Brownfields—A Canadian Perspective

Barriers to redevelopment of contaminated lands have led to vacant or underutilized sites termed “brown fields.” These barriers fall into six categories: regulatory, technical/scientific, legal/liability, financial, urbanplanning, and communications. The lack of protection to innocent parties, such as developers and lenders, and the lack of guidance for applying sitespecific and risk-based remediation approaches are two key barriers to redevelopment. This article presents guiding principles for redeveloping brownfields and recommends best practices toward overcoming existing barriers to such redevelopment. Success stories of redeveloped contaminated industrial sites are provided to illuminate the effectiveness of the best practices approach.     

Pilot scale testing composite swellable organosilica nanoscale zero‐valent iron—Iron‐Osorb®—for in situ remediation of trichloroethylene

Iron‐Osorb^® is a solid composite material of swellable organosilica with embedded nanoscale zero‐valent iron that was formulated to extract and dechlorinate solvents in groundwater. The unique feature of the highly porous organosilica is its strong affinity for chlorinated solvents, such as trichloroethylene (TCE), while being impervious to dissolved solids. The swellable matrix is able to release ethane after dechlorination and return to the initial state. Iron‐Osorb^® was determined to be highly effective in reducing TCE concentrations in bench‐scale experiments. The material was tested in a series of three pilot scale tests for in situ remediation of TCE in conjunction with the Ohio Environmental Protection Agency at a site in central Ohio. Results of these tests indicate that TCE levels were reduced for a period of time after injection, then leveled out or bounced back, presumably due to depletion of zero‐valent iron. Use of tracer materials and soil corings indicate that Iron‐Osorb^® traveled distances of at least 20 feet from the injection point during soil augmentation. The material appears to remain in place once the injection fluid is diluted into the surrounding groundwater. Overall, the technology is promising as a remediation method to treat dilute plumes or create diffuse permeable reactive barriers. Keys to future implementation include developing injection mechanisms that optimize soil distribution of the material and making the system long‐lasting to allow for continual treatment of contaminants emanating from the soil matrix. © 2011 Wiley Periodicals, Inc.     

Applications of mulch biowalls—three case studies

Mulch biowalls are proving to be an effective means of generating reducing conditions for the in situ anaerobic reduction of contaminants in groundwater that are amenable to the reduction process. Mulch is an inexpensive and readily available substrate that provides a long‐lasting carbon and electron donor source for the stimulation of the anaerobic reduction process in groundwater. Examples of contaminants that are amenable to the biotic anaerobic reduction process include: chlorinated alkenes and alkanes, explosives, perchlorate, some metals, and petroleum hydrocarbons. The microbial degradation of cellulose fibers (mulch) is arguably the oldest reduction process known and is evident anywhere that plant material, soil, and water are present together. This article presents three case studies discussing three different uses of mulch biowalls to stimulate the anaerobic bioremediation of contaminants in shallow soils and groundwater. © 2009 Wiley Periodicals, Inc.     

Managing residual contaminants—reuse and isolation case studies

Contaminants remaining onsite after regulatory‐approved environmental remediation operations are complete represent continued risk to human health and the environment. Many sites require continued management efforts to: (1) protect the integrity of the engineered remedy/control, (2) limit the exposure of individuals to residual contamination by limiting reuse activities, (3) maintain ready access to accurate records/information, and (4) protect against vulnerabilities from intentional threats/actions. This article presents performance information from selected case studies to provide insight into various management approaches employed for addressing the risks associated with residual contaminants. The case studies involve sites remediated within the U.S. Comprehensive Environmental Response, Compensation, and Liability Act framework and illustrate two prevailing management approaches for addressing the risks. Sacrifice zones are sites that are purposefully isolated to prevent human access onto the property. Reuse sites provide limited access for specific use. © 2008 Wiley Periodicals, Inc.