The discovery of long-buried crypts during a routine water main replacement in NYC’s Washington Square Park captured plenty of attention and headlines, but mysterious archaeological finds at construction sites are not as uncommon as you might think, especially in urban settings.

The secret crypts should serve as a reminder to developers and contractors that a review of archaeological records should be an important part of pre-construction due diligence, according to CBRE Valuation & Advisory Services group. Builders throughout the US are obligated to report archaeological finds if the project has triggered compliance with historic preservation laws, which would place a halt on the project until further preservation measures can be determined and completed.

A normal Phase 1 or Phase 2 Environmental Site Assessment does not usually include archaeological due diligence, but that does not exempt builders from being aware of preservation laws and complying. The State Historic Preservation Office maintains records on identified archaeological resources in each state and qualified environmental and cultural resource management consultants can be brought in for projects that require further review.