Innovations in the Use of Organoclay and Surface-Modified Clay for Manufactured Gas Plant Remediation
Matt Geary, Technical Sales Manager, CETCO/Minerals Technologies, Inc.
Co-Author: Anna Willett, PE, CETCO/Minerals Technologies, Inc.
A comprehensive approach to Manufactured Gas Plant (MGP) remediation incorporates source control via In-Situ Stabilization (ISS) and Permeable Reactive Barriers (PRBs) for downgradient groundwater contamination, as well as in-situ capping for contaminated sediment. ISS reduces or eliminates downgradient impacts, while PRBs prevent migration of contamination off-site and sediment capping minimizes dredging requirements. Organoclay and surface-modified clay, such as Fluoro-sorb® Adsorbent have a high adsorptive capacity for a wide variety of contaminants at MGP sites. Organoclay binds contaminants like nonaqueous phase liquids (NAPLs), PAHs, PCBs, and other hydrocarbons. Surface-modified clay is effective for treating perfluoroalkyl and polyfluoroalkyl substances (PFAS). There have been numerous successful installations of these treatment media and several case studies will be presented.
ISS uses organoclay or surface-modified clay to stabilize organic contaminants in soils in conjunction with solidification agents, such as Portland cement or bentonite, that reduce hydraulic conductivity. The amount of media required can be determined by testing varying percentages (typically 1-5% by weight) in mix designs and conducting leaching tests to see which mixture meets the design specifications.
PRBs with organoclay or surface-modified clay can be used to treat mobile contamination downgradient of source areas. To implement a PRB, contaminant concentrations and hydrogeologic information are used to estimate the mass of contaminants that are moving through the barrier over time. PRB dimensions and dosing can be developed using the adsorptive capacity of organoclay or surface-modified clay.
Organoclay and surface-modified clay can be used in thin layer caps to sequester contaminants, maintain navigability, and safely preserve habitat in waterways. Some of the approaches that are used for in-situ active capping are:
Matt Geary has over 34 years of experience in the environmental consulting/construction industry, ranging from his role as a site superintendent for one of the nation’s largest remediation construction firms to managing a remediation estimating department and serving as a Vice President of a mid‐sized environmental consulting firm. Covering the East Coast of the United States and Eastern Canada for CETCO, Matt has extensive knowledge of local, state, provincial and federal regulations. He served as a member of the Brownfield Action Committee (BAC) for The Delaware Department of Natural Resources and Environmental Control and has presented technical papers and case studies at many local and national conferences relating to PFAS Remediation, MGP site remediation, sediment capping and In‐Situ Solidification and Stabilization (ISS) and Vapor Intrusion Mitigation. Matt has a B.S. in Environmental Resources Management from the Pennsylvania State University, State College PA.
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