Thousands of unexploded chemical weapons are sitting on the ocean floor about five miles off of Oahu’s famed southern beaches.

Research shows that the military dumped about 16,000 bombs filled with mustard agent, each weighing 100 pounds, off the coast of Pearl Harbor during World War II. At the time, it was a common method of disposal.

Now, decades later, with $3 million in funding from the U.S. Army, scientists at the University of Hawaii are investigating whether these weapons could be posing a risk to human health or the marine ecosystem.

For the past couple of weeks, a team of three scientists has descended hundreds of feet below sea level in a yellow, battery-powered submarine that’s equipped with glaring lights, nimble electronic arms and cameras to study the munitions.

It’s the first major investigation into what impact the discarded chemical weapons may be having on the environment, according to J.C. King, the Army’s assistant for munitions and chemical matters, who spoke at a media briefing on Friday.

The survey is expected to provide a roadmap for future testing at other chemical weapons dump sites in U.S. coastal waters. Up until 1970, the military discarded millions of the weapons at sea, according to military records made public in recent years, and the potential health and environmental impacts of the ordnance, as well as their threat to offshore oil drilling in the Gulf of Mexico, have become a matter of increasing national concern.

“We are basically writing the book,” said Terry Kerby, the operations director for the Hawaii Undersea Research Labs, who is piloting the dives. “It’s never been done before, this deep water investigation of these ordnance sites. We are basically establishing procedures that can be used for sites all over the world.”

The Hawaii researchers have collected samples of seafloor sediment, water and marine life around the sunken ordnance for chemical testing. A second round of samples will be taken next year and a final report is expected to be released in 2015 at the earliest, according to officials working on the project. A central focus of the study is to detect whether the chemicals could be seeping into seafood, according to Margo Edwards, the principal investigator for the project at UH’s School of Ocean and Earth Science and Technology.

The mustard bomb dump site is just one of four graveyards for chemical weapons known to exist in waters around Hawaii, and one of 19 that exists in U.S. coastal waters. The John Warner National Defense Authorization Act for fiscal year 2007 ordered the Department of Defense to initiate a comprehensive search of the military’s sea disposal dump sites. The military dumped millions of tons of conventional and chemical weapons in coastal waters between 1919 and 1970, when the military discontinued the practice. In 1972, Congress passed the Marine Protection, Research and Sanctuaries Act outlawing the dumping.

Unitl recently, there was little information on the extent of the disposals, the exact locations of weapons and their composition. The 2007 defense budget bill initiated a widespread search of millions of dispersed and spotty military records that turned up a surprising amount of dumping off Hawaii and Alaska, the east and west coasts of the mainland, and even the Mississippi River.

In Hawaii, a DOD review of more than a million pages of documents at the National Archives revealed several main dump sites for chemical weapons totaling 2,700 tons, in addition to extensive disposals of conventional weapons.

Off Waianae, the military dumped thousands of munitions containing chemical warfare, including mustard agent, cyanide, lewisite and cyanogen chloride. This includes about 200 containers of lewisite, each weighting more than 2,000 pounds, as well as 20 cyanide bombs, weighing 1,000 pounds each, and hundreds of bombs containing cyanogen chloride.

The military disposed of 28,000 projectiles containing mustard agent at a site a few miles further out to sea than the location that UH researchers are currently studying. Thousands of mustard projectiles were also sunk off the east coast of Maui.

These are just the locations that are known. Records indicate that thousands more weapons containing mustard gas were disposed of around Hawaii, as well as millions of conventional munitions, including bombs, grenades, rockets and ammunition, but the military doesn’t know where.

The chemical weapons that UH is currently studying off Pearl Harbor were an inadvertent discovery. In 2009, UH was conducting a study of the ocean floor for the state’s proposed interisland cable project, designed to bring renewable energy from Maui, Molokai or Lanai to Oahu through undersea cables laid along the ocean floor. During the study, researchers found about 100 mustard bombs. The site is believed to be that where 16,000 mustard bombs were sunk, but records hadn’t provided the location.

During the past couple of weeks, researchers have identified another 100 bombs within a three-mile study area, according to Edwards. The chemical munitions could pose a serious threat to laying the cable, according to a state energy office report of the findings, which suggests that other routes be considered.

UH had made an earlier attempt beginning in 2007 to find chemical weapons to no avail. But sonar and other location methods did turn up tens of thousands of conventional weapons off of Pearl Harbor.

“As the ships were steaming along, stuff was just being thrown overboard,” said Edwards, who said that imaging had revealed distinct trails tracing back to Pearl Harbor.

But while records give general locations of dump sites and sonar has provided more detailed information, actually finding the weapons is a challenge.

“Using a submersible to search the deep ocean floor is kind of like driving over the Pali on a pitch black night with a flashlight looking out the window,” said Edwards.

Officials working on the project said Friday that removing any of the ordnance was unlikely because of the dangers it poses. Casings containing the chemicals are in various stages of decay. In 1976, three Department of Defense workers were burned by mustard agent when bringing containers to the surface during a biological survey about three miles off of Pearl Harbor.

Sulfur mustard, often referred to as mustard gas, is a liquid that can cause blistering of the skin, severe burns to the eyes and respiratory track, as well as death, according to the Centers for Disease Control. It’s also a known carcinogen. Now banned by international treaty, it was used during World War I and World War II.

A central concern is whether the chemicals are making their way into the food chain, according to Edwards.

At the colder temperatures found in deep ocean water the chemicals solidify and are only slightly soluble, according to information from the Department of Defense. Hazardous material that is leaked into the water is unlikely to persist at high concentrations.

Edwards said it was unlikely that the ordnance would make its way to shore or more shallow waters used for recreation because of the geography of the ocean floor.

“There’s a really steep cliff, a steep drop-off basically, once you get to between 150 and 300 meters water depth. It just sort of drops off, so gravity doesn’t want this stuff to go that way,” she said. “It’s not more buoyant than water so it shouldn’t float to the surface.”

UH Scientists descend in Pisces V, a submarine provided by the National Oceanic and Atmospheric Administration, to collect seafloor sediment near ordnance off Pearl Harbor.

Watch a slideshow of undersea operations. Photos provided by UH:

This Department of Defense map shows known dump sites of conventional and chemical weapons off Hawaii.

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Listings of the known ordnance dumped in waters off Hawaii can be found in this DOD report. Records show the military disposed of the weapons between 1920 and 1951.

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