In February 2015 the Ministry of Ecology issued a negative report, and the project was placed on hold pending completion of a new land use study for the City Council. In June Paris Mayor Anne Hidalgo announced that construction permits had been signed, with a new cost estimate of $450 million and completion further delayed to 2019. Opponents, who objected to the demolition of 2.5 acres (1 hectare) of greenhouses and biological gardens at the Jardin des Serres d'Auteuil on the eastern border of the current ground, proposed an alternate, northward expansion into the Bois de Boulogne that would require covering a portion of the A13 highway. Proponents of the eastward expansion argued that further delays would jeopardize Paris's bid for the 2024 Olympic games.