Sonoma County Airport Stages Latest Overnight Repairs, Addressing Aging Culvert, Pavement Problems

Jun. 25—After months of planning, construction crews and engineers on Tuesday executed what some officials described as a "surgical" operation to repair deteriorating sections of the main runway at Charles M. Schulz-Sonoma County Airport.

The repairs were meant to resolve, at least for now, areas of deteriorating runway pavement identified by federal aviation officials in January, as well as safety concerns that have been raised by the airport's own operations specialists for more than a year.

The work, which began Monday at 11 p.m., forced the closure of Runway 14/32, which is the principle airstrip used by commercial air traffic. Throughout Tuesday, commercial flights used the airport's shorter, alternate runway.

The extensive repairs included replacing a failing World War II-era culvert underneath the northern end of the runway and a concrete-encased electrical conduit on the southern end that had caused pavement to sink around it.

The work, scheduled to conclude at 7 p.m. Tuesday, capped a frantic month of repairs on the runway, including three rounds of emergency patchwork that also required the runway to close for shorter periods.

By Tuesday morning, most of the 84-year-old culvert had been replaced.

"It was fast. It was like watching an orchestra," said Johannes Hoevertsz, director of the county's Department of Public Infrastructure, which oversees the airport.

The corrugated metal storm drain — buried 13 feet under the runway — was long past its life span.

Nearly a month before the scheduled work, several sinkholes appeared on the runway pavement above the failing storm drain, forcing airport officials to order overnight emergency repairs three times in a six-day period.

Inspections showed parts of the decades-old culvert had corroded and buckled, causing the metal pipe to sink and destabilize the earth above it. That deterioration caused voids to appear below two layers of runway pavement in a stretch of the runway where commercial and general aviation flights touch down.

In January, the Federal Aviation Administration ordered county officials to repair the culvert following the federal agency's annual inspection of the airport. In March the airport announced plans to complete the work in June and described officials' efforts as "proactive."

But some airport operations and safety employees have been raising concerns about the condition of the runway as far back as late, 2022, a Press Democrat Investigation found in April.

An Alaska Airlines flight lands on the Sonoma County airport's secondary runway as crews work on a failing culvert underneath the main runway. It's the first commercial arrival of the day pic.twitter.com/ycgN073awa

— Emma R. Murphy (@MurphReports) June 25, 2024

The repairs on the two sections of the main runway were expected to take 20 hours. Representatives of Alaska, United and Avelo said Monday and Tuesday they expected no impact on their flight schedules.

"Our crew used another available runway for operations departing and arriving STS to avoid impacts to our flight operations," Madison Jones, communications manager for Avelo Airlines wrote in an email.

"Avelo is working closely with the airport to continuously monitor field conditions," she said.

On Tuesday morning, the day's first commercial flights were departing from the alternative runway at about 7 a.m. The heavy construction equipment and crews on the main runway were visible to passengers as the planes lifted off.

The first arrivals were about two hours later. By that time, crews were tamping down the soil over the new culvert.

Hoevertsz said the repair work went off quickly and without any problems.

Timeline of failing runway pavement at the Charles M. Schulz-Sonoma County Airport

* 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 work kicked off Monday night with a management/contractor meeting at 9 p.m., he said. Excavation started at 11 p.m. and by 2 a.m. workers had dug down to 13 feet and started pulling out the old culvert.

By 3:30 a.m. the culvert had been completely removed. By 4:30 a.m., crews were back filling soil. Hoevertsz said he noticed no voids or cavities in the earth during the work.

Voids that formed from rusted and sinking sections of the culvert had been responsible for pockets of empty space forming just under the runway. Those voids caused potholes to form in late May and earlier this month.

At the southern end of the Runway 14/32, crews milled or ground down a section of sinking pavement where an underground electrical conduit traverses the runway. The uneven pavement resulted in standing water during periods of heavy rain.

Monday and Tuesday's repairs, estimated to cost $667,115, address areas of the runway impacted by the culvert and conduit.

Most of the runway, however, has not been repaved since 2001.

A major repaving job, estimated at $42 million, is at least four years off, officials say.

You can reach Staff Writer Emma Murphy at 707-521-5228 or [email protected]. On Twitter @MurphReports.

You can reach Staff Writer Martin Espinoza at 707-521-5213 or [email protected]. On Twitter @pressreno.

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