The track of Line C of the Rome Metro, set as the basis for the tender, was conceived to connect the eastern quadrant of Rome, starting from the Pantano terminus in the municipality of Monte Compatri, with the north-western part (Clodio-Mazzini area), passing through the historic center. The originally conceived route aimed to provide the city of Rome with a rapid transportation infrastructure that could:
- Connect the areas at the northeastern limits of the municipal territory to those in the southwest.
- Bring a significant increase in the network effect with the two existing lines.
- Reduce surface vehicular traffic.
- Allow for the expansion of pedestrian zones in the central area.
Line C in Operation
The section of Line C that is currently built and operational extends from the far eastern periphery to the San Giovanni station, the gateway to the historic center. It passes through popular neighborhoods along the Casilina Street before going underground at the Giardinetti station. From here, it serves the important neighborhoods of Alessandrino, Centocelle, and Pigneto. The center and the periphery are brought closer, reducing physical and social distances. The section currently in an advanced construction phase, known as “Tratta T3,” starts from the San Giovanni station, enters the historic center of Rome, traversing an urban fabric characterized by unique archaeological and monumental remains declared UNESCO World Heritage.
Activities began in 2006 with initial archaeological investigations and the development of the final design. Currently, 22 stations and approximately 19 kilometers of track are open to the public in the section between the Monte Compatri/Pantano station and the San Giovanni station. The latter, in passenger operation since May 12, 2018, serves as an important interchange node with the existing Line A. Line C is the first fully automated line built in Rome and one of the most technologically advanced subways in the world. In its current configuration, with the 13 trains delivered by Metro C ScpA to the operator, it can provide a train frequency of one train every 7 minutes.
The construction of the Line C stations provided an opportunity to initiate a process of revitalization of the squares where the stations are located and their surrounding areas. The new stations have spacious areas that can be used for various initiatives, transforming them from simple functional spaces into true “city landmarks.”
The first initiatives were carried out even before the start of operations, such as the two concerts by the youth choir of the Teatro dell’Opera. The first concert took place in the atrium of the Teano station, and the second was held at the San Giovanni station during its inauguration. Additional initiatives followed, such as the event titled “Mamme narranti,” which took place as part of the Letterature Off festival of literature in Rome in June 2019. At the San Giovanni, Pigneto, and Mirti stations, there were “spectacular readings” featuring mothers from different parts of the world reading tales from their own cultural traditions. Starting from the end of June 2019 until early October, a series of free concerts were held at the Pigneto, Malatesta, Teano, Mirti, and Centocelle stations.
The construction of Line C also served as an opportunity for study and research, as evidenced by the numerous discoveries made during archaeological excavations. It also provided a chance to enhance the accessibility and enjoyment of Rome’s historical archaeological heritage. A comprehensive program of investigations, carried out by Metro C ScpA in collaboration with Rome Metropolitane and the Ministry for Cultural Heritage and Activities, resulted in the identification of numerous artifacts. This program was conducted under the Scientific Operational Direction of Excavations by the Archaeological Superintendence of Rome, not only leading to the discovery of numerous artifacts but also to the update of archaeological records in previously unexplored areas.
The phases and execution methods of the works, their duration, and their temporal sequence were approved and shared within a <strong>technical committee</strong> involving the Department of Mobility and Transport of the Municipality of Rome, ATAC, USTIF, the Lazio Region, and Rome Metropolitane. The work program is organized with time windows that allow for early closure at 9 PM of the operational line and some weekends of complete closure.
In order to minimize interference with the operational line, the usable part of the existing platform of Line B, which is 150 meters long, was reduced to 110 meters. This reduction allowed for the installation of a <strong>compartmentalization structure</strong> in the intervention area. The purpose of this structure is to physically separate the work areas from those affected by the service. The structure consists of a <strong>framework of metal beams and pillars</strong>, on which a corrugated sheet parallel to the tunnel is mounted. The area of the tunnel supports has been delimited with a system of wooden panels connected to the metal structure, leaving only one gate for access by the construction workers directly from the platform. Only after the assembly of this structure was it possible to proceed with the subsequent phases, which include the <strong>cutting of the tunnel roof and supports</strong>, over a width of about 8 meters, and the construction of 4 plinths founded on micropiles, on which the final overpass structure will be launched.
Once the tunnel roof was cut, the assembly of the overpass structure began. The first step was the launching of two longitudinal beams, which represent the main framework of the structure. This launch took place <strong>on the nights between April 22 and 23</strong>. The installation of prefabricated structures (pre-slabs) is currently in progress, as well as the completion of the bottom slab. Steel bracing will be positioned, the upper pre-slabs will be launched, and the covering slab of the box will be cast. Only after these steps will the parts of the existing tunnel be demolished to create access to the platform at the Colosseo station. The crossing will then be completed with the installation of glass side walls and interior finishes.
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In the case of the Stazione San Giovanni, the numerous findings have led to the decision to create a specific museum installation inside the station, while the ongoing project for the Amba Aradam/Ipponio station involves the valorization in situ of the archaeological complex discovered during excavations. These interventions confirm how the construction of major urban infrastructures like Line C represents a tremendous opportunity for enriching historical and archaeological knowledge and for the protection and enhancement of new discoveries.
Line C under construction: San Giovanni – Fori Imperiali
The section known as T3 of Line C, currently under construction, covers a distance of approximately 2.8 km, with 2 stations (Amba Aradam/Ipponio and Fori Imperiali) and 2 ventilation shafts (via Sannio and Piazza Celimontana). Construction began on March 21, 2013. The T3 route starts from Piazzale Appio, where the line tunnels pass below San Giovanni Station on Line A, entering the historic city center to reach Fori Imperiali Station, passing through an urban fabric characterized by unique archaeological and monumental pre-existing structures in the world. From Piazzale Appio, the route continues parallel to the Aurelian Walls (in this initial section, Amba Aradam/Ipponio Station and Multifunctional Shaft 3.3 are located), then it passes under the Aurelian Walls at Porta Metronia and continues towards the Celio hill, where a large-diameter ventilation shaft has been constructed in Piazza Celimontana, inside of which a railway connection for even/odd tracks is integrated. In this section, the line tunnels reach the greatest depth ever achieved within Line C, penetrating approximately 15 meters into the pliocene clay layer, at an elevation of 55 meters above ground level with a hydraulic head, evaluated on the tunnel’s crown, exceeding 40 meters. Continuing along the route, you encounter Fori Imperiali Station, built below Via dei Fori Imperiali in the section between the Basilica of Maxentius and the Colosseum square. The line tunnels follow the axis of Via dei Fori Imperiali, passing adjacent to the Forum of Caesar, tunneling beneath the Cloaca Maxima, and skirting the Columns of the Forum of Nerva.
The tunnels with mechanized excavation TBM
The tunnels are constructed using mechanized excavation with TBM (Tunnel Boring Machine) of the EPB type (Earth Pressure Balance). The machines are equipped with a cutterhead with a diameter of 6.70 meters, while the final tunnel lining consists of precast segments with a thickness of 30 cm.
In the exterior area of the construction site, the final cladding of the Muñoz Wall is underway. These works are being carried out by a specialized restoration company, following a study and sampling of the most suitable cladding types in collaboration with the Superintendency. In the Clivo di Venere area, where the construction site is more extensive, the assembly of the injection system has been completed, and consolidation work has begun from the TBM tunnel, preparatory to the excavation to widen the platform of the odd-track platform. As for the structure of Line C station (Clivo di Venere side), the roof slabs, atrium, and first technical floor have currently been completed, and excavation work is in progress between the latter and the mezzanine floor. Activities related to station linings between the atrium level and the first technical floor are also in progress.
Particular attention is given to the third construction macro-area (Colosseo Shaft), which concerns the connection between Fori Imperiali station and the existing Line B Colosseo station. The overpass structure described earlier terminates in a shaft, constructed at the base of the Colosseum, allowing access to the platform towards Termini. The shaft was excavated using a double micropile shoring system and a system of metal struts that facilitated the emptying of the structure in an archaeological manner. Currently, excavation activities are complete, and the bottom slab of the structure is being constructed, followed by the linings and the top slab. The section of the structure between Fori Imperiali station and the existing Line B tunnel is under construction. Among the completed parts of the work are the top slab and bottom slab, except for the portion closest to Line B, and part of the perimeter linings have been finished.
Tunnels: Traditional Excavation from Stazione San Giovanni to Pozzo 3.3 Sannio
The tunnels in this approximately 150-meter section, due to constraints arising from the topographical layout of the route, have been constructed using blind hole excavation for both tracks, carried out using a shielded cutterhead with a diameter of 3000 mm (micro-TBM). The use of this excavation method became necessary for several reasons:
- The impossibility of the TBM machines that excavated all the Line C tunnels to pass under the existing Stazione San Giovanni of Metro A;
- The impossibility of conducting consolidations from above due to the presence of archaeological layers.
Currently, the following activities are in progress:
- Excavation of the natural tunnel for the odd-track side of San Giovanni;
- Preliminary work for the construction of the final lining of the even-track tunnel.
Soon, activities will commence for opening the connection gap of the odd-track line tunnel between the operational section and the one under construction, as well as the construction of the slab for laying the railway track.
Pozzo 3.3. Sannio
The multifunctional shaft 3.3 is located between Amba Aradam/Ipponio and San Giovanni stations, adjacent to a garden near the Via Sannio market on the Piazzale Appio side. This is the shaft from which the TBMs began tunneling in the direction of Fori Imperiali.
Currently, activities are underway to complete the bottom slab and construct the perimeter linings and slabs for the 3 levels below the cover. Soon, work will progress to finish the technical levels designated for equipment and technology rooms, the construction of the slab for laying the tracks, and the construction of the metal platform.
Amba Aradam/Ipponio Station
It extends for approximately 120 meters in length and over 30 meters in depth, composed of 5 levels including the roof and foundation. The urban context in which it is situated, combined with the limited size of the construction site, necessitated the choice of the Top-Down method as the excavation methodology for the station. This method involves excavation under the roof, creating intermediate floors as excavation progresses and using these structural elements as intermediate braces for the perimeter diaphragms, even during the excavation phase. The station functionally follows the typological pattern of Line C stations, with a central platform that extends for 110 meters in length and approximately 4 meters in width.
Significant ancient structures were discovered at this site during the second phase of archaeological excavations, which began once the perimeter shoring was completed. The archaeological investigations at Amba Aradam/Ipponio station of Line C covered an area of approximately 1753 square meters and led to discoveries of exceptional interest. As a result of these findings, the Archaeological Superintendence, in order to preserve and enhance the discoveries, required the redefinition of the architectural-functional project to relocate the ancient structures within the station in the same position and layout and to contextualize the artifacts found by restoring the visual relationship with the Aurelian Walls.
Following this requirement, Metro C ScpA requested three well-known architecture firms to develop concepts for the redefinition of the architectural-functional project. Based on the concept selected by the Archaeological Superintendence, the final project was developed and delivered to the client, Roma Metropolitane, in August 2018 and is currently in the approval phase.
Following the approval of the aforementioned final project, it will be necessary to develop the detailed and construction design, which will need to be submitted for approval by the client. Subsequently, construction work can resume. Currently, the station construction site is being used for logistical support for all TBM excavation activities, including the introduction of segments and the removal of excavated earth, among other tasks.
Pozzo 3.2. Celimontana
The shaft is located in a garden adjacent to Piazza Celimontana and has a circular plan with a diameter of 34.80 meters. The iron level is at an elevation of -15.50 meters above sea level, resulting in a significant excavation depth of about 59 meters from ground level.
The construction of the shaft, up to the levels subject to archaeological investigations (+19.00 meters above sea level), was carried out using archaeological excavation methods. During the archaeological excavation phases, the presence of reinforced concrete shoring allowed for safe descent to otherwise unreachable depths. At a depth of approximately 17 meters from the current level, a Republican-era aqueduct made of squared tuff blocks was uncovered, connected to a large tank dating back to the third century BC. Additionally, a burial site with accompanying items dating between the late 10th century and the early 9th century BC was discovered. Currently, the internal structures from level 5 (-45 meters from ground level) to level 1 (-8 meters from ground level) have been completed, as well as the lift structures and linings for the level 1 ceiling. The construction of the level 1 technical floor is in progress, using prefabricated elements. Excavation work will resume shortly, starting from an elevation of -45 meters from ground level.
Fori Imperiali Station and the Connection with Line B
The station is located beneath the street of the same name, between the Colosseum and the area in front of the Basilica of Maxentius, and plays a strategic role as it is situated in one of the most visited monumental areas in the world. It will become a fundamental interchange point with Line B.
The connection with Line B Colosseo is achieved through a tunnel consisting of two levels that will lead users to both platforms of the existing station, starting from the atrium level. The platform for the even-track is directly connected, while to reach the platform in the direction of Laurentina, passengers will need to cross the railway line by passing through a steel and glass tunnel partially incorporated into the vault of the existing station, which will have to be partially cut to accommodate the tunnel itself.
The station structure is a rectangular box excavated between diaphragm walls with a thickness of 1.20 meters, which extend up to 48 meters from ground level and are anchored in the impermeable layer of pliocene clays that serves as a natural bottom buffer. This is essential given the nature of the soil and the hydraulic head that exceeds 20 meters once excavation reaches the bottom. In this case as well, the adoption of the Top-Down excavation method was a mandatory choice, considering the impossibility of eliminating vehicular traffic along Via dei Fori Imperiali.
The reinforced concrete structure that will house the station is complete, including the roof slab and the atrium level slab. During the excavation beneath the roof between the roof slab and the atrium level slab, the dismantling of 28 ancient wells was carried out using archaeological methods.
Currently, the following activities related to the construction of the station body are in progress:
– Relocation of archaeological artifacts, as prescribed by the Parco Archeologico Colosseo (Archaeological Park of the Colosseum), aimed at preserving the structures.
– Excavation beneath the roof between the atrium level and the first technical level.
– Construction of the first technical level slab.
For the construction of the pedestrian connection between Fori Imperiali Station and Line B Colosseo Station, the relocation of systems and equipment has been carried out, which is a prerequisite for the assembly of a steel structure designed to contain the vault in the section where the future pedestrian underpass will be built. Currently, the following activities are underway:
– Archaeological excavation of the Colosseo Shaft, which contains the connection to Line B.
– Construction of the pedestrian connection tunnel.
Monitoring of Monuments and Historic Buildings and Protective Measures
Along its route, Line C interacts with historic buildings and monuments of great value, from the Colosseum to the Palazzo della Cancelleria and Palazzo Venezia. To ensure the preservation of this world-heritage protected by UNESCO, Metro C ScpA has undertaken a series of preventive activities to accurately and reliably assess the condition of historic buildings and monuments. The analyses of the interaction between the subway line and monuments have involved 13 monuments and 40 historic buildings, including those located in the Baroque bend of the Tiber River along Corso Vittorio Emanuele. These studies have been developed starting from survey and investigation phases, leading to the definition of specific monitoring plans and preservation interventions for each monument, developed in collaboration with the Ministry for Cultural Heritage and Activities.
The Amba Aradam/Ipponio Station
It extends for approximately 120 meters in length and over 30 meters in depth, comprising 5 levels, including the roof and foundation. The urban context in which it is situated, along with the limited size of the construction site, necessitated the choice of the Top-Down method as the excavation methodology for the station. This method involves excavation under the roof, creating intermediate floors as excavation progresses and using these structural elements as intermediate braces for the perimeter diaphragms, even during the excavation phase. Functionally, the station follows the typological pattern of Line C stations, with a central platform that extends for 110 meters in length and approximately 4 meters in width.
Significant ancient structures were discovered at this site during the second phase of archaeological excavations, which began once the perimeter shoring was completed. The archaeological investigations at Amba Aradam/Ipponio station of Line C covered an area of approximately 1753 square meters and led to discoveries of exceptional interest. As a result of these findings, the Archaeological Superintendence, in order to preserve and enhance the discoveries, required the redefinition of the architectural-functional project to relocate the ancient structures within the station in the same position and layout and to contextualize the artifacts found by restoring the visual relationship with the Aurelian Walls.
Following this requirement, Metro C ScpA requested three well-known architecture firms to develop concepts for the redefinition of the architectural-functional project. Based on the concept selected by the Archaeological Superintendence, the final project was developed and delivered to the client, Roma Metropolitane, in August 2018, and is currently in the approval phase.
Based on the results of the analyses conducted within the scope of the T3 section, a series of structural and/or geotechnical measures, both temporary and permanent, have been implemented for the following monuments:
- Aurelian Walls at Porta Asinaria: Temporary shoring of the walls and the construction of a pile wall to support Porta Asinaria, as well as geotechnical compensation grouting during the passage of the TBM;
- Aurelian Walls at Porta Metronia: Temporary shoring of the walls and geotechnical compensation grouting during the TBM passage;
- Santa Maria in Domnica Church: Temporary internal and external shoring and preservation interventions for the artistic heritage within the church;
- Santo Stefano Rotondo Church: Drum encircling and preservation interventions for the artistic heritage within the church;
- Celimontano Aqueduct Pillar: Temporary shoring;
- Basilica of Maxentius: Temporary shoring of the external walls and permanent interventions with ropes and bars;
- Columns of the Forum of Nerva: Temporary shoring.
All interventions, whether temporary or permanent, have been completed. Furthermore, all monuments within the subsidence area of the Line C works are continuously monitored through extensive vibrational, structural, geomatic, and geotechnical monitoring instrumentation.
