Manned and unmanned submersibles — possibly from the University of Hawai'i — would survey the ocean floor thousands of feet deep off south O'ahu for chemical weapons dumped at the end of World War II, under a $459.6 billion defense appropriations bill approved yesterday by the U.S. House.

U.S. Rep. Neil Abercrombie, D-Hawai'i, said $5.5 million would go for sonar mapping, water quality testing and analysis "so we know exactly what's there, how much is there and, critically, what condition the (munitions) containers are in."

"Sixty years of saltwater corrosion may have caused a hazard. These funds will allow us to take the first steps in mitigating a possible environmental time bomb," Abercrombie said.

Hawai'i lawmakers inserted about $218 million for special projects in the defense spending bill, approved 400-15 by the House.

The amount could grow if the Navy agrees to a provision from Sen. Daniel K. Inouye, D-Hawai'i, to use $20 million of its funding to help build a new USS Arizona Memorial museum and visitor center.

Other projects include $25 million for a Hawai'i-based federal health program, $23 million for the Maui Space Surveillance System and $7 million for upgrading the electrical distribution system at Hickam Air Force Base.

The Senate began debate on the bill yesterday and could vote on it as soon as today.

During the Senate debate, Inouye, chairman of the Senate Appropriations Defense Subcommittee, said the measure was a "must-pass bill."

The House bill includes $19.6 million for projects requested by Abercrombie, including the $5.5 million to begin the survey of tons of chemical munitions dumped off O'ahu. Samples of the water, sediment and plant and animal life taken by surface ships and underwater would be analyzed for toxic compounds.

Publicity about the U.S. military's practice of dumping chemical and conventional weapons at sea decades ago led to records that 4,220 tons of hydrogen cyanide were dumped somewhere off Pearl Harbor in 1944. During that year, the military also dumped 16,000 100-pound mustard bombs "about five miles off of O'ahu."

In 1945, off Wai'anae, the Army dumped thousands of hydrogen cyanide bombs, cyanogen chloride bombs, mustard bombs and lewisite containers. Charts identified some as being in 1,600 feet of water.

"There are questions about what's happened in terms of rust, seepage and so forth on the containers. Nobody's even sure exactly what's there," said Abercrombie spokesman Dave Helfert. It's possible that it may be safer to leave the munitions where they are, he added.

The discovery of propellant charges washing up on shore in large quantities in March added to what might be a wider possible cleanup.

A study conducted by the National Oceanic and Atmospheric Administration concluded that about 2,000 rounds of dumped ammunition, including 3-foot artillery projectiles, pose no danger in relatively shallow waters.

Another $800,000 in the defense appropriations bill would be used to continue research at the Hawai'i Institute of Marine Biology into the hearing of marine mammals, such as whales and dolphins, and the effects of underwater sound such as sonar on the animals' behavior.

The bill also has a $2.4 million earmark from Inouye and Abercrombie for BAE Systems' continued development in Hawai'i of a marine mammal detection system for Navy aircraft, which would survey naval training areas before active sonar is used to avoid harming ocean creatures.

Another $5.2 million would be used for research on developing a global network of sensors that can track objects in space using small, inexpensive optics.

Oceanit Aerospace Group, the Maui-based subsidiary of Oceanit Laboratories Inc. of Honolulu, is developing the technology.

Reach Dennis Camire at dcamire@gns.gannett.com and William Cole at wcole@honoluluadvertiser.com.