Donaldson Run watershed in north Arlington.
100% Plan Documents
- 100% Project Plans (Plan signature form)
- Project Cost Estimate
- Summary of project design peer review (all comments have been addressed)
- The County Board approved the construction contract at their March 23, 2021 meeting. Construction is expected to being in May/June, 2021. The storm sewer pipe and outfall at the end of N. Upton Street will be repaired as part of the project.
- Story maps show before/after improvements from the Tributary A project and key elements of the Tributary B project.
About the Project
Donaldson Run has been impacted by stormwater runoff, causing excessive erosion along the stream channel. A technique called “natural stream channel design” will be used to create a new stream channel that can better manage the runoff it receives from the surrounding land. This method uses step pools, floodplain reconnection and meanders to help reduce the energy of the flow.
The Tributary B stream restoration approach is affirmed by design professionals, confirmed by peer review, and approved by regulatory agencies. EPA’s Chesapeake Bay Program considers urban stream restoration a best management practice to restore the Chesapeake Bay.
In 2006, the County completed a stream restoration of Donaldson Run’s Tributary A. The photos at the top right of this page show before and after pictures of the stream restoration.
The stream restoration of Tributary B will:
- Protect the 30” water main and sanitary sewer line. The water main within the stream valley serves 20,000 residents. Erosion in the stream valley has uncovered the water main, twice requiring emergency stabilization work. This infrastructure was not designed to be exposed and as a result is currently more prone to damage and breaks. The project will support and protect these pipes.
- Help the County meet its regulatory requirements to reduce nitrogen, phosphorus and sediment pollution. The County’s MS4 Permit requires reductions in nitrogen, phosphorus and sediment pollution. Stream restoration projects, like Tributary B, are especially effective tools to address phosphorus and sediment pollution. Arlington’s pollution reduction efforts are a part of the larger Chesapeake Bay cleanup effort.
- Improve the long-term health of the stream valley forest. The stream erosion has undermined and killed trees along the stream, and more will be damaged unless the stream valley is restored. Twenty trees have been lost in the past 2 years due to stream erosion and storm damage. The restored stream channel will be stable, and, as a result, the remaining trees and new trees planted after restoration will be protected. Over 300 new trees will be planted as part of the project.
- Restore native vegetation to the Tributary B stream valley. The area surrounding Tributary B is overrun with invasive, nonnative plants such as kudzu, porcelainberry, and English ivy. The area will be replanted with native plants that support local wildlife.
- Protect the multi-use trail. Erosion is threatening the trail in several places. This is particularly noticeable in the section that is close to the confluence with Tributary A.
Design alternatives have been suggested to stabilize the stream in its current configuration. Learn why stabilizing the stream in its current configuration isn’t effective.
Why doesn’t the County do stormwater management upstream of Donaldson Run to reduce stormwater runoff, instead of doing stream restoration?
The County is doing both – adding new stormwater management facilities in the watershed, as well as restoring streams. The Stormwater Master Plan included a study to find locations to add stormwater management facilities in local watersheds. These watershed retrofits will slow down and treat stormwater runoff, which will help water quality in our streams in the long term. However, these retrofits can’t undo the damage that development and excessive runoff have already caused to local streams. Streams that have eroded down and widened in their channel will continue to do so, washing more sediment and pollution downstream, and threatening more trees along the stream channel.
Why do trees have to be removed to do a stream restoration project? Due to the extremely tight work area, the impact that heavy equipment will have on the critical root zone of trees, and the fact that some of the trees are compromised due to stream bank erosion, some trees will be lost as a part of the construction process. Trees that are lost will be replaced following construction.
- Two tree inventories were completed for this project. The first in 2010 and the second in 2015. For each inventory, urban foresters surveyed, measured, and assessed the condition of all of the trees in the project area.
- 83 trees will be removed as a result of the project. 20 trees within the project area have been lost in the past 2 years from stream erosion and storm damage.
- 332 native trees, 180 shrubs, 200 live stakes (cuttings that will grow into trees), and more than 4000 herbaceous plants will be planted as part of the project. The planting contract includes a 5 year warranty on the plants and invasive plant control.
Why doesn’t the County use a wood based stream restoration method? Staff reviewed the suggestion that a wood-based bank stabilization/armoring would present an effective and cost-efficient method for Tributary B. Staff reached out to a firm with significant experience in this technique, which uses trees adjacent to the stream to build stability structures. Because of the steep topography and severe erosion in the Tributary B valley, a large number of these structures would be needed, and significantly more trees would be removed to build these structures than the trees that will be removed for the project as currently designed. It is also a serious concern that this approach would be less enduring for the long-term as tree material degrades in an alternating wet and dry urban stream environment— reducing project integrity over time.
|February 5, 2020||Donaldson Run Civic Association Meeting - Taylor Elementary School||
|April 27, 2017||Urban Forestry Commission Meeting|
|November 9, 2016||Donaldson Run Civic Association|
|April 18, 2012||Donaldson Run Civic Association|
|June 2, 2011||Donaldson Run Advisory Group Meeting|
|Feb. 23, 2011||Donaldson Run Civic Association|
|Nov. 20, 2010||Donaldson Run Community Stream Walk – 60% Design Review|
|June 23, 2010||Community Meeting|
|Dec. 2, 2009||Donaldson Run Civic Association|
|Nov. 14, 2009||Donaldson Run Community Stream Walk|
|Nov. 5, 2009||Donaldson Run Advisory Group Meeting|
|December 2007||Neighborhood Conservation (NC) Advisory Committee Meeting||Funding approval.|
|2005||Donaldson Run Civic Association||Votes taken to reaffirm the Tributary B stream restoration project as the neighborhood’s first-priority NC project.|
|September 2004||Donaldson Run Civic Association||Vote to designate the Tributary B project as the priority NC Program project (it was announced prior to the meeting that the vote would be taken).|
More than 10 years ago, residents of Donaldson Run Civic Association were concerned about erosion in the stream, which degrades the health of the stream and threatens nearby trees and trails. The Donaldson Run Civic Association applied for and received Neighborhood Conservation Program funding in 2001 to study Donaldson Run stream and identify potential stream improvements.
A stream restoration project was completed on Donaldson Run Tributary A in 2006. Before and after photos are in the image gallery. The Donaldson Run Civic Association was awarded an additional $350,000 in 2007 to restore Tributary B. Matching funds to construct the project will come from the Stormwater Fund.