Hotel Indigo Excavation Update: The Ship, Post-Excavation

The long process of conservation, documentation, public interpretation, and research has begun.

Page archived as of March 11, 2019

Note: The information on this page reflects the state of knowledge when this update was written. Information may have changed. 

The Ship, Post-Excavation

May 2016

Conservation

After excavating and disassembling the ship in January, it was transported to a facility here in the city and placed into two large tanks of water to begin the long conservation process. Because the ship sank and then was buried below the water table, it has been in a stable, consistent, anaerobic or oxygen-free environment for the last 200 years. Here, you can see against the wall and above the orange pipe the previous ground level in relation to the depth of the ship. Without oxygen, the bacteria, mold, and fungi that would otherwise begin to break apart and decompose the wood cannot live. Being buried and submerged has kept the wood from freezing and thawing or alternating between drying out and rewetting, both processes act to physically break apart the structure of the wood. Once re-exposed by archaeologists to oxygen and to the elements, the ship’s timbers would rapidly break down and fall apart if left untreated. For this reason, it was necessary to quickly document the ship in the ground before taking it apart and removing it to a more stable environment. 

220 S Union May Update Ship at Ground Level

Like the 1755 John Carlyle warehouse excavated before it, storing the timbers in tanks of water serves two purposes. First, the water acts to physically stabilize the wood. Because the wood has been soaking in water for the last 200 years, the tiny spaces within and between the cells of the wood are filled with and supported by water. If we were to remove this water all at once, much of the structural support keeping the wood together would be lost. We saw this process on site in the weeks between when the ship was exposed and when it was excavated. As the timbers dried out, the edges became fragile and started to crack. To combat this, archaeologists on site regularly sprayed the wood with water and covered it at night with sheets of black plastic to trap the condensation.

220 S Union May Update Tank (1)

220 S Union May Update: Cracks

220 S Union May Update: Spraying Water

Second, by storing the wood in tanks of water we can both clean and chemically stabilize the wood as well. During their use as a ship and since being buried, the ship’s timbers have absorbed salts and metals and other elements from the soil that are harmful to their stability. Every few weeks, Alexandria Archaeology drains and refills the tanks with clean water in order to remove these foreign components from the timbers. This “purging” process can last as long as several years, depending on how much foreign material the timbers have absorbed, the porosity of the wood is, and how often we drain and refill the tanks.

220 S Union May Update: Tank (2)

Just like the warehouse, after the wood is physically and chemically stable, the next step in the conservation of the ship involves removing all of the water from the wood and replacing it with a chemical called polyethylene glycol (or PEG). The PEG will help retain the physical stability of the wood without evaporating like water. Lastly the wood will be freeze-dried in order to remove any remaining traces of water. 

Alexandria Archaeology is currently putting together a request for proposals for finding a conservation facility to take over and complete the conservation of the ship. Once it is properly conserved and stable, the ship will hopefully return to Alexandria for long-term interpretation and display. 

Documentation

In mid-April, we had to take the timbers out of the tanks in order to install liners in the tanks. This was important to do in order to prevent the water and wood from coming into contact with the sides of the metal tank, which can leech harmful metallic ions into the ship’s timbers. We took this opportunity to lay out each timber as it was originally found and to document each part of the ship in a warmer, drier, and less hurried setting. Archaeologists and volunteers from Alexandria Archaeology and the Naval History & Heritage Command spent a week in mid-April laying out the ship on the floor of the storage facility and going over every inch of every timber . We examined, measured, drew, photographed, and inventoried the parts of the ship and we now have a detailed record of many of the ship’s timbers and a descriptive inventory of the rest. From these, researchers will be able to continue research the finer points of how the builders constructed the ship, which may allow us to eventually identify the ship and its makers. 

220 S Union May Update: Measuring (1)

220 S Union May Update: Measuring (2)

220 S Union May Update: Measuring (3)

220 S Union May Update: Measuring (4)

220 S Union May Update: Measuring (5)

In addition to these records of the ship, we also have a pair of digital datasets that we recorded while the ship was still in the ground. The first of these is a digital model of the ship as it was discovered produced by stitching together many photographs of the ship taken from slightly different—but overlapping—angles. Known as photogrammetry, this process is a quick and efficient way for us to produce a 3D model of the ship before we dismantled it.

220 S Union May Update: Photogrammetry

The second of these digital datasets comes from a series of laser scans conducted as the ship was being excavated. Laser scanning works by aiming a pulse of light at a specific point on the ship, timing how long it takes to travel to the ship, reflect off of the ship, and return to the scanner, and then converting that time into a distance using the equation: distance = speed of light * time / 2. Repeating this process hundreds of thousands or even millions of times across the entire surface of the ship, we were able to obtain an extremely accurate and precise digital model that records each layer of the ship. This scan was made after the frame of the ship was completely exposed and contains 43,857,638 individual points recorded on and around the ship.    

220 S Union May Update: Lidar


Public Interpretation

Because we had to take the timbers out of the tanks in order to install liners in the tanks and because we were going to be laying out the timbers for documentation anyway, we had a wonderful opportunity to open the storage facility and allow the public in to see the ship. We offered guided tours of the ship April 14th, 15th, and 16th and almost 1,000 people booked a tour on one of those three days; that number doesn’t even include those who showed up without reservations.  

Ongoing Research

We know from historic maps that show Alexandria’s changing shoreline that the ship had to have been sunk and buried sometime between 1788 and 1798. In 1788 the location of the buried ship would have been underwater. Ten years later, by 1798, the property owner had filled in the shoreline with tons of earth so as to create more land. In this building out process, savvy waterfront landowners acquired older ships no longer seaworthy or worth the cost of repair and purposely sink or scuttle them so as to expedite the filling process. This means that our ship became part of the archaeological record sometime in that intervening decade.

Previously, we had identified a lease from 1798 between Elizabeth Copper, the owner of the lot on which the ship was found, and John Thomas Ricketts, an Alexandrian merchant. The lease specified that Ricketts was to “extend [land] into the River immediately in front of the premises.” However, after carefully reading the legal description of the 1798 agreement, it appears as if it includes and references the Strand as “…a space of Ground…left open as a passage by which to communicate with other parts of the Town and as a landing place…” This means that by 1798, the lot at 220 S. Union Street already had been filled in, and the scuttled ship must have been in the ground by the time John Thomas Ricketts signed the lease. Instead, Mr. Ricketts was agreeing to fill in land further to the east on the other side of The Strand. 

220 S Union May Update: Gazette 1799Even though this lead turned out to be a dead end, other leads remain. For example, an Act passed by the Alexandria Corporation in 1799 in order “to preserve the navigation of the Public Docks in the town of Alexandria ” may have a bearing on our buried ship. It begins: 

“Whereas…That diverse persons, inhabitants of the said town, and others, have been and still are in the habit of introducing into the public docks adjacent to the several wharves in said town, the decayed and rotten hulks of old vessels, boats, and craft, of different descriptions, under pretense of repairing the same, but in reality to serve the purposes of fuel, which when cut down to the surface of the water are willfully and negligently suffered to sink to the bottom of said docks where they remain obstructions to the navigation…” 

The 1799 Act then states: 

“…Be it enacted by the mayor and commonalty of the town of Alexandria, aforesaid, That if any person…shall bring…into any of the public docks…any hulks…of any vessel…and suffer the same to sink…and there remain any longer time than ten days, such offender shall upon conviction, forfeit and pay the sum of fifty dollars…and the further sum of five dollars for every twenty four hours…such nuisance and obstruction shall remain unremoved out of the said docks…”

At the turn of the 19th-century, this seems to have become enough of a problem that the City had to do something about it, going to far as to impose heavy fines for people who allowed their ships to sink from abuse and neglect at the docks. We have only half of the bottom of a ship, which appears to have been chopped down to the waterline with an axe, and then was allowed to sink on what used to be the City’s waterfront, and which dates to the years just before the City essentially said “Enough is enough! You all have to stop chopping your ships down to the waterline and then letting them sink to the bottom of the City’s waterfront!” Added together, a picture for how our ship was cut apart and came to rest at the bottom of the Potomac River along the Alexandria waterfront is coming together.     

Other lines of research we are currently pursuing include: 

  1. Analysis of the tree rings in the ship’s timbers (dendrochronology) which may reveal the source of the wood and the age of the trees used to build the ship.
  2. Initial study of the extensive worm damage to the ship’s sacrificial planking suggests that the worms are indigenous to the Caribbean region. Further analysis may help us to understand how far our vessel ventured during its lifetime.   
  3. Continued investigation of the artifacts found scattered among the ship timbers may help us continue to zero in on a date of use and the function of the ship
  4. Analysis of the many wooden fasteners or treenails (“trunnels”) that held the ship together can tell us about the lifespan of the vessel, how well it withstood the stress of many years of sea travel, and the amount of weight it carried and its distribution inside the ship. 
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