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hwrnmnbsolNow that Hurricane Irene has passed, and homes and businesses on the Eastern seaboard have seen their utility service restored, persons living and working along the Atlantic coast are able to heave a sigh of relief. But with the remnants of Lee churning its way through the Deep South, Katia looming with at least some chance of making an impact, and the rest of the storm season still ahead of us, plenty of questions remain regarding what America should do, going forwards, regarding hurricane preparedness.
One of the most pressing questions relates to the question of whether utilities should be buried as opposed to strung overhead. Certainly burying lines costs more than the alternative – perhaps as much as an order of magnitude greater – but do underground utilities decrease the chances of outages during storms? If so, is it worth the premium to bury services in the first place? At what point does it become worthwhile to spend money to tear out perfectly usable lines and bury them?
To answer this question, we first must ask: what possessed us to run our water, gas, and drain lines overhead on poles in the first place?
The concept of centralized utility systems was invented by the Romans. The aqueducts developed by that ancient empire were the first systems capable of carrying potable water for hundreds of miles. These systems were invented long before powered pumping systems were devised, and hence had to be able to deliver water solely by the force of gravity. For this reason, aqueducts had to start out running high overhead, and then gently sloped down as they reached the terminus of the water supply network. The graceful arches of these Roman constructions can still be seen in parts of Europe.
The basics of Roman technology remained essentially unchanged until the advent of industrial power, and the invention of high-capacity water pumps. Initially powered by water wheels, and then steam, the first 'lift stations' provided pumping head -- but water system engineers continued to employ the Roman practice of distributing water overhead. Even when electric motors became the chief means of developing power for industrial use, the precedent set by the ancient Roman engineers remained the law of the land.
Over time, in the interest of saving costs, the gracefully arched aqueduct structures of the Romans were supplanted by cheaper and simpler infrastructure. The practice of using creosote-impregnated utility poles began in London in the 1830's, with pipes made of lead, clay or even wood. As portable pumps for fire-fighting were devised, fire hydrants were devised that drape down from the overhead lines, allowing convenient connection points for firefighters and marking-posts for dogs, provided they could jump high enough.
As new utility services were devised, it was deemed convenient to simply suspend them from the overhead poles already in existence. Natural gas, for instance, distributes overhead to can-type pressure regulators mounted on poles; in America, these regulate gas pressure down to 4 ounces or five pound service before entering buildings. Sanitary sewer and storm sewer lines are pumped up via sump pumps and flow in overhead cast iron lines to treatment stations; this practice became commonplace after numerous failures in gravity drainage owing to root intrusion and seismic breakage in underground lines. In the modern age, millions of Americans work, play and live their lives while rarely giving a thought to the water, effluent and gas whizzing overhead.
Unfortunately, the model of overhead utility services was devised by Empires which, by and large, were not located in areas prone to hurricanes, tornadoes, blizzards or other forms of extreme weather that can generate high winds. Lines run on poles above the ground, as it turns out, are quite susceptible to high winds, not to mention freezing conditions and weathering. Data from Hurricane Irene illustrates this point nicely; the media reported extensively on the millions of homes left without running water because trees fell across mains and shattered pipe, and who can forget the images of broken sewer pipes spraying nauseating effluent all across New Jersey?
The question, therefore, is whether a paradigm shift is warranted regarding the optimal configuration of utilities. Should America take another look at the buried approach?
The advantages of burying utility services are easy to see. Certainly a pipe located several feet below the ground will not be exposed to damage from high winds, although large enough fallen trees may still cause damage as their deeply-dug root systems uproot destructively. Additionally, a pipe below ground is less likely to be subject to freezing, is harder to steal or vandalize, and will be well-supported by the bedding of the trench in which it is run.
There are also operational advantages to running sewer systems underground. To the extent it is possible, employing gravity to remove wastewater is preferable to relying upon a powered system to eject it. The sump pumps can fail, and when this happens a building has no way to reject rainwater or sewage. However, if these systems could be configured so as to drain entirely into a gravity-run subsurface drainage system, this vulnerability could be eliminated.
However, there are many disadvantages to this approach. Cost is of course a significant consideration. Running sanitary, storm, gas and water systems under the ground will require the displacement of large amounts of earth. It will demand close and careful coordination between these systems and other things which may already be in the ground, such as buried power lines. Much of these lines will certainly require the excavation of large amounts of hardscape as well as grass and plantings; few citizens will appreciate the tearing up of roadway infrastructure to accommodate the burial of services that they rarely think about to begin with.
Additionally, there are other operational hazards to buried utility services. As observed previously, there are risks of buried line breakage associated with seismic events, tree roots, uneven soil density, lines buried under heavy traffic roadways and soil corrosion. When a buried line breaks, spotting the break's precise location can be difficult, whereas this is trivial for overhead services. Repairs can also be difficult and costly, requiring significant excavation and temporary pumping along with the tasks of material replacement.
There may even be hazards to life and limb. Buried high pressure natural gas has the potential to explode in a destructive manner that overhead lines could never expect to see. Broken sanitary sewer lines could seep waste into the water table for many years without being detected. Likewise, spot leaks in buried potable water lines could allow contaminated soil to foul water and harm people long before the problem is noticed.
We therefore conclude that while there may be many reasons why burying utility services appears attractive, at least at the first blush, there are at least equally as many reasons to disincentivize this approach. Hurricanes and other severe storms, while certainly damaging and frightening to the general public, are also rare enough that they typically impact only a relatively small number of people in any given year. The public should not rush to demand change to engineering principles that have been established for thousands of years based solely on a new idea's apparent face value.
We recommend that for the time being, water, sewer and gas utilities should remain mounted overhead in their current configuration. This conservative approach has served the western world well for centuries, and until such time as costs come down for buried work, overhead utility distribution should remain the model for American infrastructure. Services buried below the ground may well be 'out of sight, out of mind', but given the inherent risks, this approach should also be judged out of bounds.
One of the most pressing questions relates to the question of whether utilities should be buried as opposed to strung overhead. Certainly burying lines costs more than the alternative – perhaps as much as an order of magnitude greater – but do underground utilities decrease the chances of outages during storms? If so, is it worth the premium to bury services in the first place? At what point does it become worthwhile to spend money to tear out perfectly usable lines and bury them?
To answer this question, we first must ask: what possessed us to run our water, gas, and drain lines overhead on poles in the first place?
The concept of centralized utility systems was invented by the Romans. The aqueducts developed by that ancient empire were the first systems capable of carrying potable water for hundreds of miles. These systems were invented long before powered pumping systems were devised, and hence had to be able to deliver water solely by the force of gravity. For this reason, aqueducts had to start out running high overhead, and then gently sloped down as they reached the terminus of the water supply network. The graceful arches of these Roman constructions can still be seen in parts of Europe.
The basics of Roman technology remained essentially unchanged until the advent of industrial power, and the invention of high-capacity water pumps. Initially powered by water wheels, and then steam, the first 'lift stations' provided pumping head -- but water system engineers continued to employ the Roman practice of distributing water overhead. Even when electric motors became the chief means of developing power for industrial use, the precedent set by the ancient Roman engineers remained the law of the land.
Over time, in the interest of saving costs, the gracefully arched aqueduct structures of the Romans were supplanted by cheaper and simpler infrastructure. The practice of using creosote-impregnated utility poles began in London in the 1830's, with pipes made of lead, clay or even wood. As portable pumps for fire-fighting were devised, fire hydrants were devised that drape down from the overhead lines, allowing convenient connection points for firefighters and marking-posts for dogs, provided they could jump high enough.
As new utility services were devised, it was deemed convenient to simply suspend them from the overhead poles already in existence. Natural gas, for instance, distributes overhead to can-type pressure regulators mounted on poles; in America, these regulate gas pressure down to 4 ounces or five pound service before entering buildings. Sanitary sewer and storm sewer lines are pumped up via sump pumps and flow in overhead cast iron lines to treatment stations; this practice became commonplace after numerous failures in gravity drainage owing to root intrusion and seismic breakage in underground lines. In the modern age, millions of Americans work, play and live their lives while rarely giving a thought to the water, effluent and gas whizzing overhead.
Unfortunately, the model of overhead utility services was devised by Empires which, by and large, were not located in areas prone to hurricanes, tornadoes, blizzards or other forms of extreme weather that can generate high winds. Lines run on poles above the ground, as it turns out, are quite susceptible to high winds, not to mention freezing conditions and weathering. Data from Hurricane Irene illustrates this point nicely; the media reported extensively on the millions of homes left without running water because trees fell across mains and shattered pipe, and who can forget the images of broken sewer pipes spraying nauseating effluent all across New Jersey?
The question, therefore, is whether a paradigm shift is warranted regarding the optimal configuration of utilities. Should America take another look at the buried approach?
The advantages of burying utility services are easy to see. Certainly a pipe located several feet below the ground will not be exposed to damage from high winds, although large enough fallen trees may still cause damage as their deeply-dug root systems uproot destructively. Additionally, a pipe below ground is less likely to be subject to freezing, is harder to steal or vandalize, and will be well-supported by the bedding of the trench in which it is run.
There are also operational advantages to running sewer systems underground. To the extent it is possible, employing gravity to remove wastewater is preferable to relying upon a powered system to eject it. The sump pumps can fail, and when this happens a building has no way to reject rainwater or sewage. However, if these systems could be configured so as to drain entirely into a gravity-run subsurface drainage system, this vulnerability could be eliminated.
However, there are many disadvantages to this approach. Cost is of course a significant consideration. Running sanitary, storm, gas and water systems under the ground will require the displacement of large amounts of earth. It will demand close and careful coordination between these systems and other things which may already be in the ground, such as buried power lines. Much of these lines will certainly require the excavation of large amounts of hardscape as well as grass and plantings; few citizens will appreciate the tearing up of roadway infrastructure to accommodate the burial of services that they rarely think about to begin with.
Additionally, there are other operational hazards to buried utility services. As observed previously, there are risks of buried line breakage associated with seismic events, tree roots, uneven soil density, lines buried under heavy traffic roadways and soil corrosion. When a buried line breaks, spotting the break's precise location can be difficult, whereas this is trivial for overhead services. Repairs can also be difficult and costly, requiring significant excavation and temporary pumping along with the tasks of material replacement.
There may even be hazards to life and limb. Buried high pressure natural gas has the potential to explode in a destructive manner that overhead lines could never expect to see. Broken sanitary sewer lines could seep waste into the water table for many years without being detected. Likewise, spot leaks in buried potable water lines could allow contaminated soil to foul water and harm people long before the problem is noticed.
We therefore conclude that while there may be many reasons why burying utility services appears attractive, at least at the first blush, there are at least equally as many reasons to disincentivize this approach. Hurricanes and other severe storms, while certainly damaging and frightening to the general public, are also rare enough that they typically impact only a relatively small number of people in any given year. The public should not rush to demand change to engineering principles that have been established for thousands of years based solely on a new idea's apparent face value.
We recommend that for the time being, water, sewer and gas utilities should remain mounted overhead in their current configuration. This conservative approach has served the western world well for centuries, and until such time as costs come down for buried work, overhead utility distribution should remain the model for American infrastructure. Services buried below the ground may well be 'out of sight, out of mind', but given the inherent risks, this approach should also be judged out of bounds.
