City crews shut down part of Pioneer Way in Oak Harbor Tuesday to clean up heating oil that leaked from a tank behind a downtown business.

As many as 200 gallons leaked from the tank behind a building at 890 Pioneer Way, although very little of that likely made it to the harbor, said Larry Altose, a spokesman for the state Department of Ecology.

The building’s tenants include a nail shop and an embroidery business.

“An outdoor above-ground heating oil tank had been filled last week with a delivery of 200 gallons,” he said.

“That’s where the spill estimate came from, as we begin by assuming everything in the tank spilled,” he said.

“We may refine that estimate, though.”

Oak Harbor Fire Department first got a call shortly before 4 p.m. Monday, when callers reported the smell of diesel in the vicinity of Pioneer and Midway Boulevard, said Fire Chief Ray Merrill.

That’s where the city’s stormwater outfall is located.

Firefighters went to the scene, put a plastic bottle under the effluent coming out of the pipe and saw a layer of oil on the surface, he said. City crews strung an orange protective boom around the outfall pipe to keep the oil from spreading.

Tuesday, city vactor trucks sucked oily water from manholes downtown, while other workers put out absorbent pads around the pipe. The smell of diesel was still pungent.

The leaky tank was located on an unpaved area with no secondary containment, Altose said.

Some of the oil soaked into the ground and some drained through cracked asphalt pavement into a private storm drain and catch basin linked to the city’s system.

The state advised the property owner to contact his insurance company and hire an environmental contractor to cleanup the area around the building.

The property owner is cooperating, Altose said.