The Sutro Tower is a 1,000-foot-high structure that serves as a transmission facility for 11 television stations, four FM radio stations, and 20 wireless communication services in the San Francisco Bay area.
We were contacted to provide corrosion control and protection for the legs of the tower, which had begun to suffer the effects of exposure to the elements. In addition to repairing the existing corrosion, the client wanted to coat the internal steel structure of the three legs of the tower, as well as the structural components inside two of the three.
There were several unique challenges presented with this project, due to a combination of structural and environmental factors, which we met with thorough preparation and careful planning.
Within this unusual structure, there were a number of difficulties presented by the construction of the tower, as well as the natural environment:
- Weather patterns. Due to the height and the location on the bay, the tower was frequently surrounded by fog. Moisture, such as that produced by fog, prevents paint from adhering. We kept crews on standby, constantly checking the weather for a break in the fog.
- Tower access. The elevator that goes to the top of the Sutro Tower is only big enough for two people, or one person with tools and paint. Additionally, it takes several minutes for a one-way trip. This meant bringing a handful of crew members up or down took around 30 minutes each time.
- Leg access. To reach the interior structure of the legs, our crew members had to climb in from the top, wearing a full body harness connected to the structure. Paint and tools also had to be secured in place, and frequent return trips to the platform for more paint were required.
- Tight fits. Space was extremely limited inside the legs. Our crew members had to wear respiratory protection to avoid inhaling fumes and particles.
- Safety was essential. We used extensive fall protection measures, held daily safety checks and meetings, and employed an on-site safety director.
- To remove existing rust and form a profile on the steel surfaces that would allow the new coating to adhere properly, we used a grinding method to prep large surfaces, and needle-nosed guns for small corners and tight areas.
- Immediately following prep, we applied a rust-inhibiting epoxy coating to the surfaces to prevent flash rust from the extremely humid environment.
- In order to minimize the structure’s exposure to humidity, we divided the process between two teams—one to prep the surfaces, and the next directly behind them to apply the first coating of epoxy.
- Following the initial phase, we applied additional coats of epoxy to provide superior protection.
The client was extremely satisfied with the results, and the manner in which our crews observed rigorous standards of safety and quality. We completed the first two legs of the tower on time and within budget, and currently await the next phase to address the third leg, as well as additional work on the structure as budgeted.
The epoxy coating we applied to the Sutro Tower will provide rust protection for 10 years before re-coating becomes necessary.