Green Infrastructure Plan

A hybrid approach that blends the best of gray and green infrastructure controls.

DC Water invites you to learn about the next exciting Green Infrastructure project in the District!

If you missed our April 7th presentation, join us on May 4th to learn about the next project in the Rock Creek sewershed (Rock Creek Project B). The public comment period for the associated Rock Creek Project B Project Description document began on March 29th. The public comment period for the Project Description document closes on May 7th. Comments should be submitted to

Click here for more information on Rock Creek Project B including proposed project locations of alley permeable pavement and bioretention sites.

Zoom meeting details:

When: May 4, 2021 06:30 PM Eastern Time (US and Canada)
Topic: DC Water's Rock Creek Green Infrastructure Project B

Click the link to join the webinar:

Or Join By Phone: +1 301 715 8592  
Webinar ID: 861 0659 3979

2016 Consent Decree Modification

On January 14, 2016, DC Water, in conjunction with the United States Environmental Protection Agency (EPA), United States Department of Justice (DOJ), and the District of Columbia (the District) executed a modification to the 2005 Long Term Control Plan (LTCP) Consent Decree to include innovative green infrastructure (GI) practices to achieve the reduction of combined sewer overflow (CSO) volume by 96 percent system-wide (for the Anacostia and Potomac rivers and Rock Creek) and offer additional community triple bottom line benefits. In addition to tunnels for the Anacostia River sewershed and portions of the Potomac River sewershed, the modification proposed managing 1.2 inches of rain over 365 impervious acres in the Rock Creek sewershed and 1.2 inches of rain over 133 impervious acres in the Potomac River sewershed with GI and targeted sewer separation. The 2016 Amended Consent Decree required DC Water to submit Practicability Assessments to EPA after the construction of the first green infrastructure projects in each sewershed.

The map below shows the requirements of the 2016 Consent Decree Modification including the two Green Infrastructure Program areas for Rock Creek and Potomac River Sewersheds:

Practicability Assessment and Path Forward

In the summer of 2020, DC Water submitted to the EPA the Practicability Assessments for both the Rock Creek GI and Potomac River GI projects as required under the terms of the 2016 Consent Decree Modification.  The Practicability Assessments (found in the resources section of this website) considered constructability, operability, public acceptability, efficacy, and cost effectiveness of the first set of GI projects in both the Rock Creek and Potomac River sewersheds and identified DC Water’s proposed plan to control CSO to these waterbodies. In both cases, EPA has agreed with DC Water’s assessment of GI and approved the plans to control CSOs to Rock Creek and the Potomac River. 

Potomac River Practicability Assessment

The Potomac River Practicability Assessment determined that implementation of GI to manage the required 133 impervious acres in the Potomac River sewershed (CSOs 027, 028 and 029) was not practicable from a constructability, public acceptability, and cost to ratepayers’ perspective.  Per the terms of the Consent Decree, DC Water will instead plan, design, and construct the Potomac River Storage/Conveyance Tunnel with a total storage volume of not less than 40 million gallons. The Potomac Practicability Assessment and the associated recommendations in the report, were approved by EPA on February 8, 2021.

Rock Creek Practicability Assessment

The Rock Creek Practicability Assessment determined that while GI in the Rock Creek sewershed was found to be practicable for the constructability, operability, public acceptability, and efficacy criteria, high costs to implement all 365 acres of GI coupled with ongoing costs associated with operations and maintenance resulted in the determination that GI to manage the required 365 impervious acres in the Rock Creek sewershed is impracticable. As compared to the all gray alternative outlined in the Amended Consent Decree, a full GI build-out in the Rock Creek sewershed would be nearly twice as expensive over a 30-year period when operations and maintenance are taken into consideration. Instead, DC Water proposed a “hybrid” approach for Rock Creek that blends the best of gray and green technologies. This approach provides the same degree of control as the all gray alternative, lowers capital costs below the “all gray” or “all green” alternatives, and will be implemented by 2030, the same deadline in the 2016 Consent Decree Modification. This hybrid approach is accountable to District ratepayers and delivers additional triple bottom line benefits such as more green space, habitat creation for birds and pollinators, and more local green jobs as compared to the all gray option. 

DC Water’s Hybrid Plan includes the best features of both green and gray controls in an effective and financially responsible manner.

The DC Water Hybrid Plan offers many advantages to District ratepayers and residents.

  • Best Mix of Green and Gray to Achieve Same 9.5 Million Gallons Storage. The hybrid approach achieves the same volume equivalence of 9.5 million gallons of storage as the all gray alternative by integrating the best features of green and gray for an optimized solution. 
  • Maintains DC Water’s Commitment to the Success of GI in the District of Columbia. DC Water’s leadership and stewardship in GI will continue under the Hybrid Plan to achieve economic, social, and environmental benefits for District residents.
  • Equivalent Level of Performance. Modeling demonstrates that the Hybrid Plan will achieve the same degree of CSO control as required by the LTCP.  There is no change in DC Water’s commitment to the degree of CSO control.
  • Same Technologies. The Hybrid Plan uses the same technologies as the LTCP – storage and GI to achieve CSO reductions.  There are no unproven or new technologies that may jeopardize CSO performance objectives.
  • Certain CSO Performance. The Hybrid Plan includes gray storage which has been proven reliable and effective on the Anacostia River in achieving CSO reductions, even during 2018, the wettest year on record in the District of Columbia.  
  • Fiscally Responsible. The Hybrid Plan is the most cost effective on a capital cost basis and is comparable to the gray alternative on a net present value basis.  This maintains DC Water’s accountability to ratepayers who fund the majority of the project.
  • Same Schedule.  The Hybrid Plan will be implemented with the same schedule deadline in the Amended Consent Decree – by early 2030.

The Rock Creek Practicability Assessment, and the associated recommendations, were approved by EPA on November 23, 2020. A non-material modification to the Consent Decree for the Hybrid Plan, approved by all parties (EPA, DOJ, the District, and DC Water) was filed in Federal Court on December 22, 2020. 

Completed Clean Rivers Project

The map below displays DC Water's Clean Rivers Project upon completion in 2030.

What is Green Infrastructure?

GI is an approach to managing stormwater runoff that takes advantage of natural processes such as infiltration and evapotranspiration, to slow down, clean and in some cases reuse stormwater to keep it from overwhelming sewer systems and polluting waterways.  The goal of GI is to mimic the natural environment through the use of plants, trees and other measures.

Types of GI include:

  • Roof Top Collection Practices: rain barrels, cisterns, green roofs, blue roofs
  • Permeable Pavements: porous asphalt, pervious concrete, permeable pavers
  • Bioretention: tree boxes, rain gardens, vegetated filter strips, bioswales

See the figure below to see how these processes work.

Types of Green Infrastructure in an Urban Setting (click to enlarge)

Benefits of Green Infrastructure

In addition to the control of stormwater, GI technologies like permeable pavement and bioretention provide other benefits to the community.

Site Level Stormwater Management.  GI provides water quality benefits as soon as installation begins. The GI and other improvements have allowed the District to enjoy water quality and environmental and social benefits beginning in 2017.

Triple Bottom Line Benefits.  GI offers environmental, social, and economic benefits that would not be realized under the previous plan. GI can increase property values, beautify neighborhoods, cool extreme summer temperatures, support natural habitats, enhance public space and support local green jobs.

Jobs.  DC Water has established an ambitious local jobs program that includes training and certification opportunities for District residents interested in GI construction, inspection and maintenance jobs.  The National Green Infrastructure Certification Program ( has trained and certified the first group of individuals.  DC Water has established a goal to have 51% of new jobs created by the GI project to be filled by District residents. DC Water has also engaged professional service firms and contractors based in the District to perform work associated with GI.