Dennis O'Shea Dennis O'Shea is a former Assistant Director of Design for DelDOT with more than 22 years of experience in bridge design and management.

The reason for replacing the bridge is the severe scouring that has taken place over the years, resulting in an Inlet depth of approximately 28 feet in 1965, to an Inlet depth greater than 100 feet today. The Army Corps first reported evidence of significant scouring in the 1980s after an underwater survey indicated that the bridge supports, also known as piers, in the Inlet were exposed and undermined.

An additional concern related to the scour is the exposure of the steel H piles to salt water. H- Piles are the support piles for the piers. Water, especially salt water, is detrimental to steel. DelDOT attempted to control the condition of the steel piles by installing a protection system to the piles. Unfortunately, this system has been problematic and the exposed steel support piles are continuing to corrode, losing strength.

To ensure the bridge remains stable before a new bridge is built, DelDOT performs underwater diver inspections on a regular basis and the Corps has continued to provide DelDOT with their periodic bathymetric surveys. The technology has improved over the years allowing the viewer to see an underwater picture of the site (go to the Web site to view). In addition, land survey equipment on the bridge monitors movement.

Progress Continues

Much has been accomplished since DelDOT decided to not accept bids for the signature arch bridge in October 2005. As you will recall, only one bidder expressed interest and that bid was coming in higher than DelDOT was willing to accept. Despite that setback, DelDOT regrouped and chose to use a method called design-build in which a team of bridge design engineers and bridge construction contractors are selected and are responsible for both the design and construction, meeting predetermined design criteria.

In June 2008, DelDOT selected Skanska USA Civil Southeast Inc., a very capable and experienced bridge builder to construct the new Indian River Inlet Bridge.

To completely eliminate the concern over scouring, a requirement for the design-build bridge is to span the Inlet entirely, providing no supports in the Inlet. The supports will also be located to allow the Corps to widen the Inlet if they chose.

We believe that the current funding already in place for this bridge project should be adequate. The majority of the funds have come from federal funding through appropriations specifically for this bridge and specific bridge replacement funding.

The public can be assured we will continue to keep them updated as we move forward with this vital project.

Related Documents

• Purpose and Need  
• 57 Years of Coastal Engineering Practices at a Problem Inlet: 1992 Report (Army Corps of Engineers)  
• "Indian River Inlet: An Evaluation by the Committee on Tidal Hydraulics", July 1994 (Army Corps of Engineers)  
• January 2006 Bathymetric Survey Raw Data (Army Corps of Engineers)  

Images
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1999 Bathymetric Survey (Army Corps of Engineers)	2004 Bathymetric Survey (Army Corps of Engineers)
1999 Bathymetric Survey (Army Corps of Engineers)	2004 Bathymetric Survey (Army Corps of Engineers)
1999 Bathymetric Survey (Army Corps of Engineers)	2004 Bathymetric Survey (Army Corps of Engineers)
1999 Bathymetric Survey Plan View (Army Corp of Engineers)	1999 Bathymetric Survey Looking East (Army Corp of Engineers)
2003 Aerial View (Army Corp of Engineers)	2004 Bathymetric Survey Looking East (Army Corp of Engineers)
2004 Bathymetric Survey Looking West (Army Corp of Engineers)	2007 Fathometer Survey (Army Corp of Engineers)