Category: Blog

Four Things You Need to Know about Probe Drilling and Pre-Grouting

This blog is the first in a series called “Insights in Brief” that aims to boil down complex concepts into bite-sized facts and key points.

While probe drilling and pre-grouting have a long and successful history in drill and blast applications, their adoption for TBM technology has been more tenuous. Continuous probe drilling and pre-grouting was first pioneered in Norwegian hard rock D&B tunnels, where they have since been used with great success to detect ground conditions and consolidate weak rock ahead of the excavation face. If these methods have great potential to allow TBMs to excavate in difficult conditions, then there must be a knowledge gap. Here, we highlight four key things to know in order to get the most out of probe drilling and pre-grouting.

Number 1: There are always Pros and Cons


Much of the reluctance to adopt probing and grouting is based on a belief that the overall impact on the project schedule and TBM advance does not usually make up for the benefits provided. However, the benefits can be dramatic when compared to alternatives such as stuck TBMs, bypass tunnels, and other costly delays to the project schedule. The ability of a grout curtain to cut off or reduce water ingress and stabilize weak zones is unique to the method. This result has also been proven on hundreds of D&B projects over decades. When tunnel projects such as India’s Tapovan-Vishnugad Hydroelectric Project are considered, where a Double Shield TBM was brought to a halt following a massive influx of mud and water, the benefits seem clear.

There are other barriers towards industry acceptance besides time, however, and that is the perception of cost (both of course being related). In particular, in mountainous conditions or when tunneling downhill, probing may be the only practical approach towards risk mitigation, and pre-grouting may be the best possible option to control water inflows. When the cost of a stuck TBM is considered as the alternative, continuous probe drilling is looking pretty good.

Number 2: The Right Program and Machine Design can make all the Difference

Though the industry view of probing and pre-grouting tends toward the conservative, there are multiple ways to reduce impact to time and budgets while maximizing the benefits:

Plan and optimize the downtime for maintenance and cutter changes to minimize the downtime caused by probing and grouting
Proper scheduling may be one of the easiest ways to reduce downtime compared with current industry standards. To efficiently perform probe drilling and potentially pre-grouting in a TBM process, it is essential to plan the interventions and remove them from the critical path of the TBM process. Detailed planning should be done to coordinate the maintenance and cutter changing stops to the probing intervals. As an example a daily maintenance shift could be sufficient time to complete a grouting umbrella, with the correct TBM set up.

Analyze the drilling performance in detail
To get the most out of probe drilling and pre-grouting, detailed measurements of the advance rates of the probe drilling and the grouting pressure should be done. These measurements enable proper prediction of the ground ahead of the TBM. The drilling could be measured manually or automatically with Measurement While Drilling (MWD) systems, which are commonly used in D&B applications. The MWD system is used to analyze the rock in detail (hardness, water content, rock mass properties, etc.) and can be used to generate 3D-models of the rock mass in order to decide on the rock support or for documentation purposes.

Choose the right TBM Design
Ultimately, choosing the right TBM type can significantly cut time and cost. A customized machine, whether shielded or open-type, can be designed for accurate and continuous probe drilling. While it might seem that a shield machine would have limited drilling trajectories, machines like the Single Shield TBM for New York’s Delaware Aqueduct Repair offer 360-degree probe drilling paths using multiple drills, as well as probe drilling under pressure using down-the-hole hammers through ports sealed with ball joints. No matter what is needed, planning during the TBM design phase will most certainly cut downtime and costs later on.

Number 3: It has been Successful on Difficult TBM Projects

 

Though probe drilling and pre-grouting have not yet been used extensively on TBM projects, successful examples can be found worldwide. At Canada’s Seymour Capilano Water Filtration Tunnels, using two Robbins Main Beam TBMs, 100% probe drilling (with minimum overlap) and pre-excavation grouting were specified as part of the twin down drives of the Seymour Capilano tunnel project. This was due to the down gradient of the tunnel under high cover where there was a moderate risk of encountering significant inflows. Fortunately the actual groundwater inflows were much less than originally anticipated and so very limited pre-excavation grouting was required. Probe drilling was continuously carried out during TBM excavation, and while it had an impact on progress in the early days, once the crews became familiar with the equipment and procedures the work activity became efficient, and was successfully implemented with minimum impact to progress. Success stories like this are common in deep rock tunnels around the world.

Number 4: Knowledge Level is Key to Success

As with many developments in the tunneling industry, probe drilling and pre-grouting are seen from the view of risk sharing. Risk sharing could entail clearly defined specifications and payment provisions that allow for fair compensation to the contractor so they will not be reluctant to accept the approach, for example. Clear design and environmental criteria need to be established, so the execution of probe drilling and pre-excavation grouting involve the opinion of the contractor, the design engineer, and equipment supplier. In some cases, for example, the contractor may choose to accept moderate inflows that are manageable and do not impact excavation progress.

Training in the operations of probe drilling and pre-grouting will also necessarily lead to greater acceptance. While there is some training available at colleges that offer mining and tunneling degree programs, much of the training for such operations is necessarily hands-on and experience based. With an experienced workforce, the negatives of probe drilling and pre-grouting are greatly reduced. Such hands-on training is currently being provided by Robbins on several projects using a combination of classroom instruction and jobsite operation for crews who are not familiar with the methods.

Ultimately, the adoption of probe drilling and pre-grouting on TBMs is something that must be recognized as an overall benefit to the industry in difficult ground conditions. The technology is well developed in D&B tunneling, and it has been field-tested for decades. It is, in our opinion, the best method of accurately detecting and treating poor ground conditions in front of the TBM.


From Risk Aversion to Risk Reduction: How Elon Musk could usher in a New Era of Tunnel Boring

 

The factory acceptance of the Robbins TBM for the Rondout West Bypass on February 17, 2017.

Tunnel boring machines like the one here, for New York’s Delaware Aqueduct Repair, are turning risk aversion on its head.

It has been some time since I have written on the Robbins blog page, but I am inspired to do so by the announcement that Elon Musk is entering our business—the tunnel boring business.  It is great to see people with a vision of an improved world enter our industry.  I agree with Musk that the advance rate of tunnels can be significantly improved if development money comes into the industry.  Development money in tunneling, however, is at best minimal and is more often essentially nonexistent.  Nearly all tunnels are heavily specified to avoid risk taking by owners (therefore discouraging new development).  Nearly all tunnels go to the low bidder and low bidders try to buy the TBMs at the lowest price; a further discouragement of development. The industry has therefore been slow to improve advance rates, but with Musk bringing the issue into the spotlight, perhaps things will change.


Risk Aversion and How to Reverse it

There are some exceptions to this practice of risk aversion for new technology, and one is the Delaware Aqueduct Repair. This tunnel corrects heavy water leakage occurring from the 1940’s-built aqueduct tunnel for New York City.  We are just completing Factory Acceptance in our plant in Solon, Ohio of this unique Single Shield TBM.  The tunnel is at significant depth (approximately 300 m / 900 ft) with the distinct possibility of encountering very high water pressure (up to 30 bars).  The contractor JV of Kiewit/Shea have shown their willingness to move forward with several new developments for this project.  The concept of grouting off high water pressure as the primary means to allow advance in such conditions, rather than use an EPB or Slurry TBM, is in my view a significant step forward for our industry.  Granted there have been halfway attempts with a combination of grouting and pressurized tunneling at recent projects like the Arrowhead Tunnels and Lake Mead Intake No. 3, but these have come at high cost and sometimes long delays.  The Delaware Aqueduct TBM, by contrast, is designed to hold up to 30 bars of pressure while grouting occurs.   Boring and cutter changes are done in atmospheric pressure.

Chemical grouting and grouting technology in general have advanced multifold in recent years, and it is commendable to see it used extensively on several aspects of the Delaware Aqueduct Project. It’s a great example of what can be done when a contractor is willing to use new technology to address potential risks—it appears it can actually reduce risk in the long run.  It is a great honor to be working with the capable Kiewit/Shea JV team to be a part of advancing technology.

The enhanced probe drilling and grouting capabilities as seen in trajectories (orange and red) on the Rondout TBM 3D model.

The enhanced probe drilling and grouting capabilities as seen in trajectories (orange and red) on the Delaware Aqueduct TBM 3D model.

Areas Ripe for Change

The Delaware Aqueduct Repair project is a flagship project for what I hope will become more common in the industry: instead of low bidding with the cheapest possible machine, offering a reasonable bid with a specialized TBM that has a higher initial investment, but ultimately a lower cost overall. The project’s use of technology is wide-reaching, particularly atmospheric cutter changes and chemical grouting, which have the potential to reduce downtime and increase safety. I do not see the future of rock tunneling under high water pressure being left to divers to change cutters and repair the cutterhead.  We all know it is not cost effective to send divers to work in confined spaces over 10 bars.  It should be noted that the long-duration Hallandsås Tunnel, for example, finished the majority of its TBM advance by relying on effectively this technique of grouting and advance after failing with a Slurry System.  There are lots of tunnels to be built with above 10 bars pressure that will use this technology.  The industry needs to automate cutter and bit changes as much as possible, and increase the integration of chemical grouting in tunneling.

Project officials examine the cutterhead and cutters of the Rondout TBM. The machine can bore and cutters can be changed at atmospheric pressure.

Niels Kofoed and Danny Smith of contractor Kiewit examine the cutterhead and cutters of the Delaware Aqueduct TBM. The machine can bore and cutters can be changed at atmospheric pressure.

Certainly there are many areas for advancement in our industry, and major public figures like Musk drawing attention to it is ultimately a good thing.  After all, getting the general public to think about solving traffic by going underground is no easy feat. Even more so, getting the tunneling industry to think about its own risk-averse practices has a big potential benefit. Hopefully all of this attention will result in more tunnels, more business, and better infrastructure. Musk’s willingness to take a risk aimed at making the underground construction industry potentially faster and more stable is a good bet to take.


The Brenner Base Tunnel: A European Core Project

 

Figure 1. The Trans-European Network for Transport (TEN-T) aims to connect all European member nations from West to East and and North to South.

Figure 1. The Trans-European Network for Transport (TEN-T) aims to connect all European member nations from West to East and and North to South.

Tunneling is a worldwide business with often-changing markets. At the moment, everybody is watching the markets in Asia and in particular various huge projects in China and India, as well as the Middle East. With these busy hot spots, it’s easy to overlook projects elsewhere.

In this blog, I want to refocus and take a look at Europe, where there are some very interesting and challenging mega-projects underway for the Trans-European Network for Transport (TEN-T) of the European Union. The TEN-T connects all economies in the European Member Countries from West to East and North to South (Figure 1). This master plan for connectivity in Europe includes nine core network corridors with several projects crossing the borders of multiple European countries. The cross-border project implementation is complicated because of the different technical, financial and statutory requirements.

TEN-T core network projects

The core projects of the TEN-T master plan all serve as missing links that would connect the European Member Countries, like the Koralm and Semmering Railway Tunnels (both in Austria), Lyon-Turin Railway Project (connecting France and Italy), Fehmarn Belt Crossing (connecting Denmark and Germany), Brenner Base Tunnel (connecting Austria and Italy), Ceneri Base Tunnel (connecting Switzerland and Italy) and also some completed projects like the Oresund Bridge, Tunnel Road and Rail Fixed Link (connecting Sweden and Denmark), Milano-Roma-Napoli Railway (Italy), Gotthard and Lötschberg Base Tunnels (Switzerland), Betuwelijn Railroad (connecting the Netherlands and Germany) and the Channel Tunnel (connecting United Kingdom and France).

Financial support from the European Union in an amount estimated at 500 billion euro is required to complete this Trans-European Network and to widen some of the bottlenecks within it. The Brenner Base Tunnel is one of the most interesting cross-border projects and a core project of the TEN-T master plan (Figure 2).

Figure 2. Layout of the Brenner Base Tunnel construction.

Figure 2. Layout of the Brenner Base Tunnel construction.


Brenner Tunnel Conversations

The Brenner Base Tunnel (BBT) is a big challenge for all involved parties. In 2015, I had the great opportunity to interview Prof. Konrad Bergmeister, who has been the CEO of the BBT SE since August 2006 (Figure 3). Bergmeister was previously the technical director and head engineer of the company managing the Brenner Highway and was responsible for the planning and construction of new infrastructure and for maintenance of the existing structures. For the past 22 years, he has taught construction engineering at the University of Natural Resources and Applied Life Sciences in Vienna (Austria). He has been the President of the Free University in Bolzano (Italy) since 2010.

Figure 3. Professor Konrad Bergmeister, the CEO of BBT SE since 2006.

Figure 3. Professor Konrad Bergmeister, the CEO of BBT SE since 2006.


Interview with Prof. Bergmeister

Could you give me a brief overview of the Brenner Base Tunnel?

The Brenner Base Tunnel is a ground-breaking engineering project for the 21st century. This underground structure has a total length of 64 km and consists of three tubes: the exploratory tunnel and two main tubes with four lateral access tunnels connecting them together (Figure 4). The tunnel itself will become the longest railway tunnel in the world once complete.

The history of the tunnel is a long one: 160 years ago, an Italian engineer came up with the idea to go beneath the Brenner Pass. After World War Two, the project was reassessed but never proceeded. Finally, between 1987 and 1989 a feasibility study was carried out. The preliminary project was approved in 2002, and between 2005 and 2008 project details were worked out. In 2009 the environmental and technical approvals were obtained in Austria and in Italy. So we started with the first exploration of the whole rock situation in 2006, drilling vertical bore holes that totalled more than 28 km when we sum it all up. And this preliminary information was used in order to study the final layout of the tunnel in order to do the definitive design.

Figure 4. The 64 km long Brenner Base Tunnel consists of three tubes: An exploratory bore and two main tubes connected by access tunnels.

Figure 4. The 64 km long Brenner Base Tunnel consists of three tubes: An exploratory bore and two main tubes connected by access tunnels.

What, for an engineer, is the most challenging aspect of the Brenner Base Tunnel?

The most challenging issues for me are the following:

First of all we developed the so-called design guide in order to have the right basis to execute the design in both countries. This design guide was based on some new design ideas taking into account all the safety issues that have been proposed with the Eurocodes on a European level.

Second we developed internally a so-called chance and risk analysis, which should allow us to monitor the development of the project in terms of possible chances and risks. How we are doing that? Well we are trying to evaluate and double check the actual ongoing construction with our project managers and external experts and we are trying to identify all the possible risks and chances that might occur as tunneling proceeds.  This analysis is part of a database that will be actualized on a yearly basis so we have additional information in terms of possible risks, additional costs, cost savings and scheduling.

The third issue is something that deals with some novel forecast technologies. We are using digital mapping and photogrammetric mapping as forecasting methods, particularly for the ongoing drill and blast operations. This is called the Tunnel Control System and is able to predict complex excavation shapes by using statistics regression analysis. It is based on 3D point clouds of the rock surfaces captured after each excavation, and the precision of previous excavated profiles is also analysed. The previous blasting data and the corresponding geological information are used for the prediction of the upcoming upper and lower blast profiles. For the forecast a certain number (minimum five previous blasts) is taken into account for a linear or nonlinear regression analysis. Through this optimization procedure up to 65% reduction in over-break has been achieved.

Figure 5. Construction on the Brenner Base Tunnel is currently underway.

Figure 5. Construction on the Brenner Base Tunnel is currently underway.

And the last issue is actually that we have been trying to develop ideas for the reuse of excavation material. The concrete mixture must be sustainable for the next 200 years since this is the lifetime of the tunnel.  We have been studying the material of the exploratory tunnel (Figure 6), especially the schists, in the central zone of the project and we were able to modify the preparation methodology and optimize the concrete mixture to re-utilize 100% of the excavation material.  Five years ago, all of the geologists and specialists during the approval phase told us that the excavation material must be disposed of. So this is actually a real step forward into optimizing the project excavation.

Figure 6. The completed exploratory bore for the Brenner Base Tunnel.

Figure 6. The completed exploratory bore for the Brenner Base Tunnel.

What is your opinion about the on-site TBM assembly of Robbins compared with the re-assembly of factory-built machines on jobsites?

From an engineering point of view we are only interested that the machine works very well on site. So we are interested to see, when the machine really starts, the performance in a certain excavation length. We are interested in the results and not so much on the specific assembly situation. There are different trade-offs: On the one hand, if you pre-assemble the machine in the production facility, this can guarantee you certain tolerances and probably certain pre-operation errors can be adjusted and finally avoided. But, the major problem is that you have to transport the semi-assembled machine on site and you have to re-assemble the machine on site again and then you have to start excavation. However, with Robbins for example, they can bring all the individual pieces on site and very often they are adjusting the machine itself directly under site conditions. It is easier, I think, to do the adjustment on site directly for specific logistics reasons. We can say that you might have more flexibility if you assemble directly on site compared with doing the assembly at the production facility.


Beyond Boring: A Journalist's Fascination with Tunnelling

About the Guest Author: Roland Herr has a background in civil engineering and is an international freelancing journalist. He has over 20 years of experience on engineering and construction projects all over the world, and is especially interested in tunneling.


Those working in tunnelling understand that this is an industry more fascinating than any other. What is it about tunnelling that makes it so exciting to those in the field?

Curious to know more, I discussed this question with some very experienced European tunnelling specialists: Frode Nilsen (Norway), Managing Director of LNS, and Dr.-techn. Klaus Rieker (Germany), Managing Director Tunnelling Division of Wayss & Freytag Ingenieurbau AG. Both conversations took place at different places and times, but with strikingly similar results.

Dr.-techn. Klaus Rieker and Frode Nilsen took time to share their experiences in the tunnelling industry.

Dr.-techn. Klaus Rieker and Frode Nilsen took time to share their experiences in the tunnelling industry.

Frode and Klaus both have extensive backgrounds in the underground industry. Frode has been working with tunnels since he left university, the Norwegian Institute of Technology, in 1988, and Klaus has been building tunnels for 25 years. Comparatively, I am a “youngster” with 14 years of experience with tunnels and the tunnelling industry, but no less enthusiastic.

Read on for the results of my Q&A sessions with Frode and Klaus:

One characteristic shared by most tunnellers is that they work internationally, on many different projects with varying levels of responsibility. Tell me about your international experience.

Klaus: [At Wayss & Freytag] I was assigned to different projects in Singapore, Malaysia and Taiwan. As a young engineer working in Asia, it was very hard to gain acceptance, particularly because in the Asian culture, older people are typically responsible for project management. It was difficult to convince the contractor that I could handle it, but step-by-step I proved myself with my performance and knowledge. I remember with pleasure my time on a metro project in Singapore; altogether we had about 30 nations involved on the project. It was really amazing!

Frode: Our most impressive project [at LNS] was SILA for the Iron Ore company LKAB. We blasted 12 silos out of the rock and built a 600 m long unloading hall and a 2.8 km tunnel for iron transport from the silos to the harbour. Our most famous project was the Svalbard Global Seed Vault in Spitsbergen for the UN, where we built tunnels and 3 rock caverns in the permafrost with an even temperature of -18° Celsius to store samples of the world’s seeds.

For Frode, the timeline and longevity of underground projects is also an amazing feat worthy of note—tunnels can be built in difficult ground conditions over a period of years, but the hard work pays off in that many tunnels have a design life of 100 years or more.

Working in tunnelling also provides a unique perspective on emerging markets. Which countries or markets are currently experiencing rapid development when it comes to tunnel construction?

Frode: In Europe, Norway is one of the most interesting nations, especially for drill & blast, with hard competition and low prices. In Asia, China is on top, and South America is also growing, in particular with the mining industry in Chile. Much of the future of tunnelling lies in mining: studies show that in 2034 around 60% of mining will be done in underground mines. That means tunnels for access, ore haulage, and more.

Klaus: Germany is now no longer really a market for tunnelling, and in Central Europe tunnel construction is declining. Meanwhile, Asia is the growing market. In Singapore for example, 10 to 20 machines are running annually for the metro system extension. China and India are also huge markets right now. I find North America to also be an interesting market with many current and upcoming projects.

Every industry has its own set of challenges. What do you find most challenging about working in the tunnelling industry specifically?

Klaus: A defining characteristic of tunnellers is that we love a challenge. We thrive on new, very difficult situations that demand utilization of all our knowledge and problem-solving skills, in order to find the best technical solution.

Frode: Client demands can be challenging, and are often accompanied by environmental and technical limitations as well as financial constraints.I am happiest when projects are profitable and everybody involved is satisfied.

Frode and Klaus’ comments on their experiences led me to one overarching conclusion: engineers working in tunnelling are some of the world’s brightest and most experienced, with shared passions for overcoming difficult situations and ever-expanding their world views. For adaptable and driven engineers, the tunnelling industry offers a challenging yet rewarding career with job security, as projects and new markets continue to emerge globally.


The Light at the End of the Tunnel: The Positive Side of Seattle’s SR99 Project

Robbins Bertha Blog

Bertha ship docks at the Port of Seattle. Photo cred: WSDOT.

Seattle is the founding city of The Robbins Company, and a place where I lived for nearly 15 years and commuted on SR99 while working at Robbins early in my career. As such, the new SR99 Viaduct Replacement Tunnel Project is of great interest to me.

The industry is all too familiar with Seattle’s SR99 Tunnel and its TBM, known as “Big Bertha”. More specifically, much has been written with regards to the TBM needing repairs after about 300 m of boring. The TBM is the world’s current largest at 17.5 m in diameter, and is excavating a 2.7 km long drive.

Robbins Bertha Blog

Bertha’s parts parked on Alaskan Way. Photo cred: WSDOT.

Robbins Bertha Blog

Last day above ground for Bertha’s cutterhead. Photo cred: WSDOT.

TBM Tendering

Robbins was a relatively new entry into the EPB/soft ground tunneling business when tenders were called for the latest SR99 project in 2011, and we made a concerted effort to get the order for this particular TBM. We teamed up with Japanese TBM manufacturer Mitsubishi Heavy Industries (MHI) to get the order. Robbins has had an association with MHI for more than 20 years, with jointly-designed machines operating around the world on projects in India, China, the U.S., and more. MHI has built over 1,000 EPB machines and in my opinion, the Japanese TBM manufacturers are further advanced in EPB technology than their European and American counterparts.

Through the process of trying to receive this order, we learned a lot about the geology, as well as the contractors’ and TBM’s specification requirements. The contractor Dragados, one of the JV partners and very well-experienced in soft ground tunneling technology, developed a high-level specification for the TBM suppliers. All of the prospective TBM suppliers were required to quote and if successful, supply to this standard. We eventually stepped out of the tendering process to supply this TBM, as the lower prices and greater assumption of contract risk offered by our competitors made the TBM supply an impractical business option for us.

Robbins Bertha Blog

Bertha’s parking spot. Photo cred: WSDOT.

Tough Tunneling

The current situation at the SR99 project is more positive than media tend to paint it. The project design consultant did a commendable job on laying out the tunnel route and building in a contingency plan. Boring through glacial till, even with modern TBMs, is never an easy task as previous projects like the Brightwater Conveyance Tunnels have taught the city of Seattle. This is doubly so along the Seattle waterfront, which includes manmade fill, utilities, and buried refuse. In such ground, TBMs can encounter rapidly changing geology; pockets of groundwater; abrasive soil; and manmade objects such as unmapped disused pipes; foundation piles; etc.

Robbins Bertha Blog

Survey says, “This is one big tunnel.” Photo cred: WSDOT.

Aware of the problems that can develop while using an EPB TBM in glacial till under a city with a lot of backfill, the SR99 designer wisely developed a contingency plan. The strategy, in addition to pre-planned safe havens, involved a “shake down” stretch of tunnel, which ran under no buildings. If problems did occur repairs to the TBM could be made by sinking a surface access shaft at this location. Unfortunately the need for that repair event occurred shortly after the machine commenced excavation.

Why there were failures of the cutterhead seals, and potentially the cutterhead main bearing, is yet to be determined. I doubt there will be any signs of failure of the main bearing when the crews get to inspect it. However, all parties involved are wisely taking precautions and installing a new main bearing in addition to the seals.

Bertha’s Lessons

The Seattle Tunnel Partners and WSDOT have in place a panel of experts to advise them on the highly technical details of the TBM design. I personally know several of these experts and they are well qualified to recommend and supervise the necessary repairs and procedures to get the TBM into a condition where it is able to finish this tunnel.

Robbins Bertha Blog

The experts behind the world’s largest TBM. Photo cred: WSDOT.

Having been in the TBM supply business for quite a few years, I unfortunately have to admit having been in a similar (fortunately not as well published) situation as the TBM supplier on more than one occasion. This situation–significant TBM problems at the beginning of boring—can result from many different factors and is not unique to the SR99 project. In fact, Robbins recently had a similar situation (admittedly on a smaller scale in terms of both public and financial impact) on a project in Turkey known as the Kargi HEPP. Despite extensive pre-planning, unexpected ground was encountered, which resulted in several in-tunnel stops and machine modifications in the first few hundred meters of the tunnel. What happens in these situations is you pull in the best minds with the most experience and immediately analyze the problem. The ultimate fix often ends up as a multi-level solution. You must ensure you have the problem under control, plus take additional measures to monitor the vulnerable components and operating procedures. At Kargi, this process resulted in the remainder of the project being finished without significant TBM problems. Without a doubt a similar process is going on at SR99 with Hitachi Zosen engineers, the contractor’s specialists, and the city’s board of experts.

Being one who is keenly interested in this project, I believe that this TBM will soon be back to boring with a new completion date, which will be fulfilled. I am optimistic that this project will one day be seen as a positive in the tunneling industry, where many lessons were learned and advancements were made. Such advancements will be put to use in Seattle and in other cities that greatly benefit from the excavation of more underground infrastructure.


A Tradition of Innovation: The 2013 Muir Wood Lecture takes a cue from Robbins’ Long History

Dick Robbins and Lok Home


Robbins current president Lok Home (left) with Robbins former president Dick Robbins (right).

When asked about his most memorable tunneling project, Dick Robbins narrowed it down to two: The Channel Tunnel and the Paris RER Metro. The former company president and CEO from 1958 to 1993 has seen hundreds of tunneling projects in his career, and should know.  The Channel Tunnel, with its hybrid machines capable of operating under 10 bar water pressure, was challenging to say the least.  But the Paris RER Metro in 1964 resulted in a radically unique machine design: “We created the world’s first below-water, pressure bulkhead shielded machine using air pressure. All future slurry and EPB designs had their genesis in this machine,” said Robbins. A sealing system using steel fingers back-supported with foam kept the gap between the machine shield and segments airtight.  Wire brush seals with grease were not developed until later projects (see below).

Paris RER Metro

The central section of the Robbins machine at the Paris RER metro, with the Arc de Triomphe in the background.

These two projects are just a few of the highlights Dick Robbins is set to touch on during his 2013 Sir Alan Muir Wood Lecture, honoring the late tunneling statesman who initiated and served as the first president of the International Tunneling Association (ITA).

The talk, titled “A Tradition of Innovation: The Next Push for Machine Tunneling” will cover everything from the beginnings of mechanized tunneling to the era of modern tunneling when his father James S. Robbins came up with the idea of developing full-face TBMs (see picture below).  Discussion will then move to modern-day marvels like the world’s largest TBM set to bore the Highway 99 Viaduct Replacement tunnel.  Robbins will make the case that a culture of innovation is needed in greater force in order to push for new leaps in design that will accelerate the advancement of the industry.

James Robbins at the Humber River TBM launch, 1956

James S. Robbins (in driver’s seat), Robbins founder, at the launch of the Humber River Sewer TBM in 1956. The machine was the first ever to exclusively use rolling disc cutters.

See the Talk:

ITA-AITES World Tunnel Congress
Geneva, Switzerland
Opening Ceremony & Sir Alan Muir Wood Lecture
Monday June 3
9:00 AM to 10:30 AM

For more information on Robbins’ long history, check out the lecture Dick Robbins and colleagues made when he received the 2009 Benjamin Franklin Medal.


Salamanders, Pseudo Scorpions, and Quartz Crystals: How my Recent Site Visit proved that TBM Tunneling is the Greenest Way to Go

View from the bottom of a deep shaft at the Jollyville Transmission Main.

The Balcones Canyonlands just north of Austin, Texas, USA is a protected wildlife preserve, and it’s not open to the public.  So when the city of Austin opted to build a 10.5 km (6.5 mi) long water line directly below it, there was understandably some concern—but not for humans. The inhabitants of the Canyonlands include some of the state’s most endangered species, from tiny, blind cave spiders to songbirds to the green-speckled Jollyville Plateau Salamander.  And don’t forget the pseudo scorpions.   The Jollyville Transmission Main, a pipeline planned to bring drinking water to the drought-ridden city, was designed deep below protected aquifers in chalk, up to 106 m (350 ft) down in limestone rock.  This made tunneling the only option.  But even so, how could the project avoid impacting such a sensitive environment?

When I visited the site in Autumn 2012, I got my answer. The contractor, Southland/Mole JV, is taking every precaution to mitigate impact, and they’ve been very successful thus far.  An environmental consultant from the city is on the site daily, and routine inspections ensure that the minimally invasive tunnel is not encroaching on the habitat of the endangered animals.

Our guides for the visit, Kent Vest and John Arciszewski of Southland Contracting, took us to the 82 m (270 ft) deep Four Points Shaft first, which has been partially reinforced with liner plates.  Kent and John explained that during excavation, water inflow from the aquifer had been high enough that the city opted to grout behind the liner plates to prevent further dewatering.  Gravel in the annular space between the liner plates and shaft walls would keep any groundwater pathways intact.

As we descended into the unlined tunnel where a 3.25 m (10.7 ft) Robbins Main Beam TBM was averaging 55 m (180 ft) per day, we talked ground support—or the lack thereof.  Three TBMs are being used to excavate portions of the tunnel in competent limestone.  Southland is not permitted to do either pre-excavation drilling or grouting because of the possibility of karst cavities and groundwater pathways—areas where endangered aquatic species might live.  While they plan to install wire mesh and rock bolts if it’s needed, the rock quality has so far been very good with little ground water.  We took a few photos while in this tunnel (see below), and then moved on to the next site.

The Southland crew in the tunnel.

The unlined tunnel.

Our last site visit of the day was the deepest—the 106 m (350 ft) Jollyville shaft next to the similarly named Jollyville Reservoir in a much more urban location.   Once we’d been lowered down the shaft, we found a small, unlined tunnel in competent limestone.  A 3.0 m (9.8 ft), contractor-owned Double Shield TBM was tunneling this reach, after having been refurbished by Robbins in Solon, Ohio.  Similarly, the machine was getting some fast advance rates of 46 m (150 ft) per day on average.

The TBM operator in the small tunnel sits next to the machine conveyor.

What I immediately noticed in this tunnel was the multitude of small, mostly dry karst cavities down the tunnel walls.  These cavities could potentially be home to the blind cave spiders, though none had been found during tunneling and it was likely they wouldn’t live in such small voids.  We noticed, during our ride on the muck train towards the machine, sparks of light emitting from these cavities.  Once we stopped John reached into a cavity and pulled out a handful of quartz crystals.  “These are all over, in all these cavities.  You can take some with you,” he said.  As I am part-pirate (my genealogy traces back to Sir Francis Drake on my mother’s side!), I decided to stuff my pockets with the sparkly crystals (i.e., treasure!).  I had never seen anything like this before, but John explained that the minerals in the perched water in many of the pockets caused the crystals to grow.  Since the pockets were small, they weren’t filled in or isolated and we could pluck quartz crystals to our heart’s content.

Shining a light on the tiny cavities.

Quartz crystals!

On a more serious note, Southland does have a plan of action if large cavities are found or if a groundwater pathway is very open and linked to the aquifer.  In this case, large voids would be isolated and sealed off to protect the habitat within.  If ground water inflows are severe they will install steel liner plates and grout behind them to stop the flow.  But, says Southland, they don’t expect to encounter either of these since the tunnels are so far below the aquifer.  In fact, one reach of the tunnel, already complete at the time of our visit, had encountered almost no groundwater in 1,300 m (4,400 ft) of tunneling.

Once back on the surface, it became clear to me that this well-designed project proved that tunneling, particularly TBM tunneling, could be used safely in even the most sensitive environments.  The foresight, planning, and execution by the designers and contractors was impressive.  The salamanders and pseudo scorpions thank you.


What is WIT, and Why Does it Matter?

“If going underground suits you, you are immediately hooked”; “Once I was exposed to the underground industry, I loved it”; “I fell in love with tunnel construction, and never left”.  All of these statements came straight from women working in tunneling who were interviewed by TunnelTalk at NAT 2012. If tunneling is such a satisfying career path for women, why are so few females working in tunneling?

The lack of women may be attributed to lack of industry exposure and the male centricity of the field, Since its establishment, tunneling and underground construction has been primarily male-dominated. In recent years, the number of lady tunnelers has grown, and the need arose for a group to support this demographic. Women in Tunneling (WIT) was created by women for women with the purpose of providing networking opportunities to women from all corners of the tunneling world, and spreading the message of the exciting opportunities that accompany a career in the field.

The inaugural WIT networking event was hosted in conjunction with NAT 2012 in Indianapolis, IN, and took place at a popular Indy wine bar. Architects, consultants, editors, engineers, marketers, and writers were among the 27 attendees. Highlights of the two-hour event included a constructive roundtable discussion and a raffle with sponsor-supplied gifts.

Women in Tunneling's First Event

A lively discussion at WIT’s first event.

All guests were excited about the future of the group, and eager to get additional women involved. The hope is to spread the word about WIT, and double the amount of attendees at the next event. Eventually, WIT would like to have events during all major North American trade shows. Interest internationally has been shown as well, and WIT looks forward to possibly expanding overseas.

WIT is not affiliated with any one company; it is an industry-supported group that aspires to grow the number of women in tunneling through networking and increased industry exposure. The group’s first event was hosted by The Robbins Company, and was entirely paid for by the generosity of sponsors Kiewit, Jacobs Associates, Arup and Bradshaw Construction Corporation.

Sponsor gifts at the event.

Sponsors provided giveaways for all attendees, and larger gifts for a raffle.

As Natasha Taylor, one of the TunnelTalk interviewees and a civil engineer at Kiewit, said, “There are all the opportunities in the world [for women in the underground industry]”. Our market is thriving and there are countless possibilities for women who want a career in a challenging and dynamic business. We hope you’ll join us in supporting WIT, and the group’s goals of bringing women together and attracting additional women to the industry.

If you’d like to get involved with WIT and receive group updates, please join our LinkedIn group. To watch the videos referenced in this blog, visit the TunnelTalk YouTube channel.


Onsite First Time Assembly Works: Debunking the Most Common Myths


I have to admit, that the first time I gave much thought to Onsite First Time Assembly (OFTA) for new machines was following a dinner conversation with a very experienced engineer from one of the large Italian underground contractors.   The engineer suggested that it was his opinion that on large diameter machines, perhaps above 8 m or so, that much time and money could be saved by an OFTA program, which would allow the machine to be initially assembled on location.  He said he did not believe the huge amount of labor expended to completely assemble a TBM in the shop, which then had to be repeated in the field, could be justified.  He argued that labor was being duplicated and the result was a longer delivery period that was reasonably required.  This conversation, taking place in the mid-nineties, is what first triggered my thinking on the subject.  Well, that conversation and couple of glasses of Brunello di Montalcino!  My engineering friend raised a very valid point and I’ve given the subject much thought since, and discussed OFTA with many people in the industry.   It appears to me that, even though the method has been successfully used on many of our projects worldwide, there are a few “myths” that have gained traction regarding the risks of OFTA.  I’ll address two of these OFTA myths.

 

Myth No. 1 – It will be a disaster if the parts don’t fit together on the job site!  That is why a full factory assembly is required.

 

This myth doesn’t take into account three factors:

1.  Partial assembly: Major sub-assemblies are pre-assembled in the factory.   The main bearing and seal assembly, for example, is fully factory assembled.  It is only the major parts that may not be pre-assembled.  However, in many cases, we pre-fit the pieces; forward shield to outer telescopic shield, outer to inner telescopic, inner telescopic to gripper shield, and so on for a double shield machine.   So the part fit-up is checked but the entire machine is not put together in the factory.

Ensuring fit up of components

Major components are checked in the factory to ensure fit up.

2.  Modern measurement devices:  In those cases where it is not possible to pre-fit two pieces in the factory, we can use modern Coordinate Measuring Machines (CMMs) or “Laser Trackers” to take precise measurements of both pieces to insure fit up when they meet in the field.

Using a Coordinate Measuring Machine

A Robbins employee uses a CMM device in the Ohio manufacturing facility.

3.  In-field repairs:  When an offshore oil rig has a component failure do they disassemble it and take it to the mainland for repairs?  When repairs are required on hydroelectric turbines and generators, do they always take the big parts to a machine shop to repair?  No, they do not.  Many repairs of large scale equipment are made in situ, wherever the plant is located.  If it is discovered at the job site that a component has been mis-machined / manufactured it is most likely a minor error (remember the CMM measurements and component fit-ups in factory partial assembly) and repair can be effected on the piece in place at the job site.  In Robbins experience, this has always been the case and such repairs have been carried out when discovered on site and without impact to final startup schedule.

 

Myth No. 2 – The labor cost on an underground job site is far higher than labor cost in a factory.  It will cost far more money and time to assemble the machine on site for the first time.

 

OFTA Myth No. 2 leads to a wrong conclusion regarding cost, and fails to examine fully the potential benefits.

1.  Cost: This above statement is generally true; however, it does not necessarily follow from this statement that money will be saved by having a factory assembly plus a job site assembly.  Robbins history with in-factory and OFTA assembly reveals the following:

Traditional Factory Assembly

  • Full factory assembly hours:  X hours
  • On-site assembly of a fully factory assembled machine: 0.5X hours

OFTA Method

  • Partial factory assembly for OFTA delivery: 0.5X hours
  • OFTA site assembly of a partial factory assembled machine: 0.7X hours

Where the value of X is dependent upon the size and type of TBM as well as the complexity of the backup system.

If we assume that the cost of labor on the job site is twice the cost in the factory, then we can use $100/ hour for the job site and $50 / hour for the factory.  The total cost for the two methods is then:

  • Traditional method cost = X hours ($50/hour) + 0.5X hours ($100/hour) = $100X
  • OFTA method cost = 0.5X hours ($50/hour) + 0.7X hours ($100/hour) = $95X

In short, the total costs are nearly the same, or perhaps with some savings in favor of the OFTA method.

2.  Schedule: Another flaw with Myth No. 2 is that it does not consider a large potential benefit: the savings in schedule possible with the OFTA method.  By not completely assembling the TBM in the factory, it is possible to deliver a working TBM at the job site one to two and a half months earlier than with a traditional full-factory assembly and delivery.  This is a significant savings for most projects, when the site assembly can be done at this early stage.

Niagara cutterhead assembly

OFTA for the 14.4 m diameter Niagara TBM was completed in four months, saving an estimated four to five months on the delivery schedule.

3.  Training of site personnel Another potential benefit that Myth No. 2 does not address is that of training.  The contractor’s site personnel who are involved with OFTA assembly and testing get far more training due to the additional hours spent on the assembly and testing, and the larger Robbins crew present to assist and advise.  Robbins’ experience indicates that contractors who opt for OFTA deliveries are frequently capable of taking over the full operation and maintenance of their new TBM much quicker than contractors who opt for a traditional delivery.   This is due to the much deeper knowledge the contractor’s personnel gain during the OFTA assembly and testing.

OFTA in India

Site personnel take part in the assembly of a Double Shield TBM in India.

In summary, the question to be asked when making the decision to use OFTA or go for a traditional factory assembly is: What are the potential risks and what are the potential rewards?  One must examine all potentials of the OFTA scenario, pros and cons, to come to the correct solution.   I’m not claiming that an OFTA scenario is correct for every project.   For example, if the start of boring of the tunnel is not on the critical path for the project and the TBM is a smaller diameter unit, it might be advisable to allow a full factory assembly. That way, when the job site is finally ready for the machine, it can be assembled a bit quicker on site.  Again, if the start of boring is not on the critical path and the labor cost difference between job site and factory is larger (e.g., job site is in Finland, TBM factory is in China), then it could be that a full factory assembly can be justified on a cost only basis.  However, in nearly every case when the start of boring the tunnel is on the critical path, then the faster delivery possible by OFTA is clearly favorable.

The biggest impediment to more widespread use of OFTA is limited thinking: looking at the potential risks without looking at the potential rewards.  Tunneling itself is fraught with risk, yet contractors take on jobs everyday due to the potential rewards.  OFTA is deserving of a similar analysis.

 

About the Author

Joe RobyJoe Roby (B.S., Mechanical Engineering, University of Washington) has worked in the tunneling industry for more than 20 years. He started at The Robbins Company as a stress analyst specializing in finite element analysis of complex structures. Subsequently he was a member of the 19-inch cutter development team. For five years he was managing director of Robbins refurbished and leased TBM division. He has authored many technical papers for conferences and industry publications on subjects ranging from cutters to TBM assembly and rebuilding practices. Today he serves as Robbins’ Vice President – Production & Logistics


There are Urgent Projects…and Then There’s Emisor Oriente

After visiting Mexico City’s Emisor Oriente Wastewater Tunnel, I realized something: there are urgent projects, and then there are URGENT PROJECTS.  Túnel Emisor Oriente, often abbreviated to TEO by those involved, is the latter.  We visited the site in 2011 to see the assembly of an EPB and learn about why the project is so important.

Day 1

On a good day with light traffic, the jobsite is about an hour’s drive away from the Distrito Federal, the downtown zone of Mexico’s capital city.  Our first day, I noticed how the high rise buildings and restaurants slowly dissolved into ramshackle huts as we drove further from the city to an area known as Ecatepec.  Approaching the site, we crossed a bridge in our SUV that spanned an extremely slow moving grayish brown river (more about this soon).

The Gran Canal

The “river” flowing outside Mexico City.

It was a warm day in June, Mexico’s rainy season, which is quite different from the rain in my home town of Seattle in the U.S.  Each day during the rainy season, the morning dawns sunny and warm–but by 4:00 in the afternoon a torrential downpour begins.  The water floods city streets throughout Mexico City, whose storm drains can’t handle the sudden inundation.  Sometimes the rain only lasts a few minutes, and sometimes it goes for longer.  The water eventually runs into rivers like the one we crossed by the jobsite, creating flooding risks.

We exited our SUV at the Lot 1 shaft and were greeted by several Robbins Field Service guys, including our Field Service Manager for the Americas, Jeremy Pinkham.  I was excited to learn more about the TEO project, where we have three EPB machines among six TBMs that are excavating an epic 62 km (39 mi) long wastewater tunnel. The tunnel will feed into the country’s largest water treatment plant, which is currently being built.

Emisor Oriente Site

The morning of the first day, at the Lot 1 Emisor Oriente site.

As Jeremy and the group walked towards the shaft to be lowered down the elevator, I was struck by a smell—something akin to a vast field of poorly maintained port-a-potties.  I asked Jeremy about the Robbins machine, which was originally intended for Lot 5 but had been fast tracked to bore part of the tunnel section at Lot 1.  I was wondering why this particular section had been deemed top priority.  “Did you see that river just a few meters away from our jobsite?” he asked. “Most rivers, when you throw a stone in, it splashes or skips and then sinks.  This one, you throw a stone in and it just goes ‘plop’, then sits there.”  It was only then that I realized that this “river” was El Gran Canal, Mexico City’s infamous open sewer originally commissioned in 1910 by President Porfirio Díaz.

The Robbins guys as well as engineers from the Lot 1 contractor Ingenieros Civiles Asociados (ICA) then explained to me that the canal in this section, lined with shacks, was prone to flooding during each rainy season due to a loss of its slope.  The effects on the people and infrastructure were severe, so the National Water Commission (CONAGUA) had fast-tracked Lot 1.  A pumping station would be put in and the first section of tunnel sealed off so that wastewater from this area could be pumped into a section of the canal downstream that still maintained its negative slope.  I was beginning to realize the importance and urgency of this project!

The guys gave us a tour of the TBM being assembled at the bottom of the shaft, which was specially designed for high pressure conditions under the water table.

Deep shaft at Lot 1

Looking up from the bottom of the Lot 1 shaft where the Robbins machine was being assembled.

Robbins crew on the EPB at Lot 1

Robbins employees on the Lot 1 EPB. From left to right: Andrei Olivares, Robbins Project Engineer; Jeremy Pinkham, Field Service Manager – The Americas; Roberto Gonzalez, General Manager, Robbins Mexico

On the ride home that day we were hit by a particularly nasty rainstorm that went on for several hours.  I learned via the local news later on that the very roads we had driven on to get to the jobsite were now flooded with wastewater and impassable—apparently a regular yet extremely concerning event.

Day 2

The next day we went to CONAGUA’s offices to speak with José Miguel Guevara, General Supply Coordinator for Potable Water and Sanitation.  He spoke with us about the massive scope of Emisor Oriente—a project that could improve the lives of over 20 million people in the area by increasing wastewater capacity by 20% during each rainy season. The new pipeline will bolster current wastewater lines (both El Gran Canal and Emisor Central—a pipeline built in 1964) that have lost their slope due to Mexico City’s sinking lake clays.

Sr. Guevara (right) in the CONAGUA office

Roland Herr, editor of Tunnel magazine (left) talks with Sr. Guevara (right) in the CONAGUA office.

While Guevara was optimistic, he admitted that health problems caused by El Gran Canal were numerous for the people living on its banks.  When asked about future plans, he expressed grave concern that funds were not currently sufficient for a covered option to the open waterway.  “At this moment,” said Guevara, “The Valley of Mexico is vulnerable.  Our new treatment plant will treat 60% of the area’s water, but we need more alternatives as well.  We are working on pieces to the problem, but the problem is not solved yet.”

With Emisor Oriente scheduled to be complete in 2014, I am hopeful that at least some of those problems will be alleviated.  This is a great example of the magnitude that civil engineering works have on societies.  I for one am proud that Robbins has a part in this monumental solution to an age old problem.After visiting Mexico City’s Emisor Oriente Wastewater Tunnel, I realized something: there are urgent projects, and then there are URGENT PROJECTS.  Túnel Emisor Oriente, often abbreviated to TEO by those involved, is the latter.

Day 1

On a good day with light traffic, the jobsite is about an hour’s drive away from the Distrito Federal, the downtown zone of Mexico’s capital city.  Our first day, I noticed how the high rise buildings and restaurants slowly dissolved into ramshackle huts as we drove further from the city to an area known as Ecatepec.  Approaching the site, we crossed a bridge in our SUV that spanned an extremely slow moving grayish brown river (more about this soon).

The Gran Canal

The “river” flowing outside Mexico City.

It was a warm day in June, Mexico’s rainy season, which is quite different from the rain in my home town of Seattle in the U.S.  Each day during the rainy season, the morning dawns sunny and warm–but by 4:00 in the afternoon a torrential downpour begins.  The water floods city streets throughout Mexico City, whose storm drains can’t handle the sudden inundation.  Sometimes the rain only lasts a few minutes, and sometimes it goes for longer.  The water eventually runs into rivers like the one we crossed by the jobsite, creating flooding risks.

We exited our SUV at the Lot 1 shaft and were greeted by several Robbins Field Service guys, including our Field Service Manager for the Americas, Jeremy Pinkham.  I was excited to learn more about the TEO project, where we have three EPB machines among six TBMs that are excavating an epic 62 km (39 mi) long wastewater tunnel. The tunnel will feed into the country’s largest water treatment plant, which is currently being built.

Emisor Oriente Site

The morning of the first day, at the Lot 1 Emisor Oriente site.

As Jeremy and the group walked towards the shaft to be lowered down the elevator, I was struck by a smell—something akin to a vast field of poorly maintained port-a-potties.  I asked Jeremy about the Robbins machine, which was originally intended for Lot 5 but had been fast tracked to bore part of the tunnel section at Lot 1.  I was wondering why this particular section had been deemed top priority.  “Did you see that river just a few meters away from our jobsite?” he asked. “Most rivers, when you throw a stone in, it splashes or skips and then sinks.  This one, you throw a stone in and it just goes ‘plop’, then sits there.”  It was only then that I realized that this “river” was El Gran Canal, Mexico City’s infamous open sewer originally commissioned in 1910 by President Porfirio Díaz.

The Robbins guys as well as engineers from the Lot 1 contractor Ingenieros Civiles Asociados (ICA) then explained to me that the canal in this section, lined with shacks, was prone to flooding during each rainy season due to a loss of its slope.  The effects on the people and infrastructure were severe, so the National Water Commission (CONAGUA) had fast-tracked Lot 1.  A pumping station would be put in and the first section of tunnel sealed off so that wastewater from this area could be pumped into a section of the canal downstream that still maintained its negative slope.  I was beginning to realize the importance and urgency of this project!

The guys gave us a tour of the TBM being assembled at the bottom of the shaft, which was specially designed for high pressure conditions under the water table.

Deep shaft at Lot 1

Looking up from the bottom of the Lot 1 shaft where the Robbins machine was being assembled.

Robbins crew on the EPB at Lot 1

Robbins employees on the Lot 1 EPB. From left to right: Andrei Olivares, Robbins Project Engineer; Jeremy Pinkham, Field Service Manager – The Americas; Roberto Gonzalez, General Manager, Robbins Mexico

On the ride home that day we were hit by a particularly nasty rainstorm that went on for several hours.  I learned via the local news later on that the very roads we had driven on to get to the jobsite were now flooded with wastewater and impassable—apparently a regular yet extremely concerning event.

Day 2

The next day we went to CONAGUA’s offices to speak with José Miguel Guevara, General Supply Coordinator for Potable Water and Sanitation.  He spoke with us about the massive scope of Emisor Oriente—a project that could improve the lives of over 20 million people in the area by increasing wastewater capacity by 20% during each rainy season. The new pipeline will bolster current wastewater lines (both El Gran Canal and Emisor Central—a pipeline built in 1964) that have lost their slope due to Mexico City’s sinking lake clays.

Sr. Guevara (right) in the CONAGUA office

Roland Herr, editor of Tunnel magazine (left) talks with Sr. Guevara (right) in the CONAGUA office.

While Guevara was optimistic, he admitted that health problems caused by El Gran Canal were numerous for the people living on its banks.  When asked about future plans, he expressed grave concern that funds were not currently sufficient for a covered option to the open waterway.  “At this moment,” said Guevara, “The Valley of Mexico is vulnerable.  Our new treatment plant will treat 60% of the area’s water, but we need more alternatives as well.  We are working on pieces to the problem, but the problem is not solved yet.”

With Emisor Oriente scheduled to be complete in 2014, I am hopeful that at least some of those problems will be alleviated.  This is a great example of the magnitude that civil engineering works have on societies.  I for one am proud to have a part in discussing this monumental solution to an age old problem.