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In mid-2016, the Federal Electricity Commission (FEC) announced that Infraestructura Marina del Golfo (IMG) was awarded the construction and operation of the South of Texas – Tuxpan gas pipeline to meet Mexico's growing energy demand.

This pipeline has a transport capacity of 2,600 million cubic feet per day (approx. 74 million m3) and runs from the border with the United States near Brownsville, Texas to Tuxpan, in the state of Veracruz (Mexico).

The execution of the land-sea connection was carried out by pipe jacking method using reinforced concrete pipes with an internal diameter of 2,600 mm and AVN closed shield tunnel boring machine. This sea outfall would serve to house the gas pipeline (product pipe) formed by two twin 42-inch pipes, one inlet and one outlet, as it passes through the Altamira compression station.

The submarine pipeline, considered one of the longest executed by pipe jacking, has a total length of 2,246 meters.

The execution of this pipeline, carried out by Europea de Hincas Telemando S.A.U – Eurohinca, began in November 2017 completing the excavation work at the end of July 2018.


Land-sea pipeline for the installation of the South of Texas – Tuxpan gas pipeline as it passes through the Altamira compression station (Mexico).



Comisión Federal de Electricidad (CFE)

Main Contractor

Infraestructura Marina del Golfo (IMG)

IMG - Joint Venture TC Energy (previously TransCanada) - IEnova

Microtunneling Contractor

Eurohinca (Europea de hincas teledirigidas S.A.U.)


The excavation works began in mid-November 2017 and was concluded at the end of July 2018 reaching the final position of the tunnel after excavating 2,246 meters. The installation of the gas pipeline as it passes through Altamira was successfully completed at the beginning of January 2019.


Altamira, Tampico, Mexico.

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Image 1: South of Texas – Tuxpan Pipeline location


The South of Texas – Tuxpan gas pipeline was built to meet Mexico's energy demand by transporting natural gas from South Texas to generation plants in Tamaulipas and Veracruz and other vital areas of the country as established by its National Development Plan (NDP).

The land-sea submarine pipeline executed by pipe jacking was the most critical and complex crossing of the project.

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Image 2: Aerial view of work platform, salt flats and mangroves.

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Image 3: Orthophoto showing the layout of the land-sea crossing executed.


For the execution of the land-sea connection of the gas pipeline, conventional execution methods were discarded due to high environmental restrictions, mangrove protected area, several surface water bodies and the existence of a coral barrier near the coast, finally opting for pipe driving as the most appropriate method to cover the 2,246 meters of underground crossing, turning the Altamira sea outfall into the longest sea outfall with direct exit to the sea in the world executed to date.

In order to execute the land-sea connection of the gas pipeline as it passes through Altamira, a work platform of more than 500 meters long and more than 100 meters wide was built. On the platform was built the launching shaft, executed by means of a screen wall or Milan wall with metal braces and distribution beams on three levels and the launch ramp necessary for the installation of the product pipe once the excavation and recovery works of the seabed tunnel boring machine have been completed.

The launching shaft had the particularity of being a rectangular shaft of 23.5 meters long between inner faces of the screens and 12 meters wide to be able to install a double jacking system to optimize the execution of the excavation allowing the simultaneous installation of up to three reinforced concrete pipes. The height of the bottom slab was located at a depth of about 12 meters from the upper level of the work platform.

Image 4: Launching shaft with bracing arrangement and distribution beam.

For the execution of the sea outfall, a tunnel boring machine (TBM) type AVN hydroshield from Herrenknecht was used. Given the characteristics and length of the drive, an additional module, called Push-Module, was designed and manufactured, which would allow the change of the installation mode of the tunnel lining, from pipe jacking to installation of segments rings if necessary, either by exceeding the pushing capacity or by not being able to advance with the excavation by jacking pipe.

Image 5: AVN hydroshield tunnel boring machine with OD3200 and emergency push module.

The layout in section of the projected microtunnel combined straight sections with two curved alignments, a first of 40,000 meters of radius and a second of 10,000 meters of radius, with entrance and exit slopes -2% and +2% respectively, being the layout straight in plan.


It is interesting to note the importance of the synergy between the execution of the tunnel and the subsequent installation of the pipeline to define the projected route.

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Image 6: Longitudinal section of the microtunnel.

For the lining of the tunnel, reinforced concrete pipe was used with an inner and outer diameter of 2,600 mm and 3,200 mm respectively, with the length of each pipe being 2.84 meters. This pipeline would serve to house the gas pipeline (product pipe), formed by two twin lines of 42 inches (one of entry and one of exit as it passes through the Altamira compression station) and an additional lower line of 24 inches (approx. 610 mm) that would serve to perform the hydrostatic test and in case of future need, expand the capacity of the pipeline.

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Image 7: Installation assembly of the product pipe (gas pipeline) inside the microtunnel.

A total of 752 pipes and 21 intermediate stations were jacked whose length, once closed, was 4.41 meters.

The first 10 pipes had a special design that allowed the sewing between them by means of screwed connections and joints with bolts to avoid the relative rotation between them, the purpose was to ensure that the first 30 meters behaved as a single pipe minimizing a possible risk of disconnection or differential settlement during the recovery and flood phase.

One of the challenges of the project was the choice of the guidance system not only for the final length to be executed but also for the characteristics of the push module (Push Module) installed behind the TBM. The lack of space and visibility between the ELS (Electronic Laser System) card installed in the first shield of the machine and the intermediate station-prisms assembly to be installed in the tunnel caused the alternative of using the SLS-LT system to finally use the GNS-HWL system to be ruled out, combination of a gyroscope to calculate the horizontal position and a water level to calculate the vertical position of the TBM.

The selected guidance system worked correctly and did not condition the progress of the excavation despite not having previous references for lengths greater than 2,000 meters.

During the excavation phase, different challenges were faced, one of them was the progressive lifting (known in English as upheaval) of the tunnel in the first 200 m where a layer of great power of very plastic clays predominated.

The maximum elevation recorded was close to exceeding 600 mm at some points as shown below.

Image 8: Measurements of the upheaval in the first 200 meters of the tunnel.

This upheaval conditioned the progress of the tunnel and its structural safety, as well as the subsequent installation of the gas pipeline.

During the excavation phase, several actions were carried out to counteract the uplift, such as the ballasting of the affected section from inside the tunnel, the construction of a surface overload platform to increase the weight of the earth on the tunnel key in the area most affected by the lifting and the most effective, the removal of material from inside the tunnel by means of 2" valves installed at the bottom of the tunnel, the latter in combination with the previous ones helped to keep the lift within the established tolerances allowing to complete the construction of the conduction.

Image 9: Construction of the overload platform on the tunnel route.

Finally, after completing the excavation of the tunnel, material extractions were carried out to bring the pipeline within the installation tolerances of the gas pipeline in the affected section and as an additional contingency measure a treatment of the ground was carried out by injecting resins to minimize the possible seats resulting from the alteration of the ground during the extraction of material.

Another key to the execution of the land-sea connection was the role played by drilling and lubrication fluids, particularly the latter, in reaching the final position with a thrust force below the initial forecast of the project. At the end of the excavation the thrust force needed to push the entire tunnel from the launching shaft, without using any intermediate station, was only 900 tons.

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Image 10: Thrust vs. thrust forces Executed tunnel distance.

As shown in the graph above, the average thrust forces were approximately 0.65 ton/meter (red line).

The execution of the Altamira Sea Outfall was completed with the recovery of the two main modules, TBM and Push-Module, for this it was necessary to carry out two recovery operations, a first where the TBM was recovered and another to recover the Push-Module.

The recovery of the TBM was carried out after flooding the space between bodies (TBM and Push-Module) and driving the six front cylinders housed in the Push-Module, previously the TBM had been pressurized to 1.5 bar to equalize the height of the water column at the point of arrival and prevent the entry of water into the TBM. Once hoisted, the recovery vessel placed the TBM in an auxiliary boat for transfer to port.

The recovery of the Push-Module was carried out after flooding the tunnel along its entire length to the launching ramp and driving the 6 rear cylinders of the Push-Module separating it from the tunnel. As was done with the TBM, after hoisting, the Push-Module was placed on an auxiliary vessel to be transported to port, thus concluding the recovery operations.

Image 11: TBM lifting from the main vessel.

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Image 12: Location of the TBM on the deck of the auxiliary vessel.

Héctor Trigal



2.246 m

Inner diameter

2.600 mm

Outter diameter

3.200 mm


Descending 2% at the input and ascending from 2% at the exit


High plasticity clays, silts, organic material and sands

Starting Level

-8.5 m (awl)

Ending Level

-11.5 m (awl)

Working Pressures

1,7 bar


Hydroshield AVN (Herrenknecht)

Intermediate Jacking Stations



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