Caltrans, Fresno, CA

San Joaquin Bridge / State Route 99 BAT Surveys


The bridge crossing the San Joaquin River at Highway 99 needed retrofit. Working in partnership with Caltrans District 6 and MCM Construction, QK provided biological inspection of the bridge for its potential to support individual and maternity colonies of bats. Our work included identification of bat species using the bridge utilizing visual surveys and acoustic monitoring methods, installation of bat exclusion devices under the bridge that spanned approximately 1,000-feet, 150-feet above ground, and monitoring and repair of exclusion devices.

Initial work was conducted during a period when the population of bats was at a seasonal minimum (prior to the return of migratory species), and the timing of the demolition was scheduled to coincide with the lower abundance of bats. Professionally operated boom-lifts were used to mitigate safety risks during the installation of the exclusion devices, and the installed exclusion devices were monitored at night when bats are active.

Additionally, the extended period of noise and vibration from demolition created challenges for maintaining the viability of the exclusion devices, and new designs of exclusion devices were formulated to cope with these unique circumstances. Caltrans was able to complete the demolition and reconstruction of this large bridge within schedule, with a relatively low cost allocated for bat protections, all while meeting the environmental standards for the protection of bats mandated by the California Department of Fish and Wildlife.