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Royal Lake Dredging and Restoration
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Royal Lake Dredging and Restoration


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Royal Lake Dredging and Restoration …

Royal Lake Dredging and Restoration

Fairfax County Department of Public Works and Environmental Services

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  • 1.  Dredging Program and Project Background Project Benefits Royal Lake Conditions Phased Approach Dredging Methods and Alternatives Park Access and Community Coordination Next StepsRoyal Lake: Meeting Agenda
  • 2.  History– Lakes previously dredged by DPWES Stormwater– Limited to small quantities– Dewatered on site Lake Barton completed in 2011 Currently working on:– Huntsman Lake, Woodglen Lake, Royal LakeDredging and Lake Restoration Program
  • 3.  Completed Data Collection Developing Lake Dredging and Management Plan Community coordination at design and constructionphases– Preliminary Design (65%)– Final Design (95%)– Preconstruction: Pardon Our Dust meeting December 2013: Final Design Construction in Fiscal Year 2015 (July 2014)Royal Lake Dredging and RestorationProject Timeline and Coordination
  • 4.  Restore sediment pool capacity– Downstream water quality benefits– Lake water quality– Aesthetics Improve lake water quality and habitat Provide long term maintenance improvementsProject Goals and Benefit
  • 5. Lake Barton Dredging and RestorationArea Treated(acres)Phosphorous Removal Nitrogen Removal Sediment Removal544 77,000 lbs dredged 115,500 lbs dredged 38,500 tons dredgedAnnual benefit fromincreased trappingefficiency130 lbs/year 200 lbs/year 65 tons/year
  • 6. Royal Lake Facts Drainage area =2,477 acres (3.67 square miles) Lake surface area =37.5 acres Sediment pool capacity =416,000 cubic yards (CY) Current sediment in lake =100,400 CY Estimated annual sediment load =4,400 CY50 feet100,400 CY
  • 7. Royal Lake
  • 8. Royal Lake: Sediment Thickness
  • 9. Royal Lake: Water Depth
  • 10. Royal Lake: Dredging Areas Phase 1: Base Dredge = 40,000 CY Phase 2: Up to an additional 60,000 CYZone D12,400 CY
  • 11. Royal Lake: Partial Drawdown
  • 12. Dredging Methods and Alternatives1. Mechanically dredgedeposited sediment andhaul wet2. Drain lake and drydeposited sediment inplace before hauling
  • 13. PRE-DREDGING:An estimated35,000 cubic yardsof sediment hadaccumulated inthe lake, formingislands andreducing waterlevels to less thanthree feet in mostareas.Lake Barton Example
  • 14. Lake Barton Example: Pre-Dredging
  • 15. LakeBartonExample: DredginginProgressDredging:Dredging tookplace withoutdraining the lake.
  • 16. LakeBartonExample: DredginginProgress
  • 17. Lake Barton Example: Disposal Site
  • 18. North Park Lake Example Allegheny County, PennsylvaniaDredging:The lake was drainedand the sediment wasdried in-place.
  • 19. North Park Lake Example Allegheny County, PennsylvaniaTemporary DiversionChannelsEquipment Workingon Next Slide
  • 20. North Park Lake: Dredging Allegheny County, PennsylvaniaTruck WashTemporaryDiversion ChannelLow PressureExcavatorBulldozerBulldozerExcavatorand DozerTruck AccessStaging
  • 21.  General Sequence– Establish access and staging areas– Conduct dredging utilizing barges– Haul wet sediment to disposal sitefor drying Benefits– Less weather dependent– Quicker initial start to dredging– Less potential for scheduleextensions or delay Concerns– Increased sediment handling effortat disposal area– Potentially higher costDredge Alternative – In the Wet
  • 22.  General Sequence– Initiate drawdown of lake– Establish access and staging areas– Establish diversion channels within lake– Conduct dredging Benefits– Higher daily sediment removal rates– Minimal sediment handling effort at disposalarea– Potentially lower cost Concerns– Very weather dependent– Higher potential for delays due to weather– Typically more odor from sediment exposed– Need to relocate/salvage fishDredge Alternative – In the Dry
  • 23.  In-lake forebay Wetland planting Shoreline stabilization Fish habitat Fish stockingLake RestorationFish habitat createdfrom salvaged treesLake Barton:Fish stocking by Virginia Game and Inland Fisheries
  • 24. Royal Lake: Shoreline Restoration
  • 25. Royal Lake: Shoreline RestorationRoyal LakeExistingConditions
  • 26. Shoreline Protection Options
  • 27. Fish Habitat Structures
  • 28. Royal Lake: Site Access and StagingOptional?
  • 29. Royal Lake: Site Access and Staging
  • 30. Staging Area 1 Potential ExpansionBerm/Cofferdamto be builtArea to be dewatered andbackfilled to expand stagingarea after berm/cofferdamis built
  • 31. Royal Lake: Dewatering BasinInactiveDewatering Basin
  • 32. Access During ConstructionPublic Access:The park will remainopen and existingparking lot will beavailable.
  • 33. Access During ConstructionPublic Access:Pedestrian gates will beprovided. Accessthrough work areas andtrails around the lakeafter work hours.
  • 34.  Community coordination at design and construction phases– Preliminary Design (65%)– Final Design (95%)– Preconstruction: “Pardon Our Dust” meeting December 2013: Final Design Construction in Fiscal Year 2015 (Starts July 2014) Project Duration:– Phase 1, Base Dredge: Dredge 40,000 CY = 5 to 6 Months– Phase 2, Full Dredge: 9 to 12 MonthsRoyal Lake Dredging and RestorationProject Timeline and Coordination
  • 35. Contacts: Martin Chang, Project Manager703-324-5825 | Dipmani Kumar, Section Chief703-324-4612 | Lake DredgingandRestoration