Contracts Approved for Four Mile Run Restoration, Stormwater Improvem

Published on June 18, 2016


  • $3.5 million contract for Four Mile Run habitat restoration

  • $3.5 million stormwater contract for West Little Pimmit Run

  • Protecting Chesapeake Bay

  • Reducing flood risk


The Arlington County Board today approved contracts for two projects, one to restore the lower section of the Four Mile Run stream and another to upgrade the storm sewer and install new water mains and four facilities to filter stormwater runoff in north Arlington. Both projects will benefit our local streams and the Chesapeake Bay.

Four Mile Run restoration


The Board approved a $3.5 million contract to restore the lower section of the Four Mile Run stream. This will implement the first phase of the Four Mile Run Restoration Master Plan, approved in 2006. The plan envisions restoring the corridor as a place where Arlington and Alexandria residents can gather, recreate, and celebrate a shared stream.

"The Four Mile Run Restoration Project has been a long time in the making and its great to finally see progress," County Board Chair Libby Garvey said. "This project exemplifies Arlington's commitment to restoring our streams and protecting the health of the Chesapeake Bay — and would not be possible without the collaboration of our community and our watershed neighbor, Alexandria."

The Board voted unanimously as part of consent agenda to approve the contract.

Naturalizing a stream bank


The project will naturalize the stream bank and construct living shoreline features along Four Mile Run between Mount Vernon Avenue and Route 1. The living shorelines will reduce erosion along the bank, improve water quality by capturing sediment and utilizing nutrients, and provide habitat for fish and waterfowl. The stone riprap that currently covers the stream banks will be replaced with native plants that will improve the habitat quality and aesthetics of the stream channel.

In addition, the asphalt trail adjacent to the project will be completely rebuilt to current standards, including a new sub-base and asphalt surface. Trail rails will be improved, and an observation platform added.

The project meets U.S. Army Corps of Engineers requirements to maintain flood protection and improves pedestrian access to the waterway. Alexandria recently completed a wetland restoration project across the stream as part of the Four Mile Run Restoration Master Plan partnership.

Meeting MS4 permit goals, funding


A key component of the County's Stormwater Management Program, this project will contribute nutrient and sediment reduction credits toward Arlington's Chesapeake Bay Total Maximum Daily Load reductions required under the County's Municipal Separate Storm Sewer System (MS4) permit. Arlington has U.S. Environmental Protection Agency State and Tribal Assistance Grant funding to offset 55 percent of total project costs, up to a maximum reimbursement of $1.74 million.

Trail detour required during construction


The project is expected to begin in late summer and last about one year. Several Four Mile Run trail detours will be in place throughout much of the construction. These detours have been developed in coordination with the City of Alexandria. The public will be notified in advance through many channels, and there will be signs on the trail.

Background


During the summer of 2000, Arlington County and City of Alexandria residents participating in the Potomac Yard planning process were inspired to restore lower Four Mile Run. Although successful in controlling flooding, the Four Mile Run flood channel suffers from severely diminished habitat and environmental features, recreational opportunities and aesthetics.

A joint task force was appointed in summer 2003, with members from each jurisdiction. The task force led an extensive public process to improve Four Mile Run, and in 2006, the Four Mile Run Restoration Master Plan was adopted. The Four Mile Run Design Guidelines followed in 2009. Initial designs for a new pedestrian bridge across the stream have been completed and the Alexandria wetland restoration project has been completed.

To read the staff report on this item, visit the County website. Scroll down to Item No. 23 on the Agenda for the June 18, 2016 Regular County Board Meeting. Visit the project website for updates and more information.  Scroll down to Item No. 23 on the Agenda for the June 18, 2016 Regular County Board Meeting. Visit the project website for updates and more information.

West Little Pimmit Run project


In a separate action, the Board approved a $3.5 million contract to upgrade the storm sewer, install new water mains and four green street "bioretention" facilities to filter stormwater runoff for West Little Pimmit Run. The project is located at Nottingham Street and John Marshall Drive, and North Kensington Street along 33rd Street North. Approximately 1,500 feet of existing 48-inch storm sewer pipes will be upgraded to 54- or 60-inch pipes.

"As Arlington continues to grow — and to age — it is critical that we invest consistently in upgrading and maintaining our infrastructure," County Board Chair Libby Garvey said. "This project will help ensure we're protecting public safety during heavy rains, as well as our streams and the Chesapeake Bay."

The Board voted unanimously as part of the consent agenda to approve the contract.

Reducing flooding risk


A severe storm in June 2006 caused extensive flooding in this area. Homes were inundated, streets flooded and vehicles damaged. A County-wide study of the storm sewer system identified a need in this area for increased capacity. The planned upgrades to the storm drainage system were adopted in the 2014 Stormwater Master Plan. The additional capacity will significantly reduce flooding risk.

In conjunction with the sewer project, the gas line will be relocated and drinking water lines will be installed on both sides of John Marshall Drive between Williamsburg Boulevard and Little Falls Road. Existing six-inch water lines built in the early 1950s will be upgraded to a new eight-inch water line. This upgrade will enhance the performance and reliability of the County's water distribution system along John Marshall Drive.

Bioretention facilities will reduce stormwater


Four street bioretention facilities will be installed as part of the project. One will be installed on 32nd Street North, another will be installed on North Kensington Street and two on John Marshall Drive. Bioretention removes contaminants and sedimentation from stormwater runoff, in this case, by creating a "green street" that will include a landscaped area in the public right-of-way that slows down and filters stormwater runoff before it enters our local streams, and eventually the Chesapeake Bay. Green streets are one of the best tools the County has available to meet Arlington's required stormwater pollution reduction goals.

Construction is anticipated to begin in late summer/fall 2016 and will last approximately one year.

To read the staff report, for this item, visit the County website. Scroll to Item No. 24 on the Agenda for the Saturday, June 18 County Board Meeting.