Urban Archaeology Investigation – DigIndy Deep Tunnel Project

Underground utilities assisting the cultural resources team

By pioneering an innovative technique in urban archaeology, Cardno is helping to identify archaeological sites and determine their National Register of Historic Places eligibility prior to construction on the DigIndy Deep Tunnel Project – a near-impossible feat using traditional reconnaissance techniques for deeply buried urban historic sites.

The project consists of 18.7 miles of tunnel, which is being mined through bedrock 200-250 feet beneath downtown Indianapolis, in an effort to reduce combined sewer overflow throughout the City. 

Working on behalf of Citizens Energy Group, Cardno is completing archaeological and architectural history investigations, reporting, and agency consultation. Our processes include standard archival research coupled with ground-penetrating radar investigations to identify potential historic archaeological features at any given project area.  

This research and analysis is then followed by controlled excavation with vacuum trucks to locate and excavate features more accurately than traditional Phase I methodology. In addition, this technique has the potential to determine National Register of Historic Places eligibility without the need for a traditional Phase II evaluation, and to minimize accidental discoveries after project construction has begun.  

Cardno has tested this technique at 11 separate locations on the DigIndy Deep Tunnel Project thus far, and has been successful each time in identifying historic sites and features. Some of these cultural resources are buried as much as one meter (three feet) below rubble and modern debris, making their detection and identification nearly impossible through traditional Phase I reconnaissance techniques.