This document provides information about a proposed stream restoration project along Difficult Run in Fairfax County, VA. The project aims to restore about 3000 feet of the main channel and 1500 feet of tributaries to stabilize the streambed and banks, reduce sediment and nutrient inputs, and improve habitat. The document discusses the existing poor conditions of erosion and instability. It also outlines the proposed restoration approaches, including designs for cross sections, alignments, structures, grading plans and profiles. Timeline details are provided, with construction dependent on future funding. The overall goal is to improve watershed conditions and reduce downstream impacts.

1. A Fairfax County, VA, publication
Department of Public Works and Environmental Services
Working for You!
Difficult Run Tributary @ Brittenford Drive
Stream Restoration Project
Hunter Mill District
May 2017
INFORMATION MEETING
Concept Plan

2. Stormwater Planning Division
Agenda
Why?
• Social Goals
• Program Drivers
• Environmental Benefits
• Watershed - Watershed Assessment and Characterization
How?
• Project Implementation Strategies
• Stream Restoration
• Approaches
• Examples
• Design Development
When?
• Timeline/Next Steps
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3. Stormwater Planning Division
Social Goals
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1. Maintain open dialog and share information.
2. Coordinate with all the stakeholders and the community.
3. Build partnerships with local organizations such as
Homeowners Associations.
4. Design Team – Wetland Studies and Solutions, Stormwater
Planning Division, Urban Forest Management Division, Park
Authority, and Utilities Design and Construction Division.

4. Stormwater Planning Division
Program Drivers
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• State and Federal Regulations
 Chesapeake Bay Agreement
Partnering states (VA, MD, DC, DE, PA, WV) signed the agreement to
restore the bay health and ecosystem.
 Municipal Separate Storm Sewer Permit (MS-4)
Easements rights and responsibility to maintain/upgrade
 Local TMDLs (Total Maximum Daily Loads – sediment, bacteria, PCBs)
Regulates amounts of pollutants in waterways
• Public Safety
 Erosion control
 Flooding
 Snow removal
• Maintenance of existing facilities
• Dam Regulations

5. Stormwater Planning Division
Environmental Benefits
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Improve watershed conditions and reduce downstream
impacts through….
Controlling quantity
Mitigate flooding where possible
Controlling velocity
Reduce erosion
Protect infrastructure and properties (private and public)

6. Stormwater Planning Division
Watersheds/Drainage Areas
Difficult Run > The Potomac River > The Chesapeake Bay…
• ~ 58 square miles
• ~ 145 miles of stream
Difficult Run Stream Assessment
 Physical Assessment: 130 Miles (conducted in 2002)
 Results:
 Poor condition with severely incised stream and
significant portion with unstable banks – 88%
channels
 Most of watershed’s tributaries in widening stage
 Habitat Assessment:
Results: ~ 1% excellent, ~16% Good, ~48% Fair,
~34% Poor, ~1% Very poor
 DEQ listed portions of the Difficult Run Watershed as impaired
waters (impairments: pathogens, benthic)
 TMDLs: E. Coli, Sediment
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Difficult Run Watershed:
Watershed Characteristics/Stream Assessment
For details: http://www.fairfaxcounty.gov/dpwes/watersheds/difficultrun.htm

7. Stormwater Planning Division
Project Implementation Strategies
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Implementation Strategies (Fairfax County - 400 Sq. Mi.):
 Watershed Management Plan
 Developed for 30 watersheds
 Priority areas for retrofits/restoration – project are selected based
on the plan
 Ongoing Maintenance Issues
 Downstream dry pond 1473DP
 Immediate safety and severe erosion issues

8. Stormwater Planning Division
Current Condition:
- Incised channel
- Eroded bed and
banks
- Unstable slopes
- Exposed Utilities
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Proposed Project
Project Goals:
Restore ~3000 feet of main channel and ~ 1500 feet of tributaries
 Stabilize streambed and banks
 Reduces sediment and nutrient inputs into stream system
 Improve habitat
 Protect Infrastructure (properties, utilities, etc.)

9. Stormwater Planning Division
Existing conditions
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10. Stormwater Planning Division
Existing conditions (cont’d)
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11. Stormwater Planning Division
Existing conditions (cont’d)
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12. Stormwater Planning Division 12
Restoration Approaches

13. Stormwater Planning Division 13
Restoration Approaches (contd.)

14. Stormwater Planning Division 14
Restoration Approaches (contd.)

15. Stormwater Planning Division 15
Restoration Approaches (contd.)

16. Stormwater Planning Division 16
Restoration Approaches Design Elements –Typical Structures

17. Stormwater Planning Division 17
Videos of Typical Structures Used

18. Stormwater Planning Division
Construction Example
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19. Stormwater Planning Division
Post Construction Example
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Immediate After Construction Growing Season Following Construction
Completion

20. Stormwater Planning Division
Post Construction
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One Year After Construction Three Years After Construction

21. Stormwater Planning Division
Example Projects: Government Center Stream Restoration Before & After
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Before After

22. Stormwater Planning Division
Example Projects: Poplar Springs, Burke Before & After
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Before After

23. Stormwater Planning Division
Example Projects: Rabbit Branch Before & After
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Before After

24. Stormwater Planning Division
Existing Conditions
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Reach Existing Length [ft]
Main Channel 3637
Tributary 1 194
Tributary 2 271
Tributary 3 443
Tributary 4 452
Tributary 5 44
Tributary 6 472
Tributary 7 659
Total 6171
Existing Channel Details:
• Main channel + 7 tributaries, 6171 ft total
• Drainage area = 459 acres = 0.72 mi2
• 7 sanitary sewer crossings

25. Stormwater Planning Division
Design – Proposed Cross Sections
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Reach 1:
WBKF = 19.0 ft
DMAX-BKF = 2.0 ft
ABKF = 24.3 ft2
Reach 2:
WBKF = 22.0 ft
DMAX-BKF = 2.3 ft
ABKF = 32.7 ft2

26. Stormwater Planning Division
Design – Proposed Alignment
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Reach Existing Length [ft] Restored Length [ft]
Main Channel 3637 2839
Tributary 1 194 40
Tributary 2 271 121
Tributary 3 443 364
Tributary 4 452 464
Tributary 5 44 47
Tributary 6 472 249
Tributary 7 659 502
Total 6171 4626

27. Stormwater Planning Division
Design – Proposed Access
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28. Stormwater Planning Division
Design – Grading Plan and Profile
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29. Stormwater Planning Division
Upstream Culvert
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30. Stormwater Planning Division
Design – Grading Plan and Profile
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31. Stormwater Planning Division
Design – Sanitary Crossing
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32. Stormwater Planning Division
Design – Grading Plan and Profile
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33. Stormwater Planning Division
Design – Grading Plan and Profile
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34. Stormwater Planning Division
Design – Grading Plan and Profile
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35. Stormwater Planning Division
Design – Grading Plan and Profile
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36. Stormwater Planning Division
Design – Sanitary Crossing
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37. Stormwater Planning Division
Design – Grading Plan and Profile
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38. Design – Sanitary Crossing
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39. Design – Sanitary Crossing
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40. Stormwater Planning Division
Design – Grading Plan and Profile
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41. Stormwater Planning Division
Design – Sanitary Crossing
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42. Stormwater Planning Division
Design – Grading Plan and Profile
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43. Stormwater Planning Division
Downstream Pond
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44. Stormwater Planning Division
Design – Grading Plan and Profile
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45. Stormwater Planning Division
Tributary 1 Trail Crossing
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46. Stormwater Planning Division
Design – Grading Plan and Profile
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47. Stormwater Planning Division
Design – Sanitary Crossing
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48. Stormwater Planning Division 48

49. Stormwater Planning Division
Design – Grading Plan and Profile
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50. Stormwater Planning Division
Design – Grading Plan and Profile
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51. Stormwater Planning Division
Design – Grading Plan and Profile
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52. Stormwater Planning Division
Tributary 6 Trail Crossing
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53. Stormwater Planning Division
Design – Grading Plan and Profile
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54. Stormwater Planning Division
Tributary 7 – Exposed Utilities and Pipe
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55. Stormwater Planning Division
Design – Grading Plan and Profile
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56. Stormwater Planning Division
Tributary 7 Trail Crossing
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57. Stormwater Planning Division
Tree Inventory
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58. Stormwater Planning Division
Forest Edge Restoration
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59. Stormwater Planning Division
Forest Edge Restoration
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60. Stormwater Planning Division
Timeline and next steps
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• Survey & Data Collection - October, 2016
• Hydrology Assessment & Layout Sketch - December, 2016
– Pre-design meeting
• Conceptual design - March, 2017
• Concept revision - June, 2017
• Design Completion - December, 2017
• Construction - Dependent on future funding

61. Additional Information
For additional information, please contact
Stormwater Planning Division 61
Sajan Pokharel
703-324-5687
Email: Sajan.Pokharel@fairfaxcounty.gov
To request this document in an alternate format, call 703-324-
5500, TTY 711, or email SWPDmail@fairfaxcounty.gov
www.fairfaxcounty.gov/publicworks/stormwater