What is the best way to knock down some huge snow piles?

Use someone else’s car to do it.

Flamethrower.

A shovel, a little at a time. No sarcasm intended here.

1. Break up the hard stuff into smaller pieces. It melts faster.
2. You could try water, but whatever you do, don’t turn on the garden hose; it will lead to a plumbing disaster. Bring buckets of warm water from inside the house.
3. How old are the kids? Could they be cajoled into building a fort in the yard with buckets of snow from the sidewalk?
4. Heat – Do you have a chimneria, freestanding firepit, or charcoal burning barbecue that you could put near an edge of the pile and light up?

If the city put snow on your sidewalks, don’t they have to clean it?

In most cities, it’s the homeowner’s responsibility to keep the sidewalks in front of their homes clear and passable. If there’s an easement between the sidewalk and street, the homeowner is responsible for maintaining that as well.

Sadly, if you can’t melt it somehow, a shovel. You’ll need to start at the top of the piles, though. Just knock off 6 inches at a time or so until you get it low enough to actually shovel the rest off. Take lots of breaks! That kind of work will wear your ass out quicker than you’d ever guess. Good luck!

Borrow a friend’s gas guzzling 4×4 suv and plow through them!

There is a variety of space heater that operates on the same principle as a jet engine. Fire it up and see how long the snow sticks around. Works best when you’re on a hill.

I’ve never lived in an urban area that got much snowfall, but I’ve heard that cities have resorted to picking the stuff up with a bucket loader and hauling it off in dump trucks. Your only practical option if the city does nothing is to try spreading the snow out in some way. When the cold snap breaks, the more surface area exposed to the sun the faster it will melt.

Your neighbors are in the same situation that you are. Whatever you decide to do, all of you should do the same thing together. One possible solution is shoveling some of it back out into the street to melt. The city isn’t going to like that, so everyone has to do it together.

A thin dusting of dirt, fireplace ashes, etc will cause the snow to melt faster when the temperature does rise; darker objects absorb heat faster.

Using hot water or heaters of some kind is really a massive waste of fuel and resources.

If the snow keeps accumulating and temperatures don’t rise, the city residents are simply going to have to accept the loss of sidewalk space until the city starts actually removing the snow in dumptrucks rather than pushing it aside.

A reminder to my fellow rural folks: When the county plow blocks the end of your access drive with snow, remember to plow it back out to the right. That way when they make their “second pass” the snow will be pushed away from your drive entrance.

You may be able to build a makeshift radiator that you could stick into the snowbank.

I would use one of these. It would probably do the trick quite nicely.