Tarawa

Terrace

Camp

Johnson

Camp Lejeune

Military Reservation

Holcomb

Boulevard

Hadnot

Point

Marine Corps

Air Station

Stone

Bay

Rifle

Range Courthouse

Bay

Onslow

Beach

Jacksonville

Atlantic Ocean

New River

Edited by

Prepared for:

Prepared by:

Morris L. Maslia

Agency for

Toxic Substances and

Disease Registry,

Atlanta, Georgia

Eastern Research

Group, Inc.,

Atlanta, Georgia

Expert Peer Review Panel Evaluating ATSDR’s

Water-Modeling Activities in Support of the Current

Study of Childhood Birth Defects and Cancer at

U.S. Marine Corps Base Camp Lejeune, North Carolina

Analyses of Groundwater Resources and

Present-Day (2004) Water-Distribution Systems,

March 28-29, 2005
Back of Cover (blank page)
Expert Peer Review Panel Evaluating ATSDR’s 

Water-Modeling Activities in Support of the 

Current Study of Childhood Birth Defects and 

Cancer at U.S. Marine Corps Base Camp Lejeune, 

North Carolina

Analyses of Groundwater Resources and Present-Day (2004) 

Water-Distribution Systems, March 28–29, 2005

Morris L. Maslia, Editor

Prepared for:

Agency for Toxic Substances and Disease Registry

Atlanta, Georgia

Prepared by:

Eastern Research Group, Inc.

Atlanta, Georgia

October 2005
Suggested Citation for this Report:

Maslia, M.L., editor, 2005, Expert Peer Review Panel Evaluating ATSDR’s Water-Modeling Activities 

in Support of the Current Study of Childhood Birth Defects and Cancer at U.S. Marine Corps Base 

Camp Lejeune, North Carolina—Analyses of Groundwater Resources and Present-Day (2004) WaterDistribution Systems, March 28-29, 2005: Prepared by Eastern Research Group, Inc., Atlanta, Georgia; 

Prepared for Agency for Toxic Substances and Disease Registry (ATSDR), Atlanta, 31 p., 4 app.
Contents

Executive Summary------------------------------------------------------------------------------------------------------- 1

1.0 Introduction ----------------------------------------------------------------------------------------------------------- 3

1.1 Background ----------------------------------------------------------------------------------------------------- 3

1.2 Meeting Organization------------------------------------------------------------------------------------------ 6

2.0 ATSDR Objectives and Goals---------------------------------------------------------------------------------------- 7

2.1 Welcoming and Opening Remarks --------------------------------------------------------------------------- 7

2.2 Statement by the Chair ---------------------------------------------------------------------------------------- 7

2.3 Summary of ATSDR Activities -------------------------------------------------------------------------------- 7

3.0 Summary of Water-Modeling Activities --------------------------------------------------------------------------- 8

3.1 General Overview ----------------------------------------------------------------------------------------------- 8

3.1.1 Overview of Water-Modeling Systems and Activities----------------------------------------------- 8

3.1.2 Brief Overview of Groundwater Analyses ------------------------------------------------------------ 9

3.2 Groundwater-Modeling Analyses ----------------------------------------------------------------------------- 9

3.2.1 Geohydrologic Framework ----------------------------------------------------------------------------- 9

3.2.2 PCE Contamination at Tarawa Terrace and Vicinity ------------------------------------------------ 10

3.2.3 Groundwater-Flow Model at Tarawa Terrace and Vicinity ---------------------------------------- 11

3.3 Analyses of Water-Distribution Systems -------------------------------------------------------------------- 14

3.3.1 Approach to Analyses of Water-Distribution Systems --------------------------------------------- 14

3.3.2 Analyses of Present-Day Water-Distribution Systems--------------------------------------------- 14

4.0 Panel Discussions--------------------------------------------------------------------------------------------------- 17

4.1 ATSDR Response to Premeeting Comments ---------------------------------------------------------------- 17

4.2 Panel Discussions and Recommendations------------------------------------------------------------------ 18

4.2.1 General Questions on the Epidemiologic Study----------------------------------------------------- 18

4.2.2 Lack of Historical Data--------------------------------------------------------------------------------- 18

4.2.3 Addressing Uncertainty and Variability -------------------------------------------------------------- 19

4.2.4 Suggested Modeling Approaches, Modifications, and Considerations ------------------------- 21

4.2.5 Parameter Estimation ---------------------------------------------------------------------------------- 23

4.2.6 Groundwater-Recharge Data ------------------------------------------------------------------------- 23

4.2.7 Project Schedule --------------------------------------------------------------------------------------- 23

4.2.8 Field Testing --------------------------------------------------------------------------------------------- 24

5.0 Discussions and Responses to Questions from the Public----------------------------------------------------- 25

6.0 Summary of Recommendations from Panel Members and ATSDR’s Response ------------------------------- 29

6.1 Data Discovery ------------------------------------------------------------------------------------------------- 29

6.2 Chronology of Events ------------------------------------------------------------------------------------------ 29

6.3 Groundwater Modeling, Tarawa Terrace Area ------------------------------------------------------------- 29

6.4 Data Analyses, Hadnot Point Area --------------------------------------------------------------------------- 30

6.5 Water-Distribution System Analyses ------------------------------------------------------------------------ 30

7.0 Acknowledgments--------------------------------------------------------------------------------------------------- 31

Appendix A Preliminary Draft Agenda, Charge to the Panel, and Questions and Issues on 

 Groundwater and Water-Distribution Systems -----------------------------------------------A1–A4

Appendix B List of Panel Members, Presenters, and Observers --------------------------------------------B1–B2

Appendix C Curriculum Vitae for Panel Members ------------------------------------------------------------C1–C22

Appendix D Panel Members’ Premeeting Comments ------------------------------------------------------- D1–D22

Compact Disc (CD-ROM)----------------------------------------------------------------------------- Inside back cover

 Summary report and verbatim transcripts of meeting, Volumes I and II (PDF file format)

Figures

1. Map showing location of U.S. Marine Corps Base, Camp Lejeune, North Carolina -------------------------- 3

2. Map showing present-day (2004) water-distribution systems serving Hadnot Point, Holcomb 

 Boulevard, and Tarawa Terrace areas of U.S. Marine Corps Base, Camp Lejeune, 

 North Carolina ------------------------------------------------------------------------------------------------------ 4

iii
Glossary of Acronyms and Abbreviations

ASCE American Society of Civil Engineers

ATSDR Agency for Toxic Substances and Disease Registry

AWWA American Water Works Association

Blvd. boulevard 

DCE 1,1-dichloroethene

elog electric log

EMD Environmental Management Division, U.S. Marine Corps 

Base Camp Lejeune

EPA U.S. Environmental Protection Agency

ft feet

ft/d foot per day

ft/s foot per second

FOH Federal Occupational Health

gal gallon

gal/min gallon per minute

GIS Geographic Information System

in. inch

in/yr inch per year

MESL Multimedia Environmental Simulations Laboratory

mg/L milligrams per liter

mL milliliter

NCEH National Center for Environmental Health

NPL National Priorities List

PCE tetrachloroethylene

PHA public health assessment

ppb parts per billion

QA/QC quality assurance and quality control

RI/FS remedial investigations/feasibility studies 

SCADA supervisory control and data acquisition

SGA small for gestational age

TCE trichloroethylene

USMC U.S. Marine Corps

USGS U.S. Geological Survey 

UST underground-storage tank

VOC volatile organic compound

WTP water-treatment plant

Disclaimer

Use of trade names and commercial sources is for identification only and does not 

imply endorsement by the Agency for Toxic Substances and Disease Registry, the 

Centers for Disease Control and Prevention, or the U.S. Department of Health and 

Human Services.

iv
Expert Peer Review Panel Evaluating ATSDR’s 

Water-Modeling Activities in Support of the 

Current Study of Childhood Birth Defects and 

Cancer at U.S. Marine Corps Base Camp Lejeune, 

North Carolina

Analyses of Groundwater Resources and Present-Day (2004) 

Water-Distribution Systems, March 28–29, 2005

Morris L. Maslia, Editor

EXECUTIVE SUMMARY

On March 28–29, 2005, the Agency for Toxic Substances and Disease Registry (ATSDR) 

held a 2-day expert peer review meeting in Atlanta, Georgia. ATSDR requested the panel of nine 

experts to provide input on the agency’s groundwater resources and water-distribution system 

modeling activities conducted from March–December 2004 at U.S. Marine Corps (USMC) Base, 

Camp Lejeune, North Carolina. As explained during the meeting, these present-day modeling 

activities are being conducted to enable ATSDR to historically reconstruct the water systems 

serving the base from 1968–1985. The historical reconstruction will allow ATSDR to estimate 

relative concentrations of particular contaminants in the water-distribution systems during that 

time frame so that exposures can be quantified. Panel members were provided with background 

information regarding ATSDR’s current epidemiologic study, including activities conducted thus 

far, findings to date, and the role of modeling and historical reconstruction in the study. During 

the meeting, the ATSDR technical team provided overviews and technical details pertaining to the 

modeling approaches and activities performed to date.

Before the meeting, ATSDR provided panel members with a list of questions to review. 

Eight questions pertained to groundwater issues, seven were related to water-distribution systems,

and four were part of the overall charge to the panel. Questions related to water-distribution 

systems were modified on the second day of the meeting. Throughout the meeting, the panel 

provided answers to these questions and offered suggestions to help ATSDR proceed with its 

future endeavors. Overall, the experts indicated that this was an important study to conduct 

and they were impressed with the quality of work performed to date. The panelists did note, 

however, that specific principal issues need to be addressed, and made recommendations for 

ATSDR’s next steps. As decided among ATSDR, the panel chair, and panel members, panelists 

provided individual recommendations throughout and at the conclusion of the meeting. These 

recommendations are presented in Section 6.0 of this report, and are briefly summarized.
A comprehensive review of archived files and other documents (interchangeably referred 

to as “data archaeology” and “data discovery”) is a priority and should precede other previously 

scheduled activities. To support both the groundwater and water-distribution system efforts, 

ATSDR should conduct in depth searching of records for additional quantitative data and detailed 

information of interconnections between the water-distribution systems. Also, ATSDR should 

obtain information describing the historical uses of tetrachloroethylene (PCE) at ABC One-Hour 

Cleaners and further characterize the Holcomb Blvd. and Hadnot Point systems.

ATSDR planned to extensively use water-distribution system models to estimate historical 

contaminant concentrations in the systems. Instead, the agency should use simple mixing models 

that require less effort and resources, but will provide the needed information.

To address groundwater-modeling uncertainty, ATSDR should consider using probabilistic 

methods (e.g., Monte Carlo simulation) to evaluate uncertainty inherent in model parameter 

arrays. 

Panelists suggested ATSDR reassess its schedule of activities and prioritize its efforts. 

ATSDR should then proceed based on the outlined priorities and available resources.

In the groundwater-flow model for the Tarawa Terrace area, ATSDR was evaluating recharge 

using an average annual value. The agency should consider other methods to more accurately 

account for recharge.

 Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
1.0 Introduction

1.1 Background

Operations began at U.S. Marine Corps (USMC) Base Camp Lejeune in the 1940s. Today, 

nearly 150,000 people work and live at the base, including active duty personnel, dependents, 

retirees, and civilian employees. About two-thirds of the active duty personnel and their 

dependents are younger than 25 years of age. The base consists of 15 different housing areas; 

families live in base housing for an average of 2 years. During the 1970s and 1980s, family 

housing areas were served by three water-distribution systems: Hadnot Point, Tarawa Terrace, and 

Holcomb Blvd. (Figure 1). 

Underground storage tanks (USTs) used for storing waste-degreasing solvents were 

installed in the Hadnot Point area in the 1940s and 1950s. In 1954, ABC One-Hour Cleaners 

(ABC Cleaners) began operating about 500 ft north of the base. In 1958, a supply well for 

Tarawa Terrace family housing units was installed about 1,000 ft southeast of the cleaners, just 

west of the intersection of Lejeune Blvd. (Highway 24) and Tarawa Blvd. On-base sampling 

conducted from 1980–1985 identified volatile organic compound (VOC) contamination in Tarawa 

Figure 1. Location of U.S. Marine Corps Base, Camp Lejeune, North Carolina.

Tarawa

Terrace

Camp

Johnson

Camp Lejeune

Military Reservation

Holcomb

Boulevard

Hadnot

Point

Marine Corps

Air Station

Stone

Bay

Rifle

Range Courthouse

Bay

Onslow

Beach

Jacksonville

Atlantic Ocean

New River

EXPLANATION

Location of Camp Lejeune in

Onslow County, North Carolina

WATER-DISTRIBUTION

SYSTEM AREA

CAMP LEJEUNE MILITARY

RESERVATION

0 5 KILOMETERS

0 5 MILES

1.0 Introduction 
Terrace and Hadnot Point system wells. Among the contaminant constituents detected were 

trichloroethylene (TCE), tetrachloroethylene (PCE), and benzene in wells at Hadnot Point. PCE, 

TCE, and 1,1-dichloroethene (DCE) were detected in the Tarawa Terrace wells. On January 27, 

1985, a fuel pump in the Holcomb Blvd. water-treatment plant (WTP) broke. While repairs were 

being made, the Holcomb Blvd. service area received water from the Hadnot Point WTP (Figure 2). 

On January 31, 1985, water samples collected at taps within the Holcomb Blvd. service area 

temporarily receiving water from the Hadnot Point WTP contained high levels of TCE and DCE. 

In early February 1985, all contaminated wells in the Hadnot Point and Tarawa Terrace areas 

were reportedly shut down. 

In 1989, the U.S. Environmental Protection Agency (EPA) placed USMC Base Camp 

Lejeune and ABC Cleaners on its National Priorities List (NPL) of sites requiring environmental 

investigation (also known as “Superfund” sites). In August 1990, the Agency for Toxic 

Substances and Disease Registry (ATSDR) conducted a public health assessment (PHA) at 

ABC Cleaners. The PHA found that PCE, detected in on- and off-site wells, was the primary 

contaminant of concern. Other detected contaminants included vinyl chloride, TCE, benzene, 

toluene, 1,2-dichloroethylene (1,2-DCE), and 1,1-DCE. 

Figure 2. Present-day (2004) water-distribution systems serving Hadnot Point, Holcomb Boulevard, and Tarawa 

Terrace areas of U.S. Marine Corps Base, Camp Lejeune, North Carolina.

Marine

Corps

Air Station

Northeast Creek

New River

Wallace Creek

Hadnot

Point WTP

Service Area

Hadnot

Point

WTP

Holcomb

Boulevard WTP

Holcomb

Boulevard WTP

Service Area

0 1 2 MILES

0 1 2 KILOMETERS

Camp

Johnson

Camp Knox

Trailer Park

Tarawa

Terrace

Naval

Hospital

Midway Park

Berkley

Manor

Watkins

Village

Paradise Point

Hadnot Point

Frenchs

Creek

EXPLANATION

WATER-DISTRIBUTION SYSTEMS

Tarawa Terrace

Holcomb Boulevard

Hadnot Point

CAMP LEJEUNE MILTARY RESERVATION

WATER PIPELINE

RAILROAD

WATER TREATMENT PLANT (WTP)

Frenchs Creek

ABC One-Hour Cleaners

 Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
In 1997, ATSDR completed a PHA for the base, which concluded that estimated exposures 

to VOCs in drinking-water were significantly below the levels shown to be of concern in animal 

studies. Thus, ATSDR determined that exposure to VOCs in on-base drinking water was unlikely 

to result in cancer and noncancer health effects in adults. However, because scientific data 

relating to the harmful effects of VOCs on a child or a fetus were limited, ATSDR recommended 

conducting an epidemiologic study to assess the risks to babies and children who were exposed 

in-utero to chlorinated solvents (e.g., PCE and TCE) contained in on-base drinking water. 

Following this recommendation, ATSDR conducted a study of adverse birth outcomes 

in 1998. ATSDR used various databases to evaluate possible associations between maternal 

exposure to contaminants contained in base drinking water and mean birth weight deficit, preterm 

birth (<37 weeks gestational age), and small for gestational age (SGA). To identify women living 

in base housing when they delivered, birth certificates were collected for live births that occurred 

January 1, 1968, through December 31, 1985. The study found that exposure to PCE in drinking 

water from the Tarawa Terrace system was related to an elevated risk of SGA for children of 

mothers older than 35 years and who experienced two or more prior fetal losses. The study also 

found that an elevated risk of SGA, though only identified among male infants, was associated 

with long-term exposure to TCE from the Hadnot Point water-distribution system. The study 

could not, however, evaluate childhood cancers and birth defects.

Currently, ATSDR is conducting a case-control epidemiologic study to evaluate exposure 

in-utero and during infancy (up to 1 year of age) to VOC-contaminated groundwater via waterdistribution systems at USMC Base Camp Lejeune from 1968–1985. The study will assess rare 

diseases, including specific birth defects (e.g., neural tube defects and cleft lip) and childhood 

cancers (e.g., childhood leukemia). The study is a multi-step process that includes: 

(1) a scientific literature review to identify particular childhood cancers and birth defects 

associated with exposure to VOC-contaminated drinking water, 

(2) a telephone survey to identify potential cases, 

(3) a medical-records search to confirm the diagnoses of the reported cases, and 

(4) a case-control study to interview parents (collect information on potential risk factors) 

and obtain exposure estimates using water-modeling techniques. 

ATSDR has completed the literature review and the telephone survey. The medical-records 

search to verify reported cases is ongoing, and work is proceeding with the case-control study. 

The agency will also be interviewing parents of cases and controls from spring through summer 

2005 to collect detailed information on residential history, parental risk factors, and maternal 

water consumption. 

No exposure data and very limited historical contaminant data are available to support 

the epidemiologic study. As a result, ATSDR is using modeling techniques to estimate the 

movement of contaminants in groundwater and in water-distribution systems at the base. This 

information will be provided to epidemiologists so that estimates of historical exposures can be 

quantified. From March–December 2004, ATSDR conducted modeling analyses of groundwater 

resources and present-day (2004) water-distribution systems serving the base (see Figure 2 for 

locations of the present-day systems). ATSDR plans to use the present-day water-distribution 

system modeling analyses to historically reconstruct water-distribution systems at the base from 

1968–1985; the agency will then be able to estimate the concentrations of particular contaminants 

delivered through the drinking-water system and the frequency and duration of exposure to 

contaminants in the drinking water.

ATSDR encountered several issues complicating the calibration of groundwater-flow and 

present-day (2004) water-distribution system models. Therefore, before ATSDR could consider 

historical events, the agency wanted to convene a panel of experts to discuss outstanding issues 

and questions regarding the groundwater- and water-distribution system modeling activities 

conducted to date at the base. 

1.0 Introduction 
On March 28–29, 2005, ATSDR held a peer review panel meeting in Atlanta, Georgia, to 

obtain external input and guidance regarding approaches, methods, and assumptions applied 

to modeling projects at the base. ATSDR asked nine panel members to comment on specific 

modeling issues and questions as well as provide ATSDR with recommendations to accomplish 

and complete modeling and historical reconstruction activities.

1.2 Meeting Organization

Nine nationally and internationally recognized experts in groundwater and water-distribution 

system modeling participated in the 2-day meeting. Dr. Barry L. Johnson (Assistant Surgeon 

General, retired) served as the panel chair. 

One month before the meeting, panel members received the overall charge, a list of targeted 

issues and questions, PHAs conducted at ABC Cleaners and USMC Base Camp Lejeune, 

descriptions of field-data collection activities, and draft technical documentation. Presentations 

presented at the meeting by ATSDR and its contractors included: 

(1) an overview of the agency’s current epidemiologic study; 

(2) detailed descriptions of the geohydrologic framework in the Tarawa Terrace area groundwater-model simulations and interpretations of related groundwater contamination; 

(3) a summary of water-modeling activities; 

(4) an overview of analyses of present-day (2004) water-distribution systems; and 

(5) detailed descriptions of field-testing procedures, activities, and results related to the 

present-day water-distribution systems serving the base. 

Throughout the meeting, panel members asked questions, provided responses to the agency’s 

questions and charge, and noted specific aspects that need further evaluation. Following the end 

of discussions on Day 2, the chair asked each panel member to provide individual comments and 

recommendations to ATSDR based on material provided to them before and during the meeting 

(Section 6.0 and Appendix D). Four USMC Base Camp Lejeune representatives, one public 

member, one reporter, and about 15 observers (mostly ATSDR staff members) attended all or part 

of the meeting. One public member asked questions and provided comments.

This report summarizes the discussions and recommendations from the 2-day meeting. 

Section 2.0 presents opening statements, which includes an overview of ATSDR activities. 

Section 3.0 summarizes water-modeling activities conducted to date as presented by 

members of ATSDR’s water-modeling team. Section 4.0 presents the panel’s discussions and 

recommendations related to specific questions posed by ATSDR. Section 5.0 presents a summary 

of discussions and responses to questions from the public. Section 6.0 documents the panel 

members’ recommendations. Appendix A contains materials provided to meeting attendees, 

including the agenda*, the overall charge to the panel, and specific questions on groundwater and 

water-distribution systems that panelists were asked to address during the meeting. Lists of panel 

members along with meeting presenters and observers are included in Appendix B. Curriculum 

vitae for the panel members (nine panelists and the chair) are provided in Appendix C. Appendix D 

contains draft premeeting comments provided by each of the nine panel members. Copies of this 

summary report and two volumes of verbatim transcripts of the meeting (in PDF file format) are 

provided on a CD located on the inside back cover of this report. 

*Appendix A includes an agenda prepared before the meeting. Based on decisions made during the meeting, the 

panel members and ATSDR staff chose to have each panel member provide recommendations to ATSDR rather than 

draft the panel communiqué indicated in the original meeting agenda.

 Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
2.0 ATSDR Objectives and Goals

2.1 Welcoming and Opening Remarks

	 Tom Sinks, Acting Director, NCEH/ATSDR

Dr. Tom Sinks, Acting Director for the National Center for Environmental Health (NCEH) 

and ATSDR, welcomed panel members and introduced the panel chair. Dr. Sinks presented the 

overall charge to the panel, which included four questions regarding ATSDR’s groundwater- and 

water-distribution modeling activities (see Appendix A). Dr. Sinks noted that ATSDR would 

challenge itself to use the best science possible to reach its goals, while being open to criticism 

and comments. He emphasized that the objective of the meeting was to obtain critiques and 

recommendations from the panel members regarding ATSDR’s modeling approaches.

2.2 Statement by the Chair

	 Barry L. Johnson, Panel Chair

Dr. Barry L. Johnson (Assistant Surgeon General, retired) read a statement explaining that 

the panel was charged with considering the appropriateness of ATSDR’s approach, methods, and 

time requirements related to water-modeling activities, and was being asked to focus solely on 

issues pertaining to water modeling. He noted that ATSDR is in the early stages of its analyses. 

The data and interpretations are, therefore, subject to modifications, in part dependent on panel 

members’ input.

2.3 Summary of ATSDR Activities

	 Perri Z. Ruckart, Principal Investigator, ATSDR

Ms. Perri Z. Ruckart, an epidemiologist with ATSDR’s Division of Health Studies, provided 

information on the site background, ATSDR activities conducted to date, and the current ATSDR 

epidemiologic study (as described in Section 1.1).

Ms. Ruckart explained that water-modeling results are needed to answer several questions for 

the epidemio­logic study. These include: 

(1) sources of contamination; 

(2) specific contaminants that impacted the water supply; 

(3) time frame when groundwater contamination reached drinking-water supply wells 

and the duration of contamination; 

(4) processes used for distributing contaminated water throughout the base’s 

water-distribution systems; and 

(5) specifics of exposure (i.e., duration, frequency, and spatial distribution of exposure 

to contaminated water supplies). 

She noted that the epidemiologic study activities are anticipated from spring 2005 through 

the expected completion date of fall 2007, based on the current project time line.

2.0 ATSDR Objectives and Goals 
3.0 Summary of Water-Modeling Activities

3.1 General Overview

	 Morris L. Maslia, Project Officer, ATSDR

Mr. Morris L. Maslia, a research environmental engineer and project officer with the 

Exposure-Dose Reconstruction Program within ATSDR’s Division of Health Assessment and 

Consultation, began by introducing members of the water-modeling team. The team includes 

representatives from various organizations: Morris Maslia and Jason Sautner of ATSDR; Claudia 

Valenzuela and Joseph Green of the Oak Ridge Institute for Science and Education; Robert Faye of 

Robert E. Faye and Associates, Inc.; Mustafa Aral of the Multimedia Environmental Simulations 

Laboratory (MESL) at the Georgia Institute of Technology; and Walter M. Grayman of W.M. 

Grayman Consulting Engineer*. Graphs presented showed the distribution of the total work effort 

and staff budgeting for groundwater analysis, water-distribution system analysis, data discovery, 

and communications. Groundwater analysis represents about 35% of the total effort, whereas 

water-distribution system modeling represents about 40% of the total effort to date. For waterdistribution system analysis, assembling accurate information and data about the present-day 

system and georeferencing this information and data (spatial analysis and geographic information 

systems activities) were the driving forces of the effort. The present-day water-distribution system 

modeling has utilized more time and staff than any of the other tasks. Mr. Maslia provided the 

following summary of water-modeling activities conducted to date.

3.1.1 Overview of Water-Modeling Systems and Activities

USMC Base Camp Lejeune, located in coastal North Carolina, has seven water-distribution 

systems (Figure 1). ATSDR is focusing on three of these systems—Tarawa Terrace, Holcomb 

Blvd., and Hadnot Point—serviced by the Hadnot Point and Holcomb Blvd. WTPs (Figure 2). 

The Hadnot Point WTP in the southern area services the Hadnot Point water-distribution system. 

The Holcomb Blvd. WTP in the northern area, however, services both the Tarawa Terrace 

(currently combined with Camp Johnson) and the Holcomb Blvd. water-distribution systems.

A chronology of the water-systems operations displayed at the meeting documented 

beginning-operation dates for each WTP. However, specific dates for several facilities are in 

doubt as a result of conflicting and newly acquired information. According to the most recent 

data, the Hadnot Point, Tarawa Terrace, and Montford Point (a/k/a Camp Johnson) WTPs were 

constructed in 1943, 1951–1952, and 1957, respectively. However, ATSDR has been unable to 

confirm the month and year that the Holcomb Blvd. WTP began operating. ATSDR has obtained 

maps suggesting that operations began in 1973, but has also received documents indicating that 

operations began in 1971. An accurate date for the beginning of plant operations is a critical 

epidemiological issue and has caused some uncertainty regarding study design and approaches, 

particularly whether or not the epidemiologic study will consider exposure by months. The 

agency appreciates the panel’s expertise and advice on how to best proceed. 

*Dr. Grayman was not present at the meeting, but is a member of the water-modeling team assembled by ATSDR for 

the Camp Lejeune activities.

 Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
The Tarawa Terrace WTP reportedly closed in March 1987. However, ATSDR recently 

received a 1991 report, which suggests that this plant supplied water to Holcomb Blvd. in 1989. 

Several supply wells at Tarawa Terrace continued to operate after the discovery of groundwater 

contamination at wells TT-26 and TT-23, which were shut down in early 1985. The remaining 

wells were probably operational through 1986 and were most likely permanently abandoned 

before April 1987. ATSDR is still in the process of data discovery and is actively attempting to 

determine an accurate time frame of operations at these WTPs. 

Goals of the water-modeling activities are based on the needs of the epidemiologic study. 

First, groundwater-flow and transport models will simulate the arrival time of contaminants at 

wells, including the mean concentration and ranges of concentrations during the periods of well 

operation. Second, the water-distribution system models will simulate the spatial distribution of 

contaminants by housing location (e.g., Tarawa Terrace and Holcomb Blvd.). Third, groundwater 

and water-distribution system simulations will be subjected to various levels of analyses to 

assess and reduce uncertainties. Uncertainties regarding the accuracy of model input arrays 

and simulation results occur with respect to both groundwater and the model. ATSDR noted 

that it was relying on panel members to provide insight and recommendations for evaluating 

these uncertainties, and to determine which models are best suited for assessing uncertainties in 

groundwater flow, contaminant transport, and water-distribution systems.

3.1.2 Brief Overview of Groundwater Analyses

The Hadnot Point area was contaminated as a result of leaking USTs, spills, and other wastedisposal practices. Groundwater contamination in the Tarawa Terrace area is largely the result of 

improper disposal of dry cleaning wastes at ABC Cleaners and leaking underground-storage tanks 

(USTs) at several locations within Tarawa Terrace proper. Available information suggests that 

PCE contamination in the Tarawa Terrace area is most likely from a single identified source—

ABC Cleaners. The groundwater-modeling approach with respect to the Tarawa Terrace area 

includes: (1) the construction of a three-dimensional groundwater-flow model, (2) calibrating the 

flow model for estimated predevelopment (steady state) and transient (unsteady state) conditions, 

and (3) applying the flow model to the simulation of aqueous phase PCE fate and transport. 

A preliminary flow model has been constructed and calibrated for Tarawa Terrace aquifers of 

interest and used to simulate the advective transport of PCE from the vicinity of ABC Cleaners to 

supply wells TT-26 and TT-23. Additional modeling analyses, consisting of aqueous phase fate 

and transport simulation of PCE, remain to be undertaken and completed.

3.2 Groundwater-Modeling Analyses

	 Robert E. Faye, Civil Engineer/Hydrologist, Robert E. Faye and Associates, Inc.

Mr. Robert E. Faye assisted ATSDR in constructing and calibrating the groundwater-flow and 

advective transport models for the Tarawa Terrace area. His presentation is summarized below.

3.2.1 Geohydrologic Framework

The geohydrologic framework was developed to quantify and describe specific aspects 

(i.e., potentiometric levels, geometry, and hydraulic characteristics) of the aquifers and confining 

units at Tarawa Terrace at a scale and level of detail appropriate for use in groundwater flow and 

contaminant fate and transport models. Data available for framework analyses included 44 electric 

logs (elogs), 100 boring logs, and 17 drillers’ logs obtained from various sources (e.g., remedial 

3.0 Summary of Water-Modeling Activities 
investigations/feasibility studies [RI/FS] at Tarawa Terrace, Montford Point, Holcomb Blvd., and 

vicinities). Through the framework analyses, 11 confining units and aquifers were identified, most 

of which are explicitly represented in the preliminary groundwater-flow model.

Two reports summarizing groundwater conditions, well data, and geohydrology at USMC 

Base Camp Lejeune—published by the U.S. Geological Survey (USGS) in the late 1980s—were 

referenced. These reports used various elogs and drillers’ logs to identify the number of confining 

units across the base. Essentially, the geohydrologic framework developed for this study closely, 

but not entirely, conforms to the USGS’s framework analysis. Results of the framework analyses, 

partly constrained by estimated chronostratigraphic boundaries, were identified with the top of 

what Mr. Faye called the local confining unit (top of the Eocene) and the top of the Beaufort 

confining unit (identified by the USGS as the top of the Paleocene). Similar patterns of permeable 

and poorly permeable units were identified on selected elogs and boring logs to gain insight into 

possible depositional cycles occurring at various depths. Permeable units of appropriate thickness 

were identified as aquifers; poorly permeable units were identified as confining units. This 

information was then correlated with the available chronostratigraphic boundaries to establish 

continuity of similar sediment groups in the subsurface from borehole to borehole.

Another component of the framework is the analysis of aquifer test data. About 60 tests—

almost all single well tests—were obtained for wells that supply the three water-distribution 

systems. Test data were used in conjunction with the USGS aquifer test analyses worksheets to 

determine horizontal hydraulic conductivity at various locations and depths within the study area.

In addition, an approximation of prepumping groundwater levels at and near Holcomb Blvd., 

Tarawa Terrace, and Camp Johnson was accomplished by identifying and mapping the earliest or 

highest available measurement of water levels. The conceptual groundwater-flow model and the 

estimates of pre-pumping levels indicate that the predevelopment potentiometric surfaces in all 

the aquifers were relatively similar. Accordingly, Northeast Creek and New River (Figure 2) are 

probably flow boundaries for all the aquifers of interest in this study. Groundwater-flow directions 

in the Tarawa Terrace area generally traveled east or south toward Northeast Creek and New 

River. Flow directions in the Holcomb Blvd. area generally traveled north, west, and northwest 

toward Northeast Creek and New River.

3.2.2 PCE Contamination at Tarawa Terrace and Vicinity

The quantity and occurrence of PCE and associated contamination in the Tarawa Terrace 

and Upper Castle Hayne aquifers, located at and near the Tarawa Terrace base housing area, were 

computed using analyses of water samples collected at several supply wells and at hydrocone 

sampling locations. Also obtained were ancillary data site locations, sampling depths, and the 

concentrations of contaminants. Mr. Faye pointed out that limited data were used to assess 

contaminant concentrations at the wellheads. He noted that ATSDR recently became aware 

of additional sample analyses, including monthly samples collected at supply well TT-25 and 

weekly samples collected downstream of the Tarawa Terrace WTP in the mid-1980s. ATSDR 

is trying to obtain these data. For most of these wells, ATSDR also has obtained information 

regarding well construction, dates wells were placed online, and dates when wells were removed 

from service. An overview of Mr. Faye’s remarks follows:

Data collected between 1991–1993, primarily “direct push technology” data, revealed the 

highest PCE concentrations. Most of the 40–50 data points were collected at depth intervals of 

15–25 ft (upper zone) and 35–45 ft (lower zone). Both field and laboratory measurements were 

available.

10 Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
According to the model, under normal operations supply well TT-26 would capture all 

aqueous PCE introduced into the subsurface and into the groundwater at ABC Cleaners. However, 

fairly large concentrations of PCE occur in the unsaturated zone north and west of the cleaners, 

and smaller concentrations of PCE have been detected south of TT-26 (near supply well TT-23). 

Well TT-26 is suspected as the primary well that delivered PCE to the water-distribution system.

An estimate of PCE mass at Tarawa Terrace was calculated. The method included: 

(1) creating upper and lower PCE concentration shells, 

(2) developing an average (midconcentration shell) using aerial and spatial distribution, 

(3) calculating the volume of aquifer material between the shells using the midconcentration 

shells and multiplying by effective porosity, 

(4) computing the area-weighted PCE concentration between the average shell contours 

(considered the volume-weighted PCE concentration), and 

(5) multiplying the volume-weighted PCE concentration by the volume adjusted by effective 

porosity.

A PCE mass of 2,500 pounds (185 gal was calculated between the two shells. Mr. Faye stated that 

the 185 gal of PCE is most likely a small percentage of the total amount of PCE actually contained in 

the aquifers, particularly because ABC Cleaners historically used about 100 gal of PCE each month, 

according to a National Oceanic and Atmospheric Administration report.

PCE, TCE, and DCE concentrations at supply well TT-26, and PCE concentrations at supply 

well TT-23 during 1985–1991 were displayed graphically. Data for TCE, a daughter product of 

PCE, suggest that biodegradation of PCE was occurring. 

3.2.3 Groundwater-Flow Model at Tarawa Terrace and Vicinity

A calibrated groundwater-flow model is necessary, ultimately, to simulate the fate and 

transport of PCE from the vicinity of ABC Cleaners to Tarawa Terrace supply wells. Mr. Faye 

emphasized that the information being presented details preliminary calibrations that have 

provided some reasonable results, but the flow and advective transport models have not been 

tested completely for sensitivity. Mr. Faye noted that ATSDR anticipates panel input regarding 

how to best proceed with the model. A summary of groundwater-flow model efforts to date 

follows.

Model Features and Input

The model grid consists of 270 columns and 200 rows and includes inactive and active areas 

of the model domain. The active model domains contain about 24,000 cells, with cell dimensions 

of 50 × 50 ft. The active domains are spatially equivalent for the nine layers (named layers 

1–9), which correspond to the geometries of the aquifers and confining units identified by the 

geohydrologic framework analysis.

Frenchmans Creek, a small drain in the western area of Tarawa Terrace, is represented in 

the model by drain cells in layer 1 (Tarawa Terrace aquifer). Northeast Creek is represented by 

the entire area down to the midchannel line (no-flow boundary). A specified altitude of 0.0 ft is 

assigned to all of the cells corresponding to Northeast Creek in layer 1. 

Arrays of horizontal hydraulic conductivity were assigned to each of the nine model layers. 

Cell-by-cell arrays were used to represent horizontal hydraulic conductivity of aquifer layers 1, 

3, 5, and 7. A uniform array of 5 ft/d was assigned to layer 9 and a uniform array of 0.2 ft/d was 

assigned to confining unit layers 2, 4, 6, and 8. 

3.0 Summary of Water-Modeling Activities 11
Vertical hydraulic conductivity of all layers was assigned as 10% of respective horizontal 

hydraulic conductivities. A specific yield of 0.20 was assigned to the Tarawa Terrace aquifer, 

which contains the water table. A storativity of 0.0005 was assigned as a uniform array to model 

layers 2–9. Except for a few measurements with questionable validity related to the Tarawa 

Terrace aquifer, no storage coefficient data were available. The specific storage of model layers 

was calculated by dividing aquifer storativity by thickness (as determined by the geometry of the 

layer). The result was assigned to the model layer as a cell-by-cell array.

Preliminary model calibration was accomplished in three steps: 

(1) developing a conceptual model of groundwater flow, 

(2) defining and simulating predevelopment (prepumping) conditions at the well heads to the 

greatest extent possible and determining whether the steady-state simulations support the 

conceptual model, and 

(3) defining operational conditions regarding pumpage and well heads and conducting 

transient simulations of these conditions. 

Transient simulations to date have been accomplished only for 1978–1994, which 

corresponds to the time of most water-level measurements.

Conceptual Model

Groundwater recharge occurs in the highland areas and flows downgradient toward Northeast 

Creek, Frenchmans Creek, and New River. USGS and North Carolina reports indicate that the 

long-term annual recharge is about 12 in/yr. However, the Tarawa Terrace area is not particularly 

dissected with drainage; Frenchmans Creek is the only prominent creek in the area. Accordingly, 

net groundwater recharge could range from 12–16 in/yr for this particular area. ATSDR will 

likely use a value within this range for estimating long-term average annual recharge. This issue 

will continue to be addressed during ongoing model simulations. 

Predevelopment Simulations

A map of simulated predevelopment water-level conditions in the Tarawa Terrace and Castle 

Hayne aquifers, shown for Tarawa Terrace and vicinity. It indicated that simulated water levels 

closely resembled the earliest or highest groundwater levels observed in the study area. Simulated 

groundwater-flow directions were shown to travel south and southeast toward New River and 

Northeast Creek from the highland areas to the north and northwest, thus conforming to the 

conceptual model. The map showed that discharge from the aquifers to Frenchmans Creek is 

continuous and well defined and that Northeast Creek and New River were sinks for groundwater 

flow. Simulated predevelopment recharge was about 13 in/yr.

Transient Simulation (1978–1994)

Camp Lejeune personnel measured monthly static and pumping levels for each on-base 

supply well using air lines. Although data gaps exist, ATSDR obtained these data for nearly all 

of the supply wells at Tarawa Terrace from January 1978 to April 1986. Uncertainties associated 

with these data include: 

(1) whether there was a standard for measurements, 

(2) whether water-level measurements were repeated until consistent results were obtained, 

(3) the amount of time that elapsed between terminating the pumping at the well and 

collecting the static level, and 

(4) the accuracy of the gauges used to obtain the measurements. Regardless, these 

measurements are the most comprehensive suite of water-level data available for model 

calibration and were used accordingly without adjustment or screening.

12  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
The simulation period was extended through 1994, because ATSDR obtained several accurate 

water-level measurements collected from various monitoring wells in the Tarawa Terrace area 

between 1991 and 1994. Therefore, instead of ending the transient analysis when the supply wells 

were shut down, the analysis was extended to make use of the additional measurements.

ATSDR is interested in 1-month stress periods, and the current simulation results correspond 

to 204 monthly stress periods from January 1978 to December 1994. Convergence problems 

resulted from difficulties with drying cells during transient simulations in the upper two layers 

of the model, presumably due to the low standard recharge rate of 13 in/yr. In these instances, 

the assigned recharge for the stress period was increased to maintain convergence. Simulated 

recharge rates ranged from 12–16 in/yr. The average simulated recharge rate for the period of 

pumping, 1978–1986, was about 12.7 in/yr. 

ATSDR used 1978 well capacity data obtained from Henry Von Oesen and Associates, Inc., 

and annual average daily pumpage rates (annual treated water rates) from the Tarawa Terrace 

WTP to estimate monthly pumping rates assigned to individual wells. The Tarawa Terrace 

well network probably operated on a rotation basis such that no well pumped continuously for 

extended periods, except during emergencies. However, no actual operational schedules for 

specific Tarawa Terrace wells are available. ATSDR applied three constraints in developing a 

pumping schedule: (1) honoring operational records, (2) ensuring that the actual rate used in 

the simulation was less than the capacity, and (3) making certain that total well discharge in a 

particular stress period and year equaled the average daily rate reported by USGS. 

Advective Transport Simulation

Preliminary advective transport simulations were conducted representing simulated 

groundwater-flow conditions at Tarawa Terrace during December 1984. Mr. Faye also presented 

the “water budget” for this stress period, which provided recharge, discharge, and storage change 

rates.

Mr. Faye explained that advective transport analyses related to flow paths generated by 

particles “seeded” within the immediate vicinity of ABC Cleaners and flow paths generated by 

particles “seeded” about 600 ft west of the cleaners. The transport analyses determined the time 

of contaminant travel from the “seeded” areas to Tarawa Terrace supply wells. Capture zones of 

particular supply wells are represented by particle flow paths to the respective wells and partly 

depend on the cell location where particles were introduced into the model. When particles were 

seeded in the immediate vicinity of ABC Cleaners, particles were entirely captured by pumping at 

well TT-26 only. Simulated travel time of the particles from the immediate vicinity of the cleaners 

to the location of well TT-26 was about 3.5 years, under simulated flow conditions representing 

December 1984. Particles seeded west of the cleaners, however, were also captured by well 

TT-23 (after 10,000 days). Although well TT-23 was pumped for less than a year before being 

permanently shut down in April 1985, according to base records. 

Mr. Faye displayed a map showing the capture zones of wells TT-26, TT-23, and TT-54, 

and offered an explanation for the occurrence of PCE at well TT-23 after only a short period of 

pumping for drinking-water production. He believes that when TT-26 was shut down for any 

period of time, the capture zone of well TT-54, located directly south of well TT-23, expanded 

into a highly contaminated section of the TT-26 capture zone. During such periods, contaminated 

groundwater was transported along flow paths toward well TT-54 and, because of its location in 

relation to well TT-23, this transport also occurred directly toward well TT-23. Thus, when well 

TT-23 began operating, groundwater containing PCE was available in the contributing aquifers 

in the immediate vicinity of the well. Therefore, PCE detected in well TT-23 was possibly not 

caused by the well immediately capturing PCE from the vicinity of ABC Cleaners. Rather, over 

time, well TT-23 was capturing contaminated groundwater intermittently transported to its vicinity 

by pumping at well TT-54, which began operating in 1961. When well TT-23 began routine 

operations in 1984 for a brief period, resident PCE in the aquifer proximate to the well was likely 

introduced into the well.

3.0 Summary of Water-Modeling Activities 13
3.3 Analyses of Water-Distribution Systems 

	 Morris L. Maslia, Project Officer, ATSDR

Mr. Maslia presented an overview of the approach for the water-distribution system analyses 

and discussed field testing performed thus far on present-day water-distribution systems. 

Highlights of his presentation are summarized below.

3.3.1 Approach to Analyses of Water-Distribution Systems 

ATSDR is evaluating two WTP service areas and three water-distribution systems. ATSDR 

has obtained its information on the piping network from AutoCAD drawings provided by the 

base’s Environmental Management Division (EMD) staff, field observations, and inquiries to the 

base’s water-utility staff. This information was needed to develop databases and model input data 

to calibrate models to present-day conditions.

If water-distribution systems operated completely independent of one another, then all 

residents served by a particular system would have had the same exposures, and therefore, 

historical reconstruction of the water-distribution systems would not be necessary. ATSDR could 

have assumed, based on its groundwater modeling, and application of materials mass balance 

concepts (“complete mixing” models) that people served by each system would have received 

the same concentrations of contaminants. However, information collected to date suggests 

that interconnections have existed between the systems during the study period (1968–1985). 

Therefore, ATSDR has identified the need to reconstruct historical water-distribution systems to 

accurately estimate exposures for the epidemiologic study period.

ATSDR considered the following two approaches for reconstructing the water-distribution 

systems: (1) using historical water-distribution system data (e.g., flows, demands, and cycling on 

and off of wells) to calibrate models, or (2) developing and calibrating water-distribution models 

to evaluate present-day conditions and then deconstructing the present-day systems to correspond 

to the historically configured systems. ATSDR has determined, however, that detailed records of 

historical data, such as system operations, flows, and demands, do not exist to support using the 

first approach. Therefore, ATSDR is following the second approach.

3.3.2 Analyses of Present-Day Water-Distribution Systems

Background

Because the required data types, specificity, and frequency for calibrating water-distribution 

system models to present-day conditions were unavailable, ATSDR established a field testing 

program to measure and gather these data. ATSDR obtained data from base EMD staff and waterutility operators on pipeline specifications (e.g., locations, sizes, and materials), storage-tank 

locations, high-lift pumps and head-discharge curves, operations, production, base housing, and 

facilities.

ATSDR has constructed hydraulically independent models for the present-day waterdistribution systems at Hadnot Point, Holcomb Blvd., and Tarawa Terrace. Mr. Maslia explained 

that ATSDR has gathered data from field tests conducted to date on hydraulics, C-factors* for 

pipeline characteristics, pump operations, and travel times. Because there are no individual 

household meters and no data on household consumption, ATSDR initiated a plan to obtain flow 

data by requesting that the USMC install flowmeters at strategic locations throughout the waterdistribution systems. The data would be used to obtain present-day per capita use and diurnal 

curves for specific housing areas.

14  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities

*Hazen-Williams C-factors.
From information provided by water-utility staff, ATSDR now understands that each waterdistribution system uses a controlling elevated storage tank that allows high-lift pumps to be 

triggered—according to the water level in the tank—to deliver water to the water-distribution 

system or to fill other storage tanks.

The results of the C-factor tests, conducted on pipelines of varying materials, diameters, and 

lengths, were provided to the panel members, and these data have been used for simulations.

ATSDR assigned each building (and its associated pipeline junction in the model) to a 

demand group (e.g., family housing). Group names were identified through a water-conservation 

analysis conducted in 1999 to estimate consumption of potable and nonpotable water at the 

base. A group categorized as “unaccounted for demand” (about 30% of metered production) 

was assigned because of the disparity between consumption, as determined from the waterconservation analysis, and metered production from the WTPs.

In terms of housing, the Hadnot Point service area (Figure 2) contains one family housing 

area and multiple bachelor housing areas; the remaining areas are primarily industrial use. 

Holcomb Blvd., however, has three housing areas; Tarawa Terrace is nearly 100% family housing, 

except for a few shopping centers.

Field Tests Conducted May–October 2004

Hadnot Point WTP service area, May 2004. This field test was conducted May 24–27 and 

consisted of three activities: 

(1) Liquid calcium chloride (CaCl2), 35% by weight, was injected into the transmission main 

on the water-distribution system side of the WTP to achieve an elevated conductance 

and chloride concentration, and recording conductivity and chloride concentration using 

continuous recording water-quality monitoring data loggers. 

(2) A sodium fluoride solution was injected into the transmission main to achieve an elevated 

fluoride concentration (before the test, the WTP fluoride was shut off so that fluoride 

concentrations in the water-distribution system pipelines approached background levels 

of about 0.2 mg/L).

(3) Water-distribution system pressures were monitored with continuous recording data 

loggers attached to selected hydrants. 

In addition to continuously recording tracer concentrations and conductivity, grab samples 

were collected for quality assurance/quality control (QA/QC) purposes. Samples were analyzed 

at the Hadnot Point WTP by ATSDR staff and then shipped to the Federal Occupational Health 

(FOH) Industrial Hygiene and Environmental Laboratory in Chicago, Illinois, for analysis. 

Twenty-seven hydrants were selected in the Hadnot Point area as monitoring locations. For 

monitoring conductivity and chloride and fluoride concentrations, nine hydrants were equipped 

with the Horiba W-23XD dual probe ion detector. For monitoring conductivity, nine hydrants 

were equipped with the Horiba W-21XD single probe ion detector, thus providing a total of 18 

monitoring locations for continuously recording conductivity data. For pressure measurements, 

nine hydrants were equipped with continuous recording Dickson PR300 pressure data loggers.

Holcomb Blvd. and Hadnot Point WTP service areas, August 2004. This field test was 

conducted August 25–27. It consisted of two activities: First, different sections of pipelines of 

varying lengths, diameters, and material types were tested to collect hydraulic data for calculating 

roughness coefficients (Hazen-Williams C-factor data). Second, an innovative approach was used 

for fire-flow testing (for model calibration purposes). Continuous recording-pressure monitoring 

equipment at several fire hydrants simultaneously recorded variations in pressure as different 

combinations of hydrants were flowed. Eight sections of pipelines, characterized by three 

different pipe materials (cast iron, polyvinyl chloride, and asbestos cement), were tested. Pipeline 

diameters ranged from 6–12 in., pipe lengths ranged from 700–1,672 ft, and flows ranged from 

3.0 Summary of Water-Modeling Activities 15
564–1,603 gal/min. Fire-flow tests were conducted at 12 locations. Pipeline diameters ranged 

from 4–12 in., pipe lengths ranged from 236–1,620 ft, and flows ranged from 773–1,120 gal/min. 

Fire-flow tests are frequently used in the process of calibrating a hydraulic water-distribution 

system model. The concept is quite straightforward.

Holcomb Blvd. WTP service area, September–October 2004. This field test was 

conducted September 22–October 12. It consisted of monitoring fluoride dilution and reinjection 

in the Holcomb Blvd. WTP area (including Tarawa Terrace and Camp Johnson). The purpose of 

this preliminary test was to:

(1) estimate travel time between points in the water-distribution system by shutting 

off and then restarting fluoride at the WTP, 

(2) record the fill-and-draw characteristics at the controlling elevated storage tanks 

(S2323 at Paradise Point and SM623 at Camp Johnson), and 

(3) record the sequence of when distribution-system water (with its fluoride concentration) 

was filling the tanks and when storage-tank water (with its fluoride concentration) was 

being supplied to the water-distribution system. 

Nine locations in the water-distribution system were equipped with the Horiba W-23XD 

continuous recording, dual probe ion detector data logger. Monitoring locations included the 

main transmission line from the WTP to the water-distribution system, the Tarawa Terrace treated 

water reservoir, two controlling elevated storage tanks, and five hydrants located throughout 

the housing areas. The fluoride at the Holcomb Blvd. WTP was shut off at 1600 hours on 

September 22. A background concentration of about 0.2 mg/L in the water-distribution system 

was reached by September 28. At 1200 hours on September 29, the fluoride was turned back on 

at the WTP. The test continued until loggers were removed and data downloaded on October 12. 

In addition to the continuous recording data loggers, split grab sample analyses were conducted 

for QA/QC purposes. Nine rounds of water samples were collected at each monitoring location 

during the test. For each round, the Holcomb Blvd. WTP water-quality lab analyzed 25 mL of the 

grab sample water and the FOH Industrial Hygiene and Environmental Laboratory analyzed the 

remaining 225 mL.

Household Meters

To address the fact that no household meters exist on base, ATSDR is applying the concept 

of “district metering area” to develop per capita demand in particular areas. To date, 16 Dynasonics 

magnetic flowmeters have been installed but have not been calibrated because of technical problems 

encountered in the field (this problem is in the process of being resolved). Mr. Maslia explained 

that calibration of the meters is the next step planned for field activities. He requested the panel’s 

input on whether these activities should be pursued and whether the meters would provide useful 

data.

16  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
4.0 Panel Discussions

Throughout the 2-day meeting, panel members asked questions, made comments, and 

discussed issues related to ATSDR’s modeling efforts and the associated epidemiologic study. 

In addition, panel members had provided ATSDR with comments before the meeting. As agreed 

upon by the panel, ATSDR did not respond to premeeting comments, but would consider these 

issues during ongoing modeling activities and when preparing the final modeling report. ATSDR 

did, however, provide responses during the meeting to general premeeting comments related to 

groundwater (responses provided below). This section summarizes ATSDR’s initial responses 

to premeeting comments (Section 4.1) and discussions and suggestions made by panel members 

during the meeting on specific topics (Section 4.2).

4.1 ATSDR Response to Premeeting Comments 

	 Morris Maslia, Project Officer, ATSDR

Mr. Maslia highlighted the following overarching groundwater issues introduced by the 

panel members’ premeeting comments. In doing so, he posed additional questions for the panel to 

consider during the meeting.

Uncertainty

Several premeeting groundwater comments concerned the uncertainty of evaluating geologic 

and aquifer characteristics. Some panelists suggested that probabilistic methods be used, such as 

the Monte Carlo simulation. Mr. Maslia responded that these simulations would be a possible next 

step, but asked the panel to consider if using probabilistic or uncertainty methods should precede 

refinement of the Tarawa Terrace model. Also, Mr. Maslia noted that ATSDR will consider 

using parameter estimation methods to evaluate sensitivities of specific groundwater-flow model 

parameters (e.g., vertical hydraulic conductivity and recharge). 

Modeling Boundaries and Source Conditions

Mr. Maslia stated that ATSDR would consider using sensitivity analysis to assess the 

nearness of the northern boundary to ABC Cleaners and the potential effect of moving the 

boundary farther away from the source. He noted that ATSDR was currently modeling advective 

flow. Mr. Maslia asked the panel members what effect the sensitivity of the model boundary 

might have when using fate and transport modeling. He added that ATSDR might consider using 

a genetic algorithm/optimization approach developed by the MESL at the Georgia Institute of 

Technology, which can use observed concentration data to determine source locations. In this 

instance, the algorithm uses historically observed values and simulates the source location, 

assumed to be ABC Cleaners. 

Fate and Transport

Mr. Maslia stated that in the future ATSDR intends to conduct complete fate and transport 

simulations, in addition to advective transport. He added that PCE at Tarawa Terrace is the 

only constituent currently under consideration for fate and transport analysis. He noted that the 

advective transport simulations for the Tarawa Terrace area provided preliminary estimates to 

start ATSDR’s analysis of the more complex contaminant fate and transport modeling analyses. 

4.0 Panel Discussions 17
4.2 Panel Discussions and Recommendations

4.2.1 General Questions on the Epidemiologic Study

Panel members asked several questions to clarify aspects of the epidemiologic study. 

Questions related to (1) how ATSDR would define and evaluate exposure, (2) how cases of 

illnesses compared to the general population, (3) who was considered unexposed, and (4) the 

temporal resolution required for the study. 

Dr. Leonard Konikow asked how ATSDR would define exposure and whether the aim was to 

evaluate exposure by household. Ms. Perri Ruckart explained that the goal of the water modeling 

was to determine when contamination arrived at the wells and to assess the spatial and temporal 

distribution of the contaminants by housing area. Mr. Maslia elaborated that the aim is to evaluate 

exposure at the street level. The water-distribution system is constructed such that a 2-in-diameter 

pipe goes from the street to the house; consequently, houses are considered in the modeling 

activities. 

Regarding the number of cases of illnesses found in the study group, Dr. Thomas Walski 

asked how the number compared to the general population. Dr. Frank Bove explained that these 

cases were identified through a survey, which makes it difficult to compare the numbers. He said 

that if the verified reported cases and the ones now being verified were combined, there would be 

a slight elevation of about two times the expected level for some of the health outcomes. Dr. Bove 

stated that this survey would need to be reevaluated, however, because assumptions were based on 

information that was doubtful or incorrect. 

Dr. Vijay Singh questioned who was living at U.S. Marine Corp Base Camp Lejeune but 

considered unexposed. Dr. Bove responded that in the past study, it was assumed that about 50% 

of live births were unexposed because they received water from the Holcomb Blvd. system. 

However, at present it is unclear whether or not interconnections existed between Holcomb Blvd. 

and Tarawa Terrace. If frequent transfers of water occurred between the Holcomb Blvd. and 

Hadnot Point WTPs, then exposure assumptions would require additional evaluation and possible 

modifications.

Regarding questions about the issue of temporal resolution desired for the study, Dr. Bove 

explained that the window of exposure depended on the particular disease. For neural tube 

defects and oral clefts, the exposure point of interest is the first trimester. Due to uncertainty, the 

study has requested data for the entire year before birth; the team will examine 3 months before 

and 3 months after conception, and also up to 1 year of life to assess childhood leukemia. At a 

minimum, the study team hopes to evaluate monthly averages. First, the population of unexposed 

and exposed individuals must be determined. Then, the concentrations of exposure will be 

ascertained assuming the data are available.

4.2.2 Lack of Historical Data

ATSDR acknowledged that a lack of historical data exists for the contaminant source, 

groundwater pumpage and levels, and water-distribution system operations. Panel members 

discussed these issues, indicating the importance of data discovery to obtain records of PCE 

use at ABC Cleaners and how ATSDR could account for time frames when data are unavailable. 

The panelists offered the following views.

18  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
Source

Dr. James Uber suggested that ATSDR focus on working back to the source to estimate the 

amount of PCE used each month. He questioned if more effort was needed to model the process 

of dry cleaning operations to assess the amount of contaminant lost and diluted in water and other 

aspects of the operation. Dr. Walski suggested speaking to the owner or employees of the cleaners 

before conducting laborious data discovery (e.g., obtaining tax records).

Groundwater

ATSDR asked the panel members how the agency should address the lack of pre-1978 

observed water-level data. Of particular interest is determining the amount of uncertainty 

and variability in arrival times (e.g., 6 months or a few years) that could be tolerated by the 

epidemiologic study. 

Dr. Konikow asked if ATSDR had any pumpage data before 1978. According to Mr. Faye, 

ATSDR had periodic snapshots of information, but it was sporadic and not always available for 

specific years (e.g., ATSDR has data for 1962 and 1971). Dr. Konikow explained that ATSDR 

could calibrate the model for periods when water-level data are available, and impose the 

stresses for the preceding time frame when data are lacking. He noted, however, that the issue 

of concentrations would still remain. Mr. Faye hoped to obtain adequate estimates through mass 

loading, but noted that this was only a single source. 

Water-Distribution System

ATSDR asked the panelists whether it would be feasible or necessary to simulate the 

complete 18-year historical period on a continuous basis.

Three panelists indicated that continuous modeling was unnecessary considering ATSDR 

was dealing with a single point of entry for much of the study period. One panelist noted, 

however, that ATSDR should consider calculating potential exposures for a continuous time 

series. Reconstructing probability distributions for the breakthrough curves and the contaminants 

entering the system was recommended, as such probabilistic distributions would provide a time 

series that could be correlated to individuals’ activities. 

4.2.3 Addressing Uncertainty and Variability

During meeting presentations, ATSDR discussed uncertainty and variability in modeling 

groundwater and water-distribution systems for the study period. After discussions, most panelists 

agreed that ATSDR should use probabilistic analyses to address geohydrologic uncertainty. The 

panelists also suggested that additional information was necessary to adequately address issues of 

interconnections between WTPs. A summary of panelists’ comments is presented below.

Groundwater

ATSDR asked the panel if the team should consider using probabilistic analyses to assess the 

variability and uncertainty of model parameters and contaminant concentrations at public supply 

wells. ATSDR also questioned panel members about their particular preferences in probability 

analysis modeling codes. 

Many panelists agreed that ATSDR should use some type of probabilistic analysis to (1) assess 

the impact of water blending of contaminated and noncontaminated wells, and (2) assess the 

uncertainty of the concentration arrival times at wells. Dr. Robert Clark generally approved of 

4.0 Panel Discussions 19
using probabilistic analysis, but noted that doing so would potentially incorporate an unnecessary 

level of complexity. Dr. Walski expressed a preference for “sensitivity analysis” to emphasize 

parameters to which the model is most sensitive. 

Water-Distribution Systems

TCE is the major contaminant of interest at Hadnot Point. ATSDR acknowledged uncertainty 

regarding interconnections between the Hadnot Point and Holcomb Blvd. WTPs, and asked the 

panel if ATSDR should consider probabilistic analyses to better quantify interconnection issues, 

ultimately determining a probabilistic estimate of exposure frequency at Holcomb Blvd. and 

Hadnot Point. The panel engaged in a discussion of the implications and uncertainties associated 

with the possible interconnections. Highlights of the discussion follow.

What is known about the interconnections?

The Holcomb Blvd. WTP began operations sometime between 1971 and 1973. Following 

the onset of operations, the frequency of water exchange between the Hadnot Point and Holcomb 

Blvd. WTPs is unknown. ATSDR found information confirming that an interconnection existed 

between Holcomb Blvd. and Hadnot Point in January 1985. Dr. David Dougherty indicated that 

a connection between the Holcomb Blvd. and Tarawa Terrace WTPs occurred sometime between 

1983 and 1985, and evidence suggests that people living in Holcomb Blvd. received Hadnot Point 

water before 1971.

Mr. Brynn Ashton, with the EMD, USMC Base Camp Lejeune, explained that much 

uncertainty exists about when the Hadnot Point and Holcomb Blvd. systems were interconnected. 

Currently, the base must obtain approval from the State to interconnect the systems. There are 

two operating permits for the systems and they are maintained separately. Dr. Bove questioned 

whether the State might have a record of each time the systems were connected. 

How does interconnectivity of systems affect selection of exposed and unexposed populations for 

the epidemiological study?

Mr. Benjamin Harding noted that ATSDR needed to find on-base populations that were 

exposed or unexposed to TCE. He questioned whether the Holcomb Blvd. population (during 

periods of no interconnections) could potentially be used for the on-base unexposed population. 

Dr. Bove cautioned about doing this because of known interconnections. Mr. Harding asked about 

the time frame needed for the unexposed population and questioned whether ATSDR could use 

a period within the study time frame (e.g., 1970–1975) when the systems were not connected. In 

response, Dr. Bove indicated that this could not be done; an exposed and unexposed population 

must be determined for the entire study period.

Should interconnections be modeled?

Mr. Harding indicated that he was unsure how the interconnections could be modeled when 

the time frames of interconnections were unknown. Even if ATSDR determines when the systems 

were or were not connected, Mr. Harding suggested that attempting to model interconnections 

may not be an effective use of agency resources.

Should probabilistic techniques be used?

Panelists indicated that ATSDR should use probabilistic analyses. Mr. Harding highly 

recommended applying probabilistic simulation methods (e.g, Monte Carlo analysis) to represent 

uncertain variables. Dr. Clark suggested that ATSDR use the PRP approach (developed by 

20 Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
Dr. Steven Buchberger at the University of Cincinnati) to evaluate use at the individual household 

level. Instead of using household demands, Dr. Walski suggested considering the time that each 

well is on as the stochastic variable because this would produce the most variability in the results. 

4.2.4 Suggested Modeling Approaches, Modifications, and Considerations 

During the meeting, ATSDR detailed its modeling approaches and responded to panelists’ 

questions regarding activities conducted to date and those planned for the future. After a detailed 

discussion, the panelists offered the views presented below. Overall, panelists recommended 

that ATSDR perform extensive data discovery (e.g., obtaining information on events chronology 

and interconnections) and use simplified mixing models instead of developing more complex 

historically reconstructed water-distribution system models.

Groundwater

ATSDR is conducting groundwater-flow modeling as a basis for the fate and transport 

analysis. Transient modeling was initially conducted from 1978–1994; a period that corresponds 

to almost all available water-level data. ATSDR has recently received monthly water-use data at 

Tarawa Terrace and other WTPs from the base for most of 1980–1985. Additional efforts will be 

made via data discovery (e.g., ascertainment of deposition documents and examining tax records) 

to determine the actual use of PCE at ABC Cleaners. ATSDR asked the panel if any modifications 

should be made to the groundwater-modeling approach and if the model should be expanded 

to include the Holcomb Blvd. and Hadnot Point areas. A summary of the panelists’ views is 

presented below.

Panelists did not recommend that ATSDR develop one model to cover the Tarawa Terrace, 

Holcomb Blvd., and Hadnot Point areas.

Instead of refining the existing model, panelists questioned whether resources should be 

applied to understanding the impact of other groundwater-contamination sources, particularly 

regarding the requirements of the epidemiologic study.

Dr. Uber suggested that the team describe the objectives of the groundwater-modeling effort 

in terms of the needs of the epidemiologic study.

Dr. Walski suggested performing an overall classification of the areas where contamination 

was known to occur, and the areas without contamination. People in the contaminated areas 

would be considered exposed and those in uncontaminated areas would be classified as 

unexposed. He also recommended that ATSDR use modeling to concentrate on the areas where 

contamination and exposure are unknown. As a next step, he recommended ATSDR prepare a 

matrix to determine a time frame when contamination did or did not occur.

Dr. Eric LaBolle asked whether ATSDR could use the preliminary groundwater-modeling 

results to provide a time range when the contamination could have arrived at well TT-26. He 

made the point that if well TT-26 had contamination during the entire study period, then the role 

of groundwater modeling might require much less detail than if groundwater modeling was being 

used to predict an arrival curve to the well.

Dr. LaBolle stated that the calibration of the transport model should focus on periods when 

the most reliable data are available.

Dr. Dougherty recommended that ATSDR move the northern boundary farther away from the 

source, but omit the sensitivity analysis.

Dr. Walski considered the historical pattern of contamination at Hadnot Point too complex to 

model because the numerous sources cannot be correlated to particular wells. 

4.0 Panel Discussions  21
Panelists suggested that ATSDR use smaller time steps, as drying and rewetting of the 

groundwater-flow model cells could lead to convergence problems. In this regard, Dr. LaBolle 

also recommended using a solver with dual-convergence criteria.

Dr. Konikow recommended performing grid-sensitivity testing to determine whether the grid 

spacing is appropriate. He suggested that ATSDR use 100-ft and 25-ft cell spacings to assess any 

differences. He said to use a 100-ft cell spacing if there are no differences; if there are differences 

and depending on the nature of these differences, Dr. Konikow suggested using a finer grid 

spacing. He stated that expanding the modeling effort to Holcomb Blvd. and Hadnot Point areas 

was dependent on whether ATSDR wanted to apply a fate and transport model to those areas. He 

indicated that ATSDR needed to have the results from Tarawa Terrace before determining if the 

models should be applied to other areas. 

Dr. Singh recommended that ATSDR consider a variable grid size, using finer grids closer to 

the source and coarser grids away from the source. 

Dr. Clark recommended that ATSDR consider accommodating degradation processes during 

fate and transport simulations. Not accounting for degradation products (e.g., vinyl chloride) 

could bias the simulated mass balance of contaminants. 

Water-Distribution Systems

ATSDR asked the panel members for recommendations to improve the models and whether 

three separate models (for Hadnot Point, Holcomb Blvd., and Tarawa Terrace) should be 

developed. In addition, the agency asked panel members to address whether or not ATSDR should 

model the Holcomb Blvd. and Hadnot Point WTP service areas separately.

Panelist opinions are detailed below, with most panelists emphasizing the need to collect 

additional data before refining the modeling approach.

Dr. Clark and Mr. Harding commented that developing three models to address each waterdistribution system would be appropriate for understanding present-day conditions. Mr. Harding 

noted that a simple mixing model would suffice for historical reconstruction purposes. 

Panelists agreed that more data discovery is required before determining the appropriateness 

of ATSDR’s approach to modeling Holcomb Blvd. and Hadnot Point as interconnected waterdistribution systems.

Panelists were unsure that refining the models would be necessary because the blended water 

is distributed to everyone in the Tarawa Terrace system. Refining the model might not increase 

the information on exposure.

Panelists concurred that the time frame of interconnections might require sophisticated 

modeling, though not yet.

Dr. Clark recommended using models to enable typical diurnal curve exposures, but 

Dr. Walski did not see the added value, given the limited data. Dr. Konikow pointed out that if the 

interconnection was not the only source of water to Holcomb Blvd., then a model could be useful 

in determining areas that did or did not receive Hadnot Point water. 

Panelists emphasized the need to demonstrate that contaminants did or did not arrive at well 

TT-26. Dr. LaBolle suggested ATSDR use a model that predicts the uncertainty in the arrival time 

and that ATSDR’s analysis should address geologic uncertainty. Dr. LaBolle noted that ATSDR 

might want data preceding the proposed time frame if other health outcomes are to be examined 

(e.g., adult cancer).

If water-distribution systems are not completely mixed, as suggested by field testing, 

Dr. LaBolle recommended focusing on a restricted area of the system. Dr. Clark commented on 

the need to consider how the blending in a system could cause different household exposures.

22  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
4.2.5 Parameter Estimation

ATSDR asked the panel whether the agency should consider using parameter estimation to 

assess model parameter sensitivity. The varying views expressed are highlighted below. Most 

panelists agreed that parameter estimation was needed, but that it should be used in parallel with 

other efforts to substantiate predictions. 

Dr. Clark recommended developing an independent dataset to validate predictions in addition 

to parameter estimations. He stated that this would be essential for the regression estimations.

Dr. Singh recommended using more efficient and powerful parameter estimation techniques 

in combination with genetic programming (i.e., load times). Because of the limited amount of 

data, this would be a much better approach than using only regression. 

Dr. LaBolle expressed concern about handling the uncertainty and variability in the 

subsurface. He stated that the current model constrained the characterization of the subsurface 

and, therefore, lacks the flexibility to address the uncertainty in the subsurface heterogeneity and 

its potential effects on exposure. Also, parameter estimation would be needed if ATSDR is to 

refine arrival times of contaminants at the wells.

Dr. Dougherty commented that model estimation was more significant than parameter 

estimation. 

4.2.6 Groundwater-Recharge Data

ATSDR asked the panel whether its methods to derive monthly groundwater-recharge rates 

were sufficient and requested recommendations on methods that might provide more refined 

estimates. Panelists offered varying opinions and issues for ATSDR to consider. A summary of 

these comments is presented below.

Dr. Clark recommended using meteorological data to obtain estimates.

Dr. Konikow asked whether ATSDR considered the possibility that recharge might be higher 

than natural recharge in urban areas as a result of various activities and conditions (e.g., car 

washing and leaky pipes). In addition, septic tanks and collection systems are a source of 

recharge. 

Dr. Dougherty suggested that to reduce the roughness of the estimate of recharge, ATSDR 

should consider using a simple model to represent the transport through the unsaturated zone to 

groundwater. At Tarawa Terrace, accretion at the contamination source is especially important 

because a septic system was employed. In addition to demonstrating the impacts of the preceding 

panel comments relative to groundwater conditions, such a simple model could smooth out some 

rewetting problems. 

4.2.7 Project Schedule

ATSDR has allotted a total project schedule of 3 years to complete this project, including 

delivering all historical reconstruction analyses to agency epidemiologists, and planning and 

organizing a peer review assessment of the final report products. Given panel deliberations thus 

far, ATSDR asked whether its schedule was appropriate and what, if any, changes should be made 

to the time frame. 

Most panelists agreed that this time frame was appropriate. The main factors that will drive 

the schedule are (1) data discovery, (2) methods to better understand the uncertainty regarding 

geohydrologic properties at Tarawa Terrace, and (3) using full-scale fate and dispersive transport 

models. 

4.0 Panel Discussions  23
4.2.8 Field Testing

In December 2004 and January 2005, Dynasonics, Inc., and AH Environmental Consultants, 

Inc., under contract to USMC Base Camp Lejeune, installed 16 flowmeters at selected locations 

throughout the Tarawa Terrace, Holcomb Blvd., and Hadnot Point water-distribution systems. 

The ATSDR water-modeling team used initial model simulations, field verification, and 

discussions with AH Environmental Consultants, Inc., staff to select meter locations. Metered 

flow measurements were considered necessary because of inconsistencies between supervisory 

control and data acquisition (SCADA) recorded data (provided by USMC Base Camp LeJeune) 

and a water-conservation analysis study of base water-utility operations. The conservation 

analysis indicated an approximate 30% difference between water produced and water used. 

For the epidemiologic study, ATSDR determined that these inconsistencies and differences 

are unacceptable. Obtaining measured flow data at locations throughout the water-distribution 

systems would also assist the ATSDR water-modeling team with hydraulic and water-quality 

model calibrations. 

ATSDR asked panel members if the water-distribution system tests could provide sufficient 

data to reliably calibrate the present-day models, and if these tests could appropriately develop the 

per capita consumption data and diurnal curve characteristics. ATSDR also asked for the panel’s 

comments on the novel fire-flow testing method for use with model calibration. Because of 

difficulties encountered with flowmeter field calibration, ATSDR also requested panel members’ 

input on the advisability of proceeding with additional calibration efforts.

Overall, the panelists commended ATSDR on the thoroughness and quality of the testing 

conducted to date. Specific observations and suggestions from the panelists follow.

Regarding the need to proceed with flowmeter calibration, Dr. Walski suggested that ATSDR 

proceed with the calibration because the meters were already installed, but he did not recommend 

allocating a lot of resources to this task. Dr. Walski was concerned that useful data would not be 

obtained because the meters are limited to a 2 ft/s threshold. Nonetheless, he recommended that 

ATSDR calibrate the meters and collect data for a 1-month period. Depending upon the quality of 

those data, the team could determine if the effort should be conducted for a longer period.

Dr. Walski suggested that ATSDR use a mass-balance approach and, as noted during the 

meeting, SCADA data would be required. SCADA equipment at the base, however, is not up-todate and is of questionable reliability. Dr. Walski explained that it is usually more economical to 

recalibrate the SCADA system than to install meters. 

Mr. Harding noted that reliable storage-tank elevation data were necessary for calibrating the 

model. Thus, if doubt existed concerning the SCADA system’s reliability, the issue needed to be 

settled because it is a boundary condition. 

Dr. Clark commented that the best approach for developing diurnal patterns would be to use 

the district metering approach, particularly considering that ATSDR has no other available data.

Mr. Harding cautioned ATSDR to consider the reason for obtaining water-use estimates, 

which he indicated were unnecessary at Tarawa Terrace except for handling the issue of well 

cycling. If ATSDR was measuring tank flows and levels at the plant only to establish water-use 

characteristics at the WTP, then he concurred with ATSDR’s field testing plan. 

24  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
5.0 Discussions and Responses to Questions from the Public

Mr. Jerry Ensminger (USMC, retired), a public member involved in contamination issues at 

the base since 1997, asked to address the panel with his comments and questions. Mr. Ensminger 

read a prepared statement submitted on behalf of Major Thomas A. Townsend (USMC, retired). 

Major Townsend and his family lived in Tarawa Terrace from January 1955 to May 1956*. The 

statement is provided verbatim in the meeting transcript (on the CD that accompanies this report) 

and summarized herein. Panel Chair Dr. Barry Johnson asked for Mr. Ensminger’s and Major 

Townsend’s comments to be made part of the public record and suggested to Dr. William Cibulas, 

director of ATSDR’s Division of Health Assessment and Consultation, that the agency provide 

responses to his serious questions. 

According to Mr. Ensminger, building of the Tarawa Terrace housing area began in 1952. 

He provided the history of the eight supply wells constructed in Tarawa Terrace: TT-26 in 1958; 

TT-52, TT-53, and TT-54 in 1961; and TT-27, TT-31, and TT-25 in 1972, 1973, and 1980, 

respectively. Mr. Ensminger stated that an additional well, TT-23, was constructed in 1984, 

but was not used for production because PCE contamination was detected. He provided panel 

members with supportive documentation for his statements. He read results from sampling events 

conducted in 1982, 1984, and 1985, indicating that PCE (up to 104 ppb in 1982), TCE (up to 

8.1 ppb in 1985), and DCE (up to 12 ppb in 1985) were detected in these on-base supply wells. 

His specific questions and comments are highlighted below, with responses by the ATSDR team 

and panelists. 

Statement: Mr. Ensminger asked the panel where the base obtained water to distribute to 

more than 1,800 housing units and commercial operations in Tarawa Terrace following the WTP 

closure in February 1985.

Response: Dr. Peter Pommerenk indicated that a pipeline was built from the Holcomb 

Blvd. WTP in about 1984, which directly connected to the raw-water tank. Therefore, he stated 

his belief that Tarawa Terrace residents received treated water from the Holcomb Blvd. area. 

According to reports received and reviewed by Mr. Faye, only wells TT-23 and TT-26 were taken 

offline in February 1985; the remaining wells continued to operate, possibly throughout 1985 and 

1986. 

Statement: Mr. Ensminger asked the panel members to refer to a document he provided to 

them dated March 1, 1985, which discusses alternatives for providing water to the Tarawa Terrace 

area. He questioned why the brief would exist if a pipeline had been installed in 1984. In referring 

to this same brief, Mr. Ensminger noted the apparant lack of standard terminology to describe the 

status of wells (e.g., inactive and active).

Response: Dr. Pommerenk acknowledged that this was a good question, and that he was 

aware of the pipeline’s construction date and his belief—that Tarawa Terrace residents received 

treated water from the Holcomb Blvd. area—was based on the assumption that water was 

supplied through the pipeline. Dr. Pommerenk indicated that, in fact, water may not have been 

flowing through the pipeline at that point in time. Dr. Walski stated that reporting terminology 

would depend on whoever recorded the information.

Statement: Mr. Ensminger questioned reports that indicate a well was taken offline due to 

contamination and later taken offline again as a result of contamination, which suggested to him 

that these wells had been placed back online during some interim period. 

5.0 Discussions and Responses to Questions from the Public  25

*Subsequent to the panel meeting, Mr. Townsend informed ATSDR that he also lived in Tarawa Terrace from 

August 25, 1965–July 30, 1967.
Response: Dr. Pommerenk commented that North Carolina required water systems to 

report when a well was completely taken out of service. He also noted that sometimes a new 

well was drilled at USMC Base Camp Lejeune and was given the same number as an old well. 

Mr. Ensminger wanted to know where and for which wells this occurred, but Dr. Pommerenk 

did not have the exact numbers. According to documents received by Mr. Faye, new wells were 

sometimes installed and given the number of the well to be replaced (e.g., new HP-645), but this 

old number did not stay in the system as the new well was given a unique permanent number. 

Statement: Mr. Ensminger asked when the eight wells at Tarawa Terrace were completely 

out of service and abandoned. 

Response: Mr. Faye acknowledged that this was a critical question to address, and that he 

was relatively certain that wells TT-23 and TT-26 were completely removed from service in 

February 1985. He expressed his belief that the remaining wells at Tarawa Terrace probably 

continued operating in 1985 and 1986. Though it was possible, he believed that it was improbable 

that Holcomb Blvd. could have supplied its original service area and that of Tarawa Terrace 

during 1985–1986. ATSDR has obtained operations records for the WTPs (e.g., monthly 

discharge rates) from 1980–1984 and 1987–1989. No such records have been located for 1985–

1986.

In response, Mr. Ensminger referred to a memorandum from 1991, which indicated that 

wells TT-23, TT-25, and TT-26 had pumps and would be able to operate; but, these wells were 

supposedly closed at this time. Mr. Faye explained that this was a note from the base responding 

to a request asking which wells were operational so that they could be sampled. According to 

U.S. Navy records, weekly water samples were collected to identify contaminants in the Tarawa 

Terrace WTP from March 1986 to March 1987. 

Statement: Mr. Ensminger asked how ATSDR could determine whether the Holcomb Blvd. 

WTP received raw water from Tarawa Terrace well fields if an auxiliary line was in place between 

Tarawa Terrace and the Holcomb Blvd. WTP in June 1985. 

Response: Mr. Faye said he had a report suggesting that Tarawa Terrace wells may have been 

used in 1989 for an extended period (throughout that year or longer) to supplement the water 

supply to the Holcomb Blvd. WTP. Dr. Walski said that the base would have had to construct 

another line that went across the systems and a raw-water line because raw and treated water 

cannot be sent through the same pipes. Mr. Faye agreed that there could have been dual pipes, but 

a freeze was reported, causing the pipes to collapse into Northeast Creek and no further details 

are known.

Mr. Maslia clarified that ATSDR recently obtained this report (dated March 1991). The 

author discussed historical aspects of various well fields, and indicated that the Tarawa Terrace 

wells supplied water to the Holcomb Blvd. WTP in 1989. 

Mr. Ensminger referred the panel and ATSDR back to the March 1985 action brief, which 

mentions the potential future use of raw water from Tarawa Terrace wells and the availability of 

water from the Holcomb Blvd. and Hadnot Point WTPs. He said that this statement suggested 

that the interconnection between Holcomb Blvd. and Hadnot Point was being opened. 

Mr. Maslia responded and noted that a previous panel, which convened in February 2005 

to address whether additional health studies would be necessary or feasible, repeatedly asked if 

the interconnection could be modeled. Past statements have suggested that the interconnection 

was for emergency purposes, but the panel wanted to know if several weeks to many months of 

interconnection could be modeled, which would require application of complex models. 

Statement: Mr. Ensminger asked how the water-distribution systems at the base compared 

against civilian water systems during the same time frame. 

Response: Mr. Maslia shared information about the water-distribution system obtained 

from field tests and USMC Base Camp Lejeune water-utility and EMD staff. In general, the 

systems are operated to maintain nearly constant pressure and water levels in the storage tanks, 

26  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
except for one controlling storage tank in each water-distribution system area. The base uses a 

completely different operational system than other water-distribution systems he has seen. The 

agency lacks specific information on diurnal demand and ATSDR is still learning more about the 

water-distribution systems at the base. Dr. Clark asked if the base currently met the Safe Drinking 

Water Act standards; Mr. Maslia said that it did. Dr. Walski stated that the base operated its waterdistribution systems more conservatively than other systems he has seen throughout the country.

Statement: Mr. Ensminger asked what results could be provided to the public about the 

flowmeters that were installed and whether the results met ATSDR’s expectations. 

Response: According to Mr. Maslia, a recommendation was made by ATSDR to install 

flowmeters throughout the three water-distribution systems being studied (Hadnot Point, 

Holcomb Blvd., and Tarawa Terrace) to quantify and understand how water flows to different 

areas and to attempt to establish demand and diurnal water-use patterns. The agency identified 

16 locations where the flowmeters should be installed. Contractors and subcontractors to the base 

installed flowmeters in December 2004 and January 2005. As of March 2005, the meters have 

been operating, but have not been successfully calibrated. ATSDR is in the process of working 

with the USMC and its contractors and subcontractors on calibrations. To date, ATSDR has not 

obtained useful nor reliable information from the flowmeters.

Statement: Mr. Ensminger asked why the calibration was being delayed. 

Response: Mr. Maslia replied that this was due to technical and resource issues. The effort 

requires that certain valves need to be shut off and would require ATSDR personnel to be onsite 

to assist with calibration procedures. ATSDR has been able to make some onsite visits to assure 

quality control associated with flowmeter calibration, but the effort to calibrate the flowmeters 

has not yet been successful.

Statement: Mr. Ensminger asked if ATSDR has received the historical documentation from 

the base necessary to conduct its activities. 

Response: Mr. Faye said that the base has provided extremely useful information regarding 

well data, UST removal documents, and RI/FS investigations at Tarawa Terrace. Regarding well data, 

ATSDR has a considerably complete record of the wells drilled at Holcomb Blvd., Hadnot Point, 

and Tarawa Terrace dating back to the early 1940s through about 1987 or 1988. These data were 

provided by the USGS. However, well data do not include operational and construction information. 

The agency has also received extensive records on additional wells completed by the base and has 

requested the locations and other data regarding these wells. He noted that the records concerning 

RI/FS and UST removal studies at Tarawa Terrace have been helpful, and that the numerous reports 

received from the base are complete. ATSDR has also requested data for the RI/FS and UST removal 

reports for Holcomb Blvd. and Hadnot Point, which the agency anticipates receiving in the near 

future.

Mr. Brynn Ashton, with the EMD, USMC Base Camp Lejeune, also responded to 

Mr. Ensminger’s question. Mr. Ashton has been heading the effort to provide requested 

documents to ATSDR. He noted that recordkeeping across the base is inconsistent and some 

information might not be as organized for some of the WTPs. However, the base commandant 

is making sure that ATSDR receives any requested records that are available.

Statement: According to Mr. Ensminger, the historical well data and water-system data 

have been extracted from the plant account records*. He questioned why this was not provided 

to ATSDR. 

5.0 Discussions and Responses to Questions from the Public  27

*Plant Account Facilities Inventory Listing of Buildings and Structures, 30 June 1990, Marine Corps Base, Camp 

Lejeune, North Carolina.
Response: Mr. Ashton replied that account data are minimal and that the base has provided 

data that are available to ATSDR. These data contain square footage of buildings, number of 

facilities, certain category codes, and years of construction. He noted that ATSDR has also been 

provided with a contact if additional information is needed and available. 

Statement: Mr. Ensminger asked how long North Carolina has required separate permits for 

multiple water systems. 

Response: Mr. Ashton was unsure, but could research the dates when the base obtained its 

permits for the systems.

Statement: Mr. Ensminger questioned if the limited number of wells originally designated 

to the Holcomb Blvd. water-distribution system could have been adequate for the demand of the 

service area. Also, regarding the flowmeters, he asked if installing choke points would increase 

the accuracy of the data. 

Response: Dr. Walski replied that this is a remaining question, but he would suggest that 

ATSDR not invest in installing choke points until the agency knew that the data required additional 

quality. 

Statement: Mr. Ensminger stated that the base’s Installation Restoration Program has accurate 

data for each well contaminated in the Hadnot Point system, and also has information on the 

contamination sources. Therefore, data are available for reconstructing the exposures to that system. 

Mr. Ensminger made additional statements throughout the 2-day meeting. During discussions 

on historical dry-cleaning operations, he reminded the group that the Vietnam War took place 

from 1965–1972, thus increasing the base population and dry-cleaning activities. He suggested 

obtaining tax records to assess the quantity of PCE used by ABC Cleaners. According to 

Mr. Ensminger, although the owner of the cleaners is deceased, depositions were conducted 

before his death and are available for review.

During panel discussions on Tarawa Terrace wells, Mr. Ensminger referenced a PCE 

detection of 215 ppb collected at the tap in February 1985, immediately before the wells were 

closed. Regarding contamination of the Hadnot Point water-distribution system, he stated that 

earlier records were available for the Hadnot Point system than for the Tarawa Terrace system. 

He cited a report conducted by the U.S. Army Hygienic Team in October 1980, which contained 

analytical data identifying chlorinated hydrocarbons at high levels in the Hadnot Point system. 

Mr. Ensminger stated that the well with the highest detected concentration (well 651, 27,000 ppb 

of VOCs) was constructed in 1972 in the back corner of a disposal lot.

In addition, Mr. Ensminger noted his skepticism of the USMC and its personnel in their 

involvement in ATSDR’s activities. He expressed concern that the base had intentionally provided 

ATSDR with incorrect water-distribution system data. ATSDR’s data indicates that Holcomb 

Blvd. provided water to all housing areas in the main area of the base throughout the 10-year 

period from 1993–2003, whereas in actuality, it was Hadnot Point that provided the water until 

August 1973. He hoped that the panel and ATSDR understood his skepticism, but he wanted them 

to understand that he and a lot of other people would like to know how their children became sick. 

28  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
6.0 Summary of Recommendations from Panel Members

and ATSDR’s Response

At the end of the meeting, the panel chair, the panel members, and ATSDR agreed that panel 

members would individually provide overall final comments, recommendations, and conclusions 

to ATSDR. Specific comments and recommentations from each panel member are provided in the 

verbatim transcript of the meeting (Volume II) on CD-ROM. The recommendations and ATSDR’s 

responses are grouped into five generalized categories.

6.1 Data Discovery

Panel members recommended that ATSDR expend additional effort and resources in the area 

of conducting more rigorous data discovery activities. To the extent possible, the agency should 

augment, enhance, and refine data it is relying on to conduct water-modeling activities.

ATSDR agrees with the panel recommendation. The agency is planning to devote additional 

resources and work with its partners and contractors to implement data discovery activities.

6.2 Chronology of Events

Panel members recommended that ATSDR focus its next efforts on refining its understanding 

of chronological events. These need to include documenting periods of known contamination, 

times when water-distribution systems were interconnected, and the start of operations of the 

Holcomb Blvd. WTP.

ATSDR agrees with the panel recommendation. The agency is planning to devote additional 

resources and work with its partners and contractors to obtain updated information so that the 

water-modeling team can refine its understanding of the chronology of contamination events.

6.3 Groundwater Modeling, Tarawa Terrace Area

Panel members made several recommendations with respect to groundwater modeling and 

associated activities for the Tarawa Terrace area, including the following:

(1) conduct sensitivity and uncertainty analyses to refine initial estimates of model 

parameter values, 

(2) determine sensitivity of model to grid/cell sizes and boundary conditions, 

(3) refine on/off cycling patterns of water-supply wells, and 

(4) conduct fate and dispersive transport analyses.

ATSDR agrees in principal with the panel recommendations. The water-modeling team is 

planning to devote significant effort in conducting sensitivity and uncertainty analyses and in 

developing a calibrated fate and dispersive transport model for the Tarawa Terrace area.

6.0 Summary of Recommendations from Panel Members and ATSDR’s Response  29
6.4 Data Analyses, Hadnot Point Area

Panel members recommended that ATSDR proceed with assessment of data to develop an 

understanding of geohydrologic and groundwater-contamination characteristics for the Hadnot 

Point area. These activities would be required before initiating additional modeling activities 

for the Hadnot Point area. Panel members also recommended that additional efforts be put into 

determining periods of interconnection between the Hadnot Point and Holcomb Blvd. waterdistribution systems.

ATSDR agrees with the panel recommendation. The agency is planning to devote additional 

resources and work with its partners and contractors to implement the panel recommendations.

6.5 Water-Distribution System Analyses

Panel members commended ATSDR for the vigor and quality of its field investigation and 

current model simulations of the water-distribution systems. Because flowmeters are already 

installed, members recommended that ATSDR proceed with collecting data from the flowmeters, 

but not initiate any additional field-testing activities. Panel members recommended that the watermodeling team consider using more simplified mixing models to quantify historical exposures to 

drinking-water supplies. (More complex modeling might be warranted if data discovery shows 

that the water-distribution systems had a greater frequency of interconnectivity.)

ATSDR agrees with the panel recommendation. The agency has concluded its waterdistribution system field-testing activities. Additionally, the water-modeling team will be using 

simplified mixing models as a first estimate of historical exposures to contaminated drinkingwater supplies.

30 Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
7.0 Acknowledgments

ATSDR would like to acknowledge the assistance and contribution of Dr. Barry L. Johnson, 

Assistant Surgeon General (retired), for his efforts in chairing the expert panel. Through his 

efforts, ATSDR has received valuable comments and recommendations from panel members that 

will assist the agency in focusing future efforts and resources in completing its analyses.

ATSDR would also like to acknowledge Jane Eggleston, Ron Spencer, and Twila D. Wilson 

of the U.S. Geological Survey, Tallahassee, Florida, for their editorial, cartographic, and pagedesign skills in preparing this document.

7.0 Acknowledgments  31

Expert Peer Review Panel Evaluating ATSDR’s 

Water-Modeling Activities in Support of the 

Current Study of Childhood Birth Defects and 

Cancer at U.S. Marine Corps Base Camp Lejeune, 

North Carolina

Analyses of Groundwater Resources and Present-Day (2004) 

Water-Distribution Systems, March 28–29, 2005

Morris L. Maslia, Editor

Appendixes A–D

Appendix A—Preliminary Draft Agenda, Charge to the Panel, and Questions and Issues for Discussion on 

Groundwater and Water-Distribution Systems

Appendix B—List of Panel Members, Presenters, and Observers

Appendix C—Curriculum Vitae for Panel Members

Appendix D—Panel Members’ Premeeting Comments

Appendix A

Preliminary Draft Agenda

Day 1 – March 28, 2005

8:30 Housekeeping Rules: Morris L. Maslia

8:35 Opening Remarks and Introduction of Chair: Tom Sinks, Acting Director, NCEH/ATSDR

8:45 Opening Statement and Presentation of Charge: Panel Chair, Dr. Barry L. Johnson, 

Assistant Surgeon General (Retired)

Introduction of Panel Members, Affiliations, and Related Experiences

9:00 Introduction of Camp Lejeune Epidemiologic Study Team: Frank Bove

Introduction of Water-Modeling Team: Morris L. Maslia

9:15 Summary of Water-Modeling Activities: Morris L. Maslia

Groundwater Modeling—Overview: Morris L. Maslia

Approach, Field Data, and Details: Robert E. Faye

10:15 Break

10:30 Panel Discussion and Answers to Questions & Issues: Groundwater

11:45 Lunch

1:00 Panel Discussion and Answers to Questions & Issues (continued) 

2:15 Break

2:30 Panel Chair Accepts Statements and Questions from Observers*

(Repeat Statement of Purpose of Panel): Barry L. Johnson

3:30 Review/Discussion of Panel Responses to Questions & Issues: Groundwater

4:00 Overview of Present-Day (2004) Water-Distribution Systems: Morris L. Maslia

5:00 Adjourn for the evening

 A1
Day 2 – March 29, 2005

8:00 Housekeeping Rules: Morris L. Maslia

8:05 Opening Statement and Re-Introduction of Panel: Barry L. Johnson, Panel Chair

8:15 Overview/Refresher of Analyses of Present-Day (2004) Water-Distribution System:

Morris L. Maslia

8:30 Panel Discussion and Answers to Questions & Issues: Water-Distribution Systems

10:00 Break

10:15 Panel Discussion and Answers to Questions & Issues: Water-Distribution Systems

12:00 Working Lunch: Address Panel Charge

1:00 Review/Discussion of Panel Responses to Questions & Issues: Water-Distribution 

Systems

1:30 Panel Chair Accepts Statements and Questions from Observers*

(Repeat Statement of Purpose of Panel): Barry L. Johnson

2:30 Panel and ATSDR Water-Modeling Staff Meet in Executive Session to Craft Panel 

Communiqué

3:30 Public Issuance of Panel Communiqué (Response to Panel Charge): Barry L. Johnson

4:00 Meeting adjourned

A2  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities

__________

*The Panel Chair will advise the public attendees of the ground rules and request questioners to supply their names 

and affiliations. All questions will be addressed to the Panel Chair, only. The Panel Chair will solicit responses from 

panel members if questions are deemed to be within the panel’s responsibility.
Charge to the Panel

The Agency for Toxic Substances and Disease Registry (ATSDR) is requesting the panel’s 

opinion with respect to the following questions. ATSDR is seeking a majority opinion with 

opposing views.

1. Will ATSDR’s approach of using “50-ft cell sizes” for groundwater modeling and “all 

pipes” networks for water-distribution system models provide sufficient detail required 

by the epidemiologic case-control study? Should courser/variable-spacing groundwatermodel grids or “skeletonized” pipe networks for water-distribution system models be 

considered in an effort to reduce the length or duration of modeling activities?

2. Is the ATSDR approach of simulating monthly conditions using water-distribution system 

models sound, or should ATSDR consider using a continuous simulation for the historical 

period (1968–1985)? If continuous simulation should be used, does this approach:

a. Increase or decrease the work effort with respect to modeling activities?

b. Increase or decrease the level of uncertainty and variability of simulated results?

3. Based on information provided by ATSDR to the panel, are there modifications or 

changes that ATSDR should consider making in its approach to modeling:

a. Groundwater resources at Camp Lejeune?

b. Present-day (2004) and historical reconstruction of water-distribution systems serving

 Camp Lejeune?

If, in the panel’s majority opinion, ATSDR should consider changes in its approach, what 

specific changes does the panel suggest?

4. Compared with other publicly documented historical reconstruction analyses, is the 

3-year project schedule for completing all historical reconstruction modeling activities 

appropriate and realistic for the amount of work and level of detail required by the 

epidemiologic study? If, in the panel’s majority opinion, ATSDR should modify the 

project schedule, what specific actions and activities does the panel suggest ATSDR take 

to modify the project schedule? 

Charge to the Panel A3
Questions and Issues for Discussion

Groundwater (includes fate and transport)

• Based on groundwater-modeling results presented, what modifications, if any, should ATSDR 

make?

• Should ATSDR use the same level of detail (50-ft cells) and expand the groundwater model to 

include the Holcomb Boulevard and Hadnot Point areas? If so, what level of increase in effort 

(time and manpower) does the panel envision for this effort?

• Rather than developing three distinct groundwater-flow models (Tarawa Terrace, Holcomb 

Boulevard, and Hadnot Point areas), should ATSDR consider developing one model covering 

all areas (i.e., simulate creeks and rivers as internal drains)?

• Should ATSDR consider using a parameter estimation (non-linear regression) approach to 

assess parameter sensitivity? If so, when should ATSDR begin this process?

• Should ATSDR consider using probabilistic analyses to assess the variability and uncertainty 

of model parameters and variability and uncertainty of contaminant concentrations at public 

supply wells? Are there public domain codes available that the panel would recommend 

using?

• How should ATSDR address the issue of lack of observed water-level data before 1974 (study 

is from 1968–1985)?

• How should ATSDR address the issue of lack of monthly groundwater-production data when 

monthly data are required for the epidemiologic study?

• Is it sufficient to use an annual average recharge or infiltration rate and assess climatic 

conditions (e.g., droughts and higher than normal precipitation) to derive monthly recharge 

rates? Are other methods or techniques available to derive monthly recharge data?

Water-Distribution Systems

• Are the distribution-system tests conducted to date and the one planned for summer 2005 

sufficient to provide ATSDR with required data for reliable calibration of present-day 

models?

• Considering the lack of household consumption data and diurnal curve characteristics, will 

applying the “district metering area (DMA)” approach using the 16 system flowmeters 

(recently installed) provide adequate and sufficient information to develop per capita 

consumption data and diurnal curve characteristics? Are panel members aware of other 

approaches that could be useful?

• Is ATSDR’s approach of developing three water-distribution system models (Tarawa Terrace, 

Holcomb Boulevard, and Hadnot Point areas) appropriate to address answers needed for the 

epidemiologic study? 

• Based on information provided to ATSDR by the U.S. Marine Corps, pipelines connecting the 

Hadnot Point water-treatment plant service area with the Holcomb Boulevard water-treatment 

plant service area were opened for emergency purposes only. Does the panel agree with the 

ATSDR approach that because of this characteristic, these two areas can be and should be 

modeled as two separate water-distribution systems?

• Should ATSDR consider using probabilistic analyses to assess the variability and uncertainty 

of: (1) water-distribution system model parameters, (2) nodal demands, and (3) system 

operations? If so, what specific methodologies would the panel suggest or recommend?

• An innovative approach for fire-flow testing (for model calibration) was employed at Camp 

Lejeune using continuous recording-pressure monitors simultaneously at several fire hydrants 

while different combinations of hydrants were flowed. Is this approach technically sound and 

beneficial?

• Is it feasible or necessary for ATSDR to simulate the complete 18-year historical period on a 

continuous basis? Will monthly simulations be adequate?

A4  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
Appendix B

Panel Members

Barry L. Johnson, PhD, FCR

 Panel Chair, Assistant Surgeon General (ret.)

 Adjunct Professor, Rollins School of 

 Public Health, Emory University; 

 Editor, Journal of Human and Ecological 

 Risk Assessment

 Atlanta, Georgia

Robert M. Clark, PhD, PE, DEE

 Environmental Engineering & Public

 Health Consultant

 Cincinnati, Ohio

David E. Dougherty, PhD

 Principal, Subterranean Research, Inc.

 Duxbury, Massachusetts

Benjamin L. Harding, PE

 Principal Engineer, Hydrosphere Resource 

 Consultants, Inc.

 Boulder, Colorado

Leonard F. Konikow, PhD, PG

 Research Hydrologist, U.S. Geological Survey

 Reston, Virginia

Eric M. LaBolle, PhD

 Scientist, University of California, 

 Davis, California

Peter Pommerenk, PhD, PE

 Project Manager, AH Environmental 

 Consultants, Inc.

 Newport News, Virginia

Vijay P. Singh, PhD, DSc, PE

 A.K. Barton Professor, Department of 

 Civil and Environmental Engineering, 

 Louisiana State University

 Baton Rouge, Louisiana

James G. Uber, PhD

 Associate Professor, Department of Civil and 

 Environmental Engineering, University of 

 Cincinnati, Ohio

Thomas M. Walski, PhD, PE, DEE

 Vice President, Engineering Bentley Systems

 Nanticoke, Pennsylvania

List of Presenters and Project 

Team Attendees

Mustafa Aral, PhD, PE

Georgia Institute of Technology

404-894-2243

maral@ce.gatech.edu

Frank Bove, DSc

Agency for Toxic Substances and

 Disease Registry (ATSDR)

404-498-0557

fjb0@cdc.gov

Robert Faye, MSCE, PE

Robert E. Faye & Associates, Inc.

706-219-1738

refaye@alltel.net

Joseph Green, MA

Oak Ridge Institute for Science & Education

404-498-0413

dgq1@cdc.gov

Morris Maslia, MSCE, PE, DEE

ATSDR

404-639-0674

mgm4@cdc.gov

Shannon Rossiter, MPH

ATSDR

404-498-0556

snr3@cdc.gov

Perri Ruckart, MPH

ATSDR

404-498-0573

afp4@cdc.gov 

Jason Sautner, MSCE

ATSDR

404-639-0674

zlc9@cdc.gov

Claudia Valenzuela, MS, Env. Eng.

Oak Ridge Institute for Science & Education

404-498-0415

cdv7@cdc.gov

 B1
List of Observers

Barbara Anderson

ATSDR

404-498-0465

bha6@cdc.gov

Brynn Ashton

U.S. Marine Corps Base Camp Lejeune

ashtonbt@lejeune.usmc.mil

Gary Campbell

ATSDR

404-498-0384

ghc1@cdc.gov

William Cibulas

ATSDR

404-498-0007

wic1@cdc.gov

Jerry Ensminger

Public Member

jmensminger@hotmail.com

Mark Evans

ATSDR

404-498-0363

mxe7@cdc.gov

Linnet Griffiths

ATSDR

404-498-0661

lig5@cdc.gov

Joel Hartsoe

U.S. Marine Corps Base Camp Lejeune

hartosejr@lejeune.usmc.mil

Carole Hossom

ATSDR

404-498-0372

cjd0@cdc.gov

Chris Mazzolini

The Daily News 

Jacksonville, North Carolina

Cmazzolini@freedomenc.com

Susan Moore

ATSDR

404-498-0505

sym8@cdc.gov

John Oh

U.S. General Accountability Office

ohj@gao.gov

Danielle Organek

U.S. General Accountability Office

organekd@gao.gov

Ken Orloff

ATSDR

404-498-0506

keo1@cdc.gov 

Alex Spiliotopoulos

S.S. Papadopoulos & Associates, Inc.

alex@sspa.com

Steven Whited

U.S. Marine Corps Base Camp Lejeune

whitedsu@lejeune.usmc.mil

Scott Williams

U.S. Marine Corps Base Camp Lejeune

williamssr@lejeune.usmc.mil

Sharon Williams-Fleetwood

ATSDR

404-498-0007

sow1@cdc.gov

David Williamson

ATSDR

770-488-1054

dxw2@cdc.gov

B2  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
Appendix C

Curriculum Vitae for Panel Members

 C1
C2  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
Robert M. Clark, PhD, PE, DEE

Education

1960 BS, Civil Engineering and Mathematics, Oregon State University

1961 BS, Mathematics, Portland State University, Oregon

1964 MS, Mathematics, Xavier University, Cincinnati, Ohio

1968 MS, Civil Engineering, Cornell University, New York

1976 PhD, Environmental Engineering, University of Cincinnati, Ohio

Work Experience

Dr. Clark is a registered engineer and worked as an environmental engineer at the U.S. 

Public Health Service and the U.S. Environmental Protection Agency (EPA) since 1961. He 

was director of the EPA Water Supply and Water Resources Division from 1985–1999. In 1999, 

he was appointed to a senior expert position at the EPA. After September 2001, Dr. Clark was 

appointed senior scientist to the EPA Water Protection Task Force, where he served until he 

retired in August 2002. He has made major contributions to the field of public health and has 

been professionally active at the national and international level. He has served as a member 

of a number of internationally recognized organizations and held national level offices for the 

American Society of Civil Engineers (ASCE) and the American Water Works Association 

(AWWA). Dr. Clark is an active researcher, having authored or coauthored more than 350 papers 

and publications and five books; he is now an independent consultant. 

Current Work

Dr. Clark is currently working on projects relating to homeland security. He is a consultant 

to Shaw Environmental and Infrastructure under a contract with the EPA. He is responsible for 

developing methodology for calibrating water-quality models in drinking-water distribution 

systems and for research on the effects of hydrodynamics on the transport and deposition of 

contaminants in networks. Dr. Clark is also a consultant to the University of Cincinnati under 

a contract with Sandia National Laboratories, which is currently reworking its risk assessment 

methodology for water-system vulnerability. He has worked with Rutgers University’s Center 

for Information Management, Integration and Connectivity to assist in the development of an 

early warning system for drinking-water utilities. In addition to his work in homeland security, 

he has worked with the U.S. Department of State to develop criteria for drinking-water treatment 

in U.S. embassies. He is working with AH Environmental Consultants, Inc., on a project with 

the U.S. Marine Corps to study volatile organic compound exposure at Camp LeJeune, North 

Carolina. 

Professional Societies and Honors

Dr. Clark is a national and international expert in the field of environmental engineering. 

He has received numerous awards including:

• ASCE, Lifetime Achievement Award (2004). Environmental and Water Resources Institute. 

In recognition of a life-long and eminent contribution to the environmental and waterresources engineering disciplines through practice, research, and public service. 

• EPA, Distinguished Service Career Achievement Award (2002). For leadership as a 

researcher and manager in protecting the Nation’s public health through his research in 

drinking water.

Curriculum Vitae for Panel Members C3
• EPA, Diversity Leadership Award (1998). Office of Research and Development. For 

enhancing the careers of ORD staff.

• ASCE, Rudolph Hering Medal (1996). For the best paper published by the Environmental 

Engineering Division.

• EPA, Gold Medal (1993). For work during the 1993 Cryptosporidia outbreak in Milwaukee, 

Wisconsin.

• AWWA, A.P. Black Award (1993). For outstanding achievements in water-supply research.

• AWWA Publication Award (1990).

• ASCE, Outstanding Research Paper (1987). From Water Resources Planning and 

Management Division.

• U.S. Public Health Service Meritorious Service Award (1983).

• Walter L. Huber Civil Engineering Research Prize (1980).

C4  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
David E. Dougherty, PhD

Education

1975 BS, Engineering, Swarthmore College 

1976 MSCE, Civil Engineering, Tufts University

1983 MA, Civil Engineering, Princeton University

1985 PhD, Civil Engineering, Princeton University, Water Resources Program

Work Experience

1994–present Principal and Cofounder, Subterranean Research, Inc.

2001–2004 Research Associate Professor, Department of Civil and Environmental Engineering,

University of Vermont

1994–2001 Associate Professor, Department of Civil and Environmental Engineering

(secondary appointment in Computer Science), University of Vermont

1990–1994 Assistant Professor, Department of Civil and Environmental Engineering,

University of Vermont

1991–1994 Engineer and Participating Guest, Lawrence Livermore National Laboratory

1986–1990 Assistant Professor, Department of Civil and Environmental Engineering,

University of California, Irvine

1981–1982 Engineer, GeoTrans, Dames & Moore

1976–1979 Engineer, Moretrench American and Ground/Water Technology

Selected Professional Activities

Committee Participation

• American Society of Civil Engineers (ACSE) Long Term Monitoring Optimization Task 

Committee (2000–present, Chair 2004–present)

• American Geophysical Union (AGU) Groundwater Technical Committee (1994–present, 

Chair during 1998–2000)

• ASCE Task Committee on Computational Issues for Groundwater Remediation 

Optimization (1994–1996)

• High Performance Computing Research Centers External Advisory Committee, Los 

Alamos National Laboratory and Oak Ridge National Laboratory (1992–1997)

• ASCE Groundwater Committee, Water Resources Planning and Management Section 

(2003–present)

• Vermont–EPSCoR, Management Committee (1996–1999)

Panel Member/Program Reviewer

• Optimization of Long Term Monitoring at Hanford Site, U.S. Department of Energy Office 

of Cleanup and Acceleration (2004)

• MODFLOW 2000, U.S. Geological Survey (1999–2000)

• Hydraulic Optimization Demonstration Project, U.S. Environmental Protection Agency 

(EPA) Technology Innovation Office (1998–1999)

• Environmental Management Science Program, U.S. Department of Energy (1999)

• Hazardous Waste Research Centers Program, EPA (1998)

• Strategic Environmental Research and Development Program, U.S. Department of Defense (1998)

Curriculum Vitae for Panel Members C5
Selected Publications

Dougherty, D.E., and Marryott, R.A., 1991, Optimal groundwater management: 1. Simulated 

annealing: Water Resources Research, v. 27, no. 10, p. 2493-2508.

Dougherty, D.E., and others, 2002, Optimization and modeling for remediation and monitoring, 

Chapter 3, in Chien, C.C., and others, eds., Environmental Modeling and Management: Theory, 

Practice, and Future Directions: Today Media, Inc.

Dougherty, D.E., and Wilson, D.A., 2003, Using on-going monitoring data and site models to 

evaluate performance of remediation systems: Proceedings MODFLOW and More 2003: 

Understanding through modeling: Golden, Colorado, International Ground Water Modeling 

Center.

Dougherty, D.E., and Young, S., 2003, Hydrologic data assimilation applied to groundwater 

plume monitoring planning: Proceedings MODFLOW and More 2003: Understanding through 

modeling, International Ground Water Modeling Center.

Eppstein, M.J., and Dougherty, D.E., 1996, Simultaneous estimation of transmissivity values and 

zonation: Water Resources Research, v. 32, no. 11, p. 3321-3336.

Eppstein, M.J., Dougherty, D.E., Troy, T.L., and Sevick-Muraca, E.M., 1999, Biomedical optical 

tomography using dynamic parameterization and Bayesian conditioning on photon migration 

measurements: Applied Optics, v. 38, p. 2138-2150.

Kosegi, J.M., Minsker, BS, and Dougherty, D.E., 2000, A feasibility study of thermal in situ 

bioremediation of dense nonaqueous phase liquids: Journal of Environmental Engineering, 

v. 126, no. 7, p. 601.

Rizzo, D.M., and Dougherty, D.M., 1994, Characterization of aquifer properties using artificial 

neural networks, Neural kriging: Water Resources Research, v. 30, no. 20, p. 483-497.

Rizzo, D.M., and Dougherty, D.M., 1996, Design optimization for multiple management period 

groundwater remediation: Water Resources Research, v., 32, no. 8, p. 2549-2561.

Rizzo, D.M., and Dougherty, D.M., 2000, Artificial neural networks in subsurface 

characterization, in Govindaraju, R.S., and Rao, A.R., eds., Artificial Neural Networks in 

Hydrology: Kluwer.

Rizzo, D.M., and Dougherty, D.M., and Yu, M., 2000, An Adaptive Long-Term Monitoring 

and Operations System (aLTMOsTM) for optimization in environmental management: ASCE 

2000 Joint Conference on Water Resources Engineering and Water Resources Planning and 

Management, Minneapolis, Minnesota.

Task Committee on the State of the Art in Long-Term Groundwater Monitoring Design of the 

Environmental and Water Resources Institute, 2003, Long-term groundwater monitoring: The 

State of the Art: American Society of Civil Engineers, 103 p.

Xue, G., Lillys, T.P., and Dougherty, D.E., 2000, Computing the minimum cost pipe network 

interconnecting one sink and many sources: SIAM J. Optimization, v. 10, no. 1, p. 22.

Yu, M., and Dougherty, D.E., 2000, Modified total variation method for 3-D electrical resistance 

tomography inverse problems: Water Resources Research, v. 36, no. 7, p. 1653.

C6  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
Benjamin L. Harding, PE

Education

1971 BS, Civil Engineering, University of Colorado

Memberships and Registrations

• Registered Professional Engineer, State of Colorado, 1979

• Member, American Society of Civil Engineers

• University of Colorado, Department of Civil, Environmental and Architectural Engineering, 

Professional Advisory Board Member, 1995–2003; Chair, 2000–2002

Work Experience

Mr. Harding has more than 35 years of diverse experience in water-resources engineering. 

For more than 20 years he has focused his practice on the design, development, and use of 

hydrologic and river/reservoir system models, decision support systems, hydraulic models, 

water-quality models, GIS, and databases. This experience includes over 20 years of project 

management, successfully directing engineers, scientists, and programmers in these areas. 

Mr. Harding is fluent or has a working knowledge of several computer languages and has 

experience with the management of software and database development projects. 

Mr. Harding’s work has been reported in papers published in Water Resources Research, 

Water Resources Bulletin and Industrial Wastes.

Project Experience

Colorado River Water Availability. Project manager and lead engineer for development of 

probabilistic estimates of water availability on the Colorado River under different assumptions 

regarding operating rules and legal interpretations of compacts.

Water Acquisition Study. Project manager and lead engineer for evaluation of water 

acquisition as a means of maintaining habitat for endangered fish in a water-short river system. 

This analysis involves both engineering and institutional factors.

Central Oahu Water-Distribution System. In support of litigation, project manager, and 

chief engineer for analysis of the fate and transport of pesticides in the water-distribution system 

of Honolulu, Hawaii. Performed and directed water-distribution fate and transport modeling. 

Developed and utilized Monte Carlo risk-assessment methods to quantify human intakes of 

pesticides and associated risk of cancer. Directed the development of GIS databases used for 

analysis of water demand, development of water-distribution models, and geocoding of exposure 

locations. Provided expert testimony in deposition and at trial in Federal court. Trial is ongoing.

Snowmaking Water Quality Studies. Project engineer for design of a field sampling program 

for hydrology and water quality of meltwater from artificial snow, and associated model studies.

Redlands Toxic Chemical Exposure Analysis. In support of litigation, project manager and 

chief engineer for analysis of the fate and transport of toxic chemicals in the water-distribution 

system of Redlands, California. Performed and directed water-distribution fate and transport 

modeling to reconstruct historical conditions at different spatial and temporal scales. Developed 

and utilized Monte Carlo risk assessment methods to quantify human intakes of contaminants and 

associated risk of cancer. Provided expert testimony at deposition. Case is ongoing.

Curriculum Vitae for Panel Members C7
Burbank TCE Exposure Analysis. In support of litigation, project manager and chief 

engineer for analysis of the fate and transport of TCE in the water-distribution system of Burbank, 

California. Performed and directed water-distribution fate and transport modeling to reconstruct 

historical conditions at different spatial and temporal scales. Provided expert testimony at 

deposition. Case was settled.

Phoenix TCE Exposure Analysis. In support of litigation, project manager and chief engineer 

for analysis of the fate and transport of TCE in the water-distribution systems of Scottsdale 

and Phoenix, Arizona. More than 10 hydraulic and water-quality models of both systems were 

constructed and calibrated. These models were run over a study period spanning 20 years or 

more. Mr. Harding managed and conducted the development of a comprehensive historical 

spatial database of parcel and land use data, beginning with current land use data and developing 

historical data from aerial photographs and other sources. These databases were used to estimate 

historical water use, to develop water-distribution models, and to geocode exposure locations. 

Provided expert testimony at deposition and at trial in state court. Case resolved at trial.

Selected Publications

Grayman W., Clark R.M., Harding B.L., Maslia, M., and Aramini, J., 2004, Reconstructing 

Historical Contamination Events, in Mays, L., ed., Water Supply Systems Security: 

McGraw-Hill.

Harding, B.L., 1999, Evaluation of Historical Concentrations of Dissolved Contaminants in the 

Burbank Water Distribution System: February 15, 1999.

Harding, B.L., 1999, Evaluation of Historical Concentrations of Dissolved Contaminants in the 

Burbank Water Distribution System: Supplemental Report, May 7, 1999.

Harding, B.L., and Grayman, W., 2002, Historical Reconstruction of Contamination in a 

Distribution System Incorporating Uncertainty: Proceedings of the 12th Conference of the 

International Society of Exposure Analysis (ISEA) and 14th Conference of the International 

Society for Environmental Epidemiology (ISEE), August, 2002, Vancouver, British Columbia, 

Canada.

Harding, B.L., and Grayman, W., 2003, Movement of Contaminants in the Central Oahu 

Distribution System.

Harding, B.L., and T.M. Walski, 1999, Long Time-Series Simulation of Water Quality in 

Distribution Systems: Proceedings of the 26th Annual Water Resources Planning and 

Management Conference, ASCE.

Harding, B.L., and T.M. Walski, 2000, Long Time-Series Simulation of Water Quality in 

Distribution Systems: ASCE, Journal of Water Resources Planning and Management, v. 126, 

no. 4.

Walski, T.M., and Harding, B.L., 1997, Historical TCE Concentrations in Drinking Water in 

the Maryvale Area of West Central Phoenix, Arizona: Lofgren, et al., versus Motorola, et al., 

Superior Court, Maricopa County, Arizona, July 31, 1997. 

Walski, T.M., and Harding, B.L., 1997, Historical TCE Concentrations in Drinking Water in 

South Scottsdale and Adjacent Areas of Phoenix, Arizona: Lofgren, et al., versus Motorola, 

et al., Superior Court, Maricopa County, Arizona, January 13, 1997.

C8  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
Barry L. Johnson, PhD, FCR

Education

1960 BS, Electrical Engineering, University of Kentucky, Lexington

1962 MS, Electrical Engineering (minor in mathematics), Iowa State University, Ames

1967 PhD, Electrical Engineering (minors in biomedical engineering, applied 

mathematics, and physiology), Iowa State University, Ames

Work Experience 

1986–1999 Assistant Administrator, Agency for Toxic Substances and Disease Registry

1999 Adjunct Professor, Rollins School of Public Health, Emory University

1972–1986 Director, Division of Biomedical and Behavioral Science, National Institute for 

Occupational Safety and Health

1970–1972 Research Scientist, U.S. Environmental Protection Agency

1962–1970 Electrical Engineer, neurotoxicologist, U.S. Public Health Service 

Professional Societies

• Environment and Health Committee, Physicians for Social Responsibility

• National Academy of Sciences’ Board on Environmental Studies and Toxicology

Editorial Boards

• Journal of Industrial Health and Toxicology, 1983–1999 

• Archives of Environmental Health, 1980–1994 

• NeuroToxicology, 1978–1993 

• Risk Analysis, 1987 

• Clean Technology and Environmental Sciences, 1990–present 

• Contaminated Soils, 1991–present 

• International Journal of Occupational and Environmental Medicine, 1994–present 

• Editor-in-Chief, Journal of Human and Ecological Risk Assessment, 1999–present 

Curriculum Vitae for Panel Members C9
Publications

Johnson, B.L., 1987, The Prevention of Neurotoxic Illnesses in Working Populations: Wiley & 

Sons, London.

Johnson, B.L., 1990, Advances in Neurobehavioral Methods in Environmental and Occupational 

Health, Lewis Publishers, Chelsea, Michigan.

Johnson, B.L., 1992, National Minority Health Conference: Focus on Environmental 

Contamination, Princeton Scientific Publishers, Princeton, New Jersey.

Johnson, B.L., 1994, Behavioral Toxicology: Department of Health and Welfare, Washington, 

D.C.

Johnson, B.L., 1994, Hazardous Waste and Public Health, Princeton Scientific Publishing, 

Princeton, New Jersey.

Johnson, B.L., 1999, Human Health Impact of Hazardous Waste, Lewis Publishers, Boca Raton, 

Florida.

Johnson, B.L., 2005, Environmental Policy and Public Health Practice (submitted for 

publication).

Authored numerous peer reviewed papers. A list is available upon request.

C10 Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
Leonard F. Konikow, PhD, PG

Education

1966 BA, Geology, Hofstra University, Hempstead, New York

1969 MS, Geology, Pennsylvania State University

1973 PhD, Geology, Pennsylvania State University

Registration

• Professional Geologist, Pennsylvania (1996–present)

Work Experience

1980–present Project Chief, Water Resources Division, U.S. Geological Survey, Research 

Project “Digital modeling of transport in saturated zone”

1978–1980 Ground Water Branch, U.S. Geological Survey, Reston, Virginia

1974–1978 Project Chief, Research Project “Solute Transport in Ground Water,” 

U.S. Geological Survey, Central Region, Lakewood, Colorado

1972–1974 Project Chief, Subsurface Waste Investigations, U.S. Geological Survey, 

Lakewood, Colorado

1969–1971 Research assistant, Pennsylvania State University

Other Experience

Instructor and lecturer at:

7/66–9/66 Geology Department, Hofstra University, Hempstead, New York

1/69–6/69 Geology Department, Pennsylvania State University

1991 & 1992 Department of Environmental Sciences, University of Virginia; Department of

Geological Sciences, Stanford University

Professional Societies

•American Geophysical Union (AGU) (1970–present; elected Fellow, 2001)

• AGU Spring Meeting Program Chairman for Hydrology (1984–1987)

• Groundwater Committee (1977–1986; Chairman, 1980–1982)

• Geological Society of America (1974–present; Fellow since 1990)

• Management Board, Hydrogeology Division, Geological Society of 

America (GSA) (1991–1995)

• Chairman, Hydrogeology Division, GSA (1993–1994)

• International Association of Hydrogeologists (IAH) (1985–present)

• Chairman, U.S. National Chapter, IAH (2001–2004)

• U.S. Executive Committee and Liaison with AGU (1986–1990)

• Association of Ground Water Scientists and Engineers (AGWSE) (Technical Division of 

National Ground Water Association) (1990–present)

• AGWSE—Board of Directors (1996–2000)

• American Institute of Hydrology (Certified as Professional Hydrogeologist) (1991–present)

• California Groundwater Resources Association (2002–present)

Curriculum Vitae for Panel Members C11
Honors and Awards

• Birdsall Distinguished Lecturer (1985–86), GSA, Hydrogeology Division

• M. King Hubbert Science Award (1989), National Ground Water Association

• O.E. Meinzer Award (1997), GSA, Hydrogeology Division

• C.V. Theis Award (1998), American Institute of Hydrology

• Distinguished Service Award (1999), U.S. Department of Interior

• Award for Distinguished Service (2000), GSA, Hydrogeology Division

• Elected as Fellow (2001), AGU

• President’s Award (2001), IAH

Selected Professional Activities

• Rocky Mountain Arsenal (Colorado) Technical Review Committee (1975–77)

• Associate Editor, Water Resources Research (1981–1984)

• National Research Council, Panel on Groundwater Contamination (1981–1982)

• National Research Council, Water Science & Technology Board, Committee on GroundWater Modeling Assessment (1987–1989)

• National Research Council, Waste Isolation Plot Plant Committee (1989–1997)

• Peer Review Panel, U.S. Environmental Protection Agency, Environmental Monitoring 

Systems Lab, Las Vegas, Nevada (1991)

• National Science Foundation, Review Panel for Hydrologic Sciences and interim staff 

assistant (1992)

• Member of Modeling Project Subcommittee, Science Advisory Board, U.S. Environmental 

Protection Agency (1993)

• Editorial Board, Ground Water Journal (1993–1995)

• Adviser to U.S. AID project studying seawater intrusion in Gaza and Morocco (1994–1997)

• National Research Council, Hydrogeology/Water Management Peer Review Panel for 

U.S. AID (2000)

• National Research Council, Committee on Principles and Operational Strategies for Staged 

Repository Systems (2001–2002)

• Farvolden Distinguished Lecturer, University of Waterloo, Ontario (2002)

Publications

Author or coauthor of numerous articles in peer-reviewed journals, government publications, 

conference proceedings, book chapters, and talks given at professional society meetings (detailed 

list available on request). 

C12  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
Eric M. LaBolle, PhD

Education

1999 PhD, Hydrologic Science, University of California, Davis

1993 MS, Civil and Environmental Engineering, University of California, Davis

1987 BS, Environmental Engineering (minor in Water Resources), Humboldt 

State University, Arcata, California

Registration

• California Engineer-in-Training license

• Occupational, Safety, and Health Administration hazardous-waste site management 

certificate, 29 CFR 1910.120, not current

Work Experience

1999–present Researcher, Hydrologic Sciences, University of California, Davis

In conjunction with the U.S. Geological Survey (USGS), developing a random 

walk component for the MODFLOW suite of groundwater flow and transport 

codes, GWT-2000. Studying the role of heterogeneity in our ability to monitor 

for natural attenuation. Using high-performance computational clusters to study 

the role of uncertainty and variability in groundwater and water-distribution 

system flow and contaminant transport on perchlorate exposure history and 

associated health risks in Rancho Cordova. Conducted verification of Integrated 

Groundwater and Surface Water Model. Mentoring and supervision of graduate 

and postdoctoral students. 

1994–present Hydrogeologist, Independent Consultant

Water resources management and planning, groundwater-banking/conjunctiveuse, model peer review, environmental simulations, groundwater-flow and 

contaminant transport, software development, and expert witness/litigation 

support for environmental contamination cases of the South Lake Tahoe Public 

Utilities District (methyl-tertiary-butyl ether (MTBE), settled); Citizens for a 

Better Environment (MTBE, settled); City of Santa Monica (MTBE, settled); City 

of Dallas versus Explorer Pipeline, et al. (MTBE, settled); City of Dinuba (MTBE, 

settled); Methanex versus the United States of America (MTBE, in litigation); and 

City of Modesto (PCE, in litigation). Additional clients include Coachella Valley 

Water District, Azurix-Madera, and iAqua-Dallas.

1993–1998 Postgraduate Researcher, Hydrologic Sciences, University of California, Davis

Evaluated aquifer remediation strategies for Lawrence Livermore National 

Laboratory, Livermore, California, using models of flow and transport in highresolution three-dimensional geostatistical characterizations of the alluvial-fan 

hydrostratigraphy. Investigated roles of diffusion in subsurface transport and 

remediation. Developed the theory of diffusion processes in composite media, 

a generalization of standard diffusion theory. Developed new computational 

methods and software for simulating transport in porous media.

Curriculum Vitae for Panel Members C13
Research Assistant

1991–1993 Hydrologic Sciences, University of California, Davis

1989–1990 Humboldt State University, Arcata, California

1989–1991 Project Engineer, Winzler & Kelly, Eureka, California

Conducted analyses and provided recommendations for water- and sewersystems upgrades, allocation of water resources, negotiations for purchase 

of water, and management of finances related to public utilities. Developed 

specifications for water-telemetry system. Developed initial design specifications 

for wastewater-effluent irrigation system. Collaborated in managing construction 

of three wastewater-treatment systems. Participated in remedial investigations of 

hazardous-waste sites. 

1987–1988 Hydrologist, Golder Associates, Redmond, Washington

Developed and applied stochastic hydrologic software to assess risk to radiation 

exposure from proposed geologic repositories for high-level radioactive wastes 

in Deaf Smith County, Texas, and Yucca Mountain, Nevada. Modeled fate 

and transport of radionuclides in proposed geologic repositories for high-level 

radioactive wastes. Collaborated in developing and verifying finite-element 

fracture-flow software. Participated in hydrogeologic characterizations and 

remedial investigations of hazardous-waste sites. 

1994–2003 Guest Lecturer, Hydrologic Sciences, University of California, Davis

Professional Societies and Awards

• Year 2000 Universities Council on Water Resources Award for Outstanding Water Resources

• PhD dissertation in the fields of natural science and engineering

• American Geophysical Union

• National Groundwater Association

• Groundwater Resources Association of California

• International Association of Hydrogeologists

Publications

• Approximately 25 journal articles, special papers/reports, and consulting report

• More than 30 abstracts and conference presentations 

• PhD dissertation

• Approximately 10 proposals

C14  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
Peter Pommerenk, PhD, PE

Education

1989 MS Aerospace Engineering, Universität der Bundeswehr München

1996 MS Environmental Engineering, Old Dominion University

2001 PhD Environmental Engineering, Old Dominion University

Memberships and Registrations

• Member, American Water Works Association

• Registered Professional Engineer, Virginia

Work Experience

2002–present Specializes in water quality and treatment, including process design studies 

(bench, pilot and full-scale plant studies), optimization of new and existing raw

water supply, treatment and water-distribution system facilities for compliance

purposes, impact assessment of pollutant discharges on ambient water quality

and computer-aided modeling of physicochemical processes and transport in

aqueous systems. As a project manager with AH Environmental Consultants, 

Inc., his projects have included:

Distribution System Hydraulic and Water Quality Modeling for City of 

Goldsboro, North Carolina; Fort Eustis, Virginia; Fort Story, Virginia, and Naval 

Service Warfare Center, Carderock Division, Maryland.

2002–2004 Served as project manager for completion of distribution system hydraulic and 

water-quality models. Tasks performed include: Development of water-quality 

sampling and hydraulic monitoring plans, model calibration, development of 

scenarios to identify solutions to distribution system water-quality problems.

U.S. Marine Corps Base Camp Lejeune, North Carolina. 

• Performed feasibility studies and preliminary design and developed cost estimates for the 

replacement of five water-treatment facilities with membrane nanofiltration, lime softening, 

and ion exchange plants. 

• Designed and conducted an investigative study to determine the source of trihalomethane 

precursor material at a well field at the U.S. Marine Corps Air Station New River and 

developed well utilization schedules to minimize disinfection byproduct formation. 

• Developed and conducted a study to evaluate the effect of pH adjustment and corrosion 

inhibitor addition on the leaching of lead from brass faucets. This work included benchscale tests and chemical equilibrium modeling of the effects of process chemistry on the 

solubility of lead phosphate and carbonate minerals. 

• Developed and completed study to minimize disinfection byproduct formation in the 

consecutive water system at the Rifle Range. 

• Developed raw-water master plan for 80 groundwater wells at the base. 

• Provided technical support to the base for the epidemiological study being conducted by 

the Agency for Toxic Substances and Disease Registry. 

U.S. Army Corps of Engineers, Washington Aqueduct Division. Developed and conducted a 

full-scale study to determine the effect of backwash water recycling on granular media filtration 

efficiency.

Curriculum Vitae for Panel Members C15
City of Virginia Beach, Virginia. As project manager developed long-term plan for alternative 

water supply, including conceptual design and cost estimation for seawater desalination and 

surface-water treatment.

U.S. Army Corps of Engineers, Washington Aqueduct Division. Evaluated alternative filter 

aids for the McMillan plant in a pilot- and full-scale study to minimize the adverse impacts 

of algae blooms in uncovered reservoirs on filtered water-effluent turbidity and particle-size 

distribution.

Naval Facilities Engineering Command, Atlantic Division. Performed sanitary surveys for 

overseas water-treatment facilities at the Naval Station Roosevelt Roads, Puerto Rico; the Naval 

Station Rota, Spain; the Naval Station Guantanamo Bay, Cuba; the Naval Support Activity 

Bahrain; and the Naval Support Activity Souda Bay, Greece.

Army National Guard, Camp Atterbury, Indiana. Evaluated the influence of water-softening 

strategies on the leaching of lead from brass faucets. This work included bench-scale tests and 

chemical equilibrium modeling of the effects of process chemistry on the solubility of lead.

City of Goldsboro, North Carolina. Responsible for providing technical support to the city on 

numerous projects including evaluation of alternatives to upgrade or replace the existing Neuse 

River intake; safe yield analysis of the Neuse River; and evaluation of trihalomethane control 

alternatives, tracer studies, and computational fluid dynamics analysis of the clearwell.

Recent Publications and Presentations

Pommerenk, P., Hiltebrand, D.J., Theiss, R.J., and Brashear, K., 2001, Use of CFD modeling 

and tracer studies to select the point of ammonia addition for chloramines, in Proceedings 

2001 Water Quality Technology Conference: Nashville, Tennessee, American Water Works 

Association.

Pommerenk, P., and Schafran, G.C., 2002, Effects of prefluoridation on removal of particles and 

organic matter: Journal of the American Water Works Association, v. 94, no. 2, p. 99–108.

C16  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
Vijay P. Singh, PhD, DSc, PE

Education

1967 BS, Engineering, U.P. Agriculture, University, India

1970 MS, Engineering, University of Guelph, Canada

1974 PhD, Civil Engineering, Colorado State University, Ft. Collins

1998 DSc, Engineering, University of the Witwatersrand, Johannesburg, South Africa

Professional Registration

• PE (Louisiana) since 1973

• PH (American Institute of Hydrology) since 1984

Work Experience

1999–present Employment: Arthur K. Barton Endowed Professor

1981–1999 Professor of Civil Engineering and Coordinator of Water Resources Program

1983–1985 Director (Acting), Louisiana Water Resources Research Institute

l978–1981 Louisiana State University; Associate Professor of Civil Engineering, Mississippi 

State University

1977–1978 Associate Research Professor of Civil Engineering, George Washington University

1974–1977 Assistant Professor of Hydrology, New Mexico Institute of Mining and Technology

Other Experience

Visiting Professor

• Department of Environmental Engineering and Physics, Univ. of Basilicata, Italy (1990, 1997)

• Department of Water Resources Engineering, Lund University, Sweden (1994)

• Swiss Federal Institute of Technology, Switzerland (1990, 1992, 1994, 1995, 1997)

• Vrije Universiteit Brussels, Belgium (1988)

• Water Resources Development Training Centre, University of Roorkee, India (1997)

• University of Technology, Graz, Austria (1998)

• University of Technology, Vienna, Austria (1998)

• U.S. Department of Interior, Denver, Colorado (1999)

• Nanyang Technological University, Singapore (2001)

• Senior Research Engineer, U.S. Army Engineer Waterways Experiment Station, Vicksburg, 

Mississippi (1982, 1984, 1985, 1986, 1995)

Consultant to local, state, national, and international organizations on 21 projects

Honors, Awards, and Recognition

• Earned 35 awards, including 2 best paper, 10 books, 3 service, 3 scholarship, teacher 

of the year, researcher of the year; outstanding service award from Italian CNR-IRPI, 

Fulbright Scholar Award, International Man of the Year Award, 20th Century Award for 

Achievement, DSc Degree, Research Fellow Award, Distinguished Faculty Award, The Brij 

Mohan Distinguished Professor Award, Achievement in Academia Award, and James M. 

Todd Technological Medal, 2001 Honor Alumnus Award, Certificate of Appreciation for 

Dedicated Service, and Arid Lands Hydraulic Engineering Award; 9 honors, including 6 

fellowships in ASCE, AWRA, I.E., IWRS, IAH and ISAE, one I.H.D. endowment lecture 

award, and U.S.-India exchange scientist award; and included in 14 WHO’s WHO.

Curriculum Vitae for Panel Members C17
Professional Academies and Societies

• Academician, Georgia Fazisi Academy, Republic of Georgia

• Fellow

Amer. Inst. of Hydrology, Senior Vice Pres.1999–2000; Pres., Louisiana Chap. 1987–94

American Water Resources Association (AWRA)

American Society of Civil Engineers (ASCE)

Indian Association of Hydrologists (IAH), Vice President, 1995–present

Institution of Engineers (IE) (India)

Indian Society of Agricultural Engineers (ISAE)

Indian Water Resources Society (IWRS)

• Member

American Geophysical Union

International Association for Hydraulic Research

International Association of Hydrological Sciences

U.S. Committee of the International Commission on Irrigation and Drainage

Indian Association of Soil and Water Conservationists

British Hydrological Society

Georgia Academy of Sciences, Republic of Georgia

Hazard Forum

Russian Academy of Water Management Sciences, Russian Federation

Sigma Xi

• Served on two national panels and member of 28 professional society committees

The University of Guelph Alumni Association

Colorado State University Alumni Association

Other Experience

Member of editorial boards of 14 journals including: Stochastic Hydrology and Hydraulics 

(1987–present), Water Resources Management (1986–present), Irrigation Science (1988–present), 

Agricultural Water Management (1988–present), Hydrology (1980–present), Natural Hazards 

(1987–1991), Hydroelectric Energy (1986–1992), Hydrological Processes (1994–present), 

Journal of Hydrologic Engineering, ASCE (1995–present), Environmental Fluid Mechanics 

(2000–present), International Journal of Sedimentation Research (2001–present), Acta Geophysica 

Polenica (2001–present), New Global Development: International Journal of Comparative Social 

Welfare (2001–present), and Water Engineering and Research (2000–present).

Editor-in-Chief, Water Science and Technology Library Book Series, Kluwer Academic 

Publishers (1991–present); Member of Editorial Board (1988–1991), Kluwer Academic 

Publishers; Member, National Board of Advisors (1982–present).

Guest editor of special issues of Stochastic Hydrology and Hydraulics on Risk and 

Reliability Analyses (v. 4, 1990; v. 5, 1991); special issue of Irrigation Science on Advances 

in Surface Irrigation (1993); two special issues of Hydrology Journal of Indian Association of 

Hydrologists on Hydrology and Water Resources (v. XVII, no. 1 & 2, 1994).

External examiner of 20 PhD dissertations abroad. Referee for proposals submitted to 

National Science Foundation, Canada’s NRCSE, and Australia’s ARC; referees articles submitted 

to 30 journals and technical contributions of U.S. Department of Agriculture and U.S. Geological 

Survey. Participated in 24 keynote speeches; lecturer at 19 courses; 200 invited talks/seminars 

organized 12 international conferences; chaired sessions at 28 international conferences; and 

assisted in organization of 23 international conferences.

Publications

Authored 11 books, 48 book chapters, 5 book reviews, 318 journal articles, 180 conference 

papers, and 70 technical reports. Edited 33 books.

C18  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
James G. Uber, PhD

Education

1983 BS, Civil Engineering, Bradley University, Peoria, Illinois

1985 MS, Environmental Engineering, University of Illinois at Urbana-Champaign

1988 PhD, Environmental Engineering, University of Illinois at Urbana-Champaign

Work Experience

1997–present Associate Professor; University of Cincinnati, Department of Civil and Environmental 

Engineering

1990–1997 Assistant Professor; University of Cincinnati, Department of Civil and Environmental 

Engineering

1988–1990 Assistant Professor; University of Alabama-Huntsville, Department of Mechanical 

Engineering

Advised/sponsored 19 graduate students and 3 postdoctoral candidates

Professional Research Activities

Annual Symposium on Water-Distribution Systems Analysis. Initiated by Uber in 1999 and 

organized annually, this symposium attracts 40–60 papers per year from a broad international 

audience, and is the primary North American outlet for theoretical developments and applications 

of systems analysis to water-distribution systems. 

Interdisciplinary Research to Broaden Understanding About Drinking Water Quality. 

Collaborative work with epidemiologists and water-quality scientists (C. Moe and P. Tolbert, 

Emory University; J. Eisenberg, University of California, Berkeley; D. Moll, Center for Disease 

Control) is estimating the microbial and chemical health risks associated with drinking water, 

especially the contribution of water-distribution systems. Collaborative work with electrical and 

controls engineers (M. Polycarpou, University of Cyprus; M. Bryds, University of Birmingham, 

United Kingdom) initiated the first work on automatic feedback control of water quality in 

spatially distributed distribution systems. 

Computational Tools for Analysis and Improvement of Water Quality in Distribution 

Systems. Development and application of the first general simulation tool to integrate multispecies water-quality dynamics with water-distribution system hydraulic models. Participated 

in initial water-security research to design and analyze monitoring and surveillance systems to 

mitigate the risks associated with intentional contamination of drinking water. Developed first 

framework to quantify microbial health risk associated with pathogen intrusion in drinking-water 

distribution systems, by linking disinfectant residual and pathogen inactivation kinetics with 

network hydraulic models and Monte-Carlo sampling.

Field-Methods for Measurement of Water Quality in Distribution Systems. Designed and 

conducted improved field-scale tracer tests using continuous monitoring to assess and improve 

the accuracy of water-distribution system water-quality models.

Collaborated with numerous researchers from Sandia National Lab, Center for Disease 

Control, and several universities.

Curriculum Vitae for Panel Members C19
Publications

Boccelli, D.L., Shang, F., Uber, J.G., Orcevic, A., Moll, D., Hooper, S., Maslia, M., Sautner, J., 

Blount, B., and Cardinali, F., 2004, Tracer tests for network model calibration, in Proceedings, 

ASCE/EWRI World Water and Environmental Resources Congress, Salt Lake City, Utah.

Boccelli, D.L., Tryby, M., Uber, J.G., Rossman, L.A., Zierolf, M.L., and Polycarpou, M.M., 1998, 

Optimal scheduling of booster disinfection in water distribution systems: ASCE Journal of 

Water Resources Planning and Management, v. 124, no. 2, p. 99–110.

Bush, C., and Uber, J., 1998, Sampling design methods for water distribution model calibration, 

ASCE Journal of Water Resources Planning and Management, v. 124, no. 6, p. 334–344.

Murray, R., Janke, R., and Uber, J., 2004, The threat ensemble vulnerability assessment (teva) 

program for drinking water distribution system security, in Proceedings, ASCE/EWRI World 

Water and Environmental Resources Congress, Salt Lake City, Utah.

Polycarpou, M.M., Uber, J.G., Wang, Z., Shang, F., and Brdys, M., 2002, Feedback control of 

water quality: IEEE Control Systems Magazine, v. 22, no. 3, p. 68–87.

Propato, M., and Uber., J.G., 2004, A linear least squares formulation for operation of booster 

disinfection systems: ASCE Journal of Water Resources Planning Management, v. 130, no. 1.

Propato, M., and Uber, J.G., 2004, Vulnerability of water distribution systems to pathogen 

intrusion: How effective is a disinfectant residual?: Environmental Science and Technology, 

v. 38, no. 13, p. 3713–3723. 

Shang, F., Uber, J.G., and Polycarpou, M.M., 2002, A particle backtracking algorithm for water 

distribution system analysis: ASCE Journal of Environmental Engineering, v. 128, no. 5, p. 

441–450.

Uber, J., Janke, R., Murray, R., and Meyer, P., 2004, Greedy heuristic methods for locating 

water quality sensors in distribution systems, in Proceedings, ASCE/EWRI World Water and 

Environmental Resources Congress, Salt Lake City, Utah.

Uber, J., Shang, F., and Rossman, L., 2004, Extensions to epanet for fate and transport of multiple 

interacting chemical or biological components, in Proceedings, ASCE/EWRI World Water and 

Environmental Resources Congress, Salt Lake City, Utah.

C20 Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
Thomas M. Walski, PhD, PE, DEE

Education

1972 BA, King’s College, Wilkes-Barre, Pennsylvania

1979 MS, PhD, Vanderbilt University, Nashville, Tennessee

Registration

• Professional Engineer, Pennsylvania, Mississippi

• Certified Water and Wastewater Operator, Pennsylvania

Work Experience

2004–present Senior Advisory Product Manager, Bentley Systems, Inc.

2000–2004 Vice President Engineering, Haestad Methods, Inc.

1996–1999 Engineering Manager, Pennsylvania American Water Company

1992–1996 Associate Professor, Environmental Engineering, Wilkes University

1989–1992 Executive Director, Wyoming Valley Sanitary Authority

1987–1989 Operation Manager, Austin, Texas, Water & Wastewater Utility

1975–1987 Environmental Engineer, U.S. Army Corps of Engineers

Other Experience

Served on several committees preparing/editing American Water Works Association 

(AWWA), American Socity of Civil Engineers (ASCE), and Water Environment Federation 

publications

Former editor, Journal of Environmental Engineering

Expert Witness, 1995–1997, Lofgren, et al., versus Motorola, et al.

Expert Panel, 1998, Modeling Water Quality in Dover Township, 

 New Jersey Water-Distribution System

Professional Society Memberships

• Has served on numerous professional committees including:

• AWWA, Fire Protection Committee (past chair)

• ASCE

Systems Committee (past chair)

Water Supply (past chair)

Task Committee on Water System Rehabilitation (past chair)

Journal of Environmental Engineering (editor)

• Water Environment Federation

Panel Members’ Premeeting Comments C21
Publications

Authored several books and over 100 journal papers and conference presentations. Authored 

water-quality modeling publications and presentations, including:

Walaski, T.M., 1991, Understanding Solids Transport in Water Distribution Systems,” in

Proceedings Water Quality Modeling in Distribution Systems: Cincinnati, Ohio.

Walaski, T.M., 1999, Modeling TCE Dynamics in Water Distribution Tanks: ASCE Water 

Resources Planning and Management Conference, Tempe, Arizona.

Walaski, T.M., 2001, Analysis of Water Quality and Pumping Energy in a Small Water System: 

ASCE Environmental and Water Resources Institute Conference, Orlando, Florida.

Walaski, T.M., 2002, Identifying Monitoring Locations in a Water Distribution System Using 

Simulation and GIS: American Water Works Association IMTech Conference, Kansas City, 

Missouri.

Walaski, T.M., and Draus, Steve, undated, Using Pipe Network Models to Help Solve Water 

Quality Problems in Water Distribution Systems.

Walaski, T.M., and Darus, Steve, 1994, An Evaluation of Water Quality at Fort Monmouth, New 

Jersey, using the EPANET Model: U.S. Army Corps of Engineers, Waterways Experiment 

Station, MP EL-95-6.

Walaski, T.M., and Draus, Steve, 1996, Predicting Water Quality Changes During Flushing: 

American Water Works Association Annual Convention, Toronto.

Walaski, T.M., and Hardin, Ben, 1999, Long Time-Series Simulations of Water Quality in 

Distribution Systems: ASCE Water Resources Planning and Management Conference, Tempe, 

Arizona. Also accepted for Journal of Water Resources Planning and Management.

Walaski, T.M., and Lutes, Teresa, 1994, Low Pressure Problems Caused by Hydraulic Transients: 

Journal of American Water Works Association, v. 86, no. 12, p. 24.

Walaski, T.M., and Male, James, 1990, Troubleshooting Water Distribution System Problems: 

Lewis Publishers.

C22  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
Appendix D

Panel Members’ Premeeting Comments

Robert M. Clark, PhD, PE, DEE

Comments

All of the data presented, including water-distribution system, calibration studies, and demand 

information, is collected for the configuration and operation of the current system. This work is 

very impressive and uses state-of-the-art technology and techniques. Having conducted a number 

of modeling and calibration studies I know how difficult it can be and I am impressed with the 

level of detail supplied. 

However, it is my understanding that an attempt will be made to use these data to simulate 

exposure patterns from water containing volatile organic compounds (VOC) as the system existed 

in 1968–1985. I didn’t find any references to that effort or any suggestions as to how that will be 

done in my material. My questions, therefore, are as follows:

 1. Is there enough information on potentially exposed population distributions as they 

existed in the target time period to make an exposure assessment?

 2. Does the Marine Corps have as-built drawings and operational information for the 

target time period comparable to the data contained in the report entitled “Analysis of 

Groundwater ....?”

 3. For the target period, can you show changes in network and system operation that can be 

matched against exposed populations during that time period?

 4. If not, then what kind of assumptions will be required to develop that kind of 

information?

 5. What kind of errors might be inherent in those assumptions?

 6. As we know from waterborne disease investigations, for an infection to occur, water must 

be consumed by the target population at the same time the contaminate is present?

 7. Do you have sufficient information on water consumption, and water-use patterns and 

target population behavior patterns to make an estimate as who was exposed and when? 

For example, if members of the target population could be assumed to take showers in the 

morning were VOCs present in the water at a point where contaminated water could have 

been drawn into the household plumbing system during the showering period?

 8. Water use as shown by Steve Buchberger at the University of Cincinnati seems to follow 

the Poisson Rectangular Pulse pattern. Has any attempt been made to characterize the 

water use of the target population as a stochastic variable and assess what effect such a 

characterization would have on the exposure patterns of the affected population?

 D1
David E. Dougherty, PhD

Comments

The following comments are preliminary and have not been sorted into any particular structure. 

They also reflect limitation in the amount of available time to review and prepare comments.

Some abbreviations used below:

ABC—ABC One-Hour Cleaners

PHA—PHA for Marine Camp Lejeune

PHA/ABC—PHA for ABC One-Hour Cleaners

Panel Brief—draft report prepared for this Expert Peer Review Panel 

PPT—powerpoint presentation

PCE—tetrachloroethylene

TT—Tarawa Terrace

HP—Hadnot Point

HB—Holcomb Boulevard

T&E—testing and evaluation

This section is organized by transport-and-fate chain of events

Sources of Waste

1. How are the sources going to be represented in the simulation models for water movement 

and distribution? Have they been characterized with equivalent adequacy for all three 

areas?

2. The Panel Brief does not adequately discuss the signatures of sources (i.e., source 

concentration locations and histories) that will used for the TT, HP, and HB areas. 

a. TT: The ABC location is described, but there is no indication of how specifically this 

 will specified for simulation purposes or for any uncertainty analyses that may be 

 performed. 

b. TT: The PHA/ABC provides some additional information relating to TT. Moreover, 

 the Panel Brief (Groundwater Modeling section, page 20, last paragraph) suggests that 

 PCE concentrations found in 1993 as much as 1,200 ft west of ABC may be suggestive 

 of one or more sources of PCE west of ABC. Additional discussion and data are 

 needed.

c. HP: Other than general discussion of underground tanks, etc., source characterization 

 and modeling information is not provided.

d. HB: Similar to HP.

Groundwater Flow, Transport, and Fate

 1. What type of simulation modeling will be performed in addition to saturated 

groundwater-flow simulation with MODFLOW 2000? Will there be a transport model? 

Will a MODPATH (or similar) model be used only? Is there any sorption? Other 

processes in addition to advection? (Panel Brief, Background section, page 1. Also, 

page 13 of the October 8, 2003, PPT says groundwater-modeling requirements include 

“calibrated HYDRAULIC model” and the next page says “fate/transport parameter 

layers” are needed.)

D2  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
 2. One major question the panel is supposed to address is the adequacy of the 50 ft grid. 

Additional information is needed. Some is related to downstream analyses for doseduration curves. (For example, what duration of exposure will be examined. The 

March 18, 2005, supplemental information suggests that a 1-week exposure may be 

significant. 

 Some others are appropriate here:

 a. Are there distance-drawdown data that have been plotted that show the region of 

influence of the TT wells in the subunits (as used in this study) of the Castle Hayne 

aquifer and in the overlying surficial materials?

 b. See the next, broader, point.

 3. Additional information on aquifer heterogeneity (e.g., spatially variable hydraulic 

conductivity) is crucial.

 a. Drilling logs are needed. Both driller and geologist logs will be useful. The resistivity 

logs provided in the March 18, 2005, supplemental is inadequate. 

 b. Cross sections would be very useful. To help focus a response, a “pathline cross 

section” that passes through source area and is aligned with paths that idealized 

“particles” would take through the aquifer. 

 c. Cross sections that show the MODFLOW simulation model grid juxtaposed with the 

textural information would be quite helpful.

 d. The supplemental information provided March 18, 2005, indicates that the 

preliminary epidemiologic study makes use of PCE contamination at TT. Is there any 

reason to believe that any in situ processes that caused partial dechlorination (e.g., 

PCE=>TCE) should be considered or should be ignored?

 e. No information on HP and HB groundwater-modeling plans or activities was 

provided. 

 4. The northern boundary of the TT groundwater model (Figure 8 of the Groundwater 

Modeling section of the Panel Brief) appears not to extend sufficiently far north and to be 

too close to the contaminant source area. Further discussion and justification is requested. 

Wells

 1. TT: A cross sectional style drawing with the as-built information for each water-supply 

well that was pumped during the study period would be helpful. Screen and gravel pack 

location, seal location, grout/backfill location. This should also indicate the model layer 

boundaries for the stack of cells in which each well is located.

 2. TT: A single table/chart is needed that indicates, for every produced well, when installed, 

when operated, when permanently removed from service, and as much pumping rate 

versus time information as may be available. Dates of well rehabilitation and measures of 

well efficiency are also needed.

 3. HP and HB: No information was provided, but similar information as above is indicated.

Water-Distribution System

 1. Census information would be useful (i.e., number of housing units, number of residents, 

and number of study residents versus time) for the three water supplies. 

 2. What is the status of historical water-distribution network definition? Status of historical 

water-distribution network simulation work?

 3. Have field studies to date led to any assessments of uncertainty and variability of key 

hydraulic properties (e.g., roughness, mixing at junctions)?

 4. What kinds of operational record for the groundwater wells exist? 

Panel Members’ Premeeting Comments D3
Individuals

 1. Is prior housing (during pregnancy) being considered?

 2. Did water-use patterns change significantly from 1968 to 1985? Are they significantly 

different from today’s usage (e.g., cooling and other appliances, conservation measures)?

Exposure

How much uncertainty can be tolerated at this end of the chain of analyses? 

Schedule

 1. Can you provide additional information on time allotted and time used by each of the 

scheduled activities? Can you provide percent-complete approximations for each activity?

 2. What do you currently extrapolate would be the schedule to perform the groundwaterrelated activities for HP and HB? To perform the historical network construction, T&E, 

and simulations?

 3. Do you have a PERT network and critical path analysis? 

 4. Have time estimates for activities proven to be sufficiently accurate? If not, which 

activities have “exploded” the schedule? 

 5. Looking forward, where are the greatest potential scheduling pitfalls?

 6. Comparing the 3-year proposed schedule and the revised schedule (both appearing in the 

July 28, 2004, PPT) there appears to have been a revision of 10 months for background 

information, 6 months for current distribution network, 9 months for historical 

distribution network, 3 months for methods, and 14 months for reporting. (These overlap 

and are not cumulative.) Anything new to report?

Questions, Requests, and Comments on Materials Provided (no particular order)

October 8, 2003, PPT

Page 32 refers to “Simulation using BRAGS model data.” Is this significant to our work?

March 18, 2005, Supplemental

Feedback on item #2. Thanks for the electric logs. However, see previous comment about 

logs and cross sections.

Panel Brief

 1. Geohydrologic Framework chapter, page 11. The Geologic Framework section describes 

the top of the marl (the Local Confining Unit) as the top of the Castle Hayne. However, 

other information includes the overlying River Bend unit.

 2. Geohydrologic Framework chapter, Figure 2: Need to map the hydrogeologic units here 

to the names used on Figure 6. 

 3. Geohydrologic Framework chapter, Figure 29: Why closed contours (i.e., circular knoll 

feature) for high K (horizontal hydraulic conductivity)? Why not more of a linear (ridge) 

configuration, such as would be indicative of a channel? Same question for Figure 28. 

 4. Groundwater Contamination chapter, page 8: Although PCE was only purportedly used at 

ABC, is there evidence of dechlorination that would be significant to this study?

D4  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
 5. Groundwater Contamination chapter, Figure 2: Is it possible to provide water-supply well 

information for the TT-series of wells? (Posted with well identifier.) Range of dates of 

service, pumping rate capacity (with date), for example? 

 6. Groundwater Contamination chapter, Figure 11ff: How were these samples collected and 

handled before laboratory analysis? 

 Are all of the protocols consistent? Are there additional observations for dates after 

July 1, 1991? Since there are no data before early 1980s and study goes back to 1968, we 

need information from the recent past. For example, TT-26 Figures (#12 for PCE, #14 

for TCE, and #15 for DCE) are suggesting dechlorination. Additional data might be used 

to do breakthrough/travel time estimates using the arrival of clean water (assuming the 

source has been interrupted).

 7. Groundwater Modeling chapter, page 16, top 2 lines: The sentence reads “[c]alibration 

was achieved rapidly with little or no adjustment of hydraulic characteristic arrays or 

recharge rates” (emphasis added). What was adjusted to accomplish the calibration?

 8. Groundwater Modeling chapter, page 16: The static calibration curve (Figure 11) seems 

pretty good. However the text says “static water levels...were obtained using air line 

measurements...accurate within an estimated range of ±12 ft.” Is this error independent of 

water level (i.e., homoscedastic)?

 9. Groundwater Modeling chapter, page 16, last paragraph: Text says TT-25 was represented 

in model layer 7 (MCH), but Table 1 of this chapter indicates TT-25 is representing UCH 

and MCH. The same paragraph describes TT-23 as in layer 5 representing the UCH, 

though Table 1 describes it as in UCH and MCH. As indicated in remarks above, under 

bullet #1 of the WELLS heading, a cross sectional style figure with all the wells, the 

textural log information, and the local model layer boundaries would be useful.

10. Groundwater Modeling chapter, page 18: lines 3–5: Are there any records indicating 

that water-supply well maintenance (in particular, redevelopment, acidization, etc.) was 

performed?

11. Groundwater Modeling chapter, page 18–19: The text discusses the assignment of 

porosities to various HSUs and/or model layer numbers. Please provide a side-by-side 

correspondence tableau of HSU names, geologic framework names, and model layer 

numbers, and give appropriate parameter values for each (e.g., porosity, horizontal 

hydraulic conductivity, hydraulic conductivity anisotropy ratio). 

12. Groundwater Modeling chapter, page 18, last paragraph, continuing on page 19: In 

discussing the seeding of particles, please indicate the layer in which the particles were 

placed. Sentence 3 talks about “the immediate vicinity of ABC”, sentence 4 talks about 

particles “placed in model layer 3,” sentence 5 talks about “particles were then placed 

at ...” without a layer, and so on. 

13. Groundwater Modeling chapter, page 19, first paragraph, last sentence: Since the average 

pore velocity is inversely proportional to porosity, can you explain why cutting porosity 

in third did not change materially the breakthrough times? Is the majority of the particle 

travel time in other layers, in which porosity is not changed, so the overall impact of layer 

5 porosity is diminished? 

14. Groundwater Modeling chapter, page 20, paragraph 2: For particle pushing using the 

MODFLOW simulation result (“advective transport simulation”), was any sorption 

incorporated to determine travel times? Linear or other isotherm? For typical values, the 

introduction of PCE source more than 10 years before the start of the study period and the 

continuation of the PCE source throughout the study period, and depending on the source 

release model (undefined, as noted earlier), sorption may be inconsequential for this 

study.

Panel Members’ Premeeting Comments D5
15. Groundwater Modeling chapter, page 20, paragraph 3: The reported inconsistency of 

results at TT-23 cannot obviously be concluded to be the result of a source of PCE 

located much closer to the well, although it could be. Wouldn’t an inverted statement—

such as, “the inconsistency leads to the obvious conclusion that the advective transport 

simulations are incorrect, assuming that the source characterization study previously 

undertaken for ABC is essentially correct”—have a stronger case in fact? Following this 

line of thought, in the 15 years since the PHA/ABC, has solid or circumstantial evidence 

of additional potential sources come to light? In midparagraph is the statement that “PCE 

concentrations were also noted in samples collected in 1993 at several monitoring wells...

located north and west of ABC...The westernmost well location was about 1,200 ft from 

ABC.” Please give more information (locations, dates, values) relating to these samples.

 There may be other alternatives, too. Since the pumping rates assigned to each well 

are only estimates for the period 1978–1994, according to page 16, and since the 

contamination was in the groundwater for almost 15 years before the beginning of the 

study period, isn’t it possible that if a greater proportion of the pre–1978 pumping came 

from the more southern supply wells then this would cause the plume to have an initial 

condition that differed substantially from simply the source condition, and this “premigrated PCE plume” is the plume that was actually detected? 

 As previously noted, it seems plausible that the no-flow northern boundary of the 

groundwater model is located too close to ABC and the TT wells. This could influence 

the pathlines of particles and their travel times. 

 In summary, the current form of this discussion leaves too many loose threads.

16. Groundwater Modeling chapter, page 20, paragraph 3, last sentence: The suggestion 

at the end of the paragraph that “dispersivity is possibly responsible for a substantial 

transfer of PCE mass from one [well’s capture zone] to [the TT-23 capture zone]” seems 

implausible. (Note that the process is dispersion, and that dispersivity is a material 

property.)

17. Groundwater Modeling chapter, Figure 2: Are there any additional pumping wells offsite 

to the north of TT?

18. Groundwater Modeling chapter, Figure 11: Have the data on Figure 11 been regressed? 

The plotted data appear to have a slope of about 0.5, rather than the ideal 1.0. 

19. Groundwater Modeling chapter, Figure 13: The text relating to this figure says most data 

plotted here are air line data. Could you indicate which are not?

D6  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
Benjamin L. Harding, PE

Initial Response to Charge

This is in response to the request by ATSDR that Camp Lejeune Expert Peer Review Panel 

participants write down their initial response to the charge and questions provided to the panel. 

The following comments reflect my best understanding at this time. Because I recognize that my 

understanding is probably incorrect and incomplete, these are provided for discussion purposes 

only and should not be distributed outside the Panel, ATSDR staff, and consultants.

Situation

 1. Residential and working areas at Camp Lejeune, North Carolina, were supplied by three 

water-distribution systems, designated Holcomb Blvd., Tarawa Terrace, and Hadnot 

Point. The history of development of the three systems has not been described other than 

that the Hadnot Point WTP reportedly once served all three systems and that the systems 

are now separated.

 2. The study period for this investigation is from 1968–1985.

 3. The groundwater supplies to the Tarawa Terrace and Hadnot Point WTPs were apparently 

contaminated before 1982. Some contaminated water from the Hadnot Point system was 

known to have been introduced into the Holcomb Blvd. system for a period of about 2 

weeks. It is possible that the Holcomb Blvd. system was interconnected with the Hadnot 

Point system at other times. It is also possible that the Holcomb Blvd. system was 

interconnected with the Tarawa Terrace system.

 4. The Tarawa Terrace and Hadnot Point WTPs were supplied by well fields. Not all wells in 

either well field were contaminated to the same levels.

 5. Only spotty records of production from the WTPs have been made available to the Panel 

to date. I do not know the extent of historical production data.

 6. No production data for individual wells have been made available to the Panel to date. 

I do not know the extent of historical production data.

 7. Only very limited metering was done on these systems and none was done on residential 

units.

 8. Based on information to date, it appears that these systems operated most of the time as 

separate systems each, with a single point of supply.

 9. The contaminants are VOCs.

10. Some measurements of the contaminants are available, both from the groundwater system 

and from the water-distribution system.

11. The types of contaminants and level of contamination are such that any disease would 

arise from chronic rather than acute exposure.

12. ATSDR is undertaking an epidemiologic study of residents and workers on the base.

Outstanding Questions

 1. What is known of the history of development of the systems, particularly their 

interconnection and their sources of supply?

 2. Are historical aerial photographs of the base available over the study period?

 3. What production data (for individual wells and/or for the WTPs) are available?

Panel Members’ Premeeting Comments D7
 4. What were the policies for dispatch of individual wells?

 5. What were the seasonal, weekly, and diurnal patterns of water use?

 6. What are the precision requirements for the epidemiologic study, in terms of the arrival 

time of contaminants and the accumulated human intakes of contaminants?

Responses to Issues and Questions

These responses are based on the information I have at this time and are subject to change:

Groundwater

 1. No groundwater model is necessary for the Holcomb Blvd. system, since there is no 

indication that the wells in this system were contaminated. A groundwater model is 

necessary for the Hadnot Point system, as wells that served that WTP were contaminated.

 2. I can’t comment on the advisability of developing single model covering the entire base 

area.

 3. ATSDR should quantify the effect of variability and uncertainty on contaminant 

concentrations at public water-supply wells.

 4. ATSDR should address the issue of lack of observed water-level data before 1974. If 

nothing else, this will increase the uncertainty of results before this time.

 5. ATSDR should attempt to reconstruct monthly groundwater-production data. The 

uncertainty of these reconstructions should be quantified.

Water-Distribution Systems

 1. I think at this time that the ATSDR has collected more than enough information on the 

current system. Emphasis should be placed on reconstructing historical systems. The 

most important piece of information to know is the extent to which the systems were 

interconnected. During periods when the systems were not interconnected and were 

operated as single-source systems, the modeling can be greatly simplified, e.g., hydraulic 

modeling may not be necessary.

 2. The information to date should provide for adequate calibration of the current system 

model, with the understanding that the historical systems will be far more poorly 

understood.

 3. ATSDR should consider separating water uses into classes (e.g., indoor residential, 

outdoor residential, indoor commercial, etc.) and estimating these components separately 

based on appropriate variables (population, floor area, irrigated area, etc.) and methods. 

Because these systems are likely single-source systems the distribution of water use will 

have very little impact on the long-term levels of exposure.

 4. For periods when the systems operated separately, and assuming they are indeed singlesource systems, no sophisticated models are required. Whether or not models are required 

for periods of interconnection depends on the extent of interconnection. It may be that no 

hydraulic model is required at all.

 5. If the interconnections to the Holcomb Blvd. system were made only on an emergency 

basis, and based on my understanding of the role of the suspected contaminants in the 

causation of disease, I think it is appropriate to treat the Hadnot Point and Holcomb Blvd. 

systems separately. 

D8  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
 6. ATSDR should use probabilistic approaches to quantify estimates of the uncertainty and 

variability of estimates of exposures, intakes and risks resulting from the modeling. The 

question of which variables have the greatest influence on the model results depends on 

the answers to questions about the configuration of the water-distribution systems, and 

can be informed by sensitivity analyses.

 7. The fire flow testing seems sound.

 8. Whether or not the use of monthly vignettes for simulation is sufficient depends on the 

dynamics of the systems.

 9. It is feasible for ATSDR to use a continuous analysis, but it is probably not necessary 

given my feeling that the systems are not very dynamic (except, perhaps, if there were 

substantial periods of interconnection.)

10. Sophisticated techniques to integrate the groundwater and water-distribution models 

are not necessary. It is necessary to have one set of well production data that is used 

by both models. ATSDR should consider using the concept of superposition in the 

water-distribution system to calculate exposure concentrations based on well-head 

concentrations developed by the groundwater models.

Responses to Charge

These are my initial impressions and are subject to change:

 1. No comment on groundwater modeling. “All pipes” networks should be used if 

sophisticated hydraulic modeling is required.

 2. If the data show the system operation is dynamic, and for periods when there is more than 

one source, continuous simulation should be considered. It does not appear at this time 

that this will be necessary.

 3. (A) No comment on groundwater. (B) Given the dearth of information about the historical 

systems, the present-day reconstruction probably does not need additional refinement.

 4. I can’t comment on this because I don’t know the complexities of the groundwater 

modeling. But, it should easily be possible to complete a reconstruction of the waterdistribution systems within 3 years unless the process is substantially constrained by the 

public documentation process.

Panel Members’ Premeeting Comments D9
Leonard F. Konikow, PhD, PG

Comments

These preliminary comments focus on the first five chapters of the draft report for the review panel:

Introduction

 Page 1: It says the 1997 PHA determined the drinking-water exposures. So why exactly is 

this study needed? Was the earlier work flawed or incomplete? 

Background

 1. Page 1: Five questions are listed as being addressed. None clearly indicate a desire 

or need to estimate the level of contamination, as opposed to the timing of the 

contamination. Isn’t there a relation between dose and health effects? This issue relates 

to the need for a solute-transport model that computes concentrations of contaminants in 

the supply wells and water-distribution system versus an advection model that estimates 

travel times.

 2. Page 1: Goal 3 is development of fate and transport models. However, an advective 

transport model is not normally considered to be a “fate and transport” model because it 

does not consider concentration gradients, dispersion, or reactions.

Geohydrologic Framework

 1. Page 9: It says recharge to the water table was simulated at a rate of 11 in/yr. However, 

the subsequent model description indicates the rate used was about 10% higher than 

stated here. Does the estimate of recharge include an accounting of leaks, lawn watering, 

and septic tank discharge that occurs in urban areas and yields effective recharge greater 

than would occur under natural conditions?

 2. Figures: Many of the figures in this and other chapters include contours that don’t look 

particularly realistic. Also, many of these maps don’t show control points, include a 

description of how they were derived, or indicate contour intervals. 

 3. Figure 11: This shows several large areas where the indicated top of the Tarawa Terrace 

aquifer lies above the elevation of the land surface or above the water surface. This is 

obviously impossible. If this contour map was used as a basis for computing the thickness 

of the TT aquifer, then that map also includes serious errors. Have such errors propagated 

down to other layers? Were these erroneous thickness and elevation maps actually used in 

the simulation model? 

 4. This section does not include any cross sections. Such illustrations would help the reader 

to better understand the geohydrologic framework. This is especially true for assessing 

hydrologic boundary conditions in the aquifer and flow directions in three dimensions. 

The same goes for presentation of model results in later chapters. 

 5. Page 15, Why is a 1-ft-thick clay layer “considered not to be of geohydrologic 

significance for this study?” If such a layer is present in the area of contamination, it 

could certainly have a major impact on contaminant transport. 

 6. If kriging was used to interpolate and contour values, it should also have been capable 

of estimating confidence intervals. These would certainly be of value and should be 

presented.

D10 Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
 7. Page 20: Why wasn’t a parameter estimation model used to estimate the hydraulic 

conductivity (K) distribution? What about vertical hydraulic conductivity?

 8. Page 20: Clarify why a predevelopment head surface is needed and what will be done 

with it. It is based on data collected over a broad time span, including some data from the 

1960s, 1970s, 1980s, 1990s, and 2000s. How can these observations all be considered to 

represent predevelopment conditions? Where are the potentiometric surfaces for the time 

during which development (and contamination) occurred? That seems to be the critical 

time for contaminant transport. Why isn’t a water-table map shown? Why are heads (in 

Figure 30) where the aquifer underlies the New River significantly above the water level 

in the New River? 

 9. Figures: Why is the northern extent of the contouring where it is—the boundary here 

seems to lie too close to the area of the contamination source.

Groundwater Contamination

 1. Page 7: At what depths were the contaminated supply wells screened? Were they 

constructed with a gravel pack that extended vertically above or below the screen 

interval? 

 2. Page 13: If the center of mass actually migrated at 0.3 ft/d, then we can solve Darcy’s 

Law for porosity (ε) using the approximate values from the maps for K and hydraulic 

gradient in this area (about 1 ft per 180 ft, or about 0.0056). This approach results in an 

estimate of ε = 0.28 (assuming that the retardation factor, Rf, =1.0). This estimate should 

be compared with the values of 0.15 or 0.20 used in the model, and the inconsistency 

explained. Were there any tracer tests conducted in the area that can be used to cross 

check estimates of effective porosity and perhaps dispersivity coefficients? (A recent U.S. 

Nuclear Regulation Commission report indicates that tracer tests were conducted at Camp 

Lejeune, although the report does not indicate the complete nature or location of these 

tracer tests; it would be worthwhile to get more information on these prior tests.)

 3. Page 14: Why is = 0.15 used as basis to compute the mass of contaminant in the aquifer? 

Why is “effective porosity” used here instead of total porosity? It doesn’t seem likely that 

this aquifer material would include disconnected porosity that is not contaminated. In 

the model a specific yield for the upper layer of 0.20 is used. It seems likely that the total 

porosity would be equal to or (more likely) greater than the specific yield. Thus, there 

may be a large error in this estimate of contaminant mass.

 4. Figure 5: There are a few mislabeled contours in this figure.

Groundwater-Flow Model

 1. Page 9: It is not clear why K was selectively assigned values of 0.00073 or 5.0 ft/d. Where 

did these particular values come from and what triggered the selective assignment?

 2. Page 14 and Figure 8: The boundary conditions & domain boundary seem inadequate. 

Setting the southern flow boundary on Northeast Creek might be appropriate for the 

shallow layers, but seems dubious for the deeper layers. The maximum depth of the 

channel is about 10 ft in this area. Why would deep groundwater discharge vertically 

upward here than continue to flow laterally towards the nearby coast. I think this 

condition needs to be justified. Also, the northern extent of the domain seems too close 

to the contamination source. The indicated boundary condition will force vertically 

downward flow at and near the northern boundary, and it doesn’t look like this location 

represents a divide for the shallow flow, let alone the deeper flow.

Panel Members’ Premeeting Comments D11
 3. Figure 11 and predevelopment calibration results: There seems to be a bias in these 

results. That is, areas where heads are relatively high tend to be underestimated, and 

in areas with lower heads (discharge areas) the calculated heads consistently are too 

high. This bias may be related to errors in the imposed boundary conditions that are too 

constraining. This bias should be corrected if possible. 

 4. Page 16: Not clear what the initial conditions were for the transient model. If the 

predevelopment potentiometric surface, did those predevelopment conditions really apply 

or exist in 1978? Monthly stress periods were used, but what time steps were used for 

each stress period? 

 5. Figures 13–18: There seem to be a fair number of errors greater than 10 ft. At or about 

t = 2,000 days, the calculated head is too high by about 20 ft in TT26, and 20 ft too low in 

TT31. That’s a 40-ft error in the gradient, which drives flow. 

 6. Page 17 and calibration process: Why was recharge adjusted to 16 in/yr in places, and 

where and why was this done? How was the calibration process implemented? Were 

recharge and pumpage rates the only parameters that were adjusted? Why not use an 

automated parameter estimation model?

 7. Page 18–19, Advective Transport Model: Actually, MODFLOW computes fluxes (or 

specific discharge) between cells, not velocities. You set porosity = 0.15 in all layers 

except layer 1. Wouldn’t we expect the porosity in the clayey confining layers to be 

substantially greater than in the sandy aquifer layers? In MODPATH, why not place 

initial particle locations at top of layer 1, since that is exactly where the contaminants 

reach the water table and enter the saturated zone? It’s not clear why particles were also 

placed 600 ft away from the ABC Cleaners site. Are there vertical components to the 

calculated particle pathlines that are not being illustrated but might be important?

 8. Figure 19: Is there an observed potentiometric surface for mid-1980s to compare to the 

calculated one? 

 9. Why was the porosity adjusted to 0.05 in layer 5? How could that not affect the velocity 

in layer 5?

10. Page 19, Summary and Discussion: It says that “simulated potentiometric levels and 

flow directions were highly similar in all model layers.” This is certainly not surprising 

because identical boundary conditions were imposed in all layers. What are budget 

numbers under transient conditions? 

11. Page 20: It states that “the conclusion is obvious that ...” But, it is not “obvious” to me 

that the source of PCE in TT-23 was not ABC Cleaners. What reasons support this 

important conclusion?

12. Advection model: It seems inadvisable to rely on a single realization of particle tracking 

and related travel times. The system includes heterogeneities (and uncertainties) at 

several scales, as well as some transient conditions, that are not represented in the model, 

and these will yield a variance in arrival times and source area definitions. This should be 

evaluated—perhaps using a coupled geostatistical and Monte Carlo approach. 

D12  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
Eric M. LaBolle, PhD

Response to Primary Charge Questions

 1. The choice of groundwater-model cell size depends in part upon (a) the subsurface 

heterogeneity, specifically the scale of significant hydrofacies or upscaled heterogeneity 

to be modeled, and (b) the discretization necessary to obtain an accurate numerical 

solution to the problem posed. Discretization may also be constrained by the available 

computing power. The documentation lacks information on the hydrofacies scale 

variability necessary to assess an appropriate horizontal cell size. However, I assume 

that hydrogeologists building the model have chosen 50 ft based on constraints imposed 

by this variability. If this is indeed the case, then one would successively refine (instead 

of coarsen as implied by the question) the grid (while maintaining the heterogeneity 

associated with the 50-ft grid) in numerical experiments to determine if 50 ft is sufficient 

to obtain an accurate numerical solution to the problem posed.

 2. One should not overlook the importance of the vertical resolution. Points (a) and 

(b) above also apply here. The length scales of hydrofacies in the vertical appear to be on 

the order of feet (or less). The modelers have upscaled these features. Therefore, the level 

of detail in the vertical needed to accurately model the character of fate and transport in 

this system potentially warrants further consideration. Additionally, if the upscaled model 

is to be used in its current state, the coarse vertical grid may result in unphysical, rapid 

vertical transport due to numerical errors and ensuing exposure misclassifications. For 

example, with some numerical methods used to solve the transport equations, a source to 

a layer will instantly mix over the entire vertical dimension within the layer, regardless of 

its dimensions, whereas the numerically accurate solution may predict vertical transport 

over days, decades, or centuries. Furthermore, coarse vertical discretization can result 

in an inaccurate representation of screened intervals. Numerical experiments should be 

performed in which one maintains the upscaled heterogeneity while refining the vertical 

discretization to assess the vertical resolution needed to obtain an accurate numerical 

solution to the problem. 

 3. If the water-distribution system model is necessary (see below), numerical accuracy this 

model is also a potential concern. Numerical experiments, similar to those suggested 

above, could be performed to assess the discretization in space and time necessary to 

obtain an accurate solution to the problem posed. 

 4. With regards to the temporal resolution of the water-distribution system model, I believe 

that ATSDR should first seek to determine if, and at what time(s), there was more than 

one source of water to the water-distribution system. A water-distribution system model 

is unnecessary to compute exposure during the time intervals when there was a single 

source of water to the system (only source concentrations are needed in this case). 

Limiting the analysis to these times can eliminate the added expense and time associated 

with further development of the distribution model. If a water-distribution system 

model is needed (for those times when there was more than one source of water to the 

system), then one should weigh the benefits of resolving the temporal resolution of the 

water-distribution system model given the inherent uncertainty in exposure estimates 

due to the unknown heterogeneity of the subsurface and unknown contaminant source 

characteristics. 

 5. For times when there were multiple sources to the system, then given the temporal 

resolution of the available data, a representative 24-hour period within a month appears 

appropriate for the water-distribution system model provided that typical cycling of the 

Panel Members’ Premeeting Comments D13
sources of water can be represented by a single day. Otherwise, a longer period may 

be needed. In either case, my experience has been that no day within the month will 

necessarily represent an average because there is memory in the system, particularly with 

regards to transport, that can (a) carry mass from the previous month into the current 

month (in the actual system and in the model if it is run continuously), and (b) generate 

patterns that do not follow a 24-hour cycle. Computing a representative day may require a 

continuous model with exposure averaged over several days.

 6. My primary concern with the schedule is consideration for the time and methodology 

to compute alternative exposure scenarios, if required. Exposure misclassifications can 

lead to a false null result depending upon the degree of misclassification and the dose 

response relationship (uncertainty in the model and variability in individual response). 

Conversely, exposure misclassifications are not expected to yield a false correlation/dose 

response (because apparent responses are expected to be distributed randomly in space 

and time). If the dose response is weakly correlated, even a small degree of exposure 

misclassification can mask detection. Thus a model approach that offers the flexibility 

to compute numerous alternative exposure scenarios is most likely to be successful in 

detecting a response, if one exists (particularly if the dose response is weakly correlated). 

A null result, therefore, should not lead one to conclude lack of a dose response 

relationship and/or effects within the population due to exposure. What does ATSDR 

intend to do should the study initially yield a null result? How does ATSDR intend to 

conclude the work should the end date be reached with a null result? 

 7. My concern in this regard is the lack of an approach to address the hydrogeologic 

uncertainty and variability in the groundwater-flow and transport models. The subsurface 

heterogeneity, highly variable and uncertain, is likely the greatest source of uncertainty in 

exposure. An approach that restricts one to a single characterization of the heterogeneity 

limits flexibility in computing alternative exposure scenarios, and will therefore 

unnecessarily constrain model outcomes to a particular range of exposure estimates 

(based on tuning model parameters with constraints imposed by the characterization). 

The model response, constrained by a single characterization of the heterogeneity, may be 

associated with a null result due to inherent exposure misclassifications. 

Response to Charge

Additional Comments

1. Hydraulic conductivity estimates appear to assume that the entire screened interval 

contributes significantly to the transmissivity, whereas typical high-K volume fractions 

can range from 20–80%. Has ATSDR accounted for high-K volume fractions (estimated 

from detailed logs) within the screened intervals in estimating initial K values? Is this 

accounted for by scaling the effective porosity?

2. The relatively small vertical gradients between aquifers suggest the possibility of 

significant vertical connectivity. Do the well tests include monitoring within the different 

aquifers to assess connectivity and degree of confinement?

3. How does ATSDR intend to deal with the acknowledged biodegradation of PCE and its 

byproducts in the fate and transport model, its calibration to observations, and exposure 

estimates?

4. Has the model been simultaneously calibrated to all available hydraulic and contaminant 

data (past to the present), including for example, the well test data?

5. ATSDR has noted that overcapacity in the distribution system resulted in substantial 

cycling, and therefore significant down time, of wells during the study period. Capture 

zones are a direct result of the duration and magnitude of pumping. Has ATSDR 

D14  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
investigated the effect of using monthly averaged, versus temporally varying nominal, 

pumping rates on the predicted capture of contaminants? Is the use of a monthly 

hydraulic model appropriate to predict contaminant capture when there is significant 

cycling and down time of the wells (even if one does not know the actual pumpage due to 

data limitations)?

6. I have prepared the following table regarding exposure misclassifications and their 

potential effects on the result; this could be relevant given a weak dose response 

relationship and pertains to my response to question 3 in the primary “Charge to the 

Panel” questions. 

Effect of Misclassification of Exposure on Ability to Detect an Association between Exposure and Health Effects

No True Correlation True Correlation

Misclassification 

of exposure with 

respect to health 

effects

Potential effect 

on result Occurrence

Potential effect 

on result Occurrence

Correlated False Correlation

Unlikely because health effects 

are random within the population and the sample size is 

sufficient.

False increase 

or decrease in 

correlation

Possible if exposure levels are 

correlated with locations and 

times of at least some misclassified exposures.

Uncorrelated None

Likely because health effects 

are random within the 

population.

False decrease 

in correlation

Likely because of inherent 

randomness in the direction and 

degree of misclassifications

Panel Members’ Premeeting Comments D15
Peter Pommerenk, PhD, PE

Fate and Transport Modeling

Occurrence of Contaminants

 1. Page 7: Well TT30 is mentioned in text and shown in Figure 2. Why was no further 

information provided, particularly with respect to the fact that no contaminants were 

found in this well despite its close vicinity to TT26? 

 2. Why were not more water-level data from locations south and west of ABC cleaners 

incorporated to obtain a more complete depiction of gradients in the TT and Upper Castle 

Hayne (UCH) aquifers?

 3. On page 12 (first full paragraph) it is stated that “Well TT-23 is not located on an 

advective pathway from ABC One-Hour Cleaners...” referring to Figures 4 and 5 that 

show the 1992 potentiometric surfaces (5 years after the wells were shut down). Could 

it be that during the 40 years of ABC Cleaners’ operation highly variable, multiple 

advective pathways were present that are not reflected by Figures 4 and 5? 

 4. Figure 30 in the Geologic Framework section suggests a strong gradient to the south for 

the TT area under predevelopment conditions. Could it be expected that these conditions 

were reestablished by 1992, 5 years after the TT wells were shut down? If so, do Figures 

4 and 5 represent a complete picture of the gradients in the TT area?

 5. Based on the observation that “the lobes of PCE mass extending northwest and southwest 

of ABC One-Hour Cleaners are either directly opposite or somewhat orthogonal to 

the hydraulic gradient within the TT aquifer” (Page 13) it was suggested that pumping 

by other (unknown) wells caused PCE migration. Therefore, can Figures 4 and 5 be 

considered an adequate temporal and spatial representation of over 30 years of advective 

contaminant transport in the TT area?

Simulation of Ground Water Flow

 1. Is it possible to elucidate how pumping rates were established to simulate withdrawals? 

On page 17 it is implied that pumping rates were simulated by balancing the annual 

withdrawals. Can this approach account for the well operation practice that has been 

established at the existing Camp Lejeune water systems? Because the existing wells are 

operated for only 6–12 hours daily and rotated every 2 to 4 weeks, is it likely that the TT 

wells were operated in a similar manner?

 2. Camp Lejeune personnel logs both static (non-pumping) and operating (pumping) water 

levels for all operable wells. The “observed” hydraulic heads in Figures 14 through 18 

suggest that measurements during static conditions were included for calibration. Is it 

appropriate to compare simulated water levels with these measurements? 

 3. Daily fluctuations due to nightly well shutdown do not appear to be simulated in the 

model. Were the pump capacities in Table 4 adjusted to account for less than 24/7 

operation? How does the monthly averaging of pump rates affect the hydraulic gradients? 

 4. Given the relatively large discrepancy (10 ft for 2 to 3 years, or 24 stress periods) between 

simulated water level and observed water level in Wells TT31, TT25, and TT52 and the 

importance of both relative and absolute water levels to advective transport, is additional 

calibration warranted?

 5. What is the rationale for selecting 1978 as the beginning of the model simulation?

D16  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
Water-Distribution System Modeling

 1. Is it possible to include a discussion of how present-day water-distribution system 

modeling will aid in reconstructing a past water-distribution system? For example, will 

C-factor testing of existing pipes allow estimates of pipe roughness 30 years ago? Are 

current node demands representative of past consumption considering, for example, 

changes in fixtures (e.g., low-flow toilets) and effects of landscaping on irrigation water 

demands, etc.?

 2. Can a discussion be included on how the output from the groundwater model will be used 

as input to the water-distribution system model and what time steps will be used?

Water-Distribution System Modeling of Present Day Conditions

 1. Page 4: It was assumed that domestic irrigation is more intensive from May through 

September. It is not clear what this means. It this a reasonable assumption considering 

that June through September are the wettest months in this area?

 2. Pages 3–5: Is the assumption of seasonal variation in water demand (due to irrigation, 

heating plant and cooling system consumption) supported by historical water-production 

data?

 3. Pages 3–5: Were troops that are currently on deployment excluded from the population 

estimates?

 4. Page 8: What may have been the cause for the large discrepancy in accounted-for and 

measured water consumption for the Hadnot Point system?

 5. Table 15: Is it reasonable to assume the same C-factor for a wide range of sizes and ages 

of pipe of the same material?

 6. Figures 12–14: Are the lines showing “simulated” flow not merely input data to the 

model?

 7. Figures 49: Are the lines showing “simulated” chloride concentrations not merely input 

data to the model?

 8. Page 19: What are the criteria for a “calibrated” model? Figure 2 seems to indicate that 

daily demand patterns are highly variable; therefore, would a demand pattern modified to 

match hydraulic heads on a particular day be expected to be representative?

 9. Page 20: What is the basis of assuming that the storage tanks behave as continuous stirred 

tank reactors as opposed to some other configuration, e.g., last-in-first-out?

10. Figure 54: Is there an explanation for the significant lag between simulated and measured 

chloride peak?

Panel Members’ Premeeting Comments D17
Vijay P. Singh, PhD, DSc, PE

Questions and Comments

Groundwater Modeling

 1. How deep are wells?

 2. Point parameters have been used for a given aquifer. What is the basis for it? Is the 

aquifer homogeneous and isotropic? How were the parameters computed? 

 3. What are the hydraulic conductivity values in both directions?

 4. How was recharge estimated? What time interval was assumed? How was evaporation 

computed? How was infiltration computed? How was soil moisture balance maintained? 

How good are recharge estimates? Is there no contamination from the land surface to 

groundwater? How about contamination due to chemical fertilizers being applied to 

lawns, leaking of pipes, stormwater runoff; etc.? 

 5. Cell size: Why not use a variable cell size, finer near the source and coarser away from it?

 6. Figures 11–18 do not show a good agreement between observations and simulations? 

What is concluded from these figures? Do they form the basis for accepting the goodness 

of the model?

 7. In order to address a practical problem, a number of assumptions have been made in 

the modeling system, and justifiably so. The question arises: How good are the model 

results? What confidence can one put in the results? What is level of uncertainty 

associated with these results? What is main cause of uncertainty? What is the overall 

model reliability? 

 8. What is the most important parameter in the modeling system that is unknown and needs 

estimation?

 9. Is the modeling system being used adequate? Does it need further refinement or can it be 

further simplified?

10. How good are the data being used? Are the data subject to quality control?

Water-Distribution System

Is the C-factor going to remain constant? It seems it will not, because of aging of pipes, 

deposition of contaminants, roughness growth, and so on.

Epidemiologic Study

In establishing a relation between water pollution and birth defects, is the assumption 

that the defects will be solely due to water pollution? How about the effects of life style, 

smoking, living in a chemical environment at home, intake of chemicals though food, and 

so on? How were the effects of these factors eliminated or singled out in the study?

D18  Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
James G. Uber, PhD

Observations and Key Questions

Following are my observations and key questions. I’ve included my observations as they capture 

the essence of my current understanding, which may need clarification or correction.

 1. The simulation model studies are to quantify the exposure magnitudes and routes 

(including locations and times) of groundwater contamination via treated drinking water. 

In general, the significant source of uncertainty are associated with source characteristics, 

geohydrology, and transport through the water-distribution system. The study aims and 

goals are motivated by such sources of uncertainty and their presumed impact on the final 

epidemiologic analyses.

 2. It appears that there is significant evidence about the source locations and also about the 

time intervals over which they were acting. Geohydrologic uncertainty will influence 

the arrival time of the plume at drinking-water wells and, thus, the time of exposure 

(and thus also the individuals exposed due to the transient nature of base populations). 

Geohydrologic uncertainty seems less important for its influence on the wells that would 

ultimately be within the plume capture zone, because of the relatively close proximity of 

sources to the drinking-water wells and the “relatively simple” geohydrology. 

 3. The water-distribution systems distributing treated water to the three base areas that are 

the focus of the study all treat (or treated) water collected and blended from multiple 

supply wells at a single treatment plant, before distribution. Due to the relatively short 

transport times in the water-distribution system compared to groundwater-transport times, 

the temporal exposure characteristics will be governed by the groundwater transport 

and the pattern of use of drinking-water wells. The water-distribution system has little 

influence over the temporal uncertainty in exposure.

 4. Insofar as spatial uncertainty in exposed populations, the water-distribution system has 

a role to play, but due to well blending and single point of entry (treatment) to each base 

area, the spatial uncertainty is governed by the degree to which the water from different 

treatment plants are/were commingled within the water-distribution system. This aspect 

would seem to deserve more direct focus in the report and should be highlighted in an 

obvious way in summaries, conclusions, key questions, etc.

 5. While there is direct evidence of contamination of tap water, this reviewer missed any 

significant discussion of the effectiveness of treatment operations to remove the various 

contaminants present in the supply wells. Perhaps this is obvious (or I missed it) but I am 

not aware if the contaminants of interest would be aerobically degraded during treatment 

operations, adsorbed onto filter media, or oxidized by interaction with free chlorine 

present during treatment and in the water-distribution system. As a relatively minor point 

(perhaps) there may be volatilization in storage reservoirs with a free surface, and perhaps 

also adsorption/desorption to/from pipe surfaces.

Panel Members’ Premeeting Comments D19
Thomas M. Walski, PhD, PE, DEE

Comments on Water Modeling

I reviewed the documents provided to me in preparation of the Water-Modeling Expert Peer 

Review Panel Meeting, with an emphasis on the water-distribution modeling work, which is my 

area of expertise.

 1. Overview. Overall, the development of the 2004 water-distribution system model 

represents an excellent piece of work. The quality and detail of the model and calibration 

data collection is better than the usual state of the art.

 2. Need for distribution model. As good as the work is for the 2004 model, I have to 

question the development of that model as a tool to represent the behavior of the Camp 

Lejeune system in the 1968–1985 study period. While it should be possible to describe 

the physical parameters of the system during this time period by deconstructing the 

current year model, the movement of contaminants in the water-distribution system 

depends heavily on the location of demands and the operation of the source. I don’t see 

where there is sufficient data to accurately model the movement of chemicals in the 

system.

The use of a water-distribution system model to determine exposure of individuals in 

the system is important if different locations can receive different concentrations of the 

chemicals of interest. However, in this system, it appears that all of the water in each 

system passes through essentially the same treatment plant in each system. Therefore, all 

water users should get essentially the same water. If that really is the case, a water-quality 

model, no matter how good, provides very little useful information beyond that using the 

average water quality throughout the system.

From what it appears to me on initial reading of the report, virtually everyone will get the 

same exposure, which would be:

Mass contaminant introduced

x (fraction of water consumed + fraction on contaminant inhaled)

x fraction of the exposure period which individual resided/worked at Camp Lejeune

= average exposure (mass units)

If good information is available from the groundwater model on the mass introduced, it 

may be possible to calculate the above value on an annual (or other time interval basis) 

it may be possible to perform the above calculation on an annual basis to account for 

temporal variations in source concentration. I’m not certain why we need to calculate 

spatial variation in exposure if the exposure is pretty uniform.

 3. Discussion of 1968–1985 modeling. I would like to see a more thorough discussion of 

how the distribution model will be used. Most importantly, how will the model source 

concentration be determined?

 4. Limitations on historical modeling. Even if the historical source concentrations can 

be reconstructed, there is still a great deal of uncertainty in how the contaminants were 

distributed spatially because of events such as fire, pipe breaks, and valves that were 

mistakenly closed.

 5. Location of sampling. It was unclear to me where the positive volatile organic compound 

(VOC) samples were collected. If the samples were taken before the treatment plant, then 

what method was used for the volitalization of VOCs in the treatment plants as the water 

flows over weirs and is exposed to a free surface?

D20 Expert Peer Review Panel—ATSDR’s Water-Modeling Activities
 6. Timing of treatment. It would be good to have a time line of the evolution of treatment 

processes in each system. Did they use the upflow reactors during the entire period of 

interest?

 7. Controlling tank. What is a controlling tank and how does it differ from the other tanks?

 8. Tank overflow levels. I’m assuming that the tank overflow can be determined by adding 

the bottom of tank elevation to the maximum water level. I’m assuming that each system 

is a single pressure zone. However I see a wide range in overflow levels (e.g., the French 

Creek tank is at 169.8 ft whereas S29 is 153.9 ft). In a small system like this, either the 

lower tank would stay full or the taller tank would never fill. How does this work?

 9. Water quality measurement. It sounds as if water quality was measured at hydrants. 

What steps were taken to ensure that the water being sampled was representative of the 

water in the main at that point?

10. Hydrant flow tests. I like the idea of using data loggers to document hydrant flow tests. 

However, it would be good to have someone visually watch a single residual gauge to 

ensure that the pressures stabilized and to make sure that pressures were not drawn down 

too far.

If I had this many data loggers, I would have spread out their locations.

Flow tests are very good for determining pipe roughness for the current system but 

roughness values do very little to affect the distribution of contaminants in the system. 

Because of this, I would not have done as much work on flow testing.

11. Rating curve. There was a comment that the relationship between chloride and 

conductivity is not linear. That is understandable in waters where chloride is not the 

primary ion. It is still possible, however, to develop a rating curve between chloride and 

conductivity, and I’m sure the study team will figure it out.

Responses to Charge

 1. Sufficient detail. The water-distribution model probably has too much detail given the 

quality of the data that will drive it.

 2. Monthly time steps. The size of the time steps depends on the time scale of source 

variations. Given the rate of change of conditions, annual time snapshots may even be 

adequate.

 3. Level of detail. My advice is “keep it simple.” If the data don’t support a given level of 

detail, don’t go to that level of detail.

 4. Project schedule. Given the difficulty of determining historical conditions, ATSDR may 

be better off simply admitting it can’t provide precise answers on exposure and simply 

acknowledge that there is a lot of uncertainty in the results instead of building precise 

models with imprecise data. Three more years of polishing bad data won’t make the 

data better. There should be more emphasis on hindcasting/archeology/detective work 

(whatever you want to call it) to get better historical data and less on analysis.

Issues and Questions for Discussion

 1. Network model is fine; data are weak.

 2. I wouldn’t spend any more time calibrating the 2005 model.

 3. Installing 16 flowmeters for current conditions is overkill. I’d trade all those meters for 

one data point in 1980.

 4. Three models are fine.

Panel Members’ Premeeting Comments D21
 5. Two models are adequate. The interconnection should be modeled only to the extent that 

it was documented that it was open.

 6. Some simple sensitivity analysis at this time is appropriate. I would avoid getting too 

fancy because the data don’t support it.

 7. The approach is very good for current year models but doesn’t add much to the 1980 

model.

 8. If you don’t have data describing daily variations, it would be a waste of time to try to 

analyze them in the model.

 9. Unless ATSDR gets better data on daily operation, a continuous model is not justified.

10. I don’t understand what benefit would be gained from applying genetic algorithms. 

I would need to get a better understanding of what parameters are being solved for and 

how it will be done. Without knowing more, I’m skeptical.

Summary

The bottom line is that I believe ATSDR has done a great job, given the lack of historical data. 

I’m not convinced that more analysis will significantly reduce the uncertainty.

D22  Water-Modeling Activities