From Geology.com: Abandoned Mine and Quarry Accidents Claim 20 to 30 Lives per Year.
#1 cause of death — drowning.
Drowning is the number one cause of death in abandoned mines. Most people involved in this type of accident went to a quarry for swimming. Quarries are extremely dangerous places to swim. Steep drop-offs, deep water, sharp rocks, flooded equipment, submerged wire and industrial waste can make swimming risky.
Another risk factor is the very cold water. Many quarry operations excavate to depths below the water table and use pumps to keep the mine dry while it is in operation. When mining stops the pumps are turned off and the quarry floods by the inflow of cold ground water. This ground water inflow can keep the quarry water very cold even in late summer.
#2 cause of death — ATV accidents.
ATV accidents are the second leading cause of death. Quarries and surface mines are dangerous places to ride an ATV. Riders unfamiliar with the quarry can speed over a quarry high wall or embankment. Death can result when an ATV is driven too close to a high wall and the rock, shattered by blasting, collapses from vibrations or weight. ATV riders have been killed by driving into wire fences at high speeds and loosing control on gravel-or sand-covered surfaces.
The Geology.com article has links to additional abandoned mine and quarry safety information.
Grace and Peace, and keep yourself and your family safe.