The East Boston Branch Sewer Relief project is a $85.4-million project that was completed in 2010 by the Massachusetts Water Resources Authority (MWRA). This project is part of the federally mandated cleanup of Boston Harbor. The sewer system in East Boston was built 110 years ago. It is in an area of reclaimed waterfront and the goal of this project was to control combined sewer overflows entering the harbor.
To reach the goal of controlling combined sewer overflows entering the harbor, the MWRA planned to upgrade to 4.5 mi of the aging interceptor system serving East Boston and to employ a combination of cured-in-place pipe (CIPP) lining, microtunneling, pipe bursting, and open-cut excavation methods. The project included three different construction contracts:
- The rehabilitation of approximately 1 mi of existing egg-shaped brick sewer by the addition of a CIPP lining
- The installation of approximately 2. 5 mi of 24 to 66 in. diameter pipes by a combination of micro-tunneling, in-line microtunneling, and traditional cut-and-cover excavation
- The expansion of approximately 1 mi of vitrified clay pipes 12 and 15 in. diameter to high-density polyethylene pipe 16 and 20 in. diameter by pipe bursting, with some reaches installed by means of cut-and-cover excavation
Numerous pipes installation methods were proposed during design, and microtunneling was selected. This method would affect the surface less and utility relocations would be required only at each shaft location. 17 microtunneling runs were completed for a total of more than 12,000 ft.
A quick timeline for the project is as follows:
- 2001 : the design process began
- 2004 : the CIPP construction contract completed
- 2008 : remaining construction work began (microtunneling and pipe bursting)
- 2010 : court-ordered completion date
For locations in which seawalls and abandoned foundations were likely to be encountered, pipeline was installed by open-cut excavation.
For areas in which the existing pipes were made of material that could be broken apart, the installation method selected was pipe bursting.
This project was a challenge for project participants because of the court-ordered deadline for completion, the major design, and the densely populated and heavily urban area where the project took place. East Boston is comprised of busy streets, a complex system of overhead and subsurface utilities, a unique geological history, and a mixture of commercial properties and residential houses. Coordination and communication with residents of the area and the community (noise control, traffic management, preconstruction and postconstruction surveys) proved challenging. The MWRA was able to complete its critical East Boston Branch Sewer Relief project on time and they greatly reached their goal by increasing the system’s storage capacity and facilitating the delivery of wet-weather flows. They reduced the volume of combined sewer overflows entering Chelsea Creek and the inner part of Boston Harbor by 79 % as well.
Figure 1 – East Boston Branch Sewer Layout
If you have any questions about sewers or combined sewer overflows, please contact John McAllister at email@example.com or at (508) 747 - 7900 x 117.
Information in this article taken from August 2011, article by Phillip Lanergan, Peter Mcgovern, Paul Savard, P .E., David McKiernan, and Lisa Hamilton, P.E., M.ASCE, published in Civil Engineering News.