Gowanus Canal was once a system of tidal creeks that came through a salt marsh and was fed by freshwater streams. Now, it’s home to coal tar residue and decades of industrial waste.

However, a cleanup process of a brownfield began Monday and is expected to take around 18 months. Residents and activists are worried about the coal tar residue, but the Department of Environmental Conservation is planning to achieve levels of cleanliness that will protect public health and the environment.

“Maybe a few years are taken off my life expectancy,” said Martin Bisi, a member of Voice of Gowanus. “That’s possible because where I live and work, there’s flooding and the flooding moves this stuff around and that’s the problem.”

The cleanup process includes scraping off the disposal of petroleum, water treatment to break down and dissolve petroleum, installation of a vapor mitigation system and a system of recovery wells.