Woodglen Lake Dredging and Restoration

Woodglen Lake Dredging and Restoration Department of Public Works and Environmental Services

Project Update, September, 2013

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

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

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

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

Woodglen Lake: Sediment Depth

Woodglen Lake: Water Depth

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

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.

Woodglen Lake: Site Access and Staging

Woodglen Lake: Decanting Basin Restoration

Realigned access road and restored

decanting basin

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

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

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

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

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

Chesapeake Bay Preservation Areas

Buffer restoration in deficient areas

Woodglen Lake: Shoreline Restoration

Existing Shoreline Condition

Woodglen Lake: Shoreline Protection

Image Courtesy of North Fork Native Plants

Fish Habitat Structures

Photos Courtesy of the Pennsylvania Fish and Boat Commission

Nesting Structure

Porcupine Crib Jr. Rock Rubble Piles

Post Clusters

Stream Stabilization

North Stream Stabilization Area

South Stream Stabilization Area

Stream Stabilization

Log Vane

Geolift

Imbricated Rock Wall

Access During Construction

Pedestrian access to lake from Zion Drive will be maintained (after hours)

Lake Barton example

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

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

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

Huntsman Lake (29 acres)

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: