This achievement marks a significant milestone for the civic body, as it strives to open the coastal road by the year's end. The twin tunnels, spanning 2.07 kilometres, were excavated using a Chinese Tunnel Boring Machine (TBM) named Mavala, after Shivaji's mountain warfare experts. The digging process commenced in January 2021, and the breakthrough for the first tunnel occurred in January 2022. Subsequently, the TBM was maneuvered leftwards, towards the northbound tunnel, utilising a hydraulic-jack powered turn-table, facilitating a 180-degree rotation.

The final breakthrough took place in the presence of Chief Minister Eknath Shinde and Deputy Chief Minister Devendra Fadnavis on Tuesday. The portal surrounding the breakthrough point was adorned in the colours of the national flag. Mantayya Swami, the chief engineer of MCRP, explained that the TBM was positioned 30 centimetres behind the breakthrough point. Upon CM Shinde pressing the buzzer, the TBM's spokes moved forward, cutting through the remaining surface. It took approximately eight minutes on Tuesday to carve out the final 30 centimetres of the tunnel.

Following the breakthrough, CM Shinde hailed the project as an engineering marvel. He stated, "The MCRP will be the first step towards resolving the city's traffic congestion issues... This is just the initial phase of the project, and in the future, we will extend the coastal road to the suburbs, including Dahisar, Mira Road, and Bhayander."

Meanwhile, Dy CM Fadnavis attributed the rapid progress of the project to the Central government. He said, "The TBM Mavala lived up to its name. The MCRP was conceptualised years ago but remained on paper until the Modi government took charge and provided the much-needed impetus."

The MCRP, spanning 10.58 kilometres, aims to alleviate vehicular congestion in Mumbai. This high-speed corridor will link Marine Drive to the Bandra Worli Sea Link (BWSL) through a network of arterial roads, tunnels, and vehicular interchanges. The highlight of this project is the pair of tunnels that traverse beneath the Arabian Sea, making them India's first undersea tunnels.

Ashwini Bhide, the additional municipal commissioner, revealed that the road will be opened to traffic by November 2023. "Initially, the project was slated for completion by November 2023, and during this period, we aim to open the tunnel partially. By May 2024, the entire corridor will be accessible to the public. We are currently working out the specifics of the stretch we plan to open in the first phase, and more details will be available soon," Bhide informed the news publication.

Each of the two tunnels, measuring 2.07 kilometres in length, will feature three separate lanes, each 3.2 meters wide. Resembling the shape of the Queen's Necklace, the tunnels' entry and exit points will be adorned with a fibreglass facade, and the BMC intends to illuminate them.