Heritage Impact Assessment Calculator

The condition factor scales the entire raw risk score up or down based on how much intact archaeological material is actually left to lose, so a well-preserved site has significantly more at stake from a given development than one that's already been destroyed or heavily disturbed by past activity. This reflects that impact assessment cares about what could still be damaged, not just how significant or close a development is in the abstract.

Mitigation reduces the final risk score by an amount that scales with the site's condition, so a well-preserved, highly significant site sees a proportionally larger score reduction from avoidance or redesign than a site that's already in poor condition, where there's less impact to mitigate in the first place. Avoidance through redesign carries the largest reduction of the four mitigation levels, reflecting that not disturbing a site at all is the most protective option available.

A normalized risk score of 75 or higher triggers that top tier, which typically results from some combination of a highly significant site, a development sitting very close to or overlapping the site boundary, an intensive activity like deep excavation or demolition, and a site still in good physical condition with limited mitigation planned. Any one of these factors alone rarely pushes the score that high; it's usually the combination of several risk factors stacking together.

No — this produces a quick screening estimate meant to help flag projects that likely need closer attention, but an actual Section 106 review or equivalent state process requires a qualified archaeologist's field survey, consultation with the relevant historic preservation office and often tribal nations, and formal documentation that this simplified scoring model cannot substitute for. Treat a high score here as a signal to engage that professional process early, not as the final determination.