This is part of a series on CRM archaeology. For general information about CRM see CRM Archaeology: Cultural Resource Management. For more information about Phase I testing see: CRM Archaeology: Phase I Testing (Part 1).
One of the common methods for phase I surveys are shovel test pits (or STPs). At the company that I currently work for we will split into two person teams on days when we are digging STPs. One person will dig the STP while the other screens the dirt. We usually trade tasks for each hole so that we don’t get bored and have equal opportunity to dig (every archaeologists favorite task).
STPs are laid out over the area of study in a systematic manner. Generally, they are spaced 15 meters apart or less along the north-south or east-west axis. The entire area that needs to be surveyed will be covered by these transects, though some STPs along the edges of the property or in areas where the land is covered in water or otherwise impossible to excavate will be ‘written off’.
STPs are either circular or square and range in size from 30 to 50 cm in diameter depending on the requirements of the company you work for. We dig using shovels, and excavation is not as meticulous as with other forms of excavation. The focus is on discovering the stratigraphy of the area and whether there are likely archaeological sites on the property. STPs are dug until the subsoil is found, and then continues 10-20 centimeters into the subsoil (again depending on the requirements of the company). Generally STPs end up being 30 to 50 cm in depth, though they some are obviously significantly deeper. Usually we will only dig an STP to a depth of 1 meter, though requirements also vary here.
We remove the “sod cap” (the very uppermost soil with grass and vegetation) from the STP before beginning excavation, and replace it when the STP is completed. If the STPs are being dug on a manicured lawn (like in a park or in front of a museum) we will use a tamper to make sure that the sod cap is as flush with the surrounding ground as possible.
If significant archaeological artifacts are found (i.e. flakes or points) radials will be dug. This means that STPs will be dug in all the cardinal directions around the positive STP. These are generally spaced 5 meters apart. Radial STPs will be dug until there are two negative (without significant artifacts) STPs in a row.
It generally takes 10-20 minutes for a professional archaeologists to dig an STP depending on the conditions of the soil. If the STP has a lot of roots, gravel, or thick clay the time required is usually on the upper end of the spectrum. The conditions for digging STPs are usually not as comfortable as field walking where you are working in a plowed field. Often we will be trudging through tall grass, or cutting through dense brush.