This presentation is part of the International Cemetery Preservation Summit, April 8-10, 2014 Niagara Falls, NY.

Conserving the Nation’s Gravesite: Treatment of the Tomb of the Unknowns at Arlington National Cemetery by Debora Rodrigues and Amy Hollis

Amy Hollis: I’m going to talk a little bit about a job that I lived for a couple years, which was about a year longer than I expected at the beginning. I’m going to give you a little bit of the background on the Tomb of the Unknowns first. The World War I unknown soldier was entombed in 1921. The photo on the left is a photo of that ceremony. The die block wasn’t quarried until 1930, when it was transported from Colorado to Vermont for sculpting in the studio of Thomas Jones. Once it was finished, the final weight is 48 tons. I’m not sure I have a really accurate number on where it started, but it was more than 48 tons. At the time it was the largest block of marble ever quarried.

In 1931, after a design competition for the monument and the surrounding area in front of the amphitheater, the sub base, die block and cap stone were installed. The photo on the left is about how it sat for 10 years before they rearranged the plaza and installed the new monument. The sketches on the right are from a 1963 pictorial survey by Wiilie Arnheim, who was a stone mason and a construction manager in the D.C. area in the latter half of the 20th century. He worked on the Capital and a lot of monumental buildings in D.C. As early as 1963, the cracks that developed in the marble die block were documented. In the solid lines in these drawings are where Mr. Arnheim observed the cracks. He had added black dotted lines where he thought they would continue to extend, and the red lines are reference to show how far they had extended when we were on site, and they did pretty much extend exactly in the places that he expected them to.

Treatment of the Tomb of the Unknowns

Treatment of the Tomb of the Unknowns

We have correspondents that said that the cracks had significantly extended between 1963 and 1975 by a total of 6 feet and cosmetic repairs had been implemented. It’s not really clear exactly what those repairs were from this correspondence. In 1990, Mary Orlin did a fantastic report with some research on the tomb, which culminated in a repair cycle. Included in that is a brief geologist’s report that discussed potential causes. They felt like it was a possibility that there was some geological feature within the stone that was causing the crack, but they couldn’t say that for sure. Then there was an engineer’s report that determined that the stone did have inconsistent densities throughout, which makes a lot of sense. When you look at the stone you can see that there’s quite a bit of veining in it, which made the repairs actually pretty forgiving.

The 1990 repair filled the cracks with a type O mortar, which is twice as much lime as Portland cement, but there was a little bit of a Portland cement component in it, and it did have an Acryl 60 additive, which acts as a bonding agent and also helps keep the mortar from shrinking. This is frowned upon now, because it’s an acrylic additive and it prevents water vapor from passing through the mortar joints, so we try to avoid using that. More modern history of the monument, 2003 a car dealer in Colorado essentially rented the Yule quarry. It had been closed for a few years, and had a new die block quarried for the monument. Presumably he knew about the cracks and knew that the cemetery was exploring the possibility of replacement. This particular stone had a flaw in it that made it unsuitable for use at the tomb, but they did repurpose it for a likeness of George H. W. Bush.

In 2005, they quarried a new block that was presumed suitable, and that was donated. In 2006, Arlington Cemetery publishes a report that states that they prefer to replace the stone rather than repair it indefinitely, but in 2007 the Defense Authorization Act was amended to require further study in an independent report on repair versus replacement. It did authorize replacement in the meantime. In 2008, a 106 review was initiated regarding the repair versus replacement of the die block. I kind of want to stop for a second and explain that this sort of back and forth was described to me as a “battle,” appropriately enough. I think what was important for us as the contractors to remember is that each group was trying to arrive at the appropriate place to honor this site and these soldiers. I think that people at the cemetery felt that the best way to honor these soldiers was to have a pristine, perfect monument in place.

As a preservationist, I certainly understand the need to retain this original material and honor the sculptor, and the architect, and the original intent of this site as well, but we did want to be sensitive to the cemetery’s needs. In 2009, the plans to repair the monument were announced, and our company was awarded the contract to do that. It was a very standard marble repair. Clean it, there was biological growth so they wanted the stains removed from that. A lot of atmospheric pollution in the area, it’s right across the river from D.C. in a fairly urban area. Even though it is of the rural design cemeteries, we were going to cut out the deteriorated edge of the joints a repoint, remove the old repairs that had become discolored and detached from the sides of the cracks, and then fill the cracks with grout. For this particular project, grout is sort of a generic term, mortar is sort of a generic term. It was all technically mortar, but for clarity’s sake, when discussing the project we called everything that went in the joints “mortar,” and everything that went in the cracks “grout,” so that we were just clear on what we were talking about and which final formula we were talking about.

It’s a very standard repair, but a very non-standard location and circumstances. We worked outside of public hours, which meant we worked at night, which is why all these photos are very dramatic. The first go around was a very cloak and dagger affair, I think that the cemetery was very worried about the visitor experience being impacted by these repairs. They didn’t want it being a distraction, it’s a very solemn and meditative site. People, sometimes this might be the only time they come to Arlington in their entire lives, they didn’t want anybody to feel like they missed an opportunity to see this monument the way it’s meant to be seen. Part of that was we left no evidence after each shift that we were there, so we showed up at 8:00 at night after the last visitor had left, and we left at 2 or 3 in the morning and took everything. Every ladder, every piece of plastic, swept up every little bit of mortar and grout that we left on the plaza, and hosed everything down before we left so that there was no evidence of us being there.

David Davis

David Davis

We worked as quickly as possible. We had to respect the traditions and the custom of the site, obviously. We had to wait until the guard in uniform came off the plaza. We waited, but if we hadn’t waited they promised that the reaction would be swift and uncomfortable. We were pretty careful to wait, because we didn’t want to be uncomfortable. We had to wait for someone to come out in camouflage to be on post so that it was not a formal posting of a guard. There were places on the plaza that we could not walk, especially the area right around the ledgers that are in front of the monument for Korea, Vietnam, and World War II. All requests for information had to be forwarded through the cemetery or the Baltimore district of the Corps of Engineers, who were our contracting officers.

These were our constituents, the Corps of Engineers, and the National Cemetery. That was pretty much it, so the people we talked to are on this screen. We had a contract officer and a technical officer from Baltimore, and Superintendent Metzler and the Tomb Guards. Our plan was to clean with a gentle detergent and biocide. Here are some pictures of our cleaner testing. Mortar was a lime mortar only, lime and masonry sand. The grout was also a lime formula, with marble dust as the aragum. In April of 2010, we came with our cones and our ladders, and we made sure we didn’t walk where we weren’t supposed to walk. We cleaned up the biological growth on all the undercuts. We filled the cracks, filled the joints. While the cracks were open, we had photogrammetry done so we could document the exact extent of the cracks, including the width of the cracks all the way around.

Final Inspection

Final Inspection

At the end of April, we were extremely proud of this repair. It was flush with the surface of the monument all the way around. You had to get pretty close to see these repairs, within 2 feet maybe before you could tell where they were. I put some of these repairs in, and I was having a hard time finding them until I got the light to hit it just the right way. We sculpted around the letters to make sure that we didn’t leave a lot of evidence of our repair. We thought, “Wow this is great, we’re writing up our project profile, we’re going to put it on the website,” and then we got a phone call. Their October inspection showed that the grout was falling away from the cracks. I briefly considered witness protection, but then decided to get down to business. We asked ourselves why, and the cemetery, and the Corps of Engineers, the army, is asking us, “Why? Why are these failing?”

We looked at site conditions, temperature, maybe the temperature was wrong, it was too humid, not humid enough. We talked about materials, maybe individual components were not appropriate. Maybe the proportions were not right for this particular repair. The execution, it was possibly too dry, we were not again, we weren’t allowed to leave any evidence of our work on site during the day, so when we left we couldn’t cover our lime repairs. We tried to compensate for this by essentially only doing a half shift of repair, so we would do 4 hours of repair and then spend the next 4 hours misting and babysitting the repairs so that hopefully we could impart enough moisture to it to get it through the day and cure it before it dried out.

The army is wanting an explanation, so we had some marble samples laying around our yard from other restorations, so I took some samples. This is Beaver Dam marble, which for the length of these material trials was a pretty good match for physical properties. We cut channels in the stones approximately the size of the cracks, and I put them in 2 different environments. One was warm temperature range, and another went in a cool temperature range, so we’re trying to decide if there’s a temperature that’s going to work for these repairs. Then one of each of those was misted and covered for a week, and the other one of each environment was left exposed. They were also misted every day, but they were exposed and that probably more accurately represented how we had treated the repairs on site in the first place.


Then the different formulas, for control we put the mortar that we used and the grout that we used exactly in these first 2 channels. The mortar had not failed, so we wanted to put that in there to make sure that we knew exactly what was happening with the mortar as well, and then we put in the grout formula as a control. We tried a different lime. I had used a high calcium lime in the monument, so we tried a regular mason’s lime with more magnesium in it. We tried different proportions of cement added in, just to see if we needed that little boost of a Portland cement inserted. For a week I controlled the temperatures, babysat them, covered them, nurtured them, and then I threw them outside for 3 months and let them fend for themselves. All the purely lime formulas failed within those 3 months, and a couple of them failed within the second day. A bunch of them failed within that first week, and then there were just a few outliers that lasted outside for a little while.

All this time, we’re still trying to communicate with the Baltimore Corps of Engineers about what we’re doing and why it’s taking me so long to give them an answer. Meanwhile, Arlington is going through its own transitions. Interestingly enough, in our final inspection in April, Superintendent Metzler did not attend, and a couple days later the announcement of his retirement came out. Katherine Condon was then installed as the Executive Officer. The cemetery management itself transferred from the Baltimore District of the Corps of Engineers to the Norfolk District. The client’s new project manager was a Lieutenant Colonel and Deputy Commander of the Norfolk District. If you can swing it, I highly recommend having a Lieutenant Colonel as your project manager. If you need something, it appears immediately. If you need to get on site a little earlier, you have permission immediately. That worked out really nicely. Also the Memorial Day plans are underway and they’re worried about having pressed benches up really close to the monument and they’re worried that people are going to notice that now it’s missing material.

In the end, they decided to wait until after Memorial Day, because it was just too much to coordinate for them. It’s their biggest event of the year, so really they just wanted to concentrate on what they needed to get assembled and tabled the repair for a little while. Our list of constituents broadened significantly. This was quite a conference call. Some of you here were on that conference call, you can back me up. We had a lot more arts agencies, and government agencies, and preservation organizations, and military agencies involved with this process now. It was very scary at first, because we had a very narrow line of communication for the first go round, and it was scary to open it up to so many other people, but this turned out to be a really open, really helpful process. We had input from a lot of people. The way that the Norfolk District decided to manage it, I mean this was part of the conversation of the conference call as well, that we split up essentially into 2 teams.

Repair Reprise

Repair Reprise

There was a technical team, which included us as the contractor. NCPTT, Mary Striegel was very involved in this, and I know Jason was involved as well. Park Service, Dennis Montanya was very active in this process, and Norman Weiss and Richard Peiper, who are private conservators but also teach at Columbia University, were fantastic advisers. We ended up doing a little bit of everything. We tweaked the material themselves, we ended up with a type ) mortar like the 1990 repairs. We did add a little bit of cement, and then we changed the particle size of the aggregate a little bit to make it more compatible. The public relations team was made up of the Norfolk District Film Crew, who did a fantastic job of producing videos, and YouTube slideshows, and putting out press releases. The Cemetery, Army Heritage, National Trust, Commission for Fine Arts, all contributed to these. There was lots of information on the National Trust website, and there were videos and materials in the Arlington National Cemetery visitor center to let visitors know what was going on at night while they weren’t there.

We had some new materials, I did some new samples. The guys in the shop were a lot happier with the smaller pieces of marble that they didn’t have to carry back and forth. Because we were working at night, we had new color issues to deal with. We did have daylight temperature bulbs to work with on site at night, but it’s still not really daylight, and you can’t trust the color comparisons that you’re seeing with these bulbs, so it was important for us to make little furtive visits during the day and get permission to take samples over to the Tomb and compare colors, so that’s what that bottom image is of, just some samples of different proportions of these larger and smaller aggregates mixed together and what difference that made to the color. It might not look like it in the slide, but they are really 3 different color.
In September we went back to take out our old repairs and put in our new ones. We ended up taking out the mortar in the joints as well. It was a pretty easy remove with the lime mortar, but it looked like it had shown some weathering on some of the skyward facing joints, and we just didn’t feel comfortable leaving that to weather that way, so we ended up putting a type O mortar back in the joints, as well. You can see that it was pretty hot, I’m not sure if we’re sweating from the temperature, or the stress because the aggregate had not arrived on time. I just had what was left over from the material trials that we had done. Fortunately, that turned out to be enough, but if anybody needs 40 pounds of crushed marble, I have a bag for you. The final results I think we’re good. Did we get the same kind of aesthetic repair as we did the first time? No, we didn’t.

Final Results

Final Results

It’s aesthetically good from the viewing area, which was mandatory. Back from where the viewers can approach the Tomb, it’s still really difficult to find the repairs. Up close, you can see some unevenness. We had some problems getting that perfectly smooth surface with a larger aggregate. We serendipitously were able to document the stone prior to and almost immediately after the large earthquake in 2011, so we have good data and measurements from the effects of the earthquake that we can observe. My information is that this 106 review for replacement of the die block has been withdrawn, so repair’s the way they plan on going forward with the monument from now on.

I’d like to take a minute to recognize Dave Davis. He’s the mason that worked with me on this project, and he passed away last year. He was an amazing artist with paint, pencil, or mortar, and I’ve never seen a repair that he could not do, so thank you.


The common practice at national cemeteries across the country is to replace marble headstones when they are damaged and can no longer be read. When the long-developing crack in Tomb of the Unknowns became obvious, Arlington National Cemetery made preparations to replace the die block in the monument, in accordance with their usual policies. In the meantime, the crack would be filled and camouflaged so that the average visitor would be unaware of the damage. Such a repair was carried out in 1990, while a separate campaign to acquire new stone proceeded.

Thus began a debate that has involved Arlington Cemetery, the U.S. Army Corps of Engineers, members of Congress, advisors from organizations throughout preservation and conservation organizations, and grass-roots efforts to preserve the monument rather than replace it. While the plan to replace the stone was delayed in 106 review, it became necessary to do something beyond the standard seasonal maintenance. The repair project was put out to bid, and ultimately Architectural Preservation Services, LLC (APS) was awarded the USACE contract. The work was carried out according to specifications in April, 2010, without publicity and with the express desire to have no evidence of the work that was occurring: perform the treatment at night, no covering, no scaffolding. Even with the constraints, by all accounts, the resulting repair was thought to be successful.

Soon after, Arlington National Cemetery went through an internal upheaval and public scandal. In the meantime, in November of 2010, conservators were informed that the installed formula was falling out on one side of the Tomb of the Unknowns. After a site visit, it was clear that the fill formula was failing around the entire monument. APS drafted a response with hypotheses about the failure, and evaluated various materials, temperature ranges, and moisture levels to confirm or refute those hypotheses. Based on the results and discussions with the Corps of Engineers, conservators were prepared to re-repair the Tomb in the spring of 2011. By this time, another internal shift was taking place, albeit on a more subtle level: ANC was being transferred from one USACE district to another. This final change essentially meant an entirely new project: new client, new facilitator, new project philosophy.

As the temperatures began to climb, the project was again tentatively postponed until the fall, allowing time to involve a panel of subject matter experts, representatives of the aforementioned organizations, in a series of conference calls. The results of the first of these calls was to take a two pronged approach; a technical group would discuss the issues involving a new treatment and develop a new formula, while an outreach group to develop a strategy to inform the public and the preservation community about the treatment, including using social media such as Facebook, Twitter and YouTube. Phase II was a very public and collaborative process.

This presentation seeks to discuss the two treatment phases of the project and how the differences in public outreach and community discussion affected the technical matters of the repair and vice versa.

Speaker Bio

Debora Rodrigues is President/Senior Conservator at Architectural Preservation Services, LLC. In 2008, Rodrigues started Architectural Preservation Services, LLC, a new conservation division of Worcester Eisenbrandt, Inc. (WEI). Prior to joining WEI, Ms. Rodrigues was the Preservation Manager/Senior Architectural Conservator for the Mission of San Juan Capistrano in Southern California. She also worked for the Aga Khan Trust for Culture, Historic Cities Support Programme in Cairo, Egypt, as well as the National Park Service, Yale University, University of Pennsylvania, Columbia University (in Yemen), and several privately-owned conservation firms. Ms. Rodrigues holds three degrees from the University of Pennsylvania: a Bachelor of Arts in Design of the Environment, a Master of Science in Historic Preservation, and a post-graduate Advanced Certificate in Architectural Conservation.

Amy Hollis is an Architectural Conservator with Architectural Preservation Services, LLC. Hollis joined APS in 2009, adding her conservation and restoration experience throughout the southeast and mid-Atlantic. In addition to private conservation work on monuments and cemeteries, Ms. Hollis managed the preservation of the forty Gilded Age historic buildings within the Jekyll Island Club National Historic Landmark District, as well as the colonial Horton House site, and Spanish-American War gun batteries. She holds a Bachelor of Fine Arts in Design with a Minor in Art and Architectural History from James Madison University and a Master of Fine Arts in Historic Preservation from Savannah College of Art & Design.

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