Gran Bretaña, Villanueva
Bridge
The existing bridge at Gran Bretaña is known as the Swayback Bridge. It is a two-span (11m and 18m) steel girder, reinforced concrete structure constructed between 2007 and 2007. During the floods of Hurricane Felix in September 2007, the center pier was undermined and settled approximately half a meter with a slight cant downstream.
Municipality engineers report the pier is founded on a spread footing whose base is approximately two and a half (2 ½ m) meters below the stream bed. The basic structure of each span is a pair of I-beams salvaged from a dismantled bridge in the municipality.
No foundation investigation was completed. The municipality has no equipment for conducting sub-soil investigations. The bridge could not be skewed to closely conform with the stream alignments and the available superstructure. The center pier is skewed for the stream flow creating eddies during high flows.
Global Community Development proposes to inject a mix of Portland Cement with fine to medium sand under air pressure under and around the pier footing to create a bubble of nonerodable material. A grout curtain, similarly created, should also be built in front of each abutment to prevent further scour.