Line 4 (Mumbai Metro)

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 ₹64,000 crore (US$8.0 billion).[7] Chief Minister Devendra Fadnavis approved the proposal to build Line 4 on 3 June 2016,[8] and the Maharashtra Cabinet cleared the project on 27 September 2016. The project was estimated to cost ₹14,549 crore (US$1.8 billion).[9]

The foundation stone for Metro 4 was laid by Prime Minister Narendra Modi on 24 December 2016.[10] The Maharashtra Coastal Zone Management Authority granted Coastal Regulation Zone (CRZ) clearance to the project in February 2017. Over 1 km (0.62 mi) 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.[11] The agency stated that the line would require two depots due to its length.[12]

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 3 millimetres (0.12 in) accuracy. The aerial survey takes less time than a regular survey, achieves greater accuracy and helps protect against false claims for compensation.[13] In February 2017, the MMRDA stated that it was studying the feasibility of extending the corridor from Kasarvadavali to Gaimukh.[14] 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 8 km (5.0 mi) extension is estimated to cost ₹300 crore per km.[15][16] 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 ₹949 crore (US$120 million).[17][18]

The MMRDA appointed Systra MVA Consulting India Pvt. Ltd. as the detail design consultants for Line 4 on 9 November 2017.[19] 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.[20][21] 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.[22][23]

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.[24]

A construction barricade along the Line 4 route.

The MMRDA invited bids for civil work on the corridor on 4 January 2017.[26][27][28] 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.[29][30] 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.[31][32]

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 ₹1,584 crore (US$200 million).[33] The contract for the remaining two packages, worth a combined ₹1,048 crore (US$130 million), was awarded to a joint venture between Tata Projects Limited and China Harbour Engineering Company.[34] The civil work was expected to be completed in 30 months.[35] Construction began in October 2018.[36] About 80% of soil-investigation works and 66% of utility works had been completed by 3 June 2019.[37]

In September 2019, the MMRDA awarded a ₹342 crore (US$43 million) contract to J Kumar Infraprojects to build the viaduct and two stations for the Metro 4A extension from Kasarvadavli to Gaimukh.[38][39] In August 2020, the Bombay High Court granted the MMRDA permission to carry out construction in a mangrove buffer zone.[40] Survey work on the land for a depot at Mogharpada began in January 2022.[41]

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.[42] By November 2022, 41% of civil works on Line 4 and 45% of work on Line 4A had been completed.[43][44]

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) [48]

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

Line 4 is estimated to cost ₹14,549 crore (US$1.8 billion),[25] and Line 4A is estimated to cost ₹949 crore (US$120 million).[18] 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.[49]