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Engineering concerns with flooding
Continuing the current series, we look at the impact that current pump and related technology has contributed to draining New York after Super Storm Sandy, as well as new innovations that are being developed. As covered in the last blog, the pumps that currently exist in the subway system are not quite up to par with the engineering standards of today. One of the main deficiencies is that they were designed to handle light freshwater rain, or about 2 to 4 inches, but in the hurricane almost 4 feet of seawater put those same pumps to the test. On a normal day with no rain at all, the pumps pull about 13 million gallons of water from the subway, but against all odds by the Monday following the hurricane the subway was running at almost 80% capacity. While this is quite a feat, it still has a damaging effect on day to day lives throughout the city.
Many officials project that if the city of New York was to overhaul the subway system and make it truly Hurricane ready it would be about a $30 billion and eight year project, not to mention the numerous inconveniences that would be caused to all of the people that rely on the subway every day.
Engineering developments and solutions
So far in the subway “investigations”, no serious structural damage has been detected, or at least nothing that couldn’t be drained or fixed quickly. Days after the storm, estimates projected that there is still about 45 million gallons in a 6,000 square foot area that is completely submerged between the Battery, or central hub, and the Hugh Carey tunnel. To handle this and whatever remaining floods are present in the subway, the New Orleans District Army Corps of Engineers sent a 12 man, team that also aided with Hurricane Katrina, and brought in 6 and 12 inch pumps that were able to move 250 billion gallons of water during Katrina. The first improvement that is planned once all of the water clears is to raise the entrances and ventilation grates so that they are able to handle more water. One type of prevention would be to plug the tunnels ahead of a major storm. Currently, mechanical engineers within the Department of Homeland Security are working with private engineering firms to make plugs that resemble giant balloons that would work to protect miles of subway tunnels, as well as above ground tunnels from flooding. Originally designed to help prevent gases from terror threats within the tunnels, these plugs are now being looked at to serve a dual purpose to include flooding. Once inflated with either air or water, the plug can fit the contour of the tunnel opening thus stopping the onset of flood waters. The other concern though, would be as to how disastrous the above ground or station flooding would become from the excess water that was not allowed into the tunnels. The storm drain system is yet another concern that has to be taken into effect when considering the cost of truly making NYC hurricane ready. We can look to the drainage tunnels of Tokyo as a way to help with the drainage for a highly populated city with flood concerns. Just on the outside of the city lay 5 massive water tanks underground that collect the excess water and transfer it down a series of tunnels to an underground pump area. Large turbines powered by jet engines then pump out the water to the nearby river. The engineering behind this system is pretty straight forward, but on a very large scale. While the cost for this engineering feat was about 3 billion dollars, the cost in damage of just one storm was over 10 times that amount. As for improving the current pipe and drainage systems that we have, many are doubtful anything will get done without another large storm serving as a wake-up call.