Adverse effects include:
- Physical destruction
- Damage or alteration of the character of the setting when that character contributes to the site’s qualification for the NRHP
- Introduction of elements that are out of character with the property or affect its setting
- Neglect that results in deterioration or destruction
- Transfer, lease or sale of the property
If a property is threatened with adverse effect, mitigation will be required. The goal of mitigation is to eliminate the threat of adverse effect. Avoidance is always the preferable alternative, but not always possible.
Examples of alternative solutions for archaeological sites include:
- Site burial
- HABS/HAER documentation
- Establishment of green spaces
- Replication and/or virtual visualization
Videography offers another potential avenue for stand-alone mitigation and/or as one aspect of data recovery. A documentary of archaeological investigations set against a background of data derived from historic research could be an exciting way to preserve a site.
Replication and/or virtual visualization are two mitigative alternatives PTA has been recommending. If a site hosts above-ground features that can be modeled, such as a military test range complex, mitigative methods may include gathering background data, creating detailed and measured drawings, geo-referenced photographs, map plotting, and comprehensive description. These data can then be used to build a model replica of the range for display. A single model or large diorama could fulfill mitigation of adverse effect and objectives of education programs and public outreach.
Virtual models have great promise as mitigative alternatives. The past can literally be brought to life by virtual visualization, with 3-dimensional displays reconstructing features such as a Mississippian mound and village site. Displays may be housed in various ways, such as a kiosk programmed with interactive capabilities. Special glasses and sophisticated projection technology allow the public to experience what life was like in the prehistoric and historic places traditionally preserved only in photographs, drawings, eye witness accounts, and technical/popular reports.