Texas Border Business
BROWNSVILLE – The Texas Department of Transportation is currently replacing concrete rail on state road SH 48 in Cameron County. The project, known as the Bahia Grande Project, aims to replace the outside concrete walls of the road, which indirectly created a downward draft (see background) during cold fronts. The air “vortex” caused numbers of brown pelicans to land on the roadway.
Since the project is not yet complete, it is very possible that the overnight cold front may result in several brown pelicans to appear on SH 48 in the Bahia Grande area. We urge drivers to exercise extra precautions and be extra attentive to the road. Furthermore, we are asking anglers not to park inside the construction area since this can compromise safety for them and for the contractor.
In the meantime, proposed safety measures include
BACKGROUND:
The Bahia Grande Wetland Complex in Cameron County, Texas was acquired by the USFWS as part of the Laguna Madre National Wildlife Refuge in 2000. Efforts to restore this area from a dry, barren basin to a functional coastal estuary have been underway since that time. In 2009, the widening of and improvements to SH 48 were completed and the brown pelicans were removed from the U.S. Endangered Species List.
As part of this improvement project and in anticipation of USFWS Bahia Grande restoration, two new bridges were constructed. One replaced an existing bridge at San Martin Cut, and the other was over the then proposed Bahia Grande Restoration Channel. In 2005, a small pilot channel with a 15-foot bottom width was dug to reestablish a tidal connection between the Bahia Grande and the Laguna Madre via the Brownsville Ship Channel. Upon completion in 2009 of the new SH 48 bridge, culverts were removed, and the pilot channel was widened.
Reports of pelicans being killed go back to at least 2011. Incidental reports and observations indicate that mortality events have ranged from several individuals to dozens of dead birds, which occur in geographically discreet locations and under certain weather conditions: those being strong (>20 mph) north winds, cold temperatures, and overcast or rainy conditions.
“Pelican poles” were installed on the two bridges in January 2015 to encourage the birds to gain more altitude while traversing the bridges. A systematic roadkill study conducted in 2015 and 2016 seemed to indicate the poles were working to some degree but may have been deflecting the birds around, instead of over, the poles.
Using an extensive study for alternative barrier analysis using computational fluid dynamics, the Texas A&M Transportation Institute determined the feasibility of replacing outside walls to reduce a negative air phenomenon which creates a vortex that prevents the brown pelican from getting the lift needed to take off. A new outside rail was designed and TxDOT expects to have the project concluded by the end of Fall 2019.
