The University of Hawaii has completed a three-year investigation of conventional and chemical military weapons dumped during and after World War II at a deep-water site five miles south of Pearl Harbor.

The School of Ocean Earth Science and Technology, which did the study for the Pentagon, reported that although even the best-preserved munitions casings are deteriorating, the observations and data collected "do not indicate any adverse impacts on ecological health" in the study area, known as HI-05, the university said yesterday.

However, Waianae Coast activist William Aila Jr. said the study falls short because no conclusive determination was made whether the testing was being done near conventional or chemical weapons.

"They should have brought one up and had it tested," Aila said.

A 2007 report to Congress said 2,558 tons of chemical agents, including lewisite, mustard, cyanogen chloride and cyanide, were dumped at three deep-water sites off Oahu.

"We know from archived records thousands of military munitions were sea-disposed at HI-05," said Margo Edwards, UH’s principal investigator. "There were also some indications that as many as 16,000 M47 100-pound bombs containing approximately 73 pounds each of the chemical agent mustard were disposed in the area."

More than 2,000 munitions were identified on the sea floor. Edwards said it would have been too dangerous to bring up some of the weapons for testing, but there is the possibility of follow-up study.

There has been an instance of harm from the chemical weapons. Three Defense Department contractors were burned in 1976 aboard a commercial vessel conducting dredging operations after inadvertently recovering leaking cylinders that contained mustard agent, the UH study said.

Sediment, water and biological samples were analyzed at UH and independent laboratories on the mainland for munitions components, including TNT, chemical agents and metals.

The analytical methods used to detect munitions components "were effective," UH said.

"With the exception of one unconfirmed detection of mustard, neither chemical agents nor explosives were detected in any samples," the university said in a release.

The risk to human health from the consumption of fish and shrimp collected near the HI-05 Study Area was within Environmental Protection Agency "acceptable risk levels," according to UH.

According to government reports, two of the munitions dump sites off Oahu are in waters 6,000 feet or more deep. UH looked for munitions at the HI-05 site in water as deep as 1,500 feet.

Both chemical and conventional weapons may have been dumped at the sites. Video reconnaissance revealed in March 2009 "a broad field" of depth charges in the vicinity of a large coral head and a trail of disposed torpedo warheads, the study said.

Most of the munitions were distributed in narrow curvilinear trails ranging from hundreds of yards to a few miles in length, suggesting that the weapons were pushed overboard by underway ships.

It was not until 1969 that the National Academy of Sciences released recommendations to modify the disposal of chemical weapons. Sea disposal was until then considered the safest and most cost-effective method to discard excess or obsolete weapons, the U.S. government said.

The Pentagon does not plan to remove any of the deep-water weapons because it said there is no data to indicate any of the munitions pose a threat to human health or the environment.

The UH investigation required the use of high-resolution side-scan sonar and remotely operated underwater vehicles to locate the undersea munitions.

Two three-man research submersibles from the Hawaii Undersea Research Laboratory also were used to take water and sediment samples in areas where military munitions were found.

UH said the U.S. military spent about $3 million for the research.