Royal Lake Dredging and Restoration Project Update-June 2014

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Royal Lake Dredging and Restoration Project Update-June 2014


  • 1.Royal Lake: Meeting Agenda Introductions and Opening Remarks Project Goal and Status Royal Lake Conditions Project Overview Site Access Dredging Phase I and Phase II Dredging Alternatives Lake Habitat and Shoreline Restoration Project Timeline Questions and Answers

2. Restore Sediment Pool Capacity Downstream water quality benefits Lake water quality Aesthetics Improve Lake Water Quality and Habitat Provide Long Term Maintenance Improvements Project Goals and Benefits 3. Completed Data Collection Completed Lake Dredging and Management Plan Design Plans and Specifications Preliminary Design Completed Final Design Current design phase Permitting In Progress Late 2014/Early 2015 Complete Final Design and Permitting Dredging Projected to Start in Late Summer, 2015 Royal Lake: Project Status 4. 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 = 103,000 CY* Estimated Annual Sediment Load = 4,400 CY 50 feet 103,000 CY * Based on a 2013 bathymetric survey 5. Royal Lake: Sediment Thickness 6. Royal Lake: Water Depth 7. Royal Lake: Sediment Sampling Results Samples were analyzed for chemicals found in typical urban environments All tests indicated significantly lower concentrations than state limits except for Arsenic Nitrogen and Phosphorous levels were elevated With dredging of 103,000 CY: Approximately 8,500 lbs of Phosphorous will be removed Approximately 102,000 lbs of Nitrogen will be removed 8. Total Wetlands Impact: 0.85 Acre All impacts within original footprint of lake Royal Lake Wetland Impact 9. Project Overview Staging Areas Sediment Forebays Lake grading to restore the original bottom elevation 10. Site Access and Staging 11. Access During Construction Public Access: The park will remain open and existing parking lot will be available. 12. Access During Construction Public Access: Pedestrian gates will be provided. Access through work areas and trails around the lake will be possible after work hours. 13. Staging Area 1 Potential Expansion Berm/Cofferdam to be built Area to be dewatered and backfilled to expand staging area after berm/cofferdam is built 14. Royal Lake: Dewatering Basin Inactive dewatering basin to be filled in and restored Staging area potential expansion 15. Phase I and Phase II Dredging PHASE II 48,000 CY PHASE I 15,000 CY PHASE I 40,000 CY 16. Dredging Alternatives 1. Wet Dredging: Mechanically dredge deposited sediment and haul wet. Normal pool maintained. (Note: This option will still require lake drawdown for a short period of time to build the forebay berms) 2. Dry Dredging: Drain the lake and dry deposited sediment in place prior to hauling 3. Project will be bid out with the option to dredge wet or dry Partial drawdown for Phase I dry dredging: drawing the lake partially to the Phase I dredging limits would leave a 15 acre pool; sediment would be dried in the dewatered section of the lake in place prior to hauling. Approximately 1/2 of the deposited sediment volume would be removed. 17. General Sequence Establish access and staging areas Conduct dredging utilizing barges Haul wet sediment to disposal site for drying Pros Less weather dependent Quicker initial start to dredging Less potential for schedule extensions or delay Concerns Increased sediment handling effort at disposal area Potentially higher cost Wet Dredging 18. 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 disposal area Potentially lower cost Concerns Very weather dependent Higher potential for delays due to weather Even with a reduced pool, there will be a need to relocate/salvage fish Dry Dredging (Full or Partial Drawdown) 19. Royal Lake: Partial Drawdown A partial drawdown would leave 15 acre pool with a maximum depth of 8 feet Sediment to be removed = 55,000 CY DRAW-DOWN 55,000 CY 20. Huntsman Lake (29 acres) Huntsman Lake Currently being dredged in the dry 21. Huntsman Lake Dam Rehabilitation Project Fish Relocation (May, 2013) 22. Huntsman Lake Improvements forebay forebay berms dam embankment Phase I dredging limits (34,500 CY) Huntsman Lake Improvements 23. Huntsman Lake Dredging June, 2014 24. In-lake forebay Wetland planting Shoreline stabilization Fish habitat Fish stocking Royal Lake Restoration Fish habitat created from salvaged trees Lake Barton: Fish stocking by Virginia Game and Inland Fisheries 25. Royal Lake: Shoreline Restoration 26. Shoreline Protection 27. Fish Habitat Structures 28. Community coordination at design and construction phase Pardon Our Dust meeting to be scheduled after contractor selection Late 2014/Early 2015: Complete final design Spring 2015: Bid advertisement Late summer 2015: Begin dredging Project Duration: Phase 1, Base Dredge: Dredge approximately 55,000 CY = 5 to 6 Months Phase 2, Full Dredge: 9 to 12 Months (total) Lake may be drained/partially drained for project depending on bid results For the wet dredge option, the lake will still require lowering for a short period to construct the forebays Royal Lake Dredging and Restoration Project Timeline and Coordination 29. Contacts: Martin Chang Dipmani Kumar Matt Meyers Stormwater Planning Division Fairfax County DPWES (703)324-5500, TY 711 Partners: Royal Lake Dredging and Restoration


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