ANTIOCH -- Work to widen the Highway 4 corridor is already helping some residents quickly make it home.
Just not human ones.
While working near a new overpass at Cavallo Road last month, Contra Costa transportation officials and a contractor discovered that a family of burrowing owls -- mother, father and three owlets -- had made a nest in a burrow in an embankment near a freeway retaining wall.
"It definitely caught us by surprise," said Susan Miller, project manager with the Contra Costa Transportation Authority.
Added Oakley Mayor Kevin Romick, vice chair of the transportation authority board: "It appears they weren't too intimidated with all that was going on, found some holes and just bunkered down."
The find left transportation planners scrambling to adjust the work schedule on that segment of the project to prevent delays while being environmentally sensitive to the raptors, said Ivy Morrison, a Contra Costa Transportation Authority spokeswoman.
A buffer zone of 250 feet -- marked in spots with four-foot high temporary orange-colored fencing -- was established around the owls' nest to keep machinery and contractors away.
"Luckily, on a project of this size, there are so many other things that can be done in the interim," Morrison said.
Brentwood Mayor Bob Taylor, who sits on the local transportation committee, said, "It's not going to totally impede (the project) on a large scale."
A wildlife biologist already observing the area has paid extra attention to the spot where the owls are, making sure the nests are not disturbed, Miller said. The cost for her extra time is nominal, Morrison said.
"You have to be cognizant of them, and make sure everything is being done appropriately," Taylor said.
Standing about 10 inches tall and weighing less than a pound, burrowing owls are identified on the California Department of Fish and Wildlife's list of species of special concern, meaning their numbers are shrinking. One place where they are abundant, though, is in East Contra Costa's grassy hills.
Documents created in 2005 to study possible environmental changes from the half-billion dollar project to widen Highway 4 identified the presence of burrowing owls and California red-legged frogs -- requiring that precautions be taken.
But, the document said they would likely be found in a more uninhabited rural creek bed area to the west.
The burrowing owl's nesting season is from February to Aug. 31, but only after the birds have fully fledged can the buffer zone be removed. Romick said the owlets off Highway 4 are already learning to fly, so it won't be long before the nest is empty.
After that, officials say, they will devise a plan to ensure the owls don't return.
Burrowing owls have been on Antioch's radar for about a decade, since residents pushed for protections for those displaced by Prewett Park. In response, the city set up 24 acres of designated habitat for them at the park.
Additionally, some nesting birds were found on a segment of the work farther east.
The owls also made homes in shallow tunnels in a stalled Antioch residential development in 2009. Activists built six artificial burrows at the preserve to attract the owls evicted from that subdivision.
Burrowing owls and other items have been discovered during development of several East Contra Costa projects, including Indian remains at Brentwood's Trilogy subdivision, Taylor said.
"When dealing with environmental issues, you have to be aware that these things are going to pop up. And they have to be appropriately addressed," he said.
Contact Paul Burgarino at 925-779-7164. Follow him at Twitter.com/paulburgarino.