Lower Four Mile Run in south Arlington (south of 395 to the Potomac).
About the Project
Invasive plant control along the stream was completed in September. Construction is underway, and the contractor has begun to remove the stone rip rap along the flood channel, and install living shoreline features. Construction will last approximately through Fall 2017.
A trail detour will be in place throughout much of the construction. The trail detour is in effect. As part of the construction, the Arlington trail will be completely rebuilt to current standards, including a new sub-base and asphalt surface. Improved trail railings and a new observation platform will be installed. The detour has been developed in coordination with the City of Alexandria and the local bicycle committees.
The work in the stream will include naturalization of the stream bank and construction of living shoreline features along the edge of the stream. Living shorelines are a more environmentally sensitive way to protect stream banks and coastal areas, with wetland plantings behind small stone breakwaters. They provide numerous benefits including:
- reducing erosion along the bank,
- improving water quality by capturing sediment and utilizing nutrients, and
- providing habitat for fish and waterfowl.
The existing stone rip rap that currently covers the stream banks will be removed and replaced with native vegetation that will improve the habitat quality and aesthetics of the stream channel. Some of the stone will also be reused to create the living shoreline features.
The project meets Corps of Engineers requirements to maintain flood protection, improves pedestrian access to the waterway as well as aquatic and riparian habitat. Alexandria recently completed a wetland restoration project across the stream as part of the Four Mile Run Restoration Master Plan partnership.
During the 1960s and 1970s, Four Mile Run experienced significant flooding events as the watershed became more urbanized. In 1974, Congress authorized the United States Army Corps of Engineers (USACE) to design and construct a flood control channel that would contain the increased flows.
In 2000, the City of Alexandria, Arlington County and the Northern Virginia Regional Commission (NRVC) began to explore the stream’s water quality and recreation potentials. The Four Mile Run Master Plan was completed in 2006 and the Design Guidelines in 2009.
A "demonstration project" was selected from the Master Plan to be completed first. The plans for the stream project include:
- Naturalize the banks along the corridor and improve access to the stream through overlooks and terracing.
- Replace rip-rap stone along the banks with native plants.
- Create living shorelines, which are small breakwaters built from stone with wetland plants behind them, on the Arlington side.
- The existing asphalt trail adjacent to Four Mile Run will be completely rebuilt to current standards, including a new sub-base and asphalt surface.
- New trail railings and a new observation platform will be installed.
- Restore the tidal wetland condition in Four Mile Run Park on the Alexandria side (completed).
About the Process
A Citizen's Joint Task Force (JTF) with representatives from Arlington and Alexandria was created in 2003 to help guide the Four Mile Run restoration plan. The JTF has met over the years as the project has progressed and provided input to the project.