Old Pipe/Renewed Pipe - How New Technology Enhances the Rehabilitation of a One Hundred and Forty Year Old Sewer

The Boston Water and Sewer Commission (Commission) owns and operates sanitary, drainage, and combined sewer systems in the city of Boston, one of which is the Dorchester Brook Sewer system. The Dorchester Brook Sewer serves a tributary area in North Dorchester and Lower Roxbury of almost 1,000 acres. It is over 100 years old, and is comprised of a 108” × 156” brick arch-shaped structure supported on wooden piles driven through thick layers of organic soils. The damage to an 840-ft section of this sewer includes longitudinal cracking in the crown of the pipe with as much as 2-3 courses of missing and/or delaminated brick layers.Spiral-wound technology has the primary advantage over the more traditional Shotcrete method in that it provides a maximum cross-sectional area for flow while also providing the needed structural integrity, and it was chosen for the rehabilitation solution.The sewer was first cleaned using bobcat-style narrow-width loaders, and then a manned-entry video inspection was performed, followed by a laser survey that detailed the actual cross-section shape of the host pipe. A middle section of the reach of sewer was found to be in particularly degraded condition, with the crown missing 3 courses of bricks and delamination and cracking present. Worker safety concerns led to an additional requirement for special shoring the inside of the pipe in this section before continuing work. Additionally, a dual-liner profile system was employed to accommodate the difference in each section of conduit based on the relative deformed conditions