Water was rushing over the spillway of the Guajataca Dam on Saturday, having eroded part of it and the land around it. In addition to cracking the dam, the hurricane brought so much water that patches of concrete in the area that normally contains the overflow had collapsed, said Miguel Abrams, the emergency management director of Quebradillas, a nearby city that was also told to evacuate.
“There’s normally a street there,” Gabriel Soto said, referring to a submerged road alongside the dam. He took pictures of the water before going to check on relatives who live nearby.
The Guajataca Dam is 120 feet high and nearly 1,000 feet long, built in 1929 by the Puerto Rico Electric Power Authority. It lies across the Guajataca River, forming a reservoir that can hold about 11 billion gallons of water that is used for drinking, irrigation and power generation.
“This is a serious situation because that’s our drinking water,” Mr. Abrams said. “Seven or eight cities depend on that lake to drink.”
The dam is in the middle of hilly rural neighborhood with curvy roads and steep ridges overlooking the water. A few miles away a maroon sedan that had been caught mid-mudslide hung precariously above the road.
The swelling waterway was such a spectacle that people gathered at the washed-out road and along the ridge to watch. The backyards of many houses abutted the ridge, but the residents there said they felt safe because their houses sat a few dozen yards above the water.
Some of the homes looked stately. Others were submerged.
Water levels have risen significantly, which added to the danger. Another storm system, Lee, was expected to douse Central Puerto Rico in the coming days, which could worsen an already precarious situation.
“Since the ground is already saturated, we don’t know how nature will work,” Mr. Abrams said. “This is a lot of water.”
But he stressed that the ridge that surrounded the dam was 300 to 500 feet high, which protects the vast majority of the…