On Wednesday, May 7, 2003, the following members of the Remediation Technologies Development Forum’s (RTDF’s) Permeable Reactive Barriers (PRB) Action Team met in a conference call:
Bob Puls, U.S. Environmental Protection Agency (EPA) (Action Team Co-chair)
John Vidumsky, DuPont (Action Team Co-chair)
Liyuan Liang, Cardiff University, Wales
Stan Morrison, U.S. Department of Energy
Tom Krug, GeoSyntec
Stephen White, U.S. Army Corps of Engineers
Also participating in the call was Christine Hartnett from ERG.
Bob Puls and John Vidumsky held this conference call to discuss upcoming PRB Action Team activities. They identified two issues that required immediate attention: planning a meeting and updating the PRB Action Team Web site.
Call participants decided to hold a PRB Action Team meeting in fall 2003. They agreed that the last Action Team meeting—held in conjunction with an Interstate Technology and Regulatory Council (ITRC) conference in November 2002—was well received and attracted many attendees. Therefore, they decided that it would be beneficial to collaborate with ITRC again. John Vidumsky will pursue this avenue; he will ask Matt Turner whether the PRB Action Team can be coordinated with the ITRC fall 2003 conference, which is scheduled to take place in Monterey, California, on September 29 through October 2, 2003. If this option is chosen, Puls said, efforts will be made to integrate the ITRC and PRB Action Team sessions.
Call participants identified the following as topics that could be included on the meeting agenda:
Hydraulic effects. DuPont has observed interesting vertical flow patterns at one PRB site, Vidumsky said, noting that water from the site’s upper unit is flowing downward into a lower unit.
Corrosion products. Stan Morrison said that studies are being performed to evaluate carbonate and uranium precipitate formation and the way these precipitates impact water flow. Puls said that EPA is performing studies on corrosion products and has found that some of the products (e.g., green rust and iron sulfide) are highly reactive. This finding conflicts with conventional thinking, which holds to the idea that PRB reactivity declines in a mathematical fashion over time. Puls said that some of EPA’s work also suggests that the corrosion products exist in natural systems. This has caused some researchers to ask whether these abiotic products play a role in natural attenuation. Vidumsky said that he also knows some researchers who are exploring the role that precipitates might play in spurring abiotic degradation activities.
Emulsified nanoscale iron. Krug said that GeoSyntec is working with NASA to assess the remedial potential of emulsified nanoscale iron.
Assessing different iron sources. Stephen White said that a researcher at Clemson University is comparing the reactivity of iron that is sold by different suppliers. Krug said that researchers at the University of Toronto have found that the dominant pathway of contaminant degradation differs across different iron sources. Vidumsky said that researchers at the University of Delaware are also trying to determine whether iron from different sources differs in reactivity.
Arsenic remediation. Vidumsky said that DuPont is using a PRB to remediate arsenic.
Chlorofluorocarbon (CFC) remediation. DuPont has performed some column studies, Vidumsky said, to determine whether CFCs can be remediated with zero valent iron (ZVI).
Vanadium remediation. Morrison said that a study has been performed to determine whether ZVI can be used to remediate vanadium.
TNT and RDX remediation. Krug and Stephen White both knew of studies that have been performed to examine PRBs’ ability to treat explosive compounds. At one site, Krug said, bioremedial techniques are being used with the PRB as part of a treatment train.
Addressing high pH. At one site, Krug said, carbon dioxide is being bubbled into a gravel-filled trench to address high-pH water. (The water was contaminated by a cement kiln dust pile.)
The Action Team’s Web site needs to be updated, Puls said. Three areas require attention: the site profiles, the list of involved participants, and the section that lists technical documents and useful links. Puls asked Steering Committee members to review these sections and submit comments to him. He will consolidate the comments and work with the webmaster to make the necessary changes.
The PRB Action Team will hold a meeting in fall 2003. Toward this end:
Vidumsky will ask Turner whether the PRB Action Team meeting can be coordinated with the ITRC meeting that is scheduled to take place in Monterey, California, on September 29 through October 2, 2003.
Puls and Vidumsky will think about ways to integrate the ITRC and PRB Action Team sessions.
Steering Committee members will identify topics for the meeting agenda and will be prepared to discuss their ideas during the next PRB Steering Committee conference call.
ERG will set up the next PRB Action Team meeting for May 14, 2003, between 11:00 a.m. and 12:30 p.m. Eastern Daylight Time.
Steering Committee members will visit the PRB Action Team’s Web site and examine the site profiles, the list of involved participants, and the section that lists technical documents and useful links. They will send Puls recommendations on how to update the Web site.