Longshore clerks used to open containers to check for stolen cars or stowaways. But today, they work from an office, using video cameras and scales that weigh the trucks as they roll through the gate.
Clerks say the weight can vary by up to 5,000 pounds before it raises eyebrows. "You figure you're going to have a thousand of these tonight, why stop this one?" said a clerk who asked that his full name not be used.
Terrorists could pack explosives in a container and bring it in as an empty, said Mitre, the Longshore security director.
"It's easy to lose 1,000 to 2,000 pounds in a container of that weight," he said. "You'll never know there's something in it."
Even a modest attack could have widespread repercussions as ports close down in panic, Stephen Flynn, a fellow at the Council on Foreign Relations, predicted at a Seattle port security conference last week.
If a bomb blast showed security has failed, he said, "how can elected officials stand up and say we can continue shipping?"
Ports have taken some measures to prepare for attacks from within the U.S. Tacoma officials said the port used part of the $6 million it received in federal grants to add automated gates where trains enter fenced-off areas. Seattle got $12.4 million in grants and spent more than half on security at its cruise-ship terminals.
Officials at the Puget Sound ports would not discuss longer-range budgets or planning against terrorism, saying it would jeopardize security and violate federal laws.
By contrast, Los Angeles and Long Beach port officials were open to discussing their $400 million five-year plan, which includes building two major facilities: an inspection building where potentially explosive cargo can be safely unpacked, and a command center, where surveillance-camera feeds from terminals can be monitored by the Coast Guard, port police and other agencies.
Cosmo Perrone, director of security at Long Beach, said improving security is itself a great deterrent.
"Aren't you displaying the castle wall?" he said. "Why would you want to hide it?"
Port officials also say they lack funds to do much more for security, especially compared with what has been spent on airports. Of course, they added, fixes aren't always expensive.
"It isn't always the fancy gadget," said Rod Hilden, chief security officer at the Port of Seattle.
"Sometimes it's just going and looking at our facilities and seeing vulnerabilities."