a combined solution for sediment remediation and waterfront development a combined solution for...
TRANSCRIPT
A Combined Solution for Sediment Remediation and
Waterfront Development
John T. Finn, P.E.
GEI Consultants, Inc.
.
Dredging 2012
The Problem
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• Removal of Sheen-Producing Sediments
• Protection of Existing Bulkheads
• Capping of Remaining Sediments
• On-site Solidification of Dredged Sediments
• Preparation for Waterfront Redevelopment
A Complex Problem: A Combined Solution : John Finn, GEI
Dredging 2012
Location: A Slip in New Bedford Harbor
Manufactured Gas and Tar Plant 1880 - 1960
OUTER SLIPIN
NER
SLIP
Dredging 2012
Outer Slip:
- Remove all sheen-producing sediment in top foot
- No off-site disposal:
Place all dredged sediment in Inner Slip
- 2-foot Composite Cap
Inner Slip - Solidify dredged sediment and existing sediment/soil
to bedrock
- Prepare the site for waterfront redevelopment
Minimum Remedy Requirements
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Remediation – Plan View
Cell 2 Cell 1
Capping Area
Fixed Turbidity Curtain
Dredged Areas for Tar Removal
Dredged Area for Cap Installation
ISSMixing Plant
Water Treatment
Facility
Sheet Pile Walls
Inner Slip ISS & Fill Area
• Protection of bulkhead stability
• Final elevation allows sufficient draft for boat traffic
• Limited capacity of Inner Slip:
- Account for expansion upon solidification
- Account for expansion/settling upon dredging/placement
Dredging Requirements and Constraints
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Dredging Behind Dual Curtains & Booms
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Dredging of Outer Slip
Vapor & Odor Suppression Foam
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GPS Positioning of Dredge Bites
Capping of Remaining Sediments
Benthic Sand – 12 inches
Stone Armor – 3 inches
Gravel – 3 inches
AquaBlok – 6 inches
Sand Fill – thickness varies
AquaBlok
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Cap Placement
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Solidification: Inner Slip – Section View
Cell 2 Cell 1
Existing Bulkhead
Top of Bedrock (El. -24.2)
New Sheet Pile Closure Walls
Top of Dredge SpoilsTop of Sediments
Mean High WaterMean Low Water
Top of Dredge Spoils
Top of Bedrock (El. -39.0)
Soil Mixing to Solidify Sediments
• 1,350 cubic yards dredged• 18,000 ft2 dredge area• 190 - eight foot diameter ISS columns• 37 - three foot diameter ISS columns• 7,000 - cubic yards of sediment and soil
mixed• 427 ton of AquaBlok
Dredging, Capping, and ISS Statistics
Site Ready for Waterfront Development
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Questions?
Thank You
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• Environmental Business Council’s
2012 Award for Collaboration
• Study of In-Situ Solidification of Contaminated Sediments, Sponsored by the Electric Power Research Institute (EPRI)
Post-Scripts
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• MassDEP leadership streamlined complex permitting– Reached out to federal, state & local regulators– Coordinated multi-agency team approach – Hosted & facilitated 2 critical multi-agency meetings
• Public engagement– Public notice soliciting public comments on
10/23/2010 – Public meeting on 12/8/2010 with USEPA and
MassDEP
• Innovative MCP site closure strategy
Coordinating Multiple Agencies
• MassDEP– Release Abatement Measure Plan– 401 Water Quality Certification– Chapter 91 License
• EPA – TSCA 61C – Risk-Based Cleanup Plan
• U.S. Army Corps of Engineers, New England District– Category 2 General Permit
• New Bedford Conservation Commission - Wetland Order Of Conditions
• Property Owner Agreement: Fueling Terminal Ops
Permitting and Legal Framework
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Dredge Cut Lines
Min.
Max.
El -14.
El -15.
Min.
Max.
El -14.5
El -14.
Tolerance Near Bulkheads Tolerance In All Other Areas
Dredging 2012