Lower Olentangy Tunnel Project, Columbus, Ohio
The Lower Olentangy Tunnel is a major extension of Columbus’ OARS Tunnel system, designed to improve sewer capacity and protect the Olentangy River. DLZ led the design team for this 3.5-mile tunnel from Neil Avenue and Vine Street to north of the OSU campus, evaluating six alignments and numerous variations to select the safest and most efficient route.
Project Highlights:
- Tunnel & Shafts: 17,300 LF of 12-ft diameter tunnel connecting to the OARS system in the Arena District, with three main shafts at Tuttle Park, Gowdy Field, and Vine Street.
- Additional Structures: A 90-inch curved microtunnel at 2nd Avenue ties into LOT at Gowdy Field.
- System Improvements: Relief structures eliminate the 2nd Avenue pump station and prevent sewer overflows, protecting parks, basements, and the river during wet weather.
DLZ’s Role:
As prime consultant, DLZ managed over 30 subconsultants and led:
- Hydraulic and surge modeling (citywide and HAST2)
- CFD analysis of outlet gates
- Shaft and civil design, structural design, odor control upgrades, and tunnel ventilation
- Risk management workshops and value engineering sessions
- Geotechnical investigations using amphibious rigs and hydrogeological evaluations
- Environmental assessments and coordination with ODOT, OSU, OEPA, ODNR, and USACE
Design Challenges & Innovations:
- Mining under highways and Olentangy River Road with strict settlement controls
- Figure-eight shaft design at Gowdy Field for dual TBM launches
- Vibration mitigation near OSU’s Stefanie Spielman Comprehensive Breast Center
- Floodplain restoration at Tuttle Park with porous paver parking
- Temporary river causeway for ground improvement at mixed-face conditions
- Integrated surge, ventilation, and odor control systems with OARS Tunnel
The LOT project delivers critical infrastructure to reduce sewer overflows, improve water quality, and protect community assets through advanced engineering and collaboration.
