Cohas Brook Sewers, Contract No. 2

Manchester, New Hampshire

Client: City of Manchester, New Hampshire


  • Construction Administration
  • Construction Observation
  • Deep Sewer Design
  • Easement Acquisition
  • Microtunneling (Trenchless Technology)
  • Permitting
  • Preliminary Design

Project Summary

The Cohas Brook Interceptor was the last of the Manchester Water Pollution Abatement Program priorities to be evaluated and designed. This final sewer interceptor consisted of approximately ten miles of sewer pipe divided into three phases, and serviced the entire southern and eastern portions of the City of Manchester as well as portions of Auburn and Londonderry. Construction of the interceptor allowed outlying areas currently serviced by subsurface disposal systems or small community pump stations to tie directly into a sewer main. Placement of this interceptor eliminated the need for at least seven municipal pump stations, and approximately another five private pump stations.

Hoyle, Tanner was part of a team of consultants for Contracts 1 and 2, which included the design and construction of 20,000 linear feet of 36″ and 42″ diameter sewer. As part of the design and construction, microtunneling was used to avoid wetlands, mitigate high traffic volume roadway crossings, and to lessen impacts of residential properties along Pine Island Pond. Hoyle, Tanner designed Phase I – Contract 3 of the Cohas Brook Interceptor project for the City of Manchester. This project included over 3,500 linear feet of 36″ and 24″ diameter sewers through and adjacent to wetlands in the vicinity of Routes I-93 and 293; 9,300 linear feet of 15″ and 8″ gravity sewers, a 6″ force main on Candia Road; and 1,200 linear feet of gravity sewer in the Pine Island Pond area.

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