IDC J E strategic Environmental Re scarce
L J	ano Da\/»liprnent Program

SERDP Impacts of DNAPL Source Zone	RestoratToT3'

Treatment: Experimental and	ER-1295

Modeling Assessment of Benefits
of Partial Source Removal

Background:

At the nearly 17,000 sites on Department of Defense
installations potentially requiring environmental cleanup,
there is a need for innovative source-zone treatment
technologies that offer cost-effective risk reduction.
Unfortunately, there is currently no consensus in the
academic, technical and regulatory communities on the
ecological or environmental impacts of dense non-aqueous
phase liquid (DNAPL) source-zone treatment. The cost of
source-zone treatment is high, and the anticipated benefits
need to be understood before significant resources are
committed to source-zone removal. Since it is not
economically practical to remove all DNAPL mass from
most source zones, the focus of this project is on the likely
benefits from partial DNAPL mass removal using some
aggressive in-situ technology (e.g., alcohol or surfactant
flushing; steam flooding; air sparging; chemical
oxidation).

Objective:

The primary objective of this project is to develop a
scientifically defensible approach for assessing the long-
term environmental impacts (i.e., benefits) of DNAPL
removal from source zones. The fundamental premise is
that contaminant flux from the source should be used as
the basis for evaluating the effectiveness of remediation.

Process/Technology Description:

An integrated approach, comprised of laboratory
experiments, field observations and numerical simulations,
will be used. To evaluate the functional relationships
between DNAPL mass reduction, contaminant mass flux
and plume behavior, data from selected DNAPL source-
zone remediation field tests will be used to demonstrate
the ability of selected numerical simulators to realistically
forecast the performance of remedial activities. Codes
such as T2VOC and UTCHEM will be used to simulate
remediation processes during steam, surfactant, or
cosolvent flooding and to predict the temporal and spatial
distribution of contaminant flux leaving the source zone.
Laboratory studies will be conducted to supplement
existing field data and to further assess the relationship
between mass removal and resultant contaminant flux for
abroad range ofhydrogeological conditions. Contaminant
flux distributions will be used as input to dissolved-plume
models to forecast the natural or enhanced attenuation

expected within the plume. Plume transport simulations
will be carried out using codes that simulate aqueous-
phase transport explicitly coupled with important
geochemical and biological reactions. Currently, there is
no numerical code that is capable of modeling fully
coupled enhanced DNAPL remediation by thermal and
chemical flooding methods with biogeochemical reactions
that occur in dissolved aqueous phase DNAPL
components. Coupling these two types of modeling
approaches at the DNAPL source-zone/ dissolved-plume
interface is a new approach that is computationally
efficientbras and that incorporates the dominant physical,
chemical and biological features in each region.

	Control Plane	Compliance Plane	

Hypothetical DNAPL Source and Dissolved Plume.

Expected Benefits:

This project will develop sufficient understanding of the
linkage between source-zone remediation and its impacts
on dissolved plume behavior to permit optimization of the
remedial process by balancing mass removal with plume
attenuation. The experimental data and modeling analyses
will provide a basis for developing appropriate flux-based
remediation endpoints at DNAPL sites and will help in the
design of cost-effective remediation technologies. Thus,
project results will facilitate more comprehensive risk
assessments and provide a scientific basis for developing
regulatory and policy guidelines for DNAPL source-zone
remediation. (Anticipated Project Completion - 2008)

Contact Information:

Dr. A. Lynn Wood

U.S. Environmental Protection Agency

National Risk Management Research Laboratory

919 Kerr Research Drive, P.O. Box 1198

Ada, OK 74820

Phone: (580) 436-8552

Fax: (580) 436-8703

E-mail: wood.lynn@epa.gov

REVISED 10/16/07


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