SUMMARY OF THE REMEDIATION TECHNOLOGIES DEVELOPMENT FORUM
PHYTOREMEDIATION ACTION TEAM
CHLORINATED SOLVENTS SUBGROUP
CONFERENCE CALL

September 14, 2000
1:30 p.m.-3:00 p.m.

On September 14, 2000, the following members of the Remediation Technologies Development Forum's (RTDF's) Phytoremediation Action Team, Chlorinated Solvents Subgroup, met in a conference call:

Bob Tossell, GeoSyntec Consultants (Subgroup Co-chair)
Keith Rose, U.S. Environmental Protection Agency (EPA) (Subgroup Co-chair)
Steve Rock, EPA
Jim Jordahl, CH2M Hill, Inc.
Steve McCutcheon, EPA

Review and General Discussion

Call participants received a new version of the Subgroup's Protocol on September 13. Bob Tossell had integrated comments from Jim Jordahl and Keith Rose into this draft. The biggest changes he made were to move the microbial discussion to an appendix and add a table (Table 1) and a figure (Figure 1). Call participants were happy with the outline, structure, and organization of the new version. Jordahl complimented Tossell on his hard work.

Steve Rock agreed with Jordahl's instruction to keep the focus on chlorinated solvents and not mention inorganics in Section 2.0, Background. Rock also suggested removing the second paragraph in Section 2.0. Tossell said that certain passages need to be finished, but as long as the major points are discussed, minor edits can be incorporated later in the process.

So far, Lee Newman and Milton Gordon have been in charge of writing Section 2.3.6, Plant Attenuation. Call participants assume that they are still working on this section, though no one has been able to contact Newman or Gordon lately. Tossell would like to have Section 2.3.6 ready for the next version of the Protocol. Rock will request a copy of the Technology Innovation Office (TIO) literature search and will ask TIO to send Tossell a copy.

Figure 1 is a standard figure that shows what can occur when there is a dense nonaqueous-phase liquid (DNAPL) in the subsurface (i.e., DNAPL is governed more by gravity than by flow in its free phase, but it does have a soluble component, which creates a plume.) Rock likes the figure, because it could be used to show how plants can be used to remediate two phases (i.e., plants do remediate the dissolved and residual phases, but do not remediate free product).

Tossell would like to incorporate the idea of the conceptual model into Section 3, Phytoremediation Approaches. His idea is to modify Figure 1 to show how phytoremediation in different applications can apply to management of sites with free-phase, dissolved-phase, and (for indoor air issues) gaseous-phase material. Call participants agreed that a conceptual model, like the ITRC Decision Tree, will help people decide if phytoremediation is appropriate for their site.

The ITRC Decision Tree will be incorporated into Section 4 and modified for specific discussions. Its original form is useful as a general screening-level assessment; however, when more detail is needed, a more specific version of the Decision Tree will help answer specific questions.

Tossell reviewed the status of the Action Items from the previous conference call. These included the following:

• Rock sent an earlier version of the Protocol to Steve McCutcheon.



• Tossell added a brief discussion of chlorinated solvents in soil to the draft. He wrote that unsaturated soil is a conduit for chlorinated solvents that are discharged to the surface because they have migrated to saturated zones. When this happens, a dissolved plume develops in the saturated zones and residual contamination is left in the soil. Tossell also mentioned that plants have difficulty remediating contamination in the saturated zones, but can be used to attenuate contamination in the dissolved phase. Tossell's discussion also mentions microbial processes.



• Lee Newman and Milton Gordon have not been able to write Section 2.3.6, Plant Attenuation, yet. If they cannot write this section for the next conference call, Tossell will try to draft the section.



• Tossell shortened the microbial section to a few short paragraphs and moved the remainder of the text to an appendix. Tossell noted that it would be great if our understanding of phytoremediation treatment processes was as well defined as they are for bioremediation.



• Section 3.0 still needs examples of how the treatment chain would work.



• Tossell explained the limitation of deep ground-water planting and control. Jordahl agreed to add to the section.



• Tossell e-mailed Bob Mueller, informing him that the Subgroup was incorporating the ITRC Decision Tree into their Protocol. Rock mentioned to Tossell that the ITRC Decision Tree can be found at ITRC's Web site, www.itrcweb.org.



• Tossell outlined Section 4.0, Phytoremediation Evaluation. Conference call participants agreed that it was a good idea to use figures and tables and link the discussion with the Decision Tree (i.e., boxes on flow charts). Section 4.0 will be designed to provide enough information to site managers to help them decide if phytoremediation is a feasible option at their sites.
  

Tossell had mentioned patents briefly in section 3.1.4.1. Call participants discussed various patents, saying that most are being challenged in court. McCutcheon warned that some site managers may not use phytoremediation because they believe that proprietary patents/technology may be too expensive or that it may be too difficult to use someone else's technology. Call participants talked about where in the Protocol, and in how much detail, patents should be discussed. Rock suggested adding a new section, Section 3.1.4.2, that would discuss patents. Tossell agreed to write this section. Rock offered to send Tossell the patent numbers.

Tossell asked call participants what they thought about Section 4.3, Research Evaluations. Previously, Newman and Gordon volunteered to discuss what "research" entails. Tossell suggested that the text (1) describe the needs and benefits of further science through applied research and (2) discuss how research can help site managers understand solvent fate at their sites. Rock suggested the text identify further research that is needed. Jordahl suggested a general discussion that tells site managers that they might want to fund specific research to help them evaluate phytoremediation at their sites (i.e., a recommendation like "if you do this you'll know exactly what process is suited to your site."). Keith Rose suggested avoiding the term "research" by saying "technology development."

Next Steps

Tossell agreed to draft Section 4.1, Screening Level Assessments, and send a new draft to Subgroup members via e-mail by October 19. He also agreed to revise Sections 1, 2, and 3 of the document.

Jordahl agreed to further explain the limitations of deep ground-water planting and control in Section 3.1.4.1.

Schedule

Previously, call participants had decided that the Subgroup's Protocol should be written by November. Tossell said that November is no longer realistic. McCutcheon suggested setting a solid target to keep the Subgroup on track. Jordahl suggested setting interim goals. The call participants agreed that Section 4.1, Screening Level Assessments, should be completed by the next Subgroup conference call and that Section 4.2, Detailed Evaluation, should be ready for the Subgroup's November conference call. Call participants agreed that January is a good deadline for getting the document completely written and internally edited before sending it out for review. The goal for having a finished document is now early 2001, possibly February or March.

ADDITIONAL BUSINESS

• McCutcheon and Jerry Schnoor are writing a companion volume to Phytoremediation of Toxic Metals by Raskin and Ensley. It will consist of 34 chapters (three chapters will directly address chlorinated solvents) and will cover the latest advances in the field. Some of the topics are as follows:

• A chapter, written by Peter Jeffers, that will investigate phytoremediation of airborne contaminants and chlorinated solvents, including the uptake of methyl bromide, trichloroethylene, and tetrachloroethylene through air and into the stomata, where breakdown products are found.



• A section on chlorinated solvents that will address reductive and oxidative pathways in vegetative systems.

• A chapter by Bill Doucette on natural attenuation of chlorinated solvents by trees and microbes.



• A chapter on ground-water evapotranspiration to control plumes.



• Chapters that present two case studies (Carswell and Aberdeen) to demonstrate successful degradation by trees and microbes.



• A chapter by Stacy Hutchinson, about using localized modeling to determine how to design a site to control surface runoff, recharge, and evapotranspiration.

McCutcheon can provide a list of chapters to the Subgroup members if anyone is interested in reviewing a chapter. Tossell agreed to be one of the outside reviewers.

• Rock said that he is currently very busy with field work, and is reviewing proposals involving various technologies. For example, in Delaware City, site managers are using phytoremediation at a waste pond to control infiltration and remediate waste.

• McCutcheon mentioned that a new society, Ecological Engineers, is accepting charter members until September 30. Anyone interested should contact McCutcheon; he will mail background information about the society. Bill Mitch (editor) and Mark Brown established the society to allow affordable subscription rates for the journal Ecological Engineering. It is also an opportunity for people in applied ecology who are taking an engineering approach to get together every one or two years. Rock asked about McCutcheon's involvement. McCutcheon is helping put together the first meeting for next spring in Atlanta and has volunteered for a leadership position. Tossell expressed interest.

ACTION ITEMS

• Bob Tossell agreed to continue to revise the Protocol and send a revised draft via e-mail to the other committee members by October 19. The revision will include the following:

• --Removing the second paragraph of Section 2.0, Background.

• --Writing Section 2.3.6, Plant Attenuation, if Lee Newman and/or Milton Gordon cannot.

• --Drafting a new section (3.1.4.2, Patents) that will review the current patents.

• --Finding an electronic copy of ITRC's Decision Tree on their Web site, www.itrcweb.org.

• --Writing Section 4.1, Screening Level Assessments.

• Steve Rock agreed to provide patent numbers to Tossell for inclusion in the Protocol's next draft.



• Rock agreed to ask TIO to send Tossell a copy of their literature search.
  

• Jim Jordahl agreed to further explain the limitations of deep ground-water planting and control (Section 3.1.4.1).



• ERG agreed to set the next conference call for Thursday, October 26, 2000, at 1:30 p.m. Eastern Daylight Time.