A construction vessel floats on Oura Bay at the site of a future U.S. Marine Corps airfield for Camp Schwab, Okinawa, Jan. 23, 2025. (Keishi Koja/Stars and Stripes)

A construction vessel spilled oil at the site of a future Marine Corps airfield in northern Okinawa over the weekend, the second such incident in 10 days.

The spill occurred just more than a mile north-northeast of Cape Henoko in Nago city at 11:50 a.m. Saturday, according to a Japan coast guard news release that day. No injuries or environmental damage were reported.

The airfield is under construction at the Marine Corps’ Camp Schwab on land reclaimed from Oura Bay to replace Marine Corps Air Station Futenma in densely populated Ginowan city. The U.S. and Japanese governments agreed to move the base in 1996. The Okinawa prefectural government took to the courts to delay construction until recently.

A contractor at the airfield site reported at 12:19 p.m. that hydraulic oil spilled from a crane on a 2.3-ton dredging vessel operating off the coast, according to the coast guard.

The coast guard confirmed oil seepage on the water’s surface, and contractors installed an oil fence and an oil absorption mat to recover the oil. No additional oil was found leaking out of the oil fence by 2:45 p.m., according to the release.

The vessel was using its crane to install equipment on another small vessel at the time of the spill. The cause is under investigation, according to the release.

On Jan. 15, hydraulic oil spilled from a drill on a different vessel that was boring into the seabed. No environmental damage or injuries were reported, and the spill was contained the same day, the coast guard said.

Contractors hired by the Okinawa Defense Bureau, an arm of Japan’s Ministry of Defense, began ground improvement work in Oura Bay on Dec. 28.

The work involves solidifying the soft seabed to ensure stability for the airfield by “laying sand at the required locations on the seabed and driving sand piles,” the bureau said in a Dec. 27 news release.

In July, contractors drove test piles into the seabed to prepare the site for steel pipes that will support the seawall.

The construction zone is divided into two main sections: 279 acres on Schwab’s north side and 91 acres in the south, according to Okinawa Prefecture’s website.

Work on the Oura Bay side, or north side, had been on hold since April 21, 2020, when Okinawa Gov. Denny Tamaki, citing safety and environmental concerns, refused to approve design changes meant to solidify the seabed.

Last week, the Japan Supreme Court rejected an appeal in a lawsuit filed by Okinawa prefecture in September 2022 seeking to block changes to construction permits required by Japan’s Ministry of Defense to finish the project.

The dismissal ended a series of 14 construction-related lawsuits filed by both sides since Nov. 17, 2015.