Manchester Started Construction on Drain Tunnel

The $360 million project aims to prevent raw sewage from entering the Merrimack River during heavy storms.

Updated on Oct. 1, 2026 in Construction

Isometric editorial illustration of a large concrete drain pipe in an excavation trench, depicting municipal infrastructure development. — Manchester officials began work on a $360 million tunnel system to divert stormwater and curb sewer overflows into the Merrimack River. AI Illustration. Upload story photo >

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Manchester broke ground in August 2026 on the Cemetery Brook Drain Tunnel Project to address city sewage overflow. The infrastructure initiative serves to separate stormwater from the sewer system.

Why it matters

Major storm events previously overwhelmed city sewers, forcing raw waste into the Merrimack River and causing backups in homes and streets. This project fulfills a 2020 agreement with the EPA to improve municipal water management.

The project involves building a 12-foot-wide tunnel spanning more than two miles at a depth of 60 feet underground. The $360 million construction cost represents a major investment in the city infrastructure.

The players

Manchester

Manchester is the largest city in New Hampshire and the site of this major infrastructure project.

Environmental Protection Agency

The Environmental Protection Agency is the federal agency responsible for setting national standards for water quality and sewage management.

The details

Crews are utilizing a tunnel boring machine to carve the new system, which is designed to divert rainwater away from the existing sewer infrastructure. This separation prevents the system from being overwhelmed during significant rainfall, mitigating environmental risks to the local waterway.

The city signed an agreement with the EPA in 2020 to reduce sewage overflow.
Construction on the project officially broke ground in August 2026.
Engineers expect the tunnel to reach completion by early 2029.

Market Landscape

This project reflects a national trend of municipalities undertaking massive subterranean construction to update legacy sewer systems. It mirrors efforts seen in other major cities to meet federal water quality standards while expanding capacity to handle extreme climate-driven weather.

Residents should anticipate localized construction activity and potential traffic adjustments near the tunnel site through 2029. Long-term, the project aims to reduce the frequency of sewer backups that impact city streets and residential basements.

The takeaway

Large-scale infrastructure projects are essential for cities looking to mitigate the damage caused by increasingly volatile weather patterns. Residents can expect improved municipal drainage efficiency once the new tunnel system is fully operational.