Every Mile a Miracle

Subways under cities,
tunnels through water
aerial ways across open country -
that's BART -
...the world's newest rapid transit system

Digitized from the archives of the Western Railway Museum.

As big cities go, San Francisco is not itself extremely large-in square miles, that is. It's the core, however, of a galaxy of satellite cities and towns which jostle each other, shoulder-to-shoulder, across a 3-county cosmos.

Naturally, like all large metropolitan areas, the San Francisco complex has a transportation problem. Yet, if any place in the country could be excused for side-stepping the issue of mass transportation, San Francisco, with its steep rocky hills and encircling water barriers, is that place.

Most other burgeoning population centers, like Miami, Washington D.C., or Los Angeles, have adopted a wait-and-see approach, settling meanwhile for extensive expressway systems to handle masses of privately operated vehicles. Only two metropolitan areas in North America have added rapid transit systems during the past half century - Toronto and Montreal.

Now the Bay Area's 3-county megalopolis has joined its forces to create the most ambitious, most sophisticated mass transportation network yet - and the one expected to most profoundly affect a renaissance of rapid transit systems.

Already the Bay Area Rapid Transit System - BART, as it is known locally - is under construction, and the first segment of its 75-mile, 1.2-billion-dollar network will be operational by 1970. The whole system will be running two years later with a capacity to move 30,000 seated passengers per hour in 80 mph luxury. Its complex network will be served by 37 stations where riders can park up to 20,000 automobiles while patronizing the high-speed trains.

With attention now focused on construction, over half of the construction contracts have already been let. Massive prefabricated twin-tube sections are taking their places across the floor of San Francisco Bay at the rate of one Section every two weeks. More than a score of contractors are simultaneously are simultaneously boring tunnels through mountains, excavating subways under cities, erecting aerial lines through rural are through rural areas and building stations and rail equipment.

Even as construction progresses, all features of the automated rail equipment -from the cars' interior carpeting to the automatic train control devices - are being tested on the system's 4 ½ mile test section in Contra Costa county, east of Oakland.

The pivotal segment of the system is the world's largest and deepest underwater tunnel which will connect downtown San Francisco with Oakland across the Bay. The twin tubes forming this vital 4-mile underwater link will permit simultaneous 2-way, 8-minute commuting between the two key cities in the system.

When a feasibility study for a mass transportation system in the San Francisco Bay area was undertaken in 1952 it was determined that the tube concept offered the only practicable way to hurdle the Bay's wet barrier. Underwater operations were actually begun late in 1966, and a 60-foot wide trench in which the double tube will be bedded is presently being excavated. To remove the 1,500,000 cubic yards of sand and silt, a Detroit Diesel powered dredge, the SAN MATEO was brought into play.

Originally unpowered and utilizing electricity generated on a separate barge, SAN MATEO now has four pairs of tandem Detroit Diesel 16V-71 turbo gensets, a compact power installation Williams & Lane, the Detroit Diesel Distributor in the San Francisco Bay Area. Benefits from the new SAN MATEO power setup are several-greater power capacity (3200 KW vs 2400 KW), the ability to increase power by smaller increments, and to work without risk of power cut-off at an outside source. Also working on the dredging project are three 45-foot steel tugs built by Equit- able Equipment Co. of New Orleans. BECKY, MARCEY and SAN CARLOS, each driven by two 6-71N Detroit Diesels, were brought to the West Coast by rail to help in positioning the tunnel dredge, and to service the work barges and supply barges.

For its 4-mile distance across the bottom of the bay, the 60-foot wide trench has a gravel bedding or foundation on which the tube's 330-foot sections rest. Accurate and permanent setting for each section depends to a large extent on uniformity and precision in grading this gravel course, which at one point drops to 130 feet below the bay's surface.

The task of screeding the gravel uniformly despite the dips and curves is one of extreme complexity. It is a delicate job, handled by a one-of-a-kind screed barge measuring 85 feet wide and 240 feet long and floating on two 17-foot diameter buoyancy tanks.

Heavy anchors at each corner of the barge hold it against the partially submerged buoyancy tanks-virtually rigid astraddle the excavated trench. Its screed frame and hopper rolls on tracks along the sides while three vertical tremmies discharge the gravel into the trench.

The double drum winches that anchor the barge in position are powered by 4-71 Detroit Diesels. Also, a 6-71N turning a 150 KW generator set, provides the power for the screed bridge and the surface.