Piers 24 & 25 Sediment Remediation Project
Tacoma, Washington
or… Adventures in Underpier CappingAdventures in Underpier Capping
Rick Moore, Hart Crowser
WEDA Pacific Chapter ConferenceNovember 5, 2009
Acknowledgments• Port of Tacoma• US EPA• US Army Corps of Engineers• Washington State
Department of Ecology• Bergerson Construction• Berger/ABAM
Presentation Overview
Project Setting and Background
Commencement Bay CERCLA ActionsHow Did We Get Here? When Will We Be Done?
Remediation ElementsWhy Do These Projects Always Happen in the Winter?
Lessons LearnedThe Good, the Challenged, and the Long-Term.
Historical Tideflat Filling
Commencement Bay Nearshore/ Tideflats Superfund SiteModified From Port of Tacoma Photo Slide
Sitcum
Hylebos
Thea Foss
Middle
St. Paul
Piers 24 & 25 Project
Site
CERCLA Background• Commencement Bay/Nearshore
Tideflats Superfund Site– Work Began Mid-1980s– 1989 EPA Record of Decision– 20+ Year Cycle to Complete Remediation
• Piers 24 & 25– Part of Mouth of Hylebos Remedial Action – One of the Last CB/NT Remediation Efforts
Site Vicinity and Project Area2006 Aerial
Photo
Source: City of Tacoma
Hylebos Waterway
Blair Waterway
Piers 24 and 25 Project Site
Site Contaminants
• PAH, Metals, and PCB Contamination from Historical Shipyard Waste Disposal
• A Convenient Place to Dump Waste
• A Difficult Place to Clean Up
1940s Shipyard
Piers 24 & 25 Project Site
1946 Aerial Photo
Piers 24 & 25 Project Timeline• 1998 to 2000 Remedial Design
• EPA AOC 2002 and CD 2005
• 2000 to 2007 Revise/Finalize Design
• 10/07 and 2/08 Complete Construction
Remediation Elements• Embankment Capping on 2V:1H Slopes
• Hot Spot Dredging for As Contamination
• Debris Pile Removal
• Hot Spot PCB Removal
A Difficult Place to Work
• Limited Access
• Forest of Pilings
• Steep, Slippery Rock Slopes
Barge-Mounted Placement of Capping Materials
Pier-Mounted Placement of Capping Materials
Sand Cap and Armor Rock Placement
Sand Cap and Armor Rock Placement
Toe Berm Riprap Placement
Sand Cap and Armor Rock
Lead Line Survey Control
Project Area - Post-Capping
Shotcrete Application
Photo Courtesy of the Port of Tacoma
Shotcrete Application
Piers 24 & 25 Project Area
Debris Pile Removal
PCB Hot Spot Removal
PCB Hot Spot Removal
Lessons Learned – The Good• Construction Methods Successful for
Steep Slope Capping
– Sand Cap 400 to 700 CY/Shift
– Crushed Armor Rock 400 to 600 CY/Shift
– Shotcrete 6 to 10 CY/Shift
• Total Construction Cost $4.6M – Within 1% of Engineering Estimate Excluding
Change Orders
The Challenged• PCB Hot Spot and Deeper Debris
Excavation Were Unexpected and Costly
– Difficult Setting to Obtain Good Sampling Data
• 50% Toe Berm Riprap Quantity Over-Run
– Difficult to Estimate Riprap Repose Angle and Settling
And The Long Term…• Piers 24 & 25 Cap Performing as Intended
• Remediation Complete:– Sitcum, Milwaukee, St. Paul, Thea Foss/Wheeler Osgood
Waterways, and ASARCO
• Remediation Pending: OXY/Area 5106
• CB/NT In Post-Construction Monitoring – Portions of the Blair and St. Paul Waterways
Delisted/Deleted from NPL
Thanks to WEDARick MooreHart [email protected]
m(206) 826-4521
Bill Evans Port of [email protected](253) 593-4563
5106 and “OXY” In-Water Areas
Commencement Bay Waterways