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.

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 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.

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 water-distribution 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.

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.

2.0 ATSDR OBJECTIVES AND GOALS

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

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

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.

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 water-distribution 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.

*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.

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.

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.

Brief Overview of Groundwater Analyses

The Hadnot Point area was contaminated as a result of leaking USTs, spills, and other waste-disposal 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

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.

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 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.

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.

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.

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.

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.

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.

3.3 Analyses of Water-Distribution Systems

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.

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.

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 water-utility 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 water-distribution 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 water-distribution systems. The data would be used to obtain present-day per capita use and diurnal curves for specific housing areas.

*Hazen-Williams C-factors.

From information provided by water-utility staff, ATSDR now understands that each water-distribution 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 water-conservation 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 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.

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

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.

4.2 Panel Discussions and Recommendations

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.

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 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 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.

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 water-distribution 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 water-distribution 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.

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.

4.2.8 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-to-date 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.

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.

*Subsequent to the panel meeting, Mr. Townsend informed ATSDR that he also lived in Tarawa Terrace from August 25, 1965–July 30, 1967.

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.

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, 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 water-distribution 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.

*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.

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.

6.4 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. water-distribution 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 water-modeling 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 water-distribution system field-testing activities. Additionally, the water-modeling team will be using simplified mixing models as a first estimate of historical exposures to contaminated drinking-water supplies.

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 page-design skills in preparing this document.

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

Appendix A—Preliminary Draft Agenda, Charge to the Panel, and Questions and Issues for Discussion on Groundwater and Water-Distribution Systems

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

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

*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 groundwater-model 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?

Questions and Issues for Discussion

• 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?

Appendix B—List of Panel Members, Presenters, and Observers

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 & Ed