Huntsman Lake Dam RehabilitationHuntsman Lake Dredging and Restoration

Department of Public Works and Environmental Services Pardon Our Dust Meeting

Fairfax County, VA

A Fairfax County, VA publication, October 2013

• Dam Rehabilitation – Background– Project Status– Sequence of Work– Major Project Elements

• Lake Dredging and Restoration– Background– Project Status– Dredging Phases– Lake Restoration

• Construction Timeline Summary• Safety• Q&A

Huntsman Lake Dam RehabilitationHuntsman Lake Dredging and Restoration

Pardon Our DustOutline

Huntsman Lake Dam Rehabilitation Project Background

• Huntsman Dam is operating under a conditional Operation & Maintenance (O&M) Certificate from the Virginia Department of Conservation and Recreation, Division of Dam Safety, because its auxiliary spillway can only convey about 50 percent of the flows from the design storm.

• Planning and design for this project was completed in February 2013, and Fairfax County and Northern Virginia Soil and Water Conservation District (NVSWCD) entered into a cost-share agreement with the Natural Resources Conservation Service (NRCS) to rehabilitate the facility in June, 2013.

• Project was advertised for construction on September 9, 2013.

• Bid opening: October 2nd, 2013• Two bids received; apparent low bidder is ASI

Constructors, Inc. • Construction contract will be managed by the Utilities

Design and Construction Division (UDCD), Fairfax County • UDCD is completing safety, qualification and reference

checks• Target date for contract execution*: November 16, 2013• Notice to Proceed (NTP): First week of December, 2013• Performance time: 240 days * Before a contract can be awarded, Natural Resources Conservation Service (NRCS) will review and concur with proposed construction schedule, subcontractors and performance bond.

Huntsman Lake Dam Rehabilitation Project Status

Huntsman Lake Dam Rehabilitation Project Summary of rehabilitation plan

Huntsman Lake Dam Rehabilitation Project Major Design Elements

Dam Rehabilitation General Sequence of Work

• Drawdown lake and flag limits of construction• Install perimeter controls• Clear some trees• Install Erosion and Sedimentation (E&S) controls• Rough-grade the area• Install cofferdam for diversion of water• Demolish the riser• Final-grade the area• Install Articulated Concrete Blocks (ACBs) • Build concrete structures (riser, cutoff wall system)• Lay topsoil and seed the area• Remove E&S controls

Huntsman Lake Dam Rehabilitation Project Spillway realignment and armoring

Huntsman Lake Dam Rehabilitation Project Spillway realignment and armoring

Huntsman Lake Dam Rehabilitation Project Spillway realignment and armoring

Huntsman Lake Dam Rehabilitation Project Riser replacement

Huntsman Lake Dam Rehabilitation Project Riser replacement

• Bid advertisement: October 14th, 2013• Mandatory pre-bid meeting: October 30th, 2013 • Bid opening: November 13th, 2013• Contract execution: middle of December, 2013 to early

January, 2014• Notice to Proceed (NTP): typically 2 weeks after contract

execution• Performance time:

– Phase I : 150 days– If Phase II is authorized: Additional 120 days

Note: For dredging, contract specifications state that the lake will be fully drained. The dam rehabilitation contractor will be responsible for lake drawdown, which is expected to take approximately 4 weeks.

Dredging and Lake Restoration Project Status

Background• Drainage area = 1,482 acres (2.3 square miles)• Lake surface area = 28.6 acres• Sediment pool capacity = 295,000 cubic yards (CY)• Current sediment in lake = 65,000 CY• Estimated annual sediment load = 2,970 CY

32.5 feet

65,000 CY

Huntsman Lake Dam Rehabilitation Project Fish Relocation (May 2013)

Sediment Thickness

Huntsman LakeSite Access and Staging Area

Huntsman Lake - Forebaysbank stabilization

aquatic bench

forebay

forebay berms

maintenance access

sanitary sewer

dam embankment

Phase I dredging limits (34,500 CY)

Dry DredgingLake Needwood in Montgomery County, MD

Dry Dredging

21

Dry DredgingLake Needwood in Montgomery County, MD

Lake Restoration

• In-lake forebay• Shoreline stabilization• Fish habitat• Fish stocking• Reforestation

Lake Barton: Fish stocking by Virginia Game and Inland FisheriesFish habitat created from salvaged trees

Shoreline RestorationHuntsman Lake Existing Conditions

Shoreline Restoration

Shoreline Protection

Reforestation

Huntsman Lake Dam RehabilitationHuntsman Lake Dredging and Restoration

Summary of construction timeline

• Lake drawdown and dam rehabilitation construction activities to start in December, 2013

• Dredging activities to commence after lake is fully drawn down by January, 2014

• Project duration: 9 months (both projects)• Lake will remain drained for entire project• Dam rehabilitation and dredging projects have been coordinated to

minimize the time lake is empty• Lake filling after project completion is dependent on rainfall

conditions, and it is expected filling will be initiated in September, 2014

Huntsman Lake Dam RehabilitationHuntsman Lake Dredging and Restoration

SAFETY

• Contractor is required to comply with Fairfax County’s Construction Safety Resolution. UDCD performs a review of the contractor’s safety record during the past 3 years.

• For all residents, keeping safe means following two simple rules:

1. Please stay outside the construction limits at all times! 2. Observe construction activities from a safe distance.

Huntsman Lake Dam RehabilitationHuntsman Lake Dredging and Restoration

For more information or questions, call the Stormwater Planning Division at 703-324-5500, TTY 711 or email: Dipmani Kumar: dkumar@fairfaxcounty.gov Matt Meyers: mmeye1@fairfaxcounty.gov

Utilities Design and Construction Division703-324-5111, TTY 711 or email:Bill Nolan (Dam Rehabilitation): wnolan@fairfaxcounty.gov Mannan Qureshi (Dredging): mqures@fairfaxcounty.gov

A Fairfax County, Virginia, publication October 2013To request this information in an alternate format, call 703-324-5500, TTY 711.

Thank you.