The U.S. Navy will be detonating underwater explosives at Apra Outer Harbor and Piti on April 27 and 28, requiring the Coast Guard to restrict entry into the affected areas.

While acknowledging the “inherent danger” and “potential hazards” associated with underwater detonation, the Coast Guard said it would not be seeking community input due to time.constraint.

The Coast Guard said it is authorized to issue a rule without prior notice and opportunity to comment when the agency for good cause finds that those procedures are “impracticable, unnecessary, or contrary to the public interest.”

The activity will run for eight hours each day from 8 a.m. to 4 p.m., the Coast Guard said in an announcement posted on the Federal Register on Friday, April 21.

The Coast Guard warned the underwater detonation poses potential hazards “within a 700-yard radius above and below the surface on April 27 and a 1,400-yard radius above and below the surface on April 28.”

“Entry of vessels or persons into these zones is prohibited, unless specifically authorized by the Captain of the Port Guam,” the announcement said.

“The Coast Guard believes this safety zone regulation is necessary to protect all persons and vessels that would otherwise transit or be within the affected areas from possible safety hazards associated with underwater detonation operations.”

According to the Navy’s Naval Weapons Engineering Course syllabus, explosive detonations underwater create shock waves in a similar manner to explosions in air.

“Due to the elastic properties of water, the shock wave tends to be of shorter duration, but with a proportionally larger peak overpressure. The energy in the underwater shock wave attenuates very quickly with range,” the syllabus states.

Although the shock wave from an underwater explosion does not cause the same level of damage as one would expect from studying explosions in air, the course syllabus indicate there is no guarantee “there are no effects from underwater shock waves.”

The Coast Guard said it received notice of the operation on March 9, only 49 days before the operation is scheduled, thus limiting its ability to issue a public notice ahead of time.

“Due to the late notice and inherent danger in underwater exercises, delaying the effective period of this safety zone would be contrary to the public interest,” the announcement said.

“Thus, delaying the effective date of this rule to wait for a comment period to run would be impracticable because it would inhibit the Coast Guard’s ability to protect vessels and waterway users from the hazards associated with this operation.”

The Coast Guard said businesses running vessels that might be affected by the Navy training activity may send comments to the Small Business and Agriculture Regulatory Enforcement Ombudsman and the Regional Small Business Regulatory Fairness Boards.

“The Coast Guard will not retaliate against small entities that question or complain about this rule or any policy or action of the Coast Guard,” the announcement said.