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Part Three of a Series: “We have met the enemy and he is us” introduces the topic of the impacts of a “dewatering system” on the infrastructure of a city. Part II “It’s all related” continues the discussion with the impacts on water and rivers.
So what does a water issue have to do with energy? Simple, you may recall from the previous posts, that the new Marriott Hotel being constructed in downtown Indianapolis has a parking garage that is three floors below grade (underground). The third floor extends below the top of the water table which required the installation of four pumps to extract the water and send it into the sewer system. These pumps run 24 hours a day, seven days a week, 365 days a year (and sometimes 366).
Now, I don’t know what types of pumps are installed in the Marriott or the size of the pumps nor am I an electrical engineer. However, it is reported that they are pumping a total of 1,200 gallons per minute, or 300 gallons per minute per pump. I doubt very seriously that they sized the four pumps right at 300 gpm, but let’s say for a minute they did. A quick internet search finds that a typical industrial dewatering pump capable of pumping 300 gpm requires about 460 volts of electricity and draws about 20 amps. That is the equivalent of 9.2 kWh (kilowatts per hour). Four pumps running 24 hours a day comes to about 900 kWh every day. As a comparison, the average American family uses 938 kWh every day. So, every day, the pumps use enough electricity to power a house.
As I mentioned, they probably did not size them at the bare minimum. Perhaps they put in 600 gpm pumps. One of those pumps uses 460 volts and draws 54 amps. That is almost 25 kWh per hour per pump. Four pumps running 24 hours a day would use about 2,400 kWh a day, or enough to power about 2.5 households.
We can’t have a discussion about energy use without mentioning CO2 emissions. This amount of electricity produces from 236 metric tons of CO2 a year on the low end to 629 metric tons on the high end. That is the equivalent CO2 of between 43 and 115 cars on our roads…from the dewatering pumps of one building in one city.
And since 96% of Indiana’s electricity comes from coal, consider the other impacts of burning coal…air pollution (beyond carbon), water pollution, sludge creation and storage.
There are indirect energy impacts as well. Since all of this water is being pumped (presumably) into the Combined Sewer system it has to be processed as wastewater. A typical wastewater treatment plant burns 6,000 kWh of electricity to process each million gallons of water. As we know, these pumps are flushing 1,728,000 gallons a day into the system or about 630,720,000 gallons a year. How does 3,784,320 kWh of power sound? That’s almost 11 more households of electricity. And carbon? How does another 2,195 metric tons of carbon sit with you? ANOTHER 400 cars!
Keep in mind; this is all to move water that didn’t have to be moved in the first place!
Stayed tuned for the final installment in this series, “Killing me softly with…PVC”.
In my previous post “We have met the enemy and he is us“, I discussed the “dewatering system” that was built for the new Marriott Hotel in downtown Indianapolis and the impact this system will have on the Combined Sewer Overflow system. Today, let’s examine some of the other impacts this system and others like it have on our environment.
John Muir once said “When one tugs at a single thing in nature, he finds it attached to the rest of the world.” What this means is all of the systems in nature are interrelated and changes in one area can have dramatic impacts in others, in other words, when we try to outsmart nature, we inevitably screw something else up! This “dewatering system” is an excellent example; there are impacts, not only to the water systems, but also to energy, carbon emissions, human health and wildlife survival.
Water – Forget the fact that these pumps are taking what could be perfectly good drinking water (or at the very least perfectly good “process” water) and flushing it down the drain, there are other impacts to the water systems. Because the parking garage in this example was built below the water table, pumps run continuously to pump the naturally occurring groundwater into the sewer system. The effect of this pumping is to lower the water table in the area, and potentially in a large surrounding area. When the water table is lowered several things occur. First, anyone in the area that is using well water will find that their wells go dry as the water table lowers, thus requiring them to dig their wells deeper, sometimes at great expense. Next, as the water table lowers, water, being water, will follow the path of least resistance and begin to “fill in” the area. This means groundwater from a larger area will begin to move thus impacting larger and large areas. In some cases, nearby wetlands and rivers could begin to drain and dry up.
In addition, as the water table lowers, plant life that is dependent upon that water will begin to die out as its root system can no longer reach its water source. This may require additional irrigation to keep the plants alive which adds to the vicious cycle and strain on the water system. In some cases, invasive plants will migrate into the spaces left behind by the dying plants. Wildlife that depends on the native plants will die out or migrate to other areas due to lack of food.
Among the impact caused by lowering the water table is subsidence. Because the presence of ground water creates hydraulic pressure, it is able to support the weight of the soil, rock, AND BUILDINGS above it. Removing the groundwater will cause a “sinking” or settling of the earth above it. Don’t believe me? The city of San Jose is THIRTEEN feet lower today than it was 100 years ago. The problems in New Orleans were exacerbated in part by subsidence caused by the extraction of groundwater over the last century. What will be the impact to the buildings as the ground around them SINKS? They too will sink and settle causing foundation problems, and other structural and non-structural issues throughout the building or HOME!
River – While we are talking about water, let’s look at the impact on the river. According to the senior manager on the project for Marriott, the water was going to the river any way, well was it? Ground water is replenished by rain water, surface water, AND NEARBY RIVERS AND STREAMS. This water may have COME from the river not be on its way TO the river. As the water table lowers, the river could try harder and harder to refill the void, eventually drying up the river. It has happened before folks! However, let’s assume for the moment that the manager was right and the water was heading to the river. By “speeding up the process” the ecosystem of the river will be changed. Rather than the water slowly filtering through the ground (and being naturally cleaned and filtered along the way) it will be blasted into the river. This will lead to increased erosion as the water speed is faster than is natural. The increase in erosion will lead to additional sediment in the water (already the number one pollutant in Indiana). This increase in sediment will begin to kill off the fish and plant life in the river as they can no longer find food or the food dies off because of lack of sunlight that is now blocked by the sediment. In addition, many of the organisms that serve a key role in the food chain are impacted by even slight changes in water temperature. Because this water did not reach the river naturally, it will change the temperature of the water.
Energy – What a minute, I thought we were talking about water here, what does that have to do with energy? In my next post we will discuss the energy impacts (both direct and indirect) of the “dewatering systems”.
What was true in 1970 when Pogo first uttered his immortal words is truer still today. At the time of this writing, my city, Indianapolis (ok, yes I live in Carmel, but much to the chagrin of many Carmelites, Indianapolis STILL is the major metropolitan city in this area), is in the midst of a 17 year project to mitigate it’s sewer overflow problem. Indy, like several hundred other cities, utilizes a Combined Sewer Overflow system. Basically, what that means is wastewater from homes and businesses (uh, sewage!) and rainwater from streets and parking lots utilize the same pipes to transport the water (and the, uh, sewage) to the treatment plants. Sounds logical, right? You only have to lay one set of pipes, excellent! Except…when it rains. That’s where the overflow part of the Combined Sewer Overflow system comes in. When the amount of “water” to be processed exceeds the capacity of the system, it is allowed to flow freely (“floatables” and all) into local rivers and streams. In Indianapolis, the amount of rain required to cause the overflow is ¼”! One quarter of one inch! In 2008, Indianapolis received a rainfall of over ¼” SIXTY times…about 6 or 7 BILLION gallons of sewage a year! Anyone want to go for a swim? How about a nice drink? Or, fish fillet? Want to be grossed out? Check out WTHR’s Bob Segall’s article at http://www.wthr.com/Global/story.asp?S=9260797.
The good news is we are fixing the problem, to the tune of several BILLION dollars, but we are fixing it. The bad news is…we haven’t really learned anything in a hundred years. A recent article in the Indianapolis Business Journal featured the “dewatering system” of the new 1,000 room Marriott hotel in downtown Indianapolis. This $425 million project is part of our city’s plans for hosting the Super Bowl in 2012. “Dewatering System” sounds so innocuous doesn’t it? Sounds almost like a dehumidifier or something, right? So, what exactly is a “dewatering system”? Many of you have homes with basements; undoubtedly you have a sump pump. These systems are designed to funnel water to the pump where it can be moved away from the foundation of the house. They help to prevent water from leaking through the foundation of the house into your basement. On a much bigger scale, that is the type of system engineered at the Marriot. Still sounds pretty harmless, right?
The system at the Marriot has a series of almost 5,000 feet of PVC pipe, funneling water to sump wells that are four feet wide and nine feet deep. There are four pumps that run every minute of every day pumping 1,200 gallons of water a minute. That’s 1,728,000 gallons a DAY, or 630,720,000 gallons a YEAR! That is enough water to supply 10,000 households for an entire year! And, what are they doing with all that water? According to the senior project manager they are sending it “right to the [White] river”. Hmmm, so they ran a pipe west from those pumps over a ¼ mile UNDER White River State Park to the river, or was it south almost half a mile under Victory Field, or north under the Eiteljorg and the Indiana State Museum. Uh, I don’t think so Tim. If I were a bettin’ man, I’d bet they will pump 630,720,000 gallons of water each year into the Indianapolis Combined Sewer System, where it not only adds to the amount of waste water that has to be handled by the system, it also has to go through the waste water treatment facility and be processed before it goes “right to the river”.
What design issue led to the decision to pump over a ½ a BILLION gallons of water into the Combined Sewer System? The three story BELOW ground parking garage is five feet deeper than the level of the water table on the site….five feet. So, think about this…how many buildings in downtown Indy have three floors of parking, or other space below ground and are pumping just as much, if not more water into the Combined Sewer? Dozens? Hundreds? In some states, it is a criminal offense to capture the rain water that falls on your property, yet we are literally flushing billions of gallons of water each year down the drain…AND we are all paying for it. Not only are we paying for the project to overhaul the sewer system and the capacity to handle water that was not entering the sewers to begin with, but we are paying for the waste water treatment facilities and operations, and we pay for it in the damage all this water has on the river itself. One day, in the not so distant future, we are going to be desperate for water to drink. Think of the cost that will entail!
Surely in this day of Low Impact Development and Sustainable Design we can come up with better solutions than just dumping the water down the drain. How about a two story parking garage, instead of three, how about building above ground instead of below, how about using that water to flush the 1000 or so toilets in the new hotel and for other non-drinking uses, how about filtering it and using it in the hotel pool? How about building codes that require developers to USE the water on their site rather than just pumping it into the water system?
The impacts of design decisions like this one go far beyond the strain it places on our sewer infrastructure. The great environmentalist John Muir once wrote, “When one tugs at a single thing in nature, he finds it attached to the rest of the world.” In my next post, we will examine some of the other impacts of the “dewatering system” on, not only water, but energy, carbon, and human health.
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