A large sinkhole opened quickly Feb. 15 on Old County Road just across the street from the Rockland Golf Club, effectively closing the road until repairs can be made.

The hole, more like a pothole, was first noticed by a driver at approximately 4:30 p.m. and the Rockland Fire Department was notified. By the time firefighters arrived, the hole had begun to grow, and as it grew, the sounds from beneath the road sounded like waves crashing onto rocks.

“It sounded like Thunder Hole,” said Rockland resident Valerie Wass, who along with her husband, Eric, had traveled from Rockland on Old County Road to a job site where their company was working. Thunder Hole is on the shore of Acadia National Park and when the seas are rough there the waves crash into the rocks with a roar.

At the Old County Road sinkhole, the diameter of the eroding road increased quickly until it measured more than 25 feet, enough to park three large sport utility vehicles inside. Firefighters, who carefully stepped closer to the edge of the pavement with flashlights, estimated the hole to be approximately 50 feet deep.

By 6:30 p.m., the sinkhole was still making intermittent and threatening sounds.

The hole began in a dip in the pavement of the road as it curved around an old limestone quarry. The area in the golf course region is home to a network of old quarries that once were mined for the limestone that was shipped in casks to New York and Boston through the 1800s. A productive vein of limestone was discovered from Camden to Thomaston, and the Midcoast is peppered with old quarries.

Old County Road runs adjacent to one of the quarries, and at that corner, the road ran right over a quarry cave. It is believed that an old tunnel or roadway, possibly connecting another quarry to the west, lies beneath Old County Road contributing to its current instability. When the firefighters peered into the hole it stretched more than halfway across the road.

By 6:30 p.m., a crew from Rockland Public Works was busy erecting barricades so that any drivers attempting to bypass the road detour would not stray close to the hole. Rockport police had closed the eastern end of Old County Road where it intersects Route 1, and Rockland police were diverting traffic from the western end of the road where it intersects Route 17.

The road will remain closed until further notice.

VillageSoup/Herald Gazette Editor Lynda Clancy can be reached at 207-236-8511 or by e-mail at lclancy@villagesoup.com.