Fight over role of tree-trimming in Austin ice outages highlights risks to nation’s grid

Extended power outages that gripped Austin last week are raising questions about trees and urban power infrastructure — and leaving the city manager fighting for his political life. 

Unlike the winter storm crisis that rocked Texas in 2021, the recent outages weren’t related to the grid. They stemmed from untrimmed limbs from the city’s canopy of heirloom oaks falling on power lines, leaving hundreds of thousands without electricity. 

The fate of Austin’s tree canopy — and its tangled relationship with the city power supply —points to a more significant national problem. As extreme weather events proliferate, they interact in complex ways with the urban forests that many cities now pride themselves on — and are turning to as a means of adaptation to climate change. 

Trees can help block the dangerous summer sun, break the power of storm winds and lessen the flood-producing impacts of a deluge. But if improperly trimmed, or in the face of sufficiently strong weather, they can turn into missiles, expanding a storm’s destructive force. 

Last month’s atmospheric rivers in California brought down thousands of trees, smashing homes, cars and power lines. In the state capital of Sacramento — which, like its fellow capital city of Austin, has long boasted of its lush urban canopy — 1,000 trees came down last month, blocking roads, destroying houses and cutting off power. 

This week, Austin’s urban forest became the focus of a rancorous debate over the city grid’s recent failures — part of a proxy war in the long-running battle over the city’s future. 

The fight comes as an enormous new influx of cash is about to come raining down on the urban forests of cities large and small. The Inflation Reduction Act, which President Biden signed into law last year, includes $1.5 billion for urban forestry — money that will “reshape tree canopies in cities across America,” as Jad Daley, president of nonprofit American Forests, told Pew Charitable Trusts. 

That battle pits Austin’s powerful southern and western neighborhoods — long a force against multifamily development and cutbacks to the city canopy — against the city utility and the growing disruption from climate change, which is straining grids nationwide. 

Austin’s urban canopy of live oaks, sycamores and Ashe junipers covers 30 percent of the city in a blanket of more than 30 million trees, the city told The Hill. 

These trees pay their way, according to the city. They lock down $242 million dollars’ worth of carbon, cut residential energy costs by nearly $19 million, reduce stormwater use and represent nearly $15 billion in insurable value.

The damage from the storm was sufficiently bad that the city still doesn’t know how many of these trees were damaged, Austin officials told The Hill. 

Instead, they’re estimating it in terms of loads of debris hauled off — 58,000 cubic yards. 

That’s the equivalent of a cube of stacked trunks and branches a hundred feet in every direction. 

In Austin, city councilors are concerned that the state of the city’s canopy proved such a liability, particularly given the amount of money that has poured into it. The council doubled funding to Austin Energy, the principal city utility, for causes like tree trimming, Councilor Vanessa Fuentes told CBS Austin. “So we have a lot of questions to ask.”  

City manager on thin ice

On Tuesday, Spencer Cronk — who as Austin city manager is the ultimate boss of Austin Energy — offered an apology before a city council openly reconsidering his employment. 

“I feel like we’ve become a little desensitized to the word ‘unprecedented’ over the past few years, but this storm truly was historic in so many ways,” Cronk said. 

“For this disaster, we have already learned many lessons and we will do better,” he added. “Once again, I offer my heartfelt apologies for any shortcomings in our response.” 

Cronk’s Tuesday apology followed a curt statement on Monday by Austin Mayor Kirk Watson (D), who announced that the city manager was on thin ice and that the City Council would “take up an emergency item” reevaluating the conditions of Cronk’s employment. 

“To all our Austin citizens who are furious about the ongoing power outage, you’re right. There must be accountability,” Watson tweeted. 

“Our trees are vulnerable after the winter storm and may have broken limbs high up in their branches that cannot be seen easily,” Juan Ortiz, city emergency manager, said in a statement. “With strong wind in the forecast, additional tree limbs may fall, potentially creating further damage and causing new outages. That’s why we’re asking people to be extra attentive today and to bear with us while we address new challenges as they arise.”  

Watson cited, in particular, the “lack of clear, timely and accurate communication” that left Austin residents shivering in their homes, unsure when the power would be turned back on. While the city had restored power to nearly 98 percent of customers by the time of Cronk’s apology, that still left more than 10,000 households without power in freezing conditions — as another winter storm rolled in midweek, breaking against the city’s already damaged canopy. 

As the city councilors deliberated over Cronk’s continued employment, about 400 households served by Austin Energy were without power as of Friday morning, according to grid tracking site PowerOutage.us.  

While the mayor and council answer to the Austin public, Watson noted, “the City Manager answers to us.” 

Firing the city manager would cost the city a year of severance at his current pay of $388,000, KXAN reported. (KXAN News, like The Hill, is a member of Nexstar Media.) 

But the backlog of untrimmed trees that contributed to the current crisis long preceded the current manager, experts said. 

A problem rooted in past storms

The severity of the grid damage caused by trees in this storm can be traced to the last storm of similar ferocity — the devastating winter storm of 2007, Michael Webber, a professor of mechanical engineering at the University of Texas, told public radio station KUT. 

Blackouts in that storm spawned an acrimonious, long-running battle between Austin Energy — which sought to cut back the city’s canopy to prevent future outages — and the city’s wealthy neighborhoods. 

“Very powerful people who are rich and are in the neighborhoods with the beautiful trees were complaining,” he told KUT’s Mose Buchele.  “They didn’t want their pretty trees in their yards touched by the city.” 

Anger from neighborhood residents at what they saw as overly aggressive tree-trimming — one association was radicalized by the clearing of 200 trees in a single block — led Austin Energy to take a more lenient tack. 

The city utility changed policies to allow slow-growing tree limbs to be within 4 feet of power lines — less than half of the previous limit — and gave property owners wide leeway to push back on or “refuse” city plans, KUT reported. 

By 2019, however, the utility realized it had a problem. “At the end of the day, if we don’t trim the trees, we could find ourselves in a very precarious situation,” then-Austin Energy Chief Operating Officer Charles Dickerson told regulators. 

“If we don’t trim with this level of prudence, we can wind up with more outages and possibly fires,” he said at the time. 

Austin Energy officials argued at a City Council meeting on Thursday night that the tree-trimming policy wasn’t the principal problem, according to KXAN. 

In many areas, outages had taken place where trees had been properly trimmed or treated, Elton Richards, the utility’s vice president of field operations, told the council. 
 
Many outages had been caused by high branches — outside the areas that were supposed to be trimmed — calving off of trees, as well as entire trees coming down. 
 
Richards also blamed what he characterized as overly restrictive council tree-trimming rules for contributing to a continuing backlog. 

Climate change stresses grid made for milder conditions

But tree damage to power lines — in Austin and California — was just a symptom of far larger problems, Payman Dehghanian, a professor of electrical engineering at George Washington University, told The Hill. 

The grid in California, Texas and the U.S. is susceptible to damage from trees for the same reason it is vulnerable in general, Dehghanian said. 

The grid “was designed to meet the energy demands of a much milder climate,” he said. 

Trees and limbs falling may have been the acute cause of the complex failures that led to outages like the one in Austin, but they impacted an electric system already highly stressed by the winter weather. 

Extreme cold or heat hits the grid from every direction, spiking demand, cutting supply and mucking up the connections in between. 

When it is too hot or cold, generators don’t work as well, households and businesses demand more energy for heating and cooling — and the resistance in powerlines increases, reducing the amount of current they can carry. 

To make matters worse, as electric load overwhelms the lines, they begin to sag toward the ground — raising the risk of summer fires, or the winter risk that branches or collecting ice will drag them down. 

These small failures create additional failures throughout the grid, as substations blow out, leaving entire neighborhoods in the dark. 

As Dehghanian explained it, the big problem the grid faces — which ties into everything from how city planners handle tree trimming to the kind of smart meters on home thermostats — is simple to state but fiendish to solve: It evolved in an environment where events like Austin’s ice storm were “high impact, low probability.” 

For a grid like that, only a small amount of redundancy is essential, Dehghanian said — what managers call “n minus one,” or the ability to stay online when one key element goes out. 

With the prospect of extreme weather events — hurricanes, floods, ice storms — regularly knocking out power across entire cities, he said this level is no longer sufficient.

“There is no single point of failure,” he said. “We are talking about a city getting out of electricity.” 

While n minus one might have been sufficient “decades ago,” it no longer is, he added. 

Building in more redundancy — getting to n minus three or four — requires rethinking the grid at every level. Every additional point of failure a system can survive requires an exponential increase in complexity, and the infrastructure costs can be enormous. 

For example, some have called for burying Austin’s power lines underground, where falling tree limbs can’t damage them. 

But at a cost of about $1 million a mile, such a step would come with “the extraordinary increase in cost,” Peter Lake, head of the state Public Utility Commission, told KXAN. 

“When we have ice on trees and branches are falling, if the lines are underground, then outages are less of an issue,” Lake said. “ 

The downside, however, is “the extraordinary increase in cost” — lines can cost $1 million-plus per mile — and the fact that routine maintenance on such lines requires digging them back up, he added. 

But these are the kinds of investments we have to get more comfortable with, Deghanian said. Every additional bit of redundancy means new power corridors, which means a complex web of new transformers, Deghanian said. “So there are a lot of complexities in that respect.”