A Washington Department of Ecology spills response crew oversaw the work of a contractor refloating a tugboat with 2,000 gallons of diesel fuel on board that sank on the northeast end of Lake Washington April 18.

The tugboat, Sea Prince, operated by Lakeshore Marine Construction, went down near a dock, creating what an Ecology spokesman described as a “heavy sheen” of diesel fuel. The 25-30 gallons of fuel that spilled were quickly contained by oil blooms deployed by the spills response contractor.

Although there were no observable impacts on fish or wildlife from the spill, Ecology spokesmen said even a small amount of fuel can cause environmental damage.

Spill responders expect almost all of the spilled diesel to be recovered through absorbents or dissipated through evaporation.

What caused the tugboat to go down has not been determined.

Lakeshore Marine Construction does waterfront construction such as retaining walls and docks.