The Quarry Missions are unlocked after finishing the mission Explosive Situation. All the missions have to be done in order and they all start next to the office in Hunter Quarry. You cannot start any mission in this set with a wanted level. Once you complete one, you will need to go back up to the office to receive another one.
REWARD - $500
You have 3 minutes and 30 seconds to clear rocks from the path by dropping them over the cliff. Start by going forward and pushing the first rock over the cliff, but don't worry if it doesn't go directly in the red marker. Make sure to not drive the Dozer over the cliff with the rock. After pushing the first rock, go to the left and get the next rock. After the second, go to the right and push the rest of the rocks over the edge. If need be, feel free to drop over the edges to get to the rocks faster, since the Dozer is quite difficult to keep overturned.
REWARD - $1,000
Some bombs have been planted by a rival company and you will need to move them into red markers to complete this objective. The first one is behind the office at the start and you have 1 minute and 30 seconds to move it into the red marker. Once it's in there, move away from it and it will explode and you'll get a report saying the next one is by the crane. Drop down to it and push it to the red marker a little bit up the hill, making sure to not run out of the 2:10 time given to you.
The next bomb is located next to the grinder and you have about 2:26, so drop to the bottom of the quarry and move the bomb into the red marker. There is one more bomb left and you have about 2:45 to move it into the red marker. Locate it by the crusher and move it to the marker to finish this mission.
REWARD - $2,000
The rivals who planted the bombs are escaping in a Dumper and you have to use one of your own to stop them. You must remain inside, so make sure to grab an Uzi-type weapon before doing this, as it makes it very easy. Get in the Dumper and get on the road and drive until you catch up with the rivals. Pull alongside them and pump their Dumper full of bullets, which shouldn't take too long. Once the damage meter is empty, the Dumper will catch on fire and explode, which signals a successful mission.
REWARD - $3,000
The bodies of the guys from the last mission are in the back of a Dumper and you have to get rid of them before the cops come snooping. You have four minutes to do all of this, so get on the Sanchez as soon as the mission starts, then drive along the edge of the quarry to the other entrance.
Once there, hop in the Dumper and drive CAREFULLY to the other entrance. If you drop the bodies by driving recklessly, then you will fail the mission. Once back at the office, drive carefully down the ramps and to the bottom, where you'll find a fire burning at one end. Back up slowly and then dump the bodies into the fire with the right analog stick to finish the mission.
REWARD - $5,000
You now have 3 minutes to deliver some explosive barrels to the airstrip at Verdant Meadows. Plan your route before you actually start driving, since you have to be careful to not drop any of the barrels like the bodies in the last mission. Stick to the roads and you shouldn't have too much of a problem with the barrels dropping. Try to cut some corners and get on the road that is directly south of the airstrip, then you can get on the strip yourself and get to the red marker. Once there, simply drop off the barrels in the marker to finish the mission.
REWARD - $7,500
A Dumper has spilled its load of explosive barrels on the train tracks and you must use the nearby Dozer to clear the tracks before the train comes. You have 3 minutes to do all of this. Get in the Dozer and head for the tracks. As soon as you see the tracks, get on them and head towards the green markers.
Push the barrels off the tracks until you see the green blip disappear from the radar, which means it's no longer a problem. Don't spend too much time trying to move each barrel, but instead head down the tracks and move the barrels off in groups of 2-3. The mission is finished when the train passes through and you see no green blips on the radar.
REWARD - $10,000 and Quarry becomes an asset ($2,000 max)
You have 8 minutes to head to the bottom of the quarry, load up a dead cop and his bike and get rid of them. Begin by getting on the Sanchez and heading to the bottom of the quarry by jumping over the cliffs. Once at the bottom, get into the Dozer and you'll see two green blips appear. These are the body and the bike and you must push both into the red marker. This can be frustrating a bit since both seem to roll under your Dozer, but keep at it and get them both into the marker.
Once you got both, get out of the Dozer and run quickly to the crane and enter it. You must use the crane to pick up the body or bike and then load them into the back of the Dumper nearby. Once you have both in the Dumper, get inside it and hurry to the entrance of the quarry, making sure to not lose either in the back. Once at the entrance, completion is only a short ways away. Head to the red marker and VERY CAREFULLY dump the "cargo" into the water, making sure not to go in with them.