News Roundup, October 2022

CBOSS Dumpster Fire Update: the CBOSS case is still making its way through San Mateo County Superior Court (under case file 17CIV00786). The trial was held in April through June of this year, and closing briefs are due in December. Closing arguments are currently scheduled to be made in court on the 5th of January 2023. The latest kerfuffle is over a post-trial Caltrain/Parsons motion to seek punitive damages from Alstom for intentionally, not just negligently, lying about the status of the project based on testimony given during the trial.

Trains Without Wires: Caltrain held a VIP invitation-only unveiling of the new EMUs in San Francisco on September 24th. Four trainsets (serial production #2 - #5) have now been delivered and will collect dust (graffiti?) for a couple of years because the electrification of the corridor is far from done. The new trains were hauled to San Francisco by diesel power.

New Palo Alto downtown
grade separation

Stirring Things Up In Palo Alto: Caltrain recently briefed the city on their plan to replace the ancient bridge over the San Francisquito Creek. This is precipitating a sudden change to the city's years-long policy of kicking the can down the road on what to do about a future grade separations at downtown Palo Alto. While everybody seems to assume the bridge and grade separation projects are necessarily linked, they are not! The solution is pretty darn obvious: replace the Palo Alto Ave crossing with a new grade separation at Everett Ave, which would connect downtown to El Camino as shown in the sketch at right.

1. Permanently close and demolish the Alma bridge over University Ave, instead connecting Alma to University via the existing cloverleaf ramps reconfigured as a signalized intersection.
2. Build a new downtown elevated grade separation viaduct and platforms through the existing station parking lots, along the original track alignment that existed before the University Ave grade separation was opened in 1940. This viaduct would be open underneath, providing station parking, bus platforms, pick-up/drop-off areas, and other station amenities. Bonus: the new straightened track alignment removes a speed-limiting double reverse curve in the tracks.
3. Cut over the trains to the new viaduct and elevated station. 
   
4. Extend Everett Ave under the elevated tracks to the existing intersection at El Camino Real and Quarry Rd, also picking up a new connection to the convoluted and inefficient bus loop. Bonus: bus service is greatly sped up to/from El Camino, Stanford and downtown by avoiding time-consuming looping routes.
5. Permanently close the grade crossing at Palo Alto Ave.
6. Demolish the old University Ave rail bridge, remove the old cloverleaf ramps, and bring the University Ave / Alma intersection back up to a grade level signalized intersection.

This grade separation approach is completely decoupled from whatever happens with the San Francisquito bridge.

More CEQA Lawsuits Flying: the recent certification of the HSR San Francisco to San Jose EIR precipitated several new CEQA lawsuits. Brisbane and a private developer are upset about the sprawling HSR "light" maintenance facility planned in the city, and its impact on the planned Brisbane Baylands development. Millbrae also got in on the action due to a clash between its development plans and the planned expansion of the station footprint for HSR. Unfortunately, the Sacramento Superior Court does not allow free access to case files, so details are hard to obtain.

The Exploding Cost of Grade Separations

Recently, the San Mateo County Transportation Authority prepared a grade separation program update, discussing past and future projects. What immediately jumps out of this document, and others published by Caltrain, is the exploding cost of grade separation projects. The project budgets are shooting through the roof, vastly outpacing inflation. Typical of this cost explosion is the Broadway grade separation in Burlingame, which will grade-separate a single intersection at the eye-watering cost of $327 million.

Cost Modeling of Historical Grade Separation Projects

With the SMCTA slides giving cost data for past and current projects along the Caltrain corridor, it is fairly straightforward to assemble a simple model of grade separation project component costs. All figures are inflated to 2020 dollars before fitting, and we break out unit quantities for each project of the following project components: fully elevated rail over road crossings, split (partially elevated) rail over road crossings, trenched road under rail crossings, pedestrian tunnels, stations, and the number of miles of corridor where the track elevation was changed. With all those quantities broken out for each project, we can fit a simple model that estimates the unit costs by (empirically, not rigorously) minimizing a least-squares fitting residual. The main result of this model is that projects from the mid-1990s through today consistently cost about $36 million per crossing, with not too much variation:

 

That brings us back to Broadway in Burlingame, which according to this model should cost only a third of the price tag of $327 million. That's right, even including two pedestrian tunnels and a new station, the entire Broadway project should cost no more than $100 million. This factor-of-three discrepancy raises some serious questions about how this project is being engineered, and whether it should even proceed in its current form. One could counter that the cost model presented here is too simplistic and doesn't reflect the unique local conditions of this project, but the model does okay with predicting the cost of every past grade separation project over the last 30 years. Is this a case of over-fitting the data, or have the engineers behind this project simply lost their senses?

With the most traffic of all grade crossings on the peninsula corridor and train-on-car collisions occurring on average once a year, the Broadway crossing is at the top of the state's priority list for grade separation, and we all know that you can't put a price on safety. That makes the Broadway grade separation project ripe for name-your-price taxpayer extortion.

Insane Costs are Baked in to the Caltrain Business Plan

A Caltrain business plan presentation from 2019 attempted to quantify the expense of partially grade-separating the corridor for each contemplated service scenario. The cost modeling for this was even cruder than the simple spreadsheet model described above: the costs for each project were either copied and pasted directly from each city's estimates (of wildly varying quality), or a standard grade separation unit cost of $255 - $355 million per crossing was adopted. This value is up to TEN TIMES the value estimated from past and present grade separation projects, and flies directly in the face of common sense. Despite the coarseness of this spreadsheet costing exercise, the resulting grade separation costs (on the order of ten billion dollars regardless of service scenario) were passed along into the regional Plan Bay Area 2050 exercise.

Why have costs exploded for a project like Broadway, which has proceeded far enough into detailed design to accurately estimate construction cost?

Cost Drivers

Utility relocation. Whenever you dig, surprises happen where utilities buried underground are found elsewhere than expected. The more and deeper you dig, the more surprises you will find. Every new discovery delays or even stops construction work, running up costs. Almost every digging project undertaken by Caltrain runs into this situation. Just in the last couple of years: in South San Francisco, construction of a grade-separated pedestrian access tunnel was delayed for 17 months, at an additional cost of $10 million (and still counting!) due to utility relocation issues. In San Mateo, the 25th Avenue grade separation project, where several new crossings were dug, was delayed by over 500 days due to negotiations with Union Pacific over the relocation of fiber optic cables. Pacific Gas & Electric also had to be paid to move a high pressure gas line. The budget for utility relocation almost tripled, from $12 million to $32 million, not counting the cost of construction delays. Meanwhile, corridor-wide, Caltrain's electrification program (while not a grade separation) is continually digging up their own brand new train control fiber optic cables, which were buried in places that don't match what the contractor said they did. This is causing many months of delay to foundation installation. The matter is now tied up in court, as one of several smoldering side sagas in the big bonfire of litigation over the CBOSS project, still building up to a climactic jury trial in 2022.

Vertical curves made for freight trains. Changing the vertical profile of the tracks, whether up or down, is subject to design constraints on the radius of vertical curves, or how quickly (and over what distance) the slope of the tracks is allowed to change. You might think this issue primarily affects faster passenger trains, but amazingly, the biggest culprit is heavy freight. Freight cars maintained to the bare-minimum standards practiced in the United States can derail at the slightest provocation, so industry track design standards are set extremely conservatively. The maximum vertical acceleration allowable for freight cars is 0.1 ft/s^2, six times less than for passenger trains. At equivalent speeds, the grade change (for example from level track to a one percent slope) must then take place over a distance six times longer than for passenger trains. If you wanted to design the vertical profile of a grade separation to the most aggressive vertical radii and shortest structure lengths allowable for passenger trains, the freight trains would have to be slowed down to 1/sqrt(6) of the passenger train speed to stay under their six times lower vertical acceleration limit. On the peninsula corridor, where we design for 110 mph passenger trains, short grade separations require that the freight trains can't go any faster than 45 mph. Unfortunately, new grade separations such as Broadway in Burlingame or downtown Redwood City are being engineered for 60 mph freight speed, which makes all the vertical curves (and bridges, embankments, trenches, etc.) almost 80% longer than they need to be for 110 mph passenger trains.

Vertical curves that can't overlap bridge spans. Recent preliminary design drawings, such as for the Redwood City grade separations, reveal a new design constraint has been applied that does not appear in older Caltrain engineering standards. The vertical alignments are configured such that wherever the track crosses over a bridge span (as for a grade separation) there is no vertical curvature. To understand how wasteful and silly this is, ask any engineer--never mind, ask any kid: is a train bridge supposed to look like design A or design B, where this  constraint has been applied so no vertical curvature exists where the tracks pass above the under-crossing? Anyone can see this design rule will blow up structure height, length, cubic yards of concrete, and of course cost. And yet, that's what we see in all the profile drawings.

Paint-by-Numbers Structure Depth. There are well-worn preliminary engineering rules for how thick a bridge deck needs to be relative to the loads it must support and the width of a span. Blind application of these rules during preliminary engineering, when the vertical track profile is often decided, results in bridge decks that are comically deep, as measured from soffit (bottom surface of the bridge) to top-of-rail. These massive bridges result in a much higher track profile, needlessly increasing the length, height, visual impact, and cost of grade separation projects. Bridge structural forms exist that minimize structure depth, and it is often possible to shorten spans by adding support columns.

How to build affordable grade separations

Here are some golden rules for designing affordable grade separations. These are rules that are clearly not being followed for Broadway, or for the Menlo Park plans, or for the downtown Redwood City plans, and directly contribute to stratospheric cost estimates for these projects.

• dig as little as possible. Wherever possible, go up and over.
  
• limit freight train speeds to no more than 45 mph.
• allow bridge decks and vertical curves to co-mingle.
  
• from the very beginning, aggressively minimize structure depths.

Another important consideration, in view of the large number of grade separation projects that will be required to advance the decadal process of grade separating the peninsula rail corridor, is to standardize designs. There ought to be a small set of bridge designs that can be repeatedly adapted to each situation, using standard prefabricated structural elements. Not every project needs to be a special snowflake.

Build a Dumbarton Rail Tunnel

The Dumbarton water tunnel TBM,
being assembled for the start of its
five-mile drive under the Bay in 2011.

Boring a new tunnel under the Dumbarton corridor, through muddy soils right under a sensitive national wildlife refuge, seems like an impossibly difficult, risky and expensive undertaking in this day and age. But here's a little-known fact: it's already been done.

From 2011 to 2013, a 15-foot diameter tunnel boring machine (TBM) quietly bored a new five-mile tunnel under the Bay from Menlo Park to Newark. The $288 million project, the first tunnel ever bored under San Francisco Bay, is part of the Hetch Hetchy Water System and was built to contain a 9-foot diameter drinking water supply pipe that feeds San Francisco and the peninsula. The TBM that bored the tunnel was an EPB (Earth Pressure Balance) machine and advanced so quickly that it had to wait underground at the far end of its drive, while an access shaft was prepared so the machinery could be retrieved. There were few geotechnical surprises along the way, of the sort that can sometimes blow out tunneling budgets and schedules. The geological layers of clay, gravel and rock under the Bay along the Dumbarton corridor are now better known than they have ever been, and any "geotechnical risk" is effectively retired after the actual boring of an actual tunnel.

Of course, a rail tunnel would be larger and cost far more than the $288 million water tunnel. To safely carry train traffic at speeds of 125 to 150 mph, two parallel tunnel bores about 30 feet (10 meters) in diameter would be needed, connected by cross-passages about every 1000 feet and with a handful of ventilation and emergency evacuation shafts to the surface.

How Much Would a Dumbarton Rail Tunnel Cost?

The costing of bored rail tunnels is reasonably predictable, with models having been developed for example by the High Speed 2 project in the United Kingdom. The HS2 tunnel cost model can be applied to estimate the known cost of the Dumbarton water tunnel, as a sanity check. The model uses 2011 British pounds, which we convert to dollars using the exchange rate of $1.57 in 2011. The length of the water tunnel is about 8000 m, and it took about 100 weeks to drive and clear out (100 m/week drive and 400 m/week clear-out). Tunnel construction cost is scaled by bore diameter as indicated by section 4.2 chart G.1; the single-bore water tunnel has 23% of the perimeter of a twin-bore 9.6 m tunnel considered in the HS2 document. Disposal cost is scaled by bore area; the single-bore water tunnel has 11% of the area of a twin-bore 9.6 m tunnel. Note the water tunnel does not require portal or ventilation / evacuation facilities.

Item	Description	Quantity	Unit	Rate	Cost ($M)
Purchase of TBM	EPB Boring Machine	1	ea.	$28M	28
Support Costs	Fixed Costs (EPB Machine)	1	ea.	$55M	55
	Time-related costs	100	weeks	$1.7M/week	170
Tunnel Construction	EPB Tunnel (single bore)	8000	m	$8000/m	64
Disposal of Material	Off-site disposal	8000	m	$800/m	6.4
TOTAL					323

The HS2 model seems to predict the direct construction cost of the existing Dumbarton water tunnel reasonably accurately, landing within ~12% of its actual cost. Most of that difference can be ascribed to the much smaller boring machine, which the HS2 model cannot account for; the Dumbarton TBM cost about $10M.

Scaling It up for Trains

The unit costs from the HS2 model can be used directly to scale up to a Dumbarton twin-bore tunnel ready for high-speed electric trains. This tunnel will be a bit longer than the water tunnel, since unlike water, trains can't just climb vertically into and out of the tunnel. Assuming 2025 dollars, which are worth about 20% less due to inflation, you get the following direct construction costs:

Item	Description	Quantity	Unit	Rate	Cost ($M)
Purchase of TBM	EPB Boring Machine	2	ea.	$35M	70
Support Costs	Fixed Costs (EPB Machine)	1	ea.	$69M	69
	Time-related costs	120	weeks	$2.1M/week	252
Tunnel Construction	EPB Tunnel (twin bore)	10000	m	$43000/m	430
Disposal of Material	Off-site disposal	10000	m	$9000/m	90
Tunnel Portals		2	ea.	$39M	78
Tunnel Shafts	Ventilation / Emergency	3	ea.	$39M	117
Systems	Electrical / Mechanical	10000	m	$8000/m	80
TOTAL					1186

The basic construction bill comes to $1.2 billion in year-of-expenditure dollars for a state-of-the-art twin-bore electric rail tunnel built in the middle of the next decade. This figure is then burdened roughly as follows:

• 3% environmental mitigation
• 25% contingency
• 6% engineering design
• 3% program management
• 4% construction management + 0.5% agency fee + 4% mobilization costs

These overhead rates compound with each other, combining to 53%. The expected all-up cost of a twin-bore Dumbarton tunnel is then about $1.8 billion.  Add to that the expense of removing the old bridge, estimated by Samtrans at $150M, and we reach almost $2 billion.

Why Tunnel?

As we are often reminded on the peninsula, a tunnel puts the trains out of sight and out of mind. In this case, it actually makes sense to build one because it crosses a terrain obstacle, San Francisco Bay. A new tunnel avoids visual and noise impacts, removes the blight of the old bridge, enables higher train speeds without endangering wildlife, and can be made more resilient to sea level rise than a new bridge. A new tunnel is not much more expensive than the options now being contemplated as part of the Samtrans Dumbarton Transportation Corridor Study, where it was summarily and improperly dismissed as too expensive, risky, burdensome and impactful (see Table 6-4). The tunnel option deserves a second and more serious look.

A Dumbarton tunnel could extend under University Ave and Willow Road in Menlo Park, grade separating both for a marginal cost that our model places at $132k per meter of twin tunnel (in 2025 dollars). The Samtrans study estimates each grade separation to cost about $200M (in 2017 dollars), so the two grade separations are worth about a mile of extra twin tunnel if you've already got TBMs in the ground. That's before the grade separations have to be rebuilt to accommodate sea level rise.

A Dumbarton tunnel would provide more cost certainty than a bridge. The last bridge the region built overran its cost estimates by several hundred percent, while the Dumbarton water tunnel was on time and on budget. Tunnel boring is a well-developed technology that is highly automated and doesn't use a lot of expensive construction labor. Some people are working on making it even more automated.

San Francisco to Tracy in 35 minutes

A Dumbarton tunnel could serve as a key component of a new regional rail link between the Bay Area and the Central Valley, putting San Jose much closer to Sacramento, and San Francisco under an hour from Stockton. It could eventually serve as the entry point of high-speed rail into the Bay Area, making faster trips from anywhere in the Bay Area to Sacramento and southern California. The performance simulation at right shows a high speed train passing through Tracy just 35 minutes after departing San Francisco Transbay, traveling along the Altamont SETEC alignment. This would vastly simplify the "blending" of Caltrain and high-speed rail since the latter would enter the peninsula rail corridor at its midpoint, sharing slow tracks for only half the distance of the existing plans and requiring fewer overtake maneuvers.

A new Altamont / Dumbarton high speed regional rail link could replace and combine the fragmented hodge-podge of projects and agencies variously pushing Altamont Commuter Express extensions, Valley Link, Livermore BART, a second BART Transbay Tube, the high-speed rail system, and whatever Cross Bay Transit Partners might come up with for Dumbarton, each of which nibble at different edges of the same basic problem: our regional mobility is inadequate and relentless traffic jams are crushing the souls of hundreds of thousands of people in the I-580, I-680, I-880, US-101 and CA-92 corridors.

The Dumbarton rail corridor needs to be thought of as so much more than a simple bay crossing that relieves traffic for people who work at Facebook. This is a one hundred year piece of infrastructure that can unclog an entire region, and it needs to be engineered for it. A tunnel for $2 billion (in 2025 dollars) is a sound and future-proof investment.

The U-Shaped Grade Separation

While some cities and towns on the peninsula are still holding out for trenches or tunnels to bury the railroad tracks out of sight, the astronomical cost and difficulty of constructing such structures below the water table in seismically unstable soils makes it likely that above-ground solutions will ultimately prevail, anywhere rail traffic needs to be separated from road traffic.  An attractive above-ground solution is the U-shaped grade separation.

What is a U-shaped grade separation?

U-shape bridge cross section, showing the benefits of
reduced track elevation

A U-shaped grade separation is a type of railroad bridge used to elevate the tracks above road traffic with as few community impacts as possible; there are no property takes and all road turning movements are preserved.  The bridge structure consists of sections made from two pre-stressed concrete side beams, forming the two sides of a U shape, connected by a flat slab forming the bottom of the U, on which the tracks are laid.  The side beams bear the bending loads from the weight of the bridge and the trains that it carries.  This is not a typical railroad bridge design; it is a specialized configuration used to quickly and efficiently build elevated urban metros in cities where these systems are being built from scratch in a densely built environment.  The concept is further explained in a paper and a patent.

While the peninsula rail corridor is not a new metro system, these U-shaped structures could still prove useful in a major push to grade-separate the 40 grade crossings that remain, enabling higher speeds and more train traffic while relieving road congestion and improving east-west access across the tracks.

What are the advantages of U-shaped grade separations?

U-shaped grade separations combine several attractive features that make them ideally suited for developed areas along the peninsula rail corridor, and certainly much better than the massive hollow core concrete box girder bridges considered standard issue by the HSR project as shown in the graphical comparison above.

• Lower track elevation.  The U shape minimizes the depth of the structure (measured from the underside of the bridge span to the top of the rails) to 3 feet or less.  This allows the standard 16-foot road clearance to be provided by raising the tracks just 19 feet above the road surface, about 8 feet less than the large elevated concrete box-girder viaducts that were proposed during the 2010 Analysis of Alternatives for peninsula HSR.  The rails are lowered thanks to the U shape, which places the structural support of the bridge to the sides, rather than under the trains.
   
• Lower visual impacts.  When the tracks don't need to rise as much, the rail approaches to a grade separation become correspondingly shorter and less obtrusive, impacting fewer views. The structures above rail level, such as overhead electrification poles, are also lowered.  This reduces the so-called "Berlin Wall" effect of a grade separation structure.
   
• Lower train noise.  The side beams function as natural sound walls, trapping rail noise before it has a chance to escape into adjacent neighborhoods.  They are especially effective because they are thick and quite close to the train.  This obviates the need to add sound walls on top of the bridge, making the finished structure less visually obtrusive.
   
• Better earthquake resistance.  The lower profile of the bridge structure reduces bending moments applied to the piers and foundations, whether by earthquake forces or train braking and acceleration or wind loads.  This makes the bridge piers less massive and integrates them better into the built environment.
   
• Better station integration.  Where stations must be located on an elevated section, structures are simplified thanks to the lower profile of the track, which reduces the reach of stairs, ramps, escalators or elevators, making for a more passenger-friendly environment.  The side beams of a U-shaped viaduct have their top flange at the same height as the train floor and form the actual platform interface, 50 inches above the rail and 72 inches from the track center line, allowing the U-shaped structure to continue uninterrupted through the station.
   
• Better safety in case of derailment.  The side beams are close to the train.  In case of a derailment, train cars will be guided by the structure and will not topple off the bridge.  This feature is known as "derailment containment."
   
• Lower construction cost.  U-shaped elements can be prefabricated off-site and assembled with minimal disruption compared to traditional cast-in-place construction methods.  Using standardized elements throughout the corridor, in dozens of locations, provides economies of scale.  The decreased profile changes for both rail and road (whether the U-shaped bridge is elevated or at-grade with the road sunk underneath) require less excavation or fill.

The U-shaped design can minimize property takes, preserve turning movements for cars and trucks, cost much less to build than below-grade solutions, and tread more lightly through built-up neighborhoods than a conventional (box beam) viaduct or split-grade separation.  U-shaped bridges are ideal for grade separation in dense areas like the peninsula.