Stan Gober Memorial Bridge
Services Applied by VCS Engineering
Summary
The Stan Gober Memorial Bridge carries County Route 92 (San Marco Road) over the Marco Channel in Collier County, Florida. The two-lane bridge consists of 22 spans supported by prestressed concrete girders on cast-in-place reinforced concrete columns, footers, and piles.
Because of the bridge’s severe marine exposure, the Owner hired Cardno and VCS to evaluate the structure’s condition and develop a rehabilitation plan that will significantly extend its service life. The primary focus of the work was the substructure elements, which are directly exposed to the marine environment. An interesting aspect of this bridge is that a marina is located at the west end. Due to the proximity of the boat launch, the bridge deck is regularly exposed to seawater dripping from boats driven over the bridge immediately after being removed from the water. This has resulted in chloride contamination of the deck — an uncommon issue in Florida, since the state does not use de-icing chemicals like northern states.
Scope
For the substructure elements and beams, VCS performed corrosion potential measurements to determine the extent of active steel reinforcement corrosion. In addition, VCS collected concrete samples for evaluation of compressive strength, chloride concentration, and petrographic analysis. On the deck, VCS performed corrosion potential measurements, collected samples, and implemented ground-penetrating radar (GPR) scans to rapidly and non-destructively identify areas of potential deterioration.
Solution
Because of the bridge’s chloride exposure and marine environment, corrosion was found to be active in most of the bridge elements, including the piles, footers, columns, girder ends, and portions of the deck. The section of deck closest to the marina had very high chloride contents and visible concrete damage. This portion of the deck will be removed and replaced, while the remaining deck area will be treated with a saline sealer to help block moisture and chlorides and extend its service life.
The girder ends, which are exposed to water and salt through the expansion joints and marine air, will receive zinc metalizing to provide cathodic protection to the beam-end reinforcement. The substructure columns, footers, and piles will be protected with galvanic cathodic protection jackets, which will both halt corrosion and serve as a barrier to further deterioration.
VCS and Cardno worked together to develop a design package for this rehabilitation work, which will be issued to contractors in Florida for bidding.
