Thousands of bats live in this Sacramento freeway. How Caltrans is ‘evicting’ them

Why did Caltrans bolt hundreds of upside-down traffic cones to the underside of the W-X freeway in downtown Sacramento? The answer is almost as odd as the sight of rows of orange cones clinging like bats to the belly of a concrete bridge.

In fact, the whole endeavor involves actual bats.

Thousands of bats and birds and even some owls reside in the crannies and crevices of the elevated freeway. Caltrans has decided to evict them so they won’t be in the way of a major upcoming Highway 50 widening project.

The traffic cones are the eviction notices.

Each cone covers one of the structure’s “weep holes,” the holes that allow moisture to drain out of the bridge deck during the rainy season. Those weep holes have been serving another, informal, purpose: Birds and bats use them as entrances to hideaways in the structure where the bats roost and the birds build nests.

Workers screwed a short plastic tube to the narrow end of each cone, then they duct-taped a short plastic sheath to the end of the tube. Bats and birds who are inside the structure can exit the bridge through the center of the cone, the tube and the plastic sheath. But they cannot get back in because the sheaths’ sides press back together, closing up.

“It’s an ingenious way that is inexpensive, easy to make and install,” said Caltrans biologist Shawn Duffy, who is advising on the project.

Evicting the bats and birds means those species will not be around to nest or reproduce in the structure during the upcoming construction period, Duffy said. “We don’t want them having their young while we are working on it. They might abandon their young, which we don’t want them to do.

“You try to approach it with the idea that you are going to prevent any harm to these creatures that are using the structure, with the idea they can come back and take up residency again” as soon as the project work finishes in each bridge section.

The “exclusion” cones are a relatively new trick for Caltrans, but were used locally last year during widening of Highway 65 in Placer County near Interstate 80, officials said.

The planned Highway 50 project will add carpool or high-occupancy vehicles lanes to Highway 50 from just east of Watt Avenue through the central city area to the interchange with Interstate 5. Crews also will build sound walls along the south side of the freeway from Stockton Boulevard to 65th Street. Other elements of the project include widened connector ramps, taller bridges at overcrossings for larger trucks, and new pavement.

In the central city area, Caltrans plans to widen the freeway in the median area for the extra lanes. The project will cost $433 million, and will be done in phases between 2021 and either 2024 or 2025, starting with the sound wall construction next month.

Although the freeway is austere looking and made mainly of concrete, it is in fact a teeming ecosystem, Duffy said.

Thousands of bats roost there in summer, fanning out at night to hunt for mosquitoes and moths in the adjacent neighborhoods, parks and along river areas, Duffy said. Many leave for warmer climates in winter, but some stay.

Bats also tend to tuck into the freeway’s expansion joints. Those joints have now been covered with spray foam topped by boards.

Birds that nest in or on the bridge include purple martins, white-throated swifts, black phoebes, starlings and swallows, Duffy said. Some weep holes are covered by boards as well. And work crews soon will put plastic at the corners and columns to prevent swallows from building mud nests.

“The real estate is used extensively,” Duffy said.

This story was originally published December 28, 2020 at 5:00 AM.