Transportation
Transportation
Featured project Water
Second Narrows Water Tunnel
A deep-buried pressure tunnel carrying drinking water beneath a seismic fault — designed to keep performing long after the shaking stops.
Featured project Wastewater
Storage that protects our water.
Deep CSO storage tunnels and conveyance systems that capture storm overflows before they ever reach a river, a bay, or an ocean.
We build the tunnels cities depend on.
For more than 25 years we have worked below ground — designing, analysing and managing tunnels, shafts and caverns for the clients who keep a modern city functioning.
Our engineers are tunnel people. Geotechnical specialists, structural designers, constructors, claims consultants and computational modellers sit in the same teams and speak the same language: what will the ground do, and what will we do about it?
That means fewer surprises below ground, faster decisions above it, and infrastructure that keeps performing for the decades it was built to serve.
25+
Years Underground
1,200+
Projects Delivered
1
Head Office
2005
Founded in Seattle
Deep expertise, where it counts.
Four markets, one set of core capabilities. Wherever the ground is difficult, the schedule is fixed, or the consequences of failure are high, we are at our best.
Water
Water
Wastewater
Wastewater
Energy & Mining
Energy & MiningServices built around the ground.
From the first feasibility question to the final claim, we provide the engineering, the management, and the independent judgement that underground projects need.
Tunnel design, underground structures, shafts and caverns for transit, water and utility programmes.
Bored tunnelling, cut-and-cover, shaft sinking, caverns, cross passages, TBM and drill-and-blast design, and specialist underground architecture.
Horizontal microtunnelling, pipe bursting and Direct Pipe installation with minimal surface disruption.
Microtunnelling, auger boring, horizontal directional drilling, pipe bursting and Direct Pipe — specified, designed and delivered.
Condition assessment, roped access, mapping and permanent repair of existing tunnels and shafts.
Roped access, high-definition mapping, structural repair, lining rehabilitation, shaft rehabilitation and emergency stabilisation.
Independent technical advice for owners, from feasibility and selection through to claims and disputes.
Feasibility studies, procurement strategy, design review, constructability advice, expert witness and dispute support.
Multi-disciplinary design, analysis and digital engineering for complex underground assets.
Structural, geotechnical, civil and computational analysis, BIM coordination, and digital twin development.
Staff augmentation, resident engineering, inspection and testing, and project controls on live sites.
CM, CM/GC and owner’s engineer services, inspection and testing, schedule and cost control, and site supervision.
Contractual clarity from notice to resolution, supported by forensic engineering.
Claims analysis, change and delay entitlement, negotiation support, mediation and expert determination.
Proof, underground.
TransportationCentral Subway
A 3.1-mile underground extension of the Market Street subway, delivering twin bored tunnels, three underground stations and a cavern beneath an operating city centre.
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TransportationNorthgate Link Extension
A 4.4-mile light rail extension including two cut-and-cover stations, a cut-and-cover crossover and 2.5 miles of underground guideway.
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TransportationSydney Metro City & Southwest
Metro-scale station caverns and twin running tunnels on Australia’s largest urban rail programme.
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TransportationCaldecott Improvement Project
A four-bore highway tunnel through the Oakland Hills, including a 3.5-mile bore and seismic retrofit.
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TransportationSR 99 Alaskan Way Viaduct Replacement
A four-lane, four-block downtown viaduct built as a structurally independent tunnel beneath a working street.
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TransportationCoos Bay Rail Tunnel Rehabilitation
Rehabilitation and rock-lining repair of six miles of historic single-track rail tunnel in basalt.
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From below ground.
Northeast Ohio Regional Sewer District’s Shoreline Storage Tunnel
A breakthrough on the CSO storage tunnel serving the Lake Erie shoreline, with commissioning on track.
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Underground Science Facility Wins National Award
Our deep underground science cavern complex takes a top honour for engineering excellence.
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Hoffman Tunnels Announces New Director of Growth and Principal
A new principal joins to lead business development across our transportation and water markets.
Read more
Have a project that goes underground?
Tell us about your site, your ground, and your programme. We will tell you honestly what is possible, what it will take, and how quickly we can get you moving.