Over two miles of oil-containment boom were laid in Tomales Bay this week after a fishing vessel ran aground near Dillon Beach. The boat has so far only leaked a small amount of oil, but removing the vessel, which can only be reached by air, will take time.    David Briggs

A derelict fishing boat is wrecked on the rocky shoreline north of Dillon Beach, and engineers are assessing the state of the vessel with the goal of preventing pollution. Their biggest concern is an oil spill: The boat can carry up to 29,000 gallons of fuel, and its hull is punctured. 

Shoreline assessment teams observed light sheening in the immediate vicinity of the vessel, but engineers arriving by helicopter have found no evidence of a leak in 13 of 17 fuel tanks. The four remaining tanks have not been accessed because of the tides, and over two miles of containment boom has been placed in Tomales Bay just in case.

“Even though we didn’t have what we believe to be a large petroleum release in this event, we’re still looking at protective measures because of the unknown on that vessel,” said Ben Perry-Thistle, a Coast Guard planner who is helping to coordinate the response.

The 90-foot boat, called the American Challenger, was being towed from Puget Sound to Mexico by the tugboat Hunter. Last Friday morning, a rope tangled in the Hunter’s propeller, causing it to lose propulsion. The Challenger was brought alongside the tugboat, but rough weather caused the lines to break apart. Both ships were dead in the water. The Hunter anchored and was then towed to Sausalito, while a Coast Guard crew could not board the fishing boat because of its unknown structural integrity and proximity to the shore. The vessel ran aground around 1 a.m. on Saturday.

The boat now sits among large rocks south of the Estero de San Antonio, inaccessible by land or water. There appears to be a large crack on the bow, and on the beach-facing side of the vessel water flows out as the waves subside, Coast Guard officer J.J. Winston said at a briefing on Monday. 

Members of the California Department of Fish and Wildlife’s Office of Spill Prevention and Response have been on the immediate shoreline with sorbent pads to capture floating sheen in the water and oil on the rocks. The fuel, which appears to be diesel, dissipates through sunlight and wave action. “It being a high-energy shoreline, there’s a lot of movement happening there, and all of that movement does naturally work some of that sheen away through evaporation and other means,” Mr. Perry-Thistle said. 

With its capacity for 29,000 gallons of petroleum, a worst-case scenario for the American Challenger would register among the largest oil spills in an average year. There have been 42 spills greater than 10,000 gallons into water from Alaska to California since 2002, according to an oil spill task force monitoring the region. The oil spill that inundated the Bolinas Lagoon in 1971 spilled over 800,000 gallons, the most in Bay Area history.

Park employees from Bodega Head to Tomales Bay have been surveying shoreline further out from the wreckage and have not seen any contamination, and no oiled wildlife has been reported. The incident falls within the Greater Farallones National Marine Sanctuary, one of the most diverse ecosystems in the world and a breeding and feeding ground for at least 25 endangered or threatened species.

The American Challenger was registered to one of the largest fishing companies in the world, Seattle-based American Seafoods, though it is unclear who was towing the boat to Mexico., though it is unclear who was towing the boat to Mexico. Spokespeople for the response team declined to name who is responsible, and a representative from American Seafoods could not be reached for comment. The responsible party does not have insurance and was unable to respond to the pollution threat, according to Captain Marie Byrd, a Coast Guard sector commander. The response is being funded by Oil Spill Liability Trust Fund, which does not relieve the owner of financial responsibility.

“We gave [the owner] every opportunity to be able to take control of the pollution threat that was posed… and he was unable to address the pollution threat situation, so we had to go ahead and assume a federal response,” Capt. Byrd said.

The response team is operating under a federally mandated contingency plan and is made up of four agencies: the Coast Guard, the Marin County Office of Emergency Services, the marine sanctuary and Fish and Wildlife’s oil spill response team. Three companies were contracted to help deploy the yellow boom and bring in salvage engineers via helicopter. 

The first team touched down on Sunday and was able to gather documents on board, a key step toward creating models of the vessel for a salvage plan. Mr. Nelson explained that much work remains before such a plan can take shape: Engineers must determine the state of each compartment, the load of each tank and the overall structural integrity of the vessel. They will model how the boat is sitting on the rocks to determine how much force would free it. The timeline for creating a salvage and tow plan is unknown.

“Right now, addressing the pollution threat to mitigate environmental impacts to our wildlife is the top priority. As far as the ultimate fate of the vessel, what that looks like still has not been determined,” Capt. Byrd said.