Development and Application of a Multimedia Models to Assess Exposure to Persistent Organic Pollutants in South Texas
V. Uddameri, Texas A&M University Kingsville, Kingsville, TX Srilakshmi K. Ramaraju, Texas A&M University Kingsville, Kingsville, TX  

A New Method of Delineating Three-Dimensional Capture Zones with Models
John Glass, CH2M Hill, Herndon, VA 
Scott DeHainaut, CH2M HILL, Otis ANGB, MA
Rose Forbes, Air Force Center for Environmental Excellence, Otis ANGB, MA

Leaching of BTEX from Aged Crude Oil Contaminated Model Soils:  Experimental and Modeling Results
Michael H. Huesemann, Pacific Northwest National Laboratory, Sequim, WA
Tom S. Hausmann, and Tim J. Fortman, Pacific Northwest National Laboratory, Sequim, WA

Use of Brute Force Optimization Modeling for Design of Extraction Well Fields
Christopher Abate, AMEC Earth Environmental, Westford, MA

Contaminant Fate and Transport in the Courtroom 

Michael Sklash, Ph.D., P. Eng., Dragun Corporation, 30445 Northwestern Highway, Suite 260, Farmington Hills, MI 48334, Tel:  248-932-0228, Fax:  248-932-0618, Email:  Msklash@dragun.com
Charles M. Denton, Esq., Varnum, Riddering, Schmidt & Howlett LLP, Bridgewater Place, P.O. Box 352, Grand Rapids, MI  49501-0352, Tel:  616-336-6538, Fax:  616-336-7000, Email:  cmdenton@varnumlaw.com

Modeling of contaminant fate and transport in soils, groundwater, air and other environmental media can be a critical component of permitting, remedial action planning and design, site characterization, and source identification.  Modeling of emissions and contamination can result in significant cost-savings as compared with additional sampling and analysis, and is frequently utilized by potentially responsible parties as well as governmental agencies for air permitting, remedial investigations, corrective measures studies, and engineering design.  The science of modeling has been challenged in federal and state courtrooms across the country.  Questions have been raised as to the reliability, predictability and specificity of contaminant fate and transport modeling by various adversaries, including former operators, neighboring owners, and liability insurers.  This paper will discuss the scientific rigors of environmental modeling, its many uses and acceptability within the scientific community, as well as its limitations.  The paper will also review and discuss recent court rulings and evidentiary issues regarding contaminant fate and transport modeling in litigation and related expert witness testimony.  

Development and Application of a Multimedia Models to Assess Exposure to Persistent Organic Pollutants in South Texas

V. Uddameri, Department of Environmental and Civil Engineering, MSC 213, Texas A&M University-Kingsville, Kingsville, TX 78363, Tel: 361-593-2742, Fax: 361-593-2069, Email: vuddameri@tamuk.edu
Srilakshmi K. Ramaraju, Department of Environmental and Civil Engineering, MSC 213, Texas A&M University-Kingsville, Kingsville, TX 78363, Tel: 361-593-2742, Fax: 361-593-2069, Email: sramaraju@even.tamuk.edu

The region of South Texas along US-Mexico border is undergoing rapid growth in recent times.  Human health and ecological risks due to persistent organic pollutants (POPs) has been a critical issue in this region as several pesticides like DDT and others have been used extensively both on the US side (till their ban in 70s) and till very recently in Mexico.  The long-range transport potential of these pollutants, their recalcitrant nature and their ability to exist in multiple compartments simultaneously, requires a set of holistic assessment tools to quantify their exposure via multiple pathways and to various receptors.  The objective of this study was to develop a suite of mathematical modeling tools to estimate exposure concentrations in various compartments.  These models were developed in an iterative fashion starting with simple Level I type calculations and extended to more complex Level III/Level IV formulations.  A Geographic Information System (GIS) was used to assimilate data necessary to parameterize the model and visualize model results and disseminate risk-based information.  Fuzzy set theory was used to evaluate imprecision arising from model assumptions and lack of suitable data.  The presentation will discuss salient results obtained from this exposure assessment study and illustrate the utility of information technologies like GIS and fuzzy set theory in carrying out multimedia exposure assessments.       

A New Method of Delineating Three-Dimensional Capture Zones with Models

John Glass, CH2M Hill, 1321 Park Center Road, Suite 600, Herndon, VA 20171, Tel: 703-471-1441, Fax: 703-471-1508, Email: jglass@ch2m.com
Scott DeHainaut, CH2M HILL, 318 E. Inner Road, Otis ANGB, MA 02542, Tel: 508-968-4670 x5667, Fax: 508-968-4490, Email: sdehaina@ch2m.com
Rose Forbes, Air Force Center for Environmental Excellence, 322 E. Inner Road, Otis ANGB, MA 02542, Tel: 508-968-4670 x5613, Fax: 508-968-4673, Email: Rose.Forbes@mmr.brooks.af.mil

The Air Force Center for Environmental Excellence operates several groundwater remediation systems at the Massachusetts Military Reservation (MMR).  These systems involve multiple extraction and injection wells designed to provide complete or partial hydraulic containment of contaminant plumes.  It is important in the design and optimization of these systems to be able to accurately delineate their hydraulic capture zones, which are three-dimensional and irregularly shaped.  Traditional delineation techniques are based on visual identification of the envelope of pathlines leading to the extraction wells, the pathlines being generated by either backward or forward particle tracking in the simulated flow field.  A new technique being used at the MMR involves forward tracking of particles from a dense three-dimensional array of starting locations without actually plotting the pathlines.  Instead, the particle-tracking outcome is used to define a grid-based three-dimensional continuum of capture parameter, which can then be contoured in two-dimensional projections or otherwise rendered visible by three-dimensional visualization software.  The resulting capture parameter is a three-dimensional scalar field that can be considered a quantitative spatial property of the flow regime.  It can be combined with other scalar fields defined in the same grid, such as the concentration field, for visualization or for volumetric calculations.  Arithmetic comparisons of capture parameter arrays generated at different pumping rates are also useful in sensitivity analysis.

Leaching of BTEX from Aged Crude Oil Contaminated Model Soils:  Experimental and Modeling Results

Michael H. Huesemann, Ph.D., Pacific Northwest National Laboratory, Marine Sciences Laboratory, 1529 West Sequim Bay Road, Sequim, WA 98382, Tel: 360-681-3618, Fax: 360-681-3699, Email: michael.huesemann@pnl.gov
Tom S. Hausmann, and Tim J. Fortman, Pacific Northwest National Laboratory, Marine Sciences Laboratory, 1529 West Sequim Bay Road, Sequim, WA 98382

It is commonly assumed that soil properties such as organic matter content, porosity, and mineral surface area have a significant effect on the bioavailability and leachability of aged petroleum hydrocarbons. In order to test this hypothesis, nine model soils or sorbents (i.e., fine and coarse quartz sand, montmorrilonite and kaolinite clay, peat, 60Å and 150Å silica gel, a loam soil, and non-porous glass beads) were spiked with a crude oil at 50,000 mg/kg and 100,000 mg/kg, aged for 27 months in the laboratory, and transferred to glass columns for the performance of continuous flow leaching experiments. The column effluents were sampled and analyzed for BTEX until they were no longer detectable in the leachate. A one-dimensional flow model for predicting the dissolution and dispersion of individual hydrocarbons from a multi-component NAPL such as crude oil was developed and used to fit the leaching data (i.e., the BTEX concentration versus time curves) by adjusting the equilibrium oil-leachate partitioning coefficient (K_ol) for each respective hydrocarbon. The Peclet number, which is a measure of dispersion and a required modeling parameter, was measured in separate bromide tracer experiments for each soil column.

Results indicate that the BTEX leaching curves could be successfully fitted with the one-dimensional NAPL dissolution flow model for all sorbents with the exception of montmorrilonite clay and that the fitting parameter K_ol for each hydrocarbon is similar to the K_ol values that were independently measured for the same crude oil by Rixey et al. (Journal of Hazardous Materials B, 65: 137-156, 1999). In addition, the fitted K_ol values were very similar for BTEX leaching from aged compared to freshly spiked loam soil. These findings indicate that leaching of BTEX in the aged soils is not affected by soil properties or aging but rather is governed by the equilibrium dissolution of these hydrocarbons from the crude oil NAPL that is coating the soil particles.

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