Tuesday, July 31, 2007

Post Peak Dam Maintenance, or Lack Thereof

"Dam failures are of particular concern because the failure of a large dam has the potential to cause more death and destruction than the failure of any other man-made structure. This is because of the destructive power of the flood wave that would be released by the sudden collapse of a large dam."[2] What will be the fate of the world's large dams after peak oil as energy declines, technology falters and budgets for inspection and maintenance of these critical and dangerous facilities begin to be pared back in deference to perceived more immediate societal priorities?

(See also; The myth of permanence: post-peak infrastructure maintenance, The Emerging Global Freshwater Crisis, and Lake Ontario & St. Lawrence River after Peak Oil in my blog.)

Most major cities, both globally and here in Canada, were born, developed and have evolved on the low-lying land adjacent to major bodies of water, either saltwater oceans, seas, bays and inlets or freshwater lakes and rivers. The cities sitting on saltwater shores seem to have been built with the dangerously misguided assumption that sea level is and will continue to be constant. The cities on freshwater shores are largely protected by a cornucopia of technology and infrastructure that has essentially stabilized water levels in the bodies of water on which they are situated.

In recent years, with the growth of scientific research and knowledge of global warming, there has been considerable attention paid to the risk faced by major cities over this next century from the potential sea-level rise that could result from the meltdown of glaciers and, most importantly, polar ice caps (79% of the world's fresh water is locked up in ice and snow). Very little attention has been paid, however, to the risk faced by major cities situated on freshwater shores that could result from the potential post peak-oil disintegration and collapse of the technology and infrastructure containing and controlling billions of tons of water upstream from these major cities. There are numerous internet sites that show the inundation risk of coastal areas from sea level rise. Very little has been done on inundation mapping downstream from major dams. That is not to suggest that smaller communities are not subject to the same risks, as most communities have evolved in the same way, on low-lying land adjacent to lakes, rivers and seas.

There are about 80,000 dams in the U.S., for example, the majority even today over fifty years old. According to FEMA, "Approximately one third of these pose a "high" or "significant" hazard to life and property if failure occurs."[1] It is important to note, here, that "high" and "significant" are from a national perspective in terms of potential dollar damage and potential deaths. As the report Flood Disasters in Canada[6] suggests, risk analysis statistics are "biased towards the more densely populated areas ..... where floods are more likely to impact humans." A dam failure upstream of any populated area would, however, be considered "significant" for those living downstream. According to the National Performance of Dams Program (NPDP), "at least 85% of the more than 75,000 dams in the the US will be in excess of 50 years old by 2020." The report goes on to stress, "Perhaps more significantly, most of the large dams throughout the US are also approaching old age."[5] There is, of course, a reason for this impending flush of aging dams. According to the report Dam Construction[7], "Within the U.S., the most active period of dam building occurred between 1950 and 1970, and has been called “the golden age of dam building” (Doyle et al., 2003). The same comment is frequently made about the situation in Canada." In Ontario today, "In the case of Ontario Power Generation’s almost 200 dams, nearly two thirds are in excess of 50 years old."[5]

Generally there is now a trend in Canada to move away from the large hydro megaprojects. "Because of the size, cost and negative environmental impacts of large dam projects, hydro development has been increasingly focused on small-scale projects, i.e., those with less than 10 MW of generating capacity. Many of these are run-of-the-river projects. There are currently more than 300 plants in Canada with a capacity of 15 MW or less (Industry Canada, 2003) and numerous others under consideration, particularly for remote communities that rely on high-cost diesel generation. Approximately 5500 sites in Canada are technically feasible for small-scale hydroelectric production (Natural Resources Canada, 2000)."[7] Though this means a reducing risk of failure of large dams, it increases the number of dams being built in proximity to and designed to service population centers, many remote where emergency response to a disaster would be delayed because of that remoteness.

Fifty years used to be considered the average life expectancy for dams. Not to suggest that the statistics or studies are being slanted but, with the rapidly ageing inventory of North American dams, a report entitled Dam Construction suggests, "Based on extensive U.S. experience, the life span of typically unmaintained dams is conservatively estimated at 75 years, refuting the common misconception that the average life of a dam is 50 years (Donnelly et al., 2002)."[7] Gee, ain't that lucky. I guess that takes the pressure off. The public relations importance of this statement is twofold, first the supposed refutation of the 50 year lifespan but, also, the inclusion of the phrase "typically unmaintained dams". Numerous studies by the International Joint Commission (IJC), FEMA, the National Performance of Dams Program (NPDP), and others, have suggested that even where dam safety programs exist and inspections occur, the vast majority of North American dams are not being maintained effectively today, many not even regularly inspected. The IJC, for example, considers the three dams involved in the international Moses/Saunders hydro dam facility at Cornwall Ontario and Messina New York (these dams hold back the waters of Lake Ontario from the St. Lawrence: the Great Lakes containing 22,573km3 of water, 22.573billion m3, enough water to cover 18.3 million acres of downstream land to a depth of 1 foot), to be potentially unsafe due to lack of inspections and maintenance. Even if the average life expectancy of a dam is 75 years rather than fifty as the above report suggests, that still means that the huge glut of dams built between 1950 and 1970 will all pass that average life expectancy by the middle of this century, at a time when the energy, technology and economy for their increasingly necessary maintenance or their decommissioning will be in serious decline. With the average life expectancy of a dam, whether that be fifty years or seventy-five, the cost and complexity of decommissioning is most often as high as it was for the original construction. There is a significant risk beyond peak oil that dams may simply be de-operated (stopping the usage and maintenance) rather than decommissioned (properly torn down and replaced or returning the river to its natural flow). The track record of site decommissioning, whether dams, nuclear sites, toxic chemical sites, or others, has not been good. There is no reason to expect that it will improve under the difficult circumstances we will face on the other side of peak oil.

Whether or not the focus on "typically unmaintained dams" in the above report is based on a knowledge of peak oil and its implications, it does suggest an awareness of widespread concerns about the future maintenance and maintainability of dams and related infrastructure. A report entitled Risky Business for Dams[5] makes the following statement, "Dam owners are facing increasingly difficult decisions about the ways in which finite financial and human resources should be allocated to ensure the continuing safe operation of ageing dams. Without such investment, dam failure is not only a possibility but can be an expected consequence of lack of proper maintenance and diligence by a dam owner." Washington State alone lists more than a dozen dam failures in the last two decades, despite the level of current technologies, full energy availability and a vibrant economy.[4]

Canada is a large, cold nation. We have significant energy needs for transportation, for infrastructure and industry, and for home heating, cooling and cooking. As the global and national reserves of fossil fuels (oil, natural gas and coal) diminish over the course of this century Canada's needs for energy will still remain high. More and more people will, as fossil fuels decline, revert, out of necessity, to the use of wood for heating their homes and cooking their food. Canada is still blessed with an abundance of temperate forests. These forests, however, are generally not in the same locations as the population concentration. The amount of forest cover in populated areas has already diminished to minuscule levels. The pressures put on that remaining accessible forest cover in the search of fuel for home heating and cooking will become increasingly severe over the balance of this century.

This large-scale reversion to the use of wood for heating and cooking will have a major and increasing impact on the viability of the nation's dams. As forest cover is removed from the hills and fields of a river's watershed (especially in the case of clear-cutting), and with the increasing pressure on those lands for food and feed crop production, the amount of soil and plant material carried by that river will increase, particularly after major weather events. There have been countless examples - globally moreso than locally - of the devastating impact of flooding when a watercourse in flash flood fills with silt and debris from upstream. Often whole communities are buried in mud or wiped out by being carried away by torrents of water. With the anticipated increase in the removal of forest cover for fuel, with the loss of it's impact on the ability of the soil to absorb and retain moisture, and with the anticipated increase in severe weather events due to global warming, the volume of silt and debris in future flood events expose Canadian rivers to the type of catastrophic flooding we have seen elsewhere in the world. The risk of dam overtopping on managed watercourses (which includes most rivers flowing through populated areas) increases dramatically under such circumstances as the volume of flood flow includes as much or more silt and debris as water. That increase in silt carried down from upstream will also dramatically increase the silting up of the reservoir behind the dam. This means the reservoir will have less water for power generation or downstream usage. It also increases the risk of overtopping during extreme weather events as dams will more commonly be run at their maximum reservoir level leaving less margin in the silt-shallowed reservoir for absorbing the sudden run-off.

There is little reason to believe that once we have passed peak oil and the global economy implodes that future maintenance and commitment to safe decommissioning will increase as the tens of thousands of North American dams age. Historically, societies have simply abandoned infrastructure as the society disintegrates. A society in decline simply no longer has the resources to live up to those well-intentioned commitments made when that society was at its peak. The dam-building golden age of the 1950s to 1970s was an age without the foresight of peak oil and its implications for technology and the global economy. That glut of dam building happened without an awareness of the probability that all of those dams would reach old age at a time when society will have gone into terminal decline. It's like a commitment made to maintain a nuclear waste dump in perpetuity as long as the radiation levels in the stored material remain dangerous. It is easy to make such commitments when you see things continuing as they are indefinitely into the future. "All things being equal....." will simply not apply on the other side of peak oil. The rules will have changed. The people who made those commitments in the past will no longer be around to shoulder the responsibility to deliver on those commitments. That will fall to people struggling with simply trying to figure out how to survive the collapse.


The following were key documents in the research for this article;
1) FEMA: Dam Failure
2) Dam Failures
3) Notable Dam Failures: Recent Dam Failures and Lessons Learned
4) Reasons for Dam Failures
5) Risky business for dams
6) Flood Disasters in Canada
7) Dam Construction
8) Hydroelectric power generation

1 comment:

denisaf said...

This well-researched article raises a major issue that is bound to have grave implications as society strives to cope with operating on the depreciating natural capital, including the declining supply of oil. It points out that there has not been the commitment to provide the natural resources to maintain the operation of these dams, so there potentially disasterus consequences