I wrote about roads and bridges. I started this thread by talking about drinking water and the issues that surround our pipelines. When it comes to water, the pipelines are only part of the problem. Before the water ever gets to the pipes, it meets quite a lot of America’s failing infrastructure, like dams and levees. These dams and levees also keep out raging river waters, stormwater run-off, and even scarier environmental concerns like fly ash.
America’s dams are an average of 51 years old. Built without the benefit of the technology that we have today. We have approximately 85,000 dams in the United States, and some 4000 of these are deemed potentially unsafe. Of these 1800 are considered high hazard, which means that should they fail, there could be great loss of life and huge property damage. We needn’t look too far back to see the potential for devastation should any of these dams or levees breach. New Orleans is grim reminder of how our aging infrastructure has failed to keep us safe from harm, and it continues to struggle in its recovery. What city will be next?
Consider the very real threat to Nashville, and large parts of Tennessee. The Wolf Creek Dam is situated some 250 river miles upstream from Nashville. Construction began on the dam in 1941, and was completed in 1950, long before the computer age. Behind it lies Lake Cumberland, with 66,000 surface acres and an average depth of 90 feet. That is a lot of water to hold back. What wasn’t known in the 40′s was how precarious it is to construct a dam on porous limestone. Over the years, water has been eroding away at channels in the rock and wearing away at the foundations of the dam. Were it not for the sink holes that developed in the early 2000′s, engineers may not have even discovered the problems before it was too late. Since that time, they have poured tons of rock, concrete and grout into the foundations to make them hold up, and in the end found that this was not enough. They had to start construction on a whole new wall to make the dam really safe once again. Were it to burst, the water in the lake would race down the Cumberland River flooding hundreds of towns along the way, including Nashville, Tennessee-which would be as much as 20 feet underwater. Additionally, we cannot estimate the economic damage, as the Cumberland River is part of the vast connected network of waterways that we use to ship goods inside the US.
Dams hold back more than just water. Much of our electricity in the US is supplied by coal burning power plants. Beyond the CO2 issues with coal generated electricity, there are toxic water issues that are rarely mentioned. That came to the forefront last year when a dam burst holding back fly ash sludge, a by product of local coal plants. This released a river of waste that destroyed homes, land, and lives. I think that we have only begun to see the health issues that are likely to arise from this catastrophe, as fly ash is loaded with heavy metals like arsenic that leech into groundwater. Most sad of all, is that fly ash can be substituted for Portland Cement in large quantities when making concrete, so this waste stream could have been put to use.
Dams in America are valuable assets, as long as they hold. They require maintenance and inspection to keep them in top shape. Yet, with the thousands of dams across our country, there are few inspectors to oversee them. Some states have only one or two full time inspectors, and some have none whatsoever. Add to that the loss of manufacturing. There are hundreds of smaller dams that were originally built by corporations that have been abandoned. Inherited by the states where they reside, little may be known about their safety or even their construction.
But dams are not our only issue. Built to hold back water in times of high flow are thousands of levees. These are woefully inadequate in America. Many fail during peak rises in the Mississippi, and we all know what can happen to a city highly dependent on them, like New Orleans, during natural disaster. The issue in some areas is huge, and relatively unknown by the majority of Americans. While California deals with budget shortfalls and wildfires, there is a brewing problem that no one talks about. Much of the southern part of the state is supplied by drinking water from the Clifton Fore bay, which is fed by the San Francisco Delta. The delta is region of some 1000 square miles that was created from marshes by building hundreds of dirt levees. Built in the 1800′s by farmers om soft peat soil, these hold back excess river water that goes into the San Francisco Bay. Since their creation, this land has sunk some 25 feet, meaning that it is below the water line and must be constantly pumped to keep it dry. If there were a large earthquake near the levees, like the one that hit California in the 80′s, these levees are likely to fail. That would flood the entire delta, and as a reslut it would suck slat water from the bay into the basin and its water system. The Clifton Forebay would have to close, to keep the salt water out. With rationing, Southern California could last 6-12 months, but it would take 2 years or more for the watershed to return to normal and salt levels to normalize. A stretch? There are estimates that there is a 66% chance of this kind of earthquake happening in the next 30 years, but with a cost of $25-$40 million per square mile to fix the problem, it is an issue that is not likely to be dealt with soon.
As long as we continue with business as usual, the problem will only continue to get worse. We have to start building more sustainably as we go forward. By using some of these materials, like fly ash, in our construction, we can alleviate some of the burden. By investing in renewables, we can decrease the output of fly ash to begin with. By restricting our development to areas that can support themselves, we can reduce the need for more infrastructure like the kind we created to make LA an oasis rather than a desert. And by building less in flood plains we sill diminish our need for levees and the maintenance they require.
