USEPA Superfund Mega-Site
Engineered Cap Design Support
Under Sole Source Contract W912WJ-18-C-0003 Lally Consulting LLC (Lally LLC) provided project-defining sediment remediation technical advisory services at the New Bedford Harbor Superfund Site.
At the request of the USACE – New England District, Lally LLC authored the project design guidance for the NBHSS caps to be installed at subtidal locations with contamination that could not effectively be addressed through removal. Based on site physical and chemical conditions, Lally LLC introduced to the project multi-layer engineered caps as the recommended approach for the contamination levels and locations requiring confinement. The cap guidance document provided functional descriptions of physical isolation, chemical isolation, and erosion control layers, cap materials including active components, design and construction considerations, contaminant flux models, and quality control guidance.
Lally LLC was thereafter requested by USACE / USEPA to develop Krig-derived cap designs to ensure a consistent methodology for the site’s seven (7) permanent subaqueous caps. The cap designs accounted for steep slopes, hydrodynamic conditions, integration with intertidal remediation in some cases, and introduced Nature-based engineering techniques to improve habitat conditions and wave attenuation functionality.
How we Helped
Specific Cap Design Services performed by Lally LLC at the request of USACE and USEPA included;
- Author project cap design technical guidance.
- Provide guidance on thin-layer capping approaches for more uniform placement of capping materials at higher production rates.
- Participate in development of Aerovox Interim Cap Design.
- Participate in weekly cap planning, design and operations meetings with project teams.
- Develop hydrodynamic modeling runs with Deltares and analyze to estimate bed shear stresses at specific NBHSS subaqueous cap locations for various recurrence interval storm conditions.
- Recommend increased Erosion Control Layer to contend with storm-induced velocities and bed shear.
- Provide guidance on design and construction of Aerovox engineered cap, with respect to placement accuracy, production efficiency, and quality control.
- Develop cap materials and overage volume estimates and establish production estimates.
- Provide guidance and presentation graphics for improved capping construction methods, equipment and quality control to meet design requirements with greater efficiency.
- Introduce Daily Effective Time and Delay Category Reporting for improved cap operations.
- Coordinate with USACE Oversight Personnel regularly.
- Analyze capping survey, coring data, and produce new quality assurance products including survey data graphics, accuracy isopachs, statistics, and DREDGEPACK plots for Aerovox cap closure.
- Run CapSim model simulations for sensitivity analysis of decay, Koc/Kow coefficients, and cap breakthrough estimates. Significantly reduce project CapSim model run time durations.
- Develop CapSim modeling reports to facilitate USACE requested data and quality control checks.
- Perform propwash and armor sizing calculations to better assess erosion risk and improve cap designs.
- Identify and research potential bioturbation effects of Mantis Shrimp related to final engineered cap design.
- Design Krig‐derived Permanent caps including Crib cap, O‐711, L‐014, L‐114, Cogg East, Cogg West, and Area C Pilot CDF for better, more consistent and protective remediation.
- Assessed erosion / stability risks and improved cap / berm design using propwash model, armor sizing calculations, and slope stability model analysis.
- Conceptualize and assess alternative capping methods in complex areas.
- Develop alternative channel cap design (marine mattress), drawings, production and cost estimates.
- Provide guidance on Generic Design, Location Specific Designs, Construction Work Plans, Quality Control Plans, and Long-Term Monitoring Plans for engineered caps.
- Perform Slope Stability Analyses on subaqueous caps using SLIDE2 modeling software. Provide results and guidance to RAC A/E Contractor.
- Participate in weekly cap planning, design and operations calls with USACE/USEPA and project team.
Related Projects
Services Provided
Author Project Cap Design Guidance
Hydrodynamic Modeling for Cap Stability
Educate on SWATH Cap Placement Method
Cap Volume and Production Estimates
Ongoing Cap Quality Control and Production
Production and Quality Control Monitoring Tools
Contaminant Flux (CapSim) Modeling
Propwash and Armor Sizing Calculations
Design Krig‐derived Permanent Caps
Alternative Capping Methods
Slope Stability Analyses
Location
Massachusetts, USA
Period
2017 – 2020
For our work under this contract, Lally Consulting LLC received the highest overall Contractor Performance Assessment Reporting Systems (CPARS) rating of Exceptional from the Federal Government.
For its work under USACE Contract W912WJ-18-C-0003, Lally Consulting LLC was nominated by the NBHSS Project Leadership and selected by an awards panel of EPA representatives from across the Agency as the 2020 national recipient of the USEPA Administrator’s Award for Outstanding Accomplishments by a Small Business Contractor.