DISCOVERY BAY -- Human error at a gas station fuel pump over the weekend led to 22 gallons of fuel being spilled into a storm drain, prompting a large multiagency response to clean the hazard.

Around 11:38 a.m. Saturday, a boat owner filling up a large Boston Whaler sport fishing boat at the Safeway gas station on Bixler Road and Highway 4 placed the fuel nozzle into a fishing rod holder instead of the gas tank, according to the East Contra Costa fire district.

The gas tank is located inches away from one of several fishing rod holders on the vessel, and both holes were several inches above where the owner could see, Battalion Chief Jeff Burris said.

"He unscrewed the fuel cap, couldn't see exactly what he was doing and wound up sticking it in the wrong hole," Burris said. "It was completely accidental."

The boat is self-bailing, meaning that it can remove water that comes into the deck when at sea, Burris said. In this instance, that mechanism pushed the fuel out of the boat and into a nearby storm drain.

Firefighters were joined at the scene by Contra Costa Hazardous Materials crews, state Fish and Wildlife officials, California Highway Patrol officers and sheriff's deputies.

Hazmat cleaned up the spill by placing absorbent booms in the drain that skim the water away from the fuel, said Matt Kaufmann, a county hazardous materials specialist. Firefighters flushed the storm drain at the point of entry with about 750 gallons of water, quickly pushing the fuel along into the booms, Burris said.

One lane of Highway 4 was closed while the work was done, he said.

Cleanup took about four hours.

Spills in the water system such as the one in Discovery Bay happen on about a monthly basis, with petroleum or diesel fuel being two of the substances most often triggering a cleanup, Kaufmann said. Though this spill is not considered severe, it is still deemed significant, he said.

The East Contra Costa area generally has several spills each year that requireresponders ¿to prevent liquid from seeping into storm drains. The largest recent incident was April 18, 2011, when a tanker truck spilled over 4,000 gallons of milk onto Brentwood Boulevard -- some into the drains.

Fish and Wildlife will determine whether the motorist will be cited or fined for Saturday's incident. An official could not be reached for comment Monday.

Contact Paul Burgarino at 925-779-7164. Follow him at Twitter.com/paulburgarino.