The existing Indian River Inlet Bridge was replaced in 2012 with a four-lane, cable-stayed bridge consisting of a 950’main span and a total length of 2,600’. The previous bridge, originally constructed in 1965 and widened with a twin structure in 1976, had a main span of 250’. In 1965, the Inlet was 23’ deep. Inlet currents up to 15 knots led to scouring of the piers, which was first observed in the 1980s. Even with the installation of protective riprap around the piers, scouring had increased the inlet’s depth to more than 100’ by 1990. The increasing possibility of a bridge failure and disruption to heavy traffic led to the need for a new crossing with a longer channel span.
A key component to the new bridge’s construction was the demolition of the existing bridge. Due to the swift, alternating current in the channel and poor soil conditions along the banks, conventional methods of removal using barges and cranes were not allowed. Furthermore, the use of barges would block navigation through the Inlet. Consequently, the engineers from Summit Engineering proposed a construction technique that had never been done before in Delaware State history.
Summit Engineering developed a unique reverse launching system designed to remove each half of the northbound and south bound bridges. Each bridge was strengthened with a unique "Queen Post" system; cut in half over the inlet channel; and then raised with hydraulic jacks and placed on rollers. The bridges’ half sections were finally pulled from the channel by rolling the spans onto the banks of the Indian River where they were then cut up for scrap.
The new signature bridge was opened on time; however, the back story - the demolition of the existing bridge - is yet another example of the innovative thinking that Summit Engineering brings to our construction partners. The innovative demolition technique was developed to address the conditions of the site, environmental constraints, and the needs of highway and waterway users.
No one’s gotten hurt, nothing has broken, it has been extraordinary to watch. - Jim Westoff, Delaware DOT
Gregg A. Reese, PE (Project Principal)