Tunnel Boring Machine (TBM)
A Tunnel Boring Machine (TBM) is a large cylindrical mechanical excavation device designed to bore circular tunnels through rock and soil. TBMs range in diameter from small utility-scale machines to massive civil engineering units capable of boring tunnels over 35 feet in diameter. They are the primary conventional technology cited in DUMB construction theory as the mechanism by which deep underground military tunnels and connecting passages could be constructed.
How TBMs Work
A TBM's rotating cutting head is equipped with metal attachments made of super-hard alloys that grind and gouge through rock as the head turns. Excavated rock — called "muck" — is passed by a conveyor assembly to the rear of the machine, where it can be removed by truck or rail. The machine is hydraulically forced forward as the cutting head advances, boring a continuous circular tunnel.
Performance Characteristics
According to data cited by Richard Sauder from informant testimony and industry records:
- A TBM operated by approximately 10 men can bore up to 10 miles per year under favorable rock conditions.
- The Pacific Gas and Electric Company, using a Robins Company TBM to bore a 22,000-foot long, 24-foot diameter tunnel, achieved a rate of 5–6 miles per year.
- More favorable conditions can achieve rates of 10 miles per year or greater.
At these rates, a TBM could connect facilities like China Lake Naval Air Weapons Station and Edwards Air Force Base (approximately 55 miles apart) in as few as five and a half years.
Spoil Disposal and Concealment
A key challenge in clandestine TBM use is disposing of the excavated rock without creating visible surface disturbance. This problem was recognized even by the Nazis in their WWII underground construction: post-war Allied examination of Nazi facilities noted that excavated rock "had been carefully scattered into hills miles away," leaving no surface evidence of major construction. The Bureau of Reclamation hypothesis — routing clandestine secondary tunnels off of legitimate water infrastructure tunnels — partially addresses this by allowing muck to be mixed with legitimate tunnel waste.
Defense Industry Use
Multiple major defense contractors and research entities cited in UAP legacy program research have conducted above-board TBM and tunneling research:
- Bechtel Corporation (1974 report: "Research Program Plan for Meeting Tomorrow's Needs in Tunneling and Excavation") identified underground defense facilities including ICBM silos and command posts as representing large demand for tunneling.
- Battelle Memorial Institute participated in the US National Committee on Tunneling Technology (USNCTT).
- Sandia National Laboratories also participated in the USNCTT.
- TRW participated in the High-Speed Ground Transportation Initiative studies.