What Does NYC Do When There's No Place To Put The Snow

In honor of Engineer’s Week –

I have a daughter that lives in Manhattan and I asked her what NYC was doing with the 16” of snow that fell recently. Pile it up and leave it to melt? Scoop it up and truck it to a snow farm in New Jersey? Push it into the river?

I would never have guessed that The City deploys giant snow-melting machines. 

https://www.nbcnewyork.com/news/local/what-does-nyc-do-when-theres-no-place-left-to-put-the-snow-meet-the-melters/2866718/

After watching this I had to ask, How much energy is required to melt all that snow? 

It is easy to calculate -- the mass rate through one snow-melter times the latent heat of fusion for water, 334,000 Joules per kilogram.

The reporter said the flow rate for one of these machines is 60 - 120 tons/hour. Using the minimum, 60T = 54,431kg, in one hour a snow-melter must add 54,431 x 334,000 Joules/hour = 18 billion J/h = 5 megawatts.

One ton of coal can generate, on average, 2.5 Mw of electricity. So, one snow-melt machine is consuming the equivalent of 2 tons of coal, per hour. Obviously, they are not burning coal and they're not plugging one of these machines into the power grid.

If their energy source is automotive gasoline, they need about 136 gallons per hour to produce 5 Mw and melt 60T of snow. To get through an 8-hour shift without re-fueling, one snow-melt machine would leave the garage with just over 1,000 gallons of gasoline. That is a lot of flammable liquid to haul around a densely-populated city.

(BTW, this assumes the snow comes in at 32F, no colder, and the water that leaves is 32.1 F, that is, all the machine does is melt the snow. It doesn't have to heat the snow to 32F and it doesn't have to heat the melt water to say 40F. That would add to the total but the energy to melt 1 kg of water is 80 times greater than the energy to raise the temperature by 1C.)

The report said they're deploying 7 out of 30 snow-melt machines. Seven machines, each consuming 136 g of gas per hour will use 7,616 gallons in one, 8-hour shift. That is 2.5 small tanker trucks of fuel per day to run 25% of their total fleet.

I thought NYC would load snow into trucks and dump it in the river. I believe that's what Denver does after a large snowstorm. However, it may not be environmentally friendly to dump snow from NYC into a river. I don't know what workers find in that snow but I'm sure no one wants it in the water.