CRM Phase II: Test Units

If it is determined that the land surveyed during CRM Phase I may be of some cultural significance, Phase II testing may be conducted. The purpose of Phase II is to establish the extent of buried culturally significant features. It is also determined whether the site is eligible for the National Register of Historic Places (NRHP) during this phase. The NRHP is a list of sites, objects, structures, and buildings that are deemed to be worthy of preservation.

The most common type of phase II testing are test units, though STPS, trenches, etc. may also be used. Test units help to establish stratigraphy for the site as well as providing further information about whether the land has areas of cultural significance. Test units are placed strategically around the area being surveyed, taking into account any artifact concentrations found during Phase I, topography, cultural features, etc. The amount of test units that are dug during Phase II varies, but generally at least two test units are dug. These are usually 1X1 meter excavations that are dug until 10-20 centimeters of sterile soil has been reached. Sterile soil means that no cultural materials have been found. Usually we dig in 10 cm arbitrary levels, meaning that we will only dig 10 centimeters at a time. If we find a natural soil color or texture change however, we will switch to digging “natural layers”. That is, we will stop digging when we hit a new soil color or texture. If we find any cultural features, like hearths, pits, postmolds, etc. we will stop to take photos and map the feature. Any features found are normally bisected so that a profile can be drawn. Features are excavated before the rest of the unit can be dug. Test units are typically square, and we lay out the units using measuring tapes, nails and string, to ensure that the unit is the appropriate size. Walls are kept as straight as possible, so that when the unit is completed we can draw a profile map. As with STP’s all soil is screened, typically through 1/4″ screens.

At the current company I work for, we usually dig test units in 3-4 person teams. Each person will dig one level, so that we can trade off before anyone gets too physically exhausted. Depending on the depth of the unit, it will take about half a day to a day to complete.

A profile map is drawn on graph paper in the field, and allow us to denote the stratigraphy of the unit. If any cultural artifacts or large rocks are present in the wall, these are also normally drawn in. In order to make the profile map as accurate as possible, a measuring tape is laid across the top of the unit, so that we can take points along the line of each color change. This way, we can create a representation of the wall on graph paper. Profile maps also include all of the colors and textures of the soil present in the unit. Pictures are also taken of the profile, and of the floor of the excavated unit.

After the profile map has been drawn and all the paperwork is in order, we get to back fill the unit. This means that we put all of the excavated soil back into the unit which depending on its depth and the condition of the soil can be a backbreaking task.



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