Golden Gate Bridge Seismic Retrofit

Drill Tech was contracted to aid in the seismic retrofit of the Golden Gate Bridge, specifically to work on the South Anchorage House and the first two pylons at the Fort Point Arch. The project considered of drilling and water testing the drilled holes, as well as the installation, grouting, and testing of over 150 large capacity tie-down anchors. Each anchor was epoxy coated, which demanded an increased level of care and protection during installation than non-epoxy strands. The location’s proximity to water and low overhead clearance required precise handling of the large multi-stand anchors and frequent grouting and re-drilling to ensure water-tight holes.

Drill Tech built proprietary drilling equipment to accommodate the tight access and constructed numerous work platforms with different configurations to support tie-down drilling, installation, and testing. The anchor holes were drilled into the bedrock with down-the-hole hammers and high-pressure air, and the spoils were collected at the mouths of the holes with a closed venturi collection system. Installing the anchors required cranes and pulley systems alongside multiple pick points and special rigging. ChemGrout plants were used for tremie grouting the anchors, and testing was performed with hydraulic rams and monitored with load cells.