Site Assessment and Characterization - Introduction to Phytoremediation of Contaminated Groundwater - page 150

along which are placed a transmitter of electromagnetic
waves and a receiver some distance away. Reflection of the
transmitted energy as it impinges on various subsurface
contacts is what is received and plotted. The data presented
by Hruska et al. (1999) indicated that the GPR provided
resolution of roots between 1.1 and 1.5 in. (3-4 cm) in dia-
meter. Although these trees had massive lateral root systems
that were entirely dependent on capture of precipitation
because the bedrock precluded the formation of an unconsoli-
dated water table, the application of GPR to sites where
phytoremediation is applied warrants further investigation.

plant(s) selected for phytoremediation. Moreover, to achieve
containment of groundwater, the rate of groundwater flow
must equal the rate of plant uptake of water to keep the
contaminated groundwater from flowing past the plants. In
some cases, the USEPA document states that success can be
had at such sites if trees are initially deeply planted to be as
close to the water table as possible, such as through use of
methods similar to the patented Tree-well ® method reported
in Gatliff (1994).
The application of vegetated covers to affect site hydrol-
ogy is discussed thoroughly. The USEPA document outlines
a list of decision-making processes that, if followed, will
lead to the recommendation or refusal of the application of
phytoremediation at a specific site (Table 6.3 ).
The USEPA Brownfields document (U.S. Environmental
Protection Agency 2001) provides introductory material on
the potential application of phytoremediation at sites
designated as Brownfields sites, which are abandoned, idle,
or under used, and have long histories of commercial or
industrial practices but also are located in areas undergoing
revitalization. In many cases, the federal regulators involved
at such sites encourage the use of innovative technologies,
such as phytoremediation. The document describes a
strategy to control contaminated groundwater flow by
surrounding a contaminant plume with plants and thereby
creating a hydrostatic barrier of tree roots so that groundwa-
ter is captured by the roots and does not flow past them.

6.6 Available Phytoremediation Site-

Assessment and Characterization
Documents

Currently, a few public documents are available that outline
various approaches, or protocols, regarding the assessment,
characterization, implementation, and monitoring of
phytoremediation. In general, these documents focus to a
greater extent on the phytoremediation of soil and sediments
relative to groundwater. The documents discussed in this
section are grouped according to the major agency
associated with the protocol and the summaries presented
here are not meant to be comprehensive.

6.6.1 U.S. Environmental Protection Agency
(USEPA) 6.6.2 Interstate Technology & Regulatory

Council (ITRC)

As one of the original proponents of the assessment of
phytoremediation in restoring contaminated environments,
the USEPA has produced many documents on the subject of
phytoremediation. The two discussed here are (1) Introduc-
tion to Phytoremediation (U.S. Environmental Protection
Agency 2000a), and (2) Brownfields Technology Primer:
Selecting and Using Phytoremediation for Site Cleanup
(U.S. Environmental Protection Agency 2001).
The Introduction to Phytoremediation (U.S. Environmen-
tal Protection Agency 2000a) is indeed that, an introduction.
Topics range from an overview of the technical, economic
and regulatory aspects of phytoremediation, to the evalua-
tion of the different plant-based technologies that compose
phytoremediation processes, to design criteria, and to per-
formance evaluation. Case studies also are provided. Per-
haps because of the general nature of the document and
because nine different phytotechnologies are covered, the
information provided on the application of phytoremediation
to hydrologic control by the reduction of off-site flow is
limited to two pages. The document rightly states that for
plants to control site hydrology, the depth to water table
cannot exceed the maximum rooting depth of the particular

Because of the typically lower installation cost of
phytoremediation relative to conventional pump-and-treat
methods to control groundwater, the potential arises that
phytoremediation may be selected as a remedial option
when, in fact, site data do not support implementation. To
help determine if phytoremediation can or cannot be applied
at a site, a decision tool was developed by members of the
Interstate Technology & Regulatory Council (ITRC). The
ITRC is a coalition of state, federal, public, and industrial
representatives with shared interest and expertise in reme-
dial technologies and activities. The goal of ITRC is to
advance innovative remedial strategies that are cost

effective.
The ITRC developed a protocol similar to that of the
USEPA discussed previously that assists in the decision-
making process (Interstate Technology and Regulatory
Council 1999) and has been revised (Interstate Technology
Regulatory Council ITRC 2009). The decision-making tool
is built on a flowchart framework, where data collected
sequentially are used to answer questions regarding the use
of phytoremediation at a particular site (Fig. 6.8 ).