The project seeks to stabilize excessive & ongoing stream erosion negatively impacting water quality, undermining trees, threatening the riparian corridor, and degrading habitat for aquatic life.
Project components include:
Install instream structures to direct flow, alleviate erosive forces on stream banks, and provide instream habitat
Raise the stream channel bottom to allow water to spread out over the floodplain
On a tributary to the main channel, stabilize a headcut & debris jam holding back sediment from channel erosion upstream
Control non-native invasive plants
Reforest the site with native trees, shrubs, and plants
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Popes Head Creek at Brecon Ridge Resident Meeting
1. A Fairfax County, VA, publication
Department of Public Works and Environmental Services
Working for You!
Headwaters of
Popes Head Creek
@ Brecon Ridge
(PH9271/PH9272)
Project No. SD-000031-220
Springfield District
Tax Map No. 067-2 & 068-4
March 2021
2. Stormwater Planning Division
Agenda
• Stormwater Program Drivers
• Watershed
• Project Goals
• Existing Conditions
• Typical Restoration Practices
• Example Construction Efforts
• Example Completed Projects
• Next Steps
2
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
3. Stormwater Planning Division
Stormwater Program Drivers – Water Quality area
The Clean Water Act of 1972
Regulate pollutant discharge to the Waters of the U.S.
Chesapeake Bay Preservation Act
Program to improve the water quality in the Chesapeake Bay
Other State & Federal Standards
– Municipal Separate Storm Sewer System Permit (MS-4):
– Total Maximum Daily Loads (TMDL)
Popes Head Creek is an impaired water for bacteria (E. coli) and for benthics (sediment)
3
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
4. Stormwater Planning Division
Fairfax County Watersheds
4
Project site in the
Popes Head Creek
watershed
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
5. Stormwater Planning Division
Project Goals
5
The project seeks to stabilize excessive & ongoing stream erosion negatively impacting
water quality, undermining trees, threatening the riparian corridor, and degrading
habitat for aquatic life.
Project components include:
• Install instream structures to direct flow, alleviate erosive forces on stream banks,
and provide instream habitat
• Raise the stream channel bottom to allow water to spread out over the floodplain
• On a tributary to the main channel, stabilize a headcut & debris jam holding back
sediment from channel erosion upstream
• Control non-native invasive plants
• Reforest the site with native trees, shrubs, and plants
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
7. Stormwater Planning Division
Existing Conditions
7
A short distance
downstream from
Braddock Road.
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
8. Stormwater Planning Division
Existing Conditions
8
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
Slightly
downstream
from the first
residential
property
along Popes
Head Creek.
9. Stormwater Planning Division
Existing Conditions
9
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
Vertical bank with
undercut and
exposed tree roots.
10. Stormwater Planning Division
Existing Conditions
10
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
Dry, friable
soil
sloughed
under its
own weight.
11. Stormwater Planning Division
Existing Conditions
11
Location is approximately 300 linear feet up the unnamed
tributary to the Popes Head Creek mainstem.
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
May 2020
November 2020
Yellow arrows identify the same small beech
tree adjacent to the debris jam/headcut.
Comparison showing the loss of woody debris
in ~6 months.
12. Stormwater Planning Division
Existing Conditions
12
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
Another large tree
being undermined
by stream flows.
13. Stormwater Planning Division
Existing Conditions
13
Tree being
undermined.
Channel eroded
down to bedrock.
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
14. Stormwater Planning Division
Existing Conditions
14
Another outside
meander where
trees on the outside
bank are being
undermined due to
increased sheer
stress.
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
15. Stormwater Planning Division
Existing Conditions
15
Fallen tree took a portion of the
channel bank down to the
existing water surface.
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
17. Stormwater Planning Division
Typical Restoration Practices – Brush Run
17
In stream woody
structures catch
debris/detritus
providing habitat for
fish and other aquatic
life.
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
18. Stormwater Planning Division
Typical Restoration Practices – Root Wads
18
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
For roughness & habitat.
19. Stormwater Planning Division
Typical Restoration Practices – Toe Log Structure
19
Toe logs provide
armoring & direct
flows away from the
bank.
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
20. Stormwater Planning Division
Example of Construction Access Road
20
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
Access road - typically
wood timber matting
underlaid with mulch
for construction
equipment to travel.
22. Stormwater Planning Division
Design consideration – Tree Removal
22
• 1,095 trees surveyed
• 240 proposed for removal. Of these, 15 are dead & 67
are assessed as either dead or in poor health.
• Please keep in mind that we have a general alignment
that is still to be engineered. As we move through an
iterative design process, decisions will be made to
preserve as many tree as possible.
• Removed trees can potentially be reused as natural
structures within the stream (e.g., log sills, root wads, and
habitat logs)
Evaluated trees are marked
with tree tags. This helps us
identify trees when reviewing
design plans and when in the
field.
Headwaters of Popes Head Creek @ Brecon Ridge Stream Restoration
23. Stormwater Planning Division
* Following Planting Density Requirements, as part of
project construction & for every disturbed acre we will plant:
• 100 overstory trees
• 200 understory trees
• 1,089 shrubs
* proposed quantities of plants will be provided at the 65%
Design plan
23
Native Plants – woody & herbaceous material examples
29. Stormwater Planning Division 29
Dead Run Segment 1
March 2016
May 2020
(∼2 Years after
construction
completion)
Completed Project Examples
30. Stormwater Planning Division
Next Steps
30
• Easement Acquisition
• Complete Design
• Permitting
• United States Army Corps of Engineers
• Virginia Department of Environmental Quality
• Fairfax County
• VDOT
• Construction
• Approximate duration: ~14 months
• Post Construction
• Completed project carries 1-year warranty
• After warranty period, County assumes
monitoring & maintenance responsibilities
31. Additional Information
For additional information, please contact
www.fairfaxcounty.gov/publicworks
Stormwater Planning Division 31
Dave Anglin, Section Chief
www.fairfaxcounty.gov/publicworks
dave.anglin@fairfaxcounty.gov
For additional information, please contact
571-722-8515
Editor's Notes
This seems like a long agenda, I would suggest paring it down. Your audience is probably really focused on the project, this agenda, with the exception of project goals seems like a presentation on environmental programs and practices.
MS4: Under this permit, we need to have programs to regulate pollutant discharge
TMDLs: Under this permit, we need to have programs to regulate pollutant discharge. Local TMDLs include bacteria (12), sediment (3), & PCB’s along the tidal Potomac area.
Emphasize that the soil being eroded is from the home lots & the HOA property.
A triple box culvert outfall from under Braddock Road. The watershed extends north almost to Lee Hwy & south of the mobile home development. Other portions extend east to West Drive in Fairfax City & west along Shirley Gate Road. Incised channel bank height averaging 5.5 feet in this area.
The channel is deeply incised on each bank side. Most vegetation close to the bank edge is seasonal, herbaceous cover and/or turf grass. A few small trees are visible on the left bank. However, note the incised left bank extends from the foreground through the downstream extent visible in the photograph.
Beyond being at risk of loss due to erosion, the tree’s critical root zone has been severely compromised. This risks root decay that will hasten tree loss.
Visible where the stream flow meets the raw bank is friable soil that sloughed off under its own weight. So, a variety of factors contribute to soil loss beyond just water flows.
Unstable debris jam at a headcut that is holding back sediment accumulated from the upper reaches of this unnamed tributary to Popes Head Creek. When the debris jam fails, the accumulated sediment will be discharged downstream. It is also likely that the headcut here will begin to erode upstream again.
As with other locations, this tree is at high risk of loss due to being undermined &/or root decay.
Ensures that erosive force will be expressed on the channel banks leading to cutting & channel widening.
This also blocked a portion of the channel area causing eddying & water flows against the raw soil increasing erosion on the down stream side.
Root wads can be placed along meanders (bends) to armor/protect the bank. These wads also act as some roughness to help manage water velocity. Root wads also provide habitat & cover for fish & other aquatic life.
Using logs in this manner also incorporates native woody material into the channel mimicking natural stream banks & re-uses material on site.
This matting & mulch disperse equipment weight & decrease tree root impacts & soil compaction.
Above - newly graded & stabilized stream channel through a series of step pools.
Below – placing large stone creating a step pool to lower stream flows over steep grade in a controlled manner .
We work closely with Urban Forest Management Division staff, arborists, and landscape architects to minimize impacts and preserve trees.
All trees within a project area with a diameter equal to/greater than 12 inches were surveyed, tagged, and species, diameter size, and health are recorded.
DO you have an after picture that is green and shows the extent of planting