'Collapse is inevitable' — but when?
By Karen Blakeman
Advertiser Staff Writer
Visitors aboard the USS Arizona Memorial often lean on the rails and gaze into the water to watch a drop of oil pearl upward, or allow themselves to be mesmerized by the watery motion of light and shadow over the sunken tomb.
T
Photos by Bruce Asato • The Honolulu Advertiser
his week, those looking down might see people.
National Parks Service divers Jenni Burbank and Jim Bradford install a prism for a laser surveying instrument on the bow of the USS Arizona. A team of six divers is using high-tech surveying devices to collect information to determine how fast the sunken vessel is deteriorating in Pearl Harbor.
"We're very much in the public view," said Matthew Russell, an archaeologist heading a team of half a dozen divers who are collecting information to help determine how fast the Arizona is deteriorating.
Using the floating ramp where the tour boat docks as a base, the divers move beneath the memorial, measuring, surveying and mapping the midsection of the ship. They point a high-tech surveying device into the depths, gauging distances from one point to the next, collecting data for a 3-D computer model of the sunken vessel and the surface on which it rests.
When completed, the model will be able to predict how quickly and in what way the ship will disintegrate and which major structural features will give way first, Russell said. This will give park officials "the information they need to make decisions about when and if to intervene in Arizona's natural deterioration."
The divers' work environment — more than 30 feet below the surface of Pearl Harbor — is a memorable one.
"Visibility is poor, especially by Hawai'i standards, because it's silty in Pearl Harbor," Russell said. "When you swim around, the sediment on the decks swirls up."
Never far from their minds as they work, he added, is the fact that the battleship is a war grave, a tomb for more than 1,000 men who died 63 years ago in an event that would change the course of American history.
Reminders are scattered through the wreckage.
"The galley area is in the midship. There are bowls, a cooking pot. The leather sole of someone's boot. It isn't easy to look at those things," Russell said.
"It's not like any other place on earth. It's sacred."
Kelly Gleason, a volunteer, passed a prism for a laser surveying instrument to Jenni Burbank, a National Parks Service diver, yesterday. Data will be used for a 3-D computer model of the ship.
Russell, an underwater archaeologist with the government's Submerged Resources Center in Sante Fe, N.M., has headed up the USS Arizona Preservation Project since 1999.
Over the years, he and his divers have drilled into the Arizona's encrusted hull and sent a remote-operated vehicle into the wreckage to determine corrosion rates. They've taken core samples, three inches in diameter and 50 feet long, from the ocean floor beneath the Arizona.
That data and other precise measurements gathered by Preservation Project members will be fed into a supercomputer, he said. Some of the data was collected last week using sound waves, and more was gathered this week by hand or with a tripod device that shoots a laser beam from a known coordinate to a target held by a diver.
The information will be combined with the ship's original specifications and used by a team of engineers and metallurgists at the National Institute of Standards and Technology who are building a 3-D computer model — called a Finite Element Model — of the Arizona.
Once the right amount of precise data has been fed into the computer, the FEM can be manipulated to forecast what the ship's ruins will look like at any point in the future.
Divers yesterday measured a salvage quay installed onto the sunken hull of the USS Arizona.
"It's very, very complex and sophisticated stuff," Russell said. "The computer will run through the software and give you an idea of what it will look like, but it takes two weeks to get an answer."
So far, preliminary data indicates the Arizona suffered more damage when it was bombed than was previously thought.
"Forward of the memorial, toward the bow, the top deck has collapsed into the main deck and the main deck has collapsed onto the second deck below," he said.
"We knew the one- and two-gun turret dropped 25 feet straight down and took out the intermediate decks, but we didn't realize the damage extended as far aft as it does — right under the forward edge of the memorial. This is the area we are working in, and when you concentrate on the details it just leaps right out at you."
Visitors to the USS Arizona Memorial peered out over the side at a diver, one of six divers who are measuring, surveying and mapping the midsection of the USS Arizona in Pearl Harbor.
Despite the damage, the wreckage is holding up well, he said. Corrosion is slower than expected, and the ship has settled into a stable position on the ocean floor.
"Collapse is inevitable," he said, "but by all indications, it is not imminent. It could be decades."
Oil leakage is always present — about two quarts per day — but that rate has remained constant over the past several years, Russell said, and with other improvements in Pearl Harbor, nature has begun to lay claim to the wreckage.
"All kinds of coral colonies are springing up, and there are small damsel fish that we never used to see," he said. "One sea turtle seems to live on the Arizona. He is always here when we come out."
The divers are expected to work through the weekend.
Reach Karen Blakeman at 535-2430 or kblakeman@honoluluadvertiser.com
