Despite a long battle fought by environmental activists and local people to save what is known as Mumbai's 'green lung', the car shed construction in Aarey is nearing completion with 95 percent of the work already finished.

The controversy, which had simmered for over a decade, saw a reversal of earlier decisions when the BJP-led government returned to power in Maharashtra in 2022 after a political split in the ruling Shiv Sena. Soon after forming the government, it reversed the previous administration’s decision to shift the car shed to Kanjurmarg and reinstated the original site in Aarey for construction. On 11 October 2020, Maharashtra Chief Minister Uddhav Thackeray had declared that the car shed would be shifted out of Aarey forests and would be built on government land in Kanjurmarg in central Mumbai. The chief minister had also directed the police to withdraw all cases filed against Aarey protestors.

Although the government declared 25% of Aarey forest as reserved forest in 2022, it excluded the car shed site from this declaration. Environmental activists argued this partial protection was insufficient to safeguard the area’s biodiversity and the rights of its indigenous communities.

Aarey Colony is home to a large number of tribespeople, who have lived in the area for generations and run cowsheds that supply milk to a government-run dairy. They have been opposing the metro car shed since it was proposed in 2011. They claimed that construction activity had destroyed a portion of wetlands in the area, which is crucial for streams to flow. Aarey is the catchment area of the Mithi river. Environmental experts too warned that any construction in the area could cause flooding.

Work on the depot had originally begun in 2015, only to be halted by the Supreme Court in October 2019 following a public outcry over the felling of over 2,700 trees. Despite the court's stay, substantial damage had already occurred by the time of its order, following an earlier order of the Bombay High Court that allowed the felling of trees. On 8 October 2019, local tribal communities held a symbolic funeral for the lost trees and displaced wildlife.

The Mumbai Metropolitan Region Development Authority (MMRDA) had announced the 20-km-long Colaba-Bandra Metro Line in January 2004. The plan encompassed 146 kilometres of railway track, of which 32 kilometres was to be underground. In 2011, the MMRDA proposed to extend the Metro Line. A car shed was proposed on 33 hectares as part of the expansion. But following protests by the residents, the area for the car shed was scaled down to 20.82 hectares.

After the Ministry of Environment, Forests and Climate Change (MoEFCC) declared Aarey Colony an eco-sensitive zone (ESZ), the state government considered a private plot at Royal Palms, a residential project of Royal Palms India, according to the managing director of the Mumbai Metro Rail Corporation. However, this, too, has been opposed by the residents as Royal Palms is situated inside Aarey Colony and is, therefore, a part of the ESZ.

On 15 April 2019, the Supreme Court dismissed the application filed by social activist Amrita P Bhattacharjee challenging Aarey Colony as the site for the metro line. While dismissing the petition, the court referred to the report of the Technical Committee on the feasibility of the metro depot in Aarey Colony.

In September 2019, the MMRDA announced its plan to acquire 29,869 square feet of Aarey forest for a site office, labour camp and casting yard for the Andheri-Kanjurmarg Metro Line 3. The state government had given permission for the land acquisition, but after mass public protests, the MMRDA shelved its plan to acquire land in Aarey and decided to take up a plot of land in Wadala to build the casting yard. The MMRDA came under flak from local people, green activists and celebrities alike, who joined hands for the Save Aarey campaign.

Earlier in 2016, the National Green Tribunal (NGT) had upheld the MoEFCC's decision to reduce the size of land for development purpose to 407 acres - roughly the size of 18 Oval cricket grounds - from the entire 15,000 acres of land in Aarey notified as ESZ. The ministry justified the reduced ESZ and said that the Metro car shed would be built in the excluded zone. Mumbai-based non-profit Vanashakti had challenged this decision in the Supreme Court. On 16 June 2020, the apex court dismissed the plea, observing that "Mumbai was a congested city and Metro is important".

The 25-acre car shed at Aarey would serve as the base for maintaining metro coaches for Mumbai Metro Line 3. The 33.5-km long Metro-3 running along Colaba-Bandra-SEEPZ is the first underground metro corridor of Mumbai. With an estimated project cost of Rs 33,000 crore, the project has received funding from several entities, including Japan's technical and lending agency, the Japan International Cooperation Agency (JICA).