Site Assessment and Characterization - Introduction to Phytoremediation of Contaminated Groundwater - page 153

as a feasibility study in the field or laboratory; an operation
and maintenance plan; a monitoring strategy; and a contin-
gency plan.

results of modeling the site water balance with the addition
of plants are promising. The protocol emphasizes the impor-
tance of using computer models to help define the water
balance in order to determine if a potential phytoremediation
system will affect the water budget. The primary simulation
objective is to determine if the plant removal of groundwater
will be at a rate fast enough to create a water-table depres-
sion to alter groundwater contaminant transport. Perhaps the
best rationale for using models is to determine the time to
reach such conditions where, at a minimum, the rate of
groundwater flow equals the rate of uptake by plants.
One approach offered in the RTDF document (Remedia-
tion Technologies Development Forum 2005) is to perform
groundwater capture-zone modeling. A capture zone is a
delineation of the source of groundwater being pumped
from a well. Capture-zone analysis usually is conducted by
water managers to understand the source of water pumped
by drinking-water supply wells and to determine if potential
sources of contamination are located in the capture zones
of these wells (see Landmeyer 1994 for an example).
For phytoremediation purposes, pumping wells rather than
transpiring trees are simulated.

6.6.3 Remediation Technologies Development
Forum (RTDF)

The Remediation Technologies Development Forum
(RTDF) represents collaboration between the USEPA, Office
of Research and Development and Technology Innovation
Office, and public and private sectors. Established in 1992, its
goal is to mutually seek innovative solutions to the growing
problem of hazardous wastes in the United States. Moreover,
to assist in widespread implementation, the solutions have to
be cost effective. Funding for the RTDF is provided by the
USEPA, with additional support by technology customers
and other federal agencies, such as the Department of
Defense (DOD) and Department of Energy (DOE). Addi-
tional funds are contributed by private concerns.
Because of the wide range of contaminants and clean-up
strategies, the RTDF is divided into different action teams.
The Phytoremediation of Organics action team produced a
report that describes the development of a field protocol for
determining the efficiency of certain plants in degrading
various groundwater and soil contaminants (Remediation
Technologies Development Forum 2005; Fig. 6.9 ). Little is
said in the report regarding the hydrologic control of ground-
water by plants. However, the team also has produced a large
bibliography that contains many relevant articles on
phytoremediation, and some address the issue of hydrologic
control by plants.
Although the main focus of the report by RTDF (Reme-
diation Technologies Development Forum 2005) is to pres-
ent the application of phytoremediation for the remediation
of chlorinated solvents at contaminated sites, the document
acknowledges the importance of assessing the hydrogeology
of a site and its influence on the extent of remediation of
contaminants. The document states that certain trees can
extract groundwater and depress the water table, which
causes groundwater to flow to these trees. As a result of the
change in groundwater flow, the risk of off-site migration of
contaminants, in this case chlorinated solvents, is decreased.
As part of a protocol displayed in the document and
reproduced with modifications in Fig. 6.9 , one of the initial
questions in the flowchart is whether the plant roots can meet
the requirement for depth to water table and whether the

6.7 Summary

A thorough review of the history and pre-existing data at
sites is warranted to determine if phytoremediation is appli-
cable and can be successful to remediate contaminated
groundwater. Thankfully, a growing body of information
exists regarding how to conduct, in a methodical and logical
manner, site assessments and characterization to determine
if conventional remedial practices or phytoremediation
can be used. However, these guidelines and protocols often
are limited in not being able to address site-specific
concerns. Moreover, the protocols often omit the use of
phytoremediation to achieve goals of hydrologic contain-
ment or control.
Why is this information important to the phytore-
mediation of contaminated groundwater? The time
invested using conventional site-assessment and characteri-
zation approaches will either be returned in the form of a
successful phytoremediation system and, therefore, a suc-
cessful phytoremediation project, or in the knowledge that
an alternative remedial strategy can be used if phytore-
mediation cannot be supported.