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Paul Spring Segment 2 at Hollin Hills Stream Restoration Community Meeting May 2019

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Project managers discuss the site location, project limits and the existing conditions prior to the start of the Paul Spring stream restoration.

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Paul Spring Segment 2 at Hollin Hills Stream Restoration Community Meeting May 2019

  1. 1. A Fairfax County, VA, publication Department of Public Works and Environmental Services Working for You! May 20, 2019 Community Meeting Hollin Meadows Elementary Paul Spring Branch Segment 2 @ Hollin Hills Stream Restoration Project Little Hunting Creek Watershed Plan Implementation
  2. 2. Hollin Hills Stream Restoration DPWES Stormwater Planning Division Program Drivers • 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 System 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 • Maintenance of existing facilities
  3. 3. DPWES Stormwater Planning Division Meeting Outline 3 • Site Location and Project Limits • Existing Conditions • Status and General Schedule • Design Goals • Proposed Alignment and Access • Example Projects • Q&A Hollin Hills Stream Restoration
  4. 4. Little Hunting Creek Watershed • 7,067 acres in Fairfax County • One of the most developed watersheds in Fairfax County • Discharges into Potomac River 4 https://www.fairfaxcounty.gov/dpwes/watersheds/littlehuntingcreek.htm DPWES Stormwater Planning Division
  5. 5. Hollin Hills Stream Restoration DPWES Stormwater Planning Division ~0.04 square miles (23 acres) 5 ~24% impervious
  6. 6. DPWES Stormwater Planning Division Project Limits 6 Hollin Hills Stream Restoration
  7. 7. Hollin Hills Stream Restoration DPWES Stormwater Planning Division Existing Conditions – Incised Channels 7
  8. 8. DPWES Stormwater Planning Division Existing Conditions Eroding Banks 8 Hollin Hills Stream Restoration
  9. 9. DPWES Stormwater Planning Division Existing Conditions Eroding Banks 9 Hollin Hills Stream Restoration
  10. 10. DPWES Stormwater Planning Division Existing Conditions Access to Culvert 10 Hollin Hills Stream Restoration
  11. 11. 11 Existing Conditions Unhealthy Trees DPWES Stormwater Planning Division Hollin Hills Stream Restoration Aging forest threatened by erosion, herbivory and non-native invasive plants.
  12. 12. 12 Existing Infrastructure DPWES Stormwater Planning Division Hollin Hills Stream Restoration Popkins entrance
  13. 13. 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 (Completed) – Preliminary (65%) Design Plan Development (late summer 2019) – Final Design Plan Development (After 65%) – Construction Documents (After final design and permits) 13 Hollin Hills Stream Restoration
  14. 14. DPWES Stormwater Planning Division Status and General Schedule (continued) • Construction (± 12 months) – Construction date dependent on future funding – Bidding and Contract Award – Community Meeting – Construction Begins 14 Hollin Hills Stream Restoration
  15. 15. DPWES Stormwater Planning Division Design Team • Design Team includes: – Members of the Hollin Hills Civic Association – Members of the Hollin Hills community – County staff: Project Manager, Construction Manager, Wastewater, Urban Forester, Stormwater Ecologist – Design Engineers: Stantec – History Commission – Northern Virginia Soil and Water Conservation District 15 Hollin Hills Stream Restoration
  16. 16. Hollin Hills Stream Restoration DPWES Stormwater Planning Division Design Goals 16 What are the design goals? • Stabilize 1,200 LF of 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, park natural resources
  17. 17. Hollin Hills Stream Restoration DPWES Stormwater Planning Division What does 253 lbs of TN look like? 17 This concept estimates saving at least 116 lb/yr TP and 253 lb/yr TN from waterway
  18. 18. Hollin Hills Stream Restoration DPWES Stormwater Planning Division What does 253 lbs of TN look like? 18 • One estimate has it costing $350/lb/yr TN removed (sewage treatment system = $88,550 /yr) • “An analysis from the Chesapeake Bay Foundation, for instance, found that putting the “pollution diet” in place—which is just one piece of the Chesapeake Bay Watershed Agreement—would provide annual benefits worth $129.7 billion: more than 65 times the investments cited in the 2017 Chesapeake Bay Restoration Spending Crosscut.” • One nutrient credit bank (Belle Meade Nutrient Bank) is turning 48.91 acres of hay field into wetland to generate 188.30 lbs of TN credit
  19. 19. Hollin Hills Stream Restoration DPWES Stormwater Planning Division Priority 1 19
  20. 20. DPWES Stormwater Planning Division Hollin Hills Stream Restoration Example In-Stream Structures 20 Reinforced Bed Rock Steps Boulder Riffle
  21. 21. DPWES Stormwater Planning Division Hollin Hills Stream Restoration Stream Bank Reinforcement 21 Native Vegetation In-Stream Log SillToe-Slope Protection
  22. 22. DPWES Stormwater Planning Division Hollin Hills Stream Restoration Construction 22
  23. 23. Hollin Hills Stream Restoration DPWES Stormwater Planning Division Design 23 Upper Middle
  24. 24. Hollin Hills Stream Restoration DPWES Stormwater Planning Division Design 24 Middle Lower
  25. 25. DPWES Stormwater Planning Division Hoolin Hills Stream Restoration Pre-Restoration 25
  26. 26. DPWES Stormwater Planning Division Hollin Hills Stream Restoration Post-restoration 26
  27. 27. Hollin Hills Stream Restoration DPWES Stormwater Planning Division Design – Tree Preservation 27 • Surveyed 238 Trees • This plan would remove 51 trees 12” or greater • Up to 37 of these trees could be reused on site Brush Habitat Large Log Habitat
  28. 28. Hollin Hills Stream Restoration DPWES Stormwater Planning Division 28 Construction Example Pre-Construction 6 months post-Construction
  29. 29. 29DPWES Stormwater Planning Division Hollin Hills Stream Restoration Examples – Quander Road Outfall Pre-Construction 6 months post-Construction 18 months post-Construction
  30. 30. Pre-Construction Construction Post Construction After plant establishmentPost-Construction Hollin Hills Stream Restoration DPWES Stormwater Planning Division Examples – Big Rocky Run Tributary 30
  31. 31. DPWES Stormwater Planning Division Highlights & Next Steps • Stream project requested by the community as erosion is getting worse • Evaluation and design to improve the stream condition and prevent further degradation • Civic Association provided easements to access property • Extensive replanting and non-native invasive control will be incorporated in later design phases • Expecting design completion early in 2020 31 Hollin Hills Stream Restoration
  32. 32. DPWES Stormwater Planning Division Communication • Comments for this plan version due May 28th • Provide them directly to Project Manager (Meghan) • Provide them to community representatives • Refinements of plan sets as we move forward will refine this concept, do not expect major changes • All refinements will be continued to be reviewed by Project Team and regulatory organizations (e.g. History Commission, Army Corps of Engineers) • All refinements will be posted in Sharefile for review • Continue to provide comments and suggestions • Planned Next Community Meeting – just before construction 32 Hollin Hills Stream Restoration
  33. 33. DPWES Stormwater Planning Division Contact Information Design Meghan Fellows – Project Manager 703-324-5807 Meghan.Fellows@fairfaxcounty.gov Fairfax County Stormwater Planning Division Department of Public Works and Environmental Services (DPWES) 12000 Government Center Parkway Suite 449 Fairfax, Virginia 22035 www.fairfaxcounty.gov/publicworks/stormwater To request this information in an alternate format call 703-324-5500, TTY 711 Presentation Website 33

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