Pushing through Adversity: Sliplining Challenges and Solutions in Large-Diameter Sewer Rehabilitation in Boston, Massachusetts

Rehabilitating aging infrastructure is becoming more urgent in urban cities, making trenchless rehabilitation methods a top priority in our industry. The Boston Water and Sewer Commission (BWSC) is undertaking a multi-year, multi-phase program to rehabilitate one of its most critical sewer interceptors. The New Boston Main Interceptor (NBMI) was installed in 1980 and conveys sewage and stormwater from more than 3,000 tributary acres, including downtown and multiple other neighborhoods. The 102-in. reinforced concrete pipe has experienced significant corrosion by hydrogen sulfide gas. The rehabilitation of the NBMI is being carried out using trenchless techniques due to its depth along a busy residential/commercial street and its crossing of several active railroad tracks and a subway line. Phases I and II rehabilitation will be complete by early 2025, and Phase III design is underway. This paper focuses on the sliplining approach utilized in Phases I and II for a total of approximately 2,600 linear feet. While this strategy minimized excavation and disruption, many challenges included sliplining in live flow, jacking from an existing structure, managing both planned and unanticipated deflections with a tight annular space, and completing the in-pipe termination between Phases I and II. Successful utility rehabilitation projects are those unseen by the surrounding communities, but that does not mean everything underground proceeds smoothly! In this paper, we shed light on specific challenges faced in sliplining the NBMI and share strategies that can prove beneficial to owners and engineers facing large-diameter sliplining worldwide.