Using excavators, the crew sorts through huge piles of rocks and puts them together like puzzle pieces.

Rocks are buried in the ground in long rows to block water flow and slow or widen it, or line the channels of streams to reduce erosion.

But how each rock fits is important, Garrison said, so the pieces of the puzzle can hold onto each other.

“We play Tetris, the biggest game in the world, and that’s exactly what we do,” Garrison said of the three men working in the creek on a hot Friday afternoon. He said, gesturing to the team.

“There’s Jeff.” [excavator], he has a bunch of stones here. He takes the first stone, the so-called throat stone, and then begins sorting. He sort of laid out four or five stones and made a plan,” Garrison said. “The people doing this are really artists. He has about six that specialize in these structures.”

Garrison said he hopes to complete the project by the end of the week before the onset of monsoons creates challenges for the project.

The work was done in response to the start of post-fire flooding in the wake of last year’s pipeline fire, which affected much of the West Flagstaff area.

However, for the amount of work done within the lower Schultz Creek basin, the landscape is remarkably similar to what it was before construction began.

This is largely the result of the project’s new technology rather than traditional fan creation, said County Flood District Manager Lucinda Andreani.

According to Alan Hayden of Natural Channel Design, the new method, called “plug and spread,” slows down the water, spreads it out, and releases sediment from it, while largely preserving the surrounding environment. can be dropped.

“Of the 3,000+ trees we counted in this work area, we probably only pulled 30 at most. I’m a little excited to find out,” he said.

The company, like Tiffany Construction, has been working on flood mitigation in the county for decades. Interestingly, Hayden said this method is more commonly used to restore wetlands and meadows.

In fact, this technique was used in a portion of the Coconino National Forest near Clint Wells to do just that in areas affected by overgrazing.

“Obviously, we are trying to do this.” [use the technique] Much more discharge is now possible than ever imagined in any application. So we raised the bar on rock size and did an awful lot of engineering,” Hayden said.

Hayden said 13 dams have been built across the former Schultz Creek Trailhead area that not only cut off the waterway, but also extend hundreds of feet across the valley floor, just about a few feet from the valley’s natural floor. It is said to reach heights of 0.5 feet. .

The dams, built by digging large trenches and ‘Tetris’ rocks into them, are expected to be nearly invisible in the valleys once the vegetation begins to grow again.

Its few inches in height is enough to create the desired influence on the flow of water.

“It pushes the water up, spreads it around, slows it down, and the seals on the sides keep it from moving back up and cutting new pieces.” [channel] around your structure. ‘ said Mr. Hayden. “If it works, as the math shows, we’ve got a new tool that we can use in areas that aren’t very noisy. Perhaps this won’t be the last fire, so this will be very useful going forward. ”

And this is very different from the appearance of other alluvial fans created by the county for similar purposes. Instead, traditional infrastructure reminds us of lunar landscapes.

“Our usual approach to alluvial fan restoration for post-fire flooding is to level everything and use a bulldozer to surface the alluvial fan because there is usually no trees left. They’re all dead, they have burnt sticks and they’re not worth much,” Hayden said. “On the other hand, we have a huge amount of trees here that are used for recreation, wildlife habitat and all sorts of other uses.”

Andreani said the plug-and-spread technology will be a new and important tool in efforts to mitigate post-fire flooding across the county. This technique will likely also be used on the other side of Flagstaff within the government tank basin, which county officials are considering addressing. Flood problem in the area west of Route 89.

Still, she says the technique doesn’t obviate the need for more traditional alluvial fans.

“In fact, it all comes down to engineering and what is dictated by the state. [terrain] It’s just the type,” Andreani said. “So it’s not applicable everywhere. But if it is possible, we think it will be an important tool in the toolbox.”

Work on the plug-and-spread infrastructure within Schultz Creek should be completed this week, but this only marks the completion of the first phase of work within the basin, Andreani said.

Work further up the stream will begin this fall and early this winter, he said, in hopes of stabilizing the slopes and reducing sedimentation in the first place.

The county’s flood control district is expected to spend a total of $5 million to $6 million on construction within the Schultz Basin, equivalent to about $90 million worth of flooding to other areas affected by the pipeline fires. Part of a mitigation project.