Flash flooding causes major damage to the Grand Canyon's critical water pipeline

WASHINGTON (AP) — The sole pipeline that supplies water for millions of Grand Canyon visitors was badly damaged by weekend flash flooding, setting up a tricky repair scenario and upending a yearslong construction project to upgrade the line laid over terrain so rugged helicopters are often required to make basic fixes.

Park officials said roughly 40% of the pipeline was damaged or destroyed. The long-term implications of the damage to the park's infrastructure , visitors and year-round residents weren't immediately clear. The 12.5-mile (20-kilometer) long Transcanyon Waterline has endured dozens of breaks in recent years. A more than $200 million repair and replacement project was well underway when the floods hit.

Caused by heavy rain, the floods killed at least two people, left more than a dozen others missing or unaccounted for and required the evacuation of more than 60 people. Officials said significant water reductions are needed — short showers, turning off the tap while brushing teeth and flushing toilets selectively to to protect the limited stored water on the South Rim, where most visitors go.

The pipeline , which was finished in the 1970s, has broken more than 85 times since 2010. It moves water from one side of the canyon, down to its base, across a bridge and back up the other side of the rough landscape. Any effort to fix a break from rock falls or flash floods is time-consuming, precarious and costly, so addressing the latest damage will be complicated.

The pipeline upgrade project, which began in 2023, took more than a decade to design, consider and fund. It involves moving the point where water would flow into the pipeline, installing helicopter pads, building water treatment facilities and replacing several miles of pipeline.

Basic decisions were complicated. For example, the original pipe was aluminum, which is lighter and easier to move into the steep canyon but is susceptible to breaking. Engineers picked a flex-steel material to balance weight with durability.

Even routine pipeline breaks force water restrictions. In 2016, a hotel on the canyon's rim that offers luxury dining and boasts about its history hosting presidents was forced to reduce dishwashing and use paper plates and plastic utensils.

The park had water conservation measure in place even before the latest bout of flooding and damage.

The flooding has forced parts of the park to close and additional flooding was possible Monday, according to the National Park Service.

“Consider changing your plans if you were going to hike, boat, or paddleboard to a slot canyon or normally dry wash. If you do still decide to recreate, check in at a nearby visitor center or ranger station,” a notice on the park website said.

Officials said previously that the repair and replacement project would ensure that the park will be able to meet its water supply needs for the next 50 years or more. The park had roughly 4.4 million visitors last year.

When the original pipeline was nearing completion in the 1960s, more than a foot (0.3 meters) of rain fell, flooding the inner canyon. That rare historic flood caused 40% of the project to be destroyed, officials said.

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