The Doan Valley Tunnel (DVT) system is one of seven tunnel systems in the Northeast Ohio Regional Sewer District’s (NEORSD) Project Clean Lake. The DVT system conveys both dry weather and wet weather flows to the existing downstream sewer system leading to the Easterly Wastewater Treatment Plant (WWTP) for treatment while also providing combined sewer overflow (CSO) storage in large storm events. With a storage volume of 18 million gallons (MG) (68 ML), the DVT system provides relief to the existing Doan Valley Interceptor (DVI) by controlling overflows at 11 permitted locations and reducing CSO volumes by 350 MG (189 ML) each year within the Doan Brook watershed area.
Major system components include: (1) DVT, 10,000 feet (3,048 m) of 18-foot-diameter (5.4 m)storage tunnel; (2) Woodhill Conveyance Tunnel (WCT), 6,300 feet (1,920 m) of 8.5‑foot-diameter (2.6 m) tunnel; and (3) MLK Conveyance Tunnel (MLKCT), 3,000 feet (914 m) of 8.5‑foot-diameter (2.6 m) tunnel.
Delve Underground led a joint venture to provide final design services for the DVT system, including 19,300 feet (5,883 m) of tunnel in rock, ranging from 8.5 to 18 feet (2.6 to 5.5 m) in diameter. Delve Underground also supported the owner during construction with submittal review, change order review, and on-site Resident Project Representative services. The project was completed ahead of schedule and $5 million under budget, and is now fully operational.
Innovations were incorporated into the design to achieve further cost savings. A shared mining shaft was designed for DVT and MLKCT to minimize disruptions and reduce costs. Further optimizations were undertaken along the alignments, including a variation to the DVT alignment to avoid a proposed new development and gain a more favorable railroad crossing. The WCT alignment was shifted to significantly improve hydraulic performance of the WCT under surge conditions.
A removable helicoidal drop shaft structure was designed to limit construction and service impacts within the densely populated University Circle medical and cultural hub area. The 6-foot-internal-diameter (1.8 m) helicoidal shaft allows for spiraling flows that reduce air entrainment, thus requiring a smaller footprint, as opposed to an equivalent 16-foot-diameter (4.9 m) baffle drop shaft that would otherwise have been required.
Newer geopolymer liner technology was used to structurally rehabilitate the aging Giddings Brook Culvert as opposed to excavating and replacing damaged portions of the culvert.