This document summarizes a proposed stream restoration project in Fairfax County, VA. It describes the existing failing gabion walls and eroding stream banks. The proposed project would replace the gabion walls with more natural stream restoration structures like cross vanes, root wads, and boulder toes to stabilize the banks. It would also add planted buffer zones and benches along the stream. The project requires designing temporary construction access given the steep slopes, and coordinating with other planned restoration work. It outlines the conceptual design, approval, and construction schedule.

1. A Fairfax County, VA, publication
Department of Public Works and Environmental Services
Working for You!
Columbia Road/Randolph Court
Stream Restoration
July 6, 2015

2. Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Meeting Outline
• Fairfax County Stormwater Management
• Project Existing Conditions
• Proposed Stream Restoration
• Construction Access
• Design Schedule
• Questions
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3. Stormwater Planning Division
Columbia Road/Randolph Court Stream Restoration
Stormwater Management
3
Department of Public Works and
Environmental Services
Land
Development
Services
Capital
Facilities
Solid Waste Stormwater
Stormwater Planning
Division
Maintenance and
Stormwater
Management Division
Wastewater

4. Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Stormwater Infrastructure
• Conveyance System
– 1,600 miles pipe and
paved channel
– 43,000 structures
– 6,800 outfalls
• Management Facilities
– 1,540 County Maintained
– 3,720 Privately Maintained
• State Regulated Dams
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5. Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Service Drivers
In response to The Clean Water Act of 1972
• National Pollutant Discharge Elimination System (NPDES)
• Virginia Stormwater Management Program (VSMP) Regulations
• Municipal Separate Storm Sewer Permit (MS4)
• Total Maximum Daily Loads (TMDLs)
– Chesapeake Bay
– Local Streams
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6. Stormwater Planning Division
Columbia Road/Randolph Court Stream Restoration
Watershed
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Watershed:
Cameron Run
Subwatershed:
Indian Run

7. Stormwater Planning Division
Columbia Road/Randolph Court Stream Restoration
Project Location
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8. Stormwater Planning Division
Columbia Road/Randolph Court Stream Restoration
Existing Conditions- 4717 Columbia Road
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120 feet of failing gabion walls
Angled culvert outlet
discharging at high velocity
eroding gabion wall toe

9. Stormwater Planning Division
Columbia Road/Randolph Court Stream Restoration
Existing Conditions- 4717 Columbia Road
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10. Stormwater Planning Division
Columbia Road/Randolph Court Stream Restoration
Existing Conditions - 4713 Randolph Court
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100 feet of failing gabion walls
Sanitary sewer adjacent to
gabion wall failure

11. Stormwater Planning Division
Columbia Road/Randolph Court Stream Restoration
Existing Conditions - 4713 Randolph Court
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Runoff from grass floodplain
eroding bank behind gabions
High velocity at stream bend
eroding gabion wall toe

12. Stormwater Planning Division
Columbia Road/Randolph Court Stream Restoration
Existing Conditions Along Stream
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Bottom sections of gabion wire
rusted through and losing stone

13. Stormwater Planning Division
Columbia Road/Randolph Court Stream Restoration
Existing Easements
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14. Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Project Constraints
• Complex project design:
– In-stream construction
• Diversion of main tributary around construction site
• Stream construction access
– Gabion replacement requires Building Permit
• County Land Development Services (LDS) structural review
– Other permit requirements:
• US Army Corps of Engineers Permits
• Virginia Stormwater Management Program Permit
• FEMA “no rise”/”no impact” floodplain study
– Gabion Walls
• Currently two failed sections
• More gabion wall sections will fail in the future
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15. Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Indian Run Stream Restoration
• Stream restoration
project proposed
upstream of this
project, from
Indian Run Court to
Columbia Road
• Combine Columbia
Road/Randolph
Court project
design with Indian
Run stream
restoration
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16. Stormwater Planning Division 16

17. Stormwater Planning Division 17

18. Stormwater Planning Division 18
• This project will most
likely be a combination
of Priority 3 and 4
Restoration Approaches
• Limited by Columbia
Road culvert invert

19. Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Stream Restoration Structures- Cross Vane
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20. Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Stream Restoration Structures - Root Wads
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21. Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Stream Restoration Structures - Boulder Toe
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22. Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Stream Restoration - Bank Benches
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23. Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Proposed Resource Protection Area (RPA) Plantings
• RPAs - vegetated riparian
buffer zone:
– Protect water quality
– Filter pollutants out of
stormwater runoff
– Reduce the volume of
stormwater runoff
– Prevent erosion
• Reduce the amount of
mowed grass within RPA
• Sanitary sewer easement
limits types of vegetation
• Plantings provide great
benefits to homeowners
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24. Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Temporary Construction Access
• Maximum allowed slope of
construction access road is
10%
• Project Site Constraints
– Steep slopes
• 4717 Columbia Road = 35%
• 4712 Randolph Court = 25%
– Mature trees
– Existing driveways
• Two feasible temporary
construction access routes
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25. Stormwater Planning Division
Columbia Road/Randolph Court Stream Restoration
Temporary Construction Access - Option 1
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Grade a temporary ramp from 4717
Columbia Road to project site. Ramp
to be removed and site restored
following construction completion.
Construction access with
hardwood matting to protect tree
roots from construction
equipment.
Access stream with temporary
ramp at the low point of gabion
wall
Staging and
Storage Area

26. Stormwater Planning Division
Columbia Road/Randolph Court Stream Restoration
Temporary Construction Access - Option 2
26
Install a temporary construction access
from 4705 Columbia Road to project
site following existing sanitary sewer
easement. Site to be restored
following construction completion.
Construction access with
hardwood matting to protect tree
roots and sanitary sewer from
construction equipment
Access stream with temporary
ramp at the low point of gabion
wall Staging and
Storage Area

27. Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Tentative Schedule
• Initiate Design Task Order (1 month)
• Conceptual Design (5 months)
– Stakeholders Meeting
– County Review
• 95% Design (2 months)
• Final Design (1 month)
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Design Task Order
July 2015
Conceptual Design
Aug 2015 - Jan 2016
Final Design
Mar - Apr 2016
95% Design
Jan - Mar 2016

28. Additional Information
For additional information, please contact
www.fairfaxcounty.gov/dpwes
Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division 28
Catie Torgersen
703-324-5864
Catherine.Torgersen@fairfaxcounty.gov