SUMMARY OF THE REMEDIATION TECHNOLOGIES DEVELOPMENT FORUM
PHYTOREMEDIATION OF ORGANICS ACTION TEAM
TCE IN GROUND WATER SUBGROUP
CONFERENCE CALL

October 6, 1998
3:00 p.m.­4:00 p.m.

On October 6, 1998, the following members of the Phytoremediation of Organics Action Team, Trichloroethylene (TCE) in Ground Water Subgroup, met in a conference call:

Harry Compton, U.S. Environmental Protection Agency (EPA) (Subgroup Co-Chair)
Larry Erickson, Kansas State University (KSU)
Lee Newman, University of Washington School of Medicine
Paul Cichy, Center for Waste Reduction Technology (CWRT) at Rohm & Haas Company

Also present was Christine Hartnett of Eastern Research Group, Inc. (ERG).

PHYTOREMEDIATION HANDBOOK

Harry Compton noted that Steve Rock's staff has drafted a phytoremediation handbook. Compton said some Superfund regulators think the handbook's tone is too positive. Paul Cichy said the positive tone is not surprising, since the handbook was written to advocate phytoremedial technologies. Lee Newman noted the importance of a document's tone: if the tone is not positive enough, no one will use the technology. On the other hand, she continued, if the tone is too positive, the technology may be used in inappropriate situations and be doomed to fail. She said phytoremedial technologies have several limitations and these must be carefully and clearly identified so that people do not use the technology inappropriately. Exaggerating the benefits, she said, could cause some site owners to simply walk away from a site after planting trees. Doing so, she concluded, would ensure failure and would give the technology a bad reputation. Cichy said Newman's concerns are valid given what happened with bioremediation technologies. He said regulatory acceptance of bioremediation technology was hindered by reports of early failures. These failures were recorded, Cichy explained, at sites where uninformed salesman convinced site owners to use the technology.

Compton said Rock released a draft of the handbook in June 1998 and sent it to a select group of reviewers. He said he recently received a copy and that he plans to review it in the near future. Larry Erickson recommended having the entire TCE in Ground Water Subgroup review the handbook. Compton agreed this was a good idea and said he would arrange to have copies sent to Newman and Erickson. Newman asked Compton to send an E-mail summarizing which areas have generated controversy so that she and Erickson can focus their efforts on those sections. Compton said Rock plans to release a final copy of the handbook by the end of October 1998.

Erickson asked about the handbook's target audience and whether the handbook will have EPA's stamp of approval. Cichy said EPA project managers are targeted as the primary audience, but that the handbook will have a diverse and broad readership because it will be posted on the Internet. Compton said public EPA documents are usually subjected to a Scientific Advisory Board review, but he was not sure whether the handbook received such an extensive review. Erickson said the handbook could be released without the Board's review if it carried a disclaimer stating that EPA provided funds for the document but does not necessarily endorse the technology.

Cichy said CWRT plans to write a document that expands upon the handbook. Eight months ago, he continued, CWRT decided to write a paper on phytoremedial technologies. When they heard of Rock's efforts, however, CWRT postponed the initiation of this project. Cichy said CWRT does not want to duplicate Rock's efforts, so they have decided to pick their paper topics after the handbook is completed.

Compton said Superfund regulators voiced the most concern about the handbook's section on vegetative cap technologies: they thought optimism was premature, given that only a few demonstration projects have been installed and limited evidence is available proving that these caps prevent contaminant migration. Cichy stressed that the handbook's section on vegetative caps comprises only a small portion of the handbook. He said this section's tone could be easily adjusted or that additional caveats could be added to the beginning of the handbook. Either of these approaches, Cichy said, would likely appease the Superfund regulators.

Conference call participants talked briefly about the pros, cons, and status of vegetative caps. Compton said the Superfund program and some state programs (e.g., Maryland) require impermeable RCRA-style caps. While vegetative caps do not fall into that category, Compton continued, they could prove to be a useful technology. He and Newman noted that vegetative caps can achieve hydraulic control and remediate wastes via biodegradation. The latter, Erickson noted, does not occur with conventional RCRA-style impermeable caps and only occurs with a vegetative cap if roots are allowed to penetrate waste.

Erickson talked briefly about how vegetative caps achieve hydraulic control, noting that plants prevent infiltrating rainwater from migrating to underlying wastes via evapotranspiration processes. Compton said evapotranspiration rates decrease markedly during the dormant (nongrowing) season. Erickson agreed, noting that vegetative caps are most effective in areas where the dormant season is dry enough so that all rainwater accumulates within the root zone. Expanding on this point, Newman noted that vegetative caps should not be used as the sole means of hydraulic control in the Pacific Northwest because this region receives large quantities of rain during the dormant season. Cichy recommended installing a sheet-pile wall at sites with vegetative caps. He said the wall would divert ground-water flow away from contaminated areas and the trees would control infiltrating rainwater. Newman said this could be a useful approach at some sites and that the handbook should clearly delineate what types of sites are appropriate for specific remediation designs.

Conference call participants noted that one vegetative cap has been installed in Beaverton, Oregon. Several other caps, Newman added, have been installed by Lou Licht. Erickson and Newman did not think any vegetative caps have been installed at Superfund sites. In fact, Erickson continued, most have been installed at low-risk industrial sites.

AMHERST MEETING AGENDA

Newman noted that a soil and ground-water conference is planned for October 19­22, 1998, in Amherst, Massachusetts. Newman agreed to E-mail Compton a copy of the conference schedule. She noted that the Subgroup had talked previously about meeting informally during the conference. Compton said he did not know whether a large enough group could be gathered for the meeting. He agreed to contact Subgroup participants to determine who could attend. He started by taking a poll of the conference call participants. Newman said that she will attend and thought Steve Rock would also. Compton said he could attend if the meeting were held on October 22, but that Greg Harvey (the other Subgroup co-chair) would not be able to attend on any of the dates. Erickson said he would not be able to attend. Compton said Erickson and Harvey are important members of the group and recommended having them participate via conference call. Assuming the meeting occurs, Compton said he would work with the Technology Innovation Office (TIO) to set up the call.

Assuming the Subgroup does meet in Amherst, Compton said he would recommend using the time to draft answers to some of the questions that TIO has posed to the Subgroup. Some topics to be addressed are fate and transport of TCE, the depth to which phytoremediation is effective, and seasonal trends. For some of the questions, Harvey said, enough information is already available to formulate an answer.

SUBGROUP GOALS AND MISSION

Compton noted that TIO and Rock want the Subgroup to define a goal. Compton said other RTDF groups have initiated projects, but that the TCE in Ground Water Subgroup has served only as a forum for monthly updates on recent developments. Newman said the Subgroup needs to decide how to focus its efforts. She noted that there was significant debate on this topic during the last conference call. While some participants suggested focusing on the fate and metabolism of TCE, Newman reported, others recommended expanding the focus to include other compounds.

Newman said the Subgroup lacks funds. Compton said a sponsor could probably be identified if the Subgroup were to draft a project proposal. He asked what projects the Subgroup should pursue. During previous conference calls, Newman noted, participants had considered conducting a study that would evaluate the phytoremedial potential of different high-biomass plants. She recommended following up with this project. She said an ideal phytoremedial plant is one that grows rapidly, has high water uptake rates, and has efficient biodegradation capabilities. She said a list of high-biomass plants was included as an attachment to a previous conference call. She recommended reexamining this list and identifying those that are most effective at phytoremediation. The more plants that are identified, she noted, the more climatic regions can be considered for phytoremediation. To date, she explained, studies have focused almost exclusively on poplars. Although some investigators (e.g., Erickson) have started looking at willows and legumes, she continued, additional plants should be evaluated as well.

Cichy said he would recommend establishing evaluation protocols before selecting the plants for the evaluation. Newman said she and Compton talked about this during a previous conference call. They realize, Newman continued, that all evaluations must be performed using the same standards, tests, and protocols so that results can be compared across different investigators. Compton said he has generated a rough draft standard operating procedure (SOP) for measuring transpiration gas. He said he will make the SOP available once it is finalized.

Compton agreed that a study evaluating different plants could be useful. He said it might dovetail nicely with a project being conducted by the University of Washington's Chuck Henry. Compton said that Henry's team's main mission is to identify native plants that can be planted on Superfund sites. Compton said Henry is searching for plants that are fast-growing and tolerant of highly contaminated soils.

Erickson said he would advise conducting a project to determine what happens to chlorinated solvents in the atmosphere. He noted that some regulators are concerned that phytoremedial technologies simply transfer contaminants from the subsurface to the air by drawing contaminants through their roots and releasing them through their leaves. Erickson and Compton noted that some data has already been collected on contaminant release to the environment. They both agreed that the data show that very little TCE is released from poplars. Compton said the data he has seen indicates that TCE concentrations are only detectable at the microscale level. Erickson noted that KSU has drafted a manuscript that discusses TCE release issues. The text, he said, is in press with Environmental Progress and concludes that (1) only small quantities of TCE are released to the atmosphere and (2) atmospheric TCE degrades within a matter of days. Erickson said TCE's breakdown products are innocuous when present in the atmosphere. In general, Erickson continued, releases to the atmosphere should not be a problem if the released contaminants have a short half-life.

NEXT CONFERENCE CALL

Compton recommended establishing the date for the next conference call via E-mail. Newman said she has faculty meetings on one Tuesday afternoon per month. She asked if calls could be scheduled around these meetings. She said if Tuesdays are better for other members, she could still attend the conference calls if they are held earlier in the day. Erickson said Mondays are the only inconvenient day for him.

MISCELLANEOUS

Newman noted that James Duffy accepted an early retirement package from Occidental Chemical Corporation. She said Duffy has received offers from several other firms, but that he is taking some vacation time before deciding what to do next. She noted that he has been a fantastic supporter of phytoremedial technologies and the Subgroup owes much of its progress to him.

Conference call participants agreed to wait until their next conference call to review the August 10, 1998, conference call summary.