A section of Crook Branch will be restored to accomplish the following 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

1. A Fairfax County, VA, publication
Department of Public Works and Environmental Services
Working for You!
December 5, 2018
Community Meeting
Mantua Elementary School Cafeteria
Crook Branch at Mantua Elementary School Stream
Restoration Project
Accotink Creek Watershed Plan Implementation

2. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Meeting Outline
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• Status and General Schedule
• Site Location and Project Limits
• Existing Conditions
• Design Goals
• Proposed Alignment and Access
• Projected Tree and Trail Impacts
• Native Vegetation
• Mantua Elementary School Chamber System
• Q&A

3. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Status and General Schedule
• Data Collection (Completed)
• Stream Restoration Design Process (In Progress)
– Pre-Concept Plan Development (Completed)
– Concept (35%) Design Plan Development (Completed)
– Field Walk – August 2017 (Completed)
– Preliminary (65%) Design Plan Development Completed)
– Final Design Plan Development (In Progress)
– Construction Documents
• Construction (± 12 months)
– Bidding and Contract Award
– Pardon Our Dust Community Meeting
– Construction date dependent on future funding
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4. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Project Limits
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5. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Existing Easements
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Conservation
Easement
Storm Drainage
and Floodplain
Easement
Floodplain
Easement
Storm Drainage
Easement
Additional
Floodplain
Easement
has been
obtained

6. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Crook Branch: Drainage Area
• Drainage Area:
– 827.8 acres
• Imperviousness:
– 35% = URBAN
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7. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Crook Branch: Existing Conditions
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8. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Crook Branch: Existing Conditions
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9. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Crook Branch: Existing Conditions
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10. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Crook Branch: Existing Conditions
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11. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Crook Branch: Existing Conditions
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12. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Crook Branch: Existing Conditions Downstream
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13. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Crook Branch: Existing Conditions Downstream
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14. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
DESIGN GOALS
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What are the design goals?
• 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
• Additional Project Specific Goals
• Protect valuable infrastructure
• Sanitary Lines
• Water Lines
• Bridge and trail

15. DPWES Stormwater Planning Division
Crook Branch Stream Restoration
Stream Structures and Bed Reinforcement
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Reinforced Bed
Step Pools Cross Vanes

16. DPWES Stormwater Planning Division
Crook Branch Stream Restoration
Stream Reinforcement – Using Wood
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Toe Wood
Type I Woody Debris
Native Vegetation
In-Stream Habitat Log Sill

17. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Design – Proposed Alignment and Access
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18. DPWES Stormwater Planning Division
Crook Branch Stream Restoration
Design – Proposed Cross Section Reach 1
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Section 1

19. DPWES Stormwater Planning Division
Crook Branch Stream Restoration
Design – Proposed Cross Section Reach 2
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Section 2

20. DPWES Stormwater Planning Division
Crook Branch Stream Restoration
Design – Proposed Cross Section Reach 3
20Section 3

21. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Design – Proposed Bridge Realignment
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• Existing bridge will
be removed
• New 40’ span bridge
will be installed

22. Crook Branch Stream Restoration
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

23. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Design – Tree Impacts
23

24. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Design – Floodplain Impacts
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25. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Design – Floodplain Impacts
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26. Crook Branch Stream Restoration
DPWES Stormwater Planning Division 26
Post Construction Example

27. Crook Branch Stream Restoration
DPWES Stormwater Planning Division 27
Growing Season Following Construction Completion

28. Crook Branch Stream Restoration
DPWES Stormwater Planning Division 28
One Year After Construction Completion

29. Crook Branch Stream Restoration
DPWES Stormwater Planning Division 29
Three Years After Construction Completion

30. Pre-Construction Construction
Post Construction After plant establishmentPost-Construction
Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Examples – Big Rocky Run Tributary
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31. Pre-Construction
After plant establishment
Post-Construction
Crook Branch Stream Restoration
Examples – Turkey Run @ Truro
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32. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Strategies for Successful 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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33. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Reduce the Competition
• Non-Native Invasive Plant Management
• Pre-treatment of vines, shrubs, bamboo, trees
• Within Limit of Disturbance
• Physical removal and chemical control
• Buffer Zone At least 25’ from LOD
• Work with you to set boundaries
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34. Additional Information
For additional information, please contact
www.fairfaxcounty.gov/publicworks
Crook Branch Stream Restoration
DPWES Stormwater Planning Division 34
Vivian Bui, Project Manager
Matt Meyers, Branch Chief
Watershed Projects implementation Branch - North
703-324-5500
Vivian.Bui@fairfaxcounty.gov
Matthew.Meyers@fairfaxcounty.gov
703-324-5500, TTY 711
www.fairfaxcounty.gov/publicworks/stormwater

35. DPWES Stormwater Planning Division
Mantua Elementary Chamber System
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Before

36. DPWES Stormwater Planning Division
Mantua Elementary Chamber System
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During Construction

37. DPWES Stormwater Planning Division
Mantua Elementary Chamber System
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During Construction

38. DPWES Stormwater Planning Division
Mantua Elementary Chamber System
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After

39. DPWES Stormwater Planning Division
Mantua Elementary Chamber System
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