From Crisis to Cleanup

Wolfpack Wood Recycling Tackles Tough Spillway Site

Wolfpack Wood Recycling’s typical jobs include clearing for subdivisions and orchard removals. The site near the Oroville Dam was not a typical job.

The area near Lake Oroville in northern California had experienced one of the wettest winters on record in 2016-17. In mid-January, officials at the dam began releasing water down the dam’s main spillway, a 3,000-foot concrete chute that serves as the dam’s primary flood-control outlet during the rainy season.

Wolfpack Wood Recycling utilizes a Morbark 4600XL.

Multiple winter storms in early February caused the California Department of Water Resources (DWR) to increase the water releases to an estimated 50,000 cubic feet per second (cfs), well within the spillway’s normal capacity. Then a potential tragedy struck: a portion of the concrete gave way, opening up a large hole in the lower section of the spillway. In an effort to assess the state of the spillway, dam operators stopped the flow. Meanwhile the water levels in the reservoir continued to rise and threatened to overflow onto the emergency spillway, essentially a lip of concrete directing water down an unpaved hillside adjacent to the main spillway.

Wolfpack Wood Recycling and other contractors were called in to help clear the brush and trees from the path of the water.

“They were worried at the time that, if the water came over the spillway, it would wash all of the trees into the river, and they did not want that,” says Tim Dempewolf, owner of Wolfpack Wood Recycling.

On February 11, four days after the damage appeared in the main spillway, water overtopped the 1,700-foot lip of the dam’s emergency spillway for the first time in its 48-year history, pouring in uncontrolled sheets onto the steep, wooded hillside to the Feather River.

Wolfpack using a 4600XL on the site.

“When I first heard that the water was going to come over the spillway, [my first thought] was ‘Get my stuff out first!’” Dempewolf says with a chuckle. He had a Morbark 4600XL Track Wood Hog horizontal grinder and a 320 Caterpillar excavator on the site.

“There were three other grinding companies working on the jobsite, so there were a lot of people trying to move pretty quickly. Everyone came together to efficiently get everyone out,” he adds. “Safety was a big deal, getting everybody out and out of harm’s way, and they did a good job.”

The next afternoon, the water caused erosion of the hillside below the emergency spillway and began to cut back toward the weir of the emergency spillway. Fears the emergency spillway structure would collapse and possibly send an estimated quarter of a million acre-feet of water down the Feather River caused the sheriffs in Butte, Yuba, and Sutter Counties to order the immediate and mandatory evacuation of more than 188,000 people. The DWR increased water releases down the main spillway to 100,000 cfs, knowing it would increase damage to the structure, in order to lower the lake level and stop releasing water over the eroding emergency spillway.

Tim Dempewolf operating a Cat 320E.

“One of the key missions for California Department of Water Resources during the initial first few days of the response effort was public safety,” says Lauren Bisnett, DWR information officer. “A lot of difficult decisions were made with the understanding that, to a certain degree, the level of some of the infrastructure on the flood-control spillway would probably be lost, but it was absolutely necessary in the interest of public safety, for the community here — downstream and for those even further away.”

By February 14, the evacuation orders were lifted, and by the following Sunday, the water flowing out the main spillway had been reduced to nearly half of what it had been during the heart of the crisis. The lower flows allowed crews to use cranes and dredges to clear the debris that formed in the channel below the spillways. The debris raised water levels in the diversion pool and tailrace below the dam to the point that the Edward Hyatt Powerplant (the dam’s primary release outlet outside of flood season) nearly flooded. Hyatt could not be operated again until significant dredging and debris removal could be completed

The Cleanup Begins

Dempewolf and other crews came back for the cleanup effort — Dempewolf clearing trees and brush to make room for the piles of dirt and debris other contractors were removing from the river, as well as clearing under power lines that had to be repositioned during the crisis.

“When I first started, it was just a hurry up, try to get stuff out of the way. Now it had calmed down, the lake was lowered down; now the focus was on getting everything in order so they could start fixing the emergency spillway,” says Dempewolf. “When I came back after the damage had been done to the emergency spillway, there were four or five additional big contractors in there, and everything had been running real smooth. Everyone knew what they are doing and watched out for everybody. Safety on this job was a pretty big deal.”

“My two helpers, Buck and Hunter, they’re my Jack Russell/mini-Australian shepherd mix; they’re quite a handful, but I’m trying to teach them how to run the grinder and excavator and stuff. But that’s not going too well. They’re good company, though. They’re my little buddies.” — Tim Dempewolf

For a challenging job like this, Dempewolf said his choice of equipment is important.

“I wouldn’t buy a grinder unless it was on tracks,” he says of his Morbark 4600XL Wood Hog. “A lot of the work that I do is on hills and kind of steep ground, and if I had a grinder on a trailer, you would not be able to get around here. I purchased Morbark equipment because they have always had a good name, and I’ve had nothing but good luck with Morbark grinders.”

Dempewolf said the strength of Morbark’s heavy-duty equipment is a key feature for him. “I’ve hit some pretty big chunks of steel with my Morbark—it held up. I was doing a project last summer out of Auburn, California, on a railroad job, and I hit some parts that came out of the railroad tracks, and it got into the machine and cracked hammers and tore up screens,” he says. “But it’s not a catastrophe if I hit steel. I’ve torn stuff up hitting steel, but I have never really completely damaged the machine.”

He says the same is true for parts. “They absolutely hold up better. I’ve ordered some parts from other companies, some of them are close in performance, but Morbark wear parts hold up really well. At one point when I was just starting out, I would get my wear parts from another company, because of pricing—they were comparable to Morbark and less expensive. But now Morbark is getting their prices more comparable, and their tips are getting better—at this point, I’m sticking with Morbark parts.”

Recovery is Underway

The dam’s hydroelectric plant, which was temporarily out of service until the debris could be removed, is operating once again and is not only generating power but also offering another way to release water. Construction crews are also fortifying the emergency spillway and completely reconstructing the main spillway.

A report issued by the DWR states that its primary objectives for the area are to continue ensuring public safety and to ensure the integrity of the dam and its associated structures. The goal is to get systems in place by November 1 “that can safely pass whatever Mother Nature throws at the Feather River watershed and Lake Oroville next winter,” according to the report.

Kiewit Corp. of Omaha, Nebraska, which was awarded a $275.4 million contract to fix the dam’s two spillways, said it will had up to 500 workers on the site and worked 20 hours a day, six days a week, to get as much work as possible done during the summer.

“A lot [of the reconstruction] is underway already with more to come soon,” said Bisnett at the time. “The timeline we are currently working on is that construction will begin this summer and that will be to repair/replace the upper and lower chute of the flood control spillway, and that’s expected to continue into 2018, if needed — and that pertains to the emergency spillway as well. We’ll continue to reinforce and use new design criteria and new standards for design and construction, and we’ll be using a lot of state-of-the-art materials as well as paying attention to seismic concerns and things like that. It’s an opportunity to re-examine some of those things while we are going in to reconstruct.”

According to an August 9, 2017, news release from the DWR, demolition, excavation, and site preparation were 99 percent complete for the 2,270 feet that will be reconstructed this year. Crews reached a major milestone in early August by placing the first structural concrete slabs, which include reinforced steel, on the lower portion of the spillway chute. Now that progress has been made on excavating trenches, drilling bore holes, and placing concrete, DWR has a clearer schedule for construction of the underground cutoff wall, with a target completion date of late December 2017 or early January 2018.

For the most up-to-date information on the spillway incident and recovery plan, please visit www.water.ca.gov/oroville-spillway. 

This story is dedicated to Karen Wilson, wife of Tim Dempewolf, who passed away April 9, 2017, from injuries sustained in a car accident.

The Dam

Spillway at Lake Oroville.

Completed in 1968, Oroville Dam is an earthen dam and is the tallest dam located in the United States, measuring over 770 feet (235 m) high and 6,920 feet (2109 m) across. The dam was the largest earth-fill dam in the world until succeeded by Aswan High Dam in Egypt. It was built by the California Department of Water Resources as part of the California State Water Project. The dam houses the Edward Hyatt Powerplant, an underground hydroelectric plant that was completed in 1967. Six generators are used to provide a maximum generating capacity of 819 MW.