When a volcano erupts hurling millions of cubic yards of sediment onto the surrounding area and into local rivers, how does a community deal with it, and where does all that sediment go?
On May 18, 1980, 52 miles northeast of Portland, Mt. St. Helens spewed forth ash, lava, and earth. Following several earthquakes, a bulge that had formed weeks prior, collapsed and the magma in the mountain began to flow, flattening everything that it came in contact with.
The collapse triggered the largest known debris avalanche in recorded history. Mudflows, known as lahars, were a result of mud, debris, snow and ice and careened down the mountain. These lahars decimated bridges and lumber camps along the Cowlitz and Toutle Rivers.
This catastrophic event changed the landscape of the Pacific Northwest permanently. What once was a forested valley through which the Toutle River flowed, became a desolate moonscape. Today, forty-five years after the fact, trees, aquatic plants, and various forms of wildlife have returned to the area.
Amid the widespread ecological and commercial damage, proximity and speed were on the side of the U.S. Army Corps of Engineers, Portland District. The district responded, serving as one of the first federal agencies responding to the crisis onsite. Existing federal legislation provided for the Corps of Engineers to, “immediately react to emergency requirements and to initiate actions especially related to protecting lives and property,” said Terry Connell, the former Portland District Commander at the time of the event.
FORTUNATE CIRCUMSTANCES
In the weeks leading up to the cataclysmic eruption of Mount St. Helens, the mountain whispered ominous warnings—earthquakes shook the ground, steam vents hissed, and the once-dormant peak began to swell, triggering a 15-mile evacuation radius. These measures ensured there were fewer people working in the area, and there were fewer ships on the water, minimizing the loss of life. The US Geological Survey expected a vertical eruption, instead the explosion sheared off the upper top of the mountain.
A THREAT OF FLOODING
Over 200 million cubic yards — enough to fill the Moda Center five and a half times — sediment choked the Cowlitz and Toutle Rivers, and waters threatened to overflow their banks. Engineers quickly identified that an overflow of the Cowlitz would be life threatening to the downstream population of places such as Kelso and Castle Rock.
The water levels of Spirit Lake began to rise as sediment and debris clogged the natural flow, leading to a rise in water levels, creating a potential flood threat, a threat that would add to the chaos in the aftermath of the eruption. The lake was poised for disaster if water, or more debris, came into the lake, or if the debris of this newly created dam shifted, water would overwhelm the already stressed river system. Along the Cowlitz River, USACE raised levees to contain the water and prevent any debris and sediment from spilling into the surrounding areas.
“We needed to take control of the situation before things got out of hand,” Connell explained.
With the flood risk contained, the attention of USACE switched to restoring navigability of the waterways. Debris from the avalanche gridlocked the rivers, a vital source of transportation of goods and industry in the area and prevented any movement. To continue to support their efforts, USACE utilized four hopper dredges to help widen the channels and clear the waterways, three belonging to USACE and one belonging to the Port of Portland.
Within three weeks, narrow and confined travel was restored to the rivers. Within 90 days, the channel was restored at the authorized depth. Over the span of two to three months, USACE continued to increase the size of the width with supervision of the Coast Guard; a timeline that far exceeded the expectations of the agencies involved.
“The local population wanted to see results in real time, and we delivered,” said Connell.
SUPPORT AND STRENGTH
As the district commander at the time of the eruption of Mt. St. Helens, Connell stressed that the strength of the Portland District across the various departments was instrumental in the immediate response.
“The Corps was well staffed with people who were experts in their fields and had combined experience to handle the situation,” said Connell.
In addition to the strength of USACE, support also came from the Governor of Washington, Governor Dixie Ray herself an engineer, and then Senator Hatfield, who happened to be in Walla Walla at the time of the eruption.
The Friday following the disaster, President Jimmy Carter came to see the damage for himself.
“Carter asked, ‘What do you need?’ and we said money! And money is what we got,” said Connell, “900 million was allocated for this, half went to the Portland District, and half went to the Forestry Service.”
Despite the upheaval of their lives, the local populace was extremely supportive of USACE’s efforts.
“Understandably, the public were very concerned as there were unlimited unknowns,” said Pat Keogh, the Chief of Planning for the Portland District at the time.
Keogh held over 50 public meetings from June to December, with 20 of those occurring in July alone. People wanted, and needed to be informed, and took any chance they could to attend these meetings and give their input. At the initial meeting, it was expected that there could be 100 people in attendance, to everyone’s shock, almost 800 people packed themselves in a gym of a local school, as the previous venue of the auditorium couldn’t accommodate them.
During the weeks and months to follow, Portland District, in conjunction with its sister districts of Walla Walla and Seattle, helped to rebuild the area. Measures were even put in place to facilitate the flow of sediment that had accumulated, for years to come.
LOOKING BACK
Following the 45th anniversary of the eruption, a group of personnel who had been with USACE at the time of the eruption and those who helped facilitate USACE efforts years later, gathered at the Mt. St. Helens Visitor Center. The exchange of stories, smiles, and the sounds of these men and their families were almost palpable. After pleasantries were exchanged, introductions made, and a tentative convoy formation was laid out, they then traveled to the SRS to reminisce and to see what things are like now.
For Connell, returning to the site with a few of the engineers involved during the planning and construction of the SRS, it was incredibly nostalgic and brought back many warm memories of teamwork and camaraderie amongst his fellow coworkers.
For Rick Goodell, returning to the Sediment Retention System was like an alumnus visiting his alma mater. Goodell was a Deputy Commander serving as the Contracting Officer, which then oversaw all contracts for the Portland District, at the time that the SRS was installed. The eruption had happened several years before, once the immediate issues were addressed, it was time to focus on what would happen to the millions of cubic yards of sediment that were still in the river system.
The solution was the SRS—an embankment, outlet works, and a spillway—that slowed the flow of water to allow debris to settle rather than be carried downstream. Stopping the sediment further up the river was much more cost effective as it prevented further problems, and it meant the costs would be much less for dredging. It was Goodell’s job to secure funds for the construction of the SRS which were in the process of being approved by Congress and ensure those funds were authorized and used properly. Under his leadership, the construction was completed on time and within budget.
Since 1986, when he was the deputy commander, Goodell has seen USACE use the lessons it learned during the eruption and subsequent restoration, to manage other emergency situations such as the flood of 1996.
“Portland District really comes together when there is an emergency, whether it is Mt. St. Helens or the flood of 96,” said Goodell.
The eruption was not just a lesson for the Portland District on emergency response and long-term management, but one that other organizations would look to in times of their own crisis.