The Rocky Run Tributary at Hickory Hollow Lane project goals are to stabilize the stream, reduce excess sediment from flowing downstream; improve aesthetics, reduce hazards, reconnect the stream to the floodplain, improve the riparian buffer and reduce road flooding, among other goals.

1. A Fairfax County, VA, publication
Department of Public Works and Environmental Services
Working for You!
January 2021
Virtual Community Meeting
Rocky Run Tributary @ Hickory Hollow Lane
Stream Restoration Project
Difficult Run Watershed Plan Implementation

2. DPWES Stormwater Planning Division
Meeting Outline
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• Fairfax County Stormwater Management
• Program drivers
• Watershed management plan implementation
• Project Introduction and Objectives
• Existing Conditions
• Restoration Approaches
• Example Projects
• Proposed Improvements
• Exiting/proposed alignment
• Access
• Tree Impacts
• Floodplain
• Easements
• Status and schedule
• Questions?

3. DPWES Stormwater Planning Division
Program Drivers
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• Municipal Separate Storm Sewer Permit (MS-4)
– Easements rights and responsibility to maintain/upgrade
• Chesapeake Bay Agreement
– Partnering states (VA, MD, DC, DE, PA, WV) signed the
agreement to restore the bay health and ecosystem
• Total Maximum Daily Loads (TMDL) = Local Stream Health
– Regulates amount of pollutants in waterways
• Dam Safety Regulations
• Public Safety/Emergency Response
• Maintenance of Existing Stormwater Infrastructure

4. DPWES Stormwater Planning Division
Implementation Strategies
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Watershed Management Plan (Fairfax County - 400 Sq. Mi.):
 Developed for 30 watersheds
 Priority areas for retrofits/restoration
For details: https://www.fairfaxcounty.gov/publicworks/stormwater/difficult-run-watershed
Rocky Branch is part of Difficult Run
Watershed management plan
Difficult Run Watershed

5. DPWES Stormwater Planning Division
Proposed Project
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Begin
End

6. DPWES Stormwater Planning Division
Project: Drainage Area
• Drainage Area: 773.2 acres
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• Imperviousness: 25.3% = URBAN

7. DPWES Stormwater Planning Division
Proposed Project – current conditions
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 Incised channel
 Eroded bed and banks
 Unstable slopes
 Exposed Utilities
 Frequently Flooded Culvert

8. DPWES Stormwater Planning Division
Existing Conditions
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Unprotected vertical bank 8’-10’ on the mainstem

9. DPWES Stormwater Planning Division
Existing Conditions
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Vertical blown-up banks downstream of Ashlawn Park near Nadine Drive

10. DPWES Stormwater Planning Division
Existing Conditions
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Exposed sanitary crossing in the main channel

11. DPWES Stormwater Planning Division
Existing Conditions
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Actively eroding bank downstream of Hickory Hollow Lane

12. DPWES Stormwater Planning Division
Existing Conditions
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Eroded downstream section of culvert crossing on Hickory Hollow Lane

13. DPWES Stormwater Planning Division
Project Design Goals
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Restore ~3,430 feet of main channel and ~ 1,740 feet of tributaries
• General Goals
• Stabilize stream
• Reduce excess sediment from being transported downstream
• Reduce excess nutrients from entering the waterway
• Improve aesthetics
• Reduce hazards (steep, eroding banks)
• Reconnect stream to floodplain
• Improve Riparian Buffers
• Reduce road flooding
• Additional Project Specific Goals
• Protect valuable infrastructure
• Sanitary Lines and others
• Hickory Hollow Road crossing
• Protect properties
• Better access to stream corridor, softer grades to reach to stream

14. DPWES Stormwater Planning Division
Restoration Approaches
Priority 1 Restoration – Raise stream to reconnect with floodplain.
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Fewer trees removed
Width of disturbance
Balanced cut and fill volumes
result in less waste
Before After

15. DPWES Stormwater Planning Division
Restoration Approaches
Priority 2 Restoration – Excavate floodplain at lower elevation.
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Width of disturbance
Large cut volumes result in waste material
Many trees removed
Priority 3 Restoration –
Confined stream valleys.

16. DPWES Stormwater Planning Division
Restoration Approaches
Priority 4 Restoration – Stabilize in-place.
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17. DPWES Stormwater Planning Division
Restoration approaches: Design element
Stream Structures and Bed Reinforcement
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Reinforced Bed
Step Pools Cross Vanes

18. DPWES Stormwater Planning Division
Restoration approaches: Design element
Stream Reinforcement – Using Wood
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Toe Wood
Type I Woody Debris
Native Vegetation
In-Stream Habitat Log Sill

19. DPWES Stormwater Planning Division
Example Projects: Government Center Stream Restoration Before & After
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20. DPWES Stormwater Planning Division
Example Projects: Poplar Springs, Burke Before & After
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21. DPWES Stormwater Planning Division
Summary of Concept Design - Alignment
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Existing stream
alignment
Proposed stream
alignment
Limit of
Disturbance

22. DPWES Stormwater Planning Division
Summary of Concept Design- Construction Access
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Staging Area
Access Path
Entry point
Entry point
Entry
points

23. DPWES Stormwater Planning Division
Design - Tree Impacts
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Tree impact considerations
Ecological / Habitat Value
• Size / Diameter
• Higher - Climax species: Oaks, Hickory, Holly (mast
producers, long-lived).
• Lower – Early successional species: Maples, Poplar
(fast-growing, short-lived).
Existing Condition
• Undercut by stream, high proportion of exposed
roots, short life expectancy
• Dead, dying, diseased or damaged trees that pose a human safety hazard
• Impacting or pending impact to infrastructure (utilities, roads, trails, etc.)
Proposed Condition
• Long-living, healthy, native species that help to stabilize the banks and floodplain
• Increased bio-diversity
Most of the trees in project areas
rated as fair/poor health conditions

24. DPWES Stormwater Planning Division
Tree Removal and Preservation
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• Trees to be removed considers those which are
already in danger of falling due to erosion
• It also considers preserving trees which are good
value and have potential for longer survivability

25. DPWES Stormwater Planning Division
Summary of Concept Design -100 Year Floodplain
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Proposed floodplain Limit
Existing floodplain limit

26. DPWES Stormwater Planning Division
Summary of Concept Design -100 Year Floodplain
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Proposed floodplain Limit
Existing floodplain limit

27. DPWES Stormwater Planning Division
Existing Easements/Easement Requirements
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Floodplain
Easement
Storm Drainage
Easement
Floodplain &
Storm Drainage
Easement
Proposed
Floodplain &
Storm Drainage
Easement

28. DPWES Stormwater Planning Division
Design – Proposed Cross Section Rendering
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29. DPWES Stormwater Planning Division
Design – Wetland Area and proposed section rendering
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30. DPWES Stormwater Planning Division 30
Post Construction Example

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Growing Season Following Construction Completion

32. DPWES Stormwater Planning Division 32
One Year After Construction Completion

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Three Years After Construction Completion

34. DPWES Stormwater Planning Division
Strategies for Successful Restoration & Revegetation
• Stream Restoration Design Goals
– Structural:
• Including grading and rock structures
– AND Biological:
• Soils and Plants support
• Insects, Reptiles, Birds and Mammals
• Pre-Construction
– Non-Native Invasive Plant Management
• Establish clear zone so that natives can re-establish
– Native plant rescues
• Final Phase of Construction
– Stabilize with native seed
– Plant native shrubs and trees
– Minimum 1-year warranty
• Minimum 3-year monitoring
– For Native Vegetative Cover
– Less than 20% Invasive
– Zero % Highly Invasive
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35. DPWES Stormwater Planning Division
Status and General Schedule
• Concept Plan Review (in progress)
• Value Engineering Study (In Progress)
– Required when construction value exceeds $2 million
• Preliminary design: April 2021
• Final design completion: Winter 2022
• Construction (± 18 months)
– Bidding and Contract Award
– Pardon Our Dust Community Meeting
– Construction date dependent on future funding
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36. Additional Information
For additional information, please contact
DPWES Stormwater Planning Division 36
Sajan Pokharel, Project Manager
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