The next step in researching chemical weapons dumped off O'ahu's south coast decades ago will begin this weekend as scientists start a yearlong study of ocean current patterns, which will eventually help officials decide whether the munitions should be removed.

The National Oceanic and Atmospheric Administration will place four monitoring sensors off Wai'anae at what was a military munitions dump site during World War II, also known as Ordnance Reef. NOAA will place another sensor at a deep-sea disposal site about 32 miles from Honolulu.

The federal Department of Defense is looking to possibly recover what NOAA said in 2007 are more than 2,000 tons of chemical agents, including lewisite, mustard, cyanogen chloride and cyanide.

Most materials break down when exposed to salt water this long, and even hazardous materials often become safe, said NOAA scientist Tony Reyer.

"We normally don't recover munitions," said Army spokesman Hudson Kekaula, but relatively shallow waters and proximity to the public has led the military to consider removing them.

The weapons are conventional and not nearly as dangerous as munitions found in a war zone, Kekaula said.

The federally funded $1.6 million project will study the speed and direction of ocean currents. The data gathered would determine where currents might take the materials "if by chance, there is some type of release of the munitions," Reyer said.

The data will also help University of Hawai'i students and NOAA scientists study how the environment is affecting those munitions.

The quantities and locations of munitions have already been identified, and this project will only study ocean currents, Reyer said. Scientists were able to map where the munitions were to ensure the sensors were landing in clear areas, he said.

NOAA will place one buoyed sensor at an 8,000-foot depth and two drag-resistant bottom mounts at a 50-foot depth off the south coast on Friday and two more drag-resistant bottom mounts on Saturday. Nothing will float above the surface, said NOAA scientist Jason Rolfe, but boaters or divers looking down through the clear 50 feet of water may be able to see the mounts on the ocean floor.

Boats and divers will not disturb the sensors with normal activities, but NOAA asked that civilians not intentionally move or disturb the equipment so the data will be as accurate as possible.

"Boaters might be able to see them, and if, for whatever reason, divers disturb the equipment it could potentially mess up research," Rolfe said.