(KFYI News) – Phoenix Parks and Recreation workers are working at top speed to restore areas damaged by Tuesday night's deluge of rain on South Mountain.  A large rock slide has closed the Central Avenue entrance to the park, and the main summit road, indefinitely.

Parks & Rec spokesman David Urbinato says the rain was so heavy that "it washed down boulders, rocks, full-grown palo verde trees... we estimate six to seven feet deep at one point, completely blocking the summit road and stranding vehicles higher up on the summit road."

He says the terrain and heavy rain provided, literally, the perfect storm.  "A lot of very steep terrain so there's a lot of natural funnels and ravines and canyons where that high volume of water could drain into."

"This was just of a scale that no one had ever seen," Urbinato added.  "Just the sheer volume of the rock slide was beyond even what many long-time rangers had ever seen at the park."

By late Wednesday morning, crews had managed to clear one lane of the summit road so that people whose cars were stranded above that point could drive them down.  The occupants of those cars had to be rescued by the Phoenix Fire Department since they couldn't drive to safety.

Once the debris is removed, the city will need to inspect all roads to make sure the roadbeds are still intact and weren't undermined by the storm runoff.

PHOTOS: Courtesy of Phoenix Parks & Recreation.