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SCDOT SC-7 Bridge Replacement, Charleston, SC

SCDOT SC-7 Bridge Replacement: Raising More than Just a Bridge

Constructed in the mid-1950s, Charleston’s SC 7 Bridge (Cosgrove Avenue) was in dire need of renovation due to structural integrity issues, eroded pavement and general wear and tear given its significant role serving as a main artery for residents to gain access to portions of North Charleston. As such, SCDOT authorized funds to replace the SC-7 (Cosgrove Avenue) bridge over SCL and Southern Railroads and S-39 in North Charleston. Improvements for this project included replacement of an existing 800-foot bridge with a new bridge, reconstruction of Cosgrove Avenue on both the northern and southern approaches, and reconfiguration and reconstruction of the Cosgrove Avenue/Arapahoe Street intersection.

The scope of the SC-7 bridge included two-stage construction. The first phase was demolition of half of the existing structure over three live railroad tracks and an existing concrete plant, and shoring and removal of approach fill in phases. It included installation of stone columns, earthquake drain, and installation of ten drilled shafts. Once completed, the constructor, Crower Construction, then switched traffic and mobilized to the other side of the structure to produce the same results in phase two.

Specific project scope included field surveys, geotechnical and subsurface utility investigations, geotechnical engineering, conceptual design of the bridge and roadway improvements, preparation of necessary environmental documentation, coordination with affected utilities and the railroad, development of final right-of-way plans, development of both preliminary and final bridge and roadway construction plans, and provision of preconstruction and construction phase support. Hussey Gay Bell was awarded the project in 2009 and was responsible for project management, environmental documentation, field surveys, geotechnical design, bridge design QA/QC, roadway design, MSE wall design, hydraulic design, utility coordination, right-of-way plans preparation, and construction support.

SCDOT SC7 Bridge Replacement
Charleston, SC

Prior to construction of the massive South Carolina Port Access Project in Charleston, two significant bridges in the area that spanned the primary railroad corridor were in dire need of renovation. US 78 at King Street extension and Rivers Avenue was an old aqueduct bridge built in the late 1920s and the SC-7 Bridge (Cosgrove Avenue), which was constructed in the mid-1950s. Because the SC-7 bridge was the detour for the US 78 bridge closure, the bridges had to be built linear – three years later and despite demolition of half of the existing structure over three live railroad tracks and an existing operational concrete plant, the project bridge and its profile achieved signature status.