What watt?

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”.

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