Peace Pipe - S2-E5
Other mistake: When John and Roy are up on the scaffold with the injured man during the sniper fire, from the time they unfurl the large tarp and tie it off to the beams the sniper fires zero shots at them, zip, but later at the station Chet asks John, in all seriousness, if he got a good look at the tarp before they left, and tells him that the tarp looked like Swiss cheese due to the sniper fire.
Answer: It is standard practice to wet down driveways so that they stand out in a long shot.
stiiggy