Project Location: Seaholm Substation, Austin, Texas
Client: Austin Electric Utility Department; Austin, Texas
Dates: May-1997

The City of Austin is extending the existing South first Street for a total length of about 10,000 ft south of its current termination. The roadway covers a total width of 120 ft, carrying four lanes of traffic, two bike lanes, two pedestrian sidewalks, and a median of 20-ft width. Two bridges of about 500 ft and 400 ft lengths are necessary for the crossings of the new roadway over Slaughter Creek and Nichols Branch Creek. The roadway crossings are designed with twin-bridge structures over the creek, each bridge with a width of 39 ft, each carrying two lanes of traffic, a bike lane, and a pedestrian sidewalk.

The foundation for a 135-MVA auto-transformer of the Seaholm Substation consists of a 51-ft x 12-ft x 6-ft rigid slab resting on topsoil and two drilled piers, each with an outside diameter of 6 feet. A containment pond with an approximate capacity of 30,000 gallons surrounds the foundation. Damages were induced to both structures during a fire in February of 1997. Engineers from LCR&A were contracted to design the retrofit of the damaged foundation and containment slab structures. Compression tests were performed on concrete specimens drilled from various parts of the damaged structures. The report included petrographic, chemical, and scanning electron microscopy studies of the distressed concrete. Tension tests were performed on exposed samples of the reinforcing steel.