Apr 30, 2013 10:16 AM by Samantha Ptashkin

Bat condos to be built under northwest side bridges

MARANA, Ariz.- Below the Ina Road Bridge, you can't see them during the day, but at dusk, bats fly.

"These bridges in Tucson hold a lot of bats," says Janine Spencer, the Environmental Engineer for the Town of Marana.

In fact, Spencer says the Ina Road Bridge, which runs over the Santa Cruz River, between I-10 and Silverbell, is home to as many as 30,000 bats over the summer months.

For decades, the bats have lived in between the tiny crevices of cement under the bridge.

But in a few years, the aging infrastructure will be torn down and the new bridge won't be so bat-friendly. "The new style bridges are flat-bottomed, as opposed to these old ones which have great crevices for bats," Spencer says.

The solution is to build "bat condos", which mimic the current home of the bats. "The deck will be thickened on the new bridge in areas and we'll design crevices right in the bridge that will be about two feet deep, ranging from an inch, to an inch and a half in width," Spencer says.

The Regional Transportation Authority is paying for the project, which will cost around $80,000.

Nine bat condos will be installed under the eastbound lanes of traffic of the new Ina Road Bridge. The nine condos will be able to hold about 30,000 bats.

Another two bat condos will be installed under the Cortaro bridge.

Spencer says installing the bat condos should be standard practice whenever there is bridge construction going forward. "We would just be inundated with mosquitoes if we didn't have bats," Spencer says. "A bat can eat 2,000 mosquitoes in one night."

Here is the timeline of events:

1) Later this year Spencer hopes crews will install the two bat condos under the Cortaro Road Bridge, which is just about a mile north of the Ina Road Bridge.

2) They will add data loggers to track temperature and relative humidity in the existing Ina Rd. Bridge and in the new bat boxes at Cortaro Rd. Bridge. By doing this they will know what climate conditions the bats prefer, to attempt to replicate these conditions in the new bat habitat structures.

3) Construction crews will build the east-bound Ina Rd. Bridge and incorporate nine new bat condos into the design.

4) Arizona Game and Fish will eliminate all bats from the existing bridge, in the fall and winter prior to demolition, when the least bats are present.

5) Crews will build the new west-bound Ina Road Bridge section, which will not include bat habitat.

All of this work is scheduled to take place over the next four years.


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