Thicket Excavations

Thicket Excavations is a quarry located in the northwest Commonwealth in 2287.

Background
This quarry has a reputation across the Commonwealth for producing the finest mirelurk meat due to the waters giving it a better flavor.

Layout
A fenced in quarry area that has been flooded, it is found to have scatters of cut stone around it. There are stairways leading up the north side of the quarry and a sloped ramp that extends into the water. The top level on the east side includes an elevator as well as a camper in which Sully Mathis's terminal can be found which details his plans for restoring the quarry for use as a base. There are several campers spread out around the nearby area. When the water drains and the raiders take over, raiders become spread out throughout the quarry. As well as 3 Mirelurk pens find their way within the area.

While the quarry is flooded, the elevator will not function from the surface. But even if you have Power Armor, you may not drown if you dive in (depending on where exactly you stand or swim); but you will immediately sink to the bottom of the quarry, unable to 'swim' back up. You can walk around, potentially finding a route using stairways and platforms to make a return to the surface. You can also reactivate the elevator by pressing the button right at the bottom. However keep in mind that wandering along the bottom of the quarry will be very time consuming compared to swimming around and repairing the pipes without Power Armor.

Some time after completing Sully's quest, you may hear that an allied settlement is being attacked by raiders stationed in the quarry. Abernathy farm will send you to the quarry to exterminate the raiders on occasion.

After completing the quest Pull the Plug, and 24 hours have passed, Sully Mathis will be hostile, and be the leader of a raider gang which he initially commented about doing in his terminal entries. However if you kill him immediately after you turn in the quest, that will be that.

Notable loot

 * Taboo Tattoos - In the trailer directly southwest of the water pump.
 * Sully's journal - Holotape in the east trailer inside of a terminal.

Appearances
Thicket Excavations only appears in Fallout 4.

Bugs

 * Upon arrival at Thicket Excavation there seems to be a foglike low-res concrete-floor, hovering above most of the real surfaces, and it persists under water. It is the high distance version of the model (aka LOD) you should only see when the object is very far away. This manifests in that both the Sole Survivor and Sully Mathis wade knee deep in concrete, Sully always hovers around the compressor/pump, before the Sole Survivor suddenly falls into the water or the access-way leading down into the excavation. The impact of this bug can be negated by restarting the game.
 * If you swim under water to enter the excavation site before draining it, you will fall down to the floor and be able to walk and shoot your gun under water. In some cases Dogmeat may also teleport down to you and swim in place as he tries to follow you.
 * If you swim around enough before draining the quarry it is possible to cause the quarry to instantaneously empty of water and update the world/quest state such that the previously mentioned enemies (raiders, mirelurks) appear.
 * Occasionally, the caged Mirelurks will spawn outside of their cages. Caged Mirelurks only turn hostile when attacked, or when the Sole Survivor (or a companion) enters their cage, so the Mirelurks will roam around without turning hostile. This results in a sort of peaceful Mirelurk. Upon closer examination, Mirelurks are kinda cute... This is a personal entry, and it just happened to me, so I don't even know if it works on other platforms.