The project will stabilize the stream, reduce water pollution and hazards, prevent flooding, and protect infrastructure.

1. A Fairfax County, VA, publication
Department of Public Works and Environmental Services
Working for You!
April 25, 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
2
• Status and General Schedule
• Site Location and Project Limits
• Discuss General Design Approach
• Review Historical Data
• 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 (In Progress)
– Final Design Plan Development – Fall 2018
– 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: Historical Aerials
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7. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Crook Branch: Historical Aerials
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8. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Crook Branch: Historical Aerials
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9. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Crook Branch: Drainage Area
• Drainage Area:
– 827.8 acres
• Imperviousness:
– 35% = URBAN
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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
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13. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Crook Branch: Existing Conditions
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14. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Crook Branch: Existing Conditions
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15. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Crook Branch: Existing Conditions Downstream
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16. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Crook Branch: Existing Conditions Downstream
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17. 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

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

19. 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

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

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

23. DPWES Stormwater Planning Division
Crook Branch Stream Restoration
Design – Proposed Cross Section Reach 3
23Section 3

24. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Design – Proposed Bridge Realignment
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25. 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

26. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Design – Tree Impacts
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27. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Design – Floodplain Impacts
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28. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Design – Floodplain Impacts
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29. Crook Branch Stream Restoration
DPWES Stormwater Planning Division 29
Post Construction Example

30. Crook Branch Stream Restoration
DPWES Stormwater Planning Division 30
Growing Season Following Construction Completion

31. Crook Branch Stream Restoration
DPWES Stormwater Planning Division 31
One Year After Construction Completion

32. Crook Branch Stream Restoration
DPWES Stormwater Planning Division 32
Three Years After Construction Completion

33. 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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34. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Examples – Rabbit Branch
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Pre-Construction Construction
Post-Construction 8 Months After Construction

35. 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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36. 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
• Establish clear zone so natives plants can re-establish
• Minimize/eliminate non-natives in adjacent yards -
volunteer
• Maintain clear zones adjacent to stream on private
property - volunteer
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37. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Tips for Planting on Private Property
37
• Plant for Native Wildlife not Urban Invaders
• Native Oak trees support over 500 native species of insects, birds, amphibians
• Bradford pear supports less than 10 species
• English Ivy harbors rats and Asian tiger mosquitos – replace with Sedges,
Golden groundsel, Christmas fern
• Common violet supports the early spring Fritillaria butterfly
• Increase plant layers in plant beds
• Maintain natural leaf litter
• Reduce lawn areas and use a mulching mower
• Reduce use of chemical pesticides - Tip and Toss to control mosquitos

38. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Managing Rainwater on Private Property
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• Reduce Stormwater Run-off at the Source
• Increase canopy from trees, shrubs and groundcover
• Forested areas intercept 90% more rainfall than lawns
• Plant trees and multiple layers of plants
• Reduce fertilization
• Detain rainfall on site
• Dis-connect downspouts
• Install rain barrels
• Rain gardens
• Pervious paving

39. Crook Branch Stream Restoration
DPWES Stormwater Planning Division
Resources for Gardening for Wildlife
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Guidance and Grants:
Northern Virginia Soil and Water Conservation District
• https://www.fairfaxcounty.gov/soil-water-conservation/
Native Plant Resources & What Not to Plant:
Plant NOVA Natives – plant descriptions and where to buy
• https://www.plantnovanatives.org/
Audubon at Home – site visits from Virginia Master Naturalists or Master Gardeners
• http://audubonva.org/audubon-at-home-1
Virginia Native Plant Society - Potowmack Chapter at Greenspring Gardens – displays, lectures
• http://vnps.org/potowmack/
DCR List of Non-Native Invasive Plants – over 90 species currently
• http://www.dcr.virginia.gov/natural-heritage/document/nh-invasive-plant-list-2014.pdf
Fairfax County Stewardship – Invasive Forest Plants
• https://www.fairfaxcounty.gov/parks/sites/parks/files/assets/documents/naturalcultural/invasive%20forest
%20plants%20brochure.pdf

40. DPWES Stormwater Planning Division
Mantua Elementary Chamber System
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Before

41. DPWES Stormwater Planning Division
Mantua Elementary Chamber System
41
During Construction

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

43. DPWES Stormwater Planning Division
Mantua Elementary Chamber System
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After

44. DPWES Stormwater Planning Division
Mantua Elementary Chamber System
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45. Additional Information
For additional information, please contact
Crook Branch Stream Restoration
DPWES Stormwater Planning Division 45
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