Pre-dig

Archaeology is both labor-intensive and irreversible—most work is done by hand and once an area is excavated it cannot be re-dug later on. An archaeological dig must be efficient and meaningful. So archaeologists take steps to make the most of every dig by planning ahead. The first step is to ask questions like: Where to dig? Why? Will digging here produce important information?

Before work begins on the ground, archaeologists like to know what they can expect to find. Other nearby sites can give a good idea about what kinds of people lived in that area, how long ago, and what kinds of settings they preferred (Near rivers? Near roads? On certain types of soil?). For sites that date to the period of written history (after the late 1500s in Virginia), archaeologists also look at old documents and maps. Other important sources include books and maps about soil characteristics and local geology.

Another vital step before digging is the “research design.” One dig cannot answer every question, so this design lists the most important questions. It also outlines the best ways to organize the work in the field (and later the laboratory) to answer those questions. Once all this preliminary work is done, the archaeologists are ready to load up their equipment and head into the field! back to top

Plan of site with grid marks along the left and top edges of the drawing.

Site Grid

One of the keys to successful archaeology is knowing exactly where everything was found on a site. To make this process efficient, archaeologists lay out a grid for mapping the entire site and smaller areas within the site. At the Prince Henry Street site, points on the grid were marked with nails driven into the ground at 10-meter intervals. A label attached to each nail has the coordinate for that point on the grid (distances east of (x axis) and north of (y axis) a point of origin (0,0). When drawing maps of different areas of the site, archaeologists can use the nearest grid nail as a reference point.

It is also important to consistently record the depths of soil layers, artifacts, and features. That information is important for understanding relationships between different parts of the site. Each site has one or more "datum" markers used as a reference for all other depths. Archaeologists use surveying equipment to measure depths relative to the datum. back to top

Archaeologists digging a grid pattern of shovel tests.

Shovel Tests

These small, initial pits are a common and effective way to assess what a project area has to offer and how best to proceed with larger-scale excavations. The typical shovel test is about the diameter of a dinner plate and generally no more than knee-deep. All soil from the test is sifted through quarter inch wire mesh to recover artifacts. The kinds of artifacts in each test is recorded, along with a description of the stratigraphy (layers of soil) exposed in the pit wall. Information about the contents of each shovel test can be entered into a computer mapping program that pinpoints areas with high concentrations of artifacts. “Hot spots” are shown with closely spaced contour lines, similar to the way a topographic map shows steep slopes. back to top

Uncovering a brick foundation in a test unit.

Test Units

In areas of the site where shovel tests show high concentrations of artifacts, archaeologists open larger square excavations (usually 1 to 2 meters on a side). With more room to maneuver, the soil can be carefully peeled away, keeping artifacts from different layers separate. In these larger units, contrasting patterns of soil become apparent, indicating “features”or manmade disturbances such as pits, postholes, trenches, even traces of a plow cutting into the subsoil. These excavations provide a representative sample of artifacts from different locations on the lot, and allow a better view of the soil deposits. back to top

Backhoe trench exposes undisturbed deposits beneath the overburden.

Using Heavy Equipment

Archaeologists sometimes use heavy machinery like backhoes. This kind of equipment is very helpful if used properly. The greatest advantage it offers is efficiency. In a given amount of time these machines can move much more soil than several people can with shovels.

Heavy equipment should almost never be used on an archaeological site as a first step. We brought a backhoe out to the Prince Henry site at City Point only after intensive testing by hand. The initial tests told us where it was reasonable to use the machine and how much soil to remove.

The backhoe operator was directed to strip away only the upper foot or so of soil. This upper layer had been churned up over the years by garden plowing and other modern activity. Moreover, we had already obtained a sample of artifacts from the "plowzone". The machine was not allowed to dig into deeper strata which remain undisturbed. The benefits of machine stripping were seen almost immediately. It was with the backhoe that the large Civil War Feature 8 was exposed. back to top