Woodglen Lake Dredging and Restoration

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Woodglen Lake Dredging and Restoration Department of Public Works and Environmental Services Project Update, September, 2013

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  • 1.Woodglen Lake Dredging and Restoration Department of Public Works and Environmental Services Project Update, September, 2013

2. Woodglen Lake: Meeting Agenda Project Goals and Status Woodglen Lake Conditions Project Overview Site Access and Decanting Basin Restoration Dredging Approaches Streambank Stabilization Lake Habitat Restoration Project Timeline February Meeting highlights Questions and Answers 3. Project Goals Restore sediment pool and create in-lake forebay Aesthetics Long-term downstream water quality benefits Improve lake water quality and habitat Stabilize two stream locations to protect access road Remove existing decanting basin and provide long term maintenance improvements 4. Woodglen Lake: Project Status Data collection completed Lake dredging and management plan completed Design plans and specifications Preliminary design completed Final design current design phase Permitting Late 2013: complete final design Begin construction in spring 2014 5. Woodglen Lake Facts Drainage area = 740 Acres (1.15 square miles) Lake surface area = 12.5 acres Sediment pool capacity = 160,000 cubic yards (CY) Current sediment in lake = 29,300 CY Estimated annual sediment load = 1,200 CY / year 16.6 feet 29,300 CY 6. Woodglen Lake: Sediment Depth 7. Woodglen Lake: Water Depth 8. Woodglen Lake: Project Overview Staging Area Improved access road Sediment forebay Lake dredging, shoreline restoration, lake habitat improvement Removal and restoration of decanting basin Potential reforestation areas 9. Dredging Approaches 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 option for dry dredging: drawing the lake down by 9 feet would leave a 3.5 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. 10. Woodglen Lake: Site Access and Staging 11. Woodglen Lake: Decanting Basin Restoration Realigned access road and restored decanting basin 12. Wet Dredging 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 Cons Increased sediment handling effort at disposal area Potentially higher cost 13. Dry Dredging (Full or Partial Drawdown) General Sequence Initiate drawdown of lake Establish access and staging areas Establish diversion channels within lake Conduct dredging Pros Higher daily sediment removal rates Minimal sediment handling effort at disposal area Potentially lower cost Cons Very weather dependent Higher potential for delays due to weather Even with a reduced pool, there will be a need to relocate/salvage fish 14. Huntsman Lake Dam Rehabilitation Project Fish Relocation (May, 2013) 15. Woodglen Lake: Partial Drawdown Staging Area A partial drawdown would leave a 3.5 acre pool with a maximum depth of 5 feet with an average depth of 1 to 2 feet. Approximate volume of sediment to be removed 15,000 CY 16. 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 17. Chesapeake Bay Preservation Areas Buffer restoration in deficient areas 18. Woodglen Lake: Shoreline Restoration Existing Shoreline Condition 19. Woodglen Lake: Shoreline Protection Image Courtesy of North Fork Native Plants 20. Fish Habitat Structures Photos Courtesy of the Pennsylvania Fish and Boat Commission Nesting Structure Porcupine Crib Jr. Rock Rubble Piles Post Clusters 21. Stream Stabilization North Stream Stabilization Area South Stream Stabilization Area 22. Stream Stabilization Log Vane Geolift Imbricated Rock Wall 23. Access During Construction Pedestrian access to lake from Zion Drive will be maintained (after hours) Lake Barton example 24. Woodglen Lake: Project Status and Timeline Data collection completed Lake dredging and management plan completed Design plans and specifications Preliminary design completed Final design current design phase Permitting Late 2013: complete final design Begin construction in spring 2014 25. Woodglen Lake Dredging and Restoration Project Timeline Early 2014: construction bid advertisement Spring 2014: begin dredging Dredging method will depend on bid results Project duration: 6 to 7 months 26. February Meeting Discussion Highlights Dry/Wet dredging: in order to ensure a competitive bidding environment, both options have to be allowed, with partial drawdown an option for dry dredging Cheapest dredging method: depends on disposal site identified, either method could be cheaper Project cost-effectiveness: forebay and maintenance enhancements make this project cost-effective from the viewpoint of downstream water quality improvements and long-term costs 27. Huntsman Lake (29 acres) 28. Woodglen Lake Dredging and Restoration Contacts Dipmani Kumar, Project Manager 703-324-4612 Dipmani.Kumar@fairfaxcounty.gov Matt Meyers, Branch Chief 703-324-5651 Matthew.Meyers@fairfaxcounty.gov Partners:

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