The Army said yesterday that it is delaying a $2.5 million study of grenades, bombs and other ordnance dumped in shallow water off Waianae that was scheduled for October because it first needs to do an environmental assessment.

Conducting the assessment for what is known as Ordnance Reef will push back the technology demonstration project until April or May, the Army said. It said it determined an assessment is required under federal law.

"The Army’s commitment to understanding the potential impact of the munitions present at Ordnance Reef on human health and the environment is unwavering, as is its intent to develop and safely demonstrate at Ordnance Reef tools required to recover and destroy munitions that may be determined in the future to pose an unacceptable risk to human health and the environment," said Tad Davis, deputy assistant secretary of the Army for environment, safety and occupational health.

An environmental assessment is a component of the National Environmental Policy Act of 1969.

Prior to the proposed technology demonstration, the Army said it wants to ensure that the assessment identifies all potential environmental impacts and the public is provided notice and an opportunity to comment.

The Ordnance Reef project might cost up to $6 million and includes studying the long-term effects on marine life and regenerating coral reef in the area.

The Army expects to start with a demonstration project to see how munitions can be safely collected using remotely operated vehicles. Cutting tools similar to those used on oil rigs would be employed to see whether munitions can be removed from surrounding coral. Officials said the benefit of removing ordnance from coral would have to be weighed against the harm in cutting it out.

An Army Corps of Engineers survey in 2002 at Ordnance Reef identified more than 2,000 military munitions at depths ranging from 15 feet to 240 feet, with the majority observed deeper than 60 feet.

William Aila Jr., a Waianae Coast activist who works, fishes and scuba-dives in that area, previously said he had seen 4- or 5-inch shells, ammunition pallets, grenades and larger bombs.

Hundreds of grenades lie scattered in a 300-by-300-foot area, Aila said. He also said he was told that torpedoes and drums lie on the ocean floor in the area.

The Army, in consultation with state and federal agencies, expects to have the environmental assessment report completed by December. The Army will then provide a 30-day public comment period.

The University of Hawaii completed last month 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 and 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 did "not indicate any adverse impacts on ecological health" in the study area, known as HI-05.

The military plans to leave the munitions in place in waters as deep as 1,500 feet.

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

A 2007 report to Congress said 2,558 tons of chemical agents, including lewisite, mustard, cyanogen chloride and cyanide, were dumped at three sites off Oahu in waters as deep as 6,000 feet.

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.