Line 4 (Mumbai Metro)

Line 4 (Green Line) of the Mumbai Metro is an under-construction rapid transit line in Mumbai, Maharashtra, India.

The Mumbai Metropolitan Region Development Authority (MMRDA) and a consortium of international companies are developing the line.

The 32.32 km line is planned to be fully elevated, and is expected to consist of 32 stations from Wadala (Mumbai) to Kasarvadavali (Ghodbunder road, Thane) via Chembur, Bhandup Mulund and Teen Hath Naka, a popular traffic crossing in Thane. It is estimated to cost ₹14,549 crore. Its construction was expected to begin by June 2018.

Alstom was initially chosen to provide rolling stock for the line, but the contract was cancelled in 2022.

Planning
In June 2015, the Mumbai Metropolitan Region Development Authority (MMRDA) proposed building a 32 km Wadala-Thane-Kasarvadavali metro line as part of a plan to build six new metro lines at a total estimated cost of inr 640000000000. Line 4 was approved in June 2016, and was estimated to cost inr 145490000000.

The foundation stone for Metro 4 was laid by Prime Minister Narendra Modi on 24 December 2016. The Maharashtra Coastal Zone Management Authority granted Coastal Regulation Zone (CRZ) clearance to the project in February 2017. Over 1 km of the line passes over water bodies in Bhakti Park and Wadala, both areas classified as CRZ II, where regulations limit construction activities. A total of 48 piers are proposed to be built in the CRZ II zone. The MMRDA proposed building metro car depots for the line on a 30 hectare plot at Owala village in Thane district and another in Vikhroli. The agency stated that the line would require two depots due to its length.

The MMRDA used a drone to carry out survey work for Metro 4. The drones were fitted with 360 degrees camera that provide up to 3 mm accuracy. The aerial survey takes less time than a regular survey, achieves greater accuracy and helps protect against false claims for compensation. In February 2017, the MMRDA said it was studying the feasibility of extending the corridor from Kasarvadavali to Gaimukh. In March 2017, the agency said that it was conducting a pre-feasbility study on extending the line from Wadala to Mumbai General Post Office in South Mumbai, via the Mumbai Port Trust. The proposed 8 km extension is estimated to cost ₹300 crore per kilometer. The extension from Kasarvadavli to Gaimukh was approved by Fadnavis at the 144th meeting of the MMRDA on 12 January 2018. The 2.7 km extension is estimated to cost inr 9490000000.

The MMRDA appointed Systra MVA Consulting India Pvt. Ltd. as the detail design consultants for Line 4 on 9 November 2017. A consortium of DB Engineering, Louis Berger and Hill International was awarded a project management and construction management services contract for the Metro 4 project in April 2018. In October 2018, the MMRDA announced that it would construct Metro 4 along with three flyovers to minimize traffic disruption, with the metro running on the upper deck of the flyover. The three flyovers will be built at Bhayander Pada, Kasarvadavli and Anandnagar near Ghodbunder.

In May 2019, MMRDA Metropolitan Commissioner R.A. Rajeev announced a modified plan to use Siddharth Colony as the interchange station with Line 2. The original plan had proposed to use the Eastern Express Highway station on Line 2B and Siddharth Colony on Line 4 as the interchange stations. However, the two stations are approximately 480 metres away from Siddharth Colony and the change was made to simplify passenger transfers.

Depot
The MMRDA considered plots in Wadala, Aarey Colony and Gaimukh Nagar in Thane to build a depot for the line. On 16 October 2023, the state urban development allotted a 174 hectare (435 acre) plot of land at Mogharpada in Thane to the MMRDA at no cost. Nine hectares of the plot is reserved for use by the BMC for the Coastal Road and a further 29 hectares is protected mangrove land. The MMRDA will utilize a portion of the remaining plot to build a depot that serves Lines 4, 10 and 11. The land left over after building the depot is zoned for residential and commercial use.

Construction
The MMRDA invited bids for civil work on the corridor on 4 January 2017. The tenders for construction of viaducts and stations were divided into five packages - Wadala to Amar Mahal Junction, Garodia Nagar to Surya Nagar, Gandhi Nagar to Sonapur, Mulund Fire Station to Majiwada and Kapurbawdi to Kasarvadavali. Metro 4 was tendered alongside Metro 2B. L&T, Afcons Infrastructure, Tata, NCC and JMC, Reliance Infrastructure-RdE, JKumar Group, ITD Cementation, CHEC-TPL bid for packages on both Metro 2B and Metro 4. A total of 10 firms and/or consortia submitted bids for the two lines, two of whom (Simplex Infrastructure and a consortium of GHEC-RCC-JV-China) bid exclusively for Metro 2B packages.

The construction work was awarded through the engineering, procurement and construction (EPC) model in April 2018. A joint venture between Reliance Infrastructure and Italian firm Astaldi S.p.A. was awarded three packages between Kasarwadavali and Wadala worth inr 15840000000. The contract for the remaining two packages, worth a combined inr 10480000000, was awarded to a joint venture between Tata Projects Limited and China Harbour Engineering Company. The civil work was expected to be completed in 30 months. Construction began in October 2018. About 80% of soil-investigation works and 66% of utility works had been completed by 3 June 2019.

In September 2019, the MMRDA awarded a inr 3420000000 contract to J Kumar Infraprojects to build the viaduct and two stations for the Metro 4A extension from Kasarvadavli to Gaimukh. In August 2020, the Bombay High Court granted the MMRDA permission to carry out construction in a mangrove buffer zone. Survey work on the land for a depot at Mogharpada began in January 2022.

The MMRDA stated that 37% of total work on Lines 4 and 4A had been completed by June 2022. The agency stated that 43.44% of viaducts and 25.20% of work on stations on Line 4 had been completed. On Line 4A, 39.03% of viaducts and 19.82% of work on stations was completed. By November 2022, 41% of civil works on Line 4 and 45% of work on Line 4A had been completed.

The Bombay High Court dismissed two petitions filed by Indo Nippon Chemical Co. Ltd. and Shree Yashwant Co-operative Housing Society Ltd. challenging the alignment for Line 4 in March 2023. In September 2023, the MMRDA awarded a inr 9050000000 contract to a joint venture between SEW Infrastructure and Vishwa Samudra Engineering to build the depot at Mogharpada. It also awarded a inr 1210000000 to Apurvakriti Infrastructure Pvt Ltd. lay ballastless railway tracks connecting Mulund Fire Station with Gaimukh and the depot.

Green Line 4
On 12 April 2023, MMRDA in press release stated that Green Line 4 project status is 49%.

Green Line 4A
On 30 December 2022, MMRDA in press release stated that Green Line 4A project status is 45%.

Stations
32 stations are being planned on Line 4. Most of them were either in the stage of planning or under early stages of construction (as of November 2018)

2 stations are being planned on Line 4A. Connected to word Gaimukh to Kasarvadavali also connect Metro 10.

Cost
Line 4 is estimated to cost inr 145490000000, and Line 4A is estimated to cost inr 9490000000. The Maharashtra Government signed an EUR545 million (₹4,000 crore) loan agreement with German development bank KfW to fund construction of Metro 4 and 4A in November 2020.

Rolling stock
The MMRDA awarded a inr 18540000000 contract to Alstom to supply 234 metro coaches for Line 4 and 4A in March 2021. This was Alstom's first order after acquiring Bombardier Transportation in January 2021. However, the company cancelled the order in March 2022 citing delays in completing the project.

Depot
The depot for the line is located at Mogharpada in Thane. It will also serve as the depot for Line 10 and Line 11. The depot has a maximum capacity for 64 stabling lines, half of which are reserved for future use, in addition to 10 inspection bays lines and 10 workshop lines. The depot also houses the operational control centre, administrative building, maintenance and workshop building, auxiliary substation, and staff quarters.

Pocket track
The Bhakti Park station will have a pocket track to enable trains to park off the main line. Line 4's depot at Mogharpada also serves Line 10 and Line 11 which creates the possibility of trains having to run without passengers from the depot to Chhatrapati Shivaji Terminus during morning hours. The pocket track enables trains to park off the main line without traveling to the last station on the line.