SUMMARY OF THE REMEDIATION TECHNOLOGIES DEVELOPMENT FORUM
PHYTOREMEDIATION OF ORGANICS ACTION TEAM
VEGETATIVE CAP SUBGROUP
CONFERENCE CALL

May 30, 1997

Members of the Phytoremediation of Organics Action Team, Vegetative Cap Subgroup, met in a conference call. The following members were present:

Tom Wong, Union Carbide Corporation (Subgroup leader)
Victoria Van Cappellen, NewFields, Inc.
David Carson, EPA/NRMRL
John Fletcher, University of Oklahoma
Greg Harvey, U.S. Air Force
Ray Hinchman, Argonne National Laboratory
Lucinda Jackson, Chevron
Steven Rock, EPA/NRMRL
Phil Sayre, EPA/TIO
Sunil Shah, Union Carbide Corporation

DEFINITION OF A VEGETATIVE CAP

The Subgroup discussed how it would define a vegetative cap; participants raised the following issues:

• Whether a vegetative cap should be described relative to hazardous or municipal waste

• What type of vegetation should be used for a cap

• Whether attempts should be made to keep animals out of capped areas

One participant added that a vegetative cap should be a healthy ecosystem; this comment raised the issue of what defines a healthy ecosystem, since natural ecosystems are known to produce toxins. Based on the discussion, the Subgroup came up with the following definition:

"A vegetative cap is a long-term, self-sustaining cover of plants growing in
and/or over materials that pose environmental risk; a vegetative cap reduces
that risk to an acceptable level and requires minimal maintenance."

Participants added that acceptable risk is typically achieved by limiting surface-water infiltration through the cap and/or using phytoremediation to reduce the toxicity of contaminated material.

PURPOSE

The objectives of the Vegetative Cap Subgroup are to:

• Demonstrate that a vegetative cap is an acceptable final cover

• Provide data on surface-water infiltration through a vegetative cap

• Provide data on toxicity reduction using phytoremediation

• Gain regulatory acceptance of vegetative caps

PROPOSED ACTION

Participants offered several suggestions on ways to help the Subgroup meet its goals. One participant suggested that the Subgroup find appropriate sites and monitor them. Participants agreed that there are many possible sites and specified three that might be of particular interest:

• A Union Carbide PAH site in Texas that has been vegetated for 15 to 20 years

• A Chevron petroleum site in California that may receive a vegetative cap

• An Air Force site in Tulsa, Oklahoma, where a vegetative cap is scheduled to undergo extensive monitoring

Participants agreed that while laboratory studies could provide some valuable information, obtaining field data should be a higher priority. One participant cautioned that a 3- to 5-year field test will probably only provide trends or indications, and that it may take 10 or more years to produce solid evidence of effective phytoremediation.

The Subgroup agreed to bring other organizations into the RTDF to facilitate the validation process by providing input and oversight. Participants suggested the Interstate Testing and Regulatory Commission, and state environmental agencies such as the Texas Natural Resources Conservation Commission (since Texas showed interest in the Ft. Worth Phytoremediation Workshop).

Participants agreed that tests need to be conducted on different types of plants (e.g., trees versus grasses) as well as different plant species (e.g., poplar trees versus oak trees), and that an array of chemicals should be tested. Participants agreed to leverage their existing knowledge by gathering and interpreting available data from sources such as AICHE, the U.S. Environmental Protection Agency (EPA), and various private corporations. One participant added that EPA is developing a Phytoremediation Handbook which could be a valuable source of information. Also, phytoremediation has been written into at least four Superfund Records of Decision (ROD) (i.e., using wetlands at an Army ammunition site in Iowa; using trees to intercept a TCE ground-water plume at Warren Air Force Base and a site in New Jersey; and using trees to intercept a PAH ground-water plume). Although this does not mean phytoremediation was accepted for these sites, the RODs may contain valuable information on phytoremediation.

NEXT STEPS

The RTDF is working to make its homepage available for information exchange and will tell Subgroup members how to use it once it is available. Steve Rock volunteered to collect information from participants to help move the Subgroup toward its goal and requested that people send him any information regarding:

• Vegetative cap projects

• Forensic ecology--sites that have been revegetated and for which data has been collected

• Monitoring systems--available monitoring data and suggestions on what should be monitored in the short- and long-term

The next conference call is scheduled for Thursday, June 26 at 10:00 a.m. CDT and will run for approximately 90 minutes. Wong will provide participants with an agenda prior to the call. The next Vegetative Cap Subgroup meeting will be part of the main RTDF meeting that is scheduled for late October in Cincinnati, Ohio. Wong will provide participants with more information on this meeting once a date is set.