Spillway Failure and Possible Collapse of Guajataca Dam, Puerto Rico

Mick West

Staff member

Source: https://twitter.com/ABC/status/911685598070452224

This story is interesting because of some similarities to the Oroville Dam situation. Heavy rains cause a badly built spillway to be used. Erosion ensues. Except in this case there a greater chance of the dam actually collapsing.

Here there's been mixed messages about how many people are in danger. The Tweet above says 70,000 people, however looking at the river on Google Earth, the path to the sea seems to be in a really deep ravine
In most places the walls of the ravine are over 200, getting below that only near the sea. The only houses I can see that are in danger are those right at the river mouth by the ocean, and those in the valley directly under the dam.

Obviously you would want to err on the side of caution. But presumably local officials have a plan on inundation areas in case of a dam breach. A mad scramble of 70,000+ people more than is needed would be unfortunate.
A better story:

“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 homes nearby. Only the neighborhoods in lower areas were in danger of flooding.

Mr. Abrams said only about six households were evacuated from Quebradillas, on the other side of the river. A 2015 study showed that if the dam ever broke, it would be Isabela that flooded.

Even as Juan Morales, the public safety director for Isabela, managed a mandatory evacuation of low-lying areas, he sought to calm tensions.

“These have been preventive evacuations,” he said. “The idea that the dam is collapsing is totally false. There has not been an evacuation of 70,000 people, also totally false. Please calm people. There isn’t a breach, and 70,000 people aren’t going to die.”

Mr. Morales was referring to the number of residents that Gov. Ricardo Rosselló said could be affected by a break in the dam. After the National Weather Service of San Juan announced the breach on Friday afternoon and issued a flash flood warning for Isabela and Quebradillas, the governor, citing the figure, ordered the municipalities to evacuate.
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The ridge they are referring to surrounds the river downstream of the dam. It is indeed remarkably deep, and the Quebradillas (east) side is 100 feet higher than the Isabela (west) side.
Lots of photos here:
Governor Ricardo Rossello said on Friday that some 70,000 people living in the area threatened by the collapse of the Guajataca Lake Dam were being evacuated, but municipal officials suggested on Saturday that there were not as many people at risk as previously thought and that only some 320 people had been taken to safe areas, local newspaper El Nuevo Día reported.
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I think it's important to note that most of the the flow of water we see is NOT the dam leaking. It's essentially just the Guajataca river after heavy rainfall. The dam is full, so anything that flows into the dam just flows right out over the spillway.


However there is a broken 3' pipe in the "waterfall" area, that looks like it went to a hydro/pumping/treatment station. Possibly the source of some of the region's drinking water.


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Still lots of no-information "dam fails, thousands in danger" stories, but here's perspective from a local official

Mayor of Quebradillas accuses the government of causing hysteria

The mayor of Quebradillas Heriberto Vélez said that the state authorities have created a climate of hysteria in their municipality, taking out of proportion the effect that the Guajataca dam collapse would have on the people.

Although the road to Quebradillas is passable, Vélez said that no official of the state government has sought to discuss the danger of a break in this dam that has damaged its structure.

"They say it's going to flood the (PR) 113, the Roman and several neighborhoods here, and that's false," said the municipal executive. "That water is never going to get here. Those are (areas of) mountains and huge basins, "he added.
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Quebradillas, Puerto Rico, April 24, 2018 – During an aerial tour of Puerto Rico, staff members from the U.S. House Committee on Oversight and Government Reform observe repair work on a spillway of Guajataca Dam, which was compromised by Hurricane María on September 20, 2017. FEMA partners with other federal agencies, the state, local communities, counties, municipalities, volunteer organizations active in disaster (VOAD) and tribal entities to provide assistance to disaster survivors and local communities. Photo by Christopher Mardorf / FEMA.

Photo by Christopher Mardorf - Apr 24, 2018 - Location: Quebradillas, Quebradillas
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QUEBRADILLAS, Puerto Rico, January 19, 2018 - Part of the Guajataca Dam collapsed after the impact of Hurricane María in Puerto Rico. Members of the U.S.Corps of Engineers (USACE) installed a system of water pipes that regulate water levels and at the same time allows the distribution of water service to residents of the West Coast area. Eduardo Martinez/FEMA.

Foto por Eduardo Martinez - Ene 19, 2018 - Location: Quebradillas, PR
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