Rehabilitation of the 105-Year-Old Lakewood Interceptor Tunnel with Glass Reinforced Plastic Composite Pipe

The Lakewood Interceptor Tunnel in Lakewood, Ohio (pop. >50,000), was originally constructed from 1918 to 1945 by tunnelling methods largely through rock strata at depths varying from 20 ft to 94 ft. It carries over 77% of the wastewater flow for the city of Lakewood (city) and is over 20,000 ft long. The egg-shaped pipe is 56.5-in. high by 42.5-in. wide and was predominately constructed with clay tile segmental block pipe with localized areas constructed with conventional brick. It is being rehabilitated using segmental Glass Reinforced Plastic (GRP) composite pipe sliplined with a fully grouted annulus. The structural design of the liner utilized the ASCE MOP 145 (2021)—Design of Close-Fit Liners for The Rehabilitation of Gravity Pipe. In 2021, the city noticed an increase in the frequency of localized collapses of the tunnel roof. This initiated a condition assessment (CA) program of the entire interceptor to evaluate options to rehabilitate the tunnel to eliminate further collapses and provide the entire interceptor with a new design life. The CA program utilized a multi-sensor platform equipped with high-definition CCTV, time-of-flight LIDAR profiling above the flowline, and SONAR profiling below the flowline to quantify condition both visually and dimensionally. The inspections revealed severe mortar loss in brick sections, movement and instability of the sewer walls, and localized loss of the crown of the tunnel in many areas. The rock strata prevented migration of the collapse to the surface, but overall, the assessment indicated that large sections of the tunnel were in a state of incipient failure that warranted widespread structural rehabilitation. The depth of the tunnel, its proximity to residences and apartment complexes, and the large flow volume created many challenges for rehabilitation. Based on a review of a wide array of rehabilitation techniques, the use of segmental GRP composites was selected due to its ability to be matched to a wide array of subtle cross section changes, overall constructability given the unique site conditions, ability to be installed without bypassing sewer flows, and life cycle cost considerations. Type testing criteria were developed to facilitate design of the lining based on 100-year life objectives and the construction phase includes a verification process to confirm that all core design objectives can be confirmed as being met in the construction phase. The project was bid in January 2023 and awarded for $25.4 million. This paper provides a detailed overview of the assessment and design process and an update on construction progress and challenges.