DC Water will use green infrastructure to manage heavy rainfall and to prevent sewage overflows into the Potomac River and Rock Creek, the utility announced.

The new plan forms part of an agreement signed this week with the District of Columbia, the U.S. Environmental Protection Agency and the U.S. Department of Justice, modifying a 2005 federal consent decree to allow large-scale green infrastructure installations to form part of the long-term strategy for curtailing combined sewer overflows and improving water quality in the Rock Creek and Potomac watersheds.

Green infrastructure makes use of vegetation, soils and natural processes that mimic nature, to soak up and store rainwater where it falls.

The water and sewer authority for the District of Columbia said that it would install infrastructure such as rain gardens, green roofs and porous pavements instead of a previously planned underground tunnel for Rock Creek. Portions of the combined sewer system in the area will also be separated.

For the Potomac River, DC Water will build an underground tunnel that can hold up to 30 million gallons of combined stormwater and sewage and send it to the Blue Plains Advanced Wastewater Treatment Plant. The authority also has plans for green infrastructure and targeted sewer separation to manage runoff in this area.

“Since 2011, DC Water has explored green infrastructure as a tool to reduce combined sewer overflows,” said George S. Hawkins, CEO and general manager of the authority. “Today’s updated agreement ensures that the Rock Creek and the Potomac River will receive water quality improvements that are comparable to the previous tunnel-only plan while also supporting natural habitats, enhancing public spaces, and supporting local jobs.

“The modified construction schedule will also reduce the burden on our ratepayers by mitigating the scale of future rate increases needed to finance the $2.6 billion project.”