Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

Report on Transmission Facility Outages 

during the Northeast Snowstorm of October 

29–30, 2011 

Causes and Recommendations 

Prepared by the Staffs of the

Federal Energy Regulatory Commission and the North American Electric Reliability Corporation

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

TABLE OF CONTENTS:

I. Introduction ................................................................................................................... 5

II. Executive Summary ........................................................................................................ 8

III. The October 29–30, 2011 Nor’easter ............................................................................ 11

A. Forecasts and Utility Preparations ...................................................................... 11

B. Storm Produces Record Amounts of October Snowfall ...................................... 13

C. Leafy Trees and Prior Rainfall Compound the Impact of the Snowstorm........... 15

IV. Significant and Widespread Damage to Electric Delivery Infrastructure ........................ 17

A. Distribution Facility Damage and Customer Impact ........................................... 17

B. Transmission Facility Damage and Customer Impact ......................................... 19

1. Transmission Outages ........................................................................... 19 

2. Affected States and Utilities ................................................................... 22 

3. Transmission Facility Outages Had Relatively Limited Impacts on Customers and

Were Restored Quickly.......................................................................... 24 

V. Causes of Transmission Facility Outages ....................................................................... 28

A. Tree Contact ........................................................................................................ 29

B. Transmission Structure Failures .......................................................................... 33

C. Other, or Unknown, Causes ................................................................................ 34

VI. Transmission Outages Did Not Destabilize the BPS or Regional Systems ....................... 35

A. Bulk Power System Impacts ................................................................................ 35

B. Regional System Impacts..................................................................................... 36

VII. Applicability of the Transmission Vegetation Management Reliability Standard ........... 38

A. Overview of Reliability Standard FAC‐003‐1 ....................................................... 38

B. FAC‐003‐1’s Scope............................................................................................... 40

VIII.Outage Reporting Provides Limited Information........................................................... 44

IX. Recommendations........................................................................................................ 46

1. Where Appropriate, Utilities Should Take Targeted Steps to Address Off‐Right‐

of‐Way Danger Trees........................................................................................... 46

2. Utilities Should Employ Recognized Best Practices in Managing Rights‐of‐Way

Where Feasible.................................................................................................... 47

3. Utilities Should Lay the Foundation for Effective Vegetation Management When

Establishing New Rights‐of‐Way ......................................................................... 49

4. Utilities Should Evaluate and, As Needed, Enhance Their Storm Preparedness

and Response Plans............................................................................................. 50

5. Utilities Should Report All Vegetation‐Caused BES Facility Outages to NERC .... 50

6. Disturbance Reports Should Be Clear and Complete.......................................... 51

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

TABLE OF FIGURES:

Figure 1: Snowfall Totals Across the Northeast on October 30, 2011.................................... 14

Figure 2: Leaf Drop Reports, October 2010 vs. October 2011................................................ 15

Figure 3: Snowfall Amounts and Customers That Lost Power................................................ 18

Figure 4: Transmission Line Outages by Voltage Level........................................................... 20

Figure 5: Total Outages: BPS vs. Non‐BPS Elements............................................................... 21

Figure 6: Transmission Line Outages by State and Voltage Level........................................... 22

Figure 7: ISO‐NE Transmission Line Outages During the October Snowstorm....................... 23

Figure 8: Line Outages by Company and Voltage Level.......................................................... 24

Figure 9: Timeline of Customers Affected by a Transmission Station Outage ....................... 25

Figure 10: Duration of Transmission Line Outages................................................................. 26

Figure 11: Line Outages by Cause Category and Voltage Level .............................................. 28

Figure 12: Fallen Trees Located on Rights‐of‐Way and Off‐Rights‐of‐Way ............................ 30

Figure 13: Trees Fallen on 115kV Line in Connecticut............................................................ 31

Figure 14: Tall Tree Fallen on an 115kV line in Massachusetts .............................................. 32

Figure 15: Structure Failure on a 345kV Line in Connecticut.................................................. 33

Figure 16: Wire Zone‐Border Zone Illustration....................................................................... 43

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

 

I. Introduction

On October 29-30, 2011, an unprecedented fall snowstorm hit the Northeastern 

United States, blanketing the region with up to two and a half feet of heavy, wet snow. 

Snowfall amounts broke all previous October records throughout the Mid-Atlantic and 

New England regions. The snowfall totals were most significant in New England, but 

parts of New York, New Jersey, and Pennsylvania also received well over a foot of snow. 

On the morning of October 30, near the end of the storm, more than 3.2 million homes 

and businesses were without power.1 Thousands were without power for more than a 

week, some for as long as eleven days. Estimates put storm costs between approximately 

$1 billion and $3 billion. 

Although the vast majority of these customer outages were caused by damage to 

electric distribution lines,2 seventy-four transmission lines3

 and forty-four transmission 

substations4

 also experienced outages of ten minutes or more. Twenty-four of the 

transmission facilities (twenty-three lines and one substation) that experienced outages 

are Bulk-Power System (BPS) elements.5

 

1

Over the course of the weekend, more than 4.3 million customers lost power at one point or another.  U.S.

DEPARTMENT OF ENERGY, ENERGY ASSURANCE DAILY 1 (Oct. 31, 2011),

http://www.oe.netl.doe.gov/docs/eads/ead103111b.pdf (showing the non‐concurrent, peak reported outages of

twenty‐two utilities).

2 Distribution lines, which carry power from the interstate transmission system to retail customers, are typically

operated under 100 kilovolts (kV) and are generally regulated by the states.

3 Transmission lines, which carry power from electric generating facilities to substations connected to the

distribution system, are typically operated over 100 kV and generally – but not universally – regulated by the

Federal Energy Regulatory Commission (FERC or the Commission) as to rates and terms of transmission service.  

See Federal Power Act § 201(b)(1), 16 U.S.C. § 824(b)(1).  As explained in footnote 5, the Commission also has

jurisdiction, pursuant to Section 215 of the Federal Power Act, over the reliability of the bulk‐power system.  

Although some facilities operated under 100 kV are considered to be “transmission facilities” in certain contexts,

this report uses that term to refer only to facilities operated at or above 100 kV.

4

A transmission substation is connected to one or more transmission lines and houses transformers used to step

up or step down (increase or decrease) electric energy voltages.  Substations also contain, among other

equipment, breakers that allow lines to be connected or isolated in order to clear faults or perform maintenance.  

Transmission substations impacted by the storm are discussed further in Section IV.B.   

5 Section 215(a)(1) of the Federal Power Act defines the bulk‐power System as “(A) facilities and control systems

necessary for operating an interconnected electric energy transmission network (or any portion thereof); and (B)

electric energy from generation facilities needed to maintain transmission system reliability.  The term does not

include facilities used in the local distribution of electric energy.”  16 U.S.C. § 824o(a)(1).  With respect to electric

reliability, the Commission has jurisdiction over all users, owners, and operators of the BPS.  FERC approves

mandatory and enforceable Reliability Standards that are developed by the Electric Reliability Organization (ERO),

the North American Electric Reliability Corporation (NERC), that apply to those BPS users, owners and operators

registered by NERC.  The Commission has adopted, at least for an initial period, NERC’s definition of the term Bulk

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

 

In light of, among other things, the scope and seriousness of the October 

snowstorm event, the number of customers and states impacted, the duration of some of 

the outages, the storm’s impact on entities subject to the Commission’s jurisdiction, and 

the level of interest of the public and elected officials in the event, the Commission 

initiated an inquiry in November 2011 focused on the transmission- and BPS-related 

impacts of the storm. NERC also began an inquiry into the storm’s effect on the BPS, 

and FERC and NERC combined their efforts into one joint inquiry. NPCC, which had 

been assisting NERC in its assessment of the storm event, also joined the inquiry team. 

From the outset, this joint inquiry focused on determining the causes of the 

transmission facility outages and on the steps utilities could take to improve their 

performance in maintaining grid reliability during the next large snowstorm or similar 

weather event. The purpose of the inquiry has not been to investigate whether particular 

companies violated the Reliability Standards or other applicable statutes and 

regulations. NPCC, NERC, and FERC will follow their regular processes in identifying 

and pursuing any potential Reliability Standards violations. Nor has the purpose of this 

inquiry been to propose new or revised Reliability Standards or other regulations. 

During the course of the inquiry, FERC, NERC, and NPCC staff obtained a 

significant amount of data from a variety of affected entities. Staff issued a first set of 

seven multi-part data requests to the thirty-six NERC-registered Transmission Owners 

and Transmission Operators6

 in the NPCC region, and sent a set of twenty-one multipart data requests to those entities that reported experiencing transmission facility 

outages during the event. Staff conducted numerous follow-up calls and requested 

additional information from a number of entities. Staff also interviewed representatives 

of Northeast Utilities, the parent company of the three utilities that experienced the most 

Electric System (BES) for application of the Reliability Standards.  The current definition of the BES is: “as defined

by the [Regional Entity,] the electrical generation resources, transmission lines, interconnections with

neighboring systems, and associated equipment, generally operated at voltages of 100 kV or higher.  Radial

transmission facilities serving only load with one transmission source are generally not included in this

definition.” Mandatory Reliability Standards for the Bulk‐Power System, Order No. 693, FERC Stats. & Regs. ¶

31,242, at P 75, order on reh’g, Order No. 693‐A, 120 FERC ¶ 61,053 (2007).  The Northeast Power Coordinating

Council (NPCC), the NERC‐certified Regional Entity for the states affected by the October snowstorm, uses a

performance‐based test (rather than a voltage‐based bright line) to determine which facilities in its region are

subject to the Reliability Standards, and calls those facilities “Bulk Power System elements.” See NPCC DOCUMENT

A‐10, CLASSIFICATION OF BULK POWER SYSTEM ELEMENTS (2007).  Because the transmission facility outages caused by the

October snowstorm occurred only in the NPCC region, this report uses NPCC’s term “BPS elements.”  

6

A Transmission Owner is an entity “that owns and maintains transmission facilities.”  A Transmission Operator is an

entity that “is responsible for the reliability of its ‘local’ transmission system, and that operates or directs the

operations of the transmission facilities.”  NERC, Glossary of Terms Used in Electric Reliability Standards (Feb. 8, 2012),

http://www.nerc.com/files/Glossary_of_Terms.pdf.   

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

transmission facility outages. Staff visited approximately twenty transmission sites on a 

three-day visit to Connecticut, Massachusetts, and New Hampshire. Staff reviewed 

relevant reports issued by the affected utilities and independent entities. 

A number of agencies in several states affected by transmission and distribution 

facility outages during the October snowstorm are conducting their own inquiries into 

utility performance before, during, and after the event. Staff consulted with many of 

these state agencies, monitored their public proceedings, and discussed with them the 

report’s preliminary findings and recommendations. Staff held outreach meetings with 

the Edison Electric Institute, the American Public Power Association, the National Rural 

Electric Cooperative Association, and the North American Transmission Forum, and also 

shared with them, on a non-public basis, the report’s preliminary findings and 

recommendations. Feedback provided by state agencies and industry associations was 

considered in preparing this report. 

This report: (1) presents staff’s assessment of the October snowstorm event, 

including its impacts on transmission facilities and the BPS, and the causes of 

transmission facility outages; (2) discusses the applicability of the transmission 

vegetation management reliability standard to the event; and (3) provides a number of 

recommendations to industry that, if implemented, could improve utilities’ performance 

and enhance transmission grid reliability during the next large snowstorm or similar 

event. 

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

 

II. Executive Summary

The early autumn snowstorm that hit the Northeast on October 29-30, 2011, was 

unprecedented in the amount of snowfall it produced and particularly devastating 

because of the untimely combination of several factors. As much as two and a half feet of 

heavy, wet snow fell at a time when many trees still had their leaves, following a warm, 

rainy period that left the ground unfrozen, saturated, and soft. The quantity of snow 

held by the unusually top-heavy trees, coupled with the soft, wet ground, resulted in a 

great number of healthy trees, most outside of utility rights-of-way,7

 being uprooted and 

falling onto distribution and transmission lines. 

The storm left a trail of destruction that primarily affected distribution systems. 

Distribution lines were damaged in an estimated 50,000 locations (“trouble spots”) 

throughout the Northeast.8

 Millions of customers9 served by more than two dozen 

utilities lost power. Tens of thousands of customers served by Connecticut Light & 

Power Company (CL&P) were without electricity for more than a week, and some 

customers served by CL&P were without service for eleven days.10 

Most of the damage, and customer outages, was due to impacts to the distribution 

system, which is generally subject to state or local regulation. The transmission system, 

which is subject to the Commission’s jurisdiction, was impacted as well, but it caused 

less than 5% of customer outages at the storm’s peak. Seventy-four transmission lines 

and forty-four transmission substations experienced sustained outages.11 Transmission 

line outages were responsible for approximately 130,000 customer outages around the 

storm’s peak. Most of these outages lasted for less than two days, and none lasted for 

more than five days. Nearly three-quarters of all of the transmission outages were 

7 Utilities rarely own the land on which they site transmission lines.  Instead, utilities obtain rights, usually in the

form of an easement, over portions of property owned by others.  The easement allows the utility to construct,

maintain, and operate transmission facilities and vegetation over a defined area of land, the “right‐of‐way.”

8

A “trouble spot” is a location where there is damage to a line requiring crew response to make conditions safe for

the public, repair damage, and restore power.   

9

In the utility industry, the term “customer” generally refers to a single meter, whether at a residence, a retail store,

or a factory; it does not refer to each person served at that meter.   

10

See WITT ASSOCIATES, CONNECTICUT OCTOBER 2011 SNOWSTORM POWER RESTORATION REPORT 11 (Dec. 1, 2011), available at

http://www.wittassociates.com/assets/860/CTPowerRestorationReport20111201_FINAL_1_.pdf.

11

For purposes of this report, facility outages lasting ten or more minutes are considered “sustained” outages.

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

 

caused when trees weighed down with heavy, wet snow fell onto transmission lines. 

Although most of the damage and outages were on the distribution system, this report 

addresses impacts on, and recommendations for, the FERC-jurisdictional transmission 

system. 

Partly as a result of the August 14, 2003 blackout across the Northeast and Canada, 

which was caused in part by trees growing too close to transmission lines,12 Congress 

passed legislation requiring the Commission to enact mandatory and enforceable 

Reliability Standards. One of those standards, FAC-003-1 (Transmission Vegetation 

Management Program), requires Transmission Owners to develop transmission 

vegetation management programs. These programs must include a schedule for 

vegetation inspections and specific vegetation clearance distances around transmission 

lines, have annual vegetation management work plans, and report certain vegetationrelated outages. 

This Standard’s applicability to this event is limited in that FAC-003-1 only applies 

to transmission lines operated at voltages of 200 kV and above, plus any lower voltage 

lines identified by the applicable Regional Entity as critical to the reliability of the 

electric system in the region — and NPCC has not designated any lower-voltage facilities 

as critical for the purpose of applying FAC-003-1. In fact, FAC-003-1 applied to only one 

transmission facility forced out of service due to vegetation contact — a 345 kV 

transmission line in Connecticut — and that line outage did not cause any loss of service 

to customers. To the extent that a state does not have vegetation management standards 

governing transmission lines operated over 100 kV and the relevant Regional Entity has 

not designated lines operated under 200 kV as critical to the region’s reliability for the 

purpose of applying FAC-003-1, lines operated between 100 kV and 200 kV in that state 

would not be covered by any federal or state vegetation management standard. 

In addition, the Standard’s applicability to the October event is limited because it 

does not specifically address off-right-of-way vegetation management. Further, although 

FAC-003-1 requires each Transmission Owner to “prepare and keep current, a formal 

transmission vegetation management program” that must include the Transmission 

Owner’s objectives, practices, approved procedures, and work specifications,”13 beyond 

this, each Transmission Owner has flexibility on the specific content of its vegetation 

12

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

and Canada:  Causes and Recommendations 139 (Apr. 2004), available at http://www.nerc.com/filez/blackout.html.

13 Reliability Standard FAC‐003‐1, at Requirement R‐1.

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

 

management program, including specific direction on how to address danger trees14

outside of Clearance 115 but within the right-of-way. 

This report makes several recommendations to help reduce the adverse impacts of 

future, similar weather events on the transmission system, including: (1) where 

appropriate, taking targeted steps to address off-right-of-way danger trees; (2) 

employing best practices in managing vegetation on full rights-of-way; (3) laying the 

foundation for effective vegetation management when establishing new rights-of-way; 

and (4) enhancing storm preparedness and response plans as needed. In addition, staff 

recommends increasing reporting of vegetation-caused outages and improving the 

content of required disturbance reports. 

14

A danger tree is any tree that, if it fell, could contact a transmission line.  See, e.g., Accredited Standards Comm.

(ASC) A300, Tree Care Indus. Ass’n, American National Standard for Tree Care Operations — Tree, Shrub, and Other

Woody Plant Maintenance — Standard Practices (Integrated Vegetation Management a. Electric Utility Rights‐of‐

Way) 72.5 (2006) [hereinafter ANSI A300].

15 Clearances are defined and discussed in more detail in Section VII.A.

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

 

III. The October 29–30, 2011 Nor’easter

An unprecedented early fall snowstorm blanketed the upper East Coast with up to 

two-and-a-half feet of snow in about a twenty-four hour period spanning October 29–30, 

2011. Significant October snowstorms are rare, and the 2011 storm broke records 

throughout the Northeast. While the storm and its impacts on trees and power lines 

were not unanticipated, the severity of the storm exceeded forecasts, and its 

repercussions were wide-ranging and severe. 

A. Forecasts and Utility Preparations 

By early in the afternoon of Thursday, October 27, 2011, weather agencies had 

issued forecasts that an unusual October Nor’easter would hit the New England and the 

Mid-Atlantic states on Saturday, October 29.16 Several inches of snow were predicted to 

fall across the Northeast, and that day’s forecasts warned that the coming storm would 

bring down trees and power lines across the region.17 Predictions of maximum total 

snowfall amounts increased rapidly from October 27 to October 29. By the morning of 

October 29, forecasters were predicting up to fifteen inches of snow in some areas.18 The 

snow was expected to begin falling in the late afternoon or early evening of October 29.19 

A number of utilities began preparations for the storm on Friday, October 28. In 

the lead-up to the storm, they held internal planning meetings, increased staff in 

16

See, e.g., CL&P Resp. to Data Req. PURA‐02, Q‐EL‐014, Conn. Pub. Utils. Regulatory Auth. Docket No. 11‐09‐09,

Nov. 23, 2011 (providing the Telvent weather report from 1:00 p.m. on October 27, 2011, which mentioned a storm

arriving on October 29, 2011).  A Nor’easter is a severe winter weather event that produces heavy snow or rain,

severe winds, and significant waves.  A Nor’easter gets its name from the strong northeasterly winds blowing in from

the ocean ahead of the storm and over coastal areas.  Nat’l Oceanic & Atmospheric Admin., National Weather Service

Glossary, http://www.weather.gov/glossary/.

17

See, e.g., CL&P Resp. to Data Req. AG‐03, Q‐AG‐117‐SP01, Conn. Pub. Utils. Regulatory Auth. Docket No. 11‐09‐09,

Nov. 18, 2011 (providing National Weather Service briefing slides used by CL&P to prepare for the storm).

18

See, e.g., CL&P Resp. to Data Req. PURA‐02, Q‐EL‐014, Conn. Pub. Utils. Regulatory Auth. Docket No. 11‐09‐09,

Nov. 23, 2011 (providing the Telvent weather report from 6:00 a.m. on October 29, 2011, which predicted up to

fifteen inches of snow in western Massachusetts).

19 Nat’l Oceanic & Atmospheric Admin., Rare October Winter Storm in the Northeast (Oct. 28, 2011),

http://www.nnvl.noaa.gov/MediaDetail2.php?MediaID=874&MediaTypeID=1.

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

e 

on as the storm is over). 

 

operations centers, and placed in-house and contract field crews on call.20 Regional 

mutual aid groups, through which utilities can request line restoration assistance from 

other utilities, also held conference calls. However, due in part to the moderate snowfall 

amounts in weather predictions from that morning, few utilities requested assistance on 

October 28.21 Nor did many utilities make mutual assistance requests on the morning of 

Saturday, October 29; at that point, there was a general understanding that utilities 

would be holding their crews in order to respond to the event in their own service 

territories.22 However, snowfall amounts exceeded forecasts, and by Saturday 

afternoon, utilities began to see that more manpower would be required to address th

rapidly increasing outages. Many utilities then began requesting aid from the mutual 

assistance groups.23 But because the storm was so widespread — and demand was so 

great — there were few regional crews immediately available.24 In addition, there 

generally was only limited pre-staging of crews (i.e., positioning field workers at 

locations around a utility’s service territory before a weather event so that they will be on

the scene to make repairs as so

Some utilities — in particular, CL&P — have faced criticism at the state level for 

inadequate storm preparation, including failing to request mutual assistance earlier or to 

pre-stage field crews in order to speed response times.25 Utility emergency preparation 

and response is almost entirely outside of the Commission’s jurisdiction.26 However, as 

discussed below, staff’s review of the impact of utility preparation and response on 

transmission restoration found no indication that inadequate preparation materially 

20

See, e.g., Davies Consulting, Final Report:  Connecticut Light and Power’s Emergency Preparedness and Response

to Storm Irene and the October Nor’easter 19 (Feb. 27, 2012), available at http://media2.wtnh.com/docs/Storm‐

Review‐Final‐Report.pdf

21

See, e.g., Witt Associates, supra note 10; Central Hudson gas & Electric Corp., 16 NYCRR — Part105 Compliance

Filing:  Report and Evaluation of October 2011 Snowstorm, October 29–November 4, 2011, at 22‐23 (Jan. 5, 2012),

available at http://documents.dps.ny.gov/public/Common/ViewDoc.aspx?DocRefId={23000E96‐EBCF‐45C1‐BB29‐

387EF9943C33}; Davies Consulting, supra note 20, at 19.

22

See, e.g., CENTRAL HUDSON GAS & ELECTRIC CORP., supra note 21, at 5; WITT ASSOCIATES, supra note10, at 21.

23

See, e.g., CENTRAL HUDSON GAS & ELECTRIC CORP., supra note  21, at 5; WITT ASSOCIATES, supra note 10, at 21.

24

See, e.g., CENTRAL HUDSON GAS & ELECTRIC CORP., supra note  21, at 5; WITT ASSOCIATES, supra note 10, at 21.

25

See, e.g., JOE MCGEE ET AL., REPORT OF THE TWO STORM PANEL, PRESENTED TO:  GOVERNOR DANNEL P. MALLOY 10–11 (Jan. 9,

2012), available at http://www.governor.ct.gov/malloy/lib/malloy/two_storm_panel_final_report.pdf; WITT

ASSOCIATES, supra note 10, at 2‐3.

26 Although several Emergency Operations Reliability Standards deal with registered entities’ responses to

emergency situations, those Standards are focused on BPS operation issues, and not more conventional preparation

and response issues like employee training, staffing levels, or field crew response.

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

t 

e 

artford, 

 

hindered restoration of transmission facilities, as opposed to the more serious 

preparation and restoration problems reported on the distribution side. 

B. Storm Produces Record Amounts of October Snowfall 

Not long after the storm began, it became clear that snowfall totals would exceed 

projections. Wet snow began falling in the late morning of October 29.27 Snowfall was 

heavy by mid-day, and it fell quickly: up to three inches per hour for sustained 

periods.28 Within about twenty-four hours, some areas had received two-and-a-half fee

of snow. The highest amounts of total snowfall were in Massachusetts, where Peru 

recorded 32 inches, and in New Hampshire, where Jaffrey recorded 31.4 inches.29 Th

storm set records for October snowfall across the region. On October 29 alone, H

Connecticut, received 12.3 inches of snow, far surpassing the previous October record of 

1.7 inches.30 That same day, Concord, New Hampshire, received a record 13.6 inches of 

snow, and Worcester, Massachusetts, received a record 11.4 inches.31 The previous 

records were 3.0 inches and 7.5 inches, respectively.32

27 Nat’l Weather Serv., October 29th Historic Early Season Snowstorm,

http://www.erh.noaa.gov/okx/StormEvents/10292011/index.html; DAVIES CONSULTING, supra note 20, at 18.

28 Nat’l Weather Serv. Forecast Office, Boston, Mass., Review of Snow‐tober 2011,

http://www.erh.noaa.gov/box/sigevents/Snowtober_2011/

29 Nat’l Weather Serv., Significant Weather Event:  Oct. 29–30, 2011,

http://www.erh.noaa.gov/box/displayEvent.php?event=Oct_29‐30_2011&element=snow.

30  Nat’l Climatic Data Ctr., CT Daily Snowfall Records Set in October 2011,

http://www.ncdc.noaa.gov/extremes/records/daily/snow/2011/10/00?sts[]=CT#records_look_up.

31 Nat’l Climatic Data Ctr., MA Daily Snowfall Records Set on October 29, 2011,

http://www.ncdc.noaa.gov/extremes/records/daily/snow/2011/10/29?sts[]=MA#records_look_up (providing daily

snowfall records for cities in Massachusetts on October 29, 2011); Nat’l Climatic Data Ctr., NH Daily Snowfall Records

Set on October 29, 2011,

http://www.ncdc.noaa.gov/extremes/records/daily/snow/2011/10/29?sts[]=NH#records_look_up (providing daily

snowfall records for cities in New Hampshire on October 29, 2011).

32 Nat’l Weather Serv., Concord Climate Data For the Year 2011 (Jan. 18, 2012),

http://www.srh.noaa.gov/data/GYX/CLACON; Nat’l Climatic Data Serv.; MA Monthly Snowfall Records Set in 2011,

http://ncdc.noaa.gov/extremes/records/monthly/snow/2011/10/00?sts[]=MA#records_look_up.

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

Figure 1: Snowfall Totals Across the Northeast on October 30, 2011

Source: NOAA, nohrsc.noaa.gov/interactive 

The National Weather Service called the October Snowstorm a “rare and historic 

October Nor’easter”33 and rated it as the strongest fall storm on record for the Northeast 

region.34 Connecticut Governor Dan Malloy said that “a review of state records dating 

back to 1650 indicates that this storm is the most severe October Nor’easter in 

Connecticut history.”35 The only other notable October snowstorm in New England in 

the last one hundred and fifty years, which occurred on October 4, 1987, was far less 

destructive. That storm produced between six and twenty inches of snowfall from 

Albany, New York, to the Western Berkshires in Massachusetts, and caused only about 

300,000 customer outages,36 compared to the more than 3 million outages caused by 

the October 2011 storm. 

 33 Nat’l Weather Serv., Winter Storm Summary for October 29, 2011 Event,

http://www.erh.noaa.gov/phi/show_wss.php.

34 Email from NOAA staff to FERC staff (Mar. 15, 2012) (on file with OE staff).  The October snowstorm is the only

October storm to be ranked by NOAA among the 45 highest‐impact snowstorms that have affected the Northeast

urban corridor.  Nat’l Climatic Data Ctr., The Northeast Snowfall Impact Scale, NOAA,

http://www.ncdc.noaa.gov/snow‐and‐ice/rsi/nesis.

35

Letter from Dannel P. Malloy, Conn. Governor, to Barack Obama, President (Nov. 11, 2011) [hereinafter Malloy

Letter].

36 Robert D. McFadden, Early Snowstorm Covers Northeast, N.Y. TIMES (Oct. 5, 1987),

http://www.nytimes.com/1987/10/05/us/early‐snowstorm‐covers‐northeast.html?pagewanted=all&src=pm.

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

C. Leafy Trees and Prior Rainfall Compound the Impact of 

the Snowstorm 

The effects of record amounts of heavy, wet snow were particularly severe because 

the snow fell across densely wooded areas where deciduous trees had not yet lost many 

of their leaves. Due to an unusually warm and wet September and October, leaf drop 

was significantly lower than normal for late October. For example, before the October 

storm, most of Massachusetts and Connecticut had only experienced “Moderate” — 

rather than the typically “High” — leaf drop.37 The weight of snow on the leaves put 

significant strain on trees, causing limbs to snap and entire healthy trees to fall. 

Figure 2: Leaf Drop Reports, October 2010 vs. October 2011

Source: The Foliage Network 

Moreover, the ground throughout much of the Northeast was saturated due to an 

abnormally wet year — including significant August rainfall from Tropical Storm Irene. 

In fact, August 2011 was the wettest month on record in the Northeast since recording 

began in 1895.38 Because the saturated ground had not yet frozen, the weight of the 

 37

See Report #15 – Oct. 29, 2011, THE FOLIAGE NETWORK,

http://www.foliagenetwork.net/index.php?option=com_content&view=article&id=333:ne‐foliage‐report‐15‐

2011&catid=34:northeast‐us&Itemid=68; Report #15 – Oct. 30, 2011, THE FOLIAGE NETWORK,

http://www.foliagenetwork.net/index.php?option=com_content&view=article&id=275:ne‐foliage‐report‐

10302010&catid=62:northeast‐us&Itemid=85.

38

In August 2011 an average of 8.53 inches of precipitation was recorded in the Northeast, while the 20th century

regional average is only 3.85 inches.  Nat’l Climatic Data Ctr., Precipitation Rankings August 2011 Northeast, NOAA,

http://www.ncdc.noaa.gov/temp‐and‐

precip/ranks.php?parameter=pcp&state=101&div=0&periods[]=1&month=8&year=2011.  The year 2011 was also the

wettest year on record for the Northeast since 1895:  an average of 56.04 inches of precipitation was recorded, while

the 20th century average is only 41.08 inches.  Nat’l Climatic Data Ctr., Precipitation Rankings December 2011

Northeast, NOAA, http://www.ncdc.noaa.gov/temp‐and‐

precip/ranks.php?periods%5B%5D=12¶meter=pcp&year=2011&month=12&state=101&div=0.

 15
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

 

heavy, wet snow on leafy trees caused many healthy trees across the region to uproot. 

On November 1, 2011, the Connecticut Department of Transportation estimated there 

were 24,000 trees downed on Connecticut roads alone. As explained by Governor 

Malloy: 39 

“The combination of heavy wet snow and near freezing air caused adherences of 

the snow to all objects including trees, which had not yet lost their seasonal 

foliage. The weight of the snow on trees and power lines, combined with very 

wet soils as a result of Tropical Storm Irene and the remnants of Tropical Storm 

Lee, quickly overwhelmed the ability of trees to remain upright under the added 

weight. This added weight de-limbed hundreds of thousands of trees and 

uprooted tens of thousands of additional trees in just 12 hours.” 

The October snowstorm crippled much of the Northeast. As noted above, more 

than 3 million customers lost electric power. Activity in the affected states ground to a 

halt: many roads were impassable and scores of schools and businesses closed.40 States 

of emergency were declared in many states, including Connecticut,41 Massachusetts,42

New Hampshire,43 and parts of New York.44 News reports identified at least twenty-two 

storm-related deaths.45 The National Oceanic and Atmospheric Administration 

estimates the costs of the storm to be between $850 and $900 million, and one unofficial 

estimate puts the costs at more than $3 billion.46

39

See Malloy Letter, supra note 35.

40

See Lauren Keiper, Millions Without Power After US Northeast Snowstorm, REUTERS (Oct. 31, 2011),

http://www.reuters.com/article/2011/10/31/uk‐weather‐northeast‐idUSLNE79U02Y20111031.

41

Press Release, Gov. Malloy Declares State of Emergency (Oct. 29, 2011), available at

http://www.governor.ct.gov/malloy/cwp/view.asp?A=4010&Q=.

42

Press Release, Governor Lynch Requests FEMA’s Reconsideration of Emergency Disaster Declaration (Nov. 2,

2011), available at http://www.governor.nh.gov/media/news/2011/110211‐emergency.htm.

43

Press Release, Governor Patrick Meets with Utility Company Officials on Storm and Power Recovery Efforts (Oct.

31, 2011), available at http://www.mass.gov/governor/pressoffice/pressreleases/2011/111031‐storm‐power‐

recovery.html.

44

Press Release, Governor Cuomo Declares State of Emergency for Counties Hit Hard by Winter Storm (Oct. 29,

2011), available at http://www.governor.ny.gov/press/10292011stateofemergency.

45

CNN Wire Staff, Freak Snowstorm Blamed for at Least 22 Deaths, CNN (Nov. 3, 2011),

http://articles.cnn.com/2011‐11‐03/us/us_east‐coast‐storm_1_carbon‐monoxide‐poisoning‐cl‐p‐power‐

outages?_s=PM:US.

46

AON BENFIELD, OCTOBER 2011 MONTHLY CAT RECAP – IMPACT FORECASTING 2 (Nov. 3, 2011), available at

http://thoughtleadership.aonbenfield.com/ThoughtLeadership/Documents/201111_if_monthly_cat_recap_october.p

df; Mary O’Leary, Gov. Malloy: “What We Need is Action” on Connecticut Power Crisis, NEW HAVEN REGISTER (Nov. 2,

2011), http://www.governor.ct.gov/malloy/cwp/view.asp?A=11&Q=489996 (quoting Governor Malloy as anticipating

 16
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

 

IV. Significant and Widespread Damage to Electric

Delivery Infrastructure

The October storm’s historic snowfall and resulting tree damage devastated the 

system of high and low voltage wires that distribute power across the Northeast, leaving 

approximately 3.2 million customers from Pennsylvania to Maine without power near 

the end of the storm. The vast majority of the damage to electric delivery infrastructure 

was to the distribution system. However, the storm’s impact on transmission facilities 

was also significant. Seventy-four transmission lines in a half-dozen states experienced 

sustained outages. 

A. Distribution Facility Damage and Customer Impact 

Exact measures of the total physical damage to distribution systems are hard to 

determine, but there were an estimated 50,000 separate locations across the Northeast 

where utility crews were required to remove trees from or physically repair distribution 

lines (“trouble spots”). This serious and widespread damage to distribution facilities 

caused more than 95% of customer outages. The map on the next page overlays a 

snapshot of several utilities’ customer outages on a map showing snowfall totals across 

the Northeast. 

storm costs would exceed $3 billion); Email from NOAA staff to FERC staff (Mar. 29, 2012) (estimating costs at

between $850 million and $900 million) (on file with OE Staff).

 17
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

Figure 3: Snowfall Amounts and Customers That Lost Power

Source: NOAA, National Operational Hydrologic Remote Sensing Center, Interactive Snow 

Information47 and U.S. Department of Energy, Energy Assurance Daily.48 

There was significantly more damage to distribution facilities than transmission 

facilities for a number of reasons, including the fact that in some areas there are 

approximately twenty times more miles of distribution lines than transmission lines.49 

In addition, under typical industry practices, vegetation is generally allowed to grow 

much closer to distribution lines than transmission lines because there is less risk of 

flashover50 between low-voltage distribution lines and nearby trees. 

 47 Available at

http://www.nohrsc.nws.gov/interactive/html/map.html?ql=station&zoom=&loc=Latitude%2CLongitude%3B+City%2C

ST%3B+or+Station+ID&var=snowfall_72_h&dy=2011&dm=10&dd=30&dh=0&incr=+%2B+&snap=1&o9=1&lbl=m&mo

de=pan&extents=us&min_x=‐76.041666666669&min_y=33.741666666667&max_x=‐

63.450000000002&max_y=43.816666666667&coord_x=‐

69.745833333336&coord_y=38.779166666667&zbox_n=&zbox_s=&zbox_e=&zbox_w=&metric=0&bgvar=dem&shdv

ar=shading&palette=1&width=1000&height=800&nw=1000&nh=800&h_o=2&font=0&js=1&uc=0

48 

U.S. Department of Energy, supra note 1.

49 

See About NU, Northeast Utilities, http://www.nu.com/aboutnu/nufacts.asp (listing 4,500 circuit miles of

transmission lines and 72,000 pole miles of distribution lines).   

50 Flashover is the spontaneous arcing of electricity from a line to a grounded object like a tree.

 18
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

A number of state utility commissions and other state government agencies have 

initiated inquiries into the distribution-level customer outages caused by the storm.51 In 

addition, several utilities (and some independent entities) have produced reports on the 

event that focus on distribution system impacts.52

B. Transmission Facility Damage and Customer Impact 

Although its impact was not as extensive as the damage to the distribution 

system, the October snowstorm impacted many transmission facilities. Near the end of 

the storm, about 130,000 customers across six states lost power as a result of 

transmission line outages. 

1. Transmission Outages

Of the seventy-four transmission lines forced out of service for a sustained period 

during to the storm, the vast majority (seventy) were 115 kV facilities. One 138 kV and 

three 345 kV lines also experienced outages. 

 51 The Connecticut Public Utilities Regulatory Authority (Docket No. 11‐09‐09), the Massachusetts Department of

Public Utilities (Docket No. 11‐119), the New Hampshire Public Utilities Commission, and the New York State Public

Service Commission (Case No. 11‐M‐0595) are all conducting inquiries.

52

See, e.g., Central Hudson Gas & Electric Corp., supra note 21; Consolidated Edison Company of New York, Inc.,

Report on Preparation and System Restoration Performance:  Nor’easter October 29 through November 3, 2011 (Jan.

5, 2012), available at http://documents.dps.ny.gov/public/Common/ViewDoc.aspx?DocRefId={512EF4A0‐EC4C‐4204‐

A527‐B047022B6FC3}; Davies Consulting, supra note 20; McGee, supra note 25; Public Service of New Hampshire,

Amp Up and Power On:  October Nor’easter 2011 (Nov. 2011), available at

http://www.hollisnh.org/announce/2011OctoberNor'easterReport.pdf; Western Massachusetts Electric Company’s

Report to the Department of Public Utilities on Expectations for Electric Distribution Company Performance Regarding

Emergency Events (Dec. 20, 2011), available at http://www.env.state.ma.us/dpu/docs/electric/11‐119/12202011‐

tech‐session.pdf.  

 19
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

Figure 4: Transmission Line Outages by Voltage Level

There were also seven brief — between one and nine minute — line trips, four of 

which were caused by relay misoperations.53 

Twenty-three of these seventy-four line outages occurred on NPCC-designated BPS 

elements. As explained in footnote 5, NPCC uses a performance-based test to designate 

facilities as BPS elements.54

 53 Relay misoperations occur when an automated line monitoring and communications device — a relay — transmits

an incorrect signal to a line’s breakers, causing the breakers to open when that action is not necessary.  Failure of a

relay to operate when it should is also considered a misoperation.  The one relay misoperation that resulted in a

transmission line outage of ten or more minutes is discussed in Section V.C.

54

NERC has filed, for Commission consideration, a revised definition of BES that would impose a bright‐line threshold

of 100 kV, such that if approved, all facilities over 100 kV would be part of the Bulk Electric System and subject to

most Reliability Standards unless a specific exception was granted or generic inclusion was made.  See N. Am. Elec.

Reliability Corp., Petition, Docket No. RM 12‐06‐000 (filed Jan. 25, 2012).  This report takes no position on the BES

definition filing.

 20
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

Figure 5: Total Outages: BPS vs. Non‐BPS Elements

Because transmission lines conduct power from generating facilities to substations, 

transmission line outages can cause substation outages.55 During the October 

snowstorm, transmission line outages forced forty-four transmission substations out of 

service, including one NPCC designated as a BPS element. Loss of power to transmission 

substations is significant for two main reasons. First, many transmission substations 

provide power to distribution systems, so that the loss of power to a transmission 

substation can result in thousands of customer outages. Second, transmission 

substations contain relays and breaker controls that operate to protect individual 

transmission lines and stabilize the power grid as a whole. When a substation’s power 

source is lost, substation battery banks provide backup power to control equipment and 

breakers, but those batteries only last for a limited period of time, at which point the 

equipment can no longer perform its functions. These forty-four transmission 

substation outages, combined with seventy-four transmission line outages, constituted a 

significant transmission event. 

 55

Sometimes only one transmission line feeds power to a substation.  If that single source line experiences an

outage, the entire substation will be out of service.  Generally, multiple transmission lines provide power to a

substation; in that case, the substation will go out of service because of transmission line outages only if all of the

transmission lines serving that substation are out of service.

 21
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

2. Affected States and Utilities

A half-dozen states — Connecticut, Maine, Massachusetts, New Hampshire, New 

York, and Rhode Island — and ten utilities experienced transmission outages on lines 

they own, or co-own and maintain. Half of those outages occurred in just one state, 

Connecticut.56 The chart below shows the number of outages by state. 

Figure 6: Transmission Line Outages by State and Voltage Level

As the following map shows, transmission line outages were concentrated in the 

Connecticut River Valley area, through Connecticut and into Massachusetts. 

 56 Other states, such as Pennsylvania and New Jersey, experienced significant snowfall and distribution facility

outages, but no transmission facility outages.

 22
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

 

New England Transmission Line Outage 

Figure 7: ISO‐NE Transmission Line Outages During the October Snowstorm

Source: ISO-New England 

The service territories of CL&P and Western Massachusetts Electric Company 

(WMECO), two subsidiaries of Northeast Utilities (NU), largely cover this area. As 

shown in the chart below, these two companies had the most transmission line outages. 

A third NU subsidiary, Public Service of New Hampshire (PSNH), had an additional 

three transmission line outages. Overall, outages of facilities owned — or co-owned, 

operated, and maintained — by NU subsidiaries57 accounted for fifty-four of the October 

storm’s seventy-four transmission line outages (approximately 74%). 

57

NU and NSTAR merged on April 10, 2012, and NSTAR is now a subsidiary of NU.  Because the merger occurred after

the October snowstorm, this report does not include NSTAR as an NU subsidiary.

 23
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

Figure 8: Line Outages by Company and Voltage Level58

3. Transmission Facility Outages Had Relatively Limited Impacts on Customers and

Were Restored Quickly

Although seventy-four transmission line outages is a significant transmission event, 

these outages impacted far fewer customers than the distribution facility outages. At the 

storm’s peak, damage to the transmission system caused approximately 130,000 homes 

and businesses to lose power, less than 5% of all of the storm-related customer outages. 

In addition, the peak number of transmission-caused customer outages (which rose 

above 100,000 customers for only about two hours) was relatively small compared to 

distribution-caused outages. While many customers impacted by distribution facility 

outages were without service for more than five days – and some for eleven – service was 

restored to all customers that lost power due to transmission outages in less than five 

 58 The full names of the utility companies included in this chart are: Bangor Hydro Electric Co.; Central Hudson Gas &

Electric Corp.; Connecticut Light & Power Co.; Holyoke Gas & Electric Department; National Grid USA; NSTAR Electric

& Gas Co.; New York State Electric & Gas Co.; Orange & Rockland Utilities, Inc.; Public Service of New Hampshire; and

Western Massachusetts Electric Co.  Where a line is co‐owned by more than one utility, this report attributes the

outage to the company with the responsibility for maintaining the line where the outage occurred.

 24
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

days. In fact, service was restored to the majority (77% percent) of such customers in 

less than forty-eight hours. 

Figure 9: Timeline of Customers Affected by a Transmission Station Outage  

While most transmission facilities were restored relatively quickly, four were out of 

service for nearly a week, and an additional three remained out of service between seven 

and eight days. However, none of these seven transmission line outages resulted in 

customer outages or were, at that time, necessary for BPS stability. The following chart 

illustrates the duration of transmission line outages. 

 25
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

Figure 10: Duration of Transmission Line Outages

Utilities faced several physical obstacles in restoring the seven transmission lines 

that were out of service for six to eight days. Each of these lines or its supporting 

structures had significant structural damage that required rebuilding. For example, on 

five of these seven lines, falling trees snapped insulators, cross-arms, and various 

support structures. In addition, the site of the damage to the 345 kV line that was out of 

service for nearly eight days was particularly difficult to access. Again, no retail 

customers were without service due to these seven line outages. 

One of the reasons for fast restoration of many transmission lines that caused 

customer outages is that, in setting priorities for transmission line restoration, utilities 

focus on restoration of lines that impact customers and are important for grid stability. 

For example, NU’s restoration priorities for the storm event were: (1) transmission lines 

that would restore more than one substation; (2) transmission lines that impacted one 

substation; (3) 345 kV lines; (4) lines that served substations with only one live-line 

feeding them, such that if the live-line went out of service, the substation — and 

customers served by it — would experience an outage (i.e., single contingency load loss 

situations); and (5) all other transmission lines. 

 26
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

 

Staff concludes that restoration of transmission lines was not materially 

hampered by inadequate utility preparation or response.59 For example, staff finds that, 

overall, additional staffing or field crew pre-staging would not have significantly 

enhanced transmission facility restoration. However, staff — and utilities themselves — 

recognize that there is room for improvement in storm preparedness. NU informed staff 

that its restoration of transmission facilities would have happened somewhat faster, 

albeit minimally, if the company had obtained more outside assistance in advance of the 

storm, pre-staged some crews, and had access to additional damage assessment 

equipment (specifically, helicopters and infrared cameras). Therefore, although utility 

preparation did not pose significant problems for restoration of transmission facilities 

during this event, staff recommends in Section IX.4 several steps utilities can take to 

improve preparation for future severe storm events. 

59 Staff recognizes that a number of states are looking into the impact of utility preparation and response on the

distribution system as part of their ongoing proceedings relating to the storm’s impacts on customers in their state.  

This report makes no findings regarding impacts of utility preparation and response on restoration of distribution

facilities.  

 27
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

V. Causes of Transmission Facility Outages

As could be expected from a major snowstorm, the vast majority of transmission 

line outages during the October event were caused by tree contact or the accumulation of 

ice and heavy, wet snow on transmission conductors.60 Other causes included losses of 

source

61 and relay misoperation. 

Figure 11: Line Outages by Cause Category and Voltage Level

 60

Transmission lines, the wires that carry electricity, are also called conductors.

61 “Loss of source” outages occur when a connected line, or series of lines, trip and no longer feed an interconnected

transmission line, meaning the interconnected line no longer has a source of electrical energy.

 28
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

 

A. Tree Contact 

The vast majority of transmission line outages — fifty-five out of seventy-four, or 

nearly 80% — were caused when snow-weighted leafy trees contacted transmission lines.

62 All but two of these trees were healthy. Twenty-five percent of these trees were 

located within the utility’s right-of-way, and therefore, were likely within the utilities’ 

rights to maintain. 

Specifically, thirty-nine transmission line outages resulted from off-right-of-way 

trees falling onto transmission lines, resulting in loss of power to approximately 84,000 

customers. An additional twelve transmission line outages, resulting in 13,000 customer 

outages, occurred when trees located inside a utility’s full right-of-way63 fell into 

transmission lines. The only tree-caused 345 kV line outage occurred when a sixty-fivefoot tall tree located within a full right-of-way (forty-six feet from the nearest 

transmission line) fell. All of the trees that fell into lines from within the utility’s full 

right-of-way were located outside the area in which the utility performs vegetation 

management (known as the “maintained right-of-way”).64

62 Utilities attributed four of those fifty‐five outages to tree contact, but post‐storm field inspections by the utilities

could not definitively confirm that explanation.  Based on review of the data, staff accepts the utilities’ attribution of

these four outages to tree contact.

63

For purposes of this report, “full right‐of‐way” means the portion of land for which a utility has documented

legal rights to build and maintain transmission facilities.   

64

As explained in Section VII.B, no Reliability Standard requires that utilities manage vegetation on the entire width

of their full rights‐of‐way.  In fact, managing a narrower maintained right‐of‐way, rather than the full right‐of‐way, is a

relatively common industry practice, though not a best practice.

 29
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

Figure 12: Fallen Trees Located on Rights‐of‐Way and Off‐Rights‐of‐Way

The 115 kV line in the photograph below was forced out of service when several 

trees, each over sixty feet tall and located twenty to thirty feet outside of the utility’s full 

right-of-way, uprooted and fell onto three separate spans of the line. Transmission lines 

are not always located in the middle of a right-of-way, but instead often are closer to an 

edge of the right-of-way. Thus, as is the case here, a tree may be outside the boundaries 

of a 130 foot wide right-of-way but still less than sixty-five feet from a conductor. 

 30
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

Figure 13: Trees Fallen on 115kV Line in Connecticut

Source: Northeast Utilities 

The line in the photograph below is a 115 kV line in Massachusetts that went out of 

service when a seventy-five foot tall tree located outside of the 100 foot wide maintained 

right-of-way, but inside the 200 foot wide full right-of-way, fell onto the line. Because 

the transmission line was not centered on the right-of-way, the base of the tree, while 

outside the maintained right-of-way, was only about 30 feet from the nearest conductor. 

 31
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

Figure 14: Tall Tree Fallen on an 115kV line in Massachusetts

Source: Northeast Utilities 

As noted above, data obtained during the inquiry indicates that some of the affected 

utilities only manage vegetation on narrower maintained rights-of-way rather than their 

full rights-of-way. For example, one utility’s maintained right-of-way widths for 115 kV 

lines range from 68 feet to 280 feet despite having easements of 88 feet to 325 feet. One 

345 kV line is located on a 340-foot wide easement, but only 280 feet of the right-of-way 

is maintained. Staff finds that the removal of danger trees from full rights-of-way could 

have prevented the twelve 115 kV transmission line outages (six of which were NPCCdesignated BPS elements) that resulted from on-right-of-way tree contact during the 

October Nor’easter. Preventing those line outages would have avoided approximately 

13,000 customer outages.65 Based on the findings outlined above, staff makes several 

recommendations regarding right-of-way management in Section IX. 

 65 Further complicating right‐of‐way management is the fact that, for a variety of reasons, some utilities find it

difficult to locate the exact edges of many rights‐of‐way in the field.  

 32
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

B. Transmission Structure Failures 

Extreme weather conditions caused several transmission facilities to break, 

resulting in transmission line outages. Temperatures during the snowstorm hovered 

around 32 degrees, which is conducive to the accumulation of ice and snow on 

transmission lines. The weight of the accumulated ice and snow on conductors, and, in 

one case, high wind conditions, caused a number of structures — including static wires,66

conductors, insulators,67 and cross-arms68 — to break, resulting in six transmission line 

outages and approximately 32,000 customer outages. Although a number of the 

transmission structures that failed were several decades (or even more than fifty years) 

old, it does not appear, based on data obtained during the inquiry, that these structures 

were in need of repair before the storm. Data reviewed by staff also indicates that the 

affected structures had been maintained according to utility plans, which staff finds are 

consistent with typical utility practice. 

Figure 15: Structure Failure on a 345kV Line in Connecticut

 66

Static wire (also known as shield wire) is grounded wire that is strung above conductors to protect them from

lightning strikes.  The static wire is connected to the grounded tower structure and provides a path for lightning to

discharge into the earth.  

67

Transmission line insulators are devices used to contain, separate, or support electrical conductors on high‐voltage

electricity supply networks.  Their purpose is to prevent electricity from arcing between conductors or from

conductors to the ground.  

68

Cross‐arms are the structures located near the top of transmission poles or metal towers that support conductors.  

 33
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

 

The 345 kV line shown in the photograph above was forced out of service when the 

weight of ice and heavy, wet snow on conductors damaged a structure and broke a 

conductor, static wire, cross-arms, guy-wires,69 and insulators. This photograph shows 

(in the background) a wood pole where cross-arms and guy-wires have broken and the 

conductor has fallen to the ground. 

C. Other, or Unknown, Causes 

Several transmission line outages were the result of various other, or unknown, 

causes. 

 Eight lines experienced outages as a result of other transmission line failures 

(i.e., losses of source); these lines were each energized by only one other 

transmission line, so that when that feeder transmission line failed, the 

adjacent line also experienced an outage. These loss-of-source transmission 

line outages caused approximately 16,000 customers to lose power. 

 A relay misoperation caused one 115 kV line to be out of service for 

approximately five hours. As described in footnote 53, a relay misoperation 

occurs when an automated line monitoring and communications device — a 

relay — transmits an incorrect signal to a line’s breakers, causing the 

breakers to open when that action is not necessary. In this case, a relay 

incorrectly detected a problem on the line and forced it out of service. The 

misoperation did not result in loss of service to any customers. 

 One 115 kV line was forced out of service when a circuit breaker component 

became stuck. The stuck component prevented the breaker from isolating a 

line that had experienced a fault, resulting in the interconnected 115 kV line 

losing power. This stuck breaker condition caused about 4,900 customers to 

lose power for approximately one-and-a-half hours. 

 Utility inspections of one 345 kV and two 115 kV transmission lines that 

experienced outages did not reveal any damage to transmission structures or 

nearby vegetation, and there is no indication of equipment misoperations. 

Therefore, the causes of these outages could not be determined by the utility. 

No customers lost power because of the 345 kV line outage. Approximately 

3,800 customers lost service for approximately four to twelve hours as a 

result of the two 115 kV line outages. Possible causes of those two line 

outages are undetected tree contacts or arcing across an insulator due to 

accumulated snow and ice. 

69

A guy‐wire is a tensioned cable designed to add stability to structures like utility poles.  One end of the cable is

attached to the structure and the other is anchored to the ground at a distance from the structure’s base.

 34
Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

 

VI. Transmission Outages Did Not Destabilize the BPS or

Regional Systems

Despite the number — and, in some cases, the duration — of the transmission 

facility outages caused by the storm, the stability of the BPS and the operations of the 

transmission systems operated by ISO-New England (ISO-NE) and the New York 

Independent System Operator (NYISO) were never impaired. This was the result of two 

main factors: a significant decrease in load resulting from distribution facility damage 

and, to a lesser extent, preventative measures taken by ISO-NE. 

A. Bulk Power System Impacts 

The loss of seventy-four transmission lines — including twenty-three BPS elements 

— during the October snowstorm did not strain the BPS. There were no Special 

Protection System70 operations. System operators were not required to shed load or take 

other mitigating measures to maintain reliability. All transmission substations that went 

out of service were restored before their batteries were depleted; thus, the stability and 

control of the BPS was not threatened due to those substation outages. In short, the 

transmission system held up well. An important reason for this, however, is that the 

damaged distribution system significantly reduced the demands placed on the 

transmission system. The dramatic drop in power usage (also known as “loss of load”) 

that occurred when millions of customers lost power due to distribution facility damage 

eased the burden on transmission facilities across the Northeast. Under normal load 

conditions, seventy-four transmission facility outages could have caused swings in 

voltage and changes in flows requiring system operators to take emergency actions, 

possibly including load shedding, in order to prevent cascading outages.71

Of course, utilities and regulators strive to prevent loss of load, the effects of which 

can cause significant harm to customers and the economy. Efforts are currently under 

way in many Northeastern states to prevent significant damage to distribution systems 

70 Special Protection Systems are systems designed to automatically detect abnormal conditions on a

transmission system and to take corrective action.  See NERC, supra note 6.

71

A cascading outage is a sequence of events where an initial event, or set of events, triggers a series of other

outages.  Cascading outages can result in widespread power outages, such as those that occurred during the 2003

Blackout.  However, in some cases, outages can be halted before the sequence results in a major interruption of

electricity service.  

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in future storms in order to minimize customer outages.72 If these efforts succeed, then 

load loss resulting from distribution facility damage during severe weather will diminish, 

which could then increase the demands on transmission lines during and immediately 

after storm events. Therefore, while it has always been important that utilities take steps 

to minimize weather-caused transmission line outages, it becomes especially important 

to do so as efforts are underway to minimize load loss caused by distribution facility 

damage.73 

Although the transmission line outages caused by the October snowstorm did not 

significantly impact the BPS, future storms could cause greater harm to the BPS, and 

there are valuable lessons that can be learned from this event. Therefore, staff 

recommends in Section IX that utilities consider targeted actions to better protect 

transmission facilities. In particular, as discussed below, staff recommends that, where 

appropriate, utilities take steps to improve maintenance of their rights-of-way and take a 

targeted approach to enhance management of off-right-of-way danger trees, focusing on 

protecting lines rated at 200 kV and above, and lower-voltage transmission lines that, if 

lost, would negatively impact the overall reliability of the Bulk Electric System. 

B. Regional System Impacts 

Transmission facility outages during the storm also had no detrimental impact on 

the ISO-NE or NYISO operations. The ten transmission line outages in the NYISO74

region did not impact the reliability or operation of the NYISO system: no system 

operating limits were exceeded, no generation was lost, and all applicable reserve 

margins were maintained. There was no need for NYISO to implement any emergency 

procedures or alerts. 

72

For example, the Connecticut legislature recently passed a bill that, among other things, requires the state

Public Utilities Regulatory Authority to establish standards for electric utilities in preventing outages, restoring

power, trimming trees, and for emergency planning, staffing, mutual aid policies, and power restoration

coordination efforts with telecommunication companies.  SB 23, Reg. Sess. (Conn. 2012).   

73

As during the October snowstorm, future severe storms events that damage transmission lines will also likely

damage distribution lines for the simple reason that large‐scale tree failures will not occur only, or even primarily,

near transmission lines.   

74

NYISO is the independent, non‐profit organization that operates New York State’s transmission network,

administers its wholesale electricity markets, and serves as the state’s NERC‐certified Reliability Coordinator.  A

Reliability Coordinator is “[t]he entity that is the highest level of authority who is responsible for the reliable

operation of the Bulk Electric System [in a defined area], has the Wide Area view of the Bulk Electric System, and

has the operating tools, processes and procedures, including the authority to prevent or mitigate emergency

operating situations in both next‐day analysis and real‐time operations.”  NERC, supra note 6.

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Nearly all transmission facility outages — sixty-four — occurred on the ISO-NE75

system, but they caused no significant operating impacts. ISO-NE implemented limited 

procedures to ensure the reliability of the region’s transmission system before, during, 

and after the snowstorm. In anticipation of the snowstorm, ISO-NE implemented an 

Abnormal Conditions Alert (Master/Local Control Center Procedure 2 (M/LCC-2)) at 

1:00 p.m. Eastern Daylight Time (EDT) on Saturday, October 29. This alert protects the 

stability of the transmission system by requiring market participants to postpone 

scheduled maintenance, construction, or testing activities in order to maintain reliability 

in the face of unplanned outages or similar conditions. ISO-NE cancelled the Abnormal 

Conditions Alert at 11:15 a.m. EDT on Monday, November 7, 2011. 

The storm’s most significant impact on ISO-NE operations was the significant loss 

of load caused by the damage to distribution and, to a lesser extent, transmission lines. 

As a result of the dramatically decreased demand, by Sunday, October 30, ISO-NE had 

more generation scheduled to run than it needed. In order to reduce the planned power 

output and keep the system in balance on October 30, ISO-NE twice implemented a 

Minimum Generation Emergency. This declaration allowed ISO-NE to require 

generators to operate below the minimum level at which it is economic to run. 

Finally, approximately 1,500 MW of generation capacity in ISO-NE went offline 

during the storm.76 However, ISO-NE maintained its required reserve margins at all 

times.77 All but one of these generation outages were resolved by 9:00 a.m. EDT on 

October 31. The remaining generator was restored on November 2. The loss of 

generation capacity had no impact on the stability of the ISO-NE system or the BPS 

because load levels dropped so significantly during and after the storm that the power 

the facilities could have produced was not needed. 

75

ISO‐NE is a private, non‐profit organization that operates the transmission grid, administers the energy markets,

and serves as the NERC‐certified Reliability Coordinator for Connecticut, Maine, Massachusetts, New Hampshire,

Rhode Island, and Vermont.   

76

Twenty‐one small units in total were offline; twelve were offline due to loss of transmission lines serving those

facilities, seven due to loss of communications for remote start capability, and two due to generator step‐up

transformer trips.

77

A generation reserve margin is the amount of generation capacity required to be available at any given time in

excess of the amount of generation that is anticipated to be needed to meet actual demand.  Reserve margins ensure

that there will be enough generation available to meet demand that exceeds projections or to compensate for

unanticipated losses of other sources of generation.  See NERC, Reliability Indicators:  Planning Reserve Margin,

http://www.nerc.com/page.php?cid=4%7C331%7C373.

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

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VII. Applicability of the Transmission Vegetation

Management Reliability Standard

As discussed above, the majority of transmission facility outages and related loss of 

load that occurred during the October snowstorm were the result of vegetation contact 

with transmission lines. Therefore, the FERC-approved Reliability Standard most 

relevant to this event is FAC-003-1 (Transmission Vegetation Management Programs). 

However, its applicability to the October snowstorm event is limited. 

A. Overview of Reliability Standard FAC-003-1 

Reliability Standard FAC-003-178 was developed by the industry with the purpose 

of preventing outages from vegetation located in transmission rights-of-way and 

minimizing outages from vegetation adjacent to the right-of-way.79 The standard 

requires Transmission Owners to document a transmission vegetation management 

program (TVMP) that defines a schedule for right-of-way vegetation inspections based 

on anticipated vegetation growth and other relevant factors.80 TVMPs must identify two 

minimum clearances around transmission lines: a “Clearance 2,” the minimum distance 

around transmission lines to be maintained at all times in order to prevent flashover 

between the lines and vegetation;81 and a “Clearance 1,” the distance around 

transmission lines utilities will clear to when performing periodic maintenance so as to 

prevent vegetation from growing into the Clearance 2 space during maintenance 

intervals.82 The TVMP also must specify a schedule for, and methods of, vegetation 

78 Reliability Standard FAC‐003‐1 was approved by FERC on March 16, 2007, in Order No. 693, FERC Stats. & Regs. ¶

31,242, and became mandatory and enforceable on June 18, 2007.

79 Reliability Standard FAC‐003‐1 (Transmission Vegetation Management Program), at A.3.

80 Id., at Requirement R1.1.

81 Id., at Requirement R1.2.2.  Clearance 2 distances must be at least as great as the clearances set forth in IEEE

Standard 516‐2003, which range from 0.75 to 6.24 meters (2.45 to 22.44 feet) between conductors and grounded

objects like vegetation, depending on the conductor’s rating.  INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS GUIDE FOR

MAINTENANCE METHODS ON ENERGIZED POWER LINES 20, 94 (2003).

82 Reliability Standard FAC‐003‐1, at Requirement R1.2.  As the Commission explained in Order No. 693, FAC‐003‐1’s

clearance requirements mandate that Transmission Owners establish “sufficient clearances to prevent outages due to

vegetation management practices under all applicable conditions.”  Order No. 693, FERC Stats. & Regs. ¶ 31,242 at P

729.  The Commission noted that “all applicable conditions” does not include the extraordinary circumstances

specified in Requirement R3.2, which excludes “natural disasters (including wind shears and major storms) that cause

vegetation to fall into the transmission lines from outside the [right‐of‐way].”  Id.

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inspections.83 In addition, utilities are required to develop annual plans for vegetation 

management work to ensure reliability, taking into account various factors, such as 

anticipated vegetation growth.84 Finally, Transmission Owners must report certain 

vegetation-related outages to the relevant Regional Entity.85

Unlike the vast majority of Reliability Standards, which apply to all BES facilities 

(i.e., generally, those operated at or above 100 kV, or otherwise as determined by the 

Regional Entity), FAC-003-1 applies only to BPS “transmission lines operated at 200 kV 

and above and to any lower voltage lines designated by the [Regional Entity] as critical to 

the reliability of the electric system.”86 This means that the Standard does not apply to 

lines operated at voltages under 200 kV in the NPCC region unless NPCC has designated 

those lines as “critical” under the Standard. NPCC has not designated any transmission 

lines rated under 200 kV as “critical” for the purposes of applying FAC-003-1. 

When approving FAC-003-1, the Commission acknowledged that, although the 

proposed Standard gave Regional Entities discretion to designate lines under 200 kV to 

which the Standard would be applicable, no Regional Entity had actually designated any 

lower-voltage lines as critical for that purpose.87 The Commission expressed the concern 

that a bright-line 200 kV threshold for application of the Standard would “exclude a 

significant number of transmission lines that could impact Bulk Power System 

reliability.”88 However, in response to industry concerns that, among other things, the 

costs of expanded applicability to sub-200 kV facilities could outweigh the benefits, the 

Commission did not require NERC to revise FAC-003-1 immediately. Instead, it 

directed NERC to “revise it through the Reliability Standards development process, with 

the expectation that the applicability of this Reliability Standard will expand to include 

additional facilities that impact reliability that currently are not covered by this 

Reliability Standard.”89

 

83 Reliability Standard FAC‐003‐1, at Requirement R1.

84 Id., at Requirement R2.

85 Id., at Requirement R3.

86 Id., at A.4.

87 Order No. 693, FERC Stats. & Regs. ¶ 31,242 at P 706.

88 Id.

89

See id. P 710.

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

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Because NPCC does not apply FAC-003-1 to any sub-200 kV BPS elements, FAC003-1 only applied to one line — a 345 kV line in Connecticut — that was forced out of 

service due to tree contact during the October snowstorm.90 That line’s outage did not 

result in any customer outages. Thus, although the October snowstorm outages were 

almost entirely caused by vegetation contact, the Transmission Vegetation Management 

Reliability Standard applied to only one of the fifty-five transmission lines forced out of 

service by tree contact (and applied to none of the distribution lines damaged in the 

storm).91 To the extent that a state does not have vegetation management standards 

governing transmission lines operated over 100 kV92 and the relevant Regional Entity 

has not designated lines operated under 200 kV as critical to the region’s reliability for 

the purpose of applying FAC-003-1, lines operated between 100 kV and 200 kV in that 

state would not be covered by any federal or state vegetation management standard. 

B. FAC-003-1’s Scope 

If FAC-003-1 had applied to all of the transmission facilities impacted by tree 

contact during the October snowstorm, compliance with the Standard with respect to 

those lines may not have prevented the storm’s vegetation-caused transmission line 

outages. This is because: (a) the majority of outages were caused by trees that fell onto 

transmission lines from outside the utility’s right-of-way, and FAC-003-1 does not 

specifically address off-right-of-way vegetation management; and (b) FAC-003-1 does 

not dictate specific right-of-way management practices, including how utilities should 

manage on-right-of-way danger trees. 

First, FAC-003-1 does not specifically address management of vegetation located 

outside a utility’s right-of-way. Thus, even if the Standard had applied to all 

90

Two other lines that experienced outages during the October snowstorm are operated at over 200 kV, and

therefore subject to FAC‐003‐1, but those outages were not caused by vegetation contact.

91

On December 21, 2011, NERC filed with FERC a proposal to replace FAC‐003‐1 with a new standard, FAC‐003‐2.  

Among other things, FAC‐003‐2 would revise the Standard so that it would be applicable to all transmission lines

operated at or above 200 kV and any line that is an element of an Interconnection Reliability Operating Limit

(IROL) or a Western Electric Coordinating Council (WECC) Transfer Path.  N. Am. Elec. Reliability Corp., Petition,

Docket No. RM12‐4‐000 (filed Dec. 21, 2011).  However, this expanded applicability would not have significantly

increased the Standard’s impact on lines forced out of service by tree contact during the October snowstorm

because only eight of those 115 kV or 138 kV lines are IROL elements (none are WECC Transfer Paths).  Moreover,

the proposed FAC‐003‐2’s requirement that no vegetation come into contact with lines governed by the Standard

does not apply when the vegetation contact is caused by major storms.  This report does not offer any views on

proposed FAC‐003‐2, which is currently under review by the Commission.  

92

See, e.g., N.Y. Comp. Codes R. & Regs. Title. 16 §§ 84.2, 84.3; Cal. Gen. Order 95, Rule 35.

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

 

transmission lines impacted by vegetation during the October storm, it would not have 

addressed the condition — tall trees growing outside of utilities’ rights-of-way — that 

caused over half of all storm-related outages. One reason FAC-003-1 does not explicitly 

address off-right-of-way vegetation management is that land adjacent to rights-of-way is 

typically not owned by the utility, and state laws usually limit utilities’ ability to prune or 

remove trees on property they do not own. Although state laws differ, generally 

speaking, a utility may not remove a tree (including a danger tree) located outside of its 

right-of-way without the property owner’s consent.93 Moreover, obtaining permission to 

remove off-right-of-way trees can be complicated and difficult. 

When utilities and state agencies set policies and make decisions regarding removal 

of danger trees outside the right-of-way, they must consider a number of factors. 

Reliability of the transmission system, and, in particular, preserving the stability of the 

BPS, is a central concern. However, environmental issues, property rights, viewsheds, 

and cost also play an important role. In heavily forested regions like New England, even 

if possible, the reliability benefits of removing all danger trees from outside utilities’ 

rights-of-way often would not outweigh the costs of doing so.94 For example, Northeast 

Utilities provided staff with an estimate that there are some 800,000 danger trees along 

the edges of its rights-of-way, and that removing them would cost approximately $400 

million.95 Notwithstanding competing policy concerns, off-right-of-way tree fall-ins 

were the leading cause of transmission line outages during the October snowstorm, and, 

in general, some off-right-of-way danger trees can pose a threat to reliability. Therefore, 

staff makes a recommendation in Section IX that utilities should re-evaluate, and work 

to enhance, their off-right-of-way vegetation management. 

93

See, e.g., N.H. Rev. Stat. Ann. § 231:172(I) (electric utilities must obtain consent of the landowner to prune trees

outside of the right‐of‐way); see also Tree Trimming FAQs, PUBLIC SERVICE OF NEW HAMPSHIRE,

http://www.psnh.com/CustomerSupport/Home/Tree‐Trimming‐FAQs.aspx (explaining procedures for obtaining

consent of tree owners before performing trimming maintenance).  In some circumstances, if a utility provides notice

of its intent to remove a tree and the landowner does not object, the utility may proceed without specific permission.  

See, e.g., N.H. Rev. Stat. Ann. § 231:172(II)(b) (stating that the utility may perform the work without permission if the

tree owner does not request personal consultation after receiving notice).  In some states, there are expedited

procedures for obtaining permission to remove “hazard trees” — trees that present an imminent danger to

transmission lines because they are damaged or diseased.  See, e.g., Mass. Gen. Laws Ann. ch. 87 § 14(b), (c)

(permitting electric utilities to file hazard tree removal plans for approval by the tree warden to avoid otherwise

applicable restrictions on tree removal).

94

As ISO‐NE has stated, “[t]he political, social and environmental expectations placed on utilities in New England

prevent the clearing required to guarantee total system protection from falling trees.  In severe weather events

(hurricanes, micro bursts, tornadoes and ice storms) trees may fail and fall into lines.”  ISO‐NE,OPERATING PROCEDURE 3

Appendix C (2005).

95 Of course, the monetary and non‐monetary costs of danger tree removal must be weighed against, among other

things, the often high costs of transmission outages.

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Second, while FAC-003-1 does require utilities to maintain plans and procedures to 

address vegetation to meet its Clearance 1 requirements, and utilities have considerable 

flexibility in designing transmission vegetation management programs as long as utilities 

are compliant with the FAC-003-1 requirements, the Standard does not specifically 

dictate how utilities should manage danger trees that are outside of Clearance 1 but 

within the right-of-way. Thus, utilities may maintain vegetation clearances on less than 

the full right-of-way, which can increase the number of danger trees within the right-ofway.

96

FAC-003-1 does recognize that the American National Standard Institute’s (ANSI) 

Standard A300, which provides guidelines for integrated vegetation management on 

electric utility rights-of-way,97 is an industry best practice.98 ANSI A300 does not 

specifically prohibit growth of danger trees on a right-of-way, but it does explain that the 

“wire zone-border zone” vegetation management method, where the full right-of-way is 

managed in order to prevent the growth of danger trees, “is a proven method that 

ensures the reliability of electric supply lines.”99 The wire zone-border zone method 

allows very low-growing vegetation such as grasses and other groundcover species in the 

area under and immediately around transmission structures (the “wire zone”) and 

permits short-growing vegetation like shrubs and short trees from the outer edge of the 

wire zone to the edge of the utility’s full right-of-way (the “border zone”).100 The 

following drawing illustrates the wire zone-border zone concept. 

96 Staff notes that no registered entity has been charged with a violation of FAC‐003‐1 as the result of a healthy tree

falling onto (as opposed to growing into) a transmission line.   

97 Integrated vegetation management (IVM) is “[a] system of managing plant communities in which compatible and

incompatible vegetation is identified, action thresholds are considered, control methods are evaluated, and selected

control(s) are implemented to achieve a specific objective.”  ANSI A300, supra note 14 at 72.    

98 Reliability Standard FAC‐003‐1, at Requirement R1 n.1.

99

ANSI A300, supra note 14 at 75.2, Annex A.

100

ANSI A300, supra note 14; RANDALL H. MILLER, BEST MANAGEMENT PRACTICES: INTEGRATED VEGETATION MANAGEMENT 17

(2007) (companion publication to ANSI A300).  

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

Figure 16: Wire Zone‐Border Zone Illustration

Source: UVM Final Report, infra note 109 

FAC-003-1’s focus on maintaining clearances through a specific method like the 

recognized wire zone-border zone best practice reflects an emphasis on preventing 

vegetation from growing or swaying into conductors (or conductors swaying or sagging 

into vegetation) rather than vegetation breaking and falling into conductors, especially 

during severe storms.101 Thus, to minimize the damage caused by similar events in the 

future vegetation management requirements would need to include a requirement to 

address at least those danger trees growing within the right-of-way. 

 101 Indeed, the genesis of FAC‐003‐1 was the major blackout that occurred on August 14, 2003, which was caused in

significant part by unmanaged vegetation that, due to growth and line sag, contacted several 345 kV lines and

precipitated cascading outages throughout the eastern United States and Canada.  See U.S.‐CANADA POWER SYSTEM

OUTAGE TASK FORCE, supra note 12.  Proposed FAC‐003‐2 requires that Transmission Owners manage vegetation in

order to prevent any vegetation from making contact with transmission lines – including fall‐ins.  N. Am. Elec.

Reliability Corp., Petition, Docket No. RM12‐4‐000, at Proposed Standard FAC‐003‐2, R1, R2 (filed Dec. 21, 2011).  

However, as stated in note 91, the proposed standard would not apply to vegetation contact in “circumstances that

are beyond the control of a Transmission Owner,” including natural disasters such as “major storms as defined either

by the Transmission Owner or an applicable regulatory body . . . .”  Id., at R1 n.2.  As previously noted, this report

takes no position on proposed FAC‐003‐2.

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

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VIII. Outage Reporting Provides Limited Information

During and after the storm, two Reliability Standards – FAC-003-1 and EOP-004-1 

– required that entities report some information about their outages to either NERC or 

NPCC. However, those requirements, and the responses provided by most affected 

utilities, resulted in FERC and NERC initially receiving limited information about the 

event. Based on the findings in this Section, staff makes recommendations in Section IX 

for improved or enhanced reporting of certain outage information.102

Standard FAC-003-1 requires Transmission Owners to report on a quarterly basis 

to Regional Entities such as NPCC sustained vegetation-caused outages on lines subject 

to that Standard,103 and NPCC guidance also instructs transmission owners to report 

vegetation-caused outages on any BPS elements operated under 200 kV.104 However, 

outages caused by off-right-of-way tree contacts during natural disasters, including 

major storms, do not have to be reported under FAC-003-1.105 While NERC obtains 

certain data about outages through other reporting mechanisms, there are no data 

reporting requirements in place that mandate the reporting of all the transmission 

facility outages that occurred in the October storm. Nor were all such outages, in fact, 

reported to NERC. Thus, utilities were not required by FAC-003-1 to submit 

information on the October storm’s BPS element outages caused by off-right-of-way tree 

fall-ins. 

Staff gathered substantial information about these outages during the inquiry, but 

is concerned that information about off-right-of-way tree fall-ins during other weather 

102 This report’s findings and recommendations regarding reporting address only issues related to reporting outage

information to FERC, NERC, or the Department of Energy (DOE).  We do not address issues related to reporting

distribution facility or customer outages to state regulators.  However, staff notes that there have been calls to

improve the consistency of distribution facility outage reporting.  See MASSACHUSETTS INSTITUTE OF TECHNOLOGY, The

Future of the Electric Grid, 9 (2011), available at http://web.mit.edu/mitei/research/studies/the‐electric‐grid‐

2011.shtml (“Most outages occur within distribution systems, but only 35 U.S. states require utilities to report data on

the impact of all outages on consumers, and reporting standards and practices differ.  It is accordingly impossible to

make comprehensive comparisons across space or over time.”).   

103 Reliability Standard FAC‐003‐1, at Requirement R3.   

104

NPCC, COMPLIANCE GUIDANCE STATEMENT ON REPORTING OF TRANSMISSION OUTAGE RELATED TO VEGETATION CONTACT (rev. Oct. 3,

2008), available at

https://www.npcc.org/Compliance/Compliance%20Guidance%20Statements/Forms/Public%20List.aspx.

105 Reliability Standard FAC‐003‐1, at Requirement R3.2.   

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 on the affected systems.108

 

events may not be reported. The weather exception prevents regulators from obtaining a 

key source of information about the extent and severity of these types of outages. Better 

information would allow policymakers to understand the scope and impacts of weathercaused off-right-of-way tree fall-ins, and to assess whether regulations or guidance 

should be formulated to address those outages. 

Second, staff finds that, during and after the October snowstorm, affected entities 

did not always provide thorough information in the disturbance reports they were 

required to file with NERC under Reliability Standard EOP-004-1. That Standard 

mandates that registered entities submit completed disturbance report forms — either 

the DOE Electric Emergency Incident and Disturbance Report (Form OE-417) or NERC’s 

Interconnection Reliability Operating Limit and Preliminary Disturbance Report — after 

certain events, including those where there is significant loss of load.106 Initial Form 

OE-417s must be submitted to DOE and NERC within an hour of the disruption, and, at 

the time of the October storm, final reports providing complete disruption information 

were required to be filed within 48 hours of the event.107 However, the majority of the 

OE-417 forms submitted by utilities during and after the October snowstorm did not 

provide enough information to allow for a useful initial analysis of the event. For 

example, many final reports did not include full narrative descriptions of events, or 

include the voltage of transmission lines that experienced outages. This lack of 

thoroughness, particularly in the final reports, made it difficult for FERC and NERC staff 

to ascertain the exact nature of the impact of the storm

106 Reliability Standard EOP‐004‐1 (Disturbance Reporting), at Requirement R3.

107 Id., Attachment 2.  As of January 1, 2012, the forty‐eight‐hour reporting requirement for final reports was

extended to seventy‐two hours.

108 The inconsistency and incompleteness of information regarding BPS outages was also noted in the MIT report on

the future of the electric grid:  “At the bulk power level, data on major disturbances and unusual occurrences have

been reported to the U.S. Department of Energy (DOE) since the 1970s and to the North American Electric Reliability

Corporation (NERC), which has responsibility for the reliability of the bulk power system, since 1984.  However, these

data are not consistent, complete, or necessarily accurate, and they cannot reliably be used to assess changes in the

reliability of the bulk power system over time.”  See MASSACHUSETTS INSTITUTE OF TECHNOLOGY, supra note 102, at 9.

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

IX. Recommendations

The October 2011 Nor’easter was a rare storm that, due to a number of 

circumstances — record amounts of heavy wet snow, trees that had not lost most of their 

leaves, and unusually saturated ground — had severe and widespread impacts on the 

electricity infrastructure in the Northeast. Staff recognizes the unusual aspects of this 

weather event. Nonetheless, based on information gathered and findings made during 

the inquiry, staff concludes there are a number of “lessons learned” that, if implemented, 

could improve reliability during future storms and similar weather events. Accordingly, 

staff makes the following recommendations with regard to transmission facilities. 

• Vegetation Management Recommendations109

By far, the leading cause of transmission line outages during the October 

snowstorm was trees or tree branches falling onto power lines from outside and inside 

utilities’ rights-of-way.110 Staff therefore recommends that utilities take the following 

targeted steps to enhance their management of danger trees both on and off their rightsof-way in order to reduce these types of outages.111

1. Where Appropriate, Utilities Should Take Targeted Steps to Address Off‐Right‐of‐

Way Danger Trees

As noted above, off-right-of-way tree fall-ins accounted for about half of the storm’s 

transmission line outages, and nearly 75% of all confirmed vegetation-caused outages. 

Off-right-of-way danger trees are a particular threat to reliability in New England, where 

there may be hundreds of danger trees along one span of a transmission line. Staff 

 109

In response to the 2003 Blackout, FERC commissioned a separate vegetation management report to support the

federal investigation into that event.  The result was the Utility Vegetation Management Final Report, completed by

CN Utility Consulting, LLC and published in 2004.  STEPHEN R. CIESLEWICZ & ROBERT R. NOVEMBRI, UTILITY VEGETATION

MANAGEMENT FINAL REPORT (March 2004) [hereinafter “UVM Final Report”], available at

http://www.ferc.gov/industries/electric/indus‐act/reliability/blackout/uvm‐final‐report.pdf. The recommendations

related to vegetation management in this report are similar to several of the vegetation management

recommendations made in the UVM Final Report.    

110

In fact, the majority of vegetation‐related outages in the United States are caused by trees or portions of trees

falling into lines from distances outside of normal clearing zones (i.e., Clearance 1 or Clearance 2 distances).  See

NERC, Vegetation Management Reports, http://www.nerc.com/page.php?cid=3|26.

111 Staff recognizes the sensitivity of vegetation management issues and the difficulty of expanding rights‐of‐way and

more effectively maintaining them.  However, these difficulties must be balanced against the reliability and safety

benefits of improved right‐of‐way management.

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

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recognizes that in most cases utilities are not free to unilaterally remove off-right-of-way 

trees, that the process for obtaining permission to do so is frequently difficult and costly, 

and that tree removal often faces significant landowner and public opposition. 

Moreover, the costs of indiscriminate, widespread removal of off-right-of-way danger 

trees may outweigh the reliability benefits of doing so. 

Taking all these factors into consideration, staff recommends that, where 

appropriate, utilities follow a targeted approach to enhancing their off-right-of-way 

danger tree management, focusing on protecting lines operated at 200 kV and above, 

and lower-voltage transmission lines that, if lost, would negatively impact the overall 

reliability of the Bulk Electric System. Utilities should analyze their transmission 

systems in order to identify danger trees — particularly those species of trees that have a 

tendency to fail — that could impact critical transmission lines. After performing this 

analysis, utilities should work with affected property owners, state regulators, and local 

communities to develop a strategy for managing those trees that pose the greatest threat 

to those facilities. In addition, if state laws or policies significantly impact utilities’ 

ability to manage off-right-of-way danger trees that could impact these critical facilities, 

utilities should work with stakeholders and state and local governments to develop 

solutions that reduce risk to those lines. 

2. Utilities Should Employ Recognized Best Practices in Managing Rights‐of‐Way

Where Feasible

Staff found in Section V.A that roughly 25% of the confirmed vegetation-related 

transmission line outages during the October event were caused by trees that fell into 

transmission lines from inside a utility’s full right-of-way. These on-right-of-way trees 

were all located outside the utility’s maintained right-of-way. Based on this finding, staff 

recommends that, where possible and practical, utilities implement the industry best 

practice of ensuring that danger trees are not present within their full rights-of-way.112 

In particular, to the extent a utility manages vegetation only on maintained rights-of-way 

rather than full rights-of-way, it should work toward reclaiming the full right-of-way 

width where feasible.113

 112 Staff recognizes that there are a number of ways to achieve this result.  The wire zone‐border zone right‐of‐

way maintenance method, discussed in Section VI, is recognized as highly effective in protecting against on‐right‐

of‐way tree contact and generally maintaining reliability.  Selection of the most appropriate maintenance method

for any given right‐of‐way should be made by qualified vegetation management personnel.

113 Maintaining narrower areas within a full right‐of‐way is not an uncommon practice in the industry and occurs

for a variety of reasons, some of which are outside the control of the utility.  However, it is not a best practice.

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

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Two key components of reclaiming and maintaining full rights-of-way are (1) 

knowing the exact boundaries of that area and (2) being able to identify those boundaries 

in the field. This is not always easy, given that traditional markers (such as wooden 

stakes or iron plates) can deteriorate or get lost during four-plus year vegetation 

management cycles. However, technologies such as Light Detection and Ranging 

(LiDAR) and Global Positioning Systems (GPS) can help utilities accurately and more 

permanently identify right-of-way boundaries on the ground. Staff recommends that, 

over time, utilities work toward employing technologies that will allow them to track the 

exact boundaries of all of their transmission rights-of-way and locate those boundaries in 

the field. 

Staff recognizes there are a number of circumstances where utilities may be unable 

to completely prevent the presence of danger trees within full, or even maintained, 

rights-of-way through implementation of the wire zone-border zone management or 

other, similar techniques, and that utilities have been, and must continue to be mindful, 

of these circumstances.114 For example, utilities may be prohibited by state law from 

removing certain vegetation on their rights-of-way in environmentally sensitive areas, or 

may be required to maintain on-right-of-way vegetation in order to partially shield 

power lines from view.115 Removal of danger trees also may not be possible where the 

easement establishing the utility’s right-of-way explicitly limits, or does not clearly 

permit, vegetation management in the full easement area. Even where the easement 

gives a utility rights to manage vegetation across the entire right-of-way, past practices 

(for example, years of permitting landowners to grow tall trees inside the right-of-way), 

landowner objections, or public sentiment opposing the maintenance of wide rights-ofway may make it difficult to employ the wire zone-border zone method or otherwise to 

remove danger trees. Staff also recognizes that reclaiming rights-of-way that are not 

currently being fully managed can be expensive, time consuming, and difficult. 

However, staff finds that consistently maintaining the full right-of-way would reduce the 

number of danger trees near transmission lines.116

114

See, e.g., CIESLEWICZ & NOVEMBRI,supra note 109, at 21 (recognizing that there are locations where

implementing the wire zone‐border zone model is not practical); MILLER, supra note 100, at 18‐19 (same).

115

See generally, CIESLEWICZ & NOVEMBRI, supra note 109, at 15‐16.

116 Staff recognizes that, in some instances, removing certain tall‐growing trees from the interior edge of the full‐

right‐of‐way may expose weaker, top‐heavy danger trees on the exterior edge, posing more of a risk of a tree

falling into the transmission facilities.

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

Utilities should, of course, take these circumstances into account when evaluating 

their right-of-way management policies to specifically address danger trees. Staff 

recommends that utilities: (a) identify the areas where elimination of danger trees inside 

the full right-of-way is possible given site-specific circumstances and (b) evaluate 

whether danger tree removal/right-of-way reclamation would increase reliability and be 

feasible. Once rights-of-way that are appropriate for removing danger trees are 

identified, utilities should prioritize their efforts, focusing first on rights-of-way 

surrounding lines that are rated at or above 200 kV, and lower-voltage transmission 

lines that, if lost, would negatively impact the overall reliability of the Bulk Electric 

System. 

In sum, in order to improve reliability during future major storms, staff 

recommends that, where possible, utilities develop and implement plans to ensure that 

danger trees are not located within their full rights-of-way.117 

3. Utilities Should Lay the Foundation for Effective Vegetation Management When

Establishing New Rights‐of‐Way

Preventing fall-ins from both inside and outside the right-of-way is easier if utilities 

consider vegetation management needs when siting new transmission lines and 

acquiring new easements. Therefore, staff recommends that utilities carefully assess 

vegetation and growth rates in the area of planned lines in order to establish the 

appropriate right-of-way width. For example, if native trees have a mature height of 100 

feet, the easement should cover an area wide enough to ensure that existing and future 

trees outside of the right-of-way will not fall into the facilities.118

In addition, utilities should ensure that easement documents protect the utility’s 

ability to ensure safe and reliable transmission of electricity. New easements should 

clearly provide the utility with rights to manage the full easement in order to prevent the 

presence of danger trees inside the right-of-way. In addition and where possible, new 

easements should give the utility the ability to remove danger trees outside of the rightof-way. 

 117

To be clear, preventing the presence of danger trees within the right‐of‐way does not mean that full rights‐of‐

way need to be (or should be) clear‐cut.  This recommendation is focused on ensuring that, where feasible,

danger trees – those trees that could fall into a transmission line or structure – are not present within rights‐of‐

way because they can threaten reliability.  Many types of trees growing within rights‐of‐way do not constitute

danger trees.

118

See CIESLEWICZ & NOVEMBRI, supra note 109, at 71.

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

• Other Recommendations 

4. Utilities Should Evaluate and, As Needed, Enhance Their Storm Preparedness and

Response Plans

As explained in Section III, the October snowstorm exceeded forecasts, and many 

utilities scrambled — often at the last minute — to assemble adequate response 

personnel, especially field crews. Although these manpower and related issues did not 

significantly hinder restoration of transmission line outages or unduly prolong 

transmission-caused customer outages, the event revealed potential areas of 

improvement in preparation for future storms. Thus, staff recommends that utilities 

evaluate their severe storm preparation and response plans to ensure they are flexible 

and scalable enough to quickly respond to events that are more severe than predicted. 

For example, utilities should: (a) clearly define how and when they will request outside 

assistance, through mutual aid or outside contractors; (b) be prepared for regional 

mutual assistance crews to be unavailable when a weather event is predicted to impact 

many states, either by requesting mutual aid from other regions early on or retaining 

additional local contractors to make up for the lack of immediately available mutual 

assistance; (c) have a policy in place regarding if, when, and where pre-staging will 

occur; (d) have the ability to, and procedures regarding, reservation of equipment, such 

as helicopters and infrared cameras, in advance of major storms in order to ensure 

prompt assessment of transmission system damage; and (e) in regions where extreme 

weather events occur, and especially where they are becoming more common, retain 

experienced weather personnel with the responsibility to predict likely impacts of 

weather events, taking into account service-territory-specific conditions. 

5. Utilities Should Report All Vegetation‐Caused BES Facility Outages to NERC

As discussed in Section VIII, even though off-right-of-way tree contact during 

severe storms is a frequent cause of transmission line outages, FAC-003-1 does not 

require utilities to report those outages to Regional Entities or NERC. Moreover, the 

Standard does not require the reporting of vegetation-caused sustained outages on BES 

transmission lines not subject to FAC-003-1 (i.e., those operated at voltages below 200 

kV or lower-voltage lines not designated as critical by a Regional Entity). To ensure that 

regulators have sufficient information to allow them to make informed policy decisions 

about these types of outages, staff recommends that all tree contact-caused BES facility 

outages be reported to NERC. 

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Report on Transmission Facility Outages during the Northeast Snowstorm of October 29–30, 2011 

Causes and Recommendations 

 51

6. Disturbance Reports Should Be Clear and Complete

Section VIII finds that although a number of entities were required by Reliability 

Standard EOP-004-1 to file preliminary and final disturbance reports related to the 

October snowstorm outages, many of the filed forms were not completed thoroughly. 

This lack of thoroughness made it difficult to quickly ascertain the impact of the storm 

on the affected systems. Staff recommends that, where possible, all entities required to 

file disturbance reports under EOP-004-1 promptly provide thorough, descriptive, highquality information in the initial reports as it becomes available to them. With regard to 

the final disturbance reports, utilities should ensure their responses are comprehensive, 

providing all the relevant information in their possession.