The MTHL was first proposed in the 1970s. The first concrete attempt to build it was in 2005 when the Maharashtra State Road Development Corporation (MSRDC) invited bids for the project. But bids submitted by the Ambani brothers was considered to be unrealistic. A fresh round of bidding took place for the project in 2008 but even though 13 companies had shown interest, none of them submitted bids. In August 2011, Mumbai Metropolitan Region Development Authority (MMRDA) appointed Arup Consultancy Engineers and KPMG to conduct the techno-economic feasibility of the MTHL and they are expected to submit their report by October 2012. The project will be based on a public-private-partnership model. In May 2012, MMRDA shortlisted five consortia out of six that had expressed interest in the project. They are Cintra-SOMA-Srei, Gammon Infrastructure Projects Ltd.-OHL, Concessions-G.S. Engineering, GMR Infrastructure-L&T Ltd.-Samsung C&T Corpn., IRB Infrastructure Developers Ltd.-Hyundai, and Tata Realty and Infrastructure Ltd.-Autostrade Indian Infrastructure Development Pvt. Ltd.-Vinci Concessions Development V Pte Ltd. The project received clearance from Chief Minister Prithviraj Chavan on 22 October 2012.
The project received environmental clearance from the Ministry of Environment and Forests (MoEF) on 23 October 2012. The project had received clearance in March 2005, but clearance was valid only for 5 years and lapsed due to the delays in the bidding process. MoEF has laid down 11 conditions that the MMRDA has to follow. Some of the conditions are that the MMRDA should put up noise barriers, replant five times the number of mangroves destroyed, no dredging and reclamation, use construction equipment with exhaust silencers and work in consultation with the Bombay Natural History Society to minimize the impact on migratory birds. Environmental activists are opposed to the clearance. They point out there was no public hearing following the second application for environmental clearance. They believe that the sea link is not allowed as per the new Coastal Regulation Zone (CRZ) notification of 2011. Activists also claim that the sea link would damage a huge mudflat and mangrove tract towards Sewri and Nhava which is a habitat for migratory birds like flamingos.
On 31 October 2012, the Department of Economic Affairs (DEA) granted in-principle approval for the MTHL. The DEA recommended granting 1,920 crore (US$349.44 million) with a concession period of 35 years for the project. In the first meeting, between MMRDA and DEA officials in September 2012, the ministry had asked the authority to treat the sea link as a road and reduce the proposed concession period from 45 years to 30 years. They also expected an internal rate of return of 15% for the project. However, the MMRDA wanted a higher rate as they claimed the project was very risky. An internal rate of return of 17% was agreed upon. The termination clause in the concession agreement comes into effect after 30 years into the concession period. The MMRDA can invoke the clause based on certain conditions such as the capacity being higher than expected. The conditions will be reviewed in the 20th year of the concession agreement. The DEA is the first tier of the three-tier clearance process to get viability gap funding (VGF) for the project. The project must also receive approval from an Empowered Committee and finally from the Finance Minister. On 9 November 2012, the State Government issued a state-support agreement and a toll notification for the project.
The Jawaharlal Nehru Port Trust (JNPT) has asked the MMRDA to build the MTHL at a height of 51 metres for a span of 300 metres to accommodate its expansion plans. MMRDA expressed that a height of 51 metres would not be feasible as it would have a huge impact on the cost. However, MMRDA officials expressed willingness to raise the height of the bridge to 31-35 metres.
MMRDA plans to award the contract for the project by April 2013 and to start construction by the end of 2013.
The MTHL project is proposed to commence at grade from the east side of Sewri Railway Station on the Harbour Line and proceed to Nhava and terminate at the north of Chirle village with an interchange to National Highway 4B on the mainland.MTHL will have a 16.5 km section in the sea and a 5.5 kilometre portion on land.
- Phase I :- A six lane main bridge will be built from Sewri to Nhava Sheva including approaches at grade near Sewri end, interchange at NH4B near Chirle village and underpasses at road and railway crossings. The length of MTHL road project from Sewri to NH4B is 22 km.
- Phase II:- Dispersal System at Sewri connecting Eastern Freeway and Acharya Donde Marg to MTHL (Sewri interchange).
The MTHL will have dispersals from Sewri to Worli (east-west connector) on the Mumbai-end and from Chirle to the Mumbai Pune Expressway and NH17. On the Mumbai side, the traffic dispersal will be through the Eastern Freeway (at Colaba and Wadala) and from Acharya Dhonde Marg (for West-bound traffic). The proposed Worli-Sewri Bridge will provide connectivity to the Bandra–Worli Sea Link and proposed Western Freeway
The cost of the MTHL has increased several times. In 2005, the cost of the project was estimated at 4,000 crore (US$728 million). The cost was revised to 6,000 crore (US$1.09 billion) in 2008. It was then increased to 8,800 crore (US$1.6 billion)in November 2011 and finally to 9,360 crore (US$1.7 billion) in August 2012.
The Central Governement will provide 1,920 crore (US$349.44 million), which is 20% of the project cost. The State Government will also contribute the same amount. The remaining 60% will have to be borne by the the developer who wins the bid. MTHL will be built on a public private partnership basis.
== Metro lines==
'Initially, there were plans to have a dual metro line below the road lanes on the bridge. The metro Line was to be extended to the proposed Navi Mumbai International Airport and connected to the proposed Ranjanpada-Sewood-Kharkopar corridor of the Navi Mumbai Metro and the proposed Sewri-Prabhadevi corridor of the Mumbai Metro. However, the MMRDA later scrapped plans for the metro line and decided to build only a road bridge. According to a senior MMRDA official said, “A detailed study has revealed that laying the foundation for the bridge with provisions for two metro lanes would hike costs instead of save money. Hence, it will be feasible to have a separate bridge for the metro in the future.” Other reasons given was that the Navi Mumbai International Airport and Sewri-Prabhadevi corridor of the Mumbai Metro were still a long away from completion.
== Worli - Sewri Bridge==
The MMRDA has commissioned a detailed project report (DPR) for a bridge between Worli and Sewri. The DPR will be submitted in October 2012. It will be 4.5 km long and is expected to be completed by 2017. It will begin in Worli, near the Bandra-Worli Sea Link (BWSL) and serve as a connector to the MTHL. The project will cost 500 crore (US$91 million). The bridge's construction will be independent of the trans-harbour link project.
MMRDA plans to float tenders for the project in December 2012. The bridge will be cable-stayed as pillars for the elevated road cannot be put up in the the section near the rail overbridge near the Elphinstone Road railway station because the section has a narrow carriageway. The MMRDA expects the project to be difficult to execute logistically, as it passes through a developed area and crosses the railway tracks more than once. The bridge will also have to reach a height of 27-28 metres at certain places such as the Elphinstone Road railway station to avoid the proposed Western Railway Elevated Corridor.