plants trees in new residentialsubdivisions.146

Documents more inuential than public educationguidelines tend to ignore or gloss over negativeinteractions between trees and power lines. CaliforniasForest and Rangelands 2010 Strategy Report, whiledealing with a number of urban forestry issues, doesnot address conict with utilities.147 The states Urban

Forest Project Protocol does make reference tonegative interactions between trees and power linesbut only spends a few words on it, recommending toplant only small trees under power lines and contacutilities for advice.148 Even model tree ordinances donot handle these issues.149

SOLUTION:RevisionofMunicipalTreeOrdinances

In most of California, there is no law stopping a privateproperty owner from planting a tree of any type directlyunder power lines, despite the eventual consequencesThere is also almost no law that allows a city or utility to

8. The Search for Solutions

FIGURE 4. An Example Of Right Tree, Right Place PuInformaon Material Published By The City Of Riverside


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14

remove newly planted trees when it is cheap to do soin anticipation of a problem. They typically must waituntil the tree is an imminent danger but by that pointit is far more expensive to remove it. However, manycities regulate nuisance trees, and require that theybe trimmed or removed at the owners expense. Onlyone California city was found to have a nuisance treeordinance that explicitlycovers trees that may growinto power lines. The City of Fowlers municipal codeprovides that:

Any tree or shrub growing in a public parkingstrip, public place, or on private property,which tree or shrub is endangering, or whichin any way may endanger, the security orusefulness of any public street, sewer, orsidewalk or the full and safe operation ofpublic utility wires, is hereby declared tobe a public nuisance...andthe City Superintendent maythen remove or trim such treeand assess the costs thereofagainst the property.150

The advantage of this ordinance,if enforced, is that the costs ofdealing with a problematic tree areborne by the person most able toavoid them the property ownerwho is most likely to have plantedthe tree. As one commentersaid, we have laws that forbidpeople from maintaining unsafe

conditions on their property. Weneed legislation that makes itunlawful to maintain or cultivateany tree that is hazardous orwhich may come in contact witha power line and grants authorityfor utilities to remove unsafe trees without fear oflawsuits or reprisals.151 Others have suggestedcharging private property owners if repeated pruning isneeded for a certain tree, thus giving them the choiceof keeping the tree or replacing it with a smaller speciesthat would not require expensive pruning.152

Some cities have tree ordinances that could plausiblybe used to remove trees before they become a problem.The City of Lakewoods code provides that:

[A]ny tree or shrub growing wholly on privateproperty but which, because of its physicalcondition, height, angle or lean, or otherfactor, is endangering or may in any wayendanger the security or usefulness of anypublic street, sewer or sidewalk, or adjoining

private property, ishereby declared to be apublic nuisance.

Since power lines are presumably the private propertyof the utility that operates them, this ordinance mighauthorize the city to remove trees that will grow up tointersect lines.153

Most other cities reviewed with tree nuisance ordinancesdene a nuisance tree in such a way that it could notbe used to deal with power line-tree conicts beforethey become expensive. San Francisco, for examplerequires that the tree pose an imminent hazard toperson or property.154 Other cities require that thenuisance tree endanger the security or usefulness ofa public sewer, street, public right of way, sidewalkor public place.155 If more cities were to model theirnuisance tree ordinances after Fowler and enforce

them, private property ownerswould have a much greaterincentive to not plant trees directlyunder power lines or plant shortetrees that are less likely to causeproblems. This would be of greabenet to the efcient and healthygrowth of the urban forest.156

Greater city involvement in urbanforest management on privateland may have some support. Asone commenter pointed out: treesare large, long-lived organisms inurban areas why wouldnt thecity regulate that?157

There are other related municipaordinance changes that mighachieve similar goals. Cities couldmove citizens towards efcientree planting by requiring a permi

to plant trees on private property, just as planting a streetree requires a permit. While the city could require thathe private property owner demonstrate appropriateplanting plans as a condition for receiving the permita system that sets up procedural roadblocks to treeplanting would likely be detrimental to the urban forest

SOLUTION:CooperationbetweenUtilitiesandLocalGovernments

There is currently minimal direct collaborationbetween utilities vegetation management programsand local governments,158 although such effortsmay be increasing.159 Utility/city direct cooperationtypically occurs only when a problem arises, while itis local nonprots that usual address forward-lookingconcerns.160 The most common form of interaction

Any tree or shrub growingin a public parking strip,

public place, or on privateproperty, which tree or

shrub is endangering, orwhich in any way may

endanger, the security orusefulness of any public

street, sewer, or sidewalkorthe full and safe

operation of public utilitywires, is hereby declaredto be a public nuisance...




involves a local ordinance requiring utilities to obtaina permit to trim within city limits, allowing the city toexercise quality control.161

This regime of minimal cooperation creates signicantinefciencies. For example, often cities patrol theirtrees and cut branches off of the bottom to keep thestreets clear, while utilities separately patrol the sametrees and cut branches off of the top to keep lines clear.PG&E reports that it has attempted to combine theseactivities more than once, without success.162

PG&Es experience does not mean that efforts atcooperation are futile; other cities, notably Chattanooga,have had better results. Chattanooga hired a utilityforester and a vegetation manager, and implemented acooperative plan with the electrical utility that included:combining use of pruning and removal contractors;coordination of activities between the utility and thePublic Works Department such as wood removal; joint

arborist training; and GIS data sharing.

163

Cities could approach improving cooperation bychoosing from a diverse range of actions that include:

A request that the city manager provide areport to the city council on the possible waysto incorporate utility knowledge and improvecooperation.

Joint training programs or temporary staffexchanges.

Periodic meetings between utility and city staff

counterparts.

Requirements that city planning departmentsincorporate utility knowledge into approvalprocesses.164

Allowing contractors and engineers to sitthrough pre-submittal conferences with permitreview teams.165

Direction to the city manager to negotiatesharing of tree crews with utilities.

An ordinance requiring that all tree planting

meets utility right tree, right place guidelines.

SOLUTION:TreeandUtilityInventories

Inventories of trees and utility infrastructure in urbanareas could help address conicts in several ways.First, they could help assess the scope of the problem.For example, while PG&E foresters assess every mileof every line every year to ensure that lines are clear,166

they do not consistently count how many newly plantedtrees are likely to grow into power lines in the future.167

Understanding the scope of the problem mighencourage cities to take action.

Second, a more precise quantication of the ecosystemservice values of urban forests would help locagovernments and utilities with cost-benet analysisfor decisions such as when and where to move powerlines underground. The non-prot American Forestshas pioneered a green data layer accessible througha GIS software product called CITYgreen to help locaelected ofcials make decisions that connect naturewith growth.168

Third, urban forest inventories are often a necessaryprerequisite to a program of planting or of replantingexisting problem trees with smaller replacementsSome cities have carried out large scale inventories fothis purpose in collaboration with electrical utilities.169

Inventories of urban utility infrastructure would alsobe helpful for this purpose. A lack of such data in thepast has prevented models from taking all tree-plantingfactors into account when identifying potential plantingsites.170

Urban forest inventories are typically of two types: eldsurveys and remote sensing. Field studies involveeither staff, volunteers, or consultants (usually costingabout $3-5 per tree) locating trees with GPS andcollecting data. Remote sensing involves assessing theurban forest via imagery from a plane or satellite, andcan provide a more limited set of data at substantially

less cost than eld studies. High resolution infraredimagery can provide information on tree crown size andeven species,171 and can be used to identify potentiaplanting sites.172 The U.S.D.A. Aerial PhotographyField Ofce acquires and distributes high resolutionimagery on a seven-year cycle at no cost. Also, theU.S.G.S. ofce in Sacramento has very high resolutionimagery for many cities and counties in California

Although there is no cost to local governments for useof this imagery, processing and distribution may takemore than a year.

SOLUTION:TreeReplacementorPreemptive

PlantingbyUtilitiesandGovernmentOne solution to the problem of tall trees interacting withpower lines is to remove the trees and replace themwith smaller ones or to preemptively plant small treesbelow power lines when the lines are rst installedCities often use cultivated varieties of trees that havepredictable growth patterns. These cultivars are soldby brand name and are clones of the parent, and sotheir shape and size can be largely known before


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planting.173 Cities and utilities can plant on publicly-owned land or on privately-owned land with the ownersconsent something that is not hard to get when thecity or utility is paying for the planting.

SB 427, a 1999 bill in the California Legislature, soughta solution along these lines, but did not make it into law.

The bill would have given utilities the power to removetrees that might potentially cause conict with powerlines, but required the utility to plant at least three treesfor every inch of diameter of the removed trees.174

SB 427 would have allowed for a utility to recover itscosts from consumers, a provision that was groundedin the idea that tree replacement would lead to a more-than-compensating reduction in long-term pruningcosts and energy efciency from shade trees. Thisproposition holds up in the real world. The reviewof one 2006 replacement program found that a utilitycan recover tree replacement costs in as little as veyears and then produce more than $18,000 in savingsper thousand trees per year from pruning alone, notto mention the savings from fewer power outagesand repairs.175 Tree replacement programs can havelasting benets, as well. In 1960, the Pennsylvaniautility company Penelec planted 3,000 compatibletree species under power lines. A survey 25 years

later found 39% of the trees still present and in goodcondition and none of them had required pruningsince planting!176

Tree replacement and preemptive planning could be away to reduce conicts between power lines and treesand grow the urban forest at the same time. An initia

source of nancial support in California might be theobtained from the $220 million in electrical efciencygrant money funded by AB1890 and disbursed by theCPUC.177

SOLUTION:PlanningPowerLinePlacementaroundtheUrbanForest

Greater undergrounding of electrical power lines isfrequently suggested as a solution to tree-power lineconict.178 Certainly that is the case in some areas, butthere are drawbacks as well. Undergrounding powelines can cost in the millions of dollars per mile179

and can delay restoring power in an outage. Evenif not undergrounded, best management practicesrecommend that planning out the location of newtransmission lines should take into account the shapeof the urban forest.180 This could even include creativeideas like criss-crossing power lines across streets soas to minimize contact with trees.181


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Urban trees are infrastructure. In a time when strategies and solutions are badly needed to address climatechange mitigation and adaptation, the urban forest becomes increasingly valuable. In order to grow capacity fothis important urban infrastructure, all levels of government should look for solutions to minimize conict betweentrees and power lines. These solutions may not always be cheap or politically popular, but the myriad positiveimpacts that trees have on the human existence make action worth the cost.

9. Conclusion


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Several of the solutions suggested in this whitepaper involve instituting or extending municipal treeordinances. Traditionally, tree ordinances that regulatedprivate trees were based on the police power or thecommon law of nuisance and applied only to trees thatposed a risk such as those that were dead or diseased.If the drafter of a tree ordinance seeks to mitigateconict between trees and power lines, he or shemay need to ground the ordinance on legal authoritybeyond traditional sources in order to avoid successfullegal challenge. Some localities, like Fairfax County,Virginia, have based their ordinance on broader stateenvironmental law. Fairfax County adopted an erosionand sediment control ordinance which it used to supportan extensive tree protection program.182

Drafters of tree ordinances must consider four mainlegal issues that can affect tree conservation efforts onprivate property: (1) legislative authority; (2) vagueness;(3) takings; and (4) rational nexus.183

LegislativeAuthority

In addition to the general police power of cities and thelaw of nuisance, California state law allows any cityto adopt ordinances that are necessary to meet localconditions of weather, vegetation, or other re hazards,even if more restrictive than state statute.184 Furthermore,nearly a quarter of California cities are charter cities,which gives them greater authority under the Californiaconstitution to regulate their own municipal affairs.185Charter city status may provide more latitude in passingtree ordinances that are founded on local benets. If

the purpose is for something broader like addressingclimate change, however, it is likely that court would ndthat the ordinance is outside of the sphere of municipalaffairs.186 This does not mean that the city cannot passthe ordinance it just means that the ordinance cannotconict with state law.

Vagueness

In order to survive a constitutional challenge forvagueness, a tree ordinance must be clear enough

such that a person of reasonable intelligence couldunderstand what it means. Courts have historically beensupportive of local governments authority to set andapply environmental regulatory standards. Still, termsshould be dened with as much precision as possible toavoid challenges terms such as minimal disturbanceto the natural topography, protection of the maximumnumber of mature trees, and minimized to the greatestdegree possible under the particular circumstanceshave been struck down for vagueness.187

Takings

The Fifth Amendment of the U.S. Constitution andArt. 1, 19 of the California Constitution prohibit thetaking of private property for public use without justcompensation. Unless tree ordinances deprive theowner of all or virtually all of the property value and leaveno economically viable use, or prevent an investment-backed use, they are unlikely to be struck down.188

However, there may be limits to the constitutionality ofmunicipal tree ordinances that require action by privateproperty owners. The Supreme Court held in 1994that:

[t]he citys goal of...providing for public greenways, [is]laudable, but there are outer limits to how this maybe done. A strong public desire to improve the publiccondition [will not] warrant achieving the desire by ashorter cut than the constitutional way of paying for thechange.189

TheRationalNexusTest

Ordinances that require tree replacement or otherexactions can be challenged on whether the conditionsimposed are reasonably related to the need created bythe regulated partys actions. In order to avoid suchchallenges, on-site or off-site replacement or in-lieu-fee requirements should be linked to the number, typeand size of the trees removed. Any funds should beset aside in an exclusive fund and used in a timelymanner.190

Appendix A: Legal Authority for FurtherMunicipal Tree Ordinance Provisions




1 U.C. Berkeley School of Law 2011, Harvard University, A.B. 2005.

2 U.C. Berkeley Lecturer in Residence and Director of the Energy Program at the Center for Law, Energy & theEnvironment.

3 California Natural Resources Agency, 2009 California Climate Adaptation Strategy,at pp. 24, 115 121. Link.

4 McPherson, Gregory E., Urban Forestry in North America.Renewable Resources Journal, Autumn 2006, at p. 8. Link

5 California Department of Forestry and Fire Protection, Californias Forests and Rangelands: 2010 Assessmentat p161 . Link.

6 Id. at pp. 4, 161. Link.

7 Id. at p. 176. Link.

8 Id. at p. 111. Link.

9 Statement of Robert W. Bell, Pacic Gas & Electric Company, President of the Utility Arborist Association (California)

Quoted in Federal Energy Regulatory Commission, Utility Vegetation Management Final Report.March 2004. LinkThe full paragraph is the following:

Electricity seeks the ground. This is a law of physics. It cant be vetoed or legislated away. Trees grow up. This isa law of nature. You cant negotiate with nature. The only time a tree stops growing is when it is dead and there isusually another tree waiting to take its place. Fortunately, from an electric reliability standpoint, trees are pretty easyto kill. Unfortunately, the vegetation manager at a typical utility company faces many man-made obstacles betweenthe teeth of the chainsaw and the trunk of the tree.

10 U.S.-Canada Power System Outage Task Force, Final Report on the August 14, 2003 Blackout in the United Stateand Canada: Causes and Recommendations.April 2004. At p. 59. Link.

11 Shading Our Cities. Gary Moll & Sara Ebenreck, eds. 1989, American Forestry Association. Pp. 137 - 138.

12 Shading Our Cities. Gary Moll & Sara Ebenreck, eds. 1989, American Forestry Association. Pp. 137 - 138.

13 San Francisco Urban Forestry Council & Department of the Environment, Urban Forest Plan. April 2006. At p. 16Link.

14 Id.

15 Utility Arborist Association Quarterly, 2006 City of Phoenix Right Tree, Right Place.Fall 2006. Link.

16 Id.

17 Interview with Lynn Cullen, Vegetation Mgmt Program Manager, PG&E. December 16, 2010.

18 See U.S.-Canada Power System Outage Task Force, Final Report on the August 14, 2003 Blackout in the UniteStates and Canada: Causes and Recommendations.April 2004. At pp. 61, 107. Link. (hot weather creates a greateelectrical load because of more demand from air conditioners and exacerbates line sag); Mitchell, Joseph W., PoweLines and Catastrophic Wildland Fire in Southern California. Presented at the Fire & Materials Conference, San

Francisco CA, Jan 26, 2009. Link. (probability of ignition from power lines increases during high wind events.)19 See Los Angeles Times, PG&E phone, mail tactics are illegal, regulators warn. May 4, 2010.

20 Pacic Gas & Electric Website, Tree-Pruning FAQs. Last visited March 26, 2011. http://www.pge.com/myhome/customerservice/other/treetrimming/faq/

21 Pacic Gas & Electric, Job Description for Senior Program Manager, Vegetation Management Department. Link.

22 Pacic Gas & Electric Press Release, PG&Es Vegetation Management Practices Clear The Way For Power RestorationDuring Storms. December 2, 2005. Link; Pacic Gas & Electric Co. v. Superior Court,95 Cal.App.4th 1389 (2002).

23 Id.

Endnotes


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20

24 Nowak, David J.; Stevens, Jack C.; Sisinni, Susan M.; Luley, Christopher J. 2002. Effects of urban tree managemenand species selection on atmospheric carbon dioxide. Journal of Arboriculture. 28(3): 113-122. Link.

25 Shading Our Cities. Gary Moll & Sara Ebenreck, eds. 1989, American Forestry Association. P. 140.

26 Federal Energy Regulatory Commission,Utility Vegetation Management Final Report.March 2004. Link. (commissionedto support the investigation of the 2003 Northeast blackout.)

27 U.S.-Canada Power System Outage Task Force, Final Report on the August 14, 2003 Blackout in the United State

and Canada: Causes and Recommendations.April 2004. At pp. 19, 27, 30, 58. Link.

28 Mitchell, Joseph W., Power Lines and Catastrophic Wildland Fire in Southern California. Presented at the Fire &Materials Conference, San Francisco CA, Jan 26, 2009. Link.

29 Pacic Gas & Electric Co. v. Superior Court, 95 Cal.App.4th 1389 (2002) (re liability settlement required that $28.7million be spent on public safety programs, tree replacement, contribution to the state general fund, etc.).

30 Burden, Dan. Factsheet: 22 Benets of Urban Street Trees. November, 2008. The Walkable and Livable CommunitiesInstitute, Inc. Link.

31 California Natural Resources Agency, 2009 California Climate Adaptation Strategy,at p. 115. Link.

32 Woodall, C.J.; Nowak, D.J.; Liknes, G.C.; Westfall, J.A. 2010. Assessing the potential for urban trees to facilitatforest tree migration in the eastern United States. Forest Ecology and Managment. 259: 1447-1454. Link.

33 Nowak, David J.,Atmospheric Carbon Reduction by Urban Trees.Journal of Environmental Management (1993) 37,207 217. Link.

34 Health & Safety Code 38550.

35 McPherson, E.G.; Simpson, J.R.; Peper, P.J.; Aguaron, E. 2008. Urban Forestry and Climate Change. Albany, CAUSDA Forest Service, Pacic Southwest Research Station. Link.

36 Id.

37 Id.

38 Climate Action Reserve, Urban Forest Project Protocol. Version 1.1, March 10, 2010. Link.

39 Shading Our Cities. Gary Moll & Sara Ebenreck, eds. 1989, American Forestry Association. P. 49; compare withAnderson, L. M.; Cordell, H. K., Residential Property Values Improved by Landscaping with Trees.Southern Journa

of Applied Forestry, Volume 9, Number 3, 1 August 1985 , pp. 162-166(5) (nding that a 3 to 5% increase in the salesprices of-single-family houses in Athens, Georgia, was associated with the presence of trees in their landscaping).

40 Nichols, Sandra S., Urban Tree Conservation: a White Paper on Local Ordinance Approaches, at p. 16. MontgomeryTree Committee, September 2007. Link.

41 Wolf, Kathleen L., Business District Streetscapes, Trees, and Consumer Response. Journal of Forestry, Volume103, Number 8, December 2005 , pp. 396-400(5).

42 Dumbaugh, Eric. Safe Streets, Livable Streets. Journal of the American Planning Association, Vol. 71, No. 3, Summe2005.

43 Jody Naderi, Byoung Suk Kweon, and Praveen Maghelal. The Street Tree Effect and Driver Safety. Institute ofTransportation Engineers Jounral, February 2008. Link.

44 Id.

45 Grey, Gene W. and Deneke, Frederick J. Urban Forestry. John Wiley & Sons, Inc. 1978. P. 45.

46 Nichols, Sandra S., Urban Tree Conservation: a White Paper on Local Ordinance Approaches, at p. 14. MontgomeryTree Committee, September 2007. Link. citing Planning Advisory Service Report Number 446: Tree ConservationOrdinances, Christopher J. Duerksen with Suzanne Richman (American Planning Association & Scenic America1993), 12.






49 McPherson, Gregory E., Urban Forestry in North America.Renewable Resources Journal, Autumn 2006, at p. 9. Link

50 Braverman, Irus, Everybody Loves Trees: Policing American Cities Through Street Trees. 19 Duke Envtl. L. & PolyF. 81, 84 (2008).


52 Shading Our Cities. Gary Moll & Sara Ebenreck, eds. 1989, American Forestry Association. P. 50.53 California Department of Forestry and Fire Protection, Californias Forests and Rangelands: 2010 Assessmentat

p.166. Link.

54 American Lung Association. State of the Air, 2010. Pp. 11 - 16. Link.

55 California Department of Forestry and Fire Protection, Californias Forests and Rangelands: 2010 Assessmentatp.165. Link.



58 California Department of Forestry and Fire Protection, Californias Forests and Rangelands: 2010 Assessmentat p

165. Link.59 Nichols, Sandra S., Urban Tree Conservation: a White Paper on Local Ordinance Approaches, at p. 13. Montgomery

Tree Committee, September 2007. Link.

60 Grey, Gene W. and Deneke, Frederick J. Urban Forestry. John Wiley & Sons, Inc. 1978. Pp. 61, 79.



63 American Forests, Urban Ecosystem Analysis: San Diego, California. July 2003. At p. 3. Link.

64 World Health Organization Fact Sheet No. 205, November 1998. Link.

65 Assessment of health effects from exposure to power-line frequency electric and magnetic elds.Portier CJ andWolfe MS (eds) NIEHS Working Group Report, National Institute of Environmental Health Sciences of the NationalInstitute of Health, p 523.

66 Health Effects from Exposure to Power-Line Frequency Electric and Magnetic Fields, National Institute of EnvironmentaHealth Sciences of the National Institute of Health. NIH Publication No. 99-4493, May 4, 1999. Link.

67 World Health Organization, About electromagnetic elds. Last visited March 2, 2011. http://www.who.int/peh-emf/about/WhatisEMF/en/; see also, Electric Power High-Voltage Transmission Lines: Design Options, Costand Electric and Magnetic Field Levels, Stoeffel et al., Environmental Assessment Division, Argonne NationaLaboratory. November 1994. Link.

68 Shading Our Cities. Gary Moll & Sara Ebenreck, eds. 1989, American Forestry Association. Pp.. 5, 54.

69 Id. at p. 54.


71 Nichols, Sandra S., Urban Tree Conservation: a White Paper on Local Ordinance Approaches, at p. 15. MontgomeryTree Committee, September 2007. Link. citing Environmental Law Institute, Lasting Landscapes: Reections on theRole of Conservation Science in Land Use Planning, (ELI, 2007)

72 Sullivan, W.C.; Kuo, F.E. Do trees Strengthen Urban Communities, Reduce Domestic Violence?USDA Forest ServiceReport R8-FR 56, January 1996.



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75 Comparing tree-shrub-grass combinations with hard surfaces. Id. at p. 72.

76 Comparing tree-shrub-grass combinations with hard surfaces. Id. at p. 72.





81 Id.

82 Id. at p. 34.

83 Miller, Robert W. Urban Forestry: Planning and Managing Urban Greenspaces. 2nd Ed., Prentice Hall 1997. P 51.



86 16 U.S.C. 2101-2111.87 16 U.S.C. 2103a

88 Pub.L. 110-234, 122 Stat. 923, enacted May 22, 2008.


90 CALFIRE, Urban Forestry & Urban Greening: Green Trees For The Golden State Grant Program 2010/2011 Requefor Proposals. At 2. Link.

91 California ReLeaf, Guidelines & Application, California ReLeaf 2011 Urban Forestry Grant Program.Link.

92 CALFIRE, Urban Forestry & Urban Greening: Green Trees For The Golden State Grant Program 2010/2011 Requefor Proposals. At 3. Link.

93 Irus Braverman, Everybody Loves Trees: Policing American Cities Through Street Trees, 19 Duke Envtl. L. & PolyF. 81, 85 (2008).

94 Illinois Institute of Technologys Institute of Design, Chicagos Urban Forest: Research and Opportunity IdenticationLink. At 13

95 High Plains/Midwest Ag Journal, 10 Different Tree Planting Programs Offer Financial Help.January 8, 2009. Link.

96 California Civil Code 660, 833, 834.

97 California Civil Code 1220.

98 Civil Code 3346.

99 Penal Code 384a.

100 Booksa v. Patel, 24 Cal.App.4th 1786. (Cal. Ct. App. 1994).

101 Government Code 536067.

102 California Public Utilities Commission, General Order 95, Rules for Overhead Electric Line Construction. Revised mostrecently August 20, 2009 in CPUC Decision No. 09-08-029. Link. Some woody stems that meet certain requirements(e.g. tree is hard to climb and not sprouting) are exempt from the 18 inch minimum clearance.

103 Interview with John Melvin, State Urban Forester at CAL FIRE. January 10, 2011.

104 California Department of Forestry and Fire Protection, Factsheet: Trees & Powerlines.Link.




105 Federal Energy Regulatory Commission, Utility Vegetation Management Final Report.March 2004. At p. 18. Link.

106 Pub. Res. Code 4293.

107 14 CCR 1256.

108 Urban Forest Ecosystems Institute, SelecTree Website, Overhead Utility Services. Last visited, March 25, 2011http://selectree.calpoly.edu/utilityTree_cust_equip.html

109 Scally v. Pacic Gas & Electric Co., 23 Cal.App.3d 806, 815 (Cal. Ct. App. 1972).110 Beresford v. Pacic Gas & Elec. Co., 45 Cal. 2d 738 (1955); Irelan-Yuba Gold Quartz Mining Co. v. Pacic Gas &

Electric Co., 18 Cal. 2d 557 (1941).

111 PG&Es Electric Transmission Guideline, Vegetation Management Policy. Effective March 1, 1999. Link.

112 Federal Energy Regulatory Commission, Utility Vegetation Management Final Report.March 2004. At p. 10. Link.

113 8 Cal. Code Regs. 37 - 38

114 North American Electric Reliability Corporation, FAC-003-1: Transmission Vegetation Management Standard. Link.

115 North American Electric Reliability Corporation, FAC-003-1: Transmission Vegetation Management Standard. At R2Link.

116 Interview with Barbara Clement, Vegetation Management Program, PG&E. January 5, 2010.

117 Pub. Res. Code 4799.06 - 4799.12.

118 State of California Department of Forestry and Fire Protection, Urban Forestry Program website. http://www.re.ca.gov/resource_mgt/resource_mgt_urbanforestry.php, last visited March 22, 2011.

119 Pub. Res. Code 4799.12 (j) (Authorized assistance may include, but is not limited to, any of the following needs: . . Funding and other assistance for demonstration projects in urban forestry with special attention given to projects orprograms assisting the state in meeting the requirements of the Global Warming Solutions Act of 2006 [AB 32].)

120 State of California Department of Forestry and Fire Protection, Urban Forestry Program. Urban Forestry & UrbanGreening: Leading Edge Projects Grant Program 2010/2011 Request for Proposals.Link. (grants for projects $30,000to $500,000); State of California Department of Forestry and Fire Protection, Urban Forestry Program. Forestry &Urban Greening: Leang Out Grant Program 2010/2011 Request for Proposals.Link. (grants for projects $2,500 to$30,000.)

121 The California Clean Water, Clean Air, Safe Neighborhood Parks,and Coastal Protection Act of 2002 (Proposition 40)Pub. Res. Code 5096.610; the Safe Drinking Water, Water Quality and Supply, Flood Control, River and CoastalProtection Bond Act of 2006 (Proposition 84), Pub. Res. Code 75001 et seq.

122 State of California Department of Forestry and Fire Protection, Urban Forestry Program. Urban Forestry Program2009/2010 Fiscal Year Grant Awards. Link.

123 State of California Department of Forestry and Fire Protection, Urban Forestry Program. Tree Standards &Specications, available athttp://www.ufei.org/Standards&Specs.

124 Climate Action Reserve, Urban Forest Project Protocol. Version 1.1, March 10, 2010. At p. 2. Link.


126 California Air Resources Board, Proposed Regulation to Implement the California Cap-and-Trade Program, Part VStaff Report and Compliance Offset Protocol.October 28, 2010. At pp. 1-2. Link.


128 Pub. Res. Code 25980 25986.

129 Dockter, Dave. Integration of the California Solar Act with Urban Forestry.Presentation at the Western Street TreeManagement Symposium, January 14, 2010. Link.

130 Vargas v. Superior Court, No. H033570,2010 WL 1896459 (Cal. App. 6th 2010).


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131 Thompson, Richard P. The State of Urban and Community Forestry in California. California Department of Forestryand Fire Protection, Urban & Community Forestry Program Technical Report No. 13. July 2006. At p. 32. Link.

132 Stephenson, Correy E., Tree Law: More Complicated and Plentiful Than Many Lawyers ThinkLawyers Weekly USA, November 22, 2004. Link.




136 Id. at p. 32.

137 See, e.g., San Luis Obispo, CA: Municipal Code Section 12.24.140; Corte Madera, CA: City Code Section 15.50.040

138 San Francisco Regulations Implementing Ordinance No. 165-95 (requiring private property owners to maintain treebranches to allow to allow at least three feet of clearance from wires).

139 See, e.g., City of Riverside, http://www.riversideca.gov/utilities/elec-treetrimprogram.asp; PG&E, http://www.pge.com/myhome/edusafety/diggingyard/planttrees/.

140 See, e.g., McPherson et al., Tree Guidelines for Coastal Southern California Communities.Western Center for UrbanForest Research and Education. January 2000. Link.

141 Urban Foest Ecosystems Institute, SelecTree Website. http://selectree.calpoly.edu/utilityTree_zones.lasso . Lastvisited March 26, 2011.

142 Statement of Randall H. Miller, System Forester, PaciCorp. Quoted in Federal Energy Regulatory Commission,Utility Vegetation Management Final Report.March 2004. At p. 121. Link.

143 Interview with Lynn Cullen, Vegetation Mgmt Program Manager, PG&E. December 16, 2010.

144 Id.

145 Nowak, David J., Compensatory Value of an Urban Forest: an Application of the Tree-Value Formula.Journal ofArboriculture 19(3): May 1993. Link.


147 California Department of Forestry and Fire Protection, Californias Forests and Rangelands: 2010 Strategy ReporLink


149 See, e.g., International Society of Arboriculture, Guidelines for Developing and Evaluating Tree Ordinances.October31, 2001. Link; Iowa State University Extension Service, Sample Tree Ordinance. Link.

150 City of Fowler, Municipal Code 7-1.08. Link. (emphasis added).

151 Statement of Brian Fisher, Strategic Coordinator, BC Hydro and Power Authority. Quoted in Federal Energy RegulatoryCommission, Utility Vegetation Management Final Report.March 2004. Link.


153 City of Lakewood, Municipal Code 4325.1.

154 San Francisco Municipal Code, Art. 16, 802 (o).

155 E.g., City of Hayward, Municipal Code 7-2.60; City of St. Helena, Municipal Code 17.9; City of La Habra, MunicipaCode 12.20.100A.

156 Other commenters have echoed this suggestion. Interview with Lynn Cullen, Vegetation Management ProgramManager, PG&E. December 16, 2010.





158 Interview with Lynn Cullen, Vegetation Management Program Manager, PG&E. December 16, 2010.


160 Interview with Lynn Cullen.

161 Interview with John Melvin.


163 Hyde, Gene,A Case Study in Urban Forestry and Electric Power Board Collaboration.Link.


165 Hyde, Gene,A Case Study in Urban Forestry and Electric Power Board Collaboration.Link.

166 Pacic Gas & Electric Website, Tree-Pruning FAQs. Last visited March 26, 2011. www.pge.com/myhome/customerservice/other/treetrimming/faq/

167 Interview with Lynn Cullen, Vegetation Management Program Manager, PG&E. December 16, 2010.

168 American Forests, Urban Ecosystem Analysis, San Diego, California: Calculating the Value of Nature.July 2003Link.

169 Utility Arborist Association Quarterly, 2006 City of Phoenix Right Tree, Right Place.Fall 2006. Link.170 Wu, C.; Xiao, Q.; McPhereson, E.G.; A Method for Locating Potential Tree-Planting Sites in Urban Areas: A Cas

Study of Los Angeles, USA. Urban Forestry & Urban Greening 7 (2008) 65 -76, at p. 68. Link.

171 Xiao, Q., S.L. Ustin, and E.G. McPherson, Using AVIRIS data and multiple-masking techniques to map urban forestrees species. International Journal of Remote Sensing 25(24): 5637-5654. 2004. Link.

172 Wu, C.; Xiao, Q.; McPhereson, E.G.; A Method for Locating Potential Tree-Planting Sites in Urban Areas: A CasStudy of Los Angeles, USA. Urban Forestry & Urban Greening 7 (2008) 65 -76. Link.

173 Shading Our Cities. Gary Moll & Sara Ebenreck, eds. 1989, American Forestry Association. Pp. 139.

174 SB 427 (Peace). Introduced February 16, 1999; amended in Senate, April 7, 1999. Link.

175 Utility Arborist Association Quarterly, 2006 City of Phoenix Right Tree, Right Place.Fall 2006. Link.

176 Miller, Robert W. Urban Forestry: Planning and Managing Urban Greenspaces. 2nd Ed., Prentice Hall 1997. Pp 389- 390.

177 CPUC Website, Energy Efciency Program Funding. Last visited March 28, 2011. www.cpuc.ca.gov/PUC/energyEnergy+Efciency/EE+General+Info/ee_funding.htm

178 E.g., interview with John Melvin, State Urban Forester at CAL FIRE. January 10, 2011; interview with Lynn Cullen,Vegetation Mgmt Program Manager, PG&E. December 16, 2010.

179 Commonwealth Associates, Feasibility of Undergrounding a Portion of the Miguel-Mission 230 kV #2 TransmissioLine Project Proposed by San Diego Gas & Electric Company.February 26, 2004. Link.

180 U.S.-Canada Power System Outage Task Force, Final Report on the August 14, 2003 Blackout in the United Stateand Canada: Causes and Recommendations.April 2004. At pp. 71, 72 Link.

181 Interview with John Melvin, State Urban Forester at CAL FIRE. January 10, 2011.182 Shea, Ruthmarie, Whose Tree is it Anyway? A Case of First Impression.77 U. Det. Mercy L. Rev. 579, 580 (2000).


184 Pub. Res. Code 4117.

185 Cal. Const. art. XI, 3(a).


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186 CEEED v. California Coastal Zone Conservation Com.,43 Cal.App.3d 306 (Cal. Ct. App. 4th 1974) (Although planningand zoning in the conventional sense have traditionally been deemed municipal affairs, where the ecological andenvironmental impact of land use affect the people of the entire state, they can no longer remain matters of purely localconcern).

187 Nichols, Sandra S., Urban Tree Conservation: a White Paper on Local Ordinance Approaches, at pp. 8 - 9. MontgomeryTree Committee, September 2007. Link.

188 See Lucas v. South Carolina Coastal Council, 505 U.S. 1003 (1992)

189 Dolan v. City of Tigard, 512 U.S. 374, 395 (1994).

190 Nichols, Sandra S., Urban Tree Conservation: a White Paper on Local Ordinance Approaches, at p 10. MontgomeryTree Committee, September 2007. Link.