Is there bigger harm to env than building parking lot? We've got plenty of these.

Why not building it under already wasted dead space like parking lot and have snow-free parking lot as extra bonus.

If the underlying stored heat leaks to the surface then it may indeed melt the snow and you'll have "snow-free" parking, but that won't be the end of the story, as all that resulted water will most likely turn your parking lot into an ice rink.

snow-free means you're losing heat to the environment vs keeping it contained. I would imagine if properly designed you could stand on top of the completed dirt pile without feeling any temperature delta with the air.