US Transportation Secretary Ray LaHood has been touring European HSR systems in recent days and is coming away impressed:
Spain's bullet train system is a model to follow as America plans how to spend the money the government is injecting to stimulate the economy, the U.S. transportation secretary said Saturday....
The Spanish network is likely to interest the U.S. government because its specially designed, electrified tracks — first devised for the French TGV system — are not as expensive to lay and run as some German or Japanese alternatives.
And Spanish state-of-the-art tunneling technology has proved successful in boring efficiently through mountain ranges to reach the cities of Valladolid and Malaga.
LaHood met with Spain's Prime Minister Jose Luis Rodriguez Zapatero to discuss how investing in such a train system could stimulate job creation in the U.S.
"Yesterday I traveled on a train at close to 350 kilometers (215 miles) per hour, the fastest I've ever ridden on a high-speed train," LaHood said. He said he had enjoyed a conversation and beverage aboard and found the experience very civilized.
"Our leaders have made the decision that America will have high speed rail," LaHood said.
As a longtime aficionado of the AVE system I am pleased, but not surprised, to see LaHood taking to the Spanish system. Because the Iberian Peninsula had its own rail gauge, Spain had to build all-new tracks using standard gauge for the AVE - meaning they have dedicated HSR tracks just as California will. Of particular interest is the tunneling technology Spain has employed, as The Transport Politic points out:
What is clear is that the distinctively Spanish obsession with using tunnel boring machines (TBM) seems to be a model for the Transportation Secretary; these semi-automated devices save on both time and cost in building underground rail corridors. For example, the 3.5 mile tunnel under downtown Barcelona, which is part of a larger project that will allow high-speed trains from central Spain to reach France, will only cost 180 million Euros to build. That’s far cheaper per mile than any similar U.S. tunneling project, and part of the explanation is the efficient use of those TBMs.
TBMs will be a godsend here in California where significant tunneling in the Pacheco Pass and Tehachapi Mountain areas will be needed to complete the system. Of course, I am sure that the Peninsula NIMBYs will seize on this as well as an argument that their tunnel is financially viable - which it probably isn't, and besides, they need to defend the position that their tunnel is more important than the all-important Pacheco and Tehachapi tunnels which are sorta necessary for the whole project to work as intended.
It's also possible that the tour is going to reconfirm for Ray LaHood the importance of adopting European safety standards for HSR trainsets. The FRA's weight rules need to be modernized - the current rules are an embarrassment and an impediment to proper HSR development in America. As the head of the Department that includes the FRA, LaHood is in a strong position to insist that the FRA enter the 21st century.
Perhaps the most important aspect of LaHood's visit is intangible - a renewed commitment to building European-style HSR here in America. Currently the only project that meets that standard is California's. I have every reason to believe this trip to France and Spain will bolster LaHood's demonstrated conviction that California's HSR project is deserving of robust federal support.
Tunneling is like a box of chocolates, you never know what you're going to find.
People have been constructing tunnels for thousands of years and, it's always been a royal pain in the keister. Often, the motivation was access to minerals like salt, coal and metal ores. The ancient Greeks and later, the Romans, painstakingly hollowed out mountains to create gently sloping water galleries that supported their cities. These days, the best-known tunnels are for transportation arteries, i.e. roads and rail. Think of the Seikan linking the islands of Honshu and Hokkaido in Japan, the Channel Tunnel between France and the UK and, the Saint Gotthard and Lötschberg base tunnels through the Alps in Switzerland to name just a few. There are even plans for a rail tunnel under the Straits of Gibraltar that would link Spain and Morocco. Like the Tsugaro Strait, this area is seismically active. Also, the combined weight of the overburden and the water above it would squeeze out water trapped in the rocks surrounding the tunnel. Pumps would have to operate continually just to keep it from flooding, at least during the construction period.
By comparison, each of the tunnels in the California HSR network will be a run-of-the-mill project - but only when viewed in isolation. All told, the construction of the starter line will involve dozens of track-miles of tunnel construction.
Mountain Crossings
Individual tunnel systems longer than 6 miles must feature additional emergency escape routes, but that will not be necessary in the context of the HSR project. All the major slip-strike faults along the route can be crossed at grade, which greatly simplifies not just rescue efforts but also repairs to the tracks. However, a secondary fault near Pacheco Pass will have to be crossed underground.
During a 2001 tunneling workshop (report, slides), CHSRA used Australian software called Quantm to identify optimized alignment options for each possible route choice through e.g. the transverse range, based on the best available geological information at the time. The software automatically generated and analyzed thousands of variations to cull those that did not meet constraints such as bore length, maximum gradients and the desire to cross major faults at grade.
The results overturned those of a less sophisticated 1994 study by Parsons Brinkerhoff, shaving billions off the estimated cost and sharply reducing the risk of drilling into pockets of natural gas or aquifers. For reference, 32 workers died in an explosion during the construction of railroad tunnels through the Santa Cruz mountains in the 19th century. More recently, errors in tunnel design and construction in Andalucia (Spain) led to a major environmental disaster for a once-thriving small town of Valle del Abdalajis:
For reference, similar water columns exist in Pacheco Pass, draining them would turn prime farmland in part of the west side of the Central Valley near Los Banos into a virtual desert.
Among other findings, the Quantm study showed that an alignment along the Grapevine is affordable, though far fewer feasible variations were found there than through the Tehachapis. The only one that crosses both the Garlock and the San Andreas at grade would run close to the wildlife refuge at Lake Castaic. Considering that there is always uncertainty regarding the detailed geology inside mountain ranges, engineers recommended the latter option, even though it adds 60 miles and 12 minutes to the SF-LA line haul time. For a map of where the tunnels through the transverse range will be, plus cross-sections of the alignment at selected points, see part 1, part 2 of the Bakersfield to LA portion of the program EIR/EIS.
The decision in favor of the Tehachapis dovetailed nicely with LAWA's plans to leverage Palmdale as a relief airport for LAX, but it also risks promoting further population growth - transit-oriented or otherwise - in the arid High Desert. Moreover, it was one of the factors that prompted CHSRA to select the fastest possible route out of the Bay Area. According to CHSRA's analysis, San Jose to Fresno via Pacheco is 10 minutes faster than via Tracy. Are the time savings worth sacrificing an SF-Silicon Valley-Sacramento run-through route via SantaClara/SJC that would be time-competitive with driving on I-80 and other congested Northern California freeways/bridges? Controversially, CHSRA concluded that they are.
In a recent and bitter twist to this saga, the foreclosure fiasco recently prompted United Airlines to cancel its last remaining flights between Palmdale and SFO due to lack of demand. Without any prospects for attracting other commercial carriers anytime soon, LAWA is now mulling "temporarily" converting the airport into a giant solar farm. That would have to be relocated - at considerable expense - in the future before the airport could be re-opened, because the glare of the solar farm would blind pilots. Renewable electricity is wonderful, but without planning certainty regarding Palmdale airport, an HSR detour via the High Desert makes no sense at all.
Tunneling Techniques
Civil/mining engineers have multiple technologies at their disposal, the optimal choice depends on the geology involved. Very long tunnels involve massive logistical efforts to get personnel and materials to and from the face of the tunnel during construction, so small exploratory tunnels and/or shafts are excavated to improve knowledge of the local geology at the meter scale. For the Channel Tunnel, whose alignment follows a seam of chalk marl, construction of the third (service) tube was used for the purpose. Base tunnels in the Alps rely on vertical shafts as emergency escape routes of last resort, supplementing the horizontal route along the length of the adjacent track. For high speed trains, engineers prefer separate tubes in each direction, linked every so often by cross tunnels. Trains act more or less like pistons, pushing a column of air out ahead of them. In addition to serving as evacuation routes, the cross tunnels provide a way for the air to escape, reducing drag losses. The cross tunnels feature firewalls that are closed in the event of a fire in one tube so the other is preserved for limited service during repair works. This off-design scenario applied to the Channel Tunnel just recently.
Extremely hard rock must be carefully blasted with dynamite, which is why the Swiss base tunnels feature a single tube for two adjacent tracks. This is suboptimal for high speed operations because the aerodynamic interactions of the train with its surroundings are asymmetrical, which can cause sway (lateral motion) and even dynamic instability. However, since those tunnels will carry mostly freight and auto trains, the lower cost of blasting just one tube won out. These days, engineers try to apply the New Austrian Tunneling Method, which relies on precise measurements of the way the overburden (rock above the tunnel) settles as the load redistributes to either side of the tunnel. The application of shotcrete (sprayed concrete grout) and especially, the installation of support rings assembled from prefabricated segments are avoided as much as possible to keep costs down.
For rocks of intermediate hardness, the cheapest and hence preferred option these days is to use a pair of giant Tunnel Boring Machines (TBMs). These leviathans feature a huge rotating cutting face supported by a support infrastructure for slurry (water + bentonite, a mineral lubricant), rock crushing and shotcrete/ring construction to stabilize the section just excavated. The ring segments are shaped such that the two faces of the completed ring end up at a slight angle to one another. This permits the implementation of tunnels with gentle lateral and/or vertical curves. Laser-based geodetic systems are used to precisely guide the direction the TBMs take, such that two such machines drilling toward one another meet up within inches of each other after miles of tunnel construction. In the Channel Tunnel project, the business ends of the TBMs were steered past each other and parked in dead ends for the rest of eternity, because it would have been more expensive to dismantle and remove them.
TBMs are also used for tunnel construction in urban areas, e.g. the Canada Line light rail project in Vancouver, BC. To get a better idea of just how complex and risky tunnel construction in built-up areas can be, I highly recommend you take 50 minutes to watch the following excellent documentary on the Kuala Lumpur Mega Tunnel (the other SMART) project in Malaysia (while it's still available). The single giant bore and dual use objective differentiates it from what would be needed for boring deep tunnels for four tracks underneath Palo Alto, an idea that CHSRA has been asked to study. In addition to the massive disruption to vehicular traffic and residents near the point(s) of surface access, the single biggest headache would be the risk of subsidence under the active rails, an existing under- or overpass, the frontage roads and high-value buildings such as hospitals and high schools. The end result may be worth having, but construction could be a nightmare.
As for the price tag of $250 million, Malaysia isn't Silicon Valley. Not even close. If the project to extend BART to Santa Clara via bored tunnels through San Jose is any indication, figure upwards of $500 million per mile in the Bay Area.
For soft rock, such as is found in downtown San Francisco, the preferred option is to cut deep trenches from the surface and cover them later on to restore the road surface. This is noisy, messy and highly disruptive to traffic during the construction period, but you can't make an omelet without breaking any eggs. Unfortunately, trains - high speed trains in particular - cannot negotiate tight corners, so buildings above them either have to be demolished first or, old-fashioned shield construction techniques applied. These are very labor-intensive and therefore expensive. Flooding, subsidence and earthquake risks all complicate their application, so they are used as sparingly as possible.
On the plus side, the incremental environmental impact required to construct two levels of tracks stacked on top of one another isn't all that great. This may be why some are advocating the construction of a second deck of platforms under the new Transbay Terminal Center. Personally, I very much doubt claims that the capacity afforded by the present single-deck design with 6 full-length platform tracks will ever present a bottleneck for HSR or even Caltrain. Also, access to platforms on a second, deeper deck would introduce serious pedestrian flow capacity and emergency evacuation issues, in addition to substantially higher cost. While there will be no tanks full of diesel or other flammable materials to worry about, extremely rare electrical fires are possible - as are earthquakes or terrorist attacks.
Conclusion
There are ways to put trains underground, but digging always involves a lot of risk and money. All possible above-ground approaches should be evaluated and rejected before opening Pandora's Box.
The California High Speed Rail Blog is a creation of Robert Cruickshank. The articles posted here are the opinion of their respective authors and no other entity. To contact Robert, send an email to his last name at gmail dot com.
