Police in Ocean County are stepping up their patrols to keep people out of a massive former mining site in Manchester.

News 12 has reported on multiple drownings there over the years.

"Fatalities, I’d say we average about two a season,” said Michael Eden, of the Ocean County Office of Emergency Management. “As far as calls for service, every weekend. The most recent incident was a fire caused by a careless campfire, which burned a couple of acres there.”

What’s known as “Crystal Lake” in Manchester is not actually a lake. Police say it is a groundwater aquifer with sudden drop-offs up to 90 feet deep. The land on the ASARCO site was mined up until the 1980s.

“Because of the mining, it has very steep banks, and it’s subject to unexpected collapse,” Eden said. “People can go in there, walk in there, and get pulled down and not be able to get out because of the unstable banks.”

The hazards extend beyond the water. The 7,000-acre property, which stretches from Route 70 to Route 37, has become popular for off-roading. The land is clearly marked as private property.

“Unfortunately, there’s so many access points and it’s such a large area, that they chase people out, they leave and they come back,” Eden said.

Starting last weekend, police have increased patrol numbers. The property managers have also installed a new access gate and dug trenches and placed trees to keep people from cutting through. Police say residents have also made noise complaints about the trespassers.

Those who are caught trespassing face a fine and up to six months in jail, and can have their vehicles impounded.

“Go to those places where you can be, and you’re covered by insurance, and you’re not breaking the law,” Eden advised.