London’s Thames Tideway project – aka the super sewer – has become the longest tunnel beneath the River Thames after miners working deep underground passed the 2km mark.

The tunnel is comprised of ‘rings’, each of which is formed of seven concrete segments. The first tunnel boring machine (TBM) to launch has now completed more than 1,000 rings.

Millicent, the TBM responsible the central delivery team’s westbound drive, was working deep underground somewhere beneath Albert Bridge and Battersea Bridge (as of mid May), with around 3km to go until Carnwath Road in Fulham.

The previous record for ‘longest tunnel beneath the Thames’ was held by the 1.3km HS1 tunnel, which crosses between Kent and Essex at Ebbsfleet.

All spoil from the tunneling operation at Kirtling Street, where Millicent launched, is being removed from site by barge. Tideway’s commitment to use the river to transport as much material as possible is keeping thousands of lorries off London’s roads. More than 1 million tonnes have now been transported by river across the project.

The Thames Tideway Tunnel, a major infrastructure project, will tackle sewage pollution in the River Thames and will use six machines to build the 25-km tunnel.

RELATED: London’s Tideway Welcomes First TBM

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Wearing hard hats and yellow vests, nearly 2,000 people led by Copenhagen Major Frank Jensen took advantage of Open Day on May 25 to visit the Enghave Plads station of Cityringen, the city’s new metro line built by Salini Impregilo. The event, the second in a series scheduled for the coming weeks, welcomed the public to discover the recently completed station ahead of the inauguration of the entire line in the following months.

As the Danish capital seeks to become a pioneer in sustainable mobility, the Group will be providing it with a line serviced by driverless trains that will enable the entire metro network to carry up to 130 million passengers a year. The automated system operating the trains will have them run at intervals of a maximum of 100 seconds. The stations that dot the line – two parallel tunnels running for 15.5 km – are on average 30 m below ground.

Cityringen’s completion was an engineering success for Copenhagen Metro Team (CMT), the line’s builder owned by Salini Impregilo, given the complexities of excavating under historic buildings at various points along the line’s trajectory. One was the Magasin du Nord. CMT’s workers excavated a mere 1.5 m below the foundations of the largest department store in the city without obliging shoppers to stay away. The same attention was given during the excavation of the deepest station under Marmorkirken (Marble Church). The work exemplifies the engineering excellence of the Group, which aims to improve its competitive standing internationally with Progetto Italia (Project Italy), an industrial operation to consolidate and capitalize on the know-how of the infrastructure sector in Italy.

Salini Impregilo will be delivering the project in the coming months. The nine years it took for it to complete Citryringen is an achievement given how long similar projects have taken, even when taking into account the different challenges faced by each one. In Paris, it took 15 years to complete 9.2 km of the Line 14 (1993 – 2007); 12.8 years for Line 5 in Milan (2007 – 2015); and 15 years for Line 9 in Barcelona (2002 – 2016).

With Cityringen ready for its inauguration, the city takes another step closer to reaching its goal of eliminating harmful emissions to become carbon neutral by 2025, with 75% of commuting done on foot, bicycle or public transport.

Source: Salini-Impregilo.com

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There was great interest in the various offerings and the state-of-the-art machine park in the training workshop.

On May 25, Herrenknecht AG invited interested boys and girls from local schools together with their parents to the Training Day at the Schwanau plant. In the state-of-the-art training workshop, over 350 visitors took the opportunity to look behind the scenes at the high-tech mechanized tunneling manufacturing facility.

The clear presentation of the individual training occupations as well as hands-on activities gave the pupils practical insights into the reality of an apprenticeship. At 15 stations, the 13 different training occupations in the industrial, technical and commercial areas as well as three options for joining the company while studying were presented.

Making a rose out of metal, designing technical drawings and using a soldering iron quickly brought existing talent and interest in the underlying training occupation to light. Theoretical job descriptions thus came to life as something that could be experienced in a practical setting. The inside of a tunnel boring machine could be explored virtually using VR glasses. Interested participants in the half-hourly plant tour were treated to live impressions. The highlight of the visit was the rotating cutting wheel of a tunnel boring machine for a metro project.

The apprentices and training supervisors willingly answered questions onsite about the application process, the theoretical and practical content of the training occupations and degree internship programs, as well as about the course of the apprenticeship. The opportunity to receive first-hand information was gladly used.

Herrenknecht invited school pupils and their families to a Training Day in its training workshop. Together with their parents, around 350 boys and girls took the opportunity to look behind the scenes at the Schwanau tunneling technology company.

Klaus Himmelsbach, Head of Training at Herrenknecht AG, is satisfied: “I am personally pleased that the offer to get a taste of our apprenticeships is so well received. It’s simply great if we can inspire young people about our company and create transparency. Because only if pupils can really get an idea of what the training occupations are like are they able to choose the right apprenticeship.”

Currently there are about 150 apprentices and student trainees at Herrenknecht AG undergoing training in Schwanau. As of the new training year, Herrenknecht offers a total of 180 young people apprenticeships and degree internships, making it one of the largest trainers in the region. The training team is donating all of the takings from the barbecue, coffee and cake stalls to the Freiburg Children’s Cancer Clinic.

RELATED: Successful Re-use for Herrenknecht Borer in The Hague

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Santamaria

Normet Board of Directors has appointed Ed Santamaria President & CEO of Normet Group. Santamaria takes over from Interim President & CEO, Aaro Cantell and he will start in his new role latest in November this year. He will be based in Normet’s Espoo office.

“I am extremely pleased that we have found a new CEO of this high caliber from our own industry sector. Ed knows well how to lead people in this kind of a global matrix organization. He also knows personally many of our customers and their future plans. I believe he can help us find areas to improve our operational efficiency as well as help identify new growth areas”, says Aaro Cantell, Chairman of Normet Group.

Santamaria brings a wealth of experience from mining industry. He is currently President, Parts & Services Division at Sandvik Mining & Rock Technology. He has spent in total 13 years in different management roles within Sandvik. Prior to Sandvik he spent 20 years with SDS corporation, a designer and manufacturer of drilling equipment. SDS was acquired by Sandvik in 2006. He is an Australian citizen with an MBA degree. He is married and has two children.

“I am very excited to join Normet. I believe joining an entrepreneurial and agile company with a global reach is a unique opportunity for me. I think I can contribute to the further development of Normet business both within tunneling and mining segments”, says Santamaria.

RELATED: Hallett Appointed to Lead Normet North America

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The benefits of pipe jacking are well established. By choosing pipe jacking over open-cut construction, owners can have a precisely installed pipeline with less disruption to the public – and at a competitive price, with less noise and lower emissions.

While the benefits of pipe jacking are apparent, they don’t come without some risk. Everyone is familiar with the adage, “a chain is only as strong as its weakest link.” While that principle can apply in many different scenarios from business to sports, it literally applies to pipe jacking.

In pipe jacking, each pipe segment is thrust into the ground, one after the other, building a “pipe chain” underground of increasing length and weight thus incrementally building stress in the pipe. Any failure of an individual pipe segment or joint at any point along the alignment can have potentially devastating consequences to a project, especially in urban areas or on water crossings where accessing the pipeline via a “rescue shaft or tunnel” can be difficult, if not impossible.

Historically, there has been limited knowledge of pipe jacking among owners and engineers, particularly when it comes to what makes an acceptable concrete jacking pipe. This is understandable considering the niche nature of pipe jacking in general and microtunneling in particular. Due to the critical nature of each pipe segment along the pipe string, concrete pipe that has been well suited for open-cut construction for decades simply does not meet the demands of modern pipe jacking.

Today, pipe jacking and microtunneling contractors need jacking pipe built with the end use in mind. Jacking pipes need added strength, joints that allow the pipe string to curve, and gaskets that prevent the ingress of water, soil or bentonite.

This doesn’t mean that jacking pipes need to be complicated in their design or manufacture. There are several pipe manufacturers in North America that make pipe segments that meet the expectations of pipe jacking and microtunneling contractors. We spoke with Robert Ward, an engineer and co-founder/owner of Ward and Burke Microtunnelling, who shared his experience related to concrete jacking pipe for microtunneling projects in the United States and Canada. Ward and Burke Microtunnelling is a member of the North American Microtunneling Association (www.NAMicrotunneling.com), an organization of contractors that promotes education and dialogue on issues related to microtunneling.

“The first thing that an owner should consider is that in many cases the jacking pipe is the final permanent product – nothing else is of any interest in the long run,” Ward said. “Therefore, it is far and away the most important part of the microtunneling process.”

Indeed, upon its commissioning, the jacking pipe might be the final permanent product and carry water, sewage or other utilities, so the longer it lasts, the more cost-effective the initial installation becomes. In addition, that means fewer disruptions to the public for future repair or replacement. It is important to remember that the jacking pipe may also be a casing pipe for a permanent product pipe such as PVC, DIP, etc. Sometimes the annulus between the casing and the final pipe is backfilled rendering the casing pipe temporary in nature, but if the annulus is not filled, the jacking pipe is a permanent structure. In all situations and uses, having a high quality jacking pipe is critical to having a successful project.

So, what are the characteristics that comprise a good concrete jacking pipe? Ward identifies several areas he sees as key. While currently there is not a standard specification for microtunneling pipe, Ward says that parts of several existing ASCE and ASTM standards can be combined to make good reinforced concrete jacking pipe for microtunneling projects. Ideally, these disparate sections will be combined into a single standard that design engineers can cite when writing specifications for microtunneling projects, especially those with difficult geology, long drives, or curves.

Rigidity: The first characteristic needed for a competent jacking pipe is rigidity, Ward said, and that leads to concrete. “During construction, the pipe is going to encounter obstacles that are going to put point loads on it, and that pipe needs to stay in a circular shape,” he said. “The TBM is rigid and it cuts a circle, so it makes sense that whatever you are pushing behind the TBM should also stay a circle. Concrete is rigid and stays in a circle when it gets point loaded.”

Joint Design: “One of the keys to successful microtunneling is reducing the friction so you maintain low jacking forces,” Ward said. “The way to do that is by injecting bentonite around the outside of the pipe. The bentonite often needs to be injected somewhere between 40 and 100 psi. Therefore, the gasket has to be able to withstand 100 psi of external pressure – not 13 psi which is typical for open cut pipes.”

The pressure is key in keeping the annulus open, thus preventing sand and soil from gripping the pipe and increasing friction along the pipe string.

Typical concrete piping systems use gaskets that are designed to keep groundwater out of the pipeline, but do not account for the bentonite lubrication systems. “Some people think that if they are tunneling in dry or shallow ground that they can make do without a gasket capable of resisting higher pressures, but that is not the case. It has nothing to do with groundwater. Failure to resist bentonite pressure will result in sand and soil coming into contact with the pipe, and consequently, pipes getting stuck.”

Steerable Pipe: Curved drives have been common internationally for a number of years, and over the past five years have become commonplace in the United States and Canada. The ability to perform curved drives can eliminate intermediate shafts or avoid obstacles, resulting in more cost-effective projects.
Even if the designed alignment is straight, the ability to steer is an important characteristic for microtunneling pipe. “The pipe needs to be capable of negotiating a 500-m radius curve, regardless of whether the tunnel is curved or straight in theory,” Ward said.

That requires the pipe’s tailskin extending 7 in. to allow the flexibility for the joint to open and close without losing pressure on the gasket. According to Ward, where the tailskin is embedded in the wall of the concrete pipe, it needs an angle that acts as both an anchor and a waterstop. Additionally, the tailskin needs a studded anchor every 12 in. welded to it around the perimeter or rebar anchors welded to the tailskin for the purpose of preventing the tailskin from coming loose and allowing water to leak around it. Finally, a hydrophilic strip glued onto the inside of the tailskin is needed to act as an additional waterstop. (See Figure 1: Typical Joint Detail for Concrete Jacking Pipe)

Figure 1: Typical Joint Detail for Concrete Jacking Pipe

Axial Loads: In pipe jacking, the ability of the pipe to accept axial loads is key to success. The pipe has to be able to be pushed through the ground without any failures. Regardless of the length of project, a stout pipe is needed because, in an imperfect world, difficulties arise and a microtunneling contractor may need to apply extra force to keep the pipe string moving.

Furthermore, concrete jacking pipes should be wet cast vs. dry cast, Ward said. Although dry cast pipes, typically used for open cut projects, have the same ultimate strength as wet cast, wet cast pipes have a higher resistance to strain and can carry an axial load of approximately 2,000 tons on an 84-in. pipe on a radius of 1,500 ft.

“From our experience, when strain exceeds 0.002, dry cast concrete pipes begin to lose their ability to resist load,” Ward said. “Wet cast concrete pipes have very little drop off in their ability to resist load and can continue to carry load even at strains exceeding 0.002 and up to 0.005 or more. ACI/ASCE designs for an ultimate strain capacity of 0.003, but it is still good to know there is sufficient load capacity above this strain in a ‘doomsday’ scenario.”

“High strains on the pipe are not an everyday occurrence, but you have to prepare for the day when things go wrong,” Ward said. “You may need to push really hard on the pipe to get you out of a tight spot, and wet cast pipe will be able to take those loads.”

Another benefit of the wet cast process is the smooth exterior of the jacking pipe. This smoother pipe surface reduces the skin friction on the pipe string, thereby lowering the required jacking force being applied to the pipe to complete the drive.

Pipe Wall Thickness: In addition to its rigidity, concrete pipe is well suited for pipe jacking projects because of its wall thickness. The thick walls of concrete pipe give an ability to accommodate intermediate jacking stations (IJSs or interjacks), which are typically installed on long microtunneling drives as a means of applying thrust in addition to the jacks at the entry pit. Interjacks are placed periodically along the pipe string between pipe segments and this additional thrust capability serves almost as an insurance policy in case an extra push on the pipe string is needed.

The diameter of the interjack cylinders is approximately 6 in., and a wall thickness of at least the diameter of the interjack cylinders is needed.

“Concrete pipe, with its thick wall has an inherent economic advantage over all other products because it can be used with interjacks at very high loads,” he said. “Again, you might not need to use interjacks often, but when you need them you don’t want a pipe that gives up.” Compared to other pipe materials, interjack stations in concrete pipe tend to be more economical to fabricate, install during jacking and then to remove when the jacking is complete.

Sourcing the Pipe: Ward says that many concrete pipe manufacturers are more than capable of delivering high-quality jacking pipe. The crucial aspect is creating a high-quality mold. The tolerance of jacking pipe needs to be higher than typical open-cut concrete – on the order of 1/16th of an inch. Ward and Burke has worked with concrete pipe manufacturers in the United States and Canada that are producing world-class concrete pipes for world-class projects.

“Once you have the mold set up, the pipe is simple to make,” Ward said. “It doesn’t cost a lot more to make the right pipe, and it will save you a lot of money vs. getting the pipe stuck.”

Industry Standards: There has been some discussion within the industry about the need to write a new specification related to concrete jacking pipe, but Ward says that existing documents can be used as guidance for making concrete pipe that meets the needs of microtunneling contractors, beginning with ASCE 27-00, and its follow-on ASCE 27-17: “Standard Practice for Direct Design of Precast Concrete Pipe for Jacking in Trenchless Construction.”

“ASCE 27-17 is the bible for microtunnelers,” Ward said. “You need to know it and abide by it.”

For strength of the pipe, ASTM C76-19: “Standard Specification for Reinforced Concrete Culvert, Storm Drain, and Sewer Pipe” can be used as a reference document. The standard identifies five different classes of pipe, with Class V being the most robust. Ward suggests using Class V pipe for all pipe jacking projects (except when tunneling in beach sand or rock, where Class IV may be acceptable).

Standards regarding the gaskets for pipes up to 50 psi pressure rating can be found under ASTM C361-16: “Standard Specification for Reinforced Concrete Low-Head Pressure Pipe.” AWWA’s C-300 pipe specification should be used for cylinder encased microtunnel concrete pipes for pressure ratings between 50 and 150 psi.

ASCE has also published the book “Standard Construction Guidelines for Microtunneling,” which covers the planning, design, pipe materials and construction of microtunneling (CI/ASCE 36-15).

By choosing properly designed pipe for the job, owners can achieve successful projects that meet the demands of the public for generations to come.

Robert, Ward, co-founder of Ward and Burke, was the source of this article on behalf of the North American Microtunneling Association (NAMA). NAMA and its members endorse the contents of this article.

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Brierley Associates announced the additions of Amr Ewais and Anna Crockford to its staff.

Ewais is a registered Professional Engineer in the Province of Ontario, Canada, and has more than 14 years of experience in geotechnical, geoenvironmental and structural engineering. He joined Brierley from the University of California Berkeley where he worked as a research associate for two years. Ewais earned his PhD in geotechnical and geoenvironmental engineering from Queens University, Kingston, Ontario, Canada. He earned his M.Sc. in tunneling and B.Sc. in civil engineering from Ain-Shams University, Cairo, Egypt.

Ewais has authored or co-authored 15 industry papers on the use and characteristics of HDPE geomembranes. His geotechnical engineering expertise ranges from: infrastructure monitoring (using fiber optics), post-grouted shafts, contaminant transport, slope stability; and, structural analysis and design.

Crockford  has eight years of geological engineering experience, primarily with mine design and is a registered Professional Engineer in the Provinces of Ontario and Alberta. She has worked on a wide variety of geotechnical engineering problems in the mining sector (underground and open pit) and heavy civil project including dams, foundations and tunnels.

Crockford has expertise in rock mechanics, excavation and support design, 2D and 3D numerical modeling of geomaterials, natural and engineered slopes, and underground excavations. She earned a Bachelor of Science in Geological Engineering and Master of Applied Science in Geomechanical Engineering from Queen’s University in Kingston, Ontario, Canada. She has authored and co-authored a dozen industry papers and presentations on geomechanics, rock support and tunneling.

Both Ewais and Crockford will be based in firm’s Denver office.

RELATED: Brierley Associates Welcomes New Hires

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Three times per year, TBM: Tunnel Business Magazine recaps the status of major tunneling projects underway in the United States and Canada. Below is the Tunnel Update that appeared in the June 2019 issue of the print edition.

CALIFORNIA

Carson/Los Angeles/Rancho Palos Verdes

Joint Water Pollution Control Plant Effluent Outfall Tunnel
Dragados USA
NTP for this $630.5 million project for the Los Angeles County Sanitation Districts (Sanitation Districts) was issued April 8, 2019, with 1,900 working days to complete the work and an estimated completion date of October 2026.

The new discharge tunnel will provide better seismic resiliency, provide additional capacity for population growth and storm events, and will provide redundancy for the two existing tunnels that were constructed in 1937 and 1958, which have not been inspected in nearly 60 years. The tunnel will be constructed by either a slurry or EPB single pass TBM beginning at the JWPCP Shaft Site (entry shaft) and ending at Royal Palms Beach (exit shaft). The tunnel alignment will vary in depth from approximately 50-ft to 450-ft below the ground surface. The entire tunnel alignment will be below the groundwater table with pressures ranging from 1 to 9 bar. As part of the scope, a 14-ft diameter cast-in-place concrete connection will be constructed to convey the treated effluent from an existing force main to the proposed JWPCP Shaft. The project also features an approximately 60-ft diameter and 113-ft deep drop shaft.

Tunneling will go through two distinct geologies. The first half will be through soft ground with depths up to 110 ft. The second half will be through hard rock with depths up to 450 ft where the tunnel will be subjected to intense ground squeezing conditions due to the overburden pressure.

The tunnel lining will consist of bolted and gasketed precast concrete segments. Tunneling will go through splays of the Palos Verdes Fault Zone where 16-ft diameter steel liner will be used within the 18-ft diameter concrete segments to accommodate displacement from seismic events at two locations. When in operation, the tunnel will be under hydrostatic pressure. In the first half of the alignment, internal pressure will exceed the external pressure and post-tensioning of the concrete segmental liner will be necessary. To offset the “hoop stress” developed from internal pressure, a post-tensioning system consisting of internal steel tendons along the circumference of the concrete liner was specified. This post tensioning design has only been used a few times in the world, but never before in North America. In the second half of the alignment, the hard rock around the tunnel will offset the internal pressure, and post-tensioning will not be required.
As of May 2019, the project is in the submittal phase with site work at the JWPCP Shaft Site expected to begin in the summer of 2019. Construction of the slurry wall for the JWPCP Shaft Site is expected to begin in the fall with excavation of the shaft expected to begin in early 2020.

Lead Design Consultant: Parsons; Tunnel Design Consultant: McMillan Jacobs Associates; Tunnel Construction Management Consultant: Mott MacDonald; Subcontractors for Dragados – Excavation and Structures: W.A. Rasic Construction Company Inc.; Jet Grouting and Support of Excavation: Malcolm Drilling Company Inc.

Personnel: Los Angeles County Sanitation Districts – Field Engineering Section: Michael Tatalovich, Section Head; Russell Vakharia, Resident Engineer; Sewer Design Section: Anthony Howard, Section Head; Oscar Morales, Supervising Engineer; Yoonkee Min, Senior Engineer; Parsons – Danson Kelii, Project Manager; McMillan Jacobs Associates – John Stolz, Lead Tunnel Design Consultant; Mott MacDonald – Daniel McMaster, Lead Tunnel Construction Manager; Dragados – John Kennedy, VP of Operations; Lawrence Lenahan, Project Manager; Claudio Cimiotti, Construction Manager; Willie Flores, Project Superintendent.

Los Angeles

Crenshaw/LAX Transit Project
Walsh/Shea Corridor Constructors
This $1.278 billion project for the Los Angeles Metropolitan Transportation Authority (Metro), being built by a joint venture of Walsh and Shea, is an 8.5-mile light-rail line that will run between the Expo Line on Exposition Boulevard and the Metro Green Line. NTP was issued in September 2013 with revenue service expected in mid 2020.

The project consists of twin bore tunnels, about 1-mile long each, connecting three underground stations. The tunnel is 21-ft OD (19-ft ID) and is approximately 70 ft below ground. Ground conditions are soft ground/alluvial, leading to the choice of an EPB TBM. All tunneling and heavy civil activities are complete.
TBM – Herrenknecht (Germany); Consultants: HNTB; Construction Support Services: Stantec; Tunnel Engineering: Arup; Systems: L.K. Comstock; Structural Engineering: SC Solutions; Community Outreach: Los Angeles Urban League; Civil Engineering: Jenkins/Gales & Martinez; Electrical: Neal Electric; Quality Control: QEI; Survey: Psomas.

Los Angeles

Regional Connector
Regional Connector Constructors (Skanska-Traylor JV)
The Regional Connector project is in the heart of downtown Los Angeles in a congested urban environment that provides numerous challenges and requires coordination with multiple third parties. The Regional Connector will connect three operating rails systems, the Metro Blue and Expo lines on the West and the Gold Line on the East. When complete, transit riders will no longer need multiple transfers and can travel north-south and east-west on the same system.

The tunneling portion of the $1.75 billion Regional Connector Transit Project for the Los Angeles County Metropolitan Transportation Authority involves 5,795 feet of twin tunnels with an excavated diameter of 21 ft. The ground conditions range from alluvium soils to clayey siltstone of the Fernando formation, with the potential for methane, hydrogen sulfide gas, and boulders. The groundwater table is generally above the tunnel alignment. Pressure balance tunneling utilizing an EPB TBM was required, along with precast concrete segments with double gaskets as the tunnel lining system. The tunnel depth (cover) ranges from 25 ft to approximately 120 ft and crosses below the existing Metro Red Line heavy rail tunnels with less than 7 ft of clearance. The Regional Connector includes approximately 2,100 ft of cut-and-cover and retained cut guideway, a 300 ft crossover cavern excavated by sequential excavation method (SEM) techniques, and three cut-and-cover subway stations. The bored tunnels were excavated by one TBM concurrently with the construction of the three stations, requiring coordination between the cut-and-cover operations and TBM tunnel excavation.

As of May 2019, construction progress includes:

• The bored tunnels were successfully completed on time in January 2018, and the TBM has been demobilized. All three cross passages, tunnel inverts, and walkways are completed.
  All three underground stations have been excavated and are currently in the concrete phase, with walls and elevated slabs being constructed at each area.
• The SEM cavern, located next to the Historic Broadway Station, is a 300 ft long x 58 ft wide and 36 ft high cavern and will be used to provide a future cross over for Metro Operations. The excavation for the cavern was broken into three drifts staggered by 60 ft. The left drift, started on May 31, 2018, and the right drift, started on July 6, 2018, were each was completed in 5 months. The center drift was broken into a top heading and invert heading which were completed in 6 months. The excavation of the cavern was successfully completed on Feb. 28, 2019, with surface settlement matching the predicted values from the design model. The SEM cavern is currently being lined with HDPE and the invert construction is underway. Final concrete liner is anticipated to be completed in February 2020.
• The Flower Street cut-and-cover tunnel progress continues. Excavation will be completed summer 2019 and concrete inverts are underway.
• The overall project is progressing on schedule and is anticipating to start the tie-in to the existing Metro Gold Line mid-2020.

The Regional Connector is a design-build project. The final design is approximately 99% complete, and the construction is approximately 55% complete, as of May 2019.

Tunnel Designer for the Contractor: Mott McDonald; TBM: Herrenkecht. Preliminary design was completed by CPJV (AECOM/WSP), which is also performing design services during construction, and Metro’s Construction Management Consultant is Arcadis.

Key Project Personnel – Metro Project Executives: Gary Baker, Project Manager; Michael Harrington, Engineering Manager; Mat Antonelli, Construction Manager; Metro Design Consultants: (AECOM/WSP), Bill Hansmire, Tunnel Design Manger; Metro Construction Manger Consultants: (Arcadis), Jaydeep Pendse, Resident Engineer; Contractor Project Executives (Regional Connector Contractors RCC): (Skanska) Mike Aparicio, Mike Smithson, Greg Zwiep, Justin Waguespack; (Traylor) John McDonald, Richard McLane, Christophe Bragard.

Los Angeles

Westside Purple Line Extension Section 1
Skanska/Traylor/Shea JV
The Westside Purple Line Extension Project is a 9-mile long project that consists of three Sections that are being planned to be built and opened for revenue service before the end of the next decade. Section 1 is a 3.92-mile long subway alignment with three stations that is being constructed under Wilshire Boulevard in gassy ground and tar sands with prehistoric fossil deposits utilizing design-build.

NTP for the $1.636 million design-build contract was issued on Jan. 12, 2015. The twin EPB TBMs had advanced 6,200 and 4,600 ft with hole through expected in late spring. Significant work is underway at each of the three stations and the shaft. The Revenue Service Date per the Full Funding Grant Agreement is Oct. 31, 2024.

The scope of work includes 17,900 ft of twin-bore tunnel: Reach 1 is 9,600 lf between Wilshire/La Brea Station and Wilshire/Western TBM retrieval shaft; Reach 2 is 4,400 lf between Wilshire/La Brea and Wilshire/Fairfax Stations; and Reach 3 is 3,300 lf between Wilshire/Fairfax and Wilshire/La Cienega Stations. There is also 600 lf of tail track at Wilshire/La Cienega Station.

The tunnel is 18-ft, 10-in. diameter with 12-in. thick precast concrete lining. Depth varies from 40 to 100 ft. The alignment includes three stations and the western retrieval shaft and 23 cross passages. Tunnels are planned to be mined by two Herrenknecht EPBMs. Cross-passages are planned to be mined by the sequential excavation method using variety of localized ground support systems.

Tunnel Designer: PTG/CH2M; Construction Manager: WEST JV (Stantec/Jacobs Engineering/AECOM); Subcontractors – TBM: Herrenknecht; Precast: Traylor; Support of Excavation/piles: Condon Johnson; Jet Grouting: Malcolm Drilling; Geotechnical instrumentation: Group Delta; Dewatering: Moretrench; Standpipe: Link Nielsen.

Los Angeles

Westside Purple Line Extension Section 2
Tutor Perini-O&G JV
The second section of the Purple Line Extension Transit Project includes 2.59 miles of additional tracks to Metro’s Rail system and two new stations at Wilshire/Rodeo and Century City/Constellation. Tutor Perini-O&G JV was awarded a $1.37 million contract in 2017.

Major construction began last spring with construction at the planned launch area for a tunnel boring machine at the Century City/Constellation Station location. Major work at the planned Wilshire/Rodeo Station in Beverly Hills was expected to begin by the end of 2018 or early 2019. Transit operations are set for 2025.

Los Angeles

Westside Purple Line Extension Section 3-Tunnels
Tutor Perini/Frontier-Kemper
Tutor Perini/ Frontier-Kemper JV was awarded a $410 million contract by the Los Angeles County Metropolitan Transportation Authority for the Purple Line Extension Section 3 Tunnels Project.
The project involves the design and construction of twin bored tunnels for future Purple Line subway service spanning approximately 2.6 miles between Century City and the VA Hospital in Westwood. Substantial completion is anticipated in the summer of 2022, with revenue service planned for 2027.

Los Angeles

Westside Purple Line Extension Section 3-Stations
Tutor Perini/O&G
Tutor Perini/O&G JV has received notice of intent to award a contract from the Los Angeles County Metropolitan Transportation Authority for the Purple Line Extension Section 3 Stations project.
The contract value is anticipated to be approximately $1.4 billion. The scope of work entails the design and construction of two new subway stations at Westwood/UCLA and Westwood/Veteran Administration (VA) Hospital. The company is currently performing initial design work on the companion Purple Line Extension Section 3 Tunnels project, awarded last year, which will build the tunnels and related systems that will connect with the new Westwood/UCLA and Westwood/VA Hospital stations.
The Purple Line Extension, Section 3, will add 2.56 miles of new rail to Metro’s Rail system and connect downtown Los Angeles to the Westside. The project is anticipated to begin construction in 2019 and be open for operations in 2027.

Redwood City

SVCW Gravity Pipeline Project
Barnard Bessac Joint Venture
This is a two-stage, $214 million project for Silicon Valley Clean Water (SVCW). The first stage (design) was awarded on Oct. 5, 2017, and is complete. The second stage (construction) was awarded on Nov. 8, 2018. Final completion is expected in October 2022.

The project involves 17,560 ft of tunnel split into two drives of 5,260 and 12,300 lf. The tunnel is 13.5 ft ID, 16.2 ft bored diameter by new EPB TBM manufactured by Herrenknecht. The depth reaches 23 m at its lowest point, 12 m deep at its shallowest. There is one temporary launching shaft, 58 ft ID made of slurry wall, and two permanent shafts as inlets made of fiberglass or polymer concrete lining.

Ground conditions include firm and compacted clay with occasional silty sand lenses (in connection to the San Francisco water bay). The double-pass lining includes a concrete lining installed by TBM, followed by an 11-ft ID fiberglass pipe installed and grouted after tunnel excavation. The rings are made of six equally sized segments, 1.5 m long, 10-in. wide wide, left and right universal segment

The schedule is as follows: Start launch shaft construction: January 2019; Start TBM excavation: September 2019; End of first drive: April 2020; End of tunnel excavation: October 2021; End of FRPM pipe installation and grouting: May 2022.

The project is one of the first tunnels in the United States to use a progressive design-build contract (development of the design conjointly with the owner, continuous cost estimation of the construction during design development, risk sharing). Crews will use a continuous conveyor for TBM muck out, which is unusual for such a small diameter tunnel with multiple 800 ft curves. It is also largest FRPM installation in tunnel in North America.

Other unique aspects of the job include a 10-degree inclined conveyor in a pushed tube tunnel from the launching shaft to the spoil basin; height restriction (<60 ft) due to vicinity to the San Carlos airport, which affects construction techniques for three shafts; low cover under a river bed (<2 diameter), under a live sewer forcemain for 60% of the project alignment; and work in a marine protected area (Bair Island).

Contractor: Barnard Bessac JV (PM: Jack Sucilsky, DPM: Oliver Robert); Designer: ARUP (EOR: Jon Hurt, PM: Nik Sokol, tunnel designer: Luis Piek); Construction Manager: Tanner Pacific (PM: Mike Jaeger, DPM: Bruce Burnworth); Owner technical Advisor: Kennedy Jenks; Launch shaft contractor: Malcom; TBM: Herrenknecht; Conveyor supplier: H&E logistic; Precast segments: Traylor Shea JV.

CONNECTICUT

Wethersfield

Goff Brook Overflow Closure
Bradshaw Construction Corp.
Bradshaw is in the process of completing a 60-in. microtunneling/conventional TBM project for 30- and 48-in. FRP sanitary sewer installations. The first tunnel (650 ft) was installed by an Akkerman WM480. The second (420 ft), third (855 ft), fourth (152 ft) and fifth (450 ft) tunnels were completed behind a Herrenknecht AVN 1200. An additional drive of 48-in. RCP was added to the project by change order, and mining was completed this winter for this final crossing. This 510-ft drive was installed on a 1,168-ft radius curve. Ground conditions for microtunneling operations were predominantly siltstone, with occasional decomposed rock and dense alluvium. The project members include the Metropolitan District Commission (Owner), Jacobs (Engineer) and Baltazar Contractors Inc. (General Contractor), with Bradshaw Construction performing as tunneling subcontractor. Project Manager: Jordan Bradshaw.

GEORGIA

Atlanta

City of Atlanta Water Supply Project
Atkinson Construction
This $300 million water supply project includes the excavation of a five-mile rock tunnel connecting the Chattahoochee River and the Hemphill Water Treatment Plant to the former Bellwood Quarry. The quarry will be used for storage, increasing the City of Atlanta’s water reserve from 3 to 30-90 days.

Atkinson Construction with JV partner Technique was subcontracted under the Construction Manager at Risk contract to build the tunnel, using a 12.5-ft hard-rock TBM supplied by The Robbins Co. The project included many unique aspects including owner-procured TBM, On-site First Time Assembly of the TBM, and it is one of the first uses of CMAR for tunnel projects in the United States.

The tunnel holed through in October 2018. As of mid April, Atkinson had lined approximately 33% of the tunnel, with completion of lining expected in September. Crews were about 70% with the excavation of the drill-and-shoot tunnel extension.

CMAR: PC Construction/HJ Russell JV; Design; Stantec, PRAD Group Inc., and River 2 Tap. TBM: Robbins. Tunnel Contractor: Atkinson/Technique.

ILLINOIS

McCook

McCook Reservoir Des Plaines Inflow Tunnel
Walsh Construction
This $107.7 million project for the Metropolitan Water Resources District (MWRD) includes approximately 5,800 ft of 20-ft ID tunnel with two shafts (one permanent and one for construction to be abandoned at completion of work). Entire tunnel is in dolomite limestone and is being constructed via drill-and-blast methods. Tunneling is nearing completion and lining has begun.

The tunnel has two live connections, one on each end. On one end it will connect to the terminus of MWRD’s existing Des Plaines Tunnel system and on the other it will connect to the live McCook Reservoir, which was placed in service in December 2017. MWRD cannot shut down either the tunnel or the reservoir to accommodate the connections so all work will be heavily weather dependent.

NTP was issued on July 9, 2016. Completion is scheduled by Jan. 23, 2020. The designer is Black & Veatch.

Personnel – MWRD: Kevin Fitzpatrick, Carmen Scalise, Patrick Jensen. Walsh: Brian Fidoruk, Nick Simmons. B&V: Mark White, Cary Hirner.

KENTUCKY

Louisville

I-64 & Grinstead CSO Trenchless Installation
Bradshaw Construction Corp.
Bradshaw is beginning construction on a CSO interceptor tunnel. The 1,252-ft rib-and-board tunnel will be installed behind a 102.5-in. LOVAT ME-99RL Series 11700 TBM. The tunnel will contain an S-curve on twin 2,300-ft radius curves. Once completed, 84-in. FRP will be installed and backfilled. Bradshaw will also construct two 24-ft ID rib-and-board access shafts. Project geology consists predominantly of clay, with 300 ft of weathered limestone expected in the middle of the crossing. The project members include the Louisville and Jefferson County Metropolitan Sewer District (Owner), Qk4 (Engineer) and Bradshaw Construction performing as the General Contractor. Project Manager: Jordan Bradshaw.

Louisville

Ohio River Tunnel (ORT)
Shea-Traylor Joint Venture (S-T JV)
The Ohio River Tunnel for Louisville and Jefferson County Metropolitan Sewer District (MSD) includes 20,205 ft of main line tunnel and 1,117 ft of tunnel bifurcation for a total of 4 miles of 20-ft finished diameter tunnel (22-ft, 4-in. excavated diameter). Tunnel depth is 180 to 220 ft. The project includes three large diameter shafts (30 to 48 ft diameter) – Pump Station Shaft, TBM Working Shaft, and TBM Retrieval shaft, along with five smaller diameter drop shafts (9 to 11 ft diameter). The tunnel will be excavated entirely in rock. Depth of overburden (above top of rock) varies between 40 and 120 ft. Crews are using a Robbins open face main beam hard rock TBM.

Approximately 2,000 ft of tunnel has been excavated. The TBM reached the end of the tunnel bifurcation on April 30, 2019. S-T JV is backing up the TBM through the tunnel bifurcation, after which they will continue excavating the main line tunnel.

For the bifurcation, gage cutters, scoop buckets on the cutterhead, and a section of the finger shield will be removed, so the TBM can fit through the rock it just excavated.

The current contract amount with tunnel extension is $140.37 million (bid at $106 million. Substantial completion is expected by Dec. 31, 2020, with final completion by March 31, 2021.

Tunnel Designer: Black & Veatch. Construction Manager: Black & Veatch. Major Subcontractors: Steppo Supply & Construction, MAC Construction & Excavating, Schnabel Foundation Co., Malcolm Drilling Co., 7NT Enterprises, Platt Construction, TEM Group, Ziegenfuss Drilling, Toni Levy & Associates, Harmon Steel. TBM: Robbins.

Key Project Personnel: MSD Construction Manager: Greg Powell; MSD Project Manager: Jacob Mathis; Black & Veatch Design Project Manager: Jonathan Steflik; Black & Veatch Sr. Construction Manager: Pete Boysen; Black & Veatch Construction Manager: Alston Noronha; S-T JV Project Manager: Shemek Oginski; S-T JV Assistant PM: Jesse Salai; S-T JV General Superintendent: Ron Walton.

MARYLAND

Montgomery County/Prince George’s County

Purple Line Light Rail Project
Purple Line Transit Partners (PLTP)
The Purple Line is a 16.2-mile light rail transit line extending from Bethesda in Montgomery County to New Carrollton in Prince George’s County. It is being delivered via a $5.6 billion P3 contract that includes a $2.1 billion design-build construction contract. The line connects major activity centers located inside the heavily congested Capital Beltway, and will provide direct connections to four branches of the WMATA Metrorail system (both branches of the Red Line at Bethesda and Silver Spring, the Green Line at College Park, and the Orange Line at New Carrollton), as well as all three MARC commuter rail lines (linking Washington, Baltimore, and Frederick, Maryland) and Amtrak’s Northeast Corridor. NTP was received on June 17, 2016. The revenue service availability date is March 11, 2022.

The scope of work includes a twin-track light rail system operating mainly at grade in dedicated or exclusive lanes and 21 stations. The route includes 0.7 miles of elevated guideway and 1,020 lf of tunnel excavated by SEM. There is also a shaft and cavern to be constructed in bedrock in Bethesda that will serve as interface between the future Purple Line and the existing underground WMATA station. SEM tunnel excavation was completed on March 11, 2019. Installation of waterproofing and a cast-in-place invert track-slab is currently ongoing. Sinking of the shaft in Bethesda by drill-and-blast is in progress as well. Current depth is approximately 80 ft.

The ground conditions at tunnel horizon encompass mixed face conditions varying from slightly weathered metamorphic rock to completely decomposed rock known as saprolite. Most of the tunnel runs below the groundwater table.

Design-Build Contractor: Purple Line Transit Constructors (PLTC), an LLC comprised of Fluor, Lane and Traylor Bros. Tunnel Designer: Mott MacDonald.

Project Personnel – MTA Project Director: William Parks; Concessionaire’s Project Manager: Peter Van der Waart; PLTC: Project Manager Scott Risley; Construction Manager: Ken Prince; Underground Construction Manager: Jean-Marc Wehrli.

MICHIGAN

Detroit

Detroit River Interceptor Repair
Jay Dee Contractors Inc.
GLWA-DB-226 is a $19,845,500 design-build project for the Great Lakes Water Authority (GLWA) for the repair of 12 miles of the Detroit River Interceptor (DRI). The DRI runs parallel to the Detroit River and ranges from 8- to 16-ft diameter. The majority of the interceptor was constructed on the early 1900s of brick and unreinforced concrete. The sewer has no flow control structures in place, so flow is controlled using existing pump stations and storage basins in the GLWA system. In addition, Jay Dee Contractors will be constructing one access structure and 3 flow control structures. The shafts will be constructed using Ribs & Lagging and Soldier Piles & Lagging. The ground conditions range from stiff clay to soft clay and the depths range from 16 to 30 ft.

The interceptor repairs include debris removal, leak repairs with chemical grout, deep concrete repairs and structural relining. Repair design for 45% of the tunnel is complete and the gate structure design is 90% complete. Repairs and cleaning have started for the first 17,000 ft of tunnel. The Conner Creek Access Structure shaft is complete and concrete work will begin in May.

Designer of Record: FK Engineering (FKE). Design Subcontractors: Applied Science, Anderson, Eckstein & Westrick. Interceptor Cleaning and Repair Subcontractor: Doetsch Environmental Services Inc.

Personnel: Jay Dee – Project Manager: Curtis Rozelle; Jay Dee Superintendent: Martin Valles; Jay Dee Senior Advisor: AG Mekkaoui; FKE Project Manager: Fritz Klingler; FKE Construction Manager: Zach Carr; FKE Project Engineer: Paul Wakefield; FKE Design Lead: Nick Bassett.

Oakland County

Michigan I-75 Modernization Project (Segment 3)
Jay Dee Contractors Inc.
The I-75 Modernization Segment 3 Design-Build-Finance-Maintain (I-75 Segment 3 DBFM) Project is part of the $629 million I-75 Modernization Project for the Michigan Department of Transportation that encompasses approximately 18 miles of freeway from north of M-102 (8 Mile Road) to south of M-59 and has a current daily traffic volume of 103,000 to 174,000.

The I-75 Segment 3 DBFM Project includes a large storage and drainage tunnel approximately 4 miles in length with an inside diameter of 14.5 ft. The project includes three main shafts ranging in diameter from 27 ft to 55 ft. Seven drop shafts will be constructed along the tunnel alignment to convey surface drainage to the newly constructed tunnel via connecting adits at the tunnel elevation. The tunnel depth varies from 50 to 110 ft below ground elevation. It is anticipated that the entire alignment will be in stiff clay. The tunnel will be constructed with a non-pressurized face Herrenknecht TBM and lined with precast concrete segments.

The project encompasses modernization of approximately 5.5 miles of the I-75 freeway with service drives. The project includes the addition of one general purpose lane in each direction from 8 Mile Road to 12 Mile Road, the addition of an HOV lane in each direction, reconstruction of the existing freeway lanes and the replacement of 28 structures. A new pump station will ]be added at the George W. Kuhn Retention Treatment Facility (GWK RTF). NTP was issued in May. Tunnel substantial completion is anticipated for September 2022. The project is in the design phase, however some geotechnical investigation work and preconstruction survey activities are underway. Construction activities is anticipated to start in August 2019.

Project Developer: Oakland Corridor Partners; Design Build Contractor: MI 75 Constructors; Tunnel Designer: AECOM Great Lakes; Geotechnical Investigation/ Shaft Designer: NTH Consultants; TBM: Herrenknecht.

Project Personnel: Project Sponsor: John T. DiPonio; Project Manager: Mina M. Shinouda; Safety Manager: Timothy Bakers; Developer’s Project Manager: David Nachman; D&C Contractor’s Project Manager: Virgil Klebba; AECOM Design Manager: Sean Kelsch; AECOM EOR: David Mast; NTH Project Manager: Jason Edberg

MISSOURI

St. Joseph

Blacksnake Creek Stormwater Separation Improvement Project
Super Excavators Inc.
The work for this $26.9 million project for the City of St. Joseph Department of Public Works generally consists of the construction of 108-in. diameter concrete precast segment lined 6,648-ft long tunnel, 37-ft diameter baffle drop shaft, 48 ft of near surface reinforced concrete box culvert, 2-ft diameter vent shaft, 181 ft of 90-in. diameter open-cut steel pipe installation, 125 ft of 90-in. jacked steel pipe, an energy dissipation structure, site restoration, and performance of other associated works. Notice to proceed was issued on July 17, 2017. Scheduled Completion is October 2019.

The TBM is now 100% launched and 514 segment rings have been installed totaling 2,056 lf. 95% of all the segments have been delivered to the project site from CSI (Concrete Systems Inc.). The work is completed at the energy dissipation structure which was critical to Milestone 1 on the project. This work was completed two months ahead of schedule. The drop shaft excavation (receiving shaft) is 100% completed. This is a 44-ft ID secant shaft with a depth of 60 vf. The concrete subcontractor, Enerfab, has begun the concrete work for the drop structure at the receiving shaft.

This is the first use of an EPB machine provided by Lovsuns in the United States. The tunnel segments are being manufactured utilizing BarChip 54 synthetic fiber. This is the first time segments have been constructed in this manner in the U.S..

Engineer: Black & Vetch Corporation; Key Project Personnel: Mike Garbeth, Senior Project Manager; Gregg Rehak, VP.

NORTH CAROLINA

Cary

White Oak Creek Greenway
Turn-Key Tunneling, Inc.
The White Oak Creek Greenway project for the Town of Cary consists of the construction of approximately 0.5 miles of pedestrian improvements consisting of approximately 1,191 lf of concrete greenway, 102 lf of 14-ft diameter pedestrian tunnel under CSXT railroad, 916 lf of concrete boardwalk, and 355 lf of concrete sidewalk. The project also includes pedestrian improvements to the Davis Drive and Park Village Drive intersection, minor utility construction, grading, drainage, paving, erosion control and landscaping. The project is estimated to start Aug. 19, 2019, with an estimated date of completion of Oct. 25, 2019.
Engineer: Kimley-Horn & Associates; Contractor: Crowder Construction Co.; 14-ft Shield by Tunnel Shields & Equipment.

Key Project Personnel: Turn-Key Tunneling, Inc – Project Manager – Brian Froehlich, PE; Crowder Construction Company – Project Manager – Seth Bennett.

Durham

Eno River Outfall
Bradshaw Construction Corp.
Tunneling is complete on this project, which consisted of a 260-lf microtunnel of 75.4-in. OD steel casing. Subsurface conditions ranged from silty sand to competent rock. Project Manager: Mike Wanhatalo.

Greensboro

Young’s Mill Outfall
Bradshaw Construction Corp.
Bradshaw has begun construction on a project consisting of two microtunnels of 430 and 420 lf under roadways and an interstate highway. The jacking pipe will be 60-in. welded steel casing with 36-in. DIP sewer. Subsurface conditions will be mixed-face and mixed reach from silt to competent rock. Project Manager: Mike Wanhatalo.

OHIO

Cleveland

Doan Valley Relief and Consolidation Sewer
Triad Engineering and Contracting Co.
This $13.5 million project for the Northeast Ohio Regional Sewer District includes 3,137 lf of 72-in. diameter sewer via trenchless methods (2,007 lf by conventional two-pass methods, 1,130 lf by microtunneling). Also included is 1,475 lf of 48-in. sewer by open-cut methods, three flow control structures, eight manholes, one cast-in-place manhole and modification of one regulator structure. Ground conditions vary from shale bedrock to clay till, sandy clay and some sand seams with water. As of April, three shafts are excavated and the MTBM holed out. The conventional tunnel excavation from DVRCS1 to S-1 is underway.
Project Personnel: NEORSD Construction Manager: Jim Jones; NEORSD Construction Supervisor: Anthony Vitale; Tunnel Designer: AECOM: Dave Mast, P.E.; Triad – Project Manager: Philip Kassouf P.E. ; Project Superintendent: Rick Chipka Jr.; Tunnel Superintendent/Engineer: Brad Kassouf. Assistant Project Engineer: Art Hanus.

Cleveland

East 140th Consolidation and Relief Sewer
Triad/McNally JV (Triad Engineering and Contracting Co; C&M McNally Underground)
This $69 million project for the Northeast Ohio Regional Sewer District comprises 14,000 lf of 60- to 84-in. tunnel, eight access shafts, 6,800 lf of 12- to 54-in. diameter consolidation and relief sewers, three detention basins, 12,000 ft of 12- to 54-in. storm sewers, regulator improvements, and junction chambers. All tunnels are completed and lined. Junction chambers and connecting structure work is continuing. The outfall is complete. Site restoration is underway. Live sewage flow connections are waiting on the Dugway Storage Tunnel activation. Final completion is expected by September 2019.

Project Personnel – NEORSD Construction Manager: Jim Jones; NEORSD Construction Supervisor: Scott Keith; Tunnel Designer: DLZ: Tom Hessler; JV Manager: Cliff Kassouf; Assistant JV Manager: John Teahen; Project Manager: Phil Kassouf; Equipment Manager: Rick Chipka; Tunnel Superintendent: James Lowery.

Cleveland

London Road Relief Sewer
Triad/McNally JV (Triad Engineering and Contracting Co; C&M McNally Underground)
Triad/McNally JV is building 10,700 lf of tunnel between 7- and 9.5-ft bored diameter for the Northeast Ohio Regional Sewer District. Also included in the $39.6 million project are six shafts, eight diversion structures, junctions and manholes, modifications to six regulators, and 870 lf of sewers by open-cut. Mobilization is completed. Five shafts are excavated. The first TBM reach is nearly excavated.

Project Personnel: NEORSD Construction Manager: Robert Auber; NEORSD Construction Supervisor: Matthew Waite; Tunnel Designer: Rory Ball, Mott MacDonald; JV Manager: Cliff Kassouf P.E.; Assistant JV Manager: John Teahen P.E.; Project Manager: Philip Kassouf, P.E.; Tunnel Superintendent: James Lowery; Project Engineers: Matthew Bennett, Brad Kassouf.

Cleveland

Westerly Storage Tunnel
Jay Dee-Obayashi
This $135 million CSO project for the Northeast Ohio Regional Sewer District Board includes approximately 9,600 lf of 25-ft ID tunnel excavated in rock and supported with a bolted, gasketed, one-pass steel fiber reinforced concrete segmental lining. The project was awarded in March 2018 and is approximately 25% complete.

Recent activities include:

Shaft excavation at site WST-1:

• Approx. 8,000 cy of soil excavated to a final soil depth of 93 ft.
• Approx. 3,800 cy of rock excavated to a current depth of 144 ft. Rock excavation in shale approx. 37% done.
• Overall shaft excavation 63% done.
• Installation of support of excavation for the soil portion of shaft WST-2:
• Eight approx. 172 ft deep unreinforced slurry wall panels
• Approx. 2,100 cy of concrete

Shaft excavation at site WST-3:

• Approx. 12,000 cy of soil excavated to a final soil depth of 146 ft.
• Approx. 2,400 cy of rock excavated to a current depth of 186 ft. Rock excavation in shale approx. 63% done and currently on hold for starter tunnel excavation.
• Overall shaft excavation 88% done.

Starter tunnel excavation at site WST-3:

• Started excavation in shale with excavator/roadheader in April. Currently 5% done.

Tunnel Designer: Stantec Mott MacDonald Westerly JV; Construction Manager: NEORSD; Major Subcontractors: DiGioia-Suburban Excavating (open cut and misc. site work); Nicholson Construction Co. (Shaft SOE); Marra Services Inc. (shaft excavation at two sites); Northstar Contracting Inc. (concrete structures); TBM: Lovsuns.

Personnel: Deputy Director of Engineering and Construction (NEORSD): Doug Gabriel; Large Tunnel Construction Manager (NEORSD): Robert Auber; Senior Construction Supervisor (NEORSD): Ryan Sullivan; Project Sponsor (Jay Dee-Obayashi): Tim Backers; Deputy Project Manager (Jay Dee-Obayashi): Nate Long; Project Engineer (Jay Dee-Obayashi): Lisa Smiley; General Superintendent (Jay Dee-Obayashi): Jerry Pordon.

Columbus

Blacklick Creek Sanitary Interceptor Sewer

Blacklick Constructors (Michels/Jay Dee)
The $108.9 million project for the City of Columbus includes a tunnel approximately 23,000 ft in length with 40 to 140 ft of cover. The segmentally lined tunnel has been excavated using a Herrenknecht EPBM. A short section of the alignment was constructed by open-cut prior to the launch of the machine. The tunnel is lined using a 4-ft long, bolted and gasketed precast concrete tunnel liner manufactured by Technopref. The project includes 12 shafts, hydraulic drop structures, a passive odor control vault and appurtenances.
NTP was given to Blacklick Constructors on May 11, 2016. Tunneling started in April 2017. Tunneling was completed in September 2018, three months ahead of schedule. Construction of project’s largest concrete structure, a 140-ft deep, 14-ft ID drop structure with 26 baffles was completed in a little under 4 months which led to achieving Substantial Completion with Beneficial Use to the Owner on April 4, 2019, 436 calendar days ahead of schedule. Work remaining to complete is the surface restoration of the shaft sites. Blacklick Constructors has demobilized all its equipment.

The Design Tunnel Axis closely followed the alignment of one of Franklin County’s busiest thoroughfares. The TBM tunneled through rapidly varying glacial and alluvial materials, tills, boulders, sand, fill and shale; with a hydraulic conductivity exceeding 10-2 in some soft ground sections.

Design/Consultants: EMHT, Aldea Services, AECOM; Construction Manager: Black & Veatch; TBM Manufacturer: Herrenknecht.

Key Project Personnel: Ed Whitman, Project Manager; Ron Klinghagen, General Superintendent; Amanda Kerr, Project Engineer; Peter DeKrom, Survey Manager; Superintendents, Engineers, and Safety: Joel Sostre, Jason Keys, Mike Stucky, Max Ross, Nick Farrington.

TEXAS

Dallas

Mill Creek/Peaks Branch/State Thomas Drainage Relief Tunnel Project
Southland/Mole JV
This $206.7 million project for the City of Dallas involves 26,385 lf of 32-ft, 6-in. OD tunnel (30-ft ID) and seven shafts ranging from 120 to 200 vf. Tunneling will occur primarily in Austin Chalk with excavation via Main Beam TBM and roadheader.

As of January, the project was 22% completed by duration. The excavation of launch shaft was completed to 120 vf, and excavation of the 39-ft diameter horseshoe starter tunnel was completed. Excavation of the three 22- to 25-ft diameter intake shafts has begun. TBM delivery and surface assembly/commissioning has started. In total there are six working sites within the city.

Owner: City of Dallas; Lead Designer: HALFF; Tunnel Designer: COWI; CM: Black and Veatch; TBM: Robbins; Subcontractor: Oscar Renda Contracting.

Key Project Personnel: SMJV Operations Manager: Kent Vest; SMJV Senior Project Manager: Travis Hartman; SMJV Project Manager: Quang D. Tran, P.E.; SMJV Deputy Project Manager: Nick Jencopale; SMJV QC Manager: Matt Jackson.

SOUTH CAROLINA

Charleston

Spring/Fishburne Drainage Improvements Project; Phase 3, Tunnels & Shafts
Jay Dee Contractors Inc.

This $33.6 million project for the City of Charleston comprises 8,250 lf of 8 to 12 ft finished CIP storm water conveyance tunnel, two 30-ft ID and two 20-ft ID lined shafts and 8 adit tunnels that connect to existing drop shafts. The project is currently 77% complete, all tunnel and adit excavations are 100%. CIP tunnel lining is about 10% complete. The four shafts are 98% complete, with only the precast covers to complete. NTP was issued July 5, 2016. Estimated completion is March 2020.

Engineers: Davis & Floyd and Black & Veatch; Construction Manager: Black & Veatch; TBM Manufacturer: Lovat; Key Personnel: Project Manager: Dave Stacey; Project Engineer: Jeff Kolzow; Project Supt.: Louie Shapiro; Construction Manager: Stephen O’Connell; Resident Engineer: Kyle White.

Greenville

Reedy River Basin Sewer Tunnel
Super Excavators Inc./Cooperativa Muratori Cementisti JV
The Reedy River Basin Sewer Tunnel for Renewable Water Resources (RE-WA) involves 6,000 lf of 130-in. ID rock tunnel with 84-in. carrier pipe (Hobas CCFRPM Pipe) grouted in place. Tunnel depth ranges from 40 to 130 ft below ground surface. There is a 40-ft ID by 40-ft deep launch shaft and 30-ft ID by 130-ft deep receiving shaft. The tunnel to be mined in intact Gneiss bedrock using a double shielded rock gripper TBM manufactured by Lovsuns Canada. Shaft construction to consist of liner plate and rock dowels with wire mesh. The project also includes 1,600 lf of 60-in. and 42-in. upstream and downstream connecting sewer as well as several junction chambers, screening/diversions structures along with odor control facilities.

The project is on schedule. The 60-in. river crossing was completed during winter. Work on the Junction Chamber and Diversion Structure CIP work is finishing up. Crews are currently constructing the 14-ft arched set starter tunnel, which is now more than 25% complete. Tunneling is scheduled to begin summer of 2019.

The bid value of the project was $39.5 million. NTP was issued March 5, 2018, with completion scheduled for May 1m 2021.

Tunnel Designer/CM: Black & Veatch; Equipment – Komatsu, Terratech, Robbins; Subcontractors/Suppliers – Chardon Concrete (Concrete Structures), Pacific International Grout (Cellular Grout), Hobas Pipe (Tunnel Carrier Pipe).

Key Project Personnel: Justin Kolster – Senior Project Manager, Super Excavators/CMCRA JV; Rudy Marognoli – Project Manager, CMCRA; Stephen O’Connell – Construction Manager, Black & Veatch; Jason Gillespie – Senior Project Manager, Renewable Water Resources.

VIRGINIA

Richmond

General Assembly Bldg. Pedestrian Tunnel
Bradshaw Construction Corp.
Bradshaw has begun construction on a pedestrian tunnel connecting the new General Assembly Building to a parking garage. The project consists of a 56-lf, 15-ft, 1-in. by 21-ft, 1-in. SEM shotcrete tunnel. Subsurface conditions should be silty sand with gravel. Project Manager: Mike Wanhatalo.

Virginia Beach

PRS Reliability Upgrades – Providence Road
Bradshaw Construction Corp.
Bradshaw will soon begin work on a 182-ft tunnel in Virginia Beach for a 42-in. FRP sewer installation. The 60-in. Permalok steel casing tunnel will be installed behind a Herrenknect AVN-1200. Ground conditions are expected to be poorly graded sand beneath the water table. The project members include the Hampton Roads Sanitation District (Owner), RK&K (Engineer) and Ulliman Schutte Construction (Construction Manager), with Bradshaw performing as tunneling subcontractor. Project Manager: Jordan Bradshaw.

WASHINGTON

Bellevue

Downtown Bellevue Tunnel (E330)
Guy F. Atkinson
The $121 million project, part of Sound Transit’s East Link Extension, involves the construction of 1,985 lf of tunnel, 34-ft ID ovaloid, 12 to 48 ft deep; one maintenance shaft, 17-ft diameter x 50-ft deep located near the midpoint of the tunnel; connecting adit to enlarged tunnel section for permanent ventilation fans; and 250 lf of cut-and-cover structure. The tunnel was excavated in soft ground consisting of glacial till and outwash gravel, using sequential excavation method (SEM) including full top heading (three headings) as well as single side drift (6 headings).

Tunnel excavation was completed in July 2018. Construction of the mid-tunnel maintenance shaft and adit was completed October 2018 except for the stairs and concrete lid. Contractor is currently using the mid-tunnel shaft and adit for access and concrete delivery. The tunnel invert final lining is complete. Contractor is currently preparing the tunnel crown and walls for the installation of the spray applied waterproofing, followed by reinforcing and final lining. Construction of the South Portal cut and cover structure has also started. The project is 80% complete.

Large diameter soft ground light rail tunnel excavated using the SEM in downtown Bellevue, Washington. Utilized two Liebherr 950 to excavate the tunnel, and Normet Spraymec 8100 shotcrete robot to place the shotcrete lining. A spray applied waterproofing product is being used to waterproof the tunnel. A 12” thick cast-in-place final lining will be installed in the typical tunnel section. The expanded section of the tunnel and the tunnel center wall will use shotcrete as the final lining.

McMillen Jacobs Associates are subcontracted to HDR for CM services. Mott McDonald is the Tunnel Designer.

Key Project Personnel: Sound Transit: Chad Frederick, Principal Construction Manager, Ryan Lescouflair, Community Outreach. Atkinson: Archie Kollmorgen, Project Manager, Rohit Shetty, Tunnel Manager. Casey Henning, Assistant Project Manager. McMillen Jacobs Associates: Ted DePooter, Resident Engineer, Mun Wei Leong, Office Engineer. Tarr Whitman Group: Kris Mason, Schedule and Change Manager.

CANADA

BRITISH COLUMBIA

North Vancouver, BC

Second Narrows Water Supply Tunnel, Burrard Inlet Crossing
Traylor-Aecon General Partnership
The Second Narrows Water Supply Tunnel is a $286 million project for Greater Vancouver Water District that will improve reliability and increase capacity for Metro Vancouver to deliver drinking water throughout the area. NTP was issued Jan. 15, 2019 and final completion is expected in May 2023.

The projects consists of two shafts (18 m OD x 68 m and 10 m OD x 110 m) on either side of the Burrard inlet that are connected by 1,100 m of 5.8-m ID, 6.7-m excavated diameter segmentally lined tunnel that will be constructed with a mix shield TBM. Ground improvement includes a safe haven constructed using ground freezing 400 m into the drive. Three permanent water mains (2 @ 2.438m, 1 @ 1.524 m) will be installed within the tunnel, up both shafts and into large underground valve chambers atop each shaft.
Geology consists of permeable and variable soft ground containing a high percentage of cobbles and boulders with a transition to weak rock over the final 300 m of the drive. Face pressures of up to 7 bar are anticipated and hyperbaric intervention via saturation diving is planned.

Initial site preparation is complete, mobilization for slurry wall installation at the north shaft is underway and production excavation was to begin in May.

Owner: Metro Vancouver (PM: Allen Mitchell, DPM: Mark Qian); Tunnel Designer: McMillen Jacobs (Andrew McGlenn); Construction Manager: Mott MacDonald (CM: Richard Brydon, DCM: Ian Whitehead); Contractor: Matt Burdick, Andrew Rule, Erica Bailey.

Subcontractors: Herrenknecht (TBM); Schauenburg (slurry treatment plant); Malcolm-Petrifond JV (slurry wall); Keller North America (ground freezing); Ballard Marine Construction (hyperbaric services); Northwest Pipe (pipe supplier); MSE Precast (precast segment supplier).

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On May 23, 2019, a celebration was in order: The last of six 8.93 m (29.3 ft) diameter EPBs from The Robbins Company had completed excavation at Lot 4 of Mexico City’s Tύnel Emisor Oriente (TEO), a feat marking the completion of 10 years and 62.1 km (38.6 mi) of tunneling.

“We are proud of having successfully finished the excavation, despite all the adversities we faced, such as large inflows of water, hydraulic loads and constant changes in geology. We solved these by adapting the excavation mode according to each type of geology found,” said Hector Arturo Carrillo, Machinery Manager for Lot 4 contractor Carso Infraestructura y Construcción (CARSO).

Despite multiple challenges, the operation achieved a project record of 30 m (98 ft) in one day, and a high of 528 m (1,732 ft) in one month. It’s a result that, Carillo says, has much to do with the continuous conveyor system being used for muck removal.

“It should be noted that our advance rates were achieved thanks to the great Robbins conveyor design,” he said. “The tunnel conveyor was composed with elements such as the booster, vertical belt, curve idlers, and advancing tail piece, as well as elements on the surface. Personally, I think it is a great, admirable system that has helped us achieve the TBM’s performance.”

The breakthrough was the latest and greatest milestone for an urgently needed wastewater project that spanned some of the most difficult geology ever encountered by EPBs. The 10.2 km (6.3 mi) long Lot 4, running from Shaft 17 to Shaft 13 at depths of up to 85 m (280 ft), included sections of basalt rock interspersed with permeable sands with high water pressure.

“Our machines had to go through the worst geology, but they were designed for it,” said Roberto Gonzalez Ramirez, General Manager for Robbins Mexico, of the three Robbins EPBs and continuous conveyor systems used on Lots 3, 4, and 5 of the project.

All of the machines were designed for water pressures from 4 to 6 bar, with mixed ground, back-loading cutterheads to tackle variable ground conditions. High pressure, tungsten carbide knife bits could be interchanged with 17-in. diameter carbide disc cutters depending on the geology. Other features included man locks and material locks designed to withstand pressures up to 7 bar, a redesigned bulkhead, and Hardox plates to reinforce the screw conveyors as well as removable wear plates to further strengthen each screw conveyor flight. The rotary union joint was redesigned to improve cutter change times during cutterhead interventions, while a new scraper design offered more impact resistance in mixed ground conditions with rock.

RELATED: Robbins TBM Overcomes Multiple Caverns to Make Breakthrough

The Lot 4 TBM was assembled in the launch shaft No. 17 and commissioned in August 2012, with the bridge and all the back-up gantries at the surface. Two months later in October 2012, after advancing 150 m (490 ft), the machine and its back-up were completely assembled in the tunnel. One month later, the continuous conveyor system was installed and running.

After 405 m (1,328 ft) of excavation, the presence of rocks, scrapers, parts of the mixing bars and other wear materials in the excavated muck prompted a cutterhead inspection. With high pressure up to 3.5 bars, it was determined that a hyperbaric intervention was necessary, and on June 2, 2013 the first hyperbaric intervention through an EPB in a tunnel was performed in Mexico. However, these interventions were done at great cost and proved to be time-consuming. After about 50 hyperbaric interventions the remainder of the project’s interventions were done in open air.

“The interventions carried out in atmospheric mode were the biggest challenge. The great influx of water tested the limits, because we were excavating on a decline. In all of these interventions we had to implement a double pumping system, at both the TBM and the shaft,” said Carrillo.

Despite the challenges of pumping water at volumes up to 180 l (48 gal) per second and cleaning fines from the tunnel each time the operation was performed, atmospheric interventions were still lower in cost and quicker than those done at hyperbaric pressure.

Even when conditions were tough, Carrillo felt his operation was well-supported by Robbins Field Service: “Robbins were always present giving ideas and contributing all their experience to solve the problems. One of the most recent examples, almost at the end of this project, was where the machine encountered a blockage to the shield and could not move forward. It became necessary to implement the exceptional pressure hydraulic system, reaching a pressure range of 596 bar on 28 thrust cylinders. Robbins personnel helped us during all that time and we were able to get through it.”

RELATED: Robbins TBM breaks through nearly One Year Early in Nepal

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Brokk, the world’s leading manufacturer of remote-controlled demolition machines, delivers a sleek, low-profile design and impressive power-to-weight ratio with the new MMB326 hydraulic drifter rock drill attachment from TEI Rock Drills. This versatile attachment seamlessly pairs with the Brokk 300 and allows for drilling multiple sizes of holes — up to 3 in. — in concrete, rock and compact soil. The attachment is manufactured with a lightweight, compact TE326 drill head featuring patented technology to improve longevity and productivity.

“The MMB326 and Brokk 300 combination provides convenience and enhanced efficiency for operators,” said Peter Bigwood, vice president of sales and marketing at Brokk Inc. “We are continuously striving to help our customers maintain productivity and safety, which is why we partnered with TEI Rock Drills to develop an attachment to meet those requirements — even while drilling into hard rock in confined areas.”

At just under 30 in. long, the MMB326 delivers 200 foot-pounds of impact energy at 3,480 blows per minute. The drill also produces 250 foot-pounds of torque and reaches rotation speeds of up to 250 rpm, which makes it a more accurate and faster alternative to jackleg drilling through brick, concrete and rock. The combination also eliminates fatigue caused by operating the heavy manual tools and promotes safety by allowing operators to stand farther away from the drilling site.

The drill head itself (TE326) is a versatile hydraulic drifter that incorporates TEI’s patented Automatic Stroke Adjustment (ASA) technology. The high-frequency and smooth operation —provided by the ASA technology — prolongs the drifter and tool life, increasing productivity and profits for the user by reducing downtime and parts costs. Additional features, such as variable rotation speeds up to 250 rpm, help to minimize the risk of jamming, while the reversible rotation motors deliver high torque to ensure powerful drilling.

RELATED: Exhibitors Packing for RETC 2019

The MMB326 offers an expanded hole range up to 3 in. (76 mm) in diameter. It uses a 360-degree positioner for drilling in a variety of positions. The attachment can be used with a manual centralizer for rock drilling or with a hydraulic clamp for extension drilling and roof bolting. It’s available in 5.9-ft (1.8-m) or 7.8-ft (2.4-m) mast lengths.

The MMB326 attachment is a ready-to-use option that doesn’t need to be modified before configuring to a Brokk machine. The attachment can be integrated directly with the Brokk controls, allowing workers to operate the Brokk and MMB326 simultaneously. This adds convenience and efficiency, as well as frees up an extra worker who normally may be required to operate the second set of controls.

The drill attachment is quieter than pneumatic handheld alternatives, allowing construction crews to use the equipment in locations governed by noise-control ordinances, such as in and around apartment buildings, high-rise towers and other residential areas.

Upon purchase, a certified TEI technician will set up the attachment on the Brokk machine. If required, operational training can be provided.

The MMB326 drill attachment complements other Brokk attachments — heightening versatility — and was designed to be used in conjunction with the Darda C20 Splitter for rock breaking applications.

RELATED: Brokk Opens New Demonstration and Service Center in Missouri

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As the popularity and use of Geotechnical Baseline Reports (GBRs) on tunnel projects grows, we often find ourselves being asked to provide a GBR for projects with little understanding by owners of what a GBR is and how it should be used. In this article, we answer the question that continues to surface when discussing tunneling projects with owners: What’s the deal with GBRs?

GBRs are becoming standard for tunnel projects around the United States yet are still somewhat of a mystery to many owners and engineers working on their first tunneling project. Even when a GBR is utilized on a project, there is often still confusion by owners regarding its purpose, use, incorporation into contract documents, and use in evaluating differing site conditions.

So, what is a GBR? A GBR is a contract document used to allocate risks posed by subsurface conditions between the contractor and the owner for civil tunneling projects. GBRs were originally developed to promote more uniform bids and to provide a way to expedite resolution of differing site conditions claims.
Generally speaking, the spectrum for risk-allocation is juxtaposed by owners who desire to shed all risk of differing site conditions to the contractor, and by owners who accept all risk of differing site conditions. In most cases, neither of these extremes is in the owner’s best interest.

The purpose of a GBR is threefold:

1. Allow the design team a means to describe subsurface conditions that can positively or negatively impact both construction and construction cost
2. Attract qualified and competent contractors by providing a basis for preparing a bid and secondly, for resolving disputes related to claims of differing site conditions
3. Provide the owner with a contractual mechanism to manage geologic risk and the cost implications of that risk should it be realized during construction

Project Risk

Risk Management

In order to talk about GBRs, we must first talk about risk associated with underground construction. Risk is any event that will affect project goals if it does occur, with an emphasis on negative events with unwanted consequences. Risk is often described as the product of probability and consequence:

Risk = (Probability of Unwanted Event) x (Consequence of Unwanted Event)

Increasing either the probability or the consequence will increase the associated risk. Proactive risk management has become a necessity for underground construction where many construction variables are difficult to identify, classify or quantify. Effective risk management has been shown to help reduce cost overruns by acknowledging that risks are present and by equitably allocating risks. The figure below shows the benefits of risk management, particularly in the early stages of a project when costs to mitigate identified risks are the lowest.

Risk Registers

On underground construction projects, the potential individual risks with significant impacts are exhausting. A comprehensive project risk register is commonly used to identify specific risks, their cost, implications, and potential mitigation alternatives. Risk registers are powerful tools if used properly and embraced by the owner, engineer, and contractor during both the project’s design and construction phases.
Developing a risk register should never be done in a vacuum. Effective risk registers are often developed during workshops that include key stakeholders, are updated and revised throughout the design process, and serve as a live document for the duration of design and construction. Generally, project risks fall into seven main categories:

1. Geological
2. Technical
3. Contractual
4. Market
5. Environmental
6. Regulatory
7. Third Party

Analysis of the identified risks allows a project-specific ranking and prioritization of those risks. The table below outlines a qualitative risk rating using both probability and consequence severity.

Once a Risk Register is developed, the project team can establish mitigation options that will minimize negative impacts on project success. The mitigation options typically fall into the following categories:

• Risk Avoidance: change the project plan or eliminate items to avoid the risk.
• Risk Mitigation/Minimization: reduce the probability of the event occurrence or reduce the severity of the event consequences.
• Risk Transfer: convert responsibility for risk, usually financial, to another party such as a contractor or insurance provider, through mechanisms such as contracts, insurance policies, securitizations, performance bonds, etc. The GBR is an integral part of the risk-transfer process.
• Risk Acceptance: acknowledge and prepare for risk occurrence.

GBR as a Risk-Sharing Tool

Above all, GBRs are a risk-sharing tool for geologic risks. For tunnel projects, the focus of construction on a single point (i.e. the tunnel face) makes the ground conditions encountered of critical importance. It is impractical to gain a complete understanding of how the ground will behave prior to construction. This is due to the inherent variability of subsurface conditions and limitations of geotechnical exploration.

Historically, owners have attempted to mitigate risks inherent in underground construction by pushing all risk to the contractor. In this approach, the contract documents include the geotechnical report as information only, and the contractor is required to make their own interpretation of both the ground conditions and anticipated ground behavior. Since the contractor makes its own interpretation of ground conditions, the owner’s assumption is that there is little basis for submitting change orders or making claims. However, the reality is that the contractor does not “accept” risk; the contractor does “price” risk. The more risk that is pushed from the owner to the contractor, the higher the bids are likely to be as the contractors add contingencies to cover the risk of unknown ground conditions. This often results in owners paying for risks that “may” occur, rather than only paying for risks that “do” occur. If ground conditions are more adverse than the contractor expected, the contractor is likely to file a claim for subsequent damages anyway. The owner, who attempted to place the risk of such conditions on the contractor, is usually unwilling to pay for the claimed differing site conditions, and costly litigation may ensue. The litigation battle is often stalled as interpretations of the ground conditions and anticipated risks are formulated by the owner post-construction rather than during design.

Another potential consequence of contractually allocating risk to the contractor is that the “low bidder” contractor is often the one who does not recognize the risks or who has not priced the risks appropriately. The low-bid contractor may find itself in financial difficulty and might then look for construction short-cuts or attempt to re-coup losses by submitting claims. Experience has shown that transferring risk to the contractor does not result in reduced project cost, claims, nor a smoother construction project.

On the other hand, the owner should not be required to accept all risks of unknown ground conditions. While the owner “owns” the ground, the contractor is responsible for exercising its expertise to determine how best to complete the project successfully. The GBR is the industry’s current “best practice” approach to addressing the unknowns in ground conditions. By clearly communicating the anticipated ground conditions and behaviors and providing an interpretation of how those conditions will affect construction, the risk can be fairly allocated between both parties. The owner, as the originator of the GBR, establishes the level of risk they are willing to accept. In theory, if a subsurface condition and/or ground behavior is encountered that is more adverse than dictated in the GBR, the owner will pay the contractor for the additional construction costs. The contractor has the opportunity and the contractual obligation to price the work based on the risks allocated in the GBR. Unless subsurface conditions and/or ground behavior are more severe than those dictated, the contractor has no basis for a claim.

The Difference Between GBRs and Geotechnical Data Reports (GDRs)

Geotechnical Data Report (GDR)

A Geotechnical Data Report (GDR) is a compilation of factual subsurface data collected during a project investigation. Data are collected during borehole drilling, laboratory testing, test pit excavation, geophysical survey, geologic mapping, literature review, and other means that provide quantitative or objective data about the subsurface. The GDR contains factual data only; to the extent possible, biases introduced by persons making the observations and collecting data are removed by conforming to applicable ASTM standards.

The GDR provides objective data that a GBR author uses to interpret subsurface conditions. For example, a GDR may include borehole logs that show a soil/bedrock contact at various elevations as encountered during drilling. Whereas, the GBR may include a subsurface profile that shows a line connecting the soil-bedrock contact between multiple boreholes. Interpolating the soil-bedrock contact between boreholes is an interpretation and may be influenced by the experience of the person making the interpretation. The GDR is also limited by what it does not include. For instance, a small diameter borehole is likely to miss scattered boulders. As a factual report, the GDR will not report boulders in the subsurface. The GBR, as an interpretive document, might state that boulders will be encountered based on the opinion and experience of the GBR authors in the project vicinity.

GBR Baseline Statements

The GBR provides information about the anticipated subsurface, discussion of similar nearby projects if available, and a section on feasible construction methods and the potential problems these methods may encounter during construction. However, the GBR’s “baseline statements” (“baselines”) make the document unique. The baselines are a set of contractual assumptions about ground conditions and behavior. It is important to understand that a baseline is not necessarily directly consistent with the data generated by the subsurface investigations, rather it provides a specific set of ground conditions that should be used by contractors to bid the project. If the actual ground conditions encountered during project construction are either the same as, or more favorable than, the baselines, it is the contractor’s responsibility to execute project construction at no additional cost to the owner. If the actual ground conditions encountered during construction are more adverse than the baselines, it is the owner’s responsibility to reimburse the contractor for the negative financial impacts resulting from those conditions. It can be helpful to think of a baseline as a “line in the sand” as depicted below.

Baselines should provide the contractor with information necessary to bid and construct the project, while still allowing the contractor the freedom to choose viable means and methods. The following are examples of items that should be addressed by the baselines:

• What type of ground will be encountered?
• Where will different types of ground exist?
• How will the ground behave?
• Will the ground behavior change over time?
• Will groundwater be encountered? Where? How much?
• Will there be obstructions that will impact tunnel advance?
• Are there third-party considerations not covered in the specifications that will affect construction?

Baselines should be clear and concise, leaving no room for interpretation. A baseline should be quantitative and allow all parties to readily identify on which side of the “line in the sand” an actual condition falls. Some examples of poor and improved baseline statements are presented below.

Often, it is prudent to set a baseline at a level not consistent with the GDR based on knowledge about the geologic environment from other projects in the area or to be consistent with the owner’s desired risk-sharing strategy for the project. Some owners may be willing to accept more risk and therefore set baselines that are more optimistic than directly indicated by the project subsurface information.

Conversely, some owners may wish to minimize the potential for contractor claims for unanticipated ground conditions and therefore set baselines at the conservative upper edge of the identified project subsurface information. However, it is important that the baselines fall within a reasonable value with respect to the anticipated subsurface conditions to avoid the contractor ignoring baselines perceived as unreasonable; the position of unreasonable baselines has been upheld in the contractor’s favor in prior court cases.

GBR Usage

The Differing Site Condition (DSC) Clause

The GBR is the primary document that defines the ground conditions upon which the contractor and owner should consult when determining the validity of a DSC. For the GBR to be effective, a DSC clause must be included in the contract documents. This gives the owner and the contractor the legal means of identifying when changes in the ground conditions should warrant compensation. Standard DSC language includes two types of DSCs: Type 1 – ground conditions that are materially different than those presented in the contract documents, and Type 2 – ground conditions that are of an unusual nature and differ materially from those normally anticipated by a reasonable, intelligent and experienced contractor in a similar area or conditions. Along with the DSC clause is a section that formally instructs the contractor that they may rely on the GBR as data to be use/d during bidding and throughout the work.

The Deal with GBRs

GBRs are becoming the standard of practice for tunnel and trenchless projects in the United States and are powerful tools for controlling and allocating risk, leveling the playing field for contractors bidding the work, and drawing lines in the sand with respect to DSCs. The key to successful implementation of a GBR is owner education and incorporation into the GBR process, not only during design but during construction. A properly written GBR can save an owner money by reducing potential litigation costs and claims, and by providing contractors with critical information and interpretations necessary in developing a competitive bid for the project.

Authors
Robin Dornfest, PG, CPG, President, Lithos Engineering
Nate Soule, PE, PG, Vice President, Lithos Engineering
Ryan Marsters, PE, PG, Associate, Lithos Engineering

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Silicon Valley Clean Water (SVCW) announced June 6 the selection of a name for its TBM that will support the agency’s $495 million infrastructure program. The program includes rehabilitating 3.3 miles of the agency’s raw wastewater conveyance piping system, involving installation of a new gravity pipeline. Other projects in the program include three new or rehabilitated pump stations, and a new preliminary treatment facility at the wastewater treatment plant.

The tunneling machine, called “Salus”, after the Roman goddess of safety and well-being, will bore 2.4 miles under the Redwood Shores Parkway right-of-way in Redwood City, to make way for a new wastewater conveyance pipeline.

Rick Einsiedl, a 20-year resident of the Redwood Shores neighborhood in Redwood City, proposed the winning name following a naming contest launched by SVCW, which provides wastewater service to more than 220,000 residents and businesses serving Belmont, San Carlos, Redwood City and the West Bay Sanitary District. A three-member judge panel selected the name for the TBM from 34 entries.

“In a mining tradition that dates back centuries, it is considered good luck to give tunneling machines a name before they start work,” said Teresa Herrera, manager of SVCW. “SVCW appreciates the community’s enthusiasm and creativity during the naming contest. We look forward to welcoming Salus to Redwood City in July and for the tunneling work to commence.”

In Einsiedl’s contest submission, he wrote “Salus (Latin: salus, ‘safety,’ ‘salvation,’ ‘welfare’) was a Roman goddess. She was the goddess of safety and well-being (welfare, health and prosperity) of both the individual and the state. As a local project that befits the people this name seems fitting for the purpose, as well as a nod to the Romans who are credited with inventing modern plumbing and sanitary management.”

Built by Herrenknecht in Schwanau, Germany, the $18.2 million TBM will be arriving from Germany in July and is an alternative to more disruptive construction options. Sixteen ft in diameter and 650 ft long with all the support elements, it will arrive disassembled and the components will be reassembled underground before beginning two years of work constructing the wastewater conveyance pipeline.

Salus will first construct a 1-mile segment of tunnel to connect the new gravity pipeline with a new force main installed on Inner Bair Island. Then the TBM will install a second section of tunnel starting from a launching shaft located north of the San Carlos airport, and extending the tunnel to SVCW’s treatment plant.

RELATED: Silicon Valley Clean Water Taps Microsoft Tools to Aid PDB Tunnel

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Equipment Corporation of America (ECA), a leading distributor of specialty foundation equipment, has named several Service Managers at its branches in the United States and Canada.

Chris McCune has been promoted to Service Manager at ECA Pittsburgh after working as a Service Technician at the branch since 2016. McCune’s background in foundation and directional drilling combined with his professionalism in dealing with customers made him the best choice for this role. McCune’s goal is to mentor younger employees and current technicians to help them follow the same successful path he followed.

Peter Kassaris has been promoted to Service Manager at ECA Canada Company. Through hard work and dedication, he was promoted to the senior technician role within 15 months of being hired. Kassaris had already amassed eight years of experience in the foundation construction industry when he came to ECA Canada in September 2017. Kassaris aims to build the best service department in the Canadian foundation construction industry.

Trey Carver has been promoted to Service Manager at ECA Florida. He began his career in 2006 as an Equipment Technician at Pile Equipment. Carver joined the team as a Technician when ECA purchased the Florida-based company in 2015. He worked his way up from Technician to Foreman, and in four short years, was promoted to Service Manager of ECA Jacksonville in February 2019. Carver strives to maintain strong customer relations through professionalism and exceptional customer service, and aspires to build a strong, self-sufficient service department capable of handling any potential issue ECA’s customers might encounter.

Kevin “Buddy” Austin began his career in 2006 as a drilling rig operator in the foundation construction industry and has since been promoted to Service Manager at ECA Washington. He joined ECA in 2011 as a Service Technician and quickly advanced into ECA Washington’s lead Technician role. Austin’s motivation, professionalism and dedication to both customers and fellow employees resulted in his promotion to Service Manager. He has become the go-to-guy for all questions regarding KLEMM because of his specialized technical knowledge of this product line. His 13 years of experience, focused on building and maintaining relationships with ECA’s customers and vendors, will help ensure the future of the company and its employees.

Rich Weinstein joined ECA Philadelphia as Service Manager in April 2019. He came to ECA with 17 years of experience in operations, service, parts and warranty management. With his comprehensive experience, Weinstein aims for the service team to be even more responsive, resulting in less machine downtime and a better overall experience with ECA. He also plans to spend more time in the field and visiting customers to develop a deeper understanding of their needs.

RELATED: ECA Celebrates 100-Year Anniversary

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Tunneling and underground construction in urban areas is increasing throughout the world for various reasons. This requires handling of complex challenges for safe construction and to minimize impacts on existing buildings, structures, utilities and the public.

Tunneling in urban areas frequently requires construction with shallow cover, in difficult ground conditions of soft soils and mixed ground, with high groundwater infiltration, frequently in close proximity to major sensitive structures and historic buildings. The potential impact of tunneling on structures and on surface traffic, adjoining businesses and everyday life of the residents is high.

AECOM provided management services for the 49ft (14.9m) diameter TBM that successfully excavated a double deck highway tunnel along the historic Bund District of Shanghai

The Needs for Underground Space in Urban Areas

According to UN reports, the world population in 2017 was estimated at 7.5 billion people with anticipated growth in population by 2050 to 10 billion people. There are 22 cities with population of 10 to 20 million people and 34 cities with population between 5 and 10 million people.

The global trend of urbanization and industrialization has caused migration from rural areas to cities. Mega cities are growing in population and the number of mega cities is increasing. For example, Tokyo is the most populated city in the world with 32 million and Seoul, Delhi and Mexico City have populations of over 20 million each. As a result of the human growth and the concentration of populations in centralized urban areas, the need for infrastructure and transportation facilities is increasing.

According to the International Tunneling Association, the tunnel and underground market is estimated at $7.5 trillion. It is further predicted that the tunnel and underground construction market is expected to outpace other heavy civil/infrastructure markets.

Some of the drivers for the increase in underground construction in urban areas beside population growth and the number of large cities are:

• The growing needs for sustainable, efficient, economical and environmentally friendly transportation and infrastructure systems
• The need to reduce environmental, property and visual impacts, and to minimize surface disturbance
• Government regulations requiring cleanup of waterways by dealing with combined sewers in older cities
• The need of resiliency of cities due to climate change
• Protection of low-land areas from flooding (diversion and flood control tunnels), and
• The public demands underground construction for more noble uses of the surface area and the economy and advancement of technologies supports the underground use.

Recent advances in tunneling technologies, improvement in safety, efficiency in implementation, better risk management and the ability to build larger diameter tunnels in more complex geology enable the construction of many newer underground facilities that were previously not possible or having high risks.

Chinatown Station cavern excavation using multiple drifts and extensive pre-support and ground improvement measures.

Challenges of Tunneling in Urban Areas

Tunneling in urban setting presents a number of unique challenges. A typical urban setting will include the presence of major roadways, potential shallow ground cover, soft ground conditions and potentially mixed ground, existing or abandoned foundations and buried structures, and large intricate networks of wet and dry utilities. Additionally, space constraints in urban settings magnify the challenge of implementing tunneling in such a manner as to avoid inducing displacements damaging to adjacent facilities, structures and utilities.

The use of cut-and-cover construction will further impact traffic, require utility relocation and/or support in place, affect businesses and expose the public to noise, dust and vibration and impact the people quality of life during construction.

However, these challenges can be addressed with carefully designed tunneling method, the use of the latest technologies in tunneling, the use of prudent excavation and support sequencing, implementation of ground improvement and a robust instrumentation and monitoring program that will identify potential issues early and implement corrective actions. With a risk mitigated approach during the design phase, and the use of the latest TBM technologies, tunneling has proven successful in complex urban settings.

Construction of the Jubilee Line at the Westminster site in the heart of London, AECOM’s engineers had to address all the challenges of urban construction at a historic site in a major city

TBM Tunneling in Urban Areas

Prior to the advent of pressurized face TBMs, urban tunneling was confined to ground conditions with sufficient stand-up time to allow the tunnel to be advanced and support erected. Tunneling below the groundwater table was limited to strata that could be stabilized by the application of compressed air to control seepage through the face. Ground improvement techniques including permeation grouting and ground freezing were used to stabilize water bearing non-cohesive soils but this was confined to short drives due to their expense.

In 1964 John V. Bartlett patented the Bentonite Tunnel Boring Machine. This TBM was the predecessor of all pressurized face TBMs and allowed safe and economic tunneling in water bearing non-cohesive soils. Earth Pressure Balance (EPB) TBMs were developed in Japan in the 1970s based in part upon experience of slurry TBM operation. EPB operation was initially confined to soils with fines content of 20% or greater. Now the operational ranges of slurry and EPB TBMs overlap significantly due to the use of additives with both types. Further development of TBM cutterhead design incorporating disc cutters and soft ground cutting tools has extended the range of the pressurized face TBMs to mixed faces of soil and rock and, on occasion, full face rock.

RELATED: Building a Better Future in Los Angeles

Now pressurized face TBMs are employed under cities across the globe excavating tunnels for transit systems, rail, sewer networks, highways, power distribution and other functions.

In Malaysia, slurry TBMs tackled karstic limestone, residual soils and mine tailings to construct the Klang Valley Mass Rapid Transit (KVMRT) Red Line under highly developed area, the first use of the variable density slurry TBM. In Shanghai a 49-ft diameter EPB TBM was used to bore a twin deck highway tunnel under the historic Bund in normally consolidated sediments and fills with less than 30 ft of cover in places passing over operational subway tunnels with 5 ft of separation. In Hong Kong, a 19-ft diameter articulated shield slurry TBM bored through full face granite, mixed face and residual soil negotiating 500-ft radius curves to construct the Lai Chi Kok Storm Water Tunnel. In Pittsburgh a 23-ft diameter slurry TBM bored the two tubes under the Allegheny River for the LRT North Shore Connector designed by AECOM through fluvio-glacial deposits and coal measures at a gradient exceeding 8% and very tight horizontal curve, one of the early uses of slurry TBMs in the Americas.

17.6 m TBM for the TM-CLK undersea tunnel, Hong Kong

TBM Technologies Enable Larger Tunnels

Before the introduction of closed face pressurized TBMs, tunnel diameter was limited in part by the strength of the ground and by the need to have sufficient ground cover to mobilize ground arching. These together with the face area determined the stand-up time of the tunneled opening and allowable advance without support. The application of face pressure by a TBM has turned these requirements on their head. Ground strength and cover are important as they limit the maximum pressure that can be applied by the TBM without risk of ‘blow out’ of the tunnel, but face area is no longer as critical a consideration in determining face stability. Therefore the use of large diameter tunnel is increasing in situations where previously a twin-bore configuration would have been adopted. In some circumstances the feasibility of the single bore solution has allowed a project to proceed where lateral and alignment constraints ruled out a twin-bore configuration.

The Bund Tunnel in Shanghai could only be constructed as a single bore because a side-by-side twin bore could not fit the lateral constraints of the corridor. To date, a few single-bore, large-diameter tunnel have been constructed in urban areas, such as the Barcelona Metro Line 9 in Spain, the Alaskan Way project in Seattle, the Evergreen line in Vancouver, and the Chong Ming Tunnel connecting Shanghai with Chong Ming Island. As confidence is built in the operation of large-bore tunnels, they will become increasingly common due to the multiple advantages they hold over twin-bore construction, as can be seen in the new projects under design and or in construction such as Riyadh Metro and Paris Metro expansion.

Advantages of the single-bore option include the elimination of cross passages, sufficient space to accommodate in-line sumps and equipment rooms within the tunnel cross section and more efficient ventilation strategies. AECOM was instrumental in recommending and designing the largest diameter bored tunnel in the world that saved three years of construction, the Tuen Mun Chek Lap Kok Link (TM-CLK) Tunnel in Hong Kong at a diameter of 57 ft, 9 in. (17.6 m) which when completed provides direct connection to the airport.

Flexibility and Adaptability of SEM/NATM

Sequential Excavation Method (SEM) (or the New Austrian Tunneling Method (NATM)) has become the method of choice for tunneling in urban areas to construct complex underground structures such as metro stations, multi-track metro lines, rail crossovers, short road tunnels and underground road ramps in order to avoid cut-and-cover construction with its impacts on streets, utilities, traffic, businesses and the public.

Under these conditions and where complex and challenging ground conditions exist, underground construction requires a flexible design that can be executed effectively and safely, while minimizing impacts to existing structures. This specifically includes tunneling in running and flowing ground, tunneling under high water ingress, encountering mixed face conditions, low ground cover, presence of sensitive buildings and structures within the influence zone of the excavation, presence of boulders, abandoned foundations or uncharted utilities and complex geometrical configurations. SEM minimizes impacts on traffic and utilities/services throughout construction, reducing disruption to everyday life.

However, SEM in an urban setting presents a number of special challenges beyond what is discussed previously. Space constraints in urban settings magnify the challenge of implementing SEM tunneling in such a manner as to avoid inducing displacements damaging to adjacent facilities, structures and utilities. Such challenges can be addressed with carefully designed excavation and support sequencing, including potential ground improvement and a robust instrumentation and monitoring program.

RELATED: Skanska Awarded Final Heavy Civil Contract for East Side Access

For example, on the Northern Blvd Crossing in New York City as part of the East Side Access for which AECOM is the PM/CM, the tunnel was constructed using SEM accommodating a very large cross-section with a width of 60 ft, 4 in. (18.4 m) and height of 38 ft, 9 in. (11.8 m) under existing transit lines and with shallow cover and unfavorable geology of mixed glacial deposits below the water table. To enable the construction, the cross section was subdivided into multiple drifts and using ground freezing to stabilize the ground and enable safe construction.

For the Chinatown Station as part of the Central Subway project in San Francisco, and for which AECOM is also the PM/CM, the station was constructed in a highly developed area under a narrow street, congested businesses, residential dwellings and historic and institutional buildings. The station caverns were excavated in multiple drifts using pipe arch canopies as a pre-support. An extensive instrumentation and monitoring program was implemented and a compensation grouting system was used to deal with the settlement of buildings and utilities.

Multiple drifts and ground freezing allowed successful SEM construction of Northern Blvd Crossing.

Ground Improvement and Pre-Support Measures

With respect to SEM, ground improvement measures improve soil standup time during excavation and allow the installation of optimized initial support while providing safe excavation. Ground improvements also serve to control ground water, reduce ground loss and potential surface settlements and minimize the tunnel deformations during excavation. The variety of ground improvement techniques available are diverse and include dewatering, jet grouting, cementitious or chemical permeation grouting, compaction grouting, ground freezing, etc. In the scenario where settlement would potentially occur, compensation grouting can be used as a remedial measure to overcome tunneling-induced settlements. Instrumentation and monitoring are critical for detecting ground movement and implementing corrective measures.

Common methods of pre-support, which include spiling, pipe arch canopies and sub-horizontal jet grouting, act to improve the standup time of weak ground during and after excavation. In addition to minimizing risk during excavation, effective pre-support measures will minimize disturbance to in-situ ground during excavation, thereby limiting surface settlements. However, pre-support measures are only suitable for implementation when they have close contact with the ground. This is essential in order for the ground and pre-support elements to work effectively as a reinforcement integrated into the ground.

Instrumentation and Monitoring Measures

Instrumentation and monitoring are essential for safe and efficient tunneling. This is due to uncertainties in both the ground model and response of the ground, utilities and structures within the zone of influence of the tunneling.

It is common practice to monitor groundwater level (pore water pressure) and ground movement in addition to the movement of buildings and utilities. Short term lowering of groundwater can cause significant ‘immediate’ and irrecoverable settlement in normally consolidated soils. If pore pressures do not recover stiffer soils can consolidate for years after construction. Another potential consequence of dewatering is that timber piles supporting historic buildings can rot if exposed to air
Ground movement is a 3-D phenomenon and it is vital to monitor the ‘bow wave’ settlement in advance of the tunnel face. This allows adjustments to be made to TBM operating parameters (or to the face excavation in case of SEM) as it advances to ensure that the target volume loss is not exceeded. Standard practice is to use surface measuring points set out on a square grid along the alignment. The spacing of the monitoring points must be sufficient to define the shape of the curve as the location of the point of inflection in the settlement curve is as significant as the maximum centerline settlement. In addition to surface monitoring points multipoint extensometers installed in boreholes should be used to determine settlement at intermediate levels between the tunnel crown and ground level.

RELATED: AECOM Strengthens its Tunneling Position in North America

Buildings are not totally static structures and over their life they will have been subjected to movements caused by a number of external factors. These include wind loads, foundation movements, seasonal variations in temperature and adjacent construction. All of these, and other factors, may have left their mark in the form of cracks, sticking doors and structural damage. Therefore it is essential to carry out a condition survey of all structures within the zone of influence of the tunnel works. This survey should record all visible defects both superficial and structural. The objectives are to ensure that pre-existing defects are not attributed to the tunneling work and identify if the residual structural capacity is sufficient to accommodate the predicted ground movements.

It is a common practice to monitor building movement using total station systems. These comprise automatic reading theodolites that scan prism targets secured to the structure to determine changes in their position in 3-D space. The accuracy of these systems demonstrates that buildings are continuously ‘moving’ in response to seasonal effects. These include thermal expansion and contraction, and groundwater table fluctuation. The annual seasonal response of sensitive structures should be established before the start of excavation. Failure to do so could lead to false alerts, unnecessary stop work orders and remedial/protection works. The emphasis is always on monitoring movement and controlling it within acceptable limits. Where it is not possible to achieve this with good tunneling technique alone, consideration must be given to protection and mitigation measures. These include underpinning, protection walls, grouted blocks and compensation grouting.

The urban subgrade is packed with utilities ranging from power cables, communication cables to sewers and water mains. All are to some degree critical to the life of the city. The potential effect of tunneling on utilities is often the most problematic issue when planning major underground works. This is because not only are their locations and condition often unknown, but their exact locations are unknown and their ownership is diverse introducing numerous stakeholders to the project. Perversely, these stakeholders often have little interest in the project beyond ensuring ‘zero harm’ to their utilities. On occasion, this results in protection criteria that are either unnecessarily expensive to satisfy or extremely difficult to achieve in the field.

Concluding Remarks

Tunneling in urban areas is becoming highly viable as a result of advancement in technologies, application of safety measures, implementation of risk mitigation strategies, and efficiency in design and construction. Properly implemented, it will avoid cut-and-cover construction and its associated impacts on traffic, utilities, businesses and the public.

Detailed geotechnical investigations, good understanding of the ground behavior during tunneling, and a robust design are essential for successful tunneling in urban areas. In addition, a comprehensive instrumentation and monitoring system with predetermined threshold limits and potential remedial measures is crucial, along with pre-qualification of all involved parties. An engaged program manager with strong technical knowledge and effective communication and collaboration between the designer, contractor and owner’s representatives is vital, and a fair and equitable risk sharing mechanism through a well-thought out Geotechnical Baseline Report are essential elements for successful implementation of tunneling in challenging settings such as urban environments.

About the Authors

Nasri Munfah is the Director of Tunneling and Underground Engineering Center of Excellence of AECOM. He oversees the firm’s tunneling and underground projects and provides leadership in project pursuit and delivery, the development of innovative solutions, recruitment and the professional development of staff. With over 30 years experience in tunnleing in urban areas globally, he provides in-sight perspective of issues related to tunneling in urban areas.

Bob Frew is a world leading tunnel specialist with over 40 years of experience. He is highly experienced with tunnel construction using soft ground and rock TBM in urban environments. Frew is based in the United States but his experience extends worldwide. He has worked on tunnel projects in Australia, Europe, North America, Middle East, China and South East Asia.

The post Advances in Tunneling Overcome Challenges in Urban Areas appeared first on Tunnel Business Magazine.

Together, with the new 225 million-gallon-per-day Wet Weather Treatment Facility at Blue Plains, this 7-mile tunnel segment reduces combined sewer overflows by more than 80 percent

Although the rivers and creeks that meander through Washington, D.C., are often noted for their historical significance, a deeper story – fueled by inevitable progress – presents a challenge that even our forefathers could not have predicted.

For more than a century, only sewer systems with separate pipes for sewage and storm water have been installed in our nation’s capital. Prior to this however combined sewage and storm water pipelines were installed. In fact, about one-third of the District of Columbia has a combined sewer system, a distinction not unique in numerous other older cities. As these pipes aged and the population grew, combined sewer overflows (or CSOs) frequently occurred during intense rainfall when the combination of storm water and sewage exceeded the capacity of the sewer pipes. The result was an overflow to the closest body of water.

Because CSOs harbor bacteria and trash that can be hazardous for both people and nature, the District of Columbia Water and Sewer Authority (DC Water) is actively implementing its Long Term Control Plan (LTCP). The plan’s goal is to meet requirements established by the U.S. Environmental Protection Agency for pollution control and reduction of CSOs into nearby waterways. This exciting new chapter – a viable solution for present and future generations – will ensure protection of the environment today and for years to come.

The LTCP, deemed a far more desirable alternative to the combined sewage back-up in homes, businesses and roadways, is well under way. The first segment, DC Clean Rivers Project Division H – Anacostia River Tunnel, is one of several contracts in the overall plan of deep tunnels, sewers and diversion facilities, designed to capture overflows to Rock Creek as well as the Anacostia and Potomac rivers for treatment at the Blue Plains Advanced Wastewater Treatment Plant.

The Division H – Anacostia River Tunnel, which holds 100 million gallons of combined sewage and measures 23 ft in diameter, was commissioned in late March 2019. Together, with the new 225 mgd Wet Weather Treatment Facility at Blue Plains, this 7-mile tunnel segment reduces combined sewer overflows by more than 80 percent.

Construction of the Division H – Anacostia River Tunnel was launched in 2013 with the construction of six reinforced concrete slurry diaphragm wall shafts along the tunnel alignment. The walls provided initial support during shaft excavation and also formed part of the permanent structure.

Hobas supplied 120-inch, 1765-ton jacking pipe for this project although 600 tons of jacking force was all that was needed to complete the drives.

Making Connections

Next, microtunneling, a trenchless pipe installation performed by remote-controlled jacking, was used to insert the jacking pipes more than 100 ft below the ground under the CSX Railroad tracks and right of way to connect the CSO-018 outfall to the tunnel system. According to Hobas Pipe USA Commercial Manager Rob Epstein, the company supplied 320 ft of 120-in., 1,765-ton jacking pipe for this project. Manufactured by Hobas Pipe USA in Houston, Texas, Hobas CC-GRP jacking pipes are known for their smooth, non-absorbent exterior surface, tight outside diameter tolerances, high compressive strength and lightweight construction.

DC Water Resident Engineer Scott Shylanski said Hobas pipe was chosen for its availability and hydraulic considerations. “The machine selected by the contractor could not accommodate the specified diameter for RCP pipe,” he noted. “Hobas was selected as it met the required head requirements and as the Hobas internal diameter was slighter smaller than originally specified, the hydraulic specifications of the Hobas pipe offset the reduced volume.”

RELATED: DC Water Opens First Leg of Massive Tunnel System

Shylanski said the Hobas pipe was jacked from DC Water’s CSO-018 shaft and was designed as the CSO-018 adit, approximately 300 lf and 90 ft deep, to the Anacostia River Tunnel. “The ends of the line – both at the shaft and tunnel connection – terminate near the structures and were embedded in a reinforced concrete collar,” he added.

Hobas Pipe USA Engineering Supervisor Rene Garcia, P.E., said the Hobas flush joint system used for jacking has been successfully tested at 100 psi external pressure, well above the field conditions on this project.

Special lead and lag pipes to be utilized with the intermediate jacking station were supplied. The use of an intermediate jacking station allowed SECA Underground Corp. to isolate different parts of the pipe stream to overcome friction, said owner Steve Leius, whose company was subcontracted by main contractor Impreglio Healy Parsons JV to perform the microtunneling operation.

“The maximum tonnage applied at any time during the run was approximately 600 tons,” Leius said. “However, most of that – up to 400 tons plus – was required over time to overcome the face pressure because of the hydrostatic loads and the slurry pressure. It’s very interesting that at the end of the drive, the machine basically holed through using approximately 50 tons generated by skin friction.”

Leius described the process in greater detail: “Obviously, when you’re jacking pipe, there’s a reaction between a pipe and the earth. You try to isolate that with overcut and whatever suspension in that area to limit that reaction. We used a polymer because of the propensity for the clay to swell with water. Because of its smooth surface and the way the pipe is spun cast, basically we didn’t have any rough areas which tends to keep the friction way down. Overall cost and outside diameter control are very beneficial to jacking operations.”

The use of an intermediate jacking station allowed SECA Underground Corp. to isolate different parts of the jacking run to overcome friction.

Finishing the Job

Due to the efficient nature of the pipe installation, open trenches were not required and traffic disruption was kept to a minimum. Additionally, special storage areas were not needed for materials and equipment.

Upon completion of the jacking run, infiltration testing was performed to check for leaks. In addition to the visual leakage survey that was conducted pipe deflection was measured as well. Although one joint had minor leakage, the problem was solved by following a plan already in place to laminate that joint.

About two weeks after its opening, the tunnel passed its first real-life test with flying colors when the District of Columbia sustained a pounding rainfall of 2 in. within three hours. The tunnel stored and treated millions of gallons of combined sewage that would have previously flowed to the river.

Mining for the next portion of the Anacostia River Tunnel System, the Northeast Boundary Tunnel, will soon begin. The tunnel will add approximately 90 million gallons of storage when it opens in 2023.

Once the Anacostia River Tunnel System is completed, overflows may still happen in rare, extreme rainstorms, but the tunnels will capture 98 percent of the CSOs in an average year.

According to DC Water, the project will lower the chance of flooding in the areas it serves from approximately 50 to 7 percent, an amount equivalent to a 15-year storm in any given year. The amount of nitrogen discharged to Chesapeake Bay will also decrease by approximately 1 million pounds per year.

Bloomingdale and LeDroit Park residents, who have been served by an undersized sewer for decades, will reap the benefits as well since the finished tunnel system is expected to provide greater flood relief to their neighborhoods.

This article was written by Vicki Thompson, Freelance Writer.

RELATED: Salini Impregilo, S.A. Healy Win $580M Northeast Boundary Tunnel

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In its longest iteration at the DRTC the Robbins continuous conveyor extended to 25 km (15 miles) of belt (total span of the belt—the tunnel measures 12.5 km (7.5 miles) in length) and traveled through two unprecedented 90-degree curves.

On April 10, 2019, crews celebrated the breakthrough of a Robbins Main Beam TBM below Indianapolis, Indiana. The smooth completion was anything but run-of-the-mill: the vast network involves 45 km (28 miles) of limestone and dolomite tunnels all being excavated by one 6.2-m (20.2-ft) machine and continuous conveyor system.

The hard-working TBM and the Shea–Kiewit (S-K) JV, which owns and operates the machine, completed the 8.5-km (5.3-mile) White River Tunnel and the 2.9-km (1.8-mile) Lower Pogues Tunnel as part of the DigIndy Network. The next phase of excavation will be to bore the Fall Creek and Pleasant Run Tunnels.

“The TBM has done very well and continues to do well. There were no major machine issues on these runs; the cutterhead was new from the Deep Rock Tunnel Connector (DRTC) and we’ve had no major problems,” said Christian Heinz, Project Manager for S-K JV.

The rebuilt Robbins hard rock TBM was first used in Indianapolis on the 12.5-km (7.8-mile) long DRTC. On that tunnel, the speedy machine achieved world records in its size class of 6 to 7 m (20 to 23 ft), including “Most Feet Mined in One Day” (124.9 m/409.8 ft); “Most Feet Mined in One Week” (515.1 m/1,690 ft); and “Most Feet Mined in One Month” (1,754 m/5,755 ft).

However, the DRTC was far from the TBM’s first job. The machine, originally built in 1980, has been used on New York City’s Second Avenue Subway, as well as projects in Massachusetts and Canada. Once the machine has completed the DigIndy network of tunnels, it will have bored more than 63 km (39 miles) of tunnel — an achievement making it one of the most prolific Robbins TBMs ever used.

RELATED: Second Avenue Subway Opens in New York

S-K JV has until 2024 to complete all of the tunnels for owner Citizens Energy Group. Once complete, the EPA-mandated deep tunnel system will reduce the amount of raw sewage overflows and clean up the White River and its tributaries. The $2 billion program is projected to reduce combined sewer overflows into the area’s waterways by 97 percent.

The S-K JV is now working on the 6.2 km (3.9 mi) Fall Creek Tunnel, which will include 11 drop shafts to depths of over 60 m (200 ft).

The machine was launched most recently from the 67-m (220-ft) deep White River shaft in September 2016 following a refurbishment that included new motors, gearboxes, electronics and other elements. About 1 mile into the White River Tunnel, the drive bifurcated eastward on the Lower Pogues Run Tunnel in front of Lucas Oil Stadium in downtown Indianapolis. After excavating the offshoot, the machine then had to be backed up to the bifurcation point before continuing north for completion of the White River Tunnel, and that wasn’t the only area where the machine had to be reversed. “We backed up the machine about 6,000 m (20,000 ft) during the course of mining these two tunnels. There were two branches off the main line that were each about 3.2 km (2 miles) long,” said Max Engen, Project Engineer for S-K JV.

In areas where the machine will need to be backed up crews use swellex bolts and split sets for ground support in the limestone and dolomite rock. “These types of support fit tighter against the rock so we don’t hit the side and roof supports when we back out,” Engen said. Each time the machine is backed up the crew must also remove the side-mounted tunnel conveyor directly behind the TBM.

Despite some challenges, the Robbins TBM achieved advance rates as high as 298.2 m (978.4 ft) in one week and 84.0 m (275.6 ft) in 24 hours. “The Robbins team is always a big help. They helped design new trailing gear decks for our pre-excavation grouting setup. We conduct probe drilling and grouting when necessary,” said Engen.

Moving the Muck

As the machine bores, Robbins continuous conveyors remove muck in an extensive system that has proved highly successful. Much of the conveyor structure has remained the same throughout excavation of the DRTC, White River and Lower Pogues tunnels, with new horizontal and conveyor belting provided. The conveyors wound through curves as sharp as 300 m (1,000 ft) in radius on the two most recent tunnels, as they follow the path of the White River overhead. The curves span a distance of 3,520 m (11,540 ft) or just over 30 percent of the tunnel lengths.

The massive conveyor system in Indianapolis offers clear advantages in terms of flexibility and reduced downtime. The system includes side-mounted in-tunnel conveyor belting and structures with patented self-adjusting curve idlers, booster drives, a vertical conveyor and radial stacker.

The Robbins continuous conveyor system, like the TBM, is a proven structure that has been refurbished and previously used on three other tunnel projects before the DigIndy Tunnel.

In its longest iteration at the DRTC, the continuous conveyor extended to 25 km (15 miles) of belt (total span of the belt—the tunnel measures 12.5 km (7.5 miles) in length) and traveled through two unprecedented 90-degree curves, drawing muck up a 76-m (250-ft) deep shaft using the vertical belt.

Crews upkeep the belt with rigorous maintenance during every shift, including tracking, placing and replacing rollers, making sure boosters are running right, and looking at oil levels. A belt monitoring system that tracks belt tension and other parameters aids in maintenance. “Overall when properly maintained, the conveyor system runs really well. Dean Workman and Tommy Bess from Robbins’ Conveyor Division were an important part of it all. They came out to the site to teach proper maintenance on the belt and are available for ongoing training with the crew,” said Heinz.

RELATED: Robbins Supplies 100th Continuous Conveyor System

The continuous conveyor system, like the TBM, is a proven structure that has been refurbished and previously used on three other tunnel projects before the DigIndy Tunnel. The long-haul nature of the conveyor system is helped by its heavy structure, up to 33% heavier than other manufacturers on the market. “The system at Indianapolis was originally used on the Parramatta Rail Link, a record-setting project in Australia, then on a tunnel in Atlanta, Georgia. It says a lot for our refurbished equipment,” said Dean Workman, Robbins Vice President of Conveyor Systems. “There are other systems out there with components that are at least 25 years old. Like all equipment, proper maintenance and storage in a dry place is key.”

On the Move

With the breakthrough behind them, S-K JV is now working on the 6.2-km (3.9-mile) Fall Creek Tunnel, which will include 11 drop shafts to depths of over 60 m (200 ft). The White River Tunnel retrieval shaft is also the launch shaft for the Fall Creek Tunnel, meaning none of the equipment had to be removed to the surface. “No major rebuilds were required of the TBM after tunneling. We have already started up again and are now about 300 m (1,000 ft) into Fall Creek. We will do some maintenance for about a month and a half before we move our conveyor system,” said Engen.

The conveyor system, which is still at the White River launch shaft, will be dismantled and moved to the Fall Creek Launch shaft as the machine bores forward. This will be the second time the team has dismantled and reassembled the conveyor system, and it will happen again when the TBM completes its last tunnel at Pleasant Run, a final 11.9-km (7.4-mile) deep leg consisting of 8 drop shafts that will capture 30 combined sewer overflows.

While work is ongoing, the S-K JV team is proud of what it has been able to achieve with a single TBM. “The credit goes to all the hardworking men and women involved with this project. The machine has been underground for 32 months, and it’s been a long road to get to this point, but we believe our team will get the job done,” said Heinz.

This article was contributed by The Robbins Company.

The post DigIndy Plows Ahead: Workhorse TBM and Conveyor System Complete Leg of Vast Indianapolis Network appeared first on Tunnel Business Magazine.

Organizers have announced the 4th annual Risk Management in Underground Construction course will be held March 10-11, 2020 at the Hyatt Regency Houston Intercontinental Airport Hotel in Houston, TX USA.

The highly-rated Risk Management in Underground Construction course provides a unique and engaging forum for stakeholders involved in large-scale underground projects, including contractors, owners, consultants, insurance companies, vendors, and law firms. As tunneling projects get larger and more complicated, the issue of risk becomes more important.

International industry experts with real-world experience will cover contracting practices, geotechnical baseline reports, funding, insurance, risk registers, and best practices. CLE and CEUs will be issued for attendees who request this certification. Registration and a full agenda are coming soon.

For more information on the conference or to become a sponsor, please contact Brittany Cline at bcline@benjaminmedia.com.

Risk Management in Underground Construction is presented by Ozdemir Engineering, Microtunneling Inc. and Benjamin Media Inc., publisher of TBM: Tunnel Business Magazine.

RELATED: Risk Management Professionals Convene in LA

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Normet made history by demonstrating battery electric emulsion charging in production environment underground on June 4 in Pyhäsalmi mine, Finland, with its Charmec MC 605 VE SD, for the first time in Europe, the company reported. Battery-based charging makes the explosives charging process safer and more efficient, as there is no need to plug in to the mine’s electric grid.

Charmec MC 605 VE SD presents the new era of charging in underground mines. Normet SmartDrive (SD) battery electric vehicle technology integrated to the state-of-art emulsion charging technology offers the highest value to customer in terms of safety, health, ergonomics and productivity, with zero local emissions. Charmec MC is globally well-known charger and its charging technology is proven in the hardest conditions. Charmec MC 605 VE SD has a full range of optional accessories to fulfill variety of customer needs and to improve modern underground development and production charging operations while increasing customer value.

Battery-based charging complements Normet’s market-leading underground charging offering. Normet’s charging equipment have been designed with safety and mechanization in mind, to fulfill even the most demanding customer needs all over the world.

RELATED: Santamaria Appointed President and CEO of Normet

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The first microtunnel drive has been successfully completed for the City of New Albany, Ohio’s Blacklick Creek Trunk Sewer (BCTS), Aldea Services Inc. reported. Part 1, a 48-in. (1,200 mm) inside diameter RCP curved (vertical and horizontal) microtunnel that will be 3,154 ft (961 m) long when completed.  The purpose of this extension is to provide sanitary sewer service to the areas of Jefferson Township, Plain Township, and the City of New Albany.

The project consists of two curved microtunnel drives with lengths of 1,653 ft (504 m) and 1,501 feet (458 m) respectively, one launch shaft, and two receiving pits. The drives are located from 20 ft to 38 ft below ground surface are being excavated using a Herrenknecht (AVN 1200) slurry microtunnel boring machine (MTBM) on a grade of 0.30%. The geology of the tunnel is predominantly in rock (Cuyahoga Shale) with 5% to 10% of the drive length being in a fine-grained till and coarse-grained till material (glacial soils), below the water table.

Like any complex underground construction project, Blacklick Creek requires close coordination to minimize impact to the surrounding community. “Additional project constraints and key stakeholder concerns include protection of groundwater and private wells, a creek crossing, a county road crossing, tie-in to a downstream newly-constructed sewer tunnel, and disruption to local traffic and residents,” explained Guadalupe Monge, PE, of Aldea Services, which is serving as the Construction Management Team and trenchless design engineers.

Construction began on Feb. 4, 2019, with preparation of work areas, construction of jacking and receiving pits (reinforced concrete caisson shaft method), and installation of settlement monitoring points. Microtunneling construction of the first drive (MH-3 to MH-5) began on March 21, 2019, and was completed successfully on May 1, 2019. The total drive length from pit wall to pit wall was 1,653 ft and the average jacking force experienced was 148 tons (including the head), two inter-jacking stations (IJS) were installed but were not used.

“Our average skin friction of 0.080 psi (including the vertical curve) demonstrates that when the jacking pipe has a joint capable of withstanding 55 psi (min) external pressure, adequate lubrication can then be distributed to the annulus at an adequate pressure to control the skin friction being applied to the pipe, allowing lower tonnage and greater tunnel distances be achieved,” explained Colin Irwin of Ward & Burke, which is serving as the trenchless contractor. The average advance rate was approximately 50 ft/day (excluding Sundays and holidays), working two 12-hour shifts per day.

Construction of the final drive (1,501 ft total length) began on May 14, 2019 and will incorporate compound curves with 820 ft (250 m) and 1,640 ft (500 m) radii, and a 400-ft straight section. The contractor plans to use a relatively new Herrenknecht technology called an “Anti-roll can” which will prevent rolling of the MTBM and increase production.

In addition to Aldea Services working as the Construction Management Team and trenchless design engineers, other contractors on the Blacklick Creek Trunk Sewer project include: Trenchless Contractor: Ward & Burke Tunneling Inc.; Lead Design Engineer: EMH&T; Manufacturer/Suppliers: Herrenknecht (MTBM), VMT (guidance system); Forterra (jacking pipe).

RELATED: Aldea Services Adds Povill to Ontario Office

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The Robbins Company announced the passing of Richard James Robbins, President and CEO of the company from 1958 to 1993. Robbins passed away surrounded by family on Thursday May 30, 2019 in Seattle, Washington, USA. He is survived by his wife Bonnie, son Jim and daughter Jennifer.

Robbins was widely regarded as a titan of the tunneling industry and built The Robbins Company into an industry leader, from the first Double Shield machine to modern-day disc cutters for hard rock, to his notable TBM innovations at the Channel Tunnel connecting the U.K. and France. In total he filed 11 U.S. patents and 56 foreign patents in the field of underground mechanical excavation, and ultimately won the 2009 Benjamin Franklin Medal in Engineering for his contributions. He accomplished all of this after taking over the company at the age of 25 following the untimely passing of his father James S. Robbins in a plane crash.

“In 1968 when I first had the chance to work for what was then known as James S. Robbins Co., I did not fully appreciate that I was getting a chance to work with the greatest innovator in the tunneling industry,” said Robbins President Lok Home. “Dick was a great mentor as a boss and as a person. He was always pushing the limits of what could be done with TBMs. Dick’s integrity, energy, and passion improved the worldwide tunneling industry, and his creations set many of the industry standards.  It has been an honor to further the great name of Robbins in the industry.”

“Dick unselfishly gave back to his industry and to his community,” said consultant and former ITA President Harvey Parker, a long-time friend of the Robbins family. “He was very active in our industry’s professional associations both here in the United States and internationally.  I was honored to work closely with Dick during his significant involvement in the International Tunnelling and Underground Space Association (ITA) where he served on the Executive Council for years, was elected First Vice President, and was a leader for the ITA Working Group on Mechanized Tunnelling.”

Robbins’ many awards garnered over the years included numerous honorary degrees, memberships and directorships in a wide variety of organizations ranging from Virginia Mason Medical Center to the Board of Trustees at his alma mater Michigan Technological University.  In 1999, the Engineering News-Record selected him as one of the “125 Top People of the Past 125 Years,” an equipment innovator who “helped shape this nation and the world.”

He was well-known in Seattle for his active contributions in community organizations and sports. “Dick was a wonderful family man,” said Parker.  “He was a great personal and professional friend who was always charming and pleasant.  He designed and lived in his own innovative floating home (houseboat) on Lake Union in Seattle.  He was an avid and very competitive sailor who designed a state-of-the-art sailboat in which he raced worldwide in races such as the famous Sydney-Hobart race.  Dick was also very active and competitive in water sports, particularly in rowing crew races.  Dick will be sorely missed, not only by those of us in the tunneling industry but also by those in the many other fields of endeavor that he touched during his active life.”

RELATED: Robbins Celebrates 60 Years of World-Class Tunneling

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Sika on May 1 announced that it has officially completed the acquisition of King Packaged Materials Co., a large independent Canadian manufacturer of dry shotcrete, mortars and concrete solutions, along with its U.S. brand, Allentown, Pa.-based King Shotcrete Equipment Inc. With this acquisition, Sika will continue to expand its geographical footprint and improve its growth potential in the home improvement, construction and mining and tunneling markets. The acquired business generates annual sales of $81 million (CAD) with  a workforce of 180 employees.

King is a family owned business and a well‐established manufacturer of products for the construction and mining industry as well as for the home improvement distribution channel. The  portfolio includes shotcrete solutions, grouts, and repair and masonry mortars.

The company has an excellent reputation for its recognized brands, its high quality and reliable product solutions, and its strong technical sales expertise. King operates three large state‐of‐the‐art plants, one located in Boisbriand (QC), close to Montreal, one in Brantford (ON), near Toronto, which are the most populated regions in Canada with dynamic construction activities and the third one in the heart of Ontario’s mining country, in Sudbury.

Christoph Ganz, Regional Manager Americas: “With the acquisition of King and its broad and
highly complementary product offering we will further strengthen our presence in [North America] and  open up exciting new cross‐selling opportunities. Especially in the home improvement market  and in the growing tunneling and mining market segments, the acquisition of King Packaged Materials will make Sika Canada one of the leading suppliers of concrete solutions. We look forward to a successful joint future and would like to extend a very warm welcome to all King employees as they join the Sika team.”

Richard Aubertin, President of Sika Canada Inc.: “The acquisition of King Packaged Materials will improve our presence and penetration on several market segments thanks to an increased production capacity of cement‐based materials in Central and Eastern Canada. The complementarity of the product lines, on markets with high growth potential, such as home improvement, tunneling and mining, will make Sika Canada one of the leading suppliers of construction solutions in the country.”

The owners of King Packaged Materials Company, the Hutter and Macpherson families, strongly  believe that Sika is the ideal partner to continue the growth of King products in all of their market sectors. They look forward to the joint business and sales activities which offer great  potential to expand the product portfolio across Canada and internationally.

RELATED: 2018 Shotcrete Project Awards Bestowed

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