Using jackhammers, diamond-blade road saws and shovels, construction workers broke through the first layer of asphalt at Charles M. Schulz-Sonoma County Airport’s troubled main runway.
Small patches of loose gravel were the only signs of something worse below the tarmac. Cement Hole Saw
It was Tuesday, June 4, and the runway had been closed for a third time in less than a week for emergency patchwork.
After busting through the second layer of pavement and clearing heavy chunks of asphalt, workers discovered large cavities inches below the runway’s surface.
Where there was supposed to be base rock and earth sat only dark, empty space.
Thirteen feet below lay the problem behind the failing concrete and sinking substrate: an 84-year-old culvert, installed at the start of World War II, buckling on the inside and collapsing in places where it crossed under the runway.
As the black voids became visible during repair work that night, Public Infrastructure Director Johannes Hoevertsz, who oversees the airport, moved closer to pounding jackhammers. He fixed the beam of a small flashlight on the gaps while others hovered to get a closer look.
For decades, the corrugated metal culvert transported stormwater under the north end of Runway 14/32, the airport’s longest and busiest strip, used by commercial and private traffic.
The culvert’s advancing age was a concern — prompting at least two inspections since September — but the extent of its sudden breakdown was unknown until early last week.
In August, airport crews began to report depressions, cracks and crumbling pavement on the runway’s surface, a sign that the culvert was failing or starting to fail.
On the southern end of Runway 14/32, problems with standing water — a sign of sinking asphalt — were documented by airport staff as far back as December 2022.
A “proactive” repair, announced by the county in March, was scheduled for June 24 after federal aviation officials ordered the county to address known problems.
But the aging culvert could no longer abide the slow pace of bureaucracy, and on the evening of May 30, airport officials found a sinkhole roughly the size of a basketball within about 10 minutes of the day’s last flight.
That discovery prompted the first in the recent trio of overnight closures for emergency repairs. The runway remained closed for emergency patchwork through the following morning and into the early afternoon, leading two inbound Alaska Airlines flights to divert to other airports.
Even after the appearance of that May 30 sinkhole, county officials addressed the runway conditions as a routine issue, deflecting concerns raised for over a year by airport operations and safety employees, as first outlined in a Press Democrat investigation in April.
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Board of Supervisors Chair David Rabbitt, in a May 31 interview with Press Democrat reporters, repeatedly denied the detected runway failure was a sinkhole, insisting “there was no hole.”
The county, in a garbled social media post the same day, described it as a “limited section of degraded pavement with some depressions and separations.”
But county photos obtained Wednesday through a public records request clearly show the hole described by Stout.
When another sinkhole appeared June 3, in the same area above the culvert, the escalating problem was undeniable.
Airport and county infrastructure officials assembled a team of engineers, construction crews, pavement trucks and ground-radar teams to assess the extent of the damage.
Last week, over the course of about four hours late Tuesday into Wednesday, they set about making swift repairs.
The work capped a frantic span of days for the growing airport, which just last month added three new direct flights and a hub for Houston-based Avelo Airlines, with more destinations than Alaska Airlines, long Sonoma County’s dominant carrier.
Airport Manager Jon Stout said the closures represented the first time during his 22-year tenure that a failing culvert has impacted the runway. Otherwise, he said, runways are “routinely” closed for maintenance, striping, rubber removal and crack-filling, often for multiple days in a row.
No aircraft reported damage or difficulty navigating the runway due to the holes, airport officials said.
During a Board of Supervisors meeting Wednesday, Rabbitt sought to defend the county’s response and downplay safety concerns about aging runway infrastructure, calling up Hoevertsz, the infrastructure director, for a short round of questioning about recent repairs.
Rabbitt pointed out that federal aviation officials have the final say over safety.
“At the end of the day, the FAA is the ultimate arbitrator at the airport of what is safe and not safe, not labor groups and not the newspaper,” Rabbitt said, just before Hoevertsz provided an update on recent runway repairs.
Hoevertsz minimized the extent of the failing culvert and its impact on the runway.
“The culvert is failing, slowly,” he said. “It’s corroded … but it’s not collapsed, there is no sinkhole,” he said.
But an airport infrastructure expert and the union representing airport safety crews said the problems should have been given greater priority long ago given the evident sinking of the runway surface and earlier reports of crumbling tarmac.
“For the pavement to be sinking means there has to be a void underneath that has to be going somewhere. Where is that?” said Augustine Ubaldi, an airport and railroad civil engineer with Robson Forensic.
* On Dec. 10, 2022, airport operations specialist notice standing water on the south end of Runway 14/32, caused a by concrete-encased electrical conduit that runs across the runway, according to internal airport emails.
* On Jan. 6, 2023, a senior airport operations specialist sends an email to airport officials alerting them that the main runway pavement near the electrical conduit was “starting (to) fail,” and that the area had “gone downhill fast!”
* On Aug. 22, 2023, airport staff report that “depressions” have formed on the runway, which were being flagged by general aviation pilots, according to an internal airport email.
* In September 2023, airport officials send a robotic camera-equipped crawler through the culvert. The camera is able to pass all the way through the culvert underneath Runway 14/32.
* On Dec. 7, 2023, a senior airport operations specialist emails airport officials that the pavement near the culvert is “degrading faster than anticipated … and it really hasn’t started raining yet.”
* On Jan. 12, 2024, a safety inspector with the Federal Aviation Administration conducting an annual inspection orders repairs on runway pavement above the culvert, to be completed by June 1. The airport later gets an extension of a few weeks.
* On March 15, 2024, the day after The Press Democrat’s interview with Airport Manager Jon Stout and County Infrastructure Director Johannes Hoevertsz regarding runway problems, the county issues a news release announcing planned repairs on the runway. County officials describe the airport’s response to the FAA’s findings as “proactive.”
* Sometime in late March or early April, airport officials again deploy a mobile camera through the 84-year-old culvert. Corrosion is detected but officials said they’re able to get the mobile camera through the entire length of the culvert under the runway.
* On May 30, a Thursday, the runway is shut down for 16 hours, starting at 10:30 p.m. to 2 p.m. the next day, as airport officials scramble to get construction crews out to repair a basketball-sized sinkhole and uneven pavement on the northern end of the runway above the culvert. Ground penetrating radar is used and other anomalies are detected.
* On Monday June 3, between 10:30 and 11 p.m., another sinkhole is detected after airport staff conduct a “deflection test” by driving a truck over the culvert. The runway is shut down and the hole is patched. Plans are made to execute a more extensive repair the following evening.
* On Tuesday June 4, the runway is closed by 10:30 p.m. to allow, construction crews to conduct the most extensive emergency repair on deteriorating runway above the failing culvert. The work, combined with previous repairs, involves filling voids or cavities in the ground with slurry, leaving a patch of concrete more than 100 feet above the culvert. Crews finish work by 2:30 a.m. June 5.
* June 24-25. The runway is scheduled to be shut down for close to 20 hours to allow a full replacement of the failing culvert. Uneven pavement on the southern end of the runway also will be addressed. The cost of repairs is expected to total $667,115. The work is scheduled to start at 11 p.m. on June 24 and conclude at 7 p.m. on June 25, Stout said.
The last plane to use Runway 14/32 before it was first closed two weeks ago touched down on the northern section of the runway near minutes before the first sinkhole was discovered.
That May 30 flight, Alaska flight AS2250 from Seattle, the final commercial flight of the night, landed at 10:18 p.m.
Twelve minutes later, Stout discovered “a hole” on the runway. County officials, in emails obtained through a public records request, said the hole spanned 12 to 18 inches — larger than the diameter of a basketball.
It was not detected during an earlier inspection of the runway that evening.
He spotted the sinkhole after the night’s last commercial flight when he was escorting a small team onto the runway for a pre-scheduled survey of the area around the culvert.
A subsequent survey of the spot using ground penetrating radar detected three subsurface holes, or voids, and two areas that appeared as anomalies. The discovery prompted a scramble to get a construction crew and find a concrete plant able to deliver to the airport in the early morning hours.
“My standard is, will I put myself and my family on that runway?” Stout said. “And the day I won’t is the day it’s closed.”
With the runway closed that Thursday night into Friday, crews raced to fill the voids with slurry and marked the location of the anomalies on the surface of the runway to track their progress.
Stout said the repairs used six cubic yards of concrete; standard concrete trucks typically hold eight to 11 cubic yards.
The runway reopened for air traffic 16 hours later after being cleared by the Federal Aviation Administration with a caveat: They required inspections every time a commercial flight traveled over the problem area.
Hoevertsz and Rabbitt, as board chair, sought to reassure the public the runway was safe and would hold until the culvert’s replacement at the end of June.
On May 31, a Friday, after the emergency repairs were done, Hoevertsz said, “I have peace of mind.”
That confidence was evident in an email Hoevertsz sent to Supervisor James Gore and other county officials Sunday afternoon. The email was in response to an email Gore had sent that morning asking for an update on the first repairs.
Gore, who shared the correspondence with The Press Democrat, had voiced disappointment over the need for emergency repairs after being “assured that the runway was sound.”
Hoevertsz, in his response, said the failing culvert was not “catastrophic.” He added that such failure would result in “visible signs of pavement collapse and sinkholes, which we do not have.”
Hoevertsz said he had invited The Press Democrat to visit the repair site on Monday afternoon.
“Understanding that the media will continue to sensationalize this story to satiate the need for drama, it would be beneficial for the reporter to see the site as well to understand the difference between sinkhole, depression, and voids underneath pavement,” Hoevertsz wrote.
By Monday evening, however — hours after The Press Democrat visited the site — another hole appeared on the runway.
This time the tarmac gave way after an airport operations employee drove a truck over it to test its integrity, county officials said.
The new hole prompted another overnight closure as construction workers patched the hole using about 240 pounds of non-shrink, quickset grout, Stout said.
After the appearance of that second sinkhole, Stout and Hoevertsz decided they needed to dig up more of the runway to take a closer look at the underlying problem in that area of the runway.
The next night, Hoevertsz, Stout and a few county employees gathered in the conference room at the airport management office.
Hoevertsz paced the room, energized by his BottleRock-inspired playlist, featuring Pearl Jam and Maná, playing in the background.
Just after 10:50 p.m., the group piled into Ford fleet trucks and formed a caravan with engineers and construction workers. The team of experts included technicians from Roy’s Sewer Service who were equipped with a remote controlled sewer crawler that would carry a camera through the culvert.
They were finally going to get eyes on the suspected cause of the sinkholes — the failing culvert — and they were clearly excited about it, swapping theories about its condition.
“You got to do this. You got to face the music, and I love that part of the job,” Hoevertsz, an engineer, said as the sewer technicians dropped the mobile camera into a catch basin on the east side of Runway 14/32 and steered it down the culvert.
Minutes later, standing around a screen set up to show the camera’s live video feed, the group swapped occasional jokes — about colonoscopies and finding an alligator or the clown from Stephen King’s “IT” lurking in the storm drain.
The only movement came from a few mice.
The camera made its way through several inches of water, revealing evidence of corrosion here and there before it stopped at a point about 119 feet from its entry point in the catch basin, directly below where the pavement had begun to deteriorate.
In the culvert, shards of corrugated metal were protruding upward from the bottom of the pipe. The technicians compared them to shark’s teeth.
The images showed what looked to be complete corrosion of the culvert’s bottom, metal giving way to the force of the earth above it, and all of the circular pipe compressing downward, destabilizing layers of ground beneath the runway.
The metal shards and debris blocked the camera from going any farther — unlike an earlier inspection in late March or April, when it had been able to travel the full span under the runway.
The partial inspection provided a full enough picture for the field inspectors, however, and left no doubts for an outside expert who reviewed the footage on behalf of The Press Democrat.
The corrosion was far enough along in the worst section of culvert to cause the pipe structure to collapse and leave voids in the ground above it, said Ubaldi, the airport and railroad civil engineer, who reviewed the video at newspaper’s request.
“Corrugated metal, it’s going to rust,” he said. “At some point you need to every now and again pay attention to it and say, ‘What is it’s condition.?”
“Anything like that you want to avoid a catastrophic failure,” he said.
Working into the early hours of Wednesday morning, a construction crew began using diamond-blade road saws and jackhammers to cut out 12-to-18 inch trenches on the surface of the runway, along the path of the culvert.
Combined with the previous trench-and-fill work, the repair work stretched about 100 feet on the west side of the runway.
When the large cavities were revealed, one construction worker poked the handle of a shovel into the void to determine how extensive it was. The dark cavities spread on either side of the trenches, making it difficult to gauge their depths.
“We were treating the symptoms,” Hoevertsz said, looking on. “I think we now found out what the disease is.”
In retrospect, Hoevertsz and Stout said they wished that work had been done days earlier, May 31, after the first hole appeared.
Stout said the decision not to dig up the area at that time was based on the ground penetrating radar showing only anomalies, not clear voids, and the belief that the slurry being pumped into the other voids would address the issue.
Had he seen the problem with his own eyes as crews began to work, Stout said he would have had them dig more extensively. He had stayed through much of the night to coordinate the emergency repairs but left at 4 a.m. that morning before the cement trucks arrived.
Hoevertsz said he did not want to “second-guess” any decisions but added that he would have preferred having more complete work done sooner.
“If you have the airport closed and you have the tools out there, I would have done the whole thing,” Hoevertsz said.
Constructed just before World War II on 339 acres outlying northwest Santa Rosa, the Charles M. Schulz-Sonoma County Airport was initially used as a military airfield.
The U.S. Fourth Air Corps trained fighter groups and squadrons at the site from 1943 to 1946. After the war it resumed operations as a civil airfield and underwent some growth through the 1960s, ’70s and ’80s.
Today, the airport offers service from three commercial airlines — Alaska Airlines, American Airlines and Avelo Airlines — with 15 nonstop destinations by May, as well as a newly renovated, $40 million terminal.
In 2023, it served a total 641,178 passengers. Avelo’s new hub could bring even more.
The airfield has two runways, with only one, Runway 14/32, capable of handling large commercial aircraft. That runway also is the site of many of the airport’s current infrastructure problems.
The emergency repairs over the six-day period are estimated to cost about $45,000, Hoevertsz said.
That money is part of contingency funds attached to more extensive repairs scheduled for later this month. The work also includes fixing a “speed bump” caused by pavement sinking on either side of an underground, concrete-encased electrical conduit that runs across the runway.
Over last weekend, airport staff discovered chipping along a crack near the conduit and a one-inch depression in the pavement. Stout said spot is being monitored and the pavement chipping does not require the same emergency repairs that were recently done on the north end of the runway.
That next round of repairs, to replace the failing culvert, is expected to total $667,115 and will require the runway to close for 20 hours. That work is scheduled to start at 11 p.m. on June 24 and conclude at 7 p.m. on June 25, Stout said.
“We’ll have four times the crew and equipment, just a bigger orchestra,” Stout said.
He called the June 4 repairs a “good rehearsal” for the project.
Both Stout and Hoevertsz said they were confident the repairs would hold until the culvert replacement.
“All we need here is 19 days,” Hoevertsz said.
But the work being done later this month is just the beginning of required maintenance. The majority of the runway has not been repaved since 2001 and officials say that major repaving, with an estimated cost of $42 million, is at least four years off.
You can reach Staff Writer Emma Murphy at 707-521-5228 or emma.murphy@pressdemocrat.com. On Twitter @MurphReports.
Circular Saw Blade You can reach Staff Writer Martin Espinoza at 707-521-5213 or martin.espinoza@pressdemocrat.com. On Twitter @pressreno.