Choosing the Best Design and Construction Technologies for Permeable Reactive Barriers - Permeable Reactive Barrier: Sustainable Groundwater Remediation - page 43

addressed at the design stage (Gavaskar et al. 2002). This chapter reviews the
design and construction technologies for PRB, with particular emphasis on
their application for remediation of CHC-contaminated GW. It aims to identify
key issues that need to be addressed to increase the performance and longev-
ity of PRB systems. While the chapter focuses on CHC and the use of zero-
valent iron (ZVI), the parameters optimized for the design of PRBs are the
same irrespective of the contaminant and material used as the reactive barrier.
3.2 PRB Engineering Design Methodology
Engineering design of PRBs comprises the selection of the most suitable
barrier configuration, appropriate reactive medium, the size of the barrier,
barrier construction technology, quality control of the barrier, and performance-
monitoring GW well installation. The design needs to be tailored to provide
a site-specific solution to meet the GW remediation objectives. A detailed
knowledge of the site hydrogeology (e.g., an understanding of aquifer and
aquitard), geochemistry (e.g., GW chemistry other than for the chemical of
concern), and chemistry of contaminants (e.g., source, composition, and con-
centrations) is required for successful PRB design (Roehl et al. 2005). The site
information required includes: activities near the proposed barrier; existing
utilities lines and other obstructions; site soil quality; construction method-
ology and contractor's expertise in the area; and knowledge of the costs of
reactive material.
3.2.1 Selection of Reactive Material
Following a detailed site characterization of the plume and GW information,
a suitable type of design can be chosen to capture the plume and remediate
it to meet the site remediation objectives—within a budget. The selection cri-
teria for reactive media should incorporate (Gavaskar et al. 2000; ITRC 2011;
Richardson and Nicklow 2002)
• Reactivity. Sufficient reactivity for an economical and practical bar-
rier thickness.
• Stability. The ability to remain reactive for several years to decades
under the site-specific geochemical and microbial conditions, with a
minimal amount of maintenance.
• Availability and Cost. A cheaper medium is preferred especially if any
differences in performance are reported to be slight.
• Hydraulic Performance. A practical size sufficiently greater than that
of the aquifer material so that an effective capture zone can be cre-
ated and maintained.