WI0800039_Correspondence_19991130

MCB CAMP LEJEUNE
OPERABLE UNIT 10, SITE 35, CAMP GEIGER
AIR SPARGE TRENCH
GROUNDWATER FLOW REGIME INVESTIGATION
UTILIZING A DYE TRACE STUDY
NOVEMBER 30, 1999
1.0 Introduction
A plume of dissolved phase chlorinated hydrocarbons 2,500 feet long by 1,000 feet wide has
impacted the lower portion of the shallow aquifer at Camp Lejeune Marine Corps Base (MCB),
Camp Geiger, Site 35. An air sparge trench 100 feet long by 40 feet deep was installed within the
boundaries of the plume to perform a pilot test. The system has been in operation since March
1998. As indicated in the progress report. dated October 1999, air sparging appears to be very
effective in removing most of the dissolved phase chlorinated hydrocarbons.
It has been proposed that the trench be extended laterally to remediate the entire plume. However,
concern has been raised that the operation of the trench may cause an "air dam" to form. This might
tend to prevent some of the upgradient groundwater containing chlorinated hydrocarbons from
migrating through the trench. Instead, this groundwater might be forced around the ends of trench,
preventing remediation from occurring.
Air sparging causes the water table in the vicinity of the trench to fluctuate rapidly and
unpredictably. In some cases, artesian flow has been observed from piezometers located in the
trench. For this reason, potentiometric surface isoelevation maps cannot be used to infer
groundwater and contaminant migration pathways.
2.0 Purpose
An alternative method of evaluating this concern is a dye trace study. The objectives of the study
are:
• Determine if the pilot air sparge trench is capturing the chlorinated hydrocarbon plume.
• Determine the direction(s) of groundwater flow in the vicinity of the trench.
• Establish point-to-point hydrologic connections.
• Obtain order of magnitude estimates of the time of travel (and thus flow velocity).
The study is performed by injecting a non -toxic tracer into lower portion of the shallow aquifer and
then monitoring for its appearance in strategically located observation wells. Detection of the tracer
is accomplished by collecting water samples from the observation wells and analyzing them at a
qualified laboratory.
Camp Geiger Dye Trace Study Work Plan 1 November 30, 1999

3.0 Dye Trace Study Methodology
The investigation involves four activities:
1. Background Survey and Tracer Selection
2. Well Installation and Dye Injection
3. Monitoring
4. Report
4.0 Background Survey and Tracer Selection
Based upon a preliminary sampling of existing wells near the air sparge trench, it has been
determined that there are no background concentrations of fluorescein (CI acid yellow 73) in the
shallow aquifer at the site. Appendix A contains a copy of the analytical results. Fluorescein has
a characteristic energy absorbency peak at a specific wavelength and a characteristic energy re -
emission peak at a longer wavelength. This characteristic makes it possible to detect this tracer in
concentrations as low as 10 parts per trillion.
The potential toxicity of fluorescein has been extensively studied. In 1984, Smart reviewed the
available information concerning the toxicity of several commonly used dyes (including
fluorescein). He found that it presented minimal toxicity in mammals and "...there is no evidence
of either short or long term toxicity to dye users and those drinking water containing tracer dyes."
(It should be noted that the shallow aquifer is not currently used for drinking water, and the
dissolved chlorinated hydrocarbons would preclude its use as a potable water source long after
the dye has completely dissipated). The use of fluorescein in dye trace studies in other parts of
North Carolina has been previously approved by the North Carolina Department of Environment
and Natural Resources (NCDENR).
5.0 Well Installation and Tracer Injection
IT will install one injection well (IP-1) and three observation well pairs (OB-1 shallow and deep
[S&D], OB-2S and 2D, and OB-3S and 3D) in the vicinity of the air sparge trench. All field
activities will be performed under the oversight of a North Carolina registered Professional
Geologist.
5.1 Observation Well Installation
The three temporary shallow observation wells OB-1S, OB-2S, and OB-3S will be installed using 8
1/2 inch outside diameter (OD) hollow stem augers. They will include ten feet of screen to be
installed so that the screen bisects the water table. The depth to the water table below land surface
(BLS) will be gauged in existing observation well MP-6S, and the temporary shallow wells will be
installed to a total depth that is five feet greater.
Camp Geiger Dye Trace Study Work Plan 2 November 30, 1999

The three temporary deep observation wells OB-1D, OB-2D and OB-3D will be installed with five
feet of screen so that the screened interval is the lowest five feet of the shallow aquifer. The matrix
of the bottom 15 to 20 feet of the shallow aquifer is reported to be a coquina (shell hash) which is
quite different in appearance from the underlying Castle boundary precisely, drilling will begin
using a 2 and 7/8 inch OD mud rotary drill bit to create a pilot boring. Once a depth of 35 feet BLS
is reached, continuous split spoon samples will be collected until the boundary is identified. Once
the total well depth is known, 8 %2 OD inch hollow stem augers will be used to enlarge the boring to
the appropriate depth for well installation.
All shallow and deep wells will be constructed of two inch inside diameter (ID), Schedule 40 PVC
screen and casing. All well screens will be 0.010 -factory slot. The top of the casing shall extend at
least one foot above the adjacent land surface and shall be supplied with a J-plug type expandable,
locking well cap.
A 10/20 clean quartz sand filter pack will be installed in the annular space from the bottom of the
boring to two feet above the top of the screened interval. A layer of bentonite pellets at least two
feet thick will be installed in the annular space on top of the filter pack and allowed to hydrate. A
minimum of five gallons of potable water per well will be added to the bentonite pellets in the
shallow wells to promote hydration. The remaining annular space will be filled with a
cement/bentonite grout mixture containing not less than three percent nor more than six percent
bentonite by weight. Following installation, all wells will be developed to improve communication
with the formation.
Observation well pair OB-1 will be installed 10 feet upgradient (southwest) of the injection point to
examine the possibility that operation of the sparging trench has caused a reversal of the localized
groundwater gradient around the trench. Observation well pair OB-2 will be located 10 feet cross
gradient (northwest) of the injection point to investigate the hypothesis that sparging is causing the
chlorinated hydrocarbon plume to migrate parallel to the trench. Observation well pair OB-3 will
be installed on the northwest end of the trench (approximately 25 feet northwest of the injection
point) to study the hypothesis that air sparging is causing groundwater to migrate around the trench.
In addition, existing wells OP-1S and 1D (located in the air sparge trench) and MP-3S and 3D
(located five feet downgradient of the trench) will be sampled to explore the possibility that
groundwater is continuing to flow in the direction of the undisturbed hydraulic gradient.
5.2 Injection Well Installation
The target zone for the dye injection is the lowest portion of the shallow aquifer, which has
historically contained the highest concentrations of chlorinated solvents. Injection well IP-1 will be
installed using mud rotary methods. Initially 12-inch OD hollow stem augers will be advanced to
20 feet BLS. A six-inch diameter Schedule 40 PVC outer casing will be set in this boring. The
annular space will be filled with a cement grout that is allowed to set overnight. Once the grout has
set a 2 and 7/8 inch OD mud rotary drill bit will be advanced through this casing into the formation
to create a pilot boring. In order to identify the lower aquifer boundary precisely continuous split
spoon samples will be collected starting at 35
feet BLS. Once the boundary is identified, the boring will be enlarged to the appropriate depth
using 5 and 7/8 inch OD mud rotary drill bit.
Camp Geiger Dye Trace Study Work Plan 3 November 30, 1999

The injection well will be' istructed of two inch OD, Schedule 4k. VC screen and casing. The
well screen will be 0.020 factory slot. The top of the casing will extend at least one foot above the
adjacent land surface and shall be supplied with a J-plug type expandable, locking well cap.
A 10/20 clean quartz sand filter pack will be installed in the annular space from the bottom of the
boring to two feet above the top of the screened interval. A layer of bentonite pellets at least two
feet thick will be installed in the annular space on top of the filter pack and allowed to hydrate. The
remaining annular space will be filled with a cement/bentonite grout mixture containing not less
than three percent nor more than six percent bentonite by weight. Following installation, the
well will be developed to break up any mud cake on the boring walls and improve
communication with the formation.
5,3 Tracer Injection
Flourescein comes as a powder that is mixed with water prior to insertion. The powder contains 75
percent fluorescein by weight (the remainder is inert materials). For this study, one pound of
flourescein powder will be mixed with five gallons of potable water, so the final dilution will be a
liquid containing 15 percent fluorescein.
A Teflon tube will be inserted in the injection well and lowered until the tubing opening is one foot
above the bottom of the well. The fluorescein dye mixture will be introduced into the well through
the tubing at a rate of approximately 250 milliliters per minute. This will minimize disruption of the
existing flow patterns in the aquifer. As the dye is being injected the tubing will gradually be raised
so the opening is level with the top of the screen when the dye injection is completed.
Following dye injection, one gallon of potable water will be injected through the tubing at the rate
of 250 milliliters per minute. When that is completed the tubing will be removed from the well. An
oversized swab will be introduced into the well and pushed downwards at a rate not to exceed five
feet per minute. This will gradually displace the dye mixture into the aquifer matrix immediately
surrounding the well. Assuming an effective porosity of 20 percent, the dye mixture would be
displaced 4 V2 inches from the well. This is sufficient to introduce it into the formation, but not so
far as to affect the test results. Once the bottom of the swab has reached the top of the well screen
the swab will be tied off and left in place for the duration of the study. This will counteract any
tendency for the dye to flow back into the injection well.
Camp Geiger Dye Trace Study Work Plan 4 November 30, 1999

6.0 Monitoring and Analysis
6.1 Monitoring
After dye has been injected into the aquifer system, water samples will periodically be collected
from each of the observation wells. These include existing wells OP-1S, OP-1D, MP-3S and MP-
3D, and new observation wells OB-1S, OB-1D, OB-2S, OB-2D, OB-3S and OB-3D.
Prior to each sampling event, each well will be purged of three casing volumes to ensure that the
sample is representative of the formation. Given the anticipated depths of the wells, this would be
approximately 2.5 gallons per shallow well and 15 gallons per deep well. Assuming the entire five
foot screened interval is equally dewatered, removing 15 gallons from a deep observation well will
affect the surrounding aquifer for distance of only nine inches from the center of the well. This will
not create a large enough hydraulic gradient to artificially influence the migration of the
fluorescein.
Following purging, one 40-m1 water sample will be collected from each observation well. The
samples will be collected at the indicated times following the completion of injection:
0 hours 2 days 5 days 8 days 15 days 40 days
12 hours 3 days 6 days 9 days 20 days 50 days
24 hours 4 days 7 days 10 days 30 days
Once the dye is unambiguously detected in an observation well and its concentration is no longer
increasing, that well will be deleted from the list for further sampling.
Each groundwater sample will be labeled with the unique sample location name, sampler name, and
time and date of collection. Each sample will be sealed in its own Ziplock bag and safely packaged
for shipment. To document the sampling process, Chain of Custody and Request for Analysis
forms will be completed as the samples are collected. The background water samples will be sent to
a qualified laboratory by courier for analysis on a spectrofluorophotometer.
6.2 Water Sample Analysis
A Shimadzu Spectrofluorophotometer Model RF 5301U will be used for analyzing both the
excitation and emission maxima of fluorescent dyes. This instrument can detect the prospective
dyes in concentrations as low as 10 parts per trillion. It provides a scaled graph of the fluorescence
intensity versus excitation and/or emission wavelengths. By analyzing a sample in the synchronous
scanning mode where a broad band of the spectrum is analyzed, the sensitivity and selectivity of the
analysis is greater than single emission or excitation scan (Duley, 1986). Analysis of the water
samples will take approximately two days from receipt of the samples. IT will notify all concerned
parties immediately upon receipt of data indicating groundwater flow through the trench or in some
other direction.
Camp Geiger Dye Trace Study Work Plan 5 November 30, 1999

7.0 Dye Trace Report
IT will prepare a dye trace report that summarizes the field activities and the results of the dye
trace. IT will prepare a base map showing the injection point, observation wells and air sparge
trench. A second map will be prepared showing the locations where dye was detected above
background concentrations and the first dates when those detections occurred. Tables will be
prepared comparing the background results to those results obtained after the dye was injected.
Copies of the spectrofluorophotometer analysis will be included in an appendix. Based upon the
results of the dye trace, IT will make recommendations for future remediation alternatives at the
site.
8.0 Demobilization
Once the study has been completed the injection well and temporary observation wells will be
removed. The NCDENR guidelines for proper well abandonment will be followed in all regards.
9.0 Schedule
The following schedule is tentative. Times may vary due to differing site conditions.
November 22 (Monday): Collect background samples from OP-1S, OP-1D, MP-3S and MP-3D.
Ship to the laboratory for analysis.
November 29 (Monday): Based on the absence of fluorescein in the background samples, select
this dye for use in the study.
December 7-8 (Tuesday -Wednesday): Mobilize the driller, install the injection and observation
wells.
December 9 (Thursday):
0800 hours: Inject dye, collect 0 hour samples.
2000 hours: Purge and collect 12 hour samples.
December 10 (Friday): Purge and collect 24 hour samples at 0800 hours.
December 11 (Saturday): Purge and collect 2 day samples at 0800 hours.
December 12 (Sunday): Purge and collect 3 day samples 0800 hours.
December 13 (Monday): Purge and collect 4 day samples 0800 hours.
December 14 (Tuesday): Purge and collect 5 day samples 0800 hours.
December 15 (Wednesday): Purge and collect 6 day samples at 0800 hours.
December 16 (Thursday): Purge and collect 7 day samples at 0800 hours.
Camp Geiger Dye Trace Study Work Plan 6 November 30, 1999

December 17 (Friday): Purge and collect 8 day samples at 0800 hours.
December 18 (Saturday): Purge and collect 9 day samples at 0800 hours.
December 19 (Sunday): Purge and collect 10 day samples at 0800 hours.
December 24 (Friday): Purge and collect 15 day samples at 0800 hours.
December 29 (Wednesday): Purge and collect 20 day samples at 0800 hours.
January 8, 2000 (Saturday): Purge and collect 30 day samples at 0800 hours.
January 18, 2000 (Tuesday): Purge and collect 40 day samples at 0800 hours.
January.28, 2000 (Friday): Purge and collect 50 day samples at 0800 hours.
February 14, 2000: Preliminary report available for review.
Camp Geiger Dye Trace Study Work Plan 7 November 30, 1999

APPENDIX A
BACKGROUND SURVEY ANALYTICAL RESULTS
Camp Geiger Dye Trace Study Work Plan 8 November 30, 1999

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Amy Axon
Groundwater Section
UIC Program
1636 Mail Service Center
Raleigh, NC 27699
Re: Proposed Dye Trace Study
Site 35, MCB Camp Lejeune, NC
Dear Ms. Axon:
OHM Remediation Services Corp.
11560 Great Oaks Way, Suite 500
Alpharetta, GA 30022-2424
Tel. [phone]
Fax. [phone]
A Member of The IT Group
November 23, 1999
Further to the Draft Dye Trace Study Investigation dated November 8, 1999 that is
currently under review by your Department, IT provides herein additional information
concerning the dyes. To perform the dye trace test IT will use flourescein, rhodamine
WT, or a combination of both. Baseline testing will be performed on groundwater
samples from nearby wells to determined if either of these dyes is present in background
concentrations. This is particularly a possibility with flourescein, as it is used in a variety
of industrial products, including antifreeze and Palmolive soap. The final selection of
either or both of the dyes will be made once the baseline analytical results are available.
Sampling was conducted on November 22, 1999 with results due no later than Monday,
November 29, 1999.
Fluorescein comes as a powder that is mixed with water prior to insertion. The powder
contains 75 percent flourescein by weight (the remainder is inert materials). If no
significant background concentrations of flourescein are detected, one pound of
fluorescein powder will be mixed with five gallons of water yielding a final dilution of 15
percent fluorescein.
Rhodamine WT comes as a liquid, which typically contains 20 percent rhodamine by
weight. This liquid will be inserted without further dilution, so the rhodamine will enter
the well in a concentration of 20 percent.
Both dyes have proven especially useful in dye trace studies because they do not readily
degrade but are non -toxic to human health. Both dyes will degrade when exposed to
ultraviolet light, but that will not occur underground. In addition, both dyes will adsorb
to clay minerals. While there are no clays reported in the five-foot vertical interval that
will be injected, immediately underlying this interval is the Castle Hayne aquitard, which
is reported to contain a substantial fraction of clay minerals. These will adsorb some of
the dyes and permanently protect any deeper water bearing zones.
In addition, as the dyes disperse in the shallow aquifer they will become more and more
dilute. The concentrations selected for injection are designed to ensure that detectable

quantities reach any of the monitoring wells. However, as the ten gallons of water
containing dye begin to disperse, the concentrations will become progressively lower.
Given:
1) The aquifer is 30 feet thick with an effective porosity of 20 percent.
2) The dyes are expected to migrate laterally and vertically one foot each for every five
feet of downgradient movement.
Once the dye has migrated 65 feet downgradient the original concentration of 20 percent
(200,000 ppm) will be diluted to six parts per million. Projecting this reduction further
downgradient indicates that the dyes will be undetectable long before the nearest receptor
(Edwards Creek is approximately 500 feet downgradient of the injection point) is
reached.
Should you require additional clarification or have any additional questions, please do not
hesitate to contact us at [phone].
Sincerely,
The IT
James A. Bunn, 4., PE
Senior Project M 'lager
Pc:
Kate Landman, RPM, Code 18232
Rick Raines, EMD
Brent Rowse, ROICC
Tom McCrory, IT
Randy Smith, IT
Job File 17536
Dave Lown, NC Superfund
Diane Rossi, NC Wilmington
Roland Moreau, IT
Frank Bogle, IT
Mike Smith, Baker