May 26th: One Trench Closed, One Trench Opened
While some students contended with the water-filled 101.T6, another group was busy finishing and “closing” the first trench begun, 100.T1. Closing a unit/trench can be called for either arbitrarily, or because you have no where else to dig/you’ve reached bedrock/sterile soil. In this case it was a mixture of both. In the NW 1/4 of 100.T1 there was a lot of sediment that could still be removed. However, we knew it was just fill material underlying the working surface above, and determining its “bottom” could be inferred from other areas of the trench. The long trough that could be a mortar box was continued down until it reached bedrock (or at least mine waste rock that had congealed into one mass due to the weight housed above it). this trough eventually bottomed out about 1 meter below where we first broke ground.
With the stopping of excavation called on 100.T1, the time came for its documentation. One plan drawing was made and profiles of the east and west profiles of the trench. North and south profiles of the deep trough were also made. The technique used to make these profile drawings is to have a line of string (that is level) running over the profile you wish to draw. From here, tape measures can be dropped down from the string (your datum line) at distance intervals of your choosing. In this case, we opted for every twenty cm across the string. At each interval, a series of measurements can be made from top to bottom (or bottom to top) of each element in the profile be it a soil change, iron bolt, or horizontal beam of wood.
Now that the trench unit is documented, we can leave it be until back-fill day and move on to opening new excavation areas.
We decided to open the very next trench area in the long line running north to south through the stamp mill/wash house. This trench was named 100.T2 (the 2 meaning that it was the 2nd in the line-not the 2nd excavated). We had an idea that the sloping boards found in 100.T1 continued throughout most of this unit, and therefore it would be rather shallow. We were mostly right.
We decided to skim the surface of this trench with shovels instead of trowels. Based on the findings of the previously opened trenches, we knew artifacts found here are most likely related to the later Warren’s Mill, and therefore artifact collection wasn’t a priority. Sure enough the sloped boards continued through the first 3 meters of the trench running north to south. Below that there was an open space of fill, followed by a large beam. We believed this beam marked the border between the stamp house and the wash house, and expected a major drop off after it down to the working surface discovered in the next trench down (101.T3). This turned out to be the case but we wouldn’t get to excavate and find out for another day. What we did find here changed our perception of the working process and provided one of the best tangible links between the past and present, stair case. More about that tomorrow.