Passive (Aggressive) Barriers for Plume Remediation
In the past 20 years, zero-valent-iron-based permeable reactive barriers have evolved an experimental technology to being accepted, standard practice for a variety of groundwater contaminants. Now, new research, field experience and market developments have driven down costs and expanded applicability – from organic-loaded bio-barriers that treat out mobile metals, nitrate and perchlorate, to nonaqueous-phase liquid (NAPL)–absorbent barriers used to control creosote and coal tar contaminants at wood-treating sites and former manufactured gas plants. At the same time, effective monopolies on shallow single pass trenching techniques have been broken, depth records using bio-polymer trenching have fallen, and new techniques, such as soil-mixing, have been demonstrated as a means to very refresh reactive materials or spot-treat “gaps” in existing walls. Site owners and consultants dealing with long-term groundwater issues –on their own sites or coming in from up-gradient – need to be aware of recent operating experience, construction alternatives, and critical factors for success. “Passive” treatment has become far more aggressive than ever anticipated.
This presentation includes an overview of reactive barrier practice, design guidance, and an apples-to-apples comparison of installation methods, costs and constraints, as well as case studies for mine seepage, permeable absorbent (PAB) NAPL barriers, reworking chlorinated iron walls and deep drain infrastructure installation using liquid shoring methods.