Want underground wiring? Move to the city

The pole behind my house
CC BY 2.0 The pole behind my house/ Lloyd Alter

In California, many people are saying that all the wiring should be underground because of fire risk. It won't happen.

Many years ago some Dutch architects were visiting our home and saw this mess of telephone, cable and internet wiring in our backyard (the electricity actually comes in from the front) and asked, 'Why isn't it underground like it all is where they live?' I explained that even in the residential areas of the city (I live in a 100-year-old streetcar suburb), the utilities and politicians say it is way too expensive to retrofit, and they only do underground for new construction or in very high density areas.

In California, there are many fires that have been either started or expanded because of above-ground electrical distribution, and many people are demanding that the wiring be undergrounded (note to editor, it has been verbed). The problem is that the cost of underground wiring can only be justified if it is amortized over a lot of people and a lot of years. It only works at reasonable densities.

Most of the people in most danger of fire in California live in the Wildland-Urban Interface (WUI). According to a recent study,

The WUI in the United States grew rapidly from 1990 to 2010 in terms of both number of new houses (from 30.8 to 43.4 million; 41% growth) and land area (from 581,000 to 770,000 km2; 33% growth), making it the fastest-growing land use type in the conterminous United States. The vast majority of new WUI areas were the result of new housing (97%), not related to an increase in wildland vegetation. Within the perimeter of recent wildfires (1990–2015), there were 286,000 houses in 2010, compared with 177,000 in 1990. Furthermore, WUI growth often results in more wildfire ignitions, putting more lives and houses at risk. Wildfire problems will not abate if recent housing growth trends continue.

It is a classic catch-22 situation; more people living in the WUI means more wires to more houses and more fires. But undergrounding is almost impossible, firstly because of cost. According to SFGate,

...it costs about $1.16 million per mile to install underground distribution lines. In cities, that number is much higher; work in San Jose cost $4.6 million per mile. Overhead lines cost about $448,800 per mile in comparison.

Paradise, California, February 11, 2019 © Justin Sullivan/Getty Images/ Paradise, California, February 11, 2019

In the rebuilding of Paradise, destroyed in an earlier fire, PG&E is putting all the wiring underground. But that is easier because everything has to be done from scratch. They note:

Paradise is well suited for the underground build as PG&E needs to replace 74 miles of damaged natural gas lines. This provides opportunities for joint trenching for both electric and gas infrastructure.

But even in Paradise, they are stringing temporary wiring above grade because it takes so long to put in all the underground services. According to the Desert Sun,

PG&E, the state's largest utility, maintains approximately 81,000 miles of overhead distribution lines and approximately 26,000 miles of underground distribution lines. It also has about 18,000 miles of larger transmission lines, the majority of which are overhead lines. At a cost of $3 million per mile, undergrounding 81,000 miles of distribution lines would cost $243 billion. PG&E has 16 million customers; distributing that expense equally would amount to a bill of more than $15,000 per account.

But the vast majority of PG&E customers don't live in the WUI; they live in cities and suburbs. So the cost of undergrounding wires for the people most in danger of fire would be a massive subsidy by urban and suburban customers for the exurban ones at most risk. Are they going to be willing to pay that?

There are other problems with undergrounding. The wires are heavier since they can't cool in the air, so it is a lot more metal. Because there is more metal, "large charging currents arise due to the higher capacitance from underground power lines and thus limits how long an AC line can be." They are not as resistant to earthquakes; according to Wikipedia,

Underground cables are more subject to damage by ground movement. The 2011 Christchurch earthquake in New Zealand caused damage to 360 kilometres (220 mi) of high voltage underground cables and subsequently cut power to large parts of Christchurch city, whereas only a few kilometres of overhead lines were damaged, largely due to pole foundations being compromised by liquefaction.

But it is mainly about the money and time.

There are other responses, similar to what happened in Australia after dozens of people were killed in brushfires. People now build houses out of totally noncombustible materials, have giant cisterns to store water, and are often totally off-grid with solar panels and big batteries. A lot of this was insurance-driven.


But those Australian houses are expensive, and so is insurance. I suspect Susie Cagle is right; It will be the rich who get the big steel houses in the woods, with the Powerwalls and solar shingles that charge up their Teslas. Everyone else will be on their own.

Installing underground electrical wiring in RomeInstalling underground electrical wiring in Rome/ Lloyd Alter/CC BY 2.0

In Rome, every time you put a shovel in the ground, it is an archeological dig. It is expensive, and so is the electricity. But people live at high densities, in small apartments, have small fridges and rarely have air conditioning. The city is not exactly a model of well-functioning public services (there are better examples but I had a picture) but the fact remains that almost everything we consume is a function of the density we build at.

Cheap power distribution, along with subsidized roads and subsidized fuel and low-density exurban housing made of cheap stick-frame wood construction and cheap plastic building materials that all burn in seconds is what made all this possible. To make it stop, we have to change all of the above.

Want underground wiring? Move to the city
In California, many people are saying that all the wiring should be underground because of fire risk. It won't happen.

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