Foretelling the gradual deterioration of a sunken ship is as inexact a science as exists, but the National Park Service continues to devote considerable resources to advancing that science as it continues to track the condition of the historic battleship that is both Hawaii’s No. 1 tourist attraction and the final resting place for more than 1,100 U.S. servicemen.

The first major effort to assess and document the condition of the USS Arizona, initiated by a series of dives authorized for the specific purpose of removing thousands of coins dropped onto the ship over the years by visitors, came in the mid-1980s and ultimately resulted in the first comprehensive map of the sunken ship.

Divers also recorded changes in bio-fouling, the accumulation of algae, plants, barnacles and other organisms. Their findings indicated that the harbor’s former use as a dumping ground may actually have contributed to the ship’s preservation by fostering marine growth, which in turn created a protective, anaerobic layer over the hull.

PEARL HARBOR

In the early 2000s the National Park Service’s Submerged Resources Center initiated the USS Arizona Preservation Project to develop an overall management strategy for the deteriorating ship and to conduct research into the corrosion and deterioration processes affecting the ship’s hull, both internally and externally.

In 2007 the USS Arizona Preservation Project worked with scientists at the National Institute of Standards and Technology to create the first mathematical model to simulate the deterioration of a sunken ship using data from the Arizona. The scientists used the ship’s blueprints and isolated an 80-foot section from the middle and entered its dimensions into a computer, creating 200,000 data blocks and entering data related to metal properties, corrosion, damage and external forces.

At the time, scientists predicted that the structure of the ship would grow unstable as it approached 75 percent thinning in 10 to 20 years.

More recently the park service worked with the software company Autodesk to undertake creating an “intelligent, high-resolution, highly detailed model” using laser scanning, sonar and the company’s photogrammetry technology. Scans were taken in 2014 and again this past summer.

The 3-D images that were produced largely confirmed what previous, less sophisticated studies had already mapped — with one positive new insight.

“We found that the ship is not degrading as fast as the hypothesis says it should,” said Scott Pawlowski, chief of cultural and natural resources for the World War II Valor in the Pacific National Monument. “The structure is solid. It’s definitely rusting in places but not in major structural areas. We’ll continue to monitor it, but based on the best science we have available, it’s in pretty darn good shape.”

Pawlowski said assessments of the memorial, which rests above but is not directly connected to the sunken ship, indicate that even if the ship collapses in areas near the memorial’s pile moorings, the resulting damage would not be enough to seriously compromise the memorial’s stability.

The findings overall are good news for the stewards of the Arizona, whose efforts to maintain and preserve the ship have always been balanced against the necessity of upholding the sanctity of one of the nation’s most revered tombs.