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Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
Huntsman Lake Dam Rehabilitation Project
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Huntsman Lake Dam Rehabilitation Project

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Huntsman Lake Dam Rehabilitation Project …

Huntsman Lake Dam Rehabilitation Project

Huntsman Lake Dredging and Restoration

Department of Public Works and Environmental Servcies

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  • 1. Huntsman Lake Dam Rehabilitation Huntsman Lake Dredging and RestorationDepartment of Public Works and Environmental Services  Fairfax County, VA   A Fairfax County, VA publication September 2012
  • 2. Huntsman Lake Dam Rehabilitation Huntsman Lake Dredging and Restoration  Outline• Dam Rehabilitation  – Background – Major design elements – Easements – Mitigation for tree and wetland loss• Lake Dredging and Restoration – Sedimentation  – Dredging options and approach – Lake restoration• Timeline for Projects and Coordination 
  • 3. Huntsman Lake Dam Rehabilitation Project  Background• Huntsman Lake Dam is a 41.5 feet high earth‐fill dam built in 1973 as flood‐control  dam by the Natural Resources Conservation Service (NRCS). Fairfax County and the  Northern Virginia Soil and Water Conservation District (NVSWCD) were the local  sponsors.• It was the second of six dams built by the NRCS in the Pohick Creek watershed
  • 4. Huntsman Lake Dam Rehabilitation Project  Background• The dam drains an area of 1,482 acres (2.3 square miles)• Land‐use in the drainage area is 73 percent residential and 22 percent  woodland or open space 
  • 5. Huntsman Lake Dam Rehabilitation Project  Background• The dam impounds a 28.6 acre lake at normal pool, with a floodwater  retarding pool area of 60 acres• Huntsman Lake Dam is regulated by the Virginia Department of Conservation  and Recreation (DCR), Division of Dam Safety
  • 6. Huntsman Lake Dam Rehabilitation Project  Background• Huntsman Dam operates under a conditional Operation & Maintenance  (O&M) Certificate from DCR because its auxiliary spillway can only convey  about 50 percent of the flows from the design storm. 
  • 7. Huntsman Lake Dam Rehabilitation Project  Background• In 2010, NRCS in collaboration with Fairfax County and NVSWCD initiated a rehabilitation  project for the Huntsman Lake dam• Fairfax County contracted with Schnabel Engineering to provide engineering and ancillary  services for the project• A local task force was formed to provide input on community concerns, and a number of  task force meetings and public meetings were held in 2010 and 2011• A rehabilitation plan was developed by NRCS collaboratively with Fairfax County and  NVSWCD and released in September 2011• Design work by Schnabel Engineering was initiated shortly after the release of the  rehabilitation plan, and a final design submitted in August, 2012
  • 8. Huntsman Lake Dam Rehabilitation Project  Summary of rehabilitation plan
  • 9. Huntsman Lake Dam Rehabilitation Project  Major Design Elements
  • 10. Huntsman Lake Dam Rehabilitation Project  riser replacement
  • 11. Huntsman Lake Dam Rehabilitation Project  riser replacement 
  • 12. Huntsman Lake Dam Rehabilitation Project  spillway realignment and armoring
  • 13. Huntsman Lake Dam Rehabilitation Project  spillway realignment and armoring
  • 14. Huntsman Lake Dam Rehabilitation Project  spillway realignment and armoring
  • 15. Huntsman Lake Dam Rehabilitation Project  EasementsA public hearing for the required easement on Lakewood Hills  Community Association #1 property is planned for December 4, 2012
  • 16. Huntsman Lake Dam Rehabilitation Project  mitigation for tree and wetland loss
  • 17. Huntsman Lake Dam Rehabilitation Project  Summary• In 2010, NRCS in collaboration with Fairfax County and NVSWCD  initiated a rehabilitation project for the Huntsman Lake dam• Final design for the project has been completed by Schnabel  Engineering and is awaiting approval by NRCS and Fairfax County• Permit applications have been prepared for the project and will  be submitted shortly• A public hearing for an easement required on Lakewood Hills #1  Homeowners Association property is proposed for December 4th,  2012• Mitigation for tree and wetland loss as a result of the project is  proposed on the lake shoreline and on Middle Run upstream of  Huntsman Boulevard
  • 18. Huntsman Lake Dredging and Lake Restoration  Background
  • 19. Huntsman Lake Facts• Drainage Area = 1,482 acres (2.3 square miles)• Lake Surface Area = 28.6 acres• Sediment Pool Capacity = 295,000 cubic yards (CY)• Current sediment in lake = 65,000 CY• Estimated annual sediment load = 2,970 CY 32.5 feet 65,000 CY
  • 20. Sediment Thickness
  • 21. Water Depth
  • 22. Inactive Dewatering Basin 2011
  • 23. Lake Restoration and Dredging ProjectProject Goals• Restore sediment pool capacity – Downstream water quality benefits – Lake water quality – Esthetics• Improve lake water quality and habitat• Provide long term maintenance improvements
  • 24. Dredging Alternatives1. Mechanically dredge and haul wet2. Drain lake and dry in place before hauling3. Hydraulically dredge and dewater on shore in Geo- textile bags
  • 25. Lake Barton ExamplePRE‐DREDGING: An estimated 35,000 cubic yards of sediment accumulated in the lake forming islands and reducing water levels to less than three feet in most areas.
  • 26. Lake Barton: Pre-Dredging
  • 27. Lake Barton: Dredging in Progress
  • 28. Lake Barton: Dredging in progress
  • 29. Lake Barton: Dredging in progress
  • 30. Lake Barton: Completed Project
  • 31. Option to Drain LakeLake Needwood in Montgomery County, MD 
  • 32. Option to Drain Lake
  • 33. Option to Drain LakeLake Needwood in Montgomery County, MD  33
  • 34. Huntsman LakePhase 1 Dredging 30,000 Cubic Yards
  • 35. Huntsman LakePhase 2 Dredging up to an additional 35,000 Cubic Yards
  • 36. Lake Restoration• In‐lake forebay• Wetland planting• Shoreline stabilization• Fish habitat• Fish stocking Lake Barton: Fish stocking by Virginia Game and Inland Fisheries Fish habitat created from salvaged trees
  • 37. Shoreline Restoration
  • 38. Shoreline RestorationHuntsman Lake Existing Conditions
  • 39. Shoreline Protection  Options
  • 40. Fish Habitat Structures
  • 41. Huntsman LakeSite Access and Staging Area
  • 42. Huntsman Lake 2011
  • 43. Huntsman Lake Dam Rehabilitation Huntsman Lake Dredging and Restoration Project timeline and coordination • Project agreement between Fairfax County, NVSWCD and NRCS  (for dam rehabilitation) expected to be executed by  February/March, 2013• Project bidding and contract award: approximately 2‐3 months• Project duration: 8‐9 months• Lake will remain drained for entire project• Drawdown will be controlled to allow fish to migrate downstream  to the greatest extent possible• Dam rehabilitation and dredging projects will be coordinated to  minimize the time lake is drained• Lake filling after project completion is dependent  on rainfall  conditions
  • 44. Huntsman Lake Dam Rehabilitation Huntsman Lake Dredging and Restoration  For more information or to request this information in an alternate format, call the Stormwater Planning Division, Department of Public  Works and Environmental Services, Fairfax County 703‐324‐5500  TTY 711 or email SWPDmail@fairfaxcounty.gov

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