The weather may be cold, but infrastructure is a hot topic in the city. This February, the New York Times carried two unrelated stories that remind us that when you're walking on a city sidewalk, what's underneath you can be far from obvious.

On February 28, the Times Real Estate section reported on a high-rise amenity that's proving itself popular during this year's harsh winter: warm sidewalks (see: "Ditch the Snow Shovel," by Michelle Higgins). Using hydronic tubing or electric resistance heating buried beneath the paving, snow-melting systems can keep sidewalks or courtyards clear and dry even as the snow piles up on neighboring properties or workers sweat to shovel it away.

The technology is uncommon in the city, in part because it's costly to install as well as to operate. It also requires a long permit process to be approved. And although people who have snow-melting like it, even architects who have specified it admit that it's something of a wasteful luxury. Said one: "A huge amount of energy is required to accomplish what one person can do in 20 minutes."

But as the lucky few were enjoying their clear dry walkways, the Times reported, February brought another kind of hot sidewalk to the city: An entire block in the New York neighborhood of Chelsea was electrified by "stray voltage." (For the full story, see: "Stray Voltage Temporarily Electrifies Block in Chelsea," by Mark Santora and Colin Moynihan.)

After a fatal accident in 2004, the Times reported, the city created rules requiring utilities to routinely test for circuit flaws and stray voltage on New York streets. Last month, the Times reports, "A utility truck equipped to measure stray voltage was surveying Chelsea when, at around 4 a.m., workers detected a single stray volt on Avenue of the Americas. As they investigated, the measurement shot up to 44 stray volts. When the rain picked up on Wednesday morning, it combined with the salt on the ground to become an effective conductor of electricity, quickly spreading the voltage to other objects. The metal grates in the sidewalk on the east side of the street were electrified, as were many other metal objects in the area." Even some doorknobs on buildings carried a charge, the paper reported.

In this case, authorities said, the current detected was probably harmless (see: "Chelsea Block Deemed Safe After Stray Voltage Scare," by CBS News). Utility spokesman Mike Clendenin told WINS radio reporter Al Jones that the warnings were just a precaution. Said Clendenin, "Not anything that anybody probably could have detected, but our instruments that we use are very sensitive. It was 1 volt."