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Dead Run Stream Restoration Public Meeting May 19, 2015

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Dead Run Stream Restoration Public Meeting May 19, 2015

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Dead Run Stream Restoration Public Meeting May 19, 2015

  1. 1. A Fairfax County, VA, publication Department of Public Works and Environmental Services Working for You! Dead Run Segment 2/3 Stream Restoration Project Public Meeting McLean Community Center May 19, 2015
  2. 2. Dead Run Segment 2/3 Stream Restoration Project Stormwater Planning Division Meeting Outline 2 • Project Scope and Status • Plan Summary and response to citizen comments • Concept Plan Overview – Basis for design – Tree save options – Floodplain analysis and review of more frequent storm impacts – Buffer restoration measures – Examples • Next Steps • Q and A • Walk to site
  3. 3. Stormwater Planning Division Dead Run Segment 2/3 Stream Restoration Project Project Limits 3 Segment 2 – McLean Central Park • 800 Linear Feet • Completely in Park • Starts below previously restored section near library Segment 3 – Dead Run Stream Valley Park • 1,500 Linear Feet • Extends to Churchill Road • Residential lots along Elizabeth Drive and Carol Rayes Street
  4. 4. Stormwater Planning Division Dead Run Segment 2/3 Stream Restoration Project Project timeline 4 • Project initiated: Fall, 2013 • Surveys and assessment completed: Winter, 2013 • Pre-concepts submitted: April, 2014 • First public meeting – April 23, 2014 • Field walk with FCPA, MTA, Urban Forestry – August 15, 2014 • Pre-concept revisions to minimize tree loss completed: February, 2015 • Second public meeting – February 18, 2015 • Revised concept plan with alternative access options for Segment 3: completed May 12, 2015 • First field walk with community – May 19, 2015 • Second field walk with community – June 9, 2015
  5. 5. Stormwater Planning Division Dead Run Segment 2/3 Stream Restoration Project Overview of Plans 5 • _PG1-27.pdf: Existing and proposed conditions (plan, profile, and cross- sections) - Plan: Bird’s eye view - Profile: Change in elevations along the proposed stream channel centerline - Cross-sections: View of a section taken perpendicular to the channel centerline at a particular location. • _PG28-31a.pdf: Plan view of access with and without aerial photography background – two options for Segment 3 • _PG32-43.pdf: Hydrology (flows) summary, and hydraulics (water surface elevations) of existing and proposed conditions • Excel files: Tree inventory – diameter, condition, removal status
  6. 6. Stormwater Planning Division Dead Run Segment 2/3 Stream Restoration Project Summary of comments received 6 • Need to understand full scope of project: • Access points, how they will be secured, personal liability if county seeks to access our property (_PG28-31a) • Type/Size of equipment that will be used (Do not dictate means and methods, equipment proposed by contractor can be shared by contractor at Pardon Our Dust meeting) • Consideration of alternative modes of accessing creek that could reduce impact on foliage (_PG28-31a – also discussed in detail later) • Duration of project, hours of construction, how long neighborhood will be denied access to pathways (Estimated 6-9 months, Standard work hours are 7am – 5 pm. Loss of access to trails will be minimized to the extent possible)
  7. 7. Stormwater Planning Division Dead Run Segment 2/3 Stream Restoration Project Summary of comments received 7 • Need to understand full scope of project: • Any revision to path of creek (_PG1-27.pdf) • Impact on topography and what type of approach will be used in what parts of creeks (terracing, widening) (_PG1-27.pdf) • Commitment of funding for replacement of lost trees and maintenance by county to ensure trees survive (_PG28-31a) • Aesthetic impact of sediment erosion techniques. (Erosion and Sediment controls are detailed as part of the final plans, all structures proposed to be installed are shown in the plan and profile).
  8. 8. Stormwater Planning Division Dead Run Segment 2/3 Stream Restoration Project Summary of comments received 8 • How flooding concerns will be addressed: • Creek jumps the bank a few times a year and threatens to flood homes • Danger of flash floods in the park, property of nearby residences, and Churchill Road bridge (_PG32-43.pdf, also discussed in detail later) Recurrence Interval Probability 100-year 1% 10-year 10% 2-year 50% 1-year approaches 100%
  9. 9. Stormwater Planning Division Dead Run Segment 2/3 Stream Restoration Project Summary of comments received 9 • How flooding concerns will be addressed (continued):
  10. 10. Stormwater Planning Division Dead Run Segment 2/3 Stream Restoration Project Churchill Road Bridge Flooding 10 • VDOT inspection reports indicate no deficiencies with the bridge. • No current or future project planned for the bridge. • Not subject to frequent closures because of overtopping.
  11. 11. Stormwater Planning Division Dead Run Segment 2/3 Stream Restoration Project Summary of comments received 11 • Loss of tree canopy: • Desire strong measures to maintain and preserve the existing canopy • Anticipated tree impacts shown on plan sheets – 6-12” tree impacts for Segment 3 access options being updated • Tree save efforts discussed in detail later • Proposed buffer restoration measures discussed in detail later
  12. 12. 1 Basis for Design • Stable Channel • Understanding of Floodplain • Address Erosion
  13. 13. 1 Basis for Design • Natural Channel Design (NCD) Approach – reference reach, analytical, regional relationships and hydraulic analysis • Stream pattern, profile and section • Range of values for stable stream pattern • Tree loss is unavoidable but provides opportunity to improve riparian diversity
  14. 14. 1 Basis for Design • Establish Goals: • 1. Improve Flow Conditions in the Channel through Adjustments to Plan/Profile/Section • 2. Create a Stable Channel by Reducing Bed/Bank Erosion that has Benefit of Reducing Contributions of Nitrogen and Phosphorus (i.e. Water Quality Improvement) • 3. Improve Channel Geomorphology and Opportunities for Species Diversity (i.e. Use Structures to Stabilize Channel and Create Pool Habitats) • 4. No-Rise / No-Impact of the Floodplain
  15. 15. 2 Tree Save Efforts 12” and Larger Trees: • ~557 trees 12” and larger assessed • ~43 trees 12” and larger are “at risk” • Species: ~32% tulip tree, ~27% red maple, ~7% green ash 6-12” Trees: • ~214 trees 6-12” assessed • ~28 trees 6-12” are “at risk” • Species: ~23% red maple, ~21% boxelder, ~18% slippery elm, ~11% green ash
  16. 16. 2 Tree Save Efforts • Pre-Concept Plan (Feb. 2014) = ~137 trees 12” and larger removed. This was same plan walked in August 2014. • Concept Plan (Feb. 2015) = ~110 trees 12” and larger removed. Initial alternative access options developed. • Since Feb. 2015 meeting, we’ve modified the channel layout and access options, and located 6 to 12” size trees.
  17. 17. 2 Tree Save Efforts Some of the saved trees
  18. 18. 2 Tree Save Efforts Some of the saved trees
  19. 19. 2 Tree Save Efforts Some of the saved trees
  20. 20. 2 Tree Save Efforts Some of the saved trees
  21. 21. 3 Access Options • Current Plan (May 2015) = ~88 trees 12” and larger proposed for removal, of which ~23 are “at risk”. Up to 10 additional trees could be removed due to access. ~133 trees 6-12” proposed for removal, of which ~28 are “at risk”. Up to 20 additional trees could be removed due to access. • 12” and Larger Trees species most affected: • ~24% tulip tree, ~20% red maple, ~17% green ash • 6-12” Trees most affected: • ~20% red maple, ~27% boxelder, ~20% slippery elm, ~13% green ash • Woody vegetation should not be in the sanitary easement and is subject to removal by Wastewater at any time.
  22. 22. 3 Access Options Segment 2 Tree DEC474 has been removed
  23. 23. 3 Access Options Segment 3 Alternative 1 Removals due to access are primarily on the left bank. ~9 trees (~2 >12” and ~7 6-12” size) Trees DEC91 & DEC301 have been removed
  24. 24. 3 Access Options Segment 3 Alternative 2 Removals due to access are primarily on the right bank. ~21 trees (~7 are >12” and ~14 are 6-12” size) – most are within the sanitary easement
  25. 25. 4 Floodplain Analysis • Studied more frequent storm events 1-, 2-, 10- year flows • Studied less frequent storm events 50-, 100- year flows • No-Rise / No-impact to the floodplain • See pages 32-43 of plan
  26. 26. 4 Floodplain Analysis Pre/Post Comparison – Existing Section 1355 2 year flow out of banks • Existing Conditions Analysis
  27. 27. 4 Floodplain Analysis Pre/Post Comparison – Existing Section 1355 Proposed Channel and Nested Channel
  28. 28. 4 Floodplain Analysis Pre/Post Comparison 100 and 10 year Typical Channel Section
  29. 29. Stormwater Planning Division Dead Run Segment 2/3 Stream Restoration Project Stream Restoration Pictures 29 Government Center Stream Restoration - Before and After
  30. 30. Stormwater Planning Division Dead Run Segment 2/3 Stream Restoration Project Stream Restoration Pictures 30 Poplar Springs, Burke - Before and After
  31. 31. Stream Restoration Stormwater Management Dead Run at Dolley Madison Library 31
  32. 32. Stream Restoration Stormwater Planning Division Dead Run at Dolley Madison Library 32 August 2014 Right January 2010 Below
  33. 33. Dead Run Segment 2/3 Stream Restoration Project Stormwater Planning Division Stream Buffer Restoration Potential 33
  34. 34. Dead Run Segment 2/3 Stream Restoration Project Stormwater Planning Division Chesapeake Bay Preservation Ordinance Resource Protection Area (RPA) 34 http://www.fairfaxcounty.gov/dpwes/environmental/cbay/
  35. 35. Dead Run Segment 2/3 Stream Restoration Project Stormwater Planning Division Stream Buffer Existing Conditions 35
  36. 36. Dead Run Segment 2/3 Stream Restoration Project Stormwater Planning Division Stream Buffer Restoration Potential 36 Segment 3 Stream Buffer Concept
  37. 37. Dead Run Segment 2/3 Stream Restoration Project Stormwater Planning Division Stream Buffer Restoration - Example 37 Typical Planting Area County Staff will coordinate with individual homeowners on plant selection and placement on their properties Buffer Parameters 35’ Minimum from edge of stream bank 50’ Offset optional Plant density determined by Chesapeake Bay Preservation Ordinance Dense planting will provide privacy screening and help mitigate tree loss
  38. 38. Dead Run Segment 2/3 Stream Restoration Project Stormwater Planning Division Stream Buffer Restoration - Example 38 Shrub Layer Typical Shrub Species Spicebush American Elderberry Witch Hazel Winterberry Holly Silky Dogwood Button Bush
  39. 39. Dead Run Segment 2/3 Stream Restoration Project Stormwater Planning Division Stream Buffer Restoration - Example 39 Understory Trees Typical Understory Species Sweetbay Magnolia Eastern Redbud American Hornbeam Hazel Alder Slippery Elm Sassafras
  40. 40. Dead Run Segment 2/3 Stream Restoration Project Stormwater Planning Division Stream Buffer Restoration 40 Canopy Layer Canopy Tree Evergreen Understory Tree Deciduous Understory Tree Shrub Typical Canopy Tree Species Sugar Maple River Birch American Basswood Common Persimmon Swamp White Oak Pin Oak Willow Oak Black Gum
  41. 41. Stormwater Planning Division Dead Run Segment 2/3 Stream Restoration Project Next steps with target dates 41 • Receive concept design comments by June 19th, 2015 • Compile comments, finalize concept plans and publish to website by July 10th, 2015 • Develop 95% design plans, permitting by September, 2015 • Final design phase public meeting, October, 2015 • Final plan authorization and bidding phase – TBD based on funding and approved budget • Target is late spring/early summer, 2016 • Sequence with Dead Run Segment 1 (Dominican Retreat) • Pardon Our Dust meeting with residents and contractor before issuing construction notice to proceed.
  42. 42. Additional Information For additional information, please contact www.fairfaxcounty.gov/dpwes Dead Run Segment 2/3 Stream Restoration Project Stormwater Planning Division 42 Dipmani Kumar 703-324-5500 dkumar@fairfaxcounty.gov

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