This project will focus on four watersheds - Hickey Run, Nash Run, Fort Dupont, and Pope Branch. The Hickey Run and Nash Run watersheds are located near the northeastern to eastern borders of DC and on the western and eastern sides of the Anacostia River, respectively. The Fort Dupont and Pope Branch watersheds extend to the southeastern border of DC, on the eastern side of the Anacostia River. The locations of potential GI BMPs for this project will be within the DDOT right-of-way. The impacted ANCs include 5C, 7B, 7C, 7D, & 7E.
The goal is to capture, retain, and manage runoff from approximately 360,000 square feet of impervious surfaces across the four sub-watersheds using green infrastructure practices. Each facility will be designed to manage, at a minimum, the first 1.2 inches of stormwater collected from each drainage area during storm events. Selection of locations and which type of green infrastructure practice is used depends on the available space within the right-of-way and the size of the drainage areas, as well as site conditions such as topography, presence of driveways and walkways, parking needs, utility conflicts, and feasibility of construction.
Site Selection Process
In order to efficiently and systematically select BMP or Best Management Practice system locations, the team used a planning process to identify several hundred potential locations for green infrastructure facilities throughout the project areas. As the project moves forward through subsequent design phases, the list of locations is expected to be narrowed to approximately 30 to 50 facilities depending on site-specific conditions which make some locations more favorable than others. At the local level, the goal is to provide enhancements to the community, maintain safety, and improve conditions for the environment.
The initial planning and site selection process included utilizing GIS data available from DC agencies and utility companies and defining screening criteria for factors that affect where BMPs can be located such as proximity to utilities and site features (such as existing trees), drainage area size, soil conditions, topography, and other elements. This screening process is used to rank or eliminate potential locations for GI systems.
Potential GI BMP locations identified in the site selection process were also visited in person to confirm the accuracy and completeness of the GIS data used and identify other potential conflicts. Additional screening considerations such as pedestrian circulation, driveway entrances, walkways, on-street parking, adjacent building types and locations, and safe access issues for each site were also evaluated during the site visits.
Public Outreach & Communication
As part of the early planning process, a comprehensive public outreach and community involvement plan was developed to guide how the project team informs and gathers feedback from residents. This plan includes a website to easily share information and updates on the progress of the project as well as information presented at Advisory Neighborhood Commission (ANC) meetings. Presentations at meetings for ANCs located within the project limits will be conducted to provide the community with details and updates on the project, the project goals, the types and potential locations of GI BMPs to be installed, answer questions, and gather feedback from the residents.
Design Process and Timeline
The Preliminary Design Phase (30% design phase) focused on evaluating each of the recommended site locations in greater detail using the collected GIS data and information gathered during site visits to establish GI system footprints and contributing drainage areas for the selected systems. Combination and treatment train systems were prioritized with a preference toward bioretention BMPs and systems with the highest cost to benefit ratio. The overall number of GI BMP systems was further refined to align with the project goals, specifically the goal of capturing and treating runoff from 360,000 square feet of impervious area within the right-of-way (ROW).
Additional Investigation and Data Collection will follow the 30% design phase which will include geotechnical investigations and site surveying for each BMP location.
The project is currently on the Intermediate Design Phase (65% design phase). This phase includes finalizing BMP system types, site selections, and sizes of BMPs. This phase also includes developing detailed design plans, construction details, and preliminary project specifications. By the completion of this phase, the project will have been designed to meet the water quality goals assigned. Public outreach will continue throughout this phase to gather additional feedback, and this feedback will be incorporated into the final design.
The Final Design Phase (90-100% design phase) involves completing the final detailed design documents which will be used for bidding the project for construction.