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Royal Lake Dredging and Restoration Fairfax County Department of Public Works and Environmental Services
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Dredging Program and Project Background
Project Benefits
Royal Lake Conditions
Phased Approach
Dredging Methods and Alternatives
Park Access and Community Coordination
Next Steps
Royal Lake: Meeting Agenda
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 Lake
Dredging and Lake Restoration Program
Completed Data Collection
Developing Lake Dredging and Management Plan
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 (July 2014)
Royal Lake Dredging and Restoration Project Timeline and Coordination
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 Benefit
Lake Barton Dredging and Restoration
Area Treated (acres)
Phosphorous Removal Nitrogen Removal Sediment Removal
544 77,000 lbs dredged 115,500 lbs dredged 38,500 tons dredged
Annual benefit from increased trapping
efficiency
130 lbs/year 200 lbs/year 65 tons/year
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 CY
50 feet
100,400 CY
Royal Lake
Royal Lake: Sediment Thickness
Royal Lake: Water Depth
Royal Lake: Dredging Areas
Phase 1: Base Dredge = 40,000 CY
Phase 2: Up to an additional 60,000 CY
Zone D
12,400 CY
Royal Lake: Partial Drawdown
Dredging Methods and Alternatives
1. Mechanically dredge deposited sediment and haul wet
2. Drain lake and dry deposited sediment in place before hauling
PRE-DREDGING: An estimated 35,000 cubic yards of sediment had accumulated in the lake, forming islands and reducing water levels to less than three feet in most areas.
Lake Barton Example
Lake Barton Example: Pre-Dredging
Lake Barton Example: Dredging in Progress
Dredging: Dredging took place without draining the lake.
Lake Barton Example: Dredging in Progress
Lake Barton Example: Disposal Site
North Park Lake Example Allegheny County, Pennsylvania
Dredging: The lake was drained and the sediment was dried in-place.
North Park Lake Example Allegheny County, Pennsylvania
Temporary Diversion Channels
Equipment Working on Next Slide
North Park Lake: Dredging Allegheny County, Pennsylvania
Truck Wash
Temporary Diversion Channel
Low Pressure Excavator
Bulldozer
Bulldozer
Excavator and Dozer Truck Access
Staging
General Sequence – Establish access and staging areas – Conduct dredging utilizing barges – Haul wet sediment to disposal site
for drying
Benefits – 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
Dredge Alternative – In the Wet
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 – Typically more odor from sediment exposed – Need to relocate/salvage fish
Dredge Alternative – In the Dry
In-lake forebay
Wetland planting
Shoreline stabilization
Fish habitat
Fish stocking
Lake Restoration
Fish habitat created from salvaged trees
Lake Barton: Fish stocking by Virginia Game and Inland Fisheries
Royal Lake: Shoreline Restoration
Royal Lake: Shoreline Restoration
Royal Lake Existing Conditions
Shoreline Protection Options
Fish Habitat Structures
Royal Lake: Site Access and Staging
Optional?
Royal Lake: Site Access and Staging
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
Royal Lake: Dewatering Basin
Inactive Dewatering Basin
Access During Construction
Public Access: The park will remain open and existing parking lot will be available.
Access During Construction
Public Access: Pedestrian gates will be provided. Access through work areas and trails around the lake after work hours.
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 Months
Royal Lake Dredging and Restoration Project Timeline and Coordination
Contacts:
Martin Chang, Project Manager 703-324-5825 | [email protected]
Dipmani Kumar, Section Chief 703-324-4612 | [email protected]
http://www.fairfaxcounty.gov/dpwes/stormwater/
Royal Lake Dredging and Restoration
http://www.fairfaxcounty.gov/NVSWCD/ http://www.fairfaxcounty.gov/parks/