Turkish President Recep Tayyip Erdogan’s project to build a canal in Istanbul will cost around $15 billion, according to the nation’s transport minister.

“We will break the ground for the first bridge by the end of June,” Adil Karaismailoglu, minister of Transportation and Infrastructure, told state-run TRT on Friday. The six bridges spanning the canal will cost $1.4 billion, the minister said.

The 45-kilometer (28-mile) Canal Istanbul, which will link the Black Sea with the Sea of Marmara, was dubbed by Erdogan as his “crazy project” when he first announced it a decade ago. The waterway is projected to create a city with a population of half a million.

Critics say they’re concerned the venture will impact an international agreement regulating the traffic through the Bosporus and the Dardanelles straits and meant to ensure stability in the Black Sea region.

Erdogan has said Turkey won’t exit the treaty but sees the Canal Istanbul as an alternative to it as the project will enhance the government’s control of shipping to and from the Black Sea. Opposition parties say commercial ships can’t be forced to take the alternative route and the canal would hit taxpayers and the environment.

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The canal would “annihilate” water resources for Istanbul’s 16 million residents, ruin the province’s nature beyond repair and make it uninhabitable, according to Ekrem Imamoglu, the mayor of the nation’s largest city. Erdogan’s government has brushed off such concerns.

Karaismailoglu said the government will build two new dams to make up for the water loss due the project.

During the president’s 18-year rule, Turkey has poured tens of billions of dollars into giant infrastructure projects, including the new Istanbul airport, a new bridge over the Bosporus and massive city hospitals.