Sonoma Airport Facilitates Regional Jet Service While Meeting Runway Safety Area Deadline

When Charles M. Schultz-Sonoma County Airport (STS) completed a $55 million runway expansion and improvement project last November, it not only met the congressionally mandated December 31, 2014, deadline for runway safety areas (RSAs) at Part 139 airports, it also added enough runway length to help attract regional jet traffic - a benefit offering long-term growth opportunities for the California wine country airport.

"We've had that goal (adding regional jet service) since the 1990s," explains STS Airport Manager Jon Stout. "Carriers were saying they wanted to use regional jet service in our market, but they couldn't do it on a 5,100-foot runway."

Complicating matters, STS's two runways shared a common end point and needed to be decoupled for safety reasons. To accomplish both goals, STS and engineer of record Mead & Hunt originally devised a plan to extend the airport's primary runway, 14-32, by 750 feet and its secondary runway, 2-20, by 200 feet, which would place its end just past 14-32. 

That design had problems, though. "Although 14-32 would be out of 2-20's safety area, the runway end wouldn't have any taxiway connection out of the safety area, and we wouldn't be able to have dual runway operations," explains Stout. "We were able to convince the FAA that by adding an additional 150 feet to 14-32, we could add two taxiway connectors outside the RSA and thus maximize utilization of both runways."

The revised and approved plan also brought STS's primary runway to 6,000 feet - the length needed to attract regional jet service.

Easier Said Than Done

With the big-picture design complete, a long list of specifics had to be worked through:

• extending two runways;

• constructing a partial parallel taxiway for 2-20;

• constructing entrance and exit taxiways for 14-32;

• constructing two new taxiways for 2-20;

• reconstructing an existing taxiway;

• grading the safety areas for both runways;

• constructing new run-up aprons for both runways;

• realigning a creek and installing a culvert under the Runway 14-32 safety area; and

• constructing detention basins and a retention structure for airfield drainage

If that were not enough, one runway had to remain in operation throughout the project; and all work needed to meet complex environmental standards and be completed within a compressed timeframe.

Scott Van Gompel, a Mead & Hunt engineer, describes the scheduling challenges: "The project was originally slated to be completed over a season and a half. For various reasons, including funding and environmental clearances, work was condensed into basically one season. Our plan was to start work in August 2013, but we weren't able to start until late September. Environmental restrictions mandated we terminate earthwork by October 15, although we were able to obtain a one-month extension because it wasn't raining. We couldn't resume work until April 2014, so we ended up jamming most all of the work into the 2014 season."

To create room for construction of the RSAs and an adjacent service road, the airport acquired three land parcels totaling 30 acres. Various environmental mitigation measures were executed to protect California tiger salamanders and rare plants; fencing was erected to exclude Western pond turtles from construction areas; and siltation barriers were installed adjacent to grading or excavation areas.

During the first phase of the project, Runway 2-20 was shut down for approximately two months while crews upgraded a taxiway that runs to the main terminal area and constructed a partial parallel taxiway and connectors. Much of the runway and taxiway lighting was installed during winter 2013, although not connected to a power supply until contractors began earthwork in April 2014.

"Our primary concern was that we knew we were going to shut down our main runway (14-32) for about four or five months," details Stout. "We had to get all of our instrument procedures for Runway 2-20 FAA-certified before we could take 14-32 out of service."

Ultimately, the certification and shut down processes took 10 days longer than the original schedule planned.  

Landscaping Saves the Day

In order for crews to complete work on Runway 14-32, initial plans called for the airport to temporarily shorten Runway 2-20 to 4,600 feet. Then, two months before the scheduled shutdown of 14-32, STS' sole commercial carrier informed airport officials that its aircraft needed 4,800 feet. 

"Alaska Airlines ran their numbers and determined that if they had an engine-out situation and the aircraft had to return to the airfield, trees at the end of the runway would present an obstruction and aircraft would need another 200 feet of runway to land," explains Van Gompel. "As a result, we had to reposition and remark the entire threshold end of the runway."

The company also worked with airline personnel to identify the particular trees that were causing concern. "They initially gave us a list of around 400 trees," he recalls. "We determined that many of the trees identified were drawn from old, outdated information and cut the list down to 11 trees, which we removed. When we did the switchover, the airline experienced no problems."

Mead & Hunt Vice President Jon Faucher takes pride in the project team's ability to overcome the late-fourth-quarter challenge. "We made sure (Alaska Airlines) flight personnel were comfortable with the distance we gave them while maintaining appropriate separation from construction activity," he comments. "They were able to operate off the shortened runway for the majority of the summer. And now, with the project complete, Runway 2-20 is 5,200 feet - 200 feet longer than its original length." 

To minimize impact on airport operations, much of the airfield work was performed at night, when no flights were scheduled. The installation of an 885-foot-long precast concrete arch culvert beneath one of the runway safety areas was one of the nighttime projects. Large cranes were needed to move the structure's 149 blocks (each weighing 18 to 22 tons); so work was performed at night during 44 scheduled airport closure periods to prevent the tall equipment from encroaching on active airspace. Crews also constructed another precast concrete box culvert that measured 825 feet in length.

All told, the project required 45,000 cubic yards of aggregate base, 36,000 tons of asphalt and 160,000 square feet of pavement markings. More than 130,000 cubic yards of soil were taken from a previous on-airport project for the runway extensions.

Two Birds, One Stone

Although the airport's complex airfield initiative was primarily a safety project, Stout reflects that decoupling and extending the runways facilitated flight operations. "The control tower personnel have more flexibility when directing aircraft, and aircraft can now land simultaneously on both runways," he explains. "We can't land commercial aircraft simultaneously, but 90% of our traffic is general aviation."

The airport has also received increased interest from air carriers since the runway improvements were completed last fall. Several airlines have indicated that STS is now on their short list for adding service, reports Stout. 

"Our primary focus is providing service to eastern destinations such as Salt Lake City, Phoenix and Denver. We actively marketed the airport throughout the construction process and have ramped up our efforts since project completion," he explains. "Alaska Airlines continues to do well and will be up to seven Q400 flights a day this summer. We've also seen an increase in corporate traffic since the completion of the project as well as increased interest in using the airport as a base for corporate jets."