Green Line 4 of the Mumbai Metro, currently under construction, is part of the metro system for the city of Mumbai, India and is being developed by MMRDA and a consortium of international companies.

The  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.

It is expected to be completed in 2022 and is expected to provide interconnectivity among the existing Eastern Express Highway at Chembur, Central Railway, Mono Rail, the ongoing Metro Line 2B (D N Nagar to Mandale) at Chembur, and the proposed Metro Line 5 (Thane to Kalyan) at Kapurbawdi, Metro Line 6 (Swami Samarth Nagar to Vikhroli) in Kanjurmarg and Metro Line 11 (Wadala to CSMT) in Wadala. It will provide rail based access to the commercial, government bodies and geographical landmarks in Mumbai. Dedicated depots are planned in Owale land in up to an extent of 20 ha. and in Godrej Land in up to 15.50 ha. area. It will reduce the current travel time by between 50% and 75% depending on road conditions. Alstom awarded to provide rolling stock for this line, but the contract has been cancelled in March 2022 due to delays and uncertainties of the project.

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 6 new metro lines at a total estimated cost of . Chief Minister Devendra Fadnavis approved the proposal to build Line 4 on 3 June 2016, and the Maharashtra Cabinet cleared the project on 27 September 2016. The project was estimated to cost .

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  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 utilized a drone to carry out survey work for Metro 4. The drones were fitted with 360 degrees camera that provide up to  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 stated that it was studying the feasibility of extending the corridor from Kasarvadavali to Gaimukh. In March 2017, the agency stated 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  extension is estimated to cost 300 crore per km. 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 .

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 ensure smooth flow of traffic, 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. As of February 2023, the MMRDA had still not acquired land for the depot at Mogharpada.

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 . The contract for the remaining two packages, worth a combined , 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  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.

Current status

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 , and Line 4A is estimated to cost . 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.

Infrastructure

Rolling stock 
The MMRDA awarded a  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.

References

Mumbai Metro lines