Royal Lake Dredging and Restoration Fairfax County Department of Public Works and Environmental Services

2.  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

3.  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

4.  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

5.  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

6. 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

7. 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

8. Royal Lake

9. Royal Lake: Sediment Thickness

10. Royal Lake: Water Depth

11. 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

12. Royal Lake: Partial Drawdown

13. Dredging Methods and Alternatives
1. Mechanically dredge
deposited sediment and
haul wet
2. Drain lake and dry
deposited sediment in
place before hauling

14. 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

15. Lake Barton Example: Pre-Dredging

16. LakeBartonExample: DredginginProgress
Dredging:
Dredging took
place without
draining the lake.

17. LakeBartonExample: DredginginProgress

18. Lake Barton Example: Disposal Site

19. North Park Lake Example Allegheny County, Pennsylvania
Dredging:
The lake was drained
and the sediment was
dried in-place.

20. North Park Lake Example Allegheny County, Pennsylvania
Temporary Diversion
Channels
Equipment Working
on Next Slide

21. North Park Lake: Dredging Allegheny County, Pennsylvania
Truck Wash
Temporary
Diversion Channel
Low Pressure
Excavator
Bulldozer
Bulldozer
Excavator
and DozerTruck Access
Staging

22.  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

23.  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

24.  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

25. Royal Lake: Shoreline Restoration

26. Royal Lake: Shoreline Restoration
Royal Lake
Existing
Conditions

27. Shoreline Protection Options

28. Fish Habitat Structures

29. Royal Lake: Site Access and Staging
Optional?

30. Royal Lake: Site Access and Staging

31. 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

32. Royal Lake: Dewatering Basin
Inactive
Dewatering Basin

33. Access During Construction
Public Access:
The park will remain
open and existing
parking lot will be
available.

34. Access During Construction
Public Access:
Pedestrian gates will be
provided. Access
through work areas and
trails around the lake
after work hours.

35.  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

36. Contacts:
 Martin Chang, Project Manager
703-324-5825 | Martin.Chang@fairfaxcounty.gov
 Dipmani Kumar, Section Chief
703-324-4612 | Dipmani.Kumar@fairfaxcounty.gov
 http://www.fairfaxcounty.gov/dpwes/stormwater/
Royal Lake DredgingandRestoration
http://www.fairfaxcounty.gov/NVSWCD/ http://www.fairfaxcounty.gov/parks/