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Archaeology Update — The Long Barrack’s Foundation Has Been Located

Kristi Nichols, Director of Archaeology, Collections and Historical Research
August 9, 2019

The archaeological project associated with the preservation of the historic structures continues to work on the three units associated with the Long Barrack. The unit located in the Cavalry Courtyard (Excavation Unit 18), against the east wall of the Long Barrack located the bottom of the foundation at approximately 1.3 meters below the surface.

The information concerning the depth of the foundation is being shared with the historic architects, and they will now begin their documentation of the wall. The other two units have not encountered the base of the foundation yet but have been excavated to approximately 1.1 meters below the surface.

Excavation Unit 9, located inside the southwest corner of the Long Barrack, worked on excavation of a feature that had appeared in the upper elevations. The feature revealed up to seven floor levels composed of compacted soils mixed with varying amounts of lime.

Hand holding what appears to be a corroded iron key artifact
Figure 1. Skeleton key recovered from feature matrix in Unit 9.

Each floor level was individually excavated and screened to determine the composition and document the artifacts solely related to the level. One of the floor levels produced a ferrous skeleton key. The artifact has not been attributed to a certain time period yet but will be examined in the context of the other materials recovered. As the excavations of the floors progressed, the unit revealed a complex profile.

In addition to the many floor layers, the profile revealed a stark contrast between the center of the Long Barrack and the space up against the foundation. A builder’s trench was revealed extending approximately 50 cm from the foundations. A builder’s trench is an area excavated alongside of a foundation to allow for access for repairs or related to the trench dug when a foundation is being constructed.

The builder’s trench base is located approximately 70 cm below surface, indicating that it was not excavated as part of the initial construction. Once the floor features were excavated, the archaeologist created precise profile drawings of the stratigraphy and laser scanned the unit.

Layers of foundation inside an excavation unit
Figure 2. Photograph of the profile of the north wall of Unit 9. Note floor layers on right and builder’s trench on left.
Archaeologist standing inside an excavation unit, taking measurements
Figure 3. Archaeologist taking elevation measurements from a datum string-line.

The Excavation Unit 17 located on the east side of the arcade of the Long Barrack further examined the rock alignment that the archaeologists had earlier uncovered. As previously identified, the rock alignment consists of two different construction materials: cut limestone on the northern portion and stacked rough limestone to the south. Both sections of the alignment are approximately 30 to 40 cm in thickness and is sitting atop a brown soil.

As the archaeologists continued to excavate the soils to the west of the alignment, additional features were uncovered. Beneath the currently standing base of the arch, a foundation of a different construction was noted. The foundation of the modern arch extends approximately 50 cm below the surface, at which a noticeable change in construction method and materials. Portland Cement, commonly used during the late 19th and early 20th century improvements on the site, was observed holding the stones together above this line.

Below, the foundation becomes narrower and the stones are held together with a mortar that is similar to that used during the Spanish Colonial period. In addition to the change in material, the foundation extends east into the unit.

At approximately 110 cm below surface, the archaeologists have uncovered a surface between the arcade foundation and the rock alignment. The surface actually appears to extend underneath the alignment.

The surface has been left in place, with a small pocket that did not appear to have the lime surface excavated approximately another 10 cm before encountered a few large limestones that prevented further excavations. When compared to Excavation Unit 9, it appears that both floor surfaces are at similar elevations and constructed of similar materials.

When viewing the profiles of the walls of the excavation units, evidence consisting of a change in soil color reveal a possible builder’s trench. In this case, it appears the builder’s trench may be related to the reconstruction of the arcade as it only extends to the approximate depth of the evidence of Portland Cement on the foundation.

Archaeologist seated inside an excavation unit writing down measurements
Figure 4. Foundation of the arcade arch. Archaeologist creating a precise, measured drawing of the unit walls.
Archaeologist inside an excavation unit mapping stones in the foundation
Figure 5. Archaeologists mapping the stones of the foundation.

Due to the presence of feature that cover the entire area of the unit, Excavation Unit 17 is being looked at to determine how to proceed forward. In the meantime, the archaeologists are mapping the stratigraphy in the profiles. In addition, the unit features are being recorded through use of a laser scanner.

Excavation Unit 18, located in the southwest corner of the Cavalry Courtyard, reached the bottom of the foundation at approximately 130 cm below surface. Much of the upper portion of the foundation exhibits Portland Cement, indicating that it is part of the early 20th century reconstruction. There appears to be a different material holding the foundation stones together. The historic architects plan to sample the different mortar materials for analysis to determine composition.

Since the excavations in Unit 18 uncovered the bottom of the foundation, archaeologists finished the week by creating precise maps of the walls of the unit (all four). Although the unit was also laser scanned, the precise drawings add another layer of data that can be referenced when analyzing the soil stratigraphy and construction of the foundations.

Archaeologists plan to open additional units during the week of August 12: one in the northern portion of the Long Barrack, with the matching unit opened as soon as traffic permits from the City are obtained; and a pair inside the Church.