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SAN JOAQUIN BRIDGE/STATE ROUTE 99 BAT SURVEYS

CALTRANS – FRESNO COUNTY, CA


ABOUT

In partnership with Caltrans District 6 and MCM Construction, QK provided the inspection of the bridge over the San Joaquin River at Highway 99 for its potential to support individual bats and maternity colonies of bats, identify the bat species using the bridge using visual surveys and acoustic monitoring methods, installed bat exclusion devices under the bridge that spanned approximately 1,000 feet and was up to 150 above ground, and monitored and repaired exclusion devices.

APPROACH

QK first conducted visual and acoustical identifications of the species of bats that use the bridge and identified areas of the bridge that were, and could be, used by bats. During a period when the population of bats was at a seasonal minimum (prior to the return of migratory species), exclusion devices were installed. The timing of the demolition was scheduled to coincide with the lower abundance of bats. Large man-lifts were employed and expert operators were used to ameliorate safety risks during the installation of the exclusion devices. The installed exclusion devices were monitored at night when construction was not occurring and when bats are active. All defects or failures of exclusion devices were repaired as soon as identified to prohibit bats from re-invading.

KEY ISSUES

Demolition and replacement of the San Joaquin River bridge at Highway 99 occurred in two phases, with the south-bound lanes being demolished and rebuilt during one phase and the north-bound lanes being demolished and rebuilt during a second phase.  During each phase, bats were excluded from the portions of the bridge to be demolished while allowing bats to continue to inhabit other portions of the bridge.  The extensive length and height of the bridge coupled with a long-term demolition schedule increased the safety risks, and the extended period of noise and vibration from demolition imposed challenges for maintaining the viability of the exclusion devices; new designs of exclusion devices were formulated to cope with these unique circumstances.

RESULTS

Caltrans was able to complete the demolition and reconstruction of this large bridge within the originally scheduled period of time, with a relatively low cost allocated for bat protections, all while meeting the environmental standards for the protection of bats imposed by the California Department of Fish and Wildlife and internal Caltrans requirements.



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