Creating and Executing Practical Performance Specifications for Deep In-situ Solidification/Stabilization


Creating and Executing Practical Performance Specifications for Deep In-situ Solidification/Stabilization

Dan Amate, P.E., Rich Beck and Joe Foglio (GZA GeoEnvironmental, Inc.)


Dan Amate, P.E.

GZA GeoEnvironmental, Inc.

Speaker Bio:

Mr. Amate has more than 15 years of professional experience in soil and groundwater remediation and construction management at former manufactured gas plant (MGP) sites, Superfund Sites (EPA Regions 2 and 3), and manufacturing facilities. He serves as lead remediation engineer in GZA’s Metro Philadelphia offices and is responsible for the selection, design, permitting, and implementation of Remedial Actions in challenging regulatory and physical environments. He also has experience in storm water management; geotechnical investigations; geotechnical instrumentation installation, monitoring, and data interpretation; retaining wall design and installation; and landfill construction, design, and permitting.


Polycyclic aromatic hydrocarbons (PAHs), benzene, naphthalene and free phase coal tar have been delineated in sandy soils from grade to approximately 65 feet below ground surface (bgs) at this small former manufactured gas plant (MGP). The former MGP site is currently occupied by a municipal water authority, which operates multiple production wells on the property and a century old water tower; a popular convenience store; and a former electric switch station. The extent of impacted soil is generally limited to the footprint of the former facility. Impacted groundwater has migrated offsite, resulting in a narrow plume extending approximately 2,000 feet downgradient but is limited vertically by a confining clay layer below the contaminated sandy soil. Given the depth of impact and regulatory constraints which require achievement of background concentrations of contaminants (PQL), In-Situ Solidification/Stabilization (ISS) was selected as the remedy. GZA developed performance-based specifications that were designed to challenge contractors to use their ISS treatment experience to execute a laboratory and field scale program to achieve conservative performance criteria. Performance criteria included traditional parameters (e.g., permeability, unconfined compressive strength, free product mobility) as well as a real time testing program to verify complete and consistent treatment of the material. The ISS program included bench and pilot scale concept testing before proceeding to full-scale treatment. The contractor utilized two custom ISS rigs to treat soils with 8.5 and 10 foot diameter augers to 65 feet below grade. The presentation will discuss how GZA and the contractor used the Performance Specifications as a tool to overcome and adapt to challenges presented throughout the project. In addition, cost saving measures including reuse of swell as backfill and use of ISS treated soil as an excavation support system will be discussed.

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