The Boring Company’s Music City Loop in Nashville has reached a major milestone as two 400-ton Prufrock tunneling machines actively race through solid limestone, pushing forward at 14,000 psi compressive strength. According to autonocion.com, the 19-mile underground transit project funded entirely by the company aims to connect downtown to Nashville International Airport by spring 2027.
Large-scale tunneling efforts typically provide a single primary image before disappearing from public view for several years while the equipment works unseen. The Boring Company has opted to manage its Nashville excavation more like a sports season, sharing performance statistics and drone footage while the borers remain beneath the surface. The September updates showed the operation moving fast.
Twin Prufrock Machines Race Through Nashville Limestone
The project began with a single machine in the ground, but recent drone footage posted by the company shows Prufrock-MB1 and Prufrock-MB2 tunneling at the same time. Broken limestone rides a conveyor out of each bore, climbing two side belts stacked one above the other to a shared rock pit. Hauling rock out is half the job because if the spoil cannot leave as fast as the cutterhead makes it, a machine built to never stop cutting ends up stopped anyway.
According to the company’s August project update, MB2 began operating from the Lot 16 worksite in August following the completion of commissioning, utilizing its initial weeks for testing while MB1 continued its forward progress. The company set up the race itself, asking publicly whether MB2 would catch the head start MB1 has held since February.
Boring machine exerts millions of pounds of force into limestone
As reported by The Tennessee Star via the company’s update, a post from Friday night provided specific figures regarding MB2’s advancement: over 4,000,000 pounds of lateral gripping force and more than 1,000,000 pounds of axial thrust to penetrate the limestone of Music City. A borer cannot just floor it like a truck because there is nothing solid to push off down there except the tunnel itself. Prufrock applies four million pounds of pressure to clamp its grippers against the walls, using that stability to push the cutterhead into the rock with a million pounds of force.
The machine was designed for the kind of ground found in these core samples, which consistently show a compressive strength of about 14,000 psi, as it installs the tunnel lining during the cutting process without pausing for segment work. MB2 also swings 17-inch disc cutters, up from 15.5 inches on MB1, giving the newer machine more bite in the consistent rock.
Project targets spring launch with expanded downtown station list
The JW Marriott Nashville was added to the station list in the August update, joining the Music City Center easement, the airport station that received an 8-0 approval from the airport authority, and a private station serving the Paramount, Alcove, and Prime towers downtown. The cars doing the driving will be Teslas, Model Ys and Model Xs with human drivers to start, promising roughly 10 minutes from BNA to downtown.
The schedule has shifted slightly from late 2026 to spring 2027 for the first operational phase, according to The Tennessee Star. Meanwhile, Metro Council voted to formally oppose the project in March over safety and environmental concerns, though state approvals allowed the digging to continue.
Frequently Asked Questions About the Nashville Tunnel Project
How much is the Music City Loop project costing The Boring Company?
The Boring Company is self-funding the 19-mile two-tube route between the Tennessee State Capitol and Nashville International Airport, with total costs estimated between $240 million and $300 million.
What vehicles will transport passengers through the Music City Loop?
Initial operations will utilize Tesla Model Y and Model X vehicles driven by human operators to transport passengers from downtown stations to BNA in approximately 10 minutes.
How did local government officials respond to the underground transit project?
Metro Council voted to formally oppose the project in March over safety and environmental concerns, but state-level approvals allowed tunneling operations to move forward regardless.
Related reading