The Boring Company is accelerating construction of the Music City Loop, with two tunnel boring machines now mining simultaneously, a third preparing for a late-October launch and a fourth already being built.
In its latest official Music City Loop construction update, published October 1, TBC said Prufrock-MB1 and Prufrock-MB2 are actively tunneling at the same time, Prufrock-MB3 is scheduled to launch later this month and Prufrock-MB4 is under construction. The company says it is pushing to have four tunnel boring machines in the ground before the end of 2026.
That would mark a major expansion of the underground construction operation that began with a single machine launched from Lot 16 near the Tennessee State Capitol.
Two machines are now tunneling at the same time
The most important construction milestone in the October update is that MB1 and MB2 are now mining simultaneously. TBC had already reported both machines active by August, but the new update emphasizes that the Nashville operation has reached the point of supporting two active TBMs at once.
That means the site is simultaneously handling inventory, trucking, tunneling support activities and workspace for design and operations personnel while both machines advance underground.
TBC says it is doing all of that from a construction footprint of less than one acre, underscoring the company's effort to keep surface disruption limited as underground activity expands.
More than 300 upgrades made to MB1
The October update also provides one of the clearest indications yet of how aggressively TBC is modifying its equipment in Nashville.
According to the company, the Nashville team has made more than 300 upgrades to Prufrock-MB1. TBC says improvements that increase speed or reliability can sometimes be identified, designed, fabricated, shipped and installed in roughly 48 hours.
Those changes are not staying with the first machine. TBC says the upgrades developed on MB1 are being incorporated into the machines that follow it, meaning later units can begin work with lessons learned from the earliest Nashville tunneling already built in.
MB3 preparing for a late-October launch
The next major milestone is Prufrock-MB3. TBC now says the third machine is expected to launch in late October.
That is a more specific timetable than the August update, which said MB3 was on track to arrive in Nashville in September. The October post focuses instead on launch preparation at a new site.
TBC says excavation of the new launch pit is underway and that it coordinated with Metro Water Services to obtain the permits needed for that excavation work.
Nashville Electric Service is also providing electrical capacity sufficient to power two TBMs plus supporting equipment. TBC says that same electrical infrastructure is intended eventually to support operation of the completed tunnel.
The new site is being equipped with office trailers, a Safety Center, an Operations Control Center, chilled-water infrastructure, compressed air, network connections, cameras and other tunneling-critical systems.
Taken together, those preparations indicate the new location is being built as a substantial tunneling support site rather than simply a temporary excavation point.
A fourth tunnel boring machine is now being built
The biggest forward-looking announcement in the October report may be Prufrock-MB4.
TBC says a fourth Nashville tunnel boring machine is now being built. The company did not give a specific delivery or launch date for MB4, but it says the team is pushing to have four TBMs underground before the end of the year.
If that target is met, the Nashville project would move from one underground machine early in 2026 to four deployed machines before the close of the same year.
That matters because TBC's construction strategy depends on parallel excavation. Multiple machines working from different launch points can advance different tunnel segments at the same time instead of relying on a single TBM to complete the system sequentially.
All permits needed ahead of tunneling are now obtained
On the regulatory side, TBC says all permits and approvals required ahead of tunneling have been obtained.
The company specifically pointed to the regulatory coordination needed to mobilize the new MB3 launch site and said agencies had moved quickly to support safe and compliant construction.
The central state approval remains the Tunnel Permit and Lease Agreement between TBC and the Tennessee Department of Transportation. Executed February 25 after more than seven months of technical review, that agreement authorized roughly 25 miles of tunnel within TDOT right of way and allowed tunneling within the permitted corridor.
The October post does not identify a remaining pre-tunneling permit that is blocking continued underground construction.
More than 40 stations remain in planning and design
While underground construction is scaling up, the station network is continuing to develop largely behind the scenes.
TBC says more than 40 Music City Loop stations are now in various stages of planning and design, with the company continuing to negotiate directly with property owners along the route.
That figure is unchanged from the August update but remains one of the most consequential numbers in the project. The Loop model depends on a large number of relatively small stations so vehicles can travel directly between origins and destinations without stopping at every intermediate station.
BNA station still in design and permitting
Nashville International Airport remains one of the anchor stations. The Metropolitan Nashville Airport Authority previously voted 8-0 to approve a Music City Loop connection and station at BNA.
The October update says the airport station is still in design and permitting.
Under TBC's current project description, the airport alignment begins near Lot 16 at the State Capitol, runs south along Rosa L. Parks Boulevard to 8th Avenue South, continues southeast along Lafayette Street and Murfreesboro Pike, follows Donelson Pike and reaches BNA. TBC continues to describe the planned BNA-to-Lower-Broadway trip as roughly 10 minutes.
Music City Center station design continues
The Music City Center Authority previously voted 8-0 to approve a tunnel easement across convention-center property. TBC says work with the convention center continues as the station design is finalized.
Residential and hotel stations remain part of the buildout
TBC also reiterated its first announced residential Music City Loop station agreement, which is planned to serve residents of the Prime, Alcove and Paramount towers downtown.
The JW Marriott Nashville agreement also remains active. TBC says the downtown hotel and the company have agreed to terms for a station that would provide hotel guests with direct access to the Loop network.
Those agreements illustrate the model TBC is pursuing in Nashville: a network combining major public destinations with privately integrated stations at residential, hospitality and commercial properties.
TBC is continuing to acquire property along the alignment
The October update includes another notable statement: TBC says it continues to acquire land along the tunnel alignment.
The company says those properties can support tunneling operations during construction and later become useful passenger stations once tunneling is complete.
That strategy means some of today's construction staging locations may become permanent parts of the operating network. It also suggests the publicly announced station map is still incomplete.
The overall route and opening target did not change
The October update does not announce a change to the overall Music City Loop concept. TBC continues to describe an almost 25-mile underground network connecting Nashville International Airport, downtown, Lower Broadway and the West End corridor.
The company's original July 2025 announcement said initial portions of the system could become operational as soon as the fourth quarter of 2026. The October construction post does not announce a revised passenger opening date.
Instead, the immediate timetable is focused on construction: MB3 launching in late October and the company attempting to have four TBMs underground by year end. Those are construction milestones, not an announcement that the full network will be carrying passengers by December.
Community outreach and hiring continue to expand
TBC also reported growth in its Nashville outreach. The company says it has now engaged with more than 275 community, educational, nonprofit and professional organizations and has participated in more than 160 volunteer events across Middle Tennessee.
The company says it has responded to more than 220 inquiries submitted through its Nashville email address and continues to host site tours for residents, business owners, students, elected officials, community leaders and regulatory agencies.
Hiring is also continuing as the project scales. TBC says it is recruiting local talent and working with Nashville-area universities to connect with students and recent graduates.
From one machine to four
The broader story in the October update is how quickly the Nashville project is moving from initial tunneling into a multi-machine construction operation.
At the beginning of 2026, MB1 was still being commissioned at Lot 16. Tunneling began after the TDOT agreement was executed in February. MB2 followed. By August, both machines were active.
Now TBC says MB1 and MB2 are mining simultaneously, MB3 is preparing to launch from a second fully equipped site and MB4 is already being built.
The next target is the company's most ambitious Nashville construction milestone yet: four tunnel boring machines underground before 2027.
If TBC reaches it, Music City Loop will enter next year with multiple tunnel headings capable of advancing at the same time across Nashville — a substantially different operation from the single launch site and single machine that started the year.
SOURCES
- Music City Loop Blog Post — October 1, 2026 · The Boring Company
- Music City Loop · The Boring Company
- Nashville selected by The Boring Company for underground Loop project · The Boring Company