Royal Lake Dredging and Restoration Project Update-June 2014

2. 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

3.  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

4.  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

5. 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

6. Royal Lake: Sediment
Thickness

7. Royal Lake: Water Depth

8. 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

9.  Total Wetlands
Impact:
– 0.85 Acre
 All impacts
within original
footprint of
lake
Royal Lake – Wetland Impact

10. Project Overview
Staging Areas
Sediment Forebays Lake grading to
restore the original
bottom elevation

11. Site Access and Staging

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

13. 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.

14. 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

15. Royal Lake: Dewatering Basin
Inactive dewatering basin
to be filled in and restored
Staging area
potential
expansion

16. Phase I and Phase II Dredging
PHASE II
48,000 CY
PHASE I
15,000 CY
PHASE I
40,000 CY

17. 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.

18.  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

19.  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)

20. 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

21. Huntsman Lake (29 acres)
Huntsman Lake – Currently being dredged in the dry

22. Huntsman Lake Dam Rehabilitation Project Fish Relocation (May, 2013)

23. Huntsman Lake Improvements
forebay
forebay berms
dam
embankment
Phase I dredging limits (34,500 CY)
Huntsman Lake Improvements

24. Huntsman Lake Dredging
June, 2014

25.  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

26. Royal Lake: Shoreline
Restoration

27. Shoreline Protection

28. Fish Habitat Structures

29.  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

30. Contacts:
Martin Chang
martin.chang@fairfaxcounty.gov
Dipmani Kumar
dipmani.kumar@fairfaxcounty.gov
Matt Meyers
matthew.meyers@fairfaxcounty.gov
Stormwater Planning Division
Fairfax County DPWES
(703)324-5500, TY 711
Partners:
Royal Lake Dredging and
Restoration