Beginning in 2017, the City's Department of Environmental Protection built several miles of high-level storm sewers (HLSS) to prevent stormwater from flooding the city's sewage system. The new storm sewers carry stormwater collected in new and existing catchment areas, preventing it from entering the sewage system. The first phase, comprising sewer installations south of Douglass Street, was supposed to be completed by summer 2018; a second phase north of Douglass Street would proceed from 2018 to 2020. The HLSS, built on a area east of the northern end of the canal, are planned to capture half of the stormwater within the Gowanus Canal's watershed.