Trenchless Technology Comparisons
Publication: Northeast Journal of Trenchless Technology Practices
By Emily Church, PE, & Daniel Roop, PE, Tighe & Bond
Introduction
The Town of Ipswich is a coastal community in Massachusetts approximately 30 miles north of Boston with approximately 13,800 residents. The Ipswich Utilities Department maintains the water system that consists of over 93 miles of pipe ranging from 6 to 12 inches, 4,700 services, three pump stations, three water tanks, 680 hydrants, and 1,100 gate valves.
The Mill Road Ipswich River water main crossing is located at the Ipswich, MA and Hamilton, MA town line. The 10-inch diameter cast iron main was installed in 1969, running along Mill Road then dropping nearly 20 feet off-road for an approximately 230-foot run beneath the Ipswich River parallel to the historic Warner Bridge. In 2017, a segment of approximately 12 feet of pipe beneath the River experienced longitudinal fractures. Gate valves on either side of the River were closed to isolate the pipe, and emergency work was performed to replace the compromised section with a new 10-inch ductile iron pipe using an open-cut method.
Unfortunately, the pressure testing of the repaired pipe failed. Despite Contractor and Town efforts at the time, the cause of the pressure test failure beneath the river could not be identified and corrected at the time, and the water main remained offline for approximately 2-years afterward. The main’s shutdown did not affect water transmission to other areas of Ipswich as flow could be redirected through the system. However, the Town desired to restore service to the main running beneath the River to improve system reliability and redundancy.
From project onset, Tighe & Bond and the Town agreed that implementation of a rehabilitation technology that would preclude the need for extensive permitting and in-river geotechnical investigations was important, if practical, to minimize schedule and reduce permitting service fees. For comparison, a recently completed sewer siphon replacement project in Town crossing beneath the Ipswich River required a 2-phase open-cut approach that took nearly 2 years to permit and thousands of dollars in permitting support fees. The team knew significant time, and cost savings could be realized if a trenchless approach were feasible.
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