Excavation of the Millpond Dike

The class excavated a one square meter trench on the east side of the Millpond Dike on Tuesday and Wednesday labs for three consecutive weeks. We hypothesized that the rock quarried from the nearby site was used in the construction of the dike, likely as a stone or gravel core and began an excavation trench in the dike to test this. Starting on 4 May, we first identified a good location with few roots and fallen trees and then marked out a one meter by one meter area with flags and twine about two meters from the center of the top of the dike. We chose a spot on the east side of the dike because the west side might have had foreign debris that had been washed into the dike by flood waters.

We shovel-shaved and used trowels when needed in our excavation, initially using trowels more frequently to better establish soil changes and start a new context. An archaeological context refers to the spatial position and surrounding material of an artifact as well as the connections to other artifacts that these factors imply. However, we adapted our methods because our purpose was to get to the bottom of the trench and because we found just one artifact in excavating about 35 centimeters down. Thus, carefully establishing each context was less significant and we focused more on excavating larger volumes of dirt and sifting efficiently. Instead of looking for changes in soil composition to establish new contexts, we created a new one about every 15 centimeters. This allowed us to work more quickly but also have a good idea of where an artifact came from if we found one. Context one was composed mostly of sandy, brown soil, while context two was sandy, light brown or orange soil. Context three, was very dense, rich, dark brown soil, which extended downwards all the way to the bottom of the trench, nearly eight feet down (Figure 1). Since our trench was on the side of the dike and thus sloped downward, we leveled the east side outside the boundaries of the trench so we could stand on it to excavate.

Figure 1. An artistic rendering of the excavation trench on the east slope of the Millpond Dike. Context one is represented by the lighter brown soil, context two by the short layer and small pockets of tan or orange soil, and context three by the rich, dark brown soil extending to the bottom of the trench.

At the end of the first lab period we excavated, retired Carleton geology professor Mary Savina stopped by the excavation site and identified three different soil textures in the west side of the trench. She hypothesized that the difference in soil composition was because each layer was laid at a different time. As we continued to excavate, we revealed an interesting stratigraphy on the sides of the trench (Figure 2). The dark soil of context three that dominated most of the trench never reached the surface and was always covered by the lighter loam of context one as it sloped downwards. The brief tan, sandy layer of context two additionally never reached the surface and looks as though it rounded out the mound made by the dark brown soil. We were unable to determine when or why different soils were used or added to the dike but hypothesized that portions of it were reconstructed or reinforced after water erosion or damage by floods. In the end, we did not find any evidence of a stone core in the Millpond Dike and were thus unable to establish a direct connection between the quarry site and the construction of the dike.

  • Beginning of context 6 (~100 cm depth)
  • End of context 6 (~117 cm depth)
  • End of context 11 (~234 cm depth)
Figure 2. The south side (top row) and west side of the dike trench at various stages of excavation. The dense, dark brown soil continues still deeper but does not appear on the surface. Vertically aligned photos were taken together and thus represent the same context.

Artifacts

We found only two artifacts in the Millpond Dike. The first was a staple found in context one on 4 May (Figure 3). Due to the condition of the staple and the fact that it was found alone in context one, we couldn’t find any more information about what type of staple it was or from where it came. We hypothesized that the staple could have been used in a sand bag because the soil in context one is more sandy than the lower contexts and the staple is quite large.

The second find was a bullet casing found in context four (Figure 4). The bullet casing had an inscription on the back that read “REM-UMC 25-20,” indicating that the bullet was manufactured by Remington Firearms after it had merged with Union Metallic Cartridge Company (UMC) in 1912 (Remington 1912). This poses a problem for dating the trench. Context four is about 90 centimeters down, which theoretically means that objects found in it would have come from the time of construction and because the bullet comes from after 1912 the relative dating puts the construction of the trench after 1912 as well. This dating conflicts with the documentary record, which dates the construction of the dike to 1873. It is possible that the bullet was found close to the edge of the trench which could explain the later date. Floods after the construction of the dike are known to have washed out the dam and may have partially destroyed the dike as well. The bullet casing could’ve been deposited during reconstruction of the dike as well.

  • Figure 3. The staple found in context 1 of the Millpond Dike trench, possibly from a sand bag.
  • Figure 4. The bullet casing found in context 4 of the Millpond Dike trench with an earliest possible date of 1912.

References

Remington Arms-Union Metallic Cartridge Co. A New Chapter in an Old Story: Being an Interesting Account of the Strange Steps by Which a Great Modern Business Has Grown out of Ancient Conditions: Together with a Look into the Future. The Company, 1912.