Manufactured Gas Plant (MGP) Remediation

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.

GZA is a solution-focused engineering firm which develops manufactured gas plan remediation 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.

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.