Understanding MGP operations and subsurface geology/hydrogeology
Since the mid-1980’s, GZA has worked on MGPs in settings ranging from small facilities in remote locations to substantial facilities in densely populated urban areas adjacent to marine and freshwater environments. From karst, to bedrock, to clay, to sand, and sediment, each MGP site presents its own set of surface and subsurface challenges. These must be understood in the context of former operations to develop effective conceptual site models both for investigation and remediation. We use our nationally known geotechnical, hydrogeological and remediation engineering expertise, coupled with our understanding of historical MGP processes, operations and by-product management, to focus on effective investigation and remedial alternatives.
Combining Science with Field Expertise and Data Management
Developing or refining a conceptual site model depends on integrating all sources of historical information, collecting quality data, and incorporating the data into a database that is used to further refine delineation. Visualizing subsurface conditions allows GZA to develop realistic investigation plans to locate and quantify impacted media. Our experience with investigation techniques, computer modelling, and data management optimizes site investigation time and expenses. GZA’s technical expertise is enhanced by our management skills in coordinating and obtaining the necessary permits, site access agreements, and subcontractors.
- Groundwater Modeling; Fate and Transport Modeling
- Subsurface and Sediment Investigation
- Soil and Groundwater Sampling & Analysis, including:
- EPA Low-Flow Sampling Protocols
- Cone-Penetration Testing (CPT)
- Ground Penetrating Radar (GPR)
- Tar-specific Green Optical Screening Tool (Tar GOST®)
- UV-Based Fluorescence Systems
- Database Management and Data Interpretation
- Impacted Sediment Evaluation
- Utility Assessments and Investigations (Camera Surveys)
- Human Health and Environmental Risk Characterization
Developing Client-focused Solutions
GZA is a solution-focused engineering firm which develops remedial alternatives to meet our Client’s risk tolerance, comply with regulatory requirements, and which can be implemented in the real world. Where allowed by regulation and with supporting data, we have developed health-based risk assessments coupled with monitored natural attenuation (MNA). In cases where MNA is not appropriate, GZA has developed cost-effective remedial alternatives to address impacted soil, sediment, and groundwater. We provide our clients with probability-based cost estimates and estimated construction schedules that account for completeness of data, regulatory interaction, permitting, and our field experience managing various remedial alternatives. GZA works with our clients to develop community outreach solutions that clearly explain the approach and impact to regulatory agencies and third party stakeholders, while addressing their concerns.
- Alternative Remediation Scenarios
- Technology Evaluation
- Probabilistic Cost Estimates and Feasibility
- Public Stakeholder Outreach and Education
- Web-based Project Specific Information
Comprehensive Design and Experienced Implementation
Developing “constructable” project plans and executing construction-based remediation at former MGP sites are trademarks of GZA. Since our entrance into the MGP practice, our personnel have designed and implemented a number of different remedies, based on subsurface conditions, that include: facility decontamination and demolition; support of excavation for deep cuts (steel sheeting, tie backs, and bracing); tangent and secant excavation techniques; dewatering; groundwater treatment; product recovery; in-situ chemical oxidation; groundwater cutoff walls with SB and CB mixes using slurry wall techniques; in-situ stabilization using augers, bucket mixing, deep soil mixing cutterheads, and chain mixing technology; jet and permeation grouting; engineered soil and sediment capping; real-time air monitoring systems; automated optical monitoring of adjacent structures; and sediment removal and site restoration.
Because a majority of MGP sites are located in or near residential communities, completing these projects requires a thorough understanding of the level of effort required to complete the construction, execute the technical objectives of the work, and interact with local authorities and the general public, while keeping projects on-time and on budget. GZA provides comprehensive Construction Management services for these challenging MGP projects. Our CMs routinely have more than 20 years of experience managing demolition and/or remediation projects on As-Agent and At-Risk project delivery systems.
- Construction Management
- Excavation and Support of Excavation Design
- Steel Sheeting
- Tie Backs
- Tangent and Secant Excavation
- Dewatering, Groundwater Treatment, Product Recovery
- In-Situ Stabilization and Treatment
- Jet and Permeation Grouting
- Cutoff Walls
- Facility Decontamination
- Sediment Removal
- Site Restoration
- Real-time Air Monitoring Programs
- Real-time Structural Monitoring Programs