The Waterford Mill must have been an impressive sight when it was first built in the 1870s with its stone dam and the Millpond dike slowing the mighty Cannon to produce some of the finest flour in the United States, a strong source of regional pride. Along with our excavation and documentary research, we undertook an energetics assessment of the dike, which involved determining its volume and thus the amount of labor required to construct it. The Millpond Dike is a significant earthen mound and would have required a large amount of labor to build it. During the excavation of the dike we found no evidence of a stone core, and thus assumed for the energetics assessment that the entire dike is made of soil. We also assumed that this soil came from the surrounding area and thus did not factor the energy required for transportation of the soil into our calculations.

To determine the volume of the dike, we used Light Detection and Ranging (LiDAR) data to identify the difference in elevation between the dike and the surrounding area. LiDAR is a technology that determines differences in distance by measuring the time difference between laser pulses being emitted, reflected, and received. A plane with a LiDAR camera mounted on it collected data in the Arboretum, which was compiled and used to produce an image of the difference of elevation in the landscape (Figure 1). The LiDAR data show that the dike is 350 meters long, 2.21 meters tall, 11 meters wide on the base, and 3 meters wide on the top. We used the “calculate volume” tool in ArcGIS software to calculate the volume of the dike as 5475 cubic meters. For reference, a typical 53-foot-long semi-trailer has a volume of about 99 cubic meters. Thus, the total volume of the Millpond Dike is equivalent to about 55 semi-trailers.

Next, we determined how much dirt a single person could move in an hour by researching relevant literature. One article stated that a person could move 0.29 cubic meters per hour (Hammerstedt 2005) and another put the number at 0.52 cubic meters (Erasmus 1965). The former study involved university students inexperienced with hard labor who excavated using replicas of prehistoric Mississippian tools. The latter study involved Mexican laborers accustomed to difficult work excavating with digging sticks. We determined a third rate of 0.31 cubic meters per hour based on Noah’s landscaping experience. We decided to use this last figure because of its position between the two rates found in the articles. The workers who built the dike were likely more experienced with excavating earth than the average university student and probably used metal shovels. However, even if the actual rate was quicker than our choice of a relatively slow one, we did not take into account the energy required for transportation or compaction of dirt, which would have added time to the project.

Using the volume and rate of excavation, we calculated the amount of person-hours involved in constructing the dike to be 17,661. We assumed a work day of eight hours, and thus the number of person-days for construction was 2208. This means that it would’ve taken one person nearly 18,000 hours, or about 2200 days, to construct the dike. Obviously the dike was not built by a solitary worker and the time taken to construct it would have depended on the size of the workforce (Table 1).

Size of workforce (people)	15	25	50	75	100
Construction duration (days)	147	88	44	29	22