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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

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

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

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

Royal Lake: Sediment Thickness

Royal Lake: Water Depth

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

Total Wetlands Impact:– 0.85 Acre

All impacts within original footprint of lake

Royal Lake – Wetland Impact

Project Overview

Staging Areas

Sediment Forebays Lake grading to restore the original bottom elevation

Site Access and Staging

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 will be possible after work hours.

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 basinto be filled in and restored

Staging area potential

expansion

Phase I and Phase II Dredging

PHASE II48,000 CY

PHASE I15,000 CY

PHASE I40,000 CY

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.

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

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)

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

Huntsman Lake (29 acres)

Huntsman Lake – Currently being dredged in the dry

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

Huntsman Lake Improvements

forebay

forebay berms

dam embankment

Phase I dredging limits (34,500 CY)

Huntsman Lake Improvements

Huntsman Lake Dredging June, 2014

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

Royal Lake: Shoreline Restoration

Shoreline Protection

Fish Habitat Structures

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

Contacts:Martin Chang martin.chang@fairfaxcounty.govDipmani Kumardipmani.kumar@fairfaxcounty.govMatt Meyersmatthew.meyers@fairfaxcounty.gov

Stormwater Planning DivisionFairfax County DPWES(703)324-5500, TY 711

Partners:

Royal Lake Dredging and Restoration