In this mission you'll have to destroy all the portables at the construction site. A 3 minutes time limit will start when you destroy the first portable, when you attack a construction worker or when you enter a vehicle. Get a Dozer, it doesn't matter which one, but maybe it's best to get the moving one. In that case you won't get bothered by it when destroying the portables. Watch out for the barrels because they will explode as soon as you hit them, probably killing you during the process. Meanwhile don't bother the construction workers, just drive over them with your Dozer. The timer will stop as soon as you destroyed the last portable. The game will now show you a little cut scene where you'll see the foreman flee into a mobile toilet. You have to use the Dozer to push the mobile toilet into the ditch. When it's lying in there, park the Dozer somewhere away from the ditch and then get in one of the Cement Trucks. Drive to the ditch and park the Cement Truck backwards in the red marker. When you positioned it another cut scene will start where the foreman will be buried under a layer of concrete. After this you've completed the mission.