"Water is starting to kind of seep into this area, and that's causing some erosion," Yakel said. "We don't want to wait for the wall to fail. We want to make the repairs before it becomes an issue."

It's unclear if sea level rise is to blame. SFO officials have yet to determine a definitive cause for the erosion, according to Yakel.

The Airport Commission earlier this fall approved the job, which will take place on the northeast section of SFO's property that protects it from flooding, king tides, high waves and storm surges.

The emergency declaration allows the airport to fast-track repair work. SFO officials are in the process of getting permit approvals from the U.S. Army Corps of Engineers and the San Francisco Bay Conservation and Development Commission.

In July, airport staff observed the damage. Several weeks later a geotechnical consultant found "seepage problems" and a potential sinkhole, Satero's letter states. "If this repair is not completed before the rain season, the seawall may fail and flooding is likely to occur," Satero said. The letter also said the repair work should have been completed by Nov. 30.

According to AGS, a San Francisco-based engineering firm hired by SFO, the section of seawall was in "critical condition" and repairs were needed before the rainy season when "the seawall was likely to fail and allow flooding," according to a memo written by the Board of Supervisors' budget and legislative analyst.

That flooding could occur on all eight of the airport's runways and taxiways, according to Geri Rayca, the manager of SFO's Planning, Design and Construction Division.

Airport officials say putting the contract for the work up for competitive bidding would take too long. They selected the Dutra Group, a marine construction and dredging firm, to make the repairs.

The short-term emergency work involves placing 2,000 feet of riprap, a layer of stones and concrete chunks, at the site, as well as repairs to the seawall's asphalt pavement.

Airport officials expect the repairs to take a month to be completed. A crane on the bay side of the seawall will do the work, and SFO operations are not expected to be affected, Cathy Widener, SFO's manager of government affairs, said during Wednesday's hearing.

Long-term work to prevent flooding at the airport from sea level rise, a decade-long project called the Shoreline Protection Project, will cost $60 million, according to SFO.

In the meantime, airport officials are working on increasing inspections of the entirety of SFO's 8-mile perimeter seawall.

Right now those inspections are done intermittently, Widener said. "Airport staff ... are currently working developing a more rigorous program."

KQED's Peter Jon Shuler contributed reporting to this post.