An archaeological evaluation is almost always carried out with trial trenching. Trenches or test pits are dug systematically in areas where archaeological remains are expected. A trial trench survey should be a representative sampling of about 5-10% of the project area.
The goal of an archaeological evaluation is to determine the size of the archaeological site, as well as its nature, intactness and preservation. By means of an evaluation protocol it is ascertained whether the site is retention worthy. This report contains a selection advice that will be used by the proper authorities to take a selection decision. Prior to the evaluation, a design brief needs to be drafted.
If an archaeological site is deemed worthy to retain, it may be decided to change the construction plans. This will allow for retention of the archaeological site without having to excavate it (in situ preservation). If changing the building plans is impossible, the site can be excavated (ex situ preservation).