- May 2019: City begins wetlands bridge project. For updates, check the bridge construction website here.
- April 2018:City of Alexandria and Arlington County receive 2018 Governor's Environmental Excellence Silver Award,
- Fall 2017: Arlington County completed its a Four Mile Run Stream Bank Restoration Project to naturalize the stream bank and construction of living shoreline features along the edge of the stream. For more information, visit projects.arlingtonva.us
- March 2017: The City has completed design of a bridge that will connect the new wetlands trail to the softball fields.
See the design plan
- Update - January 2018: The city received a a Recreational Trails Program grant through the Virginia Department of Conservation and Recreation to construct the wetlands bridge. The City is currently obtaining permits to construct the bridge and expect its completion in Spring 2019.
- February 2017: The Four Mile Run Wetlands Restoration has won first place in the Best Habitat category of the Best Urban BMP in the Bay contest!
- May 2016: The City held a ribbon cutting for the Alexandria portion of the Four Mile Run Project, officially opening the wetlands, parking lot and trail.
Four Mile Run Overview
Four Mile Run is a nine-mile long stream located in a highly urbanized area in Northern Virginia. Its 19.6 square mile watershed covers portions of Arlington and Fairfax Counties and the Cities of Alexandria and Falls Church. The lower portion of Four Mile Run, from I-395 at the upstream end to National Airport at the mouth, is contained in a hardened flood control channel and marks a rough boundary between Arlington County and the City of Alexandria. Along this stretch of Four Mile Run are neighborhoods, commercial districts, and some industrial facilities, including the Arlington County Water Pollution Control Plant. Because of the highly urbanized nature of the Four Mile Run watershed, the neighborhoods and businesses adjacent to this portion of the run were subjected to repeated flooding, beginning in the 1940s. In response to this flooding, the municipalities forged a partnership with the US Army Corps of Engineers (USACE) to build a flood-control channel in the lower portion of Four Mile Run. Construction of that channel took place during the 1970s and early 1980s. Since its completion over twenty years ago, the channel has safely conveyed the high storm flows through the two jurisdictions and prevented flooding.
Four Mile Run Restoration Project
The restoration project is a joint venture to restore 2.3 miles of a highly degraded stream within the hardened flood control channel - or levee corridor - of Four Mile Run. Through a partnership of efforts and funds, residents and staff from Alexandria, Arlington, the Northern Virginia Regional Comission (NVRC), the US Environmental Protection Agency, the US Army Corps of Engineers and Congressman Jim Moran's office have been working collaboratively to successfully implement the framework set forth by the Four Mile Run Restoration Master Plan (2006).
The Four Mile Run Design Guidelines, as approved by Arlington County and the Alexandria Planning Commission in September 2009, were created to govern the aesthetic and physical components of the stream corridor. The Design Guidelines include recommendations that will guide trails and paths, stream crossing, bridges, lighting, building orientation and setbacks, benches, the proposed Nature Center, and vegetation; among other physical components.
- Staff report
- Available for download as separate chapters on NVRC's website
- Full document (this is a very large file)
A citizen-led Joint Task Force (JTF), with representatives appointed by the chief administrative officers of each jurisdiction, examines project alternatives, gathers public input, and provides recommendations to the project's Agency Coordination Group (ACG). Members of the ACG represent the various local, regional, and federal government agencies involved in the planning and implementation of the restoration effort. A list of JTF members and an archive of meeting summaries are available on the project website.
NVRC is facilitating the administration of the Four Mile Run Restoration Project and additional information related to the project can be found on their website.
Tidal Restoration Demonstration Project
In May 2016, the City of Alexandria completed the Tidal Restoration Demonstration Project to restore the banks of the shoreline and wetlands in the channelized portion of Four Mile Run, from Mt. Vernon Avenue to Route 1, as described below.
A major objective of the Master Plan was to reestablish the vegetation that once lined the stream and existed in the lowland wetlands areas but has since disappeared or been colonized by invasive species. The Four Mile Run Wetlands Restoration plays a prominent role in regional efforts to protect the Potomac River basin and the endangered Chesapeake Bay by restoring the natural cycles and diversity of habitat to support a variety of life in and along these waterways. The Restoration project restored the historic 2-acre tidal wetland where the water levels fluctuate with the daily tidal cycle along Four Mile Run. Wetlands were once common along all the tidal tributaries and protected shorelines of the Potomac River, but many tidal wetlands have been lost to urban and suburban shoreline development. The upland trail serves as a buffer between the tidal wetland and the existing forested wetland. Wetlands are important to both wildlife and humans and provide a connection between aquatic and terrestrial habitats that is important to fish and aquatic organisms as well as many birds and terrestrial animals. Tidal wetlands are important nurseries and foraging areas for fish, waterfowl and other birds, reptiles and mammals. Wetlands also benefit humans by improving water quality and storing floodwaters.
Tidal wetlands can be divided into different plant zones based on fluctuating water depths. This created wetland includes a low marsh zone and a high marsh zone and is surrounded by an upland meadow.
The low marsh zone is typically flooded for more than ½ of the day by water up to several feet deep. This extensive inundation limits the diversity of plants that can grow in this zone. Common low marsh plants, such as the yellow pond-lily (Nuphar advena) and the arrow arum (Peltandra virginica), provide cover for juvenile and adult fish and other aquatic species. The ten-foot tall, emergent grass, wild rice (Zizania aquatica), was an important food crop for Native Americans and remains an important food source for water fowl. The prolonged and deep inundation by tidal waters allows the low marsh vegetation to take up nutrients and trap sediments from the flood waters.
The high marsh is flooded less than ½ the day by water that is typically less than one-foot deep. The vegetation community is composed of many species that form a dense cover. Grasses, sedges and rushes, such as rice cut grass (Leersia oryzoides), soft rush (Juncus effusus), woolgrass (Scirpus cyperinus) and three-square (Schoenoplectus pungens) are common in the high marsh, as are forbs such as rose mallow (Hibiscus laevis), broadleaf arrowhead (Sagittaria latifolia), and swamp milkweed (Asclepias incarnata). The diverse plant community provides habitat to many insects, amphibians, birds and other animals. The high marsh is not inundated for long periods, but the dense vegetation is efficient at capturing sediments and pollutants from floodwaters.
The upland meadow is a perennial herb community that is not regularly flooded. It provides terrestrial habitat utilized by many of the same species that live in the wetland; frogs forage in the meadow and turtles nest here. A mix of grass species and flowering herbs, such as black-eyed Susan (Rudbeckia hirta) and goldenrods (Solidago spp.), provide foraging and nesting habitat for many song birds and provide nectar and act as larval hosts for native pollinators while providing cover habitat for other wildlife. The meadow vegetation also provides soil stabilization and erosion control.
The City also renovated the parking lot at Mount Vernon Avenue. The parking lot renovation included twenty marked parking spaces on permeable pavers, a turnaround for drop-off and pick up, a rain garden and additional trees.
Pedestrian/Cyclist Bridge Competition
In Spring 2010, the City of Alexandria, Arlington County, in partnership with the Northern Virginia Regional Commission, held a Bridge Design Competition and Call for Qualifications for the design of the Four Mile Run Pedestrian-Cyclist Bridge. This step began the formal design and technical engineering process for this bridge envisioned in the Four Mile Run Restoration Master Plan. Since the design competition, Arlington, Alexandria, NVRC and the Virginia Department of Transportation worked to develop the Scope of Services for the design and engineering. The jurisdictions began the design process with the engineering firm Buro Happold based on their concept here. The bridge design is nearing completion. More information on the project can be found on the NVRC Website.