The route of Line C of the Rome Metro, as originally planned, aimed to connect the eastern quadrant of Rome, starting from the Pantano terminus in the municipality of Monte Compatri, with the northwest quadrant (Clodio-Mazzini area), passing through the historic center. The initially conceived route had the following objectives:
- Connecting areas at the northeastern limits of the municipal territory to those in the southwest.
- Significantly increasing the network effect with the existing two lines.
- Reducing surface vehicular traffic.
- Allowing the extension of pedestrian zones in the central area.
Line C in Operation:
The section of Line C that has been completed and is currently in operation runs from the far eastern periphery to the San Giovanni station, which serves as the gateway to the historic center. It passes through the populous neighborhoods along Via Casilina, entering the underground at the Giardinetti station. From there, it reaches the significant districts of Alessandrino, Centocelle, and Pigneto. The center and the outskirts become closer, bridging physical and social distances. The section currently under advanced construction, known as “Section T3,” starts from the San Giovanni station and enters the historic center of Rome, crossing an urban fabric characterized by unique archaeological and monumental preexisting structures in the world, declared UNESCO World Heritage Sites.
The 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 service since May 12, 2018, serves as a vital interchange point with the existing Line A. Line C is the first fully automated line built in Rome and one of the most technologically advanced metro systems 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 every 7 minutes.
The construction of the Line C stations has provided an opportunity to initiate a process of revitalization for the squares where the stations are located and their surrounding areas. The new stations feature spacious areas that can also be used for various initiatives, turning them from simple functional spaces into true “city places”.
The first initiatives were implemented even before the start of operations, such as the two concerts by the children’s choir of the Opera Theater, the first of which was held in the atrium of the Teano station, and the second at the San Giovanni station during its inauguration. Additional initiatives have taken place, like the one titled “Narrating Mothers,” which was held as part of the Literature Off program of the Rome Literature Festival in June 2019. In the San Giovanni, Pigneto, and Mirti stations, “spectacularized readings” were held, featuring mothers from various parts of the world reading stories from their native traditions. Starting from the end of June 2019 until early October, a series of free concerts were also held at the Pigneto, Malatesta, Teano, Mirti, and Centocelle stations.
The construction of Line C has also been an opportunity for study and research, as evidenced by the numerous discoveries made during archaeological excavations. It has also been an opportunity to improve accessibility and the enjoyment of Rome’s historical archaeological heritage. A comprehensive program of investigations has been carried out through collaboration between Metro C ScpA, the Client Roma Metropolitane, and the Ministry for Cultural Heritage and Activities, under the Operational Scientific Direction of Archaeological Excavations of the Archaeological Superintendence of Rome. This program has not only led to the identification of numerous artifacts but has also updated archaeological maps in areas that had never been investigated before.
The phases and execution methods of the work, their duration, and their temporal sequence have been approved and shared within a technical committee involving the Department of Mobility and Transport of the Municipality of Rome, ATAC, USTIF, the Lazio Region, and Roma Metropolitane. The work program is organized with time windows for early closures at 9:00 PM of the operating line and some weekends with complete closures.
In order to minimize interference with the operating line, the usable part of the existing platform of Line B, which is 150 meters long, has been reduced to 110 meters in the area where the intervention is taking place. This reduction was made to install a compartmentalization structure designed to physically separate the work areas from those affected by the service. The structure consists of a network system of metal beams and pillars on which a corrugated sheet is mounted parallel to the vault. The area of the gallery supports has been delimited with a system of wooden panels connected to the metal structure, leaving only a gate for access by construction workers directly from the platform. Only after the assembly of this structure was it possible to proceed with the subsequent phases, which involve the cutting of the vault and supports, 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.
After the cutting of the existing gallery vault was completed, the assembly of the overpass structure began. The first step was the launching of two longitudinal beams, which represent the load-bearing framework of the structure. This launching took place on the nights between April 22 and 23. The launching of the prefabricated structures (precast elements) is currently in progress, as well as the completion of the bottom slab. Steel bracing elements will then be positioned, the upper precast elements will be launched, and the roof slab of the box section will be cast. Only after this will the parts of the existing gallery be demolished to create access to the platform of the Colosseo station. The passage will then be completed with the installation of lateral glass walls and interior finishes.
In the case of San Giovanni Station, the numerous findings have led to the decision to create a specific museum exhibition inside the station, while the ongoing project for Amba Aradam/Ipponio station’s approval involves the valorization in situ of the archaeological complex discovered during the excavations. These interventions confirm how the construction of large urban infrastructures like Line C represents a formidable 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, spans approximately 2.8 km with 2 stations (Amba Aradam/Ipponio and Fori Imperiali) and 2 ventilation shafts (via Sannio and Piazza Celimontana). The construction work commenced on March 21, 2013. The T3 route starts from Piazzale Appio, where the subway tunnels pass underneath the San Giovanni station of Line A, entering the historic city center to reach the Fori Imperiali station, crossing an urban area characterized by unique archaeological and monumental remains. From Piazzale Appio, the route continues parallel to the Aurelian Walls (in this initial section, the Amba Aradam/Ipponio station and the Multifunctional Shaft 3.3 are located). It then passes under the Aurelian Walls at Porta Metronia and continues towards the Celio, where a large-diameter ventilation shaft has been constructed in Piazza Celimontana, including a railway communication for even and odd tracks. In this section, the subway tunnels reach the greatest depth ever achieved within Line C, going down approximately 15 meters into the Pliocene clay layer at an elevation of 55 meters above sea level with a hydraulic head evaluated on the tunnel’s vault exceeding 40 meters. Continuing along the route, you encounter the Fori Imperiali station, built beneath Via dei Fori Imperiali, in the stretch between the Basilica of Maxentius and the Colosseum Square. The subway tunnels follow the axis of Via dei Fori Imperiali, passing adjacent to Caesar’s Forum, passing beneath the Cloaca Maxima, and skirting the Colonnades of the Forum of Nerva.
TBM-Machine Excavated Tunnels
The tunnels are constructed using mechanical excavation with TBM (Tunnel Boring Machine) of the EPB type (Earth Pressure Balance). These machines are equipped with a cutterhead with a diameter of 6.70 meters, and the final lining of the tunnel consists of precast segments with a thickness of 30 cm.
In the external area of the construction site, work is in progress on the final cladding of the Muñoz Wall, carried out by a specialized restoration company. The choice of cladding materials has been made after studying and sampling with the Superintendence to determine the most suitable types of cladding. 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 on the TBM tunnel in preparation for the widening of the odd-track platform tunnel. As for the Line C station structure (Clivo di Venere construction site), the roof slabs for the atrium and the first technical level have been completed. Excavation work is currently underway between the first technical level and the mezzanine slab. Activities related to the station linings between the atrium and the first technical level are also in progress.
Special attention is given to the third construction macro-area (Pozzo Colosseo), which concerns the connection between the Fori Imperiali station and the existing Line B Colosseo station. The previously described overpass structure terminates in a shaft, constructed at the foot 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 allowed for the emptying of the structure in an archaeological manner. Currently, excavation activities have been completed, and the construction of the base slab of the structure is in progress, followed by the installation of linings and the roof slab. The section of the structure between the Fori Imperiali station and the existing Line B tunnel is under construction. Among the completed parts of the work are the roof slab and the base slab, except for the section closest to Line B, and part of the perimeter linings have been completed.
Galleries: Traditional Excavation from San Giovanni Station to Pozzo 3.3 Sannio
The galleries in this approximately 150-meter section, due to constraints related to the topographic and altimetric profile of the route, have been constructed using blind hole excavation for both tracks, using a shielded cutter with a diameter of 3000 mm (micro-TBM). The use of this excavation method became necessary for several reasons:
- The impossibility of using the TBM machines that excavated all the Line C tunnels to pass beneath the existing San Giovanni Station of Metro Line A.
- The inability to perform top-down consolidations due to the presence of archaeological layers.
Currently, the following activities are in progress:
- Excavation of the natural tunnel for the odd-track side at San Giovanni.
- Preparatory work for the construction of the final lining for the even-track tunnel.
Activities for opening the connection gap of the odd-track line tunnel between the operational section and the construction section, as well as the construction of the concrete slab for the installation of railway tracks, will begin shortly.
Pozzo 3.3. Sannio
The multifunctional well 3.3 is located between the Amba Aradam/Ipponio and San Giovanni stations, adjacent to a garden near the Via Sannio market on the Piazzale Appio side. This is the well from which the TBMs started excavating the tunnels in the direction of the Fori Imperiali.
Currently, activities are underway to complete the bottom slab and the construction of the perimeter linings and slabs for the 3 levels below the cover. Soon, finishing works will commence on the technical floors intended for equipment and technology rooms, followed by the construction of the concrete slab for laying the railway tracks and the installation of the metal platform.
Amba Aradam/Ipponio Station
It extends for approximately 120 meters in length and over 30 meters in depth and consists of 5 levels, including the roof and foundation. The urban context in which it is located, along with the limited size of the construction site, dictated the choice of the Top-Down method as the excavation methodology for the station. This method involves excavating underground, constructing intermediate slabs as excavation progresses, and using these structural elements as intermediate supports for the perimeter diaphragm walls during the excavation phase. The station functionally follows the typical typology of Line C stations, with a central platform that extends for 110 meters in length and approximately 4 meters in width.
Important ancient structures were discovered at this site during the second phase of archaeological excavations, which began once the perimeter walls were constructed. Archaeological investigations at Amba Aradam/Ipponio Station of Line C covered an area of approximately 1,753 square meters and led to discoveries of exceptional interest. As a result, the Archaeological Superintendent, in order to safeguard and enhance the findings, required the redefinition of the architectural-functional project. This redefinition was necessary to reposition the ancient structures within the station in the same location and orientation and to contextualize the discovered artifacts by restoring the visual relationship with the Aurelian Walls.
Following this requirement, Metro C ScpA requested three well-known architectural firms to develop concepts for the redefinition of the architectural-functional project. Based on the concept selected by the Archaeological Superintendent, the final project was developed and delivered to the client, Roma Metropolitane, in August 2018. It is currently in the approval phase.
Following the approval of the aforementioned final project, it will be necessary to develop the executive and construction design, which will need to be submitted for approval to the client. Afterward, 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 excavation material extraction, etc.
Celimontana Shaft 3.2
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 floor level is at an elevation of -15.50 meters above sea level, resulting in a significant depth of the structure’s excavation of approximately 59 meters from ground level.
The construction of the shaft, up to the elevations involved in 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 diaphragm walls allowed for safe excavation to depths that would otherwise be unreachable. At a depth of approximately 17 meters from the current floor level, a Republic-era aqueduct constructed from squared tuff blocks was uncovered, connected to a large basin dating back to the third century BC. Additionally, a burial site with accompanying artifacts dating from the late 10th century to 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, including the lifting structures and formwork for the level 1 floor. The construction of the technical level 1 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 Interconnection with Line B
This station is located beneath the street of the same name, between the Colosseum and the area in front of the Basilica of Maxentius. It plays a strategic role as it is situated in one of the most visited monumental areas in the world and will become a crucial interchange hub with Line B.
The connection with Line B at Colosseo is established through a tunnel consisting of two levels. Starting from the atrium level, this tunnel will lead passengers to both platforms of the existing station. The platform for the even-numbered track is directly connected, while to reach the platform in the direction of Laurentina, passengers will need to cross the railway track through a steel and glass tunnel partially incorporated into the roof of the existing station. The existing station roof will need to be partially cut to accommodate this tunnel. The station structure is a rectangular box excavated between diaphragm walls that are 1.20 meters thick and extend 48 meters from ground level. They anchor into the impermeable layer of Pliocene clays, which acts as a natural bottom buffer, essential due to the nature of the terrain and a hydraulic head exceeding 20 meters once excavation reaches the bottom. In this case as well, the adoption of the Top-Down excavation method was a mandatory choice, given the impossibility of eliminating vehicular traffic along Via dei Fori Imperiali.
The reinforced concrete structure housing the station is completed, including the roof and the atrium floor. During the excavation beneath the roof, the archaeological dismantling of 28 ancient wells was carried out.
Currently, the following activities are underway for the construction of the station structure:
- Relocation of archaeological artifacts, as prescribed by the Parco Archeologico Colosseo (Colosseum Archaeological Park), aimed at the safeguarding of these structures.
- Excavation beneath the roof between the atrium level and the first technical level.
- Construction of the first technical level floor.
For the construction of the pedestrian connection between Fori Imperiali Station and Line B Colosseo Station, the relocation of equipment and apparatus has been carried out, preparatory to the installation of a metal framework structure to contain the roof in the section where the future pedestrian underpass will be constructed. Currently, the following activities are in progress:
- Archaeological excavation of Pozzo Colosseo, which contains the connection to Line B.
- Construction of the pedestrian connection tunnel.
Monitoring of Monuments and Historic Buildings and Safeguarding Interventions
Line C interacts with historic buildings and monuments of great value along its route, from the Colosseum to the Palazzo della Cancelleria and Palazzo Venezia. To ensure the preservation of this unique UNESCO-protected heritage, Metro C ScpA has carried out a series of preventive activities to accurately and reliably assess the condition of historic buildings and monuments. Interaction analyses between the subway line and monuments have involved 13 monuments and 40 historic buildings, including those within the Baroque bend of the Tiber River along Corso Vittorio Emanuele. These studies have been developed starting from survey and investigation phases, resulting in the definition of specific monitoring plans and safeguarding interventions for each monument, developed in collaboration with the Ministry for Cultural Heritage and Activities.
The safeguarding interventions can be essentially categorized into two groups:
- Provisional or definitive interventions to be implemented before the start of excavation activities: These are structural consolidation interventions aimed at addressing pre-existing issues or a pronounced state of degradation that is not directly related to the effects induced by the construction of Line C. Examples include the definitive structural consolidation interventions for the Basilica of Maxentius or the Church of Santo Stefano Rotondo, as well as provisional interventions for the Columns of the Forum of Nerva.
- Interventions to be carried out during the excavation phase to counteract induced settlements in real-time and contain them below predetermined thresholds: These are geotechnical interventions such as Compensation Grouting, which is planned during the passage of the subway tunnels beneath the Aurelian Walls at Porta Metronia and the existing Colosseo Station on Line B.
Based on the results of the analyses conducted within the T3 section, a series of structural and/or geotechnical monitoring and intervention measures, both provisional and definitive, have been implemented for the following monuments:
- Aurelian Walls at Porta Asinaria: Temporary shoring of the walls, construction of a pile wall for the protection of Porta Asinaria, and 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 passage of the TBM.
- Church of Santa Maria in Domnica: Temporary internal and external shoring and safeguarding of the artistic heritage inside the church.
- Church of Santo Stefano Rotondo: Ringing of the drum and safeguarding of the artistic heritage inside the church.
- Pylon of the Caelian Aqueduct: Temporary shoring.
- Basilica of Maxentius: Temporary shoring of the external walls and definitive anchoring with cables and bars.
- Columns of the Forum of Nerva: Temporary shoring.
All intervention measures, whether definitive or provisional, have been completed. Furthermore, continuous monitoring of all monuments located within the subsidence basin of Line C works is carried out using a comprehensive instrumentation system for vibration, structural, geomatic, and geotechnical monitoring.
