My boyfriend is involved in archaeological work on land, so I’ll weigh in with what I’ve learned from him (errors mine):
Serendipity has a lot to do with finding many archaeological sites, just as with fossil sites (e.g., dinosaurs). Archaeology is an excellent example of a discipline in which amateurs can make an important contribution by reporting their finds. In the case of historic sites, there may actually be documentation to help guide the excavation (but such documentation is not always very reliable). As beakerxf pointed out, excavations are expensive affairs, so a dig undertaken for academic research purposes is almost certainly going to focus on potentially high-profile finds rather than, say, an everyday Roman kitchen. IMHO, I don’t think any academic archaeologist would want to waste precious resources ($$$) digging in sites that may or may not have much significance, or just digging along a likely riverbank if there’s no other evidence in sight.
[Side note: I understand that much of the excavation undertaken in Italy and Isreal these days is salvage archaeology, where the excavators might be just one step ahead of the builders. There’s also a lot of material left in the ground or discarded, especially in Italy; how many marble statues can you save & put in a museum?]
The world of professional archaeology is a bit different. In the U.S., there are regulations regarding what level of effort is required to look for archaeologically significant sites before new construction begins (a practice known as cultural resource management, or CRM for short). Any construction work to be conducted by a federal agency (e.g., the Army Corps of Engineers) or on federal property (e.g., national parks) requires an archaeological investigation before work begins. Individual states also have their own requirements; private developers often don’t need to do anything at all, but state agencies and public utilities are obliged to investigate. Contract archaeology firms, or sometimes archaeological divisions of large engineering companies, undertake all the excavating work for the client (property owner or building contractor); the excavations are supervised by archaeologists (principal investigators, or PIs) who usually have a certain minimum level of professional experience.
Investigations proceed in three phases:
[ul]
[li]Phase I: The area to be impacted by construction is walked over by the client, the principal investigator and often the site geomorphologist (person who studies landforms). Areas that will be impacted most are identified. A literature search is also done to see if finds have previously been reported from the area. In the event that no known sites exist in that area, then several “shovel test pits” are excavated in those spots that the PI and/or the geomorphologist feel may have been likely locations for activity, or else they may simply dig a number of test pits in a pattern that will sample the area effectively. Once the shovel test pits are dug (by steam shovel), the geomorphologist examines the soil stratigraphy in order to build a predictive model for sediment accumulation at the site, and the excavated material is screened for artifacts.[/li]
The number and/or type of artifacts recovered will help determine whether the investigation moves ahead to the next phase. (I don’t recall whether there’s a specific minimum number, but I think the rule of thumb is on the order of a few dozen artifacts.) If few or no pieces are found, the investigation ends. If it continues, the predictive model constructed by the geomorphologist helps to narrow the area that should be investigated further.
[li]Phase II: One meter by one meter squares are dug one layer at a time, with sediment screened. Artifacts found in situ are plotted with respect to the levels and locations at which they are found inside the square.[/li]
Again, if relatively few artifacts are found, or if the site is discovered to be profoundly disturbed, the investigation can end at this point. However, if many and/or highly signficant items are found, the investigation moves to
[li]Phase III: This phase may include widespread excavation, with large pits (1 x 3 meters or 3 x 3 meters) wherever the PI deems necessary.[/li][/ul]
Reports have to be written by the PI’s firm at the end of each phase, and all artifacts recovered have to be washed and catalogued (and often stored). In sites that turn out to be rich in artifacts, other studies may also be done to help place the artifacts in a temporal context, e.g., radiocarbon dating, pollen analysis, sediment analysis. Other specialists may also be called in to lend their expertise for the final interpretation of the site. These days, the PI’s firm will also generate public outreach materials (pamphlets, videos) related to the dig.
If the PI hits the mother lode of artifacts during a Phase I investigation, a Phase III may be triggered immediately.
As you can imagine, going through all phases can be an expensive affair for the client. A full-blown excavation through all three phases may take more than a year to complete and cost a minimum of several hundred thousand dollars. As a result, Phase III excavations are seldom financed by anyone other than a federal or state agency or public utility. Others clients will try to practice avoidance (i.e., they adjust their plans to find a less sensitive area), or they may simply give up. Unfortunately, some clients are able to find skeevy contract archaeologists who will manage not to “see” anything in the course of the Phase I, and so write off the entire site.
