DC Department of Energy and the Environment, together with DC Water, have had a long-term commitment to the restoration of Pope Branch, a mile-long urban stream. In addition to the common challenges to aquatic resources resulting from watershed development and the desire to provide attractive public open space in the District, there were significant infrastructure issues that needed to be addressed. In the case of Pope Branch, DC DOEE is responsible for the protection of the stream and associated resources while DC Water is dependent on the Pope Branch stream valley for their wastewater conveyance network. Five projects, including two design-build regenerative stormwater restoration gully repairs, one urban stormwater treatment community open space, sewer pipe repairs/updates, and approximately one mile of stream restoration, were successfully implemented over a five-year period.
Results/Conclusions
The focus of this presentation will be a discussion of the restoration of the approximately mile-long perennial Pope Branch. The Pope Branch Stream Valley Park is a large, high value forested park with a drainage area of about 0.5 square miles of highly urban land. Biohabitats, and Underwood & Associates were selected to implement the design-build of the two RSC’s and the stormwater community park. Biohabitats was also selected to design and permit the mile-long Pope Branch stream restoration project, and Underwood & Associates won the construction implementation of the project. The project was successfully implemented in the Fall and Winter of 2016. The restoration approach included a special pool design to reduce maintenance at the downstream end of Pope Branch before it entered an approximately 1,400-ft long culvert under I-295 which conveys the flow to the Anacostia. Prior to the project, this culvert filled with sediment and debris and led to local road flooding. All along the flow path, the stream elevation was raised to improve floodplain connection and reduce the symptoms of urban hydrology (i.e., reduce peak discharge and increase time of concentration). At the upstream end, the earlier mentioned RSCs and other upland watershed projects reduce the discharge of stormwater, nutrients and sediments to Pope Branch. Together, these restoration projects have reduced TSS, TN, and TP annual loadings by 744 tons of TSS, 450 lbs of TN, and 408 lbs of TP, based on the Maryland Department of the Environment's guidance document (MDE 2014). These nutrient reductions are dwarfed by the reductions associated with the repair of leaking sanitary sewers.