Other mistake: When Station 51 is dispatched to the landslide, the engine company get into their turnouts and roll out, but in the next exterior shot as the engine drives past the camera, not only are the guys not in their turnouts, it's too obvious that none are 51's guys, and the one in Chet's jumpseat even leans forward. Presumably they're 127's guys. Also the light bar on the squad and the rotating light on the truck are not on.
Other mistake: When Station 51 is on scene at the landslide, there's a dresser on the grass in front of the house, and when the explosion occurs due to the broken gas main, in the closeups as Johnny dives to the ground there's what looks like a can of gasoline (used for the stunt perhaps) atop that dresser that wasn't there before, and it's also not in the wide shots as Johnny dives down.
Other mistake: After Brackett tries unsuccessfully to get O'Brien on the line to ask about the fish tank, it cuts to an exterior shot of Station 51, and we hear the dispatcher say, "All units responding with Engine 3 cancel," but subtitles read, "Four units with Engine 3 cancelled." Subtitles from Universal Studios 2010 DVD.
Other mistake: When the man injured in the manhole is brought to treatment 6, Early tells Roy to patch him up for an EKG, but the subtitles read, "Patch one from the EKG," and then Early tells the x-ray technician to do a skull and chest series, but the subtitles read, "Skull and chest searches." Subtitles from Universal Studios 2010 DVD.
Answer: It is standard practice to wet down driveways so that they stand out in a long shot.
stiiggy