With the bronze and stone removed, the true breadth of the restora- tion project was revealed. Although the team had taken probes of the monument and determined that the core structure of bricks had been compromised, there were still quite a few unknowns. Although there were extensive surveys of the monument taken and the original drawings were analyzed, the team was still unsure about some of the dimensions of the internal structure such as the distance between the stone and bronze, and how those two elements were connected. Once the bronze was removed, it was clear there was no anchoring between the two elements. With this question answered, the team was able to fit the dimensions of a stainless steel frame to support the vertical section of the monument. In addition, the team installed a stainless steel plate and sleeve to support the bronze legs at the bottom of the statue and prevent lateral movement. Next, the team turned to reinforcing the plaza upon which the monu - ment is viewed. Beneath the plaza there is a series of steel beams spanned by brick arches. When the team first entered the crawl space beneath the plaza, it was immediately clear that there was significant damage to the structure including rust and other signs of deteriora- tion. After this initial survey, the team had to decide whether to rip up the plaza and completely replace the structure or repair the original structure. The team opted to repair the original structure, employing the use of cathodic protection to prevent further deterioration to the steel support beams that were embedded in the brick arches. While cathodic protection does not reduce the damage already done to the structure, the system minimizes or prevents further damage from being done. The team also scraped, cleaned, and applied corrosive-resistant paint to the exposed portions of the steel. With the entire restoration process completed in a little over a year and a half, the monument is scheduled to be rededicated on October 20th, 2021. Through the efforts of the partnership, future generations will be able to explore, learn, and benefit from this historical monument for generations to come. “The actual foundation of the Memorial both in- spired and is at the heart of the restoration efforts. With our Partners the National Park Service, the City of Boston, and the Museum of African American History, we are using our restoration of the Memorial as a platform to explore issues of race, social justice, and inclusive place - making,” said Liz Vizza, president of Friends of the Public Garden on behalf of the Partnership team. “Fortifying the foundation and telling the fuller stories of the public art that inhabits our shared spaces like America’s first public park are catalysts that brings people together, creates community, and furthers a richer and deeper understanding of our shared history and future for many generations to come.”
1980s, the bronze relief was one of the areas of the monument that had succumbed the least to deterioration. Because of the positive state of the relief, there was no need to remove it directly for restoration. However, due to the compromised nature of the substructure, the relief had to be removed to make room for the restoration teams. On top of allowing the team to complete a comprehensive restoration, this off- site removal afforded unique views of the monument that had never been seen before, such as the back, which revealed key insights into the making of the monument. In addition, there was a discolored area in the top left section of the relief that posed somewhat of a mystery to the restoration team. Further analysis showed that the discolored area included a high amount of iron, likely a contamination during the casting process that rose over the years. This analysis gave the team the confidence to correctly fix the area. Much in the same way as the process behind the bronze relief, the team had to make a decision as to where the stone portions of the monument would be restored. Additionally, the team had to decide how much of the stone would be removed for restoration. Ultimately, the team opted to remove roughly 85 percent of the stone in the monument for intensive cleaning and restoration that included things like infill and removal of deteriorated stone, leaving a small portion of stone around the back.
LUKE CAROTHERS is the Editor for Civil + Structural Engineer Media. If you want us to cover your project or want to feature your own article, he can be reached at lcarothers@zweiggroup.com.
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july 2021
csengineermag.com
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