US 21 over Harbor River Bridge Replacement – Beaufort County, SC

The Design-Build project consisted of replacing the existing swing-span bridge over a tidal waterway / navigable channel which serves as the only means for vehicular transportation from the mainland to Harbor and Fripp islands. The new high-level 3,353 foot long fixed-span Harbor River bridge provides uninterrupted access for shrimping and sailing vessels along the river below as well as provide improved safety for motorists crossing the bridge itself. The replacement bridge has two 12′ wide lanes with 10′ paved shoulders in each direction, providing 90′ of horizontal and 65′ vertical clearance for river navigation.

As the Lead Design Firm on the Design-Build team, ICE provided preliminary and final roadway and bridge design and plan preparation. These services included MOT and signing; drainage and erosion control; 2D modeling, hydraulic, and scour analysis; structures; and utility coordination. ICE also provided geotechnical peer review and project soil structure interaction support, HAZMAT monitoring and testing, survey and SUE, community and public relations, permitting and environmental compliance, right-of-way acquisition, and construction support services.

Notable Accomplishments:

  • The Design Build Team submitted 10 Alternative Technical Concepts (ATCs) to SCDOT and received approval of nine of those resulting in a costs savings of over $6 Million.
  • To protect the environment, the Team devised an innovative scheme for construction staging which resulted in the reduction of nearly 30% of wetland impacts.
  • Final RFC plans were completed, submitted and accepted in advance of the permit.
  • ICE’s in-house geotechnical engineers successfully led the project’s bi-direction static load test program on the demonstration 8-ft diameter drilled shaft. ICE’s in-house geotechnical engineers are currently performing PDA testing on the project’s driven concrete and timber piles along with performing vibration monitoring and preconditions assessments on adjacent structures.
  • ICE Environmental Specialists provided various support during construction and demolition, including development and implementation of appropriate environmental work plans associated with nest monitoring for Bald Eagles and marine mammal protection.