The project will retrofit two detention basins and restore approximately 1600 feet of stream to reduce erosion and improve habitat.

1. A Fairfax County, VA, publication
Department of Public Works and Environmental Services
Working for You!
Leigh Meadow and Towlston Basin
(0103DP/0584DP)
January 2018

2. Stormwater Planning Division
Agenda
Social Goals
Program Drivers
Environmental Benefits
Project Goals
Existing Conditions
Next steps
Contact information
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3. Stormwater Planning Division
Social Goals
1. Maintain open dialogue and share information.
2. Coordinate with all the stakeholders and the community.
3. Design Team – Stantec Consulting Services, Utilities Design
and Construction Division, Stormwater Planning Division, and
the Community.
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4. Stormwater Planning Division
Stormwater Program Drivers
• Municipal Separate Storm Sewer Permit (MS-4)
• Chesapeake Bay Total Maximum Daily Loads (TMDL)
– Regulates amount of pollutants in waterways
• Other Local TMDLs
• Maintenance of Existing Facilities
• Dam Regulations
• Public Safety /Emergency Response
– Flooding
– Snow Removal
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5. Environmental Benefits
Improve watershed conditions and reduce downstream
impacts through….
Controlling quantity
Controlling velocity
Reduce erosion
Protect infrastructure
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6. Project Area Limits
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0584DP
0103DP
700 feet

7. Stormwater Planning Division
Project Goals
• Retrofit two detention basins (0584DP and 0103DP).
 0584DP - Regenerative Stormwater Conveyance
0103DP – Sand Filter
• Restore up to 1600 feet of stream on Leigh Meadow HOA
and Towlston Meadow HOA properties.
Stabilize streambed and banks
Reduces sediment and nutrient inputs into stream
system
Improve habitat
Maintain close coordination with stakeholders
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8. Stormwater Planning Division
Project Goals
• Safety
• Protect existing infrastructure
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9. Regenerative Stormwater Conveyance
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10. Sand Filter
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Existing
Conditions

12. Stormwater Planning Division
Towlston Meadow Basin Outfall Conditions
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Mowed turf grass does not provide enough root
depth to increase soil resistance to erosion.
24 inch drop about 50 feet downstream of basin.

13. Stormwater Planning Division
Existing Bank Conditions
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April 2015
June 2016

14. Stormwater Planning Division
Existing Bank Conditions
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Existing Bank Conditions
Erosion undermines tree. Tree becomes unstable and leans.
Stormwater Planning Division

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The tree falls down once roots are unable to compensate for the lack of support.
Existing Bank Conditions
Stormwater Planning Division

17. Stormwater Planning Division
Typical Structures Used – Cross Vanes
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Normal Flow Higher flows
Higher flows

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Typical Structures Used –Boulder Clusters

19. Stormwater Planning Division
Typical Structures Used – Root Wads
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20. Stormwater Planning Division 20
Construction
Examples

21. Stormwater Planning Division
Construction
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22. Stormwater Planning Division
Construction
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23. Stormwater Planning Division
Growing Season Following Construction Completion
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24. Stormwater Planning Division
One Year After Construction Completion
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25. Stormwater Planning Division
Three Years After Construction Completion
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Before and After Examples
Stormwater Planning Division
Before One year after construction.
Bridal Path

27. Before and After Examples
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Banks Park
Before One year after construction
Stormwater Planning Division

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Next Steps – Schedule
• Easement acquisition – Completed in October 2017
• Concept design – March 2018
• Revised Concept design – June 2018
• Complete Design – November 2018
• Start Construction – July 2019
• Complete Construction – July 2020

29. Stormwater Planning Division
Contact Information
Contact Information
Design
Fred Wilkins – Project Manager
703-324-5189
Fred.Wilkins@fairfaxcounty.gov
Fairfax County Stormwater Planning Division
703-324-5500 TTY 711
12000 Government Center Parkway
Suite 449
Fairfax, Virginia 22035
www.fairfaxcounty.gov/dpwes/stormwater
To request this information in an alternate format call 703-324-5500, TTY 711
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