c/EPA
United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
EPA/540/R-95/500
March 1999
Roy F. Weston, Inc. and I EG
Technologies Corporation
Unterdruck-Verdampfer-
Brunnen (UVB) Technology
Innovative Technology
Evaluation Report
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
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EPA/540/R-95/500
March 1999
Roy F. Weston. Inc. and
IEG Technologies Corporation
Unterdruck-Verdampfer-Brunnen
(UVB) Technology
Innovative Technology Evaluation Report
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Printed on Recycled Paper
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Notice
The information in this document has been funded by the U. S. Environmental Protection Agency (EPA) under Contract No.
68-C5-0037 to Tetra Tech EM Inc. It has been subjected to the Agency's peer and administrative reviews and has been
approved for publication as an EPA document. Mention of trade names or commercial products does not constitute an
endorsement or recommendation for use.
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Foreword
The U. S. Environmental Protection Agency (EPA) is charged by Congress with protecting the Nation's land, air, and water
resources. Under a mandate of national environmental laws, the Agency strives to formulate and implement actions leading to
a compatible balance between human activities and the ability of natural systems to nurture life. To meet this mandate, EPA's
research program is providing data and technical support for solving environmental problems today and building a science
knowledge base necessary to manage our ecological resources wisely, understand how pollutants affect our health, and prevent
or reduce environmental risks in the future.
The National Risk Management Research Laboratory is the Agency's center for investigation of technological and manage-
ment approaches for reducing risks from threats to human health and the environment. The focus of the Laboratory's research
program is on methods for the prevention and control of pollution to air, land, water and subsurface resources; protection of
water quality in public water systems; remediation of contaminated sites and groundwater; and prevention and control of
indoor air pollution. The goal of this research effort is to catalyze development and implementation of innovative, cost-
effective environmental technologies; develop scientific and engineering information needed by EPA to support regulatory and
policy decisions; and provide technical support and information transfer to ensure effective implementation of environmental
regulations and strategies.
This publication has been produced as part of the Laboratory's strategic long-term research plan. It is published and made
available by EPA's Office of Research and Development to assist the user community and to link researchers with their clients.
E. Timothy Oppelt, Director
National Risk Management Research Laboratory
in
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Abstract
This report summarizes the findings of an evaluation of the Unterdruck-Verdampfer-Brunnen (UVB) technology developed by
IEO Technologies Corporation (IEG) and demonstrated in association with Roy F. Weston, Inc. This evaluation was
conducted under the U.S. Environmental Protection Agency (EPA) Superfund Innovative Technology Evaluation (SITE)
program. The UVB treatment technology was demonstrated over a period of 12 months from April 1993 to May 1994 at March
Air Force Base (AFB) in Riverside, California.
This Innovative Technology Evaluation Report provides information from the SITE demonstration of the UVB technology that
is useful for remedial managers, environmental consultants, and other potential technology users in implementing the
technology at Superfund and Resource Conservation and Recovery Act (RCRA) hazardous waste sites.
The SITE demonstration for the UVB technology was designed with three primary and seven secondary objectives to provide
potential users of the technology with the information necessary to assess the applicability of the UVB system at other
contaminated sites. The demonstration program objectives were achieved through the collection of groundwater and soil gas
samples, as well as UVB system process ah" stream samples over a 12-month period. To meet the objectives, data were
collected in three phases: baseline sampling, long-term sampling, and dye trace sampling. Baseline and long-term sampling
included the collection of groundwater samples from eight monitoring wells, a soil gas sample from the soil vapor monitoring
well, and air samples from the three UVB process ah- streams both before UVB system startup and monthly thereafter. In
addition, a dye trace study was implemented to evaluate the system's radius of circulation cell. This study included the
introduction of fluorescent dye into the groundwater and the subsequent monitoring of 13 groundwater wells for the presence
of dye three times a week over a 4-month period.
The technology was analyzed to identify its advantages, disadvantages, and limitations. The UVB technology was evaluated
based on the nine criteria used for decision making in the Superfund feasibility study process. The overall effectiveness of the
system depends upon the time available for mass exchange between dissolved and vapor phase, the concentration gradient, the
temperature of the operating system, the interface area of the bubble (bubble size), and the contaminant gas-liquid partitioning
(mass transfer coefficient). The technology employs readily available equipment and materials. Material handling require-
ments and site support requirements are minimal. The technology as presented at the SITE demonstration is limited to
treatment of VOCs in the saturated zone and capillary fringe.
IV
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Contents
Acronyms, Abbreviations, and Symbols x
Conversion Table xiv
Acknowledgements xv
Executive Summary 1
1.0 Introduction 7
1.1 The SITE Program . 7
1.2 Innovative Technology Evaluation Report 8
1.3 Technology Description 8
1.4 Key Contacts 11
2.0 Technology Applications Analysis 12
2.1 Feasibility Study Evaluation Criteria , 12
2.1.1 Overall Protection of Human Health and the Environment 12
2.1.2 Compliance with ARARs 12
2.1.3 Long-Term Effectiveness and Permanence 12
2.1.4 Reduction of Toxicity, Mobility, or Volume Through Treatment 13
2.1.5 Short-Term Effectiveness 13
2.1.6 Implementability 14
2.1.7 Cost 14
2.1.8 State Acceptance 14
2.1.9 Community Acceptance 14
2.2 Technology Performance Versus ARARs 14
2.2.1 Comprehensive Environmental Response, Compensation, and Liability Act 15
2.2.2 Resource Conservation and Recovery Act 15
2.2.3 Clean Water Act 19
2.2.4 Safe Drinking Water Act 19
2.2.5 Clean Ah-Act 20
2.2.6 Occupational Safety and Health Administration Requirements 20
2.2.7 Technology Performance Versus ARARs During the Demonstration 20
2.3 Operability of the Technology 21
2.4 Applicable Wastes 22
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Contents (continued)
2.5 Key Features of the Treatment Technology 22
2.6 Availability and Transportability of Equipment 22
2.7 Materials handling Requirements 22
2.8 Site Support Requirements 23
2.9 Limitations of the Technology 23
3.0 Economic Analysis 25
3.1 Basis of Economic Analysis 25
3.1.1 Operation, Maintenance, and Monitoring Factors 25
3.1.2 Site Conditions and System Design Factors 26
3.2 Costs Included in the Price of the UVB Treatment System 27
3.3 Cost Categories 27
3.3.1 Site Preparation Costs 27
3.3.2 Permitting and Regulatory Requirements Costs 28
3.3.3 Capital Equipment Costs 28
3.3.4 Startup Costs 28
3.3.5 Labor Costs 28
3.3.6 Consumables and Supplies Costs 29
3.3.7 Utilities Costs 29
3.3.8 Effluent Treatment and Disposal Costs 29
3.3.9 Residuals and Waste Shipping and Handling Costs 29
3.3.10 Analytical Services Costs 30
3.3.11 Maintenance and Modifications Costs 30
3.3.12 Demobilization Costs 30
3.4 Estimated Cost of the UVB System 30
4.0 Treatment Effectiveness 33
4.1 Background 33
4.1.1 March AFB 33
4.1.2 Site 31 '. 35
4.1.2.1 Geology ! 35
4.1.2.2 Hydrogeologic Conditions 37
4.1.2.3 Site Contamination 42
4.1.3 Demonstration Objectives and Approach '. 42
4.2 Demonstration Procedures 48
4.2.1 Demonstration Preparation 48
4.2.2 Demonstration Design '. 48
4.2.2.1 Sampling and Analysis Program 50
VI
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Contents (continued)
4.2.2.2 Sampling and Measurement Locations 50
4.2.3 Sampling Methods 54
4.2.3.1 Groundwater Samples 54
4.2.3.2 Gas Samples 54
4.2.4 Quality Assurance and Quality Control Program 54
4.2.4.1 Field Quality Control Checks 54
4.2.4.2 Laboratory QC Checks 55
4.3 Demonstration Results and Conclusions 55
4.3.1 Operating Conditions 55
4.3.1.1 UVB Treatment System Configuration 55
4.3.1.2 Operating Parameters 57
4.3.1.3 System Maintenance 57
4.3.2 Results and Discussion 62
4.3.2.1 Primary Objectives '. 62
4.3.2.2 Secondary Objectives 76
4.3.3 Data Quality 83
4.3.4 Conclusions 88
5.0 UVB Technology Status 90
6.0 References 91
Appendices
A Dye Trace Study Report
B Case Studies
VII
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Figures
1-1 UVB Technology Conceptual Diagram 9
4-1 March AFB Location Map 34
4-2 Site 31 Location Map 36
4-3 Generalized Stratigraphic Cross Section 38
4-4 Interpreted Seismic Cross Section 39
4-5 Potentiometric Surface Map 41
4-6 Site 31 Source Locations 43
4-7 Well Location Map 44
4-8 Site 31 TCE Plume from In Situ Data 1 46
4-9 Sampling Locations Conceptual Diagram 49
4-10 As-Built UVB Configuration 56
4-11 As-Built UVB Internal Components 58
4-12 Aboveground System Components 59
4-13 Estimated UVB Radius of Circulation Cell Plan View '. 66
4-14 TCE Concentration vs. Time 69
4-15 DCE Concentration vs. Time 71
4-16 Dissolved Oxygen Concentration vs. Time 73
viii
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Tables
ES-l Feasibility Study Evaluation Criteria for the UVB Technology 5
2-1 Federal and State ARARs for the UVB Groundwater Treatment. 16
3-1 Costs Associated with the UVB Technology 32
4-1 Historical Site 31 Groundwater TCE Concentrations 45
4-2 Groundwater Monitoring Well Completion and Location Data 47
4-3 Groundwater Sampling and Analysis Overview 51
4-4 Air and Soil Vapor Sampling Overview 52
4-5 Dye Tracer Study Sampling Overview , 53
4-6 Maintenance Summary 60
4-7 Treatment System TCE and DCE Removal Summary 64
4-8 Aquifer TCE Concentration Summary 77
4-9 Aquifer DCE Concentration Summary 78
4-10 Soil/Vapor Well Summary 80
4-11 UVB Process Air TCE Removal Summary 82
4-12 System Operating Parameters 83
4-13 Fixed Gas Summary 84
4-14 Data Quality Outliers , 85
ix
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Acronyms, Abbreviations, and Symbols
ACL
AFB
Ag
Al
AMSL
APHA
ARAR
ASTM
ATTIC
B
Ba
BACT
Be
bgs
BS
BSD
C
Ca
CAA
Cd
CERCLA
CERI
CFR
cm
cm/s
CMDTOCAA
Co
C02
Cr
CRADA
Alternative Concentration Limit
Air Force Base
Silver
Aluminum
Above mean sea level
American Public Health Association
Applicable or Relevant and Appropriate Requirements
American Society for Testing and Materials
Alternative Treatment Technology Information Center
Boron
Barium
Best Available Control Technologies
Beryllium
Below ground surface
Blank spike
Blank spike duplicate
Degree Celsius
Calcium
Clean Air Act
Cadmium
Comprehensive Environmental Response, Compensation, and Liability Act
Center for Environmental Research Information
Code of Federal Regulations
Centimeter
Centimeter per second
Compendium of Methods for the Determination of Toxic Organic
Compounds in Ambient Air
Cobalt
Carbon dioxide
Chromium
Cooperative Research and Development Agreement
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Acronyms, Abbreviations, and Symbols (continued)
Cu
CWA
DCE
DOC
DUP
EPA
Fe
fpm
ft3
ft/day
gpd/ft2
HSWA
IEG
IRP
ITER
K
LDR
m
m3
MCAWW
MCL
Mg
mg/kg
mg/L
mm
Mn
Mo
MS
MSD
N2
NA
Na
NAAQS
NC
Copper
Clean Water Act
1,1 -Dichloroethene
Dissolved organic carbon
Duplicate
U.S. Environmental Protection Agency
Iron
Feet per minute
Cubic feet
Feet per day
Gallons per day per feet squared
Gallons per minute
Hazardous and Solid Waste Amendments
IEG Technologies Corporation
Installation Restoration Program
Innovative Technology Evaluation Report
Potassium
Horizontal hydraulic conductivity
Vertical hydraulic conductivity
Land disposal restrictions
Meter
Cubic meter
Method for the Chemical Analysis of Water and Wastes
Maximum contaminant level
Magnesium
Milligrams per kilogram
Milligrams per liter
Millimeter
Manganese
Molybdenum
Matrix spike
Matrix spike duplicate
Nitrogen
Not analyzed
Sodium
National Ambient Air Quality Standards
Not calculated
XI
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Acronyms, Abbreviations, and Symbols (continued)
Ni
NI
NPDES
NTIS
02
O&M
ORD
OSHA
OSWER
OU1
PPE
psia
POTW
PRC
PSD
QA
QAPP
QC
RCRA
RI/FS
RPD
s
SARA
Sb
scfin
SDWA
Se
Si
SIP
SITE
SVOC
SW-846
TDS
TCE
TER
TETC
Nickel
Not installed
National Pollutant Discharge Elimination System
National Technical Information Service
Oxygen
Operations and maintenance
Office of Research and Development
Occupational Safety and Health Administration
Office of Solid Waste and Emergency Response
Operable Unit 1
Parts per billion on a volume to volume basis
Personal protective equipment
Pounds per square inch absolute
Publicly owned treatment works
PRC Environmental Management, Inc.
Prevention of Significant Deterioration
Quality assurance
Quality Assurance Project Plan
Quality control
Resource Conservation and Recovery Act
Remedial Investigation/Feasibility Study
Relative percent difference
Second
Superfund Amendments and Reauthorization Act (of 1986)
Antimony
Standard cubic feet per minute
Safe Drinking Water Act
Selenium
Silicon
State Implementation Plan
Superfund Innovative Technology Evaluation
Semivolatile organic compounds
U.S. EPA Test Methods for Evaluating Solid Wastes
Total dissolved solids
Trichloroethene
Technical Evaluation Report
The Earth Technology Corporation
xii
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Acronyms, Abbreviations, and Symbols (continued)
Ti Titanium
ug/L Micrograms per liter
UCL Upper confidence limit
UVB Unterdruck-Verdampfer-Brunnen
V Vanadium
VISITT Vendor Information System for Innovative Treatment Technologies
VOC Volatile organic compounds
Weston Roy F. Weston, Inc.
Zn Zinc
in Hg Inches of mercury
%v/v Percent volume to volume basis
< Less than
> Greater than
xiii
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Conversion Factors
To Convert From
To
Multiply By
Length
Area:
Volume:
inch
foot
mile
square foot
acre
gallon
cubic foot
centimeter
meter
kilometer
square meter
square meter
liter
cubic meter
2.54
0.305
1.61
0.0929
1 4,047
'3.78
0.0283
Mass:
pound
kilogram
0.454
Energy:
Power:
Temperature:
kilowatt-hour
kilowatt
megajoule
horsepower
(°Fahrenheit - 32) °Celsius
3.60
1.34
0.556
XIV
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Acknowledgments
This report was prepared under the direction of Ms. Michelle Simon, the EPA SITE project manager at the National Risk
Management Research Laboratory in Cincinnati, Ohio. This report was prepared by Mr. Benjamin Hough, Mr. John Hoffelt,
Mr. Roger Argus, Mr. Jeff Swano, and Ms. Lisa Eminhizer of Tetra Tech EM Inc. (formerly PRC Environmental Management,
Inc). Contributors and reviewers for this report were Mr. Jeff Bannon of Roy F. Weston, Inc., and Dr. Eric Klingel of IEG
Technologies Corporation. The report was typed by Ms. Judi Lattimore, edited by Mr. Butch Fries, and reviewed by Dr.
Kenneth Partymiller and Mr. Mark Walsh of Tetra Tech.
US EPA gratefully acknowledges the following personnel. This project would never have taken place without the interest and
efforts of Dr. John Sabol, Mr. Jon Satrom, Mr. Steve Wright, and Ms. Shari McTiver of March Air Force Base; Mr. Dezo
Linbrunner of the U.S. Army Corps of Engineers; and Mr. Ralph Taber of Black and Veatch Waste Science.
xv
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Executive Summary
This report summarizes the findings of an evaluation of the
Unterdruck-Verdampfer-Brunnen (UVB) technology
developed by IEG Technologies Corporation (IEG) and
demonstrated in association with Roy F. Weston, Inc. This
evaluation was conducted under the U.S. Environmental
Protection Agency (EPA) Superfund Innovative
Technology Evaluation (SITE) program. The UVB
treatment technology was demonstrated over a period of
12 months from April 1993 to May 1994 at March Air
Force Base (AFB) in Riverside, California.
This Innovative Technology Evaluation Report provides
information from the SITE demonstration of the UVB
technology that is useful for remedial managers,
environmental consultants, and other potential technology
users in implementing the technology at Superfund and
Resource Conservation and Recovery Act (RCRA)
hazardous waste sites. Section 1.0 presents an overview of
the SITE program, describes the UVB technology, and
lists key contacts. Section 2.0 discusses information
relevant to the technology's application, including an
assessment of the technology related to the nine feasibility
study evaluation criteria used for decision making in the
Superfund process, potential applicable environmental
regulations, and operability and limitations of the
technology. Section 3.0 summarizes the costs associated
with implementing the technology. Section 4.0 presents
the site characterization, demonstration approach,
demonstration procedures, and the results and conclusions
of the demonstration. Section 5.0 summarizes the
technology status, and Section 6.0 includes a list of
references. Appendices A and B present the Dye Trace
Study Report conducted during the SITE demonstration
and case studies provided by the developer.
The UVB Technology
The UVB technology is a patented in situ groundwater
remediation technology (developed in Germany) that
combines air-lift pumping and air stripping to clean
aquifers contaminated with volatile organic compounds
(VOC). A properly installed UVB system consists of a
single well with two hydraulically separated screened
intervals installed within a single permeable zone. The
air-lift pumping occurs in response to negative pressure
introduced at the wellhead by a blower. This blower
creates a vacuum that draws water into the well through the
lower screened portion of the well. Simultaneously, air
stripping occurs as ambient air (also flowing in response to
the vacuum) is introduced through a diffuser plate located
within the upper screened section of the well, causing air
bubbles to form in the water pulled into the well. The
rising air bubbles provide the air-lift pump effect that
moves water toward the top of the well and draws water
into the lower screened section of the well. This pumping
effect is supplemented by a submersible pump that ensures
that water flows from bottom to top in the well. As the air
bubbles rise through the water column, volatile
compounds are transferred from the aqueous to the gas
phase. The transfer of volatile compounds is further
enhanced by a stripping reactor located immediately
above the air diffuser. The stripping reactor consists of a
fluted and channelized column that facilitates the transfer
of volatile compounds to the gas phase by increasing the
contact time between the two phases and by minimizing
the coalescence of air bubbles. The rising air transports
volatile compounds to the top of the well casing where
they are removed by the blower. The blower effluent is
treated before discharge using a carbon adsorption unit.
Once the upward stream of water leaves the stripping
reactor, the water falls back through the well casing and
returns to the aquifer through the upper well screen. This
return flow to the aquifer, coupled with inflow at the well
bottom, circulates groundwater around the UVB well. The
extent of the circulation pattern is known as the radius of
circulation cell, which determines the volume of water
affected by the UVB system.
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Waste Applicability
The UVB technology demonstrated at March AFB
removed trichloroethene (TCE) and 1,1-dichloroethene
(DCE) from groundwater. The developer claims that the
technology can also clean aquifers contaminated with
other organic compounds, including volatile and
semivolatile hydrocarbons. Additionally, the developer
claims that in some cases the UVB technology is capable
of simultaneous recovery of soil gas from the vadose zone.
Demonstration Objectives and Approach
The SITE demonstration for the UVB technology was
designed with three primary and seven secondary
objectives to provide potential users of the technology
with the information necessary to assess the applicability
of the UVB system at other contaminated sites. The
following primary and secondary objectives were selected
to evaluate the technology:
Primary Objectives:
(PI) Determine the concentration to which the UVB
technology reduces TCE and DCE in groundwater
discharged from the treatment system
(P2) Estimate the radius of circulation cell of the
groundwater treatment system
(P3 ) Determine whether TCE and DCE concentrations
nave been reduced in groundwater (both vertically and
horizontally) within the radius of circulation cell of
the UVB system over the course of the pilot study
Secondary Objectives:
(SI) Assess homogenization of the groundwater
within the zone of influence
(S2) Document selected aquifer geochemical
characteristics that may be affected by oxygenation
and recirculation of treated groundwater
(S3) Determine whether the treatment system induces
a vacuum in the vadose zone that suggests vapor
transport
(S4) Estimate the capital and operating costs, of
constructing a single treatment unit to remediate
groundwater contaminated with TCE and DCE
(S5) Document pre- and post-treatment off-gas
volatile organic contaminant levels
(S6) Document system operating parameters
(S7) Evaluate the presence of aerobic biological
activity in the saturated and vadose zones
The demonstration program objectives were achieved
through the collection of groundwater and soil gas
samples, as well as UVB system process air stream
samples over a 12-month period. To meet the objectives,
data were collected in three phases: baseline sampling,
long-term sampling, and dye trace sampling. Baseline and
long-term sampling included the collection of groundwater
samples from eight monitoring wells, a soil gas sample
from the soil vapor monitoring well, and air samples from
the three UVB process air streams both before UVB
system startup and monthly thereafter. In addition, a dye
trace study was implemented to evaluate the system's
radius of circulation cell. This study included the
introduction of fluorescent dye into the groundwater and
the subsequent monitoring of 13 groundwater wells for the
presence of dye three times a week over a 4-month period.
Demonstration Conclusions
Based on the UVB SITE demonstration, the following
conclusions may be drawn about the applicability of the
UVB technology:
• Results of chemical analyses of samples from the
UVB system wells indicate that the UVB treatment
system removed TCE and DCE from the groundwater.
The UVB system reduced TCE in the groundwater
discharged from the treatment system to below 5
micrograms per liter (p.g/L) in nine out of the 10
monthly monitoring events and on average by greater
than 94 percent during the period in which the system
operated without apparent maintenance problems.
The mean TCE concentration in water discharged
from the system was approximately 3 ]ig/L; however,
the upper confidence limit at the 95 percent
confidence level was calculated to be approximately 6
Hg/L. The UVB system reduced DCE to less than 1
ug/L in groundwater discharged from the treatment
system; however, the system's ability to remove DCE
could not be meaningfully estimated due to the low
(less than 4 ug/L) influent concentration of DCE.
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• The radius of circulation cell of the groundwater
treatment system was estimated by both direct and
indirect methods. The radius of circulation cell was
directly measured by conducting a dye trace study.
Based on the dye trace study, the radius of circulation
cell was measured to be at least 40 feet (12.2 meters
[m]) in the downgradient direction. The radius of
circulation cell was indirectly evaluated by (1)
modeling of the groundwater flow, and (2) analyzing
aquifer pump test data (step-test and constant rate).
Groundwater flow modeling results indicate a radius
of circulation cell of 83 feet (25.3m). The drawdown
measured in the observation wells during the pump
tests provided information on the size and shape of the
cone of depression at various pumping rates. The size
and shape of the cone of depression observed during
the pump tests was used to estimate the radius of
circulation cell of the UVB system well operating at a
constant rate of 20 gallons per minute (75.7 liters per
minute). The observed drawdown data from the pump
tests indicated a radius of circulation cell of about 60
feet (18.3 m). The pump test data are not directly
applicable to determining the radius of circulation cell
of the UVB circulation cell. An attempt was made to
indirectly evaluate the radius of circulation cell using
variations of target compound concentrations and
fluctuations of dissolved oxygen in surrounding
groundwater monitoring wells. However, these
methods did not provide a reliable or conclusive
estimate of the radius of circulation cell.
• TCE and DCE concentrations in samples from the
shallow and intermediate zone wells were reduced
both vertically and laterally except in the intermediate
outer cluster well, which showed an increase in
concentration. TCE concentrations were reduced
laterally by an average of approximately 52 percent in
the shallow and intermediate zones of the aquifer over
a 12 month period. No reduction of either TCE of
DCE was observed in the deep zone, which could be
due to limited duration of monitoring in this zone.
• A convergence and stabilization of TCE and DCE
concentrations was observed in samples from the
shallow and intermediate zones of the aquifer, which
suggest homogenization of the groundwater.
• No clear trends in the field parameters, general
chemistry, and dissolved metals results were observed
that would indicate significant precipitation of
dissolved metals, changes in dissolved organic
carbon, orthe presence of dissolved salts caused by the
increase in oxygen hi the groundwater.
Although the developer claims that the UVB system
has applications to cleanups of both groundwater and
soil gas, the system installed at Site 31 was designed to
remove halogenated hydrocarbons from the
groundwater only. The VOC concentrations and
vacuum measurements in the vapor monitoring well
indicate that migration of contaminants in the vadose
zone was not significantly affected by operation of the
UVB system as designed. Changes in system design
and operating parameters may lead to significant
transport of contaminants hi the vadose zone.
One-time capital costs for a single treatment unit were
estimated to be $180,000; variable annual operation
and maintenance costs for the first year were
estimated to be $72,000, and $42,000 for subsequent
years. Based on these estimates, the total cost for
operating a single UVB system for 1 year was
calculated to be $260,000. Since the time required to
remediate an aquifer is site-specific, costs have been
estimated for operation of a UVB system over a range
of time for comparison purposes. Therefore, the cost
to operate a single UVB system was calculated to be
$340,000 for 3 years, $440,000 for 5 years, and
$710,000 for 10 years. Additionally, the costs for
treatment per 1,000 gallons (3,785 liters [L]) of
groundwater were estimated to be $260 for 1 year,
$110 for 3 years, $88 for 5 years, and $71 for 10 years.
The costs for treatment per 1,000 liters (264.2 gallons)
of groundwater were estimated to be $69 for 1 year,
$29 for 3 years, $23 for 5 years, and $19 for 10 years.
The cost of treatment per 1,000 gallons (3,785 L)
refers to the amount of groundwater pumped through
the system. Potential users of the treatment
technology should be aware that typically 60 to 90
percent of the water pumped through the system is
recirculated water.
The results from air monitoring of the UVB treatment
system indicated that low concentrations of TCE are
being removed from the groundwater. TCE
concentrations reduced by the UVB system correlate
to trends observed in target compounds concentrations
in the inner cluster monitoring wells (that is,
increasing concentration from the baseline event to
the third monthly monitoring event with a subsequent
decrease in concentrations).
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• The temperature of the internal monitoring ports
ranged from 18.5 to 44.7 degrees Celsius; the relative
humidity ranged from 27 to 100 percent; the vacuum
pressure ranged from 13.81 to 15.03 pounds per
square inch absolute (9,709.81 to 10,567.59 kilograms
per square meter); the air flow ranged from 100 to 898
standard cubic feet per minute (47.2 to 423.9 liters per
second); and the velocity ranged from 1,109 to 9,999
feet per minute (563.4 to 5,079.5 centimeters per
second).
• Bioactivity in the soil and groundwater was not
significantly enhanced by the UVB system operation.
Other Case Studies
According to the developer, the UVB technology has been
applied at about 80 sites in Europe, and 22 systems are
operating in the United States. In Appendix B, the
developer has provided two case studies from Germany
involving trichloroethene, 1,1,1-trichloroethane, and
dichloromethane; a case from North Carolina involving
benzene, toluene, ethylbenzene, and xylene; and the
developer's interpretation of the data collected during this
SITE demonstration.
Technology Applicability
The technology was analyzed to identify its advantages,
disadvantages, and limitations. The UVB technology was
evaluated based on the nine criteria used for decision
making in the Superfund feasibility study process.
Table ES-1 presents the evaluation. The overall
effectiveness of the system depends upon the time
available for mass exchange between dissolved and vapor
phase, the concentration gradient, the temperature of the
operating system, the interface area of the bubble (bubble
size), and the contaminant gas-liquid partitioning (mass
transfer coefficient). The technology employs readily
available equipment and materials. Material handling
requirements and site support requirements are minimal.
The technology as presented at the SITE demonstration is
limited to treatment of VOCs in the saturated zone and
capillary fringe.
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Section 1
Introduction
This report summarizes the findings of an evaluation of the
Unterdruck-Verdampfer-Brunnen (UVB) technology
developed by BEG Technologies Corporation (IEG) and
demonstrated in association with Roy F. Weston, Inc. This
evaluation was conducted under the U.S. Environmental
Protection Agency (EPA) Superfund Innovative
Technology Evaluation (SITE) program. The UVB
treatment technology was demonstrated over a period of
12 months from April 1993 to May 1994 at March Air
Force Base (AFB) in Riverside, California.
This Innovative Technology Evaluation Report (ITER)
provides information from the SITE demonstration of the
UVB technology that is useful for remedial managers,
environmental consultants, and other potential technology
users in implementing the technology at Superfund and
Resource Conservation and Recovery Act (RCRA)
hazardous waste sites. Section 1.0 presents an overview of
the SITE program, describes the UVB technology, and
lists key contacts. Section 2.0 discusses information
relevant to the technology's application, including an
assessment of the technology related to the nine feasibility
study evaluation criteria, potential applicable environmental
regulations, and operability and limitations of the
technology. Section 3.0 summarizes the costs associated
with implementing the technology. Section 4.0 presents
the site characterization, demonstration approach,
demonstration procedures, and the results and conclusions
of the demonstration. Section 5.0 summarizes the
technology status, and Section 6.0 includes a list of
references. Appendices A and B present the Dye Trace
Study Report conducted during the SITE demonstration
and case studies provided by the developer.
An accompanying document to the ITER, the Draft UVB
Technology Evaluation Report (TER) (PRC 1995), has
also been prepared. The TER includes a detailed
presentation of the demonstration procedures used to
collect and analyze samples, tabulated summaries of the
demonstration results and quality assurance/quality
control (QA/QC) program used to ensure the quality and
usability of data. The document is intended to provide a
record of all information generated during, the UVB
demonstration and is intended for use during the QA/QC
review of the ITER.
This section provides background information about the
EPA SITE program, discusses the purpose of this ITER,
and describes the UVB technology. Additional
information about the SITE program, the UVB
technology, and the demonstration can be obtained by
contacting the key individuals listed at the end of this
section.
1.1 The SITE Program
SITE is a formal program established by EPA's Office of
Solid Waste and Emergency Response (OSWER) and
Office of Research and Development (ORD) in response
to the Superfund Amendments and Reauthorization Act of
1986 (SARA). The SITE program's primary purpose is to
maximize the use of alternatives in cleaning up hazardous
waste sites by encouragingthe development, demonstration,
and use of new or innovative treatment and monitoring
technologies. It consists of four major elements:
• Identify and remove obstacles to the development and
commercial use of alternate technologies.
• Structure a development program that nurtures
emerging technologies.
• Demonstrate promising innovative technologies to
establish reliable performance and cost information
for site characterization and cleanup decision-making.
• Develop procedures and policies that encourage the
selection of available alternative treatment remedies
-------
at Superfund sites, as well as other waste sites and
commercial facilities.
specific characteristics. It also discusses advantages,
disadvantages, and limitations of the technology.
Technologies are selected for the SITE Demonstration
Program through annual requests forproposals. ORD staff
review the proposals to determine which technologies
show the most promise for use at Superfund sites.
Technologies chosen must be at the pilot- or full-scale
stage, must be innovative, and must have some advantage
over existing technologies. Mobile technologies are of
particular interest.
Once EPA has accepted a proposal, cooperative
agreements between EPA and the developer establish
responsibilities for conducting the demonstrations and
evaluating the technology. The developer is responsible
for demonstrating the technology at the selected site and is
expected to pay any costs for transport, operations, and
removal of the equipment, EPA is responsible for project
planning, sampling and analysis, quality assurance and
quality control, preparing reports, disseminating
information, and transporting and disposing of treated
waste materials.
The results of the demonstration are published in two basic
documents: the SITE technology capsule and the ITER.
The SITE technology capsule provides information on the
technology, emphasizing key features of the results of the
SITE demonstration. Both the SITE technology capsule
and the ITER are intended for use by remedial managers
making a detailed evaluation of the technology for a
specific site and waste.
1.2 innovative Technology
Evaluation Report
This ITER provides information on the UVB technology
and includes a comprehensive description of the
demonstration and its results. The ITER is intended for
use by EPA remedial project managers, EPA on-scene
coordinators, contractors, and other decision makers for
implementing specific remedial actions. The ITER is
designed to aid decision makers in evaluating specific
technologies for further consideration as an option hi a
particular cleanup operation.
To encourage the general use of demonstrated
technologies, the ITER provides information regarding
the applicability of each technology to specific sites and
wastes. The ITER includes information on cost and site-
Each SITE demonstration evaluates the performance of a
technology hi treating a specific material. The
characteristics of other materials may differ from the
characteristics of the treated material. Therefore,
successful field demonstration of a technology at one site
does not necessarily ensure that it will be applicable at
other sites. Data from the field demonstration may require
extrapolation for estimating the operating ranges hi which
the technology will perform satisfactorily. Only limited
conclusions can be drawn from a single field
demonstration.
1.3 Technology Description
Roy F. Weston, Inc. in association with IEG Technologies
Corporation (IEG), conducted the pilot-scale demonstration
of the UVB technology (Figure 1-1). The UVB system is
an in situ remediation technology for the cleanup of
aquifers contaminated with volatile organic compounds
(VOCs). The UVB system is a patented technology
developed hi Germany that consists of a single well with
two hydraulically separated screened intervals installed
within a single permeable zone. The UVB system
combines air-lift pumping and air stripping to facilitate the
removal of volatile compounds (Weston 1992). Air-lift
pumping effects are enhanced by adding a submersible
pump to transport water from the well bottom to the upper
hydraulic section. Stripped volatile compounds are
removed from the well head by a blower and are captured
hi a carbon adsorption unit before releasing the stripped air
to the atmosphere. Once stripped of volatile compounds,
treated water reinfiltrates into the aquifer through the
upper screen of the UVB system. The movement of water
through the UVB system creates a hydraulic circulation
pattern in the aquifer, which constitutes the UVB
circulation cell.
The air-lift effect occurs hi response to negative pressure
introduced at the well head by a blower. This blower
creates a vacuum that draws water into the well through the
lower screened portion of the well. Simultaneously,
ambient air (also flowing hi as a response to the applied
vacuum) is introduced through a diffuser plate, causing
bubbles to form in the water that is pulled into the well.
The rising air bubbles provide the air-lift pump effect that
moves water toward the top of the well and causes a
suction effect at the well bottom. This pumping effect may
-------
Carbon Adsorption Units
Blower
-Monitoring Well
Ambient Air
• Monitoring Well
Saturated Zone~
. Stripping
Reactor
-Air Sieve
Plate
Groundwater
Table
Pac&er-
Groundwater flow
Groundwater
intake
Figure 1-1. UVB technology conceptual diagram.
-------
be supplemented by a submersible pump that ensures that
water flows from bottom to top in the well. As the air
bubbles rise through the water column, transfer of volatile
compounds from the aqueous to gas phase occurs. The
rising air transports volatile compounds to the top of the
well casing where they are removed by the blower. The
blower effluent is treated using a carbon adsorption unit
before discharge to the ambient air.
The upper portion of the well is hydraulically separated
from the lower portion by a packer, as shown in Figure 1-
1. However, a small (3-inch or 7.6 centimeter [cm]) water
inlet pipe inserted through the packer connects the two
sections of the well. Water from the bottom of the aquifer
flows into the well through a screened portion of the casing
in response to a pressure gradient, air-lift pump effect, and
a submersible pump. The pressure gradient from the upper
well to the lower well results from the vacuum applied in
the upper well. These forces then draw water up through
the inlet pipe from the lower part of the well and into the
upper part of the well, where it is introduced to the air
diffiiser.
Stripping is initiated by the air sieve phi hole plate that
disperses air bubbles within the water column to increase
transfer of volatile compounds from the aqueous to the
gaseous phase. This process is further enhanced by a
fluted and channelized column that facilitates the transfer
of volatile compounds to the gaseous phase by increasing
contact time between the two phases and by minimizing
the coalescence of air bubbles. Volatilization is enhanced
by the concentration gradient between the aqueous and gas
phases and the negative (reduced) pressure in the upper
hydraulic section of the UVB well. Volatilization depends
on the solubility, molecular weight, and vapor pressure of
the compounds treated and the nature of the air-water
interface through which the compounds must pass. The
effectiveness of vapor stripping depends on the time
available for mass exchange between dissolved and vapor
phases, the concentration gradient (between the two
phases), the operating temperature, the interface area of
the bubble (bubble size), and the contaminant gas-liquid
partitioning (mass transfer coefficient).
The overall stripping zone of the UVB system extends
from the diffiiser plate to the top of the water column. To
maximize volatilization in the stripping zone, the diffuser
plate and stripping reactor are positioned at a depth that
optimizes the reach of the stripping zone and the volume of
air flow into the system. The down-well components of
the UVB system have been designed with leveling ballast
that allows the system to be free floating. This feature
allows the system to compensate for fluctuations in
groundwater elevation during operation and, thereby,
maintain maximum volatilization.
The upward stream of water in the well is drawn up to a
maximum height of about 3 feet (0.9 meters [m]) above the
groundwater table hi response to the vacuum and air-lift
pumping. Once the hydrostatic head (height of the water
column drawn up into the well casing) exceeds the sum of
the buoyancy (air-lift) force and pressure head (vacuum)
force in the well, the water falls back through the well
casing and returns through the upper well screen to the
aquifer. This return flow to the aquifer coupled with
inflow at the well bottom circulates groundwater around
the UVB well. The extent of the circulation pattern is
known as the radius of circulation cell and determines the
volume of water affected by the UVB system when there is
negligible natural groundwater flow.
The radius of circulation cell and shape of the circulation
pattern are directly related to the aquifer properties. The
circulation pattern is further modified by natural
groundwater flow that skews the pattern in the
downgradient direction. Numerical simulation of the
UVB operation indicates that the radius of circulation cell
is largely controlled by anisotropy (horizontal [KJ and
vertical [Kv] hydraulic conductivity), aquifer thickness,
and, to a lesser extent, well design (Small and Narasimhan
1993). In general, changes that favor horizontal flow over
vertical flow such as a small ratio of screen length to
aquifer thickness, anisotropy, horizontal heterogeneities
such as low permeability layers, or increased aquifer
thickness will increase the radius of circulation cell (Small
and Narasimhan 1993).
According to the developer, the radius of circulation cell
can be estimated using numerical algorithms and
graphical solutions developed by Dr. Bruno Herrling of
the University of Karlsruhe, Germany. The Herrling
model is based on theoretical assumptions that relate K,/
Kv, well discharge rate, Darcy velocity of the groundwater
flow, and aquifer thickness to the distance between the
UVB well and the stagnation point (Herrling et al. 1991).
The distance from the UVB system to the stagnation point
determined by the Herrling model is essentially equivalent
to the radius of circulation cell of the system. The model
was not thoroughly assessed as part of the evaluation of the
UVB technology; however, IEG believes the model is
10
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valid based on empirical data generated from operation of
the UVB system at other sites in Germany and the United
States. As a general rule, IEG estimates that the system
radius of circulation cell is approximately 2.5 times the
distance between the upper and lower screen intervals.
Groundwater within the radius of circulation cell includes
both treated and untreated water. A portion of the treated
water discharged to the upper screen is recaptured within
the circulation cell. Treated water not captured by the
system leaves the circulation cell in the downgradient
direction. The percentage of treated water recycled within
the UVB system (IEG estimates up to 90 percent) is related
to the radius of circulation cell and is a function of the ratio
of K,/Kv. The larger the radius of circulation cell and the
larger the K^ to Kv ratio values, the smaller the percentage
of recycled water. The recycled treated water dilutes
influent contaminant concentrations.
The developer presents the UVB technology as a highly
efficient in situ system requiring minimal maintenance.
According to BEG, the UVB technology in some cases is
also capable of simultaneous recovery of soil gas from the
vadose zone and treatment of contaminated groundwater
from the aquifer as a result of the in situ vacuum. For soil
gas recovery, a screened portion would extend from below
the water table to above the capillary zone in the well
(Weston 1992).
1.4 Key Contacts
Additional information on the UVB technology and the
SITE program can be obtained from the following sources:
The UVB Technology
JeffBannon
Roy F. Weston, Inc.
14724 Ventura Boulevard, Suite 1000
Sherman Oaks, CA 91403
(818)382-1808
FAX: (818) 382-1801
Dr. Eric Klingel
IEG Technologies
P.O. Box 6091
Mooresville,NC28117
(704) 660-1673
FAX: (704) 660-1673
The SITE Program
Robert A. Olexsey
Director, Land Remediation and
Pollution Control Division
U.S. Environmental Protection Agency
26 West Martin Luther King Drive
Cincinnati, OH 45268
(513)569-7861
FAX: (513) 569-7620
Michelle Simon
EPA SITE Project Manager
U.S. Environmental Protection Agency
26 West Martin Luther King Drive
Cincinnati, OH 45268
(513)569-7469
FAX: (513) 569-7676
Information on the SITE program is available through the
following on-line information clearinghouse: the Vendor
Information System for Innovative Treatment Technologies
(VISITT) (Hotline: 800-245-4505) database contains
information on 154 technologies offered by 97 developers.
Technical reports may be obtained by contacting U. S.
EPA/NSCEP, P. O. Box 42419, Cincinnati, Ohio 45242-
2419, or by calling 800-490-9198.
11
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Section 2
Technology Applications Analysis
This section evaluates the general applicability of the
UVB technology to contaminated waste sites. Information
presented in this section is intended to assist decision
makers in screening specific technologies for a particular
cleanup situation. This section presents the advantages,
disadvantages, and limitations of the technology and
discusses factors that have a major impact on the
performance and cost of the technology. The analysis is
based both on the demonstration results and on available
information from other applications of the technology.
2.1 Feasibility Study Evaluation
Criteria
This section assesses the UVB technology against the nine
evaluation criteria used for conducting detailed analyses
of remedial alternatives in feasibility studies under the
Comprehensive Environmental Response, Compensation,
and Liability Act (CERCLA) (EPA 1988a).
2.1.1 Overall Protection of Human
Health and the Environment
The UVB technology provides both short- and long-term
protection to human health and the environment by
removing contaminants in groundwater and by preventing
further migration of contaminants in the groundwater.
The UVB technology removes VOCs from groundwater
by stripping them from the groundwater and transferring
them to the gas phase for subsequent treatment. The
treated groundwater is discharged back into the aquifer
without bringing the water to the surface; thus,
contaminants are removed from the groundwater with
minimal exposure to on-site workers and the community.
Exposure from air emissions is minimized through the
removal of contaminants in the system's air process
stream using carbon adsorption units before discharge to
the atmosphere.
The UVB system creates a capture zone hi the aquifer that
limits the migration of contaminated groundwater.
However, a portion of the groundwater can leave the
circulation cell in the downgradient direction. The
escaping groundwater may present a concern if high
concentrations of dissolved contaminants are present.
More than one pass through the system may be required to
reach remediation goals for high concentrations of
dissolved contaminants.
2.1.2 Compliance with ARARs
General and specific applicable or relevant and
appropriate requirements (ARARs) identified for the UVB
technology are presented in Section 2.2. Compliance with
chemical-, location-, and action-specific ARARs should
be determined on a site-specific basis; however, location-
and action-specific ARARs generally can be met.
Compliance with chemical-specific ARARs depends on
the efficiency of the UVB system to remove contaminants
from the groundwater. To meet chemical-specific
ARARs, contaminated groundwater may require multiple
passes through the treatment system. Contaminated
concentrations may increase during initial operation;
however, as the UVB circulating cell is established, the
influent concentrations should be diluted to below levels
requiring more than one pass.
2.1.3 Long-Term Effectiveness and
Permanence
The UVB system permanently removes contaminants
from the groundwater; however, treatment residuals
(activated carbon) are not destroyed on-site and require
proper off-site treatment and disposal. Treatment of
dissolved phase VOCs in the groundwater and air
emissions using air stripping and carbon adsorption units
are permanent solutions for the removal of contaminants.
12
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Both of these techniques are well-demonstrated and
effectively remove volatile contaminants from groundwater
and air. The UVB system removes dissolved phase VOCs
by air stripping the groundwater in the wellbore followed
by reinfiltration of the treated groundwater into the
aquifer. The reinfiltration of treated water creates a
recirculation pattern of groundwater in the surrounding
aquifer. The continuous flushing of the saturated zone
with recirculated treated water facilitates the partitioning
of adsorbed, absorbed, and liquid contaminants to the
dissolved phase through increased dissolution, diffusion,
and desorption. Increased partitioning through these
processes is driven by increased groundwater flow rates
within the system's radius of circulation cell and an
increase in the concentration gradient established by the
reinjection and recirculation of treated water hi the
aquifer. These processes provide an effective long-term
solution to aquifer remediation by affecting contaminants
in the saturated zone. The magnitude of residual risk from
adsorbed, absorbed, or liquid contaminants can be
controlled by extending the length of tune that the system
operates, thereby allowing groundwater to recirculate
through the treatment system in multiple passes.
2.1.4 Reduction ofToxicity, Mobility, or
Volume Through Treatment
Contaminant concentrations may increase during the
initial operation of the UVB system due to increased
groundwater flow and partitioning of VOCs to the
dissolved phase. This initial period of increased
concentrations is followed by a subsequent decrease in
concentration. According to the developer, this
contaminant concentration pattern is typical of the UVB
operation and is the result of the system increasing the
partitioning of contaminants to the dissolved phase. The
partitioning of contaminants to the dissolved phase is
enhanced by the higher than natural groundwater flow
rates within the system's radius of circulation cell and by
an increase in the concentration gradient established by the
reinjection and recirculation of treated water within the
aquifer.
The subsequent reduction of contaminant concentrations
in the groundwater is due to the active removal of
contaminants via air stripping. The treatment process
reduces the concentration of dissolved phase VOC
contaminants hi the groundwater by transferring the
contaminants from the groundwater to a gas phase where
they are concentrated in carbon adsorption units for
disposal or recycling. The reduction of contaminant
concentrations may also be caused by the dilution of
contaminated water with treated water. After being
treated, the groundwater reinfiltrates into the aquifer,
where it mixes with untreated groundwater in the radius of
circulation cell. The percentage of treated water recycled
within the UVB system (IEG estimates up to 90 percent) is
related to the radius of circulation cell and is a function of
the aquifer anisotropy (K^/K^ ratio). The smaller the
radius of circulation cell and the smaller the ratio K,, to K^,
the larger the percentage of recycled water.
In addition to reducing contaminant concentrations in the
aquifer, the UVB system affects contaminant mobility.
Initially, contaminant mobility within the UVB system's
radius of circulation cell is increased by the partitioning of
contaminants into solution (dissolved phase) and by the
increased groundwater flow velocity near the UVB
system. The increased contaminant mobility facilitates
the long-term remediation of the groundwater within the
system's radius of circulation cell. The developer claims
that the UVB system also limits contaminant mobility by
capturing contaminated groundwater from the migrating
plume and recirculating treated water within the radius of
circulation cell.
2.1.5 Short-Term Effectiveness
Potential short-term risks presented during system
operation to workers, the community, and the environment
include increased contaminant concentrations in the
groundwater during initial operation of the UVB and
exposure to contaminants in the system' s air stream. Since
all treatment of groundwater occurs in situ, potential initial
increases in contaminant concentration do not pose a
significant risk to on-site workers or the community. In
addition, once the circulation cell has been established,
concentrations should decrease due to active removal of
contaminants by the treatment system and dilution caused
by the reinfiltration and recirculation of treated
groundwater within the system's radius of circulation cell.
Because the technology removes VOCs through air
stripping, abatement controls must be provided for these
emissions. Adverse impacts from the air stream are
mitigated by passing the emissions through carbon
adsorption units before discharge to the ambient air.
Implementation of the UVB system involves (1) site
preparation, (2) installation of the system well, internal air
stripping well components, and carbon adsorption units,
13
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(3) installation of monitoring wells (if not already
present), and (4) operation, monitoring, and maintenance.
Well installation activities can be completed using
conventional drilling techniques. Minimal adverse
impacts to the community, workers, or the environment
are anticipated during site preparation or installation of the
treatment system or monitoring wells. Additionally,
exposure from air emissions during operation, monitoring,
and maintenance are minimized through the removal of
contaminants in the system's air process stream using
carbon adsorption units before discharge to the ambient
air.
2.1.6 Implementability
Site preparation and access requirements for the
technology are minimal. The site must be accessible to
large trucks. The space requirements for the above-ground
components of the UVB system including the UVB
system well, carbon adsorption units, blower, and piping
are approximately 100 to 700 square feet; 300 square feet
(27.9 m2) is typical. The equipment and materials that
constitute this remedial alternative are commercially
available and are proven in conventional applications at
sites with similar conditions. Installation and operation of
the UVB system is anticipated to involve few
administrative difficulties. Once the well has been
completed, the treatment system can be operational within
1 day if all necessary equipment, utilities, and supplies are
available. Operation and monitoring can be performed by
a trained field technician and do not require a specialist.
However, the system should be maintained by personnel
intimately familiar with operation of the UVB. Other
services and supplies required to implement the UVB
system could include a drill rig, carbon adsorption
regeneration/disposal, laboratory analysis to monitor
system performance, and electrical utilities.
2.1.7 Cost
The assumptions and calculations for the UVB system
costs are presented in Section 3.0. Capital cost to install a
UVB system is $180,000. This cost includes site
preparation, permitting and regulatory requirements,
equipment costs, startup, and demobilization. Annual
operation, monitoring and maintenance costs for the first
year are estimated to be $72,000 and for subsequent years
$42,000. Based on these estimates, the total cost for
operating a single UVB system for 1 year was calculated to
be $260,000. Since the tune required to remediate an
aquifer is site-specific, costs have been estimated for
operation of the UVB system over a range of time for
comparison purposes. Therefore, the cost to operate a
single UVB system was calculated to be $340,000 for 3
years, $440,000 for 5 years, and $710,000 for 10 years.
Additionally, the costs for treatment per 1,000 gallons
(3,785 liters [L]) of groundwater were estimated to be
$260 for 1 year, $110 for 3 years, $88 for 5 years, and $71
for 10 years. The cost of treatment per 1,000 gallons
(3,785 L) refers to the amount of groundwater pumped
through the system. Potential users of the treatment
technology should be aware that IEG estimates typically
60 to 90 percent of the water pumped through the system is
recirculated water.
2.1.8 State Acceptance
State acceptance is anticipated because the UVB system
uses well-documented and widely accepted processes to
remove VOCs from groundwater and to treat the process
air emissions. Also, the UVB system is small and
relatively easy to transport, operate, and manage. If
remediation is conducted as part of Resource Conservation
and Recovery Act (RCRA) corrective actions, state
regulatory agencies may require that permits be obtained
before implementing the system, such as a permit to
operate the treatment system, an air emissions permit, and
a permit to store contaminated soil cuttings and purge
water for greater than 90 days if these items are considered
hazardous wastes.
2.1.9 Community Acceptance
The system's low profile, limited space requirements,
minimal maintenance and monitoring, and low noise level
coupled with minimal short-term risks to the community
and the permanent removal of contaminants through hi
situ processes make this technology likely to be accepted
by the public.
!
2.2 Technology Performance Versus
ARARs
This section discusses specific federal environmental
regulatory requirements pertinent to the transport,
treatment, storage, and disposal of treatment residuals
generated during operation of the UVB system, and
analyzes these regulations in lieu of the demonstration
results. The regulations that apply to a particular
14
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remediation activity will depend on the type of
remediation site and the type of waste being treated. Table
2-1 provides a summary of regulations discussed in this
section. In addition to the federal requirements, state and
local regulatory requirements, which may be more
stringent, also must be addressed by remedial managers.
2.2.1 Comprehensive Environmental
Response, Compensation, and
Liability Act
CERCLA as amended by SARA provides for federal
authority to respond to releases or potential releases of any
hazardous substance into the environment, as well as to
releases of pollutants or contaminants that may present an
imminent or significant danger to public health and
welfare or the environment. Remedial alternatives that
significantly reduce the volume, toxicity, or mobility of
hazardous materials and that provide long-term protection
are preferred. Selected remedies must also be cost
effective and protective of human health and the
environment.
Contaminated water treatment using the UVB system
takes place on-site, while residual wastes generated during
the installation, operation, and monitoring of the system
may require treatment or disposal either on-site or off-site.
On-site actions must meet all substantive state and federal
ARARs.
Substantive requirements pertain directly to actions or
conditions in the environment (for example, groundwater
effluent and air emission standards). Off-site actions must
comply with legally applicable substantive and
administrative requirements. Administrative requirements,
such as permitting, facilitate the implementation of
substantive requirements. On-site remedial actions must
comply with federal and, if more stringent, state ARARs.
ARARs are determined on a site-by-site basis and may be
waived under six conditions: (1) the action is an interim
measure, and the ARAR will be met at completion; (2)
compliance with the ARAR would pose a greater risk to
health and the environment than noncompliance; (3) it is
technically impracticable to meet the ARAR; (4) the
standard of performance of an ARAR can be met by an
equivalent method; (5) a state ARAR has not been
consistently applied elsewhere; and (6) fund balancing
where ARAR compliance would entail such cost in
relation to the added degree of protection or reduction of
risk afforded by that ARAR that remedial action at other
sites would be jeopardized. These waiver options apply
only to SuperfUnd actions taken on site, and the waiver
must be clearly justified. Off-site remediations are not
eligible for ARAR waivers, and all substantive and
administrative applicable requirements must be met.
The contamination addressed by the UVB demonstration
at March AFB was attributed to past disposal of spent
solvents. The UVB system was designed to remove VOCs
from the groundwater by transferring the contaminants
from the aqueous phase to the gaseous phase and
subsequently treating the resulting air stream through
carbon adsorption units. Spent granular activated carbon
is generated during treatment of air emissions. Other
sources of waste are soil and contaminated groundwater
derived from system installation and regular monitoring of
the aquifer. Given these wastes (typical of operation of a
UVB system), the following additional statutes and
regulations pertinent to use of a UVB system were
identified: (l)RCRA,(2)theCleanWaterAct(CWA),(3)
the Safe Drinking Water Act (SDWA), (4) the Clean Air
Act (CAA), and (5) Occupational Safety and Health
Administration (OSHA) regulations. These five ARARs
are discussed below. Specific ARARs that were
applicable to the UVB technology demonstration are
presented in Table 2-1.
2.2.2 Resource Conservation and
Recovery Act
RCRA, as amended by the Hazardous and Solid Waste
Amendments (HSWA) of 1984, regulates management
and disposal of municipal and industrial solid wastes. The
EPA and RCRA-authorized states (listed in 40 Code of
Federal Regulations [CFR] Part 272) implement and
enforce RCRA and state regulations.
The UVB system has been used to treat water
contaminated with a variety of organic materials including
solvents and petroleum hydrocarbons. Contaminated
water treated by the UVB system will most likely be
hazardous or sufficiently similar to hazardous waste so
that RCRA standards may be requirements. Generally,
RCRA does not apply to in situ groundwater treatment
because the contaminated groundwater may not be
considered hazardous waste while it is in the aquifer; the
contaminated groundwater becomes regulated
("generated") once it leaves the aquifer. The applicability
of RCRA requirements to the UVB treatment system
requires a determination of whether or not the
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contaminated groundwater leaves the aquifer for
treatment in the UVB system well. Potential pertinent
RCRA requirements are discussed below.
The presence of RCRA-defined hazardous waste
determines whether RCRA regulations apply to the UVB
technology. If wastes generated while installing,
monitoring, or operating the technology are determined to
be hazardous according to RCRA, all RCRA requirements
regarding the management and disposal of hazardous
wastes must be addressed. RCRA regulations define
hazardous wastes and regulate their transport, treatment,
storage, and disposal. Wastes defined as hazardous under
RCRA include characteristic and listed wastes. Criteria
for identifying characteristic hazardous wastes are
included in 40 CFR Part 261 Subpart C. Listed wastes
from nonspecific and specific industrial sources, off-
specification products, spill cleanups, and other industrial
sources are itemized in 40 CFR Part 261 Subpart D.
If contaminated groundwater is determined to be a
hazardous waste and is extracted (during system
monitoring or is interpreted as extraction during system
operation) for treatment, storage, or disposal, the
requirements for a hazardous waste generator will apply.
Requirements for hazardous waste generators are
specified in 40 CFR Part 262 and include obtaining an
EPA identification number. If hazardous wastes are
treated by the UVB treatment system, the owner/operator
of the treatment or disposal facility must obtain an EPA
identification number and a RCRA permit from EPA or a
RCRA-authorized state. RCRA requirements for permits
are specified in 40 CFR Part 270. In addition to the
permitting requirements, owners and operators of
facilities that treat hazardous waste must comply with 40
CFR Part 264.
Air emissions from operation of the UVB are subject to
RCRA regulations on air emissions from hazardous waste
treatment, storage, or disposal* operations and are
addressed in 40 CFR Part 264 and 265, Subparts AA and
BB. The air emission standards apply to treatment,
storage, or disposal units subject to the RCRA permitting
requirements of 40 CFR part 270 or hazardous waste
recycling units that are otherwise subject to the permitting
requirements of 40 CFR Part 270.
Spent granular activated carbon, soil, and purge and
decontamination water generated during installation,
operation, and monitoring of the treatment system must be
stored and disposed of properly. If the water treated is a
listed waste, treatment residues will be considered listed
wastes (unless RCRA delisting requirements are met). If
the treatment residues are not listed wastes, they should be
tested to determine if they are RCRA characteristic
hazardous wastes. If the residuals are not a RCRA
hazardous waste and do not contain free liquids, they can
be disposed of at a nonhazardous waste landfill. If the soil
cutting, purge/decontamination water, or spent carbon is
hazardous, the following RCRA standards apply.
Title 40 CFR Part 262 details standards for generators of
hazardous waste. These requirements include obtaining
an EPA identification number, meeting waste accumulation
standards, labeling wastes, and keeping appropriate
records. Part 262 allows generators to store wastes up to
90 days without a permit and without having interim status
as a treatment, storage, and disposal facility. If treatment
residues are stored on-site for 90 days or more, 40 CFR
Part 265 requirements apply.
Any facility (on-site or off-site) designated for permanent
disposal of hazardous wastes must be in compliance with
RCRA. Disposal facilities must fulfill permitting, storage,
maintenance, and closure requirements contained in 40
CFR Parts 264 through 270. In addition, any authorized-
state RCRA requirements must be fulfilled. If treatment
residues are disposed of off-site, 40 CFR Part 263
transportation standards apply.
Soils classified as hazardous waste are subject to land
disposal restrictions (LDR) under both RCRA and
CERCLA. Applicable RCRA requirements could include
(1) a Uniform Hazardous Waste Manifest if the treated
soils are transported, (2) restrictions on placing soils in
land disposal units, (3) time limits on accumulating treated
soils, and (4) permits for storing treated soils.
The UVB system could also be used to treat contaminated
water at RCRA-regulated facilities. Requirements for
corrective action at RCRA-regulated facilities are
provided in40 CFRPart 264, Subpart F (promulgated) and
Subpart S (proposed). These subparts also apply to
remediation at Superfund sites. Subparts F and S include
requirements for initiating and conducting RCRA
corrective actions, remediating groundwater, and ensuring
that corrective actions comply with other environmental
regulations. Subpart S also details conditions under which
particular RCRA requirements may be waived for
temporary treatment units operating at corrective action
18
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sites. Thus, RCRA mandates requirements similar to
CERCLA, and as proposed, allows treatment units such as
the UVB treatment system to operate without full permits.
Water quality standards included in RCRA (such as
groundwater monitoring and protection standards), CWA,
and SDWA are appropriate cleanup standards and apply to
discharges of treated water or reinjection of treated
groundwater. The CWA and SDWA are discussed below.
2.2.3 Clean Water Act
The CWA is designed- to restore and maintain the
chemical, physical, and biological quality of navigable
surface waters by establishing federal, state, and local
discharge standards. Since all treated water is reinjected
into the aquifer during operation of the UVB system, only
purge and decontamination water generated during system
monitoring may be regulated under the CWA if it is
discharged to surface water bodies or publicly owned
treatment works (POTW). On-site discharges to surface
water bodies must meet substantive National Pollutant
Discharge Elimination System (NPDES) requirements,
but do not require an NPDES permit. Off-site discharges
to a surface water body require an NPDES permit and must
meet NPDES permit limits. Discharges to a POTW are
considered an off-site activity, even if an on-site sewer is
used. Therefore, compliance with substantive and
administrative requirements of the national pretreatment
program is required. General pretreatment regulations are
included hi 40 CFR Part 403. Any local or state
requirements, such as state antidegradation requirements,
must also be identified and satisfied.
2.2.4 Safe Drinking Water Act
The SDWA, as amended in 1986, requires EPA to
establish regulations to protect human health from
contaminants hi drinking water. The legislation
authorizes national drinking water standards and a joint
federal-state system for ensuring compliance with these
standards. The SDWA also regulates underground
injection of fluids and includes sole-source aquifer and
wellhead protection programs.
The National Primary Drinking Water Standards are found
at 40 CFR Parts 141 through 149. SDWA primary or
health-based, and secondary or aesthetic maximum
contaminant levels (MCL) will generally apply as cleanup
standards for water that is, or may be, used for drinking
water supply. In some cases, such as when multiple
contaminants are present, alternative concentration limits
(ACL) may be used. CERCLA and RCRA standards and
guidance should be used hi establishing ACLs (EPA
1987a).
To date, no UVB installation has been interpreted by
federal or state agencies as underground injection since
treated water is placed into the subsurface environment. If
this interpretation is applied, water discharged from the
UVB system will be regulated by the underground
injection control program found in CFR 40 Parts 144 and
145. Injection wells are categorized in Class I through V,
depending on their construction and use. Reinjection of
treated water involves Class IV (reinjection) or Class V
(recharge) wells and should meet requirements for well
construction, operation, and closure. If the groundwater,
after treatment, still contains hazardous waste then its
reinjection into the upper portion of the aquifer would be
subject to 40 CFR Part 144.13, which prohibits Class IV
wells. Technically, the UVB technology could be
considered a Class IV well because of Hie following
definition in 40 CFR Part 144.6(d):
"(d) Class IV. (1) Wells used by generators of hazardous
waste or of radioactive waste, by owners or operators of
hazardous waste management facilities, or by owners or
operators of radioactive waste disposal sites to dispose of
hazardous waste or radioactive waste into a formation
which within one-quarter (V£) mile of the well contains an
underground source of drinking water.
(2) Wells used by generators of hazardous waste or of
radioactive waste, by owners or operators of hazardous
waste management facilities, or by owners or operators of
radioactive waste disposal sites to dispose of hazardous
waste or radioactive waste above a formation which within
one-quarter (V4) mile of the well contains an underground
source of drinking water.
(3) Wells used by generators of hazardous waste or
owners or operators of hazardous waste management
facilities to dispose of hazardous waste, which cannot be
classified under paragraph (a)(l) or (d) (1) and (2) of this
section (e.g., wells used to dispose of hazardous waste into
or above a formation which contains an aquifer which has
been exempted pursuant to §146.04)."
The sole-source aquifer protection and wellhead
protection programs are designed to protect specific
19
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drinking water supply sources. If such a source is to be
remediated using the UVB system, appropriate program
officials should be notified, and any potential regulatory
requirements should be identified. State groundwater
antidegradation requirements and water quality standards
may also apply.
2.2.5 Clean Air Act
The CAA and the 1990 amendments establish primary and
secondary ambient air quality standards for protection of
public health as well as emission limitations for certain
hazardous air pollutants. Permitting requirements under
CAA are administered by each state as part of State
Implementation Plans (SIP) developed to bring each state
into compliance with National Ambient Ah- Quality
Standards (NAAQS). The ambient ah- quality standards
for specific pollutants apply to the operation of the UVB
system because the technology ultimately results in an
em ission from a point source to the ambient air. Allowable
emission limits for operation of a UVB system will be
established on a case-by-case basis depending on the type
of waste treated and whether the site is hi an attainment
area of the NAAQS. Allowable emission limits may be set
for specific hazardous air pollutants, particulate matter,
hydrogen chloride, or other pollutants. If the site is in an
attainment area, the allowable emission limits may still be
curtailed by the increments available under Prevention of
Significant Deterioration (PSD) regulations. Typically,
an air pollution abatement device, such as a carbon
adsorption unit, will be required to remove VOCs from the
UVB system's process air stream before discharge to the
ambient air.
EPA has developed a guidance document for control of
emissions from air stripper operations at CERCLA sites,
"Control of Air Emissions from Superfund Air Strippers at
Superfund Groundwater Sites" (EPA 1989). The local SIP
may include specific standards to control air emissions of
VOCs in ozone nonattainment areas. The EPA guidance
suggests that the sources most in need of controls are those
with an actual emissions rate of total VOCs in excess of 3
pounds per hour (1.4 kilograms per hour), or 15 pounds per
day (6.8 kilograms per day), or a potential (calculated) rate
of 10 tons per year (9,072 kilograms per year) (EPA 1989).
Based on the average conditions measured during the first
6 months of UVB system operation, the concentration of
TCE in the pretreatment air emissions (before passing
through the carbon adsorption units) was 2.0 x 10~5 pounds
per hour (9.1 x 1Q-6 kilograms per hour), 4.8 x 10"4 pounds
per day (2.2 x 1Q* kilograms per day), and 0.18 pounds per
year (0.08 kilograms per year).
The ARARs pertainingto the CAA can be determined only
on a site-by-site basis. Remedial activities involving the
UVB technology may be subject to the requirements of
Part C of the CAA for the prevention of significant
deterioration (PSD) of air quality in attainment (or
unclassified) areas. The PSD requirements will be
applicable when the remedial activities involve a major
source or modification as defined in 40 CFR Part §52.21.
The PSD significant emission rate for VOCs is 40 tons per
year (36,288 kilograms per year). Activities subject to
PSD review must ensure application of best available
control technologies (BACT) and demonstrate that the
activity will not adversely impact ambient air quality.
2.2.6 Occupational Safety and Health
Administration Requirements
CERCLA remedial actions and RCRA corrective actions
must be carried out in accordance with OSHA
requirements detailed in 20 CFR Parts 1900 through 1926,
especially Part 1910.120, which provides for the health
and safely of workers at hazardous waste sites. On-site
construction activities at Superfund or RCRA corrective
actions sites must be performed in accordance with Part
1926 of RCRA, which provides safety and health
regulations for constructions sites. State OSHA
requirements, which may be significantly stricter than
federal standards, must also be met.
All technicians operating the UVB treatment system are
required to have completed an OSHA training course and
must be familiar with all OSHA requirements relevant to
hazardous waste sites. For most sites, minimum personal
protective equipment (PPE) for technicians will include
gloves, hard hats, steel toe boots, and coveralls.
Depending on contaminant types and concentrations,
additional PPE may be required. Noise levels should be
monitored to ensure that workers are not exposed to noise
levels above a time-weighted average of 85 decibels over
an 8-hour day.
2.2.7 Technology Performance Versus
ARARs During the Demonstration
Several ARARs discussed in Table 2-1 did not apply to the
UVB treatment technology during the demonstration at
March AFB. ARARs relevant to wastewater injection
were not applicable during the demonstration because the
technology was not defined as underground injection by
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the regulatory oversight agencies. This interpretation was
based on site-specific conditions including the presence of
a groundwater extraction system about one-half mile
downgradient of the UVB system. If the technology is
interpreted as a wastewater injection system by the
regulatory agency, more stringent construction, operating,
and monitoring requirements may be imposed.
Site investigation and remediation activities at March
AFB are being performed by the base under CERCLA.
Since treatment of groundwater using the UVB system
took place on site, administrative requirements for the
technology demonstration, such as permitting were not
required. For the demonstration, groundwater was
characterized as a RCRA hazardous waste because it
resulted from the disposal of spent solvent (TCE and
DCE). RCRA requirements outlined in Table 2-1 for the
characterization, storage, transport, and disposal of wastes
generated by the system were followed.
The chemical-specific ARAR for cleanup of TCE in
groundwater (5 iig/L) was generally met. The UVB
system reduced TCE in the groundwater discharged from
the treatment system to below 5 |ig/L in nine but of the 10
monthly sampling events and on average by greater than
94 percent hi events where the system operated without
maintenance problems. The mean concentration of TCE
in water discharged from the system was approximately 3
jj,g/L with a 95 percent upper confidence limit
concentration of approximately 6 |ig/L. Based on the
system's removal efficiency documented during the
demonstration, influent concentrations greater than 83 ug/
L will require more than one treatment cycle through the
system to meet the chemical-specific ARAR for TCE (5
ug/L).
2.3 Operability of the Technology
Where applicable, the UVB technology provides an
effective long-term solution to aquifer remediation by
removing contaminants from the saturated zone. In
general, the UVB technology is applicable for the
treatment of dissolved phase volatile compounds in
groundwater. In addition, the system dynamics
established by the recirculation of treated water make this
technology suited for remediation of contaminant source
areas. The technology employs readily available
equipment and materials and once the UVB treatment
system is installed and balanced, it requires minimal
support from on-site personnel.
Several operating parameters influence the performance
of the UVB treatment system. Its performance is most
affected by its ability to strip volatile contaminants from
groundwater, which depends on the solubility, molecular
weight, and vapor pressure of the compounds treated and
the nature of the air-water interface through which the
compounds must pass. The UVB system effects the
volatilization of VOCs by optimizing the air-water
interface through the use of air-lift pumping and a
stripping reactor. These processes increase the
volatilization of dissolved contaminants to the vapor
phase by increasing the contact time for mass exchange
between the dissolved and vapor phases and by
minimizing coalescence of air bubbles. In order to achieve
the most efficient operation of the treatment system,
several factors must be balanced. The vacuum in the upper
portion of the system well and the supplemental pump
must be balanced to a flow rate compatible with the
hydraulic conductivity of the aquifer. In addition, the
diffuser plate and stripping reactor must b& positioned to
provide the maximum stripping zone without overcoming
the vacuum induced in the upper well. Routine
maintenance checks must be performed to ensure the
proper position and balance are sustained for the system to
operate at maximum efficiency.
Over the year-long demonstration of the UVB system, four
scheduled maintenance events were performed on the
system. Maintenance generally consisted of removing the
internal well components for inspection. Additionally, the
system was balanced such mat the stripping reactor
operated at optimal depth in relation to the vacuum
induced in the upper portion of the well. The leveling
ballasts are designed so the internal components
automatically adjust to fluctuations in the groundwater
levels (and thus the induced vacuum). However, one of the
buoyancy tanks was found to be leaking, which is
suspected to have caused the system to be periodically out
of balance during a 4-month interval. Except for the
leaking ballast, the system proved to be relatively stable
and required a minimum of attention over the course of the
demonstration. In instances where the system was out of
balance or required maintenance, it would be desirable to
incorporate some means of on-line monitoring to assure
that inefficient or out of compliance effluent conditions do
not persist. If such means of monitoring are not available,
it would be prudent to check the system at regular
intervals.
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2.4 Applicable Wastes
The UVB technology, demonstrated at March AFB,
California, was designed to remove dissolved phase VOCs
from the groundwater, in particular TCE and DCE. The
developer claims that the technology can also clean up
aquifers contaminated with other VOCs and semivolatile
organic compounds (SVOC). Additionally, the developer
claims that the in situ stripping of volatile contaminants
may be combined with added nutrients and electron
acceptors for in situ biodegradation.
According to the developer, the UVB technology may, in
some cases, be capable of simultaneous recovery of soil
gas from the vadose zone and treatment of contaminated
groundwater from the aquifer as a result of the in situ
vacuum. For soil gas recovery, the upper screened portion
of the UVB well is completed from below the water table
to above the capillary zone. Although the developer
claims that the UVB technology reduces VOCs from soil
gas in the vadose zone, the technology was evaluated only
for its effects in the saturated zone.
2.5 Key Features of the UVB
Treatment Technology
The UVB technology is an hi situ groundwater
remediation technology for the cleanup of aquifers
contaminated with VOCs, which is an alternative method
to pump-and-treat remediation of groundwater. The UVB
technology is designed to remove VOCs from
groundwater by transferring the contaminants from the
aqueous phase to the gaseous phase and subsequently
treating the resulting air stream through carbon adsorption
units. Key features of the UVB treatment system include;
a dual screen well, packer, submersible pump, air diffuser
plate, stripping reactor, blower, and carbon adsorption
units. Several unique features of the UVB system
distinguish it from most air stripping or pump and treat
technologies. According to the developer, air stripping in
a UVB system occurs in situ, eliminating the need for
conditioning the exhaust air due to high humidity.
Additionally, since air stripping occurs under a vacuum,
the amount of airrequired for the stripping process is much
less than for traditional techniques.
The unique dual screen construction of a UVB well in
conjunction with in situ air stripping allows the immediate
reinfiltration of groundwater once it has passed the
stripping reactor. As a result, remediation of the aquifer
occurs without extraction of groundwater, lowering of the
groundwater table, or generating wastewater typical of
pump and treat. Also, groundwater in a UVB well can be
pumped in part by air lift, which facilitates the partitioning
of contaminants in solution to the gas phase.
The recirculation of treated water within the system's
radius of circulation cell also distinguishes the system
from other conventional pump and treat systems. The
continuous flushing of the saturated zone with recirculated
treated water facilitates the partitioning of adsorbed,
absorbed, and liquid contaminants to the dissolved phase
through increased dissolution, diffusion, and desorption.
Increased partitioning through these processes is driven by
increased groundwater flow rates within the system's
radius of circulation cell and increased concentration
gradient established by the reinjection and recirculation of
treated water in the aquifer. This process provides an
effective long-term solution to aquifer remediation by
removing contaminants from multi loci in the saturated
zone.
2.6 Availability and Transportability of
Equipment
The UVB technology employs conventional, commercially
available equipment and materials that are easily
transported on flat-bed trailers. Once the installation of
the well is complete, the treatment system can be in
operation within a day if all necessary facilities, utilities,
and supplies are available. On-site assembly and
maintenance requirements are minimal. Demobilization
includes decontaminating on-site equipment, disconnecting
utilities, disassembling equipment, transporting equipment
off site, and plugging and abandoning of the UVB system
well. The system well is plugged and abandoned by
overdrilling the well and pressure grouting the well bore to
the surface. Plugging and abandonment of the monitoring
wells is considered a separate activity since wells may be
left in place for long-term monitoring.
2.7 Materials Handling Requirements
The materials handling requirements for the UVB system
include managing drilling wastes, purge water, and
decontamination wastes. The drilling wastes are produced
during installation of the system well. The UVB system
requires a 24-inch (61.0 cm) diameter bore, which
produces about 3.14 cubic feet (ft3) (0.1 m3) of drilling
waste per foot of bore. At the March AFB demonstration,
22
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the 24-inch (61.0 cm) bore was extended approximately 80
feet (24.4 m) and produced more than 251 ft3 (7.1 m3) of
drilling waste. The drilling waste can be managed either in
55-gallon (208.2 L) drums or in roll-off type debris boxes.
Disposal options for this waste depend on local
requirements and on the presence or absence of
contaminants. The options may range from on-site
disposal to disposal in a hazardous waste or commercial
waste landfill. Based on ffiG's experience, installation of
the UVB system does not require development of the
system well; therefore, development water is not
produced.
This analysis assumes that the monitoring wells are
already installed; however, management of this drilling
waste would be similar. Purge water is generated during
development and sampling of the groundwater monitoring
wells. Well purging usually continues until general water
quality parameters stabilize. Typically, this requires
removal of three to five well volumes from each
monitoring well. Purge water can be managed in 55-
gallon (208.2 L) drums. Disposal options again depend on
local restrictions and on the presence or absence of
contaminants. Options range from surface discharge
through an NPDES outfall, to disposal through a POTW,
to treatment and disposal at a permitted hazardous waste
facility.
Decontamination wastes are generated during installation
and sampling activities. Wastes generated during
installation include decontamination water and may
include residue and components of a decontamination pad
for the drill rig. Decontamination pads typically consist of
plywood and plastic sheeting; however, a gravel base may
be needed. The amount of water needed to decontaminate
a drill rig typically ranges from 100 to 300 gallons (378.5
to 1,135.5 L). Decontamination fluid is also generated
during sampling activities from cleaning of the sampling
equipment. The sampling decontamination fluid may
consist of water and an organic solvent such as hexane or
isopropanol. The amount of fluid needed at each well for
each sampling event may require 5 gallons (18.9 L) of
water and 100 to 200 milliliters of solvent. The solid
decontamination wastes can be managed in a roll-off type
debris boxes, and the liquid wastes can be managed in 55-
gallon (208.2 L) drums. Disposal options are similar to
those for drilling wastes and purge water.
2.8 Site Support Requirements
The site support requirements needed for the UVB system
are space to set up the carbon adsorption units and
electricity. The system requires standard 120/240 volts
(200 amperes). An electrical pole, a 480-volt transformer,
an electrical hookup between the supply lines, a pole, and
the UVB treatment system are necessary to supply power.
The space requirements for the above-ground components
of the UVB system including the UVB system well,
carbon adsorption units, blower, and piping used during
the SITE demonstration are approximately 500 square feet
(46.5 m2). A concrete pad was provided for the unit, but is
not absolutely necessary. A security fence was also
provided for the unit during the SITE demonstration, but is
recommended only if site security is not already provided.
Other requirements for installation and routine monitoring
of the system include decontamination fluids for drilling
and sampling. These fluids can be transported to the site in
portable tanks and containers.
2.9 Limitations of the Technology
The limitations of the UVB technology are that it requires
a minimum depth to groundwater of 5 feet and a minimum
aquifer thickness of 10 feet. In such areas, it may be
difficult to establish a stripping zone of adequate size to
remove contaminants from the aqueous phase. The
technology has further limitations in very thin aquifers;
the saturated zone must be of sufficient thickness to
provide space for the upper and lower portions of the
system. In addition, the thickness of the saturated zone
affects the radius of circulation cell; the smaller the aquifer
thicknesses, the smaller the radius of circulation cell.
The majority of water being drawn from the aquifer into
the lower screen section is treated water reinfiltrated from
the upper section. This recirculation of cleaned water
significantly decreases the contaminant levels in the water
treated by the system. As the UVB system continues to
operate, the circulation cell moves outward, which further
decreases the contaminant levels in the water treated by
the system. Although the recirculation of water facilitates
the long-term remediation of contaminants in the aquifer,
excessive recirculation will cause a significant decrease of
influent concentrations and increase the time required to
remediate the aquifer.
23
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High concentrations of volatile compounds may require
more than one pass through the system to achieve
remediation goals. This may initially be a problem since a
portion of the treated water is not captured by the system
and leaves the circulation cell in the downgradient
direction. However, as the UVB circulation cell is
established, the influent concentrations should be diluted
to below levels requiring more than one pass, thereby
limiting the potential migration of contaminants above
target concentrations from the system.
SITE did not evaluate the applicability of this technology
for inorganic and semivolatile compounds.
24
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Section 3
Economic Analysis
This section presents cost estimates for using the UVB
technology to treat groundwater. Cost estimates presented
in this section are based primarily on data compiled during
the SITE demonstration and additional costs provided by
Weston. Costs have been assigned to one of 12 categories
applicable to typical cleanup activities at Superfund and
RCRA sites (Evans 1990). This section provides a
discussion of each category including the general and
specific impacts on the overall cost and the assumptions
used in calculating the cost estimate. Costs are presented
in October 1994 dollars and are considered to be order-of-
magnitude estimates, with an accuracy of plus 50 percent
and minus 30 percent.
3.1 Basis of Economic Analysis
This section describes the factors that affect the costs
associated with the UVB treatment system and establishes
the assumptions used hi this economic analysis. A number
of factors affect the estimated costs of treating
groundwater with the UVB treatment system. The factors
affecting capital equipment costs are related to both site
conditions and system design and are generally fixed.
Annual operations and maintenance (O&M) costs are
highly variable due to the tune-dependent nature of UVB
operation. Typical contaminated groundwater sites may
require 1 to 10 years of system operation to be remediated
by the UVB treatment system operation. The time
required for remediation is dependent on several factors
discussed in detail in Section 3.1.1. Due to the variable
nature of the time required to remediate a site, annual
O&M costs have been presented for operating the UVB
treatment system for 1, 3, 5, and 10 years. These costs
represent average quotes from vendors providing the
necessary services.
3.1.1 Operation, Maintenance, and
Monitoring Factors
The costs associated with using the UVB technology are
influenced by operation, maintenance, and monitoring
factors. The maintenance and monitoring costs depend in
part on the duration of operation of the system because
increased time for remediation requires more maintenance
and more monitoring. The duration of operation for the
remediation of a site using the UVB treatment system
depends on a number of factors including: (1) the mass
and physical characteristics of contaminants present, (2)
efficiency of the UVB treatment system in removing
specific contaminants, and (3) the aquifer hydraulic
conductivity. As discussed in Section 1.3, the aquifer
hydraulic conductivity affects the aerial extent of
contamination that can be treated by defining the radius of
circulation cell of the UVB system. Similarly, the
hydraulic conductivity affects the amount of treated water
that is recycled through the system (recirculated water),
which determines the quantity of untreated water pulled
into the circulation cell.
The mass and characteristics of contaminants in the
aquifer to be remediated affect the operation time by
influencing the exchange of contaminants from the
dissolved to vapor phase. Groundwater with high
concentrations of contaminants and contaminants in
phases other than the dissolved phase may require multiple
passes of recirculated water through the treatment system
to meet the target concentrations. The increased tune
needed for multiple passes through the treatment system
will increase the total cost of the operation, maintenance,
and monitoring factors.
25
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The treatment efficiency of each UVB treatment well
system is dependent on adjustments to design factors (such
as screen lengths and vacuum pressure gradient). Systems
that are not properly adjusted will not achieve maximum
efficiency in removing contaminants. Low removal
efficiencies will also require multiple passes of
recirculated water through the treatment system to meet
target concentrations. Again, the increased tune needed
for multiple passes through the treatment system will
increase the total cost of the operation, maintenance, and
monitoring factors.
The aquifer conductivity affects the operation time by
controlling (1) the radius of circulation cell of the
treatment system, (2) the volume of water that can be
pumped through the treatment system per unit time, and
(3) the amount of recirculated water passing through the
system. The radius of circulation cell is directly
proportional to the ratio of the horizontal to vertical
conductivity of the aquifer. Anisotropic conditions within
the aquifer will result in differences in hydraulic
conductivity and groundwater flow within the aquifer.
High ratios of K^/K.^ indicate a large radius of circulation
cell, and low ratios of Kj/K^ indicate a small radius of
circulation cell. Aquifers with low horizontal hydraulic
conductivity may require the UVB treatment system to
operate at a reduced rate. Furthermore, low K,/Kv ratios
indicate a high degree of recirculation through the system
and a small amount of untreated water entering the system.
High Kj/Ky ratios indicate a low degree of recirculation
through the system and a large amount of untreated water
entering the system. The developer reports typical
recirculation amounts of 60 to 90 percent. Small radii of
influence may require multiple treatment units to be
installed if the aerial extent of contamination exceeds the
radius of circulation cell, and small treatment volumes or
high degrees of recirculation may increase the operation
time required to remediate an aquifer. Extra treatment
units and extended treatment time will increase the total
cost of the operation, maintenance, and monitoring
factors.
Routine maintenance of the UVB system is recommended
at least four times per year (once per quarter). System
maintenance may be increased during the initial startup
phase of operation to ensure the system is working
properly. After the initial startup period, however, there
are no daily requirements for operation and maintenance.
Requirements for monitoring the system's performance
and contaminant concentrations will vary between sites.
Most sites will require monitoring of the treated and
untreated groundwater, the system's effluent air stream,
and the groundwater in surrounding monitoring wells.
Section 3.3 provides additional information regarding
operation, maintenance, and monitoring factors.
This economic analysis assumes the aquifer conditions,
system well design, system maintenance schedule, and
monitoring frequency used during the SITE demonstration.
The conditions observed and assumptions made during the
SITE demonstration and for this economic analysis are
discussed in the following section.
3.1.2 Site Conditions and System
Design Factors
The number of UVB treatment systems employed at the
site will affect the duration and costs of a groundwater
remediation project. The need to use more than one
treatment system is determined based on the site
conditions. This analysis assumes that only one UVB
treatment system will be operated.
The UVB treatment system can treat groundwater
containing VOCs. This analysis assumes that the UVB
technology will treat groundwater contaminated with
TCE.
System design costs typical for Superfund sites include
site preparation (such as removal of debris), construction
activities (such as access roads), and installation of
monitoring wells. These costs are not included in this
analysis because they are assumed to have been incurred
while characterizing the extent of groundwater
contamination. Added costs will be incurred if additional
preparation, construction, or monitoring well installation
activities are necessary.
Assumptions for site conditions and system design include
the following:
* The site is a Superfund site
• The aquifer has been characterized during previous
investigations
* Suitable site access roads exist
• Utility supply lines, such as electricity and telephone
lines, exist on site
26
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• A single UVB treatment system will be used for
treatment
• The treatment system operates automatically
• Contaminated groundwater is located in a shallow
aquifer no more than 40 feet (12.2 m) below ground
surface
• The saturated zone has a depth of approximately
40 feet (12.2m)
• The flowrate through the UVB system is 20 gpm (75.7
liters per minute)
• The unit operates 95 percent of the time with only 5
percent downtime for maintenance and repairs
• One technician will be required to collect all required
samples and perform minor equipment repairs at the
same frequency used for monitoring
• One treated and one untreated groundwater sample
will be collected from the UVB well once a month to
monitor system performance for the first year and
quarterly thereafter
• Three groundwater samples will be collected from
surrounding wells once a month for the first year and
quarterly thereafter to monitor the system's effect on
the aquifer
• Labor costs associated with major repairs are not
included
• Because of the nature of the UVB technology, no site
cleanup or restoration activities will be required
during demobilization except for well plugging and
dismantling the carbon adsorption unit.
3.2 Costs Included in the Price of
Purchasing the UVB Treatment
System
According to IEG, several costs usually associated with
groundwater remediation projects are included in the price
of purchasing the UVB treatment system. Construction
costs for installing the UVB treatment system are incurred
only with the installation of a 16-inch (40.6 cm) system
well and then installing the downhole components of the
UVB treatment system. The construction costs are
discussed in Section 3.3.1, Site Preparation Costs, and the
UVB system purchase costs are discussed in Section 3.3.3,
Capital Equipment Costs. System design costs include
designing the treatment system to determine optimal
airflow. These costs are included in the cost of purchasing
the UVB treatment system.
Mobilization involves transporting all equipment to the
site and assembling it. IEG includes mobilization in the
cost of purchasing the UVB treatment system.
Mobilization of the equipment necessary for installing a
16-inch (40.6 cm) system well is assumed to be included in
the cost of constructing the well. Any additional support
equipment needed at the remediation site is assumed to be
supplied by the customer or by independent vendors. The
cost for this additional support equipment is included with
site preparation costs.
3.3 Cost Categories
Cost data associated with the UVB technology have been
assigned to the following 12 categories: (l)site
preparation; (2) permitting and regulatory requirements;
(3) capital equipment; (4) startup; (5) labor; (6)
consumables and supplies; (7) utilities; (8) effluent
treatment and disposal; (9) residuals and waste shipping
and handling; (10) analytical services; (11) maintenance
and modifications; and (12) demobilization (Evans 1990).
Costs associated with each of these categories are
discussed below.
3.3.1 Site Preparation Costs
Site preparation costs include administrative costs,
electrical hookup, and 16-inch (40.6 cm) system well
installation. For this analysis, administrative costs, such
as developing a work plan and other site planning
activities, are estimated to be $10,000.
This analysis assumes that electric lines exist at the site.
One pole, one 480-volt transformer, and an electrical
hookup between the lines, pole, and the UVB treatment
system are necessary. Based on costs incurred at the SITE
demonstration, electrical hookup costs are estimated to be
about $5,000.
According to Weston, the cost incurred at the SITE
demonstration for installing an 80-foot (24.4 m), 16-inch
(40.6 cm) system well was about $450 per foot ($ 1,475 per
27
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meter). This analysis also assumes an 80-foot (24.4 m),
16-inch (40.6 cm) system well (24-inch [61.0 cm] bore)
will be installed for a total cost of $36,000. The total
drilling cost does not include disposal of the drill cuttings
(see Section 3.3.9)
Total site preparation costs are estimated to be $51,000.
Mobilization costs are typically incurred as a site
preparation cost. Mobilization involves transporting all
equipment to the site and assembling it. IEG includes such
costs in the price of purchasing the UVB treatment system.
Mobilization of system well installation equipment
described above is assumed to be included in the cost of
constructing the well. Any additional support equipment
needed at the remediation site is assumed to be supplied by
the customer or by independent vendors. These costs are
included with the above drilling costs.
3.3.2 Permitting and Regulatory
Requirements Costs
Permitting and regulatory costs will vary, depending on
whether treatment occurs at a Superfund or a RCRA
corrective action site, on state and local requirements, and
on how treated effluent and any solid wastes generated
(such drill cuttings and spent activated carbon) are
disposed. Superfund sites require remedial actions to be
consistent with ARARs including federal, state, and local
standards and criteria. In general, ARARs must be
determined on a site-specific basis. RCRA corrective
action sites will require additional permitting, monitoring,
and records.
Permitting and regulatory costs are assumed to be about 5
percent of the total capital equipment costs for a treatment
operation that is part of a Superfund remedial action
(Evans 1990). For this analysis, permitting and regulatory
costs are estimated to be $5,400. Costs at a RCRA
corrective action site are estimated to be an additional 5
percent higher. The permitting and regulatory costs
include preparation of required regulatory documents.
3.3.3 Capital Equipment Costs
Capital equipment costs include the UVB treatment
system and an off-gas air treatment system. The UVB
treatment system includes: a vacuum pump, piping, a
downhole submersible pump, air diffuser plate, stripping
reactor, buoyancy tanks, 16-inch (40.6 cm) double-cased
stainless steel screens and casing, well pack materials, and
a wellhead seal. According to Weston, the capital
equipment costs of the UVB treatment system will be
about $100,000.
Construction costs for installing the UVB treatment
system are incurred only with the installation of a 16-inch
(40.6 cm) system well and then installing the downhole
components of the UVB treatment system. The well
installation costs are discussed in Section 3.3.1, Site
Preparation Costs, and costs for installation of the
downhole components are included previously with the
price of purchasing the UVB treatment system.
The off-gas air treatment system includes two activated
carbon units, ancillary piping connecting the carbon units
to the UVB blower, and carbon. According to EEG, the
cost for this equipment will be about $8,100. Monthly
carbon adsorption unit rental costs are discussed in Section
3.3.6, Consumables and Supplies Costs. The costs of
disposing of or recharging the carbon are discussed in
Section 3.3.8, Effluent Treatment and Disposal Costs.
Total capital equipment costs will be about $110,000,
which includes carbon adsorption units and the UVB
system.
3.3.4 Startup Costs
Startup costs are incurred during all activities to operate
the UVB treatment system and include operator training,
optimization, and shakedown costs. Optimization and
shakedown activities include initial startup, trial runs,
final equipment inspection, and the associated labor for
conducting these activities. These costs are included in the
price of purchasing the UVB treatment system (Section
3.3.3, Capital Equipment Costs) and are not presented as a
separate cost item in this analysis.
Operator training costs are assumed to include providing a
40-hour health and safety training course and developing a
health and safety program for the Superfund site. This
analysis assumes that one operator must be trained. These
startup training costs are estimated to be about $10,000.
3.3.5 Labor Costs
Labor costs include the total staff needed for operation and
maintenance of the UVB treatment system and an annual
health and safety refresher course with medical
monitoring. An annual health and safety refresher course
28
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will cost about $2,000 per person. The labor wage rates
provided in this analysis include overhead and fringe
benefits.
These costs assume that one technician collects monthly
samples and inspects the off-gas treatment system. The
technician will collect samples of untreated and treated
groundwater and three groundwater samples from
surrounding monitoring wells for a total of five
groundwater samples. The samples will be collected
monthly for the first year and quarterly thereafter. This
analysis assumes a relatively fast recharging rate in the
monitoring wells and minimal purge volumes
(approximately 50 gallons [189.3 L] per well). This
analysis also assumes that sampling activities will be
conducted in Level D PPE. Sampling activities are
estimated to require about 12 hours per sampling event.
The fully loaded hourly labor rate for the technician is
estimated to be about $31.50 for a total annual cost of
about $4,500.
Total annual labor costs for the first year are estimated to
be $6,500 for operation inspections and health and safety
requirements. For each additional year thereafter, total
annual labor costs are estimated to be $3,500 for operation
inspections and health and safety requirements.
3.3.6 Consumables and Supplies Costs
Consumables and supply costs only include renting
activated carbon units. Costs for PPE are included with the
labor costs (Section 3.3.5) presented above, and the costs
for sampling equipment are assumed to be incurred during
site characterization studies. The monthly rental costs for
activated carbon units will be about $570 per unit. The off-
gas treatment units used for this demonstration were two
1,800-pound (816.5 kilograms [kg]) vapor phase activated
carbon units. This analysis assumes two activated carbon
units will be used per year for a total annual cost of about
$14,000.
3.3.7 Utilities Costs
Total utility costs are based on the power used to operate
the entire UVB treatment system. This includes pumps
and the vacuum pump. Electrical usage at the SITE
demonstration was 3.67 kilowatts per hour of operation.
This analysis assumes the treatment system will operate
24 hours per day 95 percent of the time. At this rate, total
annual electrical usage will be about 30,542 kilowatts.
This analysis assumes that electricity costs about $0.07 per
kilowatt-hour, inclusive of usage and demand charges.
Total annual electricity costs are estimated to be about
$2,000.
Electrical costs can vary by as much as 50 percent
depending on the geographical location and local utility
rates. This analysis assumes that no alternative sources of
electrical power, such as a diesel-powered generator, will
be used as backup.
3.3.8 Effluent Treatment and Disposal
Costs
The UVB treatment system off gas is treated by two
granulated activated carbon units. The costs of purchasing
the initial fill of carbon are discussed in Section 3.3.3,
Capital Equipment Costs, and the costs of renting this
equipment are covered in Section 3.3.6, Consumables and
Supplies Costs. The cost of replacing the carbon is
discussed in this section because of its close association
with treating the off gas effluent stream. No other effluent
or wastes are generated by the operation of the UVB
treatment system.
This analysis assumes the activated carbon units will be
replaced every 6 months. Based on vendor quotes, the cost
for reactivating carbon is about $500 for each unit. This
cost includes transportation, reactivation, and a change-
out unit. Total annual carbon replacements costs will be
about $2,000.
3.3.9 Residuals and Waste Shipping and
Handling Costs
No residuals or wastes are generated from the operation of
the UVB treatment system. Drill cuttings, however, will
be generated during installation and removal of the system
well, and purge water will be generated from periodic
sampling activities. Disposal of wastes generated during
removal of the system well are addressed in Section
3.3.12, Demobilization Costs. Disposal of drilling wastes
(cuttings) from installation activities are assumed to occur
in the first year after installation. This cost estimate
assumes that the cuttings are not characteristically
hazardous but that the cuttings are disposed of at a licensed
hazardous waste disposal facility. The cost for disposal of
the cuttings is estimated to be $2,600 and includes
transportation, treatment, and disposal as a bulk solid in a
landfill.
29
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For the purge water, this analysis assumes contaminant
concentration will be below RCRA regulatory levels that
require storage and treatment as a hazardous waste. This
purge water will be collected in 55-gallon (208.2 L)
carbon-steel drums and disposed of at an off-site industrial
wastewater treatment and disposal facility. This analysis
assumes that about 150 gallons (567.8 L) of purge water
will be generated during each sampling event and stored
on site until a total of 600 gallons (2,271.0 L) are
accumulated, requiring 12 55-gallon (208.2 L) carbon
steel drums. Each drum costs about $30, for a total one-
time cost of $360. .After accumulating 600 gallons
(2,271.0 L) of purge water, a licensed waste hauler will
transfer the wastes from the drums into a tanker truck.
This analysis assumes that the purge water will be
transported about 100 miles (161 kilometers [km]) to the
nearest industrial wastewater treatment facility.
Transportation costs (including pumping and labor costs)
are estimated to be $700 per trip, and disposal costs are
estimated to be $0.25 per gallon ($0.07 per L).
Total annual residuals and waste shipping costs in the first
year of operation are estimated to be $6,200. Total annual
costs for the subsequent years are estimated to be $850.
3.3.10 Analytical Services Costs
Analytical costs include laboratory analyses, data
reduction and tabulation, quality assurance/quality control
(QA/QC), and reporting. This analysis assumes the
following samples will be collected each month of the first
year to be analyzed for VOCs by EPA SW-846 Method
8260: one sample of untreated groundwater, one sample
of treated groundwater, three samples from outlying
groundwater monitoring wells, and QA/QC samples
consisting of a trip blank, a field and equipment blank, a
field duplicate, and matrix spike and matrix spike
duplicate (MS/MSD) samples. Monthly laboratory
analysis will cost about $2,300; data reduction, tabulation,
data validation, and reporting is estimated to cost about
$750 per month. Total annual analytical services costs in
the first year are estimated to be about $36,000.
For each successive year after the first year, samples will
be collected quarterly. One untreated groundwater
sample, one treated groundwater sample, three outlying
groundwater monitoring well samples, and QA/QC
samples consisting of a trip blank, a field and equipment
blank, a field duplicate, and MS/MSD samples will be
collected during each quarterly sampling event. Assuming
the same costs outlined above, the total annual analytical
services costs will be about $ 12,000 for each year after the
first year.
3.3.11 Maintenance and Modifications
Costs
IEG provides maintenance for a cost of $2,000 per quarter.
This analysis assumes the site owner or operator will
procure the IEG maintenance agreement. Total annual
maintenance and modification costs are estimated to be
$8,000.
3.3.72 Demobilization Costs
Site demobilization includes shutdown, disassembly, well
plugging and abandonment, and transportation and
disposal of equipment to a licensed hazardous waste
disposal facility. Well plugging and abandonment
procedures consist of overdrilling the well and pressure
grouting the boring to the ground surface. Demobilization
will occur at the end of the groundwater remediation
project and is estimated to take about 5 days to complete.
This analysis assumes the UVB technology will have no
salvage value at the end of the project. The majority of
demobilization costs apply to waste disposal, which is
estimated to be about $4,400. This estimate assumes that
the waste is not characteristically hazardous. The wastes
requiring disposal include the casing and filter pack from
overdrilling, the UVB system itself, and ancillary piping
and equipment associated with the carbon adsorption
units. The total volume of waste is assumed to be 20 cubic
yards (15.3 m3). The cost for waste disposal includes
transportation and labor. Labor costs associated with all
activities other than well plugging and abandonment
during demobilization will include two technicians
working five 8-hour days and are estimated to be about
$2,500; labor costs associated with well plugging and
abandonment are accounted for in the waste disposal cost.
Total demobilization costs are estimated to be about
$6,900 in current 1994 dollars. Because groundwater
remediation projects can take many years to complete,
demobilization costs will have to be adjusted to future
dollars, once the term of the project can be estimated, to
determine actual demobilization costs.
3.4 Estimated Cost of the UVB System
This section presents the estimated costs in October 1994
dollars for using the UVB system under the conditions
30
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described in the previous sections. Table 3-1 presents a
breakdown of costs for the 12 categories previously
identified. The table presents fixed costs and annual
variable costs, and compares the costs for groundwater
treatment projects lasting 1,3,5, and 10 years. The cost of
treatment per 1,000 gallons (3,785 L) refers to the amount
of groundwater pumped through the system (not to the
volume of contaminated water hi the aquifer). Potential
users of the treatment technology should be aware that
typically 60 to 90 percent of the water pumped through the
system is recirculated water. The cost estimate for each
category was rounded to two significant figures. The total
costs were also rounded to two significant figures. One-
time capital costs for a single treatment unit were
estimated to be $180,000; variable annual operation and
maintenance costs were estimated to be $75,000. Based
on these estimates, the total cost for operating a single
UVB system for 1 year was calculated to be $260,000.
Since the time required to remediate an aquifer is site-
specific, costs have been estimated for operation of a UVB
system over a range of time for comparison purposes.
Therefore, the cost to operate a single UVB system was
calculated to be $340,000 for 3 years, $440,000 for 5 years,
and $710,000 for 10 years. Additionally, the costs for
treatment per 1,000 gallons (3,785 L) of groundwater were
estimated to be $260 for 1 year, $110 for 3 years, $88 for
5 years, and $71 for 10 years. (The costs for treatment per
1,000 L of groundwater were estimated to be $69 for 1
year, $29 for3 years, $23 for 5 years, and $19 for 10 years.)
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Table 3-1. Costs Associated with the UVB Technology
Cost Categories
Costs in 1994 $a
Site Preparation b
Permitting and Regulatory Requirements b
Capital Equipment b
Startup b
Labor °'d
Consumables and Supplies °
Utilities c
Effluent Treatment and Disposal °
Residual and Waste Shipping and Handling c>e
Analytical Services c>f
Maintenance and Modifications c
Demobilization b
Total One-Time Costs
Rrst Year Operation and Maintenance Costs
Subsequent Years Operation and Maintenance Base
Costs
Total Cost of Project Lasting 1 Year g
Total Cost of Project Lasting 3 Years 9
Total Cost of Project Lasting 5 Years 9
Total Cost of Project Lasting 10 Years 9
Costs per 1,000 Gallons (3,785 L) Treated (1 Year) h
Costs per 1,000 Gallons (3,785 L) Treated (3 Years) h
Costs per 1,000 Gallons (3,785 L) Treated (5 Years) h
Costs per 1,000 Gallons (3,785 L) Treated (10 Years) h
j
$51,000
5,400
110,000
10,000
6,500
1(3,500)
14,000
2,000
2,000
6,200
(850)
36,000
(12,000)
8,000
6,900
180,000
75,000
42,000
260,000
340,000
440,000
710,000
260
110
88
71
Notes: *
o
d
Costs have been rounded to two significant figures
One-time cost
Annual variable operation and maintenance cost
Figure presents annual cost of the first year of operation. Annual cost for successive
years is estimated to be $3,500.
Figure presents annual cost of the first year of operation. Annual cost for successive
years is estimated to be $850.
Figure presents annual cost of the first year of operation. Annual cost for successive
years is estimated to be $12,000.
Estimated annual inflation rate is 4 percent
Annually treats about 1,000,000 gallons (3,785,000 L) (assuming 5 percent downtime)
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Section 4
Treatment Effectiveness
This section documents the background, field and
analytical procedures, results, and conclusions used to
assesses the ability of the UVB technology to remove
VOCs from contaminated groundwater. This assessment
is based on the UVB SITE demonstration at March AFB
and on case studies supplied by the technology developer.
Because the results of the SITE demonstration are of
known quality, conclusions are drawn mainly from the
demonstration results.
4.1 Background
EPA conducted a SITE demonstration of the UVB system
at Site 31 on March AFB, which is located near Riverside,
California (Figure 4-1). The U.S. Air Force contracted
with Weston and IEG to demonstrate the UVB technology
atMarch AFB. The U.S. Army Corps of Engineers Omaha
District initiated installation of the technology through
Black & Veatch Waste Science. The Air Force invited the
SITE program to evaluate the demonstration project. The
environmental setting at March AFB and Site 31 are
described in Sections 4.1.1 and 4.1.2. An overview of the
demonstration objectives and approach is presented in
Section 4.1.3
4.1.1 March AFB
In April 1993, Site 31 at March AFB was selected for the
SITE demonstration of the UVB technology. March AFB
is located on approximately 7,000 acres (2,832.9 hectares)
in the northern end of the Ferris Valley, east of the city of
Riverside, in Riverside County, California. The base is
approximately 60 miles (96.5 km) east of Los Angeles and
90 miles (144.8 km) north of San Diego.
March AFB was officially commissioned on March 1,
1918 as a World War I aviation training facility and is one
of the oldest bases in the western United States. The base
has since steadily grown and has been home to West Coast
bombing and gunnery training, the Strategic Air
Command, and Ah" Mobility Command. In 1993, March
AFB was designated by Congress under the Base Closure
and Realignment Act to realign its forces from active duty
personnel to Air Force Reserve and National Guard Force
units. Realignment activities are scheduled to be
completed in 1996 and the base will be redesignated
"March Air Reserve Base" at that time.
March AFB has long been engaged in a wide variety of
operations that involve the use, storage, and disposal of
hazardous materials. Base operations such as aircraft
maintenance, fuel storage operations, and fire-training
exercises have generated a variety of hazardous wastes
which, combined with past waste disposal practices, have
resulted in contamination of soil and groundwater at
several areas on base.
In 1983, March AFB initiated Installation Restoration
Program (IRP) activities to locate, investigate, and
remediate hazardous waste sites. The IRP provides a
procedural framework for developing, implementing, and
monitoring response actions at March AFB in accordance
with pertinent federal regulations and applicable state
laws. To more effectively manage the IRP program, three
separate operable units were created based on geographic
location and similarity of the sites. The three operable
units consist of 42 sites that are undergoing comprehensive
site investigation and characterization activities. March
AFB has taken a leadership role in implementing and
expediting IRP activities and is one of the model IRP bases
for the U.S. Air Force. This role includes actively
assessing mechanisms for accelerating the remedial
investigation/feasibility study (RI/FS) process in an effort
to move more quickly to a record of decision, and to
implement the selected remedial actions.
33
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LOS ANGELES
* 60 MILES
MARCH
AIR FORCE BASE
MARCH AFB
California
SAN DIEGO
90 MILES
Figure 4-1. March AFB location map.
34
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March AFB has committed to the pilot-scale application of
various innovative remedial technologies to accelerate the
selection, design, and installation of full-scale alternative
remedial technologies and implementation of remedial
activities. Within this framework, the UVB technology
was selected as an interim remedial action to treat
contaminated groundwater at Site 31.
Site 31 is managed within Operable Unit 1 (OU1), which
consists of a total of 14 sites. Site 31 (an unconfirmed
solvent disposal area) is located off Graeber Street on the
east side of Building 1211 (Figure 4-2). The practice of
discharging solvents on the ground reportedly occurred
from about the mid-1950s to the mid-1970s at the site. In
addition, floor drains from maintenance shops may have
leaked solvents to the subsurface. Site investigative
activities confirm the presence of elevated levels of VOCs,
specifically TCE and DCE, in the groundwater and soil
gas.
4.1.2 Site 31
Characterization of the geology, hydrology, and
contaminants at Site 31 is based on the observations and
results from the UVB SITE demonstration, investigation
results from Site 31 documented in the report by The Earth
Technology Corporation (TETC), "Installation Restoration
Program, Draft Final Remedial Investigation/Feasibility
Study Report For Operable Unit 1, March Air Force Base,
California (TETC 1994), and data generated on the UVB
system by Weston and documented in its report, "Pilot
Study for Innovative Technology UVB-Vacuum
Vaporization Well, Site 31 March Air Force Base,
California" (Weston 1994). Based on the site
characterization data, the UVB system was installed
approximately 100 feet (30.5 m) south of Building 1211 in
an area containing high (>400 ng/L) concentrations of
TCE in the groundwater.
4.1.2.1 Geology
The geologic interpretation of Site 31 is based on field
observations while installing groundwater monitoring
wells during SITE demonstration activities and on
previous investigative results provided by March AFB. A
detailed description of the site and regional geology is
presented in the draft final RI/FS report for OU1 (TETC
1994).
March AFB lies within the northern portion of the
Peninsular Range geomorphic province, as defined by the
California Division of Mines and Geology. The base lies
between two major fault zones: the Elsinore-Chino fault
zone to the southwest and the San Jacinto fault zone to the
northeast. These northwest trending fault zones have been
active recently and can act as barriers to groundwater
movement (TETC 1994).
The region around March AFB is characterized by rugged
mountain ranges composed of igneous and metamorphic
rocks, broad erosional plains composed of deeply eroded
sedimentary and crystalline basement rocks, and a broad,
flat valley composed of younger alluvial material. The
main base lies in the Penis Valley where alluvium is found
at the surface (TETC 1994).
Sites 31 is located within the northern portion of Penis
Valley at an elevation of approximately 1,505 feet (458.7
m) above mean sea level. Penis Valley is an alluvial filled
valley that slopes gently at approximately 20 feet per mile
(3.8 meters/kilometers [m/km]) to the south-southeast
(TETC 1994). The alluvium consists of poorly
consolidated deposits of clay, silt, sand, and cobble-sized
particles derived from the surrounding crystalline
basement rock. Lithologic logs from the site suggest that
the alluvium overlies weathered granitic bedrock. The
contact between the alluvium and weathered bedrock is
undulating and varies in depth from 95 to 100 feet (29.0 to
30.5 m) below ground surface (bgs) in the northern and
eastern portions of the Site 31 to 150 to 165 feet (45.7 to
50.3 m) bgs in the southern and western portion of the site.
The thickness of the weathered bedrock at the site is highly
variable and is estimated to be approximately 50 feet (15.2
m) in the vicinity of the UVB system based on the results
of a seismic reflection survey conducted at Site 31 (Tetra
Tech 1993a).
The stratigraphy at Site 31 consists of alternating layers of
clay, silt, silty sand, and sand. Lithologic descriptions of
the individual borings advanced during demonstration
activities are shown on logs presented in the UVB
Technology Evaluation Report (TER) (PRC 1995). In
general, correlation of boring logs across the site is poor,
which is indicative of the nature of the underlying alluvial
deposits. The upper 40 feet (12.2 m) of the alluvial
deposits consisted predominantly of interbedded silt and
silty sand. From 40 to 50 feet (12.2 to 15.2 m) bgs, a
relatively clean (trace to little silt- and clay-sized particles)
sand was encountered. The sand interval appears to
35
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MORENO VALLEY
West March AFB
Hlvsaida National Canwtaiy
(V«t»rmn«AdmW«tratton)
Penis
Figure 4-2. Site 31 location map.
36
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correlate with adjacent borehole logs, which suggests that
it is laterally continuous in the vicinity of the UVB system.
This sand interval is underlain by silty sand extending
from approximately 50 to 65 feet (15.2 to 19.8 m) bgs
which hi turn overlies a second relatively clean sand layer
extending from approximately 65 to 75 feet (19.8 to 22.9
m) bgs. The second clean sand interval is interpreted to be
lenticular, pinching out to the north and south toward the
UVB well and outer cluster wells. The discontinuous
nature of the layer is also suggested by the poor correlation
with adjacent boring logs. The lithology below this
interval consists of interbedded silts and sands, and minor
clays. Prominent within this zone is a clay encountered at
120 feet (36.6 m) bgs, which has been interpreted to act as
a confining layer beneath the site (TETC 1994). A cross
section showing the generalized stratigraphy at the site
from the system well to the outer cluster wells is presented
on Figure 4-3.
Based on geological reconnaissance of the base and
surrounding area during IRP activities, two major sets of
near-vertical fractures were identified (Tetra Tech 1993b).
A primary and moderately subordinate fracture set
trending north-northwest and north-northeast were
interpreted and appear to be closely related to the fracture
systems that permeate the bedrock surrounding the base
(Tetra-Tech 1993b). The physical characteristics of the
fault and fracture traces, such as width of the specific
fracture traces, presence or absence of fault gouge, and
degree of filling of fracture channels have been roughly
approximated in the field. These measurements suggest
that the width of these zones may vary between 10 feet to
200 feet (3.0 to 61.0 m) and that near-surface fractures
may have openings of an eighth of an inch (3.2
millimeters) or more. In some instances, the fractures may
be filled with varying amounts of clay minerals or caliche
(Tetra Tech 1993b).
Based on a seismic reflection survey conducted at Site 31,
a northwest/southeast trending fault approximately
parallel to Graeber Street has been interpreted (Tetra Tech
1993 a). The seismic reflection data from Site 31 indicate
an offset of approximately 9 feet (2.7 m) in a prominent
clay layer at 115 feet (35.1) bgs and hi unweathered
bedrock at 170 feet (51.8m) bgs. A cross section showing
the interpreted seismic profile is presented on Figure 4-4.
The fault has been interpreted to have a surface projection
located immediately south of well 4MW14, approximately
40 feet (12.2 m) northeast of the UVB system. In addition,
recent unpublished geophysical investigative results from
March AFB support the presence of the interpreted fault
through the base (IT Corporation 1994). Preliminary data
from this investigation appear to correlate with the
geophysical investigation conducted at Site 31 (Tetra Tech
1993a). This correlation suggests that a well-developed
fracture zone parallel to Graeber Street (southeast
trending) may be present. If present, this fracture zone
could provide a preferential conduit for groundwater flow
at the site.
4.1.2.2 Hydrogeologic Conditions
Data collected during UVB SITE demonstration indicate
that hydrogeologic conditions at Site 31 exert a controlling
influence over the movement of groundwater and likely
the subsequent distribution of contaminants during the
demonstration. The primary hydrogeologic factors
affecting the demonstration results are groundwater flow
direction and anisotropy and heterogeneity of the aquifer.
Hydrogeology
Groundwater beneath Site 31 occurs in two distinct zones:
an upper unconfined water table zone and a lower
semiconfined zone (TETC 1994). Depth to groundwater
beneath Site 31 in the upper unconfined zone is
approximately 40 feet (12.2 m) bgs. A prominent sand
unit occurs at a depth between 40 to 50 feet (12.2 to 15.2m)
bgs. This unit ranges from 5 to 10 feet (1.5 to 3.0 m) thick
and appears to be a highly conductive water-bearing unit.
Borehole data suggest that a clayey sand and sandy clay
layer occurs at about 120 feet (36.6 m) bgs that acts as a
confining layer beneath Site 31. This clay layer appears to
be a barrier to the vertical flow of groundwater at Site 31.
Depth to water in the lower semiconfined zone is
approximately 45 feet (13.7 m) bgs. The lower
semiconfined zone consists of saturated alluvial deposits
and the underlying weathered bedrock. Comparison of
static groundwater levels in well screens in the upper
unconfined zone and lower semiconfined zone suggests
that the two zones are hydraulically separated.
Furthermore, a step-drawdown test and long-term
constant rate pump test conducted in the upper confined
zone showed no effects on the lower semiconfined zone
(TETC 1994).
Aquifer characteristics of the upper unconfined zone as
calculated from the pump tests indicate that: (1) average
site hydraulic conductivity is 90.5 gallons per day per foot
squared (gpd/ft2) (4.26 x 10~3 cm/s); (2) effective porosity
37
-------
PW1 PWJS
PW2
VI
PW4 PW6
PW5
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SW WELL GRADED SANDS
SP SP POORLY GRADED SANDS
15 -•
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SO--
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120- •
133-1-
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su
ML
SILTY SANDS
INORGANIC SILTS AND VERY FINE SANDS
GROUNDWATER PIEXOMETRIC SURFACE
INFERRED CONTACT
VERTICAL SCALE: 1"=15'
HORIZONTAL NOT TO SCALE
Figure 4-3. Generalized stratigraphic cross section.
38
-------
Hi S
oaswnaAvui awii AVM OMU.
2
ee
39
-------
is 27.2 percent; and, (3) transport velocity is 0.62 feet per
day(ft/day)(2.19x!0-4cm/s)(TETC 1994). Groundwater
gradient and direction calculated from the wells screened
in the upper unconfined zone suggest that groundwater
flows to the southeast at a gradient of approximately 0.014
(Figure 4-5). Results from a dye trace study conducted as
part of the SITE demonstration also suggest flow in the
south-southeast direction at a maximum velocity of 0.75 to
0.77 ft/day (2.65 x 10"4 to 2.72 x 10"4 cm/s) (Appendix A).
After the UVB was shut down, the natural gradient was
measured in January 1995 to be 0.07.
Groundwater Flow Direction
The downgradient direction of groundwater flow was
originally determined to be to the southeast based on a
preliminary contour map of the November 1992
groundwater elevations at Site 31 (TETC1994). Thisflow
direction corresponds to the general groundwater gradient
over the majority of the base, gently sloping to the
southeast. After heavy rains during the winter of 1992-93,
an apparent change in groundwater flow direction was
observed at the site (TETC 1994). This change was
interpreted to be in response to recharge along the
Heacock Storm Drain, located along the eastern boundary
of the base. Recharge from the storm drain appears to have
caused localized groundwater mounding, which in turn
locally affects the direction of groundwater flow. The
mounding of groundwater in response to the recharge
appears to have temporarily redirected the groundwater
flow toward the west-southwest along the eastern portion
of the base, which includes Site 31. However, wells west
of Site 31 did not appear to have been affected by
groundwater recharge from Heacock Storm Drain, and
data from these wells continue to indicate a groundwater
flow direction to the southeast.
Groundwater level elevations were collected before,
during, and after the UVB demonstration. Based on
contouring of the groundwater elevations, the
potentiometric surface appears relatively flat with
generally less than 1 foot (0.3 m) change of gradient across
Site 31. Due to the relatively flat gradient and the linear
distribution of groundwater monitoring wells at the site,
the localized groundwater flow direction could not be
precisely determined during the demonstration. However,
groundwater levels measured during operation of the UVB
system suggest that wells PW1 through PW6 are
downgradient (southeast) of the treatment system. After
startup of the UVB system, additional wells screened
across the groundwater table were installed in the
immediate vicinity of the treatment system. These
additional wells allowed the accurate measurement of the
groundwater gradient after the UVB system was shut
down on December 4, 1994. Figure 4-5 presents the
interpreted potentiometric surface map of the groundwater
elevation data collected from Site 31 wells on December 9,
1994. The map indicates that groundwater flow is toward
the southeast.
Modeling of groundwater flow at March AFB suggests
that the site is located on a groundwater trough (Tetra-
Tech 1994). The convergence of groundwater flow
directions in the trough appears to have caused a saddling
effect on the groundwater gradient. Several interpretations
for the change in gradient direction at the site have been
proposed, including shallow bedrock and structural
discontinuity (Terra Tech 1994). However, since
interpretation of boring log data from the site suggests that
bedrock is at least 110 to 120 feet (33.5 to 36.6 m) bgs, it
is unlikely that bedrock has significantly affected the
groundwater gradient at the site. In addition, the
semiconfining layer between the measured unconfined
water table elevation and the bedrock should effectively
mask the influence of the bedrock. Changes in gradient
could be caused by changes in the topographic elevation of
the semiconfming or changes in permeability of the
semiconfining bed.
Anisotropy and Heterogeneity
In addition to the natural groundwater gradient direction,
the anisotropy and heterogeneity of the aquifer play a
significant role in controlling the movement of
groundwater and subsequent distribution of contaminants.
These factors are magnified especially when an induced
flow, such as the UVB circulation cell, is placed on the
aquifer. Induced groundwater flow resulting from
operation of the UVB system will be influenced by the
anisotropy and heterogeneity of the aquifer and locally
may not flow in the undisturbed downgradient
groundwater flow direction.
Since the aquifer consists of alluvial deposits, anisotropic
conditions are likely present. The vertical hydraulic
conductivity at the site is assumed to be an order of
magnitude less than horizontal hydraulic conductivity. In
addition to anisotropic conditions in the alluvial deposits,
structural controls, such as fractures and faults, may
significantly affect groundwater flow in the aquifer.
40
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1254
FACIUTY LJ
LOX FACILITY
NOTE: ADD 1460.00 TO ALL GROUNDWATER
ELEVATIONS FOR EXACT ELEVATION.
^EGEND
MONITORING WELL LOCATION
W/GROUNDWATER ELEVATION
FROM 12/9/94.
CALCULATED GROUNDWATER CONTOURS
Figure 4-5. Potentiometric surface map.
41
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Pump test data from the base appear to indicate a second
prominent anisotropic property that may be related to
faulting at the base. The data appear to indicate the
existence of vertical-oriented hydraulic-flow discontinuities
(Tetra Tech 1993b). The presence of faulting at the base
has led to a hypothesis of a double-porosity, fractured
aquifer system that is characterized by a system of fine-
pore matrix lithology and higher-permeability secondary
fracture porosity. An interpreted zone of higher
conductivity is currently being used for a base-wide
ground water model and appears to provide the best match
for the observed groundwater data collected at the base
(Tetra Tech 1994).
4.1.2.3 Site Contamination
Contaminant characterization activities conducted at Site
31 have included soil gas surveys, advancement of soil
borings and collection of soil samples for chemical and
geotechnical analyses, and placement of groundwater
monitoring wells and sample collection for chemical
analyses. The investigative findings from these activities
indicate that subsurface conditions at Site 31 are fairly
complex and that soil, soil gas, and groundwater contain
elevated levels of VOCs, hi particular, TCE.
Soil
More than 100 surface and subsurface soil samples have
been collected at Site 31 during investigations. Chemical
data from the samples indicate that few organic
compounds have been detected. Based on the analytical
data, it appears that VOCs in the soil are limited to one
location immediately south to southeast of Building 1211.
Samples from borings in these location show detectable
concentrations of TCE ranging from 0.0066 milligrams
per kilogram (mg/kg) to 0.046 mg/kg, and DCE at a
concentration of 0.0075 mg/kg. A review of the soil
samples results and the site's history suggests that these
areas are suspected source areas for VOC contamination in
the groundwater (TETC1994). The location of the source
area relative to the UVB system is presented in Figure 4-6.
Soil Gas
To further characterize and locate potential contaminant
source areas, two soil gas investigations were conducted at
Site 31 during January, 1992 and September, 1993 (TETC
1994). During the investigations, soil gas samples were
collected from depths of 5,10,20, and 30 feet (1.5,3.0,6.1,
and 9.1 m) bgs. Soil gas concentrations of up to 342 jig/L
TCE and 200 jig/L DCE along with minor concentrations
of tetrachloroethene, chloroform, and 1,1,1-TCE were
detected, predominantly along the southern and eastern
sides of Building 1211. The highest concentrations of
TCE in the soil gas appeared to be concentrated at the 20-
foot (6.1m) sample interval and coincide with the elevated
groundwater concentrations south of Building 1211.
Groundwater
Twenty-two groundwater monitoring wells are present at
Site 31 (Figure 4-7). Chemical analysis of groundwater
samples from these wells indicates that elevated
concentrations of chlorinated hydrocarbons are present, in
particular TCE and DCE. Before the UVB was installed,
concentrations of up to 2,000 ug/L TCE and 210 |j.g/L of
DCE have been detected in groundwater samples at Site
31. Table 4-1 presents a compilation of TCE
concentrations in groundwater from Site 31. Based on the
tabulated results, the highest concentrations of TCE
appear to be located in samples collected immediately
south of Building 1211. An interpretation of TCE
concentrations from in situ groundwater sampling
collected during remedial investigation activities is
presented as Figure 4-8. This interpretation indicates the
presence of a second area of elevated TCE concentrations
located northeast of the UVB system.
Prior to system startup, the distribution of TCE vertically
within the aquifer at Site 31 appeared somewhat stratified,
with the highest concentrations detected in shallow and
intermediate screened wells (approximately 40 to 80 feet
[12.2 to 24.4 m] bgs) and the lowest concentrations
detected in deep screened wells (approximately 90 to 105
feet [27.4 to 32.0 m] bgs). Due to the long (40 feet [12.2
m]) screen intervals of many of the monitoring wells,
contaminant stratification cannot be assessed in more
detail. Well-specific screen intervals, depths, and
locations for all Site 31 monitoring wells are presented in
Table 4-2.
4.1.3 Demonstration Objectives and
Approach
The SITE demonstration was designed to address primary
and secondary objectives selected for evaluation of the
UVB technology. These objectives were selected to
provide potential users of the UVB technology with the
necessary technical information to assess the applicability
42
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(Concrete
1 Slab
jw/ Floor
Drain*
Figure 4-6. Site 31 source locations.
43
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I.EGEND
GROUNDWATER MONITORING WELL LOCATION
UVB SYSTEM WELL AND MONITORING
WELLS (W-1, W-2, AND W-3)
Figure 4-7. Well location map.
44
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Figure 4-8. Site 31 TCE plume from in situ data.
46
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of the treatment system to other contaminated sites. For
the SITE demonstration of the UVB technology, three
primary and seven secondary objectives were selected and
are summarized below:
Primary Objectives:
(PI) Determine the concentration to which the UVB
technology reduces TCE and DCE in groundwater
discharged from the treatment system
(P2) Estimate the radius of circulation cell of the
groundwater treatment system
(P3) Determine whether TCE and DCE concentrations
have been reduced in groundwater (both vertically and
horizontally) within the radius of circulation cell of
the UVB system over the course of the pilot study
Secondary Objectives:
(SI) Assess homogenization of the groundwater
within the zone of influence
(S2) Document selected aquifer geochemical
characteristics that may be affected by oxygenation
and recirculation of treated groundwater
(S3) Determine whether the treatment system induces
a vacuum in the vadose zone that suggests vapor
transport
(S4) Estimate the capital and operating costs of
constructing a single treatment unit to remediate
groundwater contaminated with TCE and DCE
(S5) Document pre- and post-treatment off-gas
volatile organic contaminant levels
(S6) Document system operating parameters
(S7) Evaluate the presence of aerobic biological
activity in the saturated and vadose zones
The demonstration program objectives were achieved by
collecting monthly samples from the groundwater, soil
gas, and the UVB system process air stream over a 12-
month period. To meet the demonstration objectives, data
were collected and analyzed using the methods and
procedures summarized in Section 4.2.
4.2 Demonstration Procedures
This section describes the methods and procedures used to
collect and analyze samples for the SITE demonstration of
the UVB technology. The field and analytical methods
used to collect and analyze samples were conducted hi
accordance with the procedures outlined in Sections 4.2.2
and 4.2.3. The activities associated with the UVB SITE
demonstration included (1) demonstration preparation, (2)
demonstration design, (3) groundwater and soil gas
sample collection and analysis, and (4) field and
laboratory QA/QC.
4.2.1 Demonstration Preparation
Predemonstration activities included drilling seven soil
borings and the subsequent installation and completion of
six groundwater monitoring wells and one soil gas well to
evaluate the UVB system. The groundwater monitoring
wells were placed in two clusters, with each cluster
containing three wells: a shallow, intermediate, and deep
screen well (Figure 4-9). The well clusters were placed
such that the outer cluster served as a control set for
comparison with inner cluster results. Based on the
preliminary estimate of the UVB system's radius of
circulation cell of approximately 50 feet (15.2 m), the
monitoring well clusters were placed at approximately 40
and 90 feet (12.2 to 27.4 m) from the UVB system well.
The soil gas well was located approximately 65 feet (19.8
m) from the UVB system well.
i ,
A second phase of site preparation activities was
conducted before the dye trace study began. Field
activities associated with the dye trace study included the
installation of two additional groundwater monitoring
wells and the setup of a field laboratory for analysis of
fluorescent dyes. The two wells were located
approximately 40 feet (12.2 m) from the UVB system well
and were completed as shallow screen monitoring wells.
4.2.2 Demonstration Design
This section describes the sampling and analysis program
and sample collection frequency and locations. The
purpose of the demonstration design was to collect and
analyze samples of known and acceptable quality to
achieve the objectives stated in Section 4.1.3.
48
-------
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49
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4.2.2.1 Sampling and Analysis Program
To meet the demonstration objectives, the sampling and
analysis program was divided into three phases: (1)
baseline sampling, (2) long-term sampling, and (3) dye
trace sampling.
Baseline sampling included the collection of groundwater
samples from eight monitoring wells and one soil gas
sample from the soil vapor monitoring well before system
start-up. This sampling provided documentation of
baseline conditions at the site and was used in achieving
the demonstration objectives. Groundwater samples were
analyzed for VOCs, dissolved metals, and general
chemistry parameters. The air sample was analyzed for
VOCs and fixed gases oxygen (O2), nitrogen (N2), and
carbon dioxide (CO^. An overview of the sampling and
analysis conducted for baseline sampling is shown hi
Tables 4-3 and 4-4.
Long-term sampling included monthly collection of
groundwater samples from eight monitoring wells, a soil
gas sample from the soil vapor monitoring well, and air
samples from the three UVB process air streams. These
samples were collected for 6 consecutive months after
system start-up. Groundwater samples were analyzed for
VOCs, dissolved metals, and general chemistry parameters.
AH air samples from system air sampling ports were
analyzed for VOCs. The air samples from the vadose zone
were analyzed for VOCs and fixed gases. The fixed gas
determinations were performed to evaluate the potential
for increasing microbiological activity hi the vadose zone.
Samples from the ambient air and contaminated air before
treatment were also analyzed for fixed gases. At the end of
the 6-month period, sampling of the soil gas and system
process air stream was terminated and an additional 6
months of modified monthly groundwater sampling was
performed. The modified sampling events consisted of the
collection and analysis of groundwater samples from
shallow and intermediate depth monitoring wells for
VOCs only. Tables 4-3 and 4-4 provide an overview of the
sampling and analysis performed for long-term air and
groundwater sampling.
Dye trace sampling was conducted to further evaluate of
the system's radius of circulation cell. After fluorescent
dyes were injected into the UVB-generated groundwater
circulation cell, groundwater samples were collected from
13 wells three times a week for a 4-month period. Samples
were collected for both qualitative and quantitative
analysis of fluorescence. Table 4-5 provides an overview
of the frequency performed for the dye trace sampling. A
more detailed description of the dye trace study project
background, dye study design, field procedures, analytical
methods, quality assurance/quality control, data
interpretation, results, and conclusions is presented in the
Dye Trace Study Report presented hi Appendix A.
4.2.2.2 Sampling and Measurement Locations
Sampling locations were selected based on the
configuration of the treatment system and project
objectives; analytical parameters were selected based on
the contaminant to be treated and project objectives. The
locations at which samples were collected and field
measurements taken during the demonstration are shown
on Figures 4-7 and 4-9. Tetra Tech collected groundwater
samples at eight locations and vapor samples at one
location for the baseline sampling events. Groundwater
was collected from eight locations and vapor samples from
four locations for long-term sampling events. Groundwater
samples were collected from 13 locations for the dye trace
study. The eight baseline and long-term groundwater
monitoring locations are identified on Figures 4-7 and 4-9
as wells Wl, W2, and PW1 through PW6.
The 13 dye trace study groundwater monitoring locations
are also identified on Figure 4-7 as Wl, W2, PW1 through
PW8,4MW14,31PW1, and 31OW1. Wells PW1 through
PW6 were installed in clusters of three, at three different
depths in the aquifer and at two separate radii from the hi
situ stripping well. One cluster is within the originally
estimated radius of circulation cell of the UVB system, and
the other cluster is outside the originally estimated radius
of circulation cell. Thus, the rationale for placement of the
wells was to install one cluster within the expected radius
of circulation cell of the UVB system well, while the other
cluster acted as a control set. The well depths were placed
to monitor (1) the upper portion of the aquifer hi the
discharge zone of the UVB system well, (2) hi the middle
of the aquifer hi the intake zone of the UVB system well,
and (3) in the lower portion of the aquifer below the UVB
system well.
The four air monitoring locations are identified on Figure
4-9 as Al through A3 and Vl. These locations measured
system air as follows: Al is ambient air, A2 is
contaminated ah" prior to treatment, A3 is post-treatment
air, and VI is soil vapor from the vadose zone.
50
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53
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4.2.3 Sampling Methods
This section describes the sampling or measurement
procedures at each sampling location.
4.2.3.1 Groundwater Samples
Groundwater samples were collected from monitoring
wells at the locations identified in Section 4.2.2.2 and
depicted on Figures 4-7 and 4-9. Monitoring wells
sampled during baseline and long-term sampling events
were purged prior to sampling using a submersible pump
or bailer. Before purging, the static water level was
measured using an electric sounder and recorded on the
well purging and sampling form. After the static level was
measured, astainless steel Grundfos Redi-Flo2 submersible
pump was lowered down the well and set at the mid point
of the water column in the well casing. Monitoring wells
were purged of at least three well volumes and until
groundwater parameters stabilized (that is, pH, specific
conductance, and temperature were within 10 percent of
previous readings). Purge water samples were collected
and analyzed in the field for pH, specific conductivity,
temperature, and reduction/oxidation potential after each
well volume. Dissolved oxygen was measured during
sampling. These parameters were recorded on the
summary sheet for water sampling.
Groundwater samples were collected immediately after
the well was purged. Samples were collected from the
mid-screen interval of the well using a disposal acrylic
bailer lowered into place by a nylon rope. New bailers
were used at each sample location to eliminate the
potential for cross contamination. Groundwater was
immediately dispensed from the bailer directly into
precleaned sample containers (provided by a commercial
supplier). The samples collected for laboratory analysis
were preserved appropriately for the tests to be performed.
When samples for determination of organic compounds
were collected, the sample was introduced into the vials
gently to reduce agitation that might drive off volatile
compounds. The samples were collected directly into the
vial without introducing any air bubbles. Each vial was
filled until a meniscus appeared over the top. The screw-
top lid with the septum (Teflon side toward the sample)
was then tightened onto the vial. After tightening the lid,
the vial was inverted and tapped to check for air bubbles.
If any air bubbles were present, the sample was recollected
by filling a new, preserved vial. Samples collected for
dissolved metals analysis were filtered in the field through
a 0.45 micron filter using a peristaltic pump.
During the dye trace study, groundwater grab samples and
passive dye receptors, known as carbon bugs, were
collected for qualitative and quantitative analysis of
fluorescence. The methods and procedures used to collect
and analyze the both the grab and carbon bug samples are
discussed in the dye trace study report presented in
Appendix A.
4.2.3.2 Gas Samples
Gas samples were periodically collected at locations
shown on Figure 4-9 to monitor changes and relative
differences between ambient air, treated and untreated air,
and soil gas. Gas samples were collected in 6-liter
SUMMA canisters. The canisters were attached to the
specified sampling locations via disposable Teflon tubing.
The tubing was purged with the air stream to be sampled
before it was attached to the SUMMA canister. The
canisters were allowed to fill for 7 to 15 seconds. Gas
samples were analyzed for VOCs or fixed gases.
4.2.4 Quality Assurance and Quality
Control Program
Quality control checks and procedures were an integral
part of the UVB SITE demonstration to ensure that the QA
objectives were met. These checks and procedures
focused on the collection of representative samples absent
of external contamination and on the generation of
comparable data. The QC checks and procedures
conducted during the demonstration were of two kinds: (1)
checks controlling field activities, such as sample
collection and shipping, and (2) checks controlling
laboratory activities, such as extraction and analysis. The
results of the field quality control checks are summarized
intheTER(PRC1995).
4.2.4.1 Field Quality Control Checks
As a check on the quality of field activities including
sample collection, shipment, and handling, three types of
field QC checks (field blanks, trip blanks, and equipment
blanks) were collected. In general, these QC checks
assessed the representativeness of the samples, and
ensured that the degree to which the analytical data
represent actual site conditions was known and
documented. Any QC results that fail acceptance criteria
54
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and could not readily be corrected in the laboratory were
reported to the project manager or QA manager as soon as
possible to effect corrective action. If a field QC check
sample exceeded the established criteria for any analytical
parameter, analytical results of that parameter for all
associated samples having the analyte concentration
above the quantitation limit were flagged during post-
laboratory validation.
4.2.4.2 Laboratory QC Checks
Laboratory QC checks were designed to determine
precision and accuracy of the analyses, to demonstrate the
absence of interferences and contamination from
glassware and reagents, and to ensure the comparability of
data. Laboratory-based QC checks consisted of method
blanks, matrix spikes/matrix spike duplicates, samples/
sample duplicates, surrogate spikes, blank spikes/blank
spike duplicates, and other checks specified in the
analytical methods. The laboratory also performed initial
calibrations and continuing calibration checks according
to the specified analytical methods. The results of the
laboratory internal QC checks for critical parameters are
summarized on a method-specific basis in the TER (PRC
1995).
Routine QC was performed for the noncritical general
chemistry parameters. At least one laboratory duplicate
and check standard was run for every batch (minimum of
one per 20 samples) for alkalinity and total dissolved
solids (TDS). Laboratory blanks were also run for these
parameters. Duplicate samples were run for all other
noncritical analyses at a frequency of 10 percent or at least
one per batch. The relative percentage difference (RPD)
acceptance criteria for duplicate analyses was 20 percent.
Additionally, check standards and laboratory blank
samples were run for metals analyses. The results of the
laboratory internal QC checks for noncritical analyses are
also presented in the TER (PRC 1995).
4.3 Demonstration Results and
Conclusions
This section presents the operating conditions, results and
discussion, data quality, and conclusions of the SITE
demonstration of the UVB treatment system. The SITE
demonstration provides the most extensive UVB
performance data to date and serves as the foundation for
conclusions on the system's effectiveness and applicability
to other cleanups. The demonstration results have been
supplemented by information provided by the vendor on
other sites undergoing remediation using the UVB
treatment system.
4.3.1 Operating Conditions
This section summarizes the configuration of the UVB
system, operating parameters, and system maintenance
performed on the UVB during the 12-month demonstration.
During the SITE demonstration, the UVB treatment
system was operated at conditions determined by the
developer. To document the UVB system's operating
conditions, groundwater influent and effluent and system
process air stream were periodically monitored and
sampled. The system operated continually, 24 hours a day,
7 days a week over the demonstration period with the
exception of periodic maintenance checks. The UVB
technology was presented by the developer as a highly
efficient in situ system requiring minimal maintenance for
the remediation of volatile organic compounds in the
groundwater, unsaturated zone, and the capillary fringe.
The UVB system installed at Site 31 was designed to
remove chlorinated hydrocarbons from the groundwater
and did not address removal of other contaminants from
either the unsaturated zone or capillary fringe.
4.3.1.1 UVB Treatment System Configuration
The UVB well installed at Site 31 consisted of a 16-inch
(40.6 cm) diameter dual screen well installed in a 26-inch
(66.0 cm) diameter bore hole and was completed to a depth
of 83.7 feet (25.5 m) bgs. The two screen sections of the
well were separated by 14.7 feet (4.5 m) of steel casing.
The lower (influent) screen section was 12 feet (3.7 m)
long and was composed of steel bridge-slot casing. The
upper (effluent) screen section extended 13.8 feet (4.2 m)
and was constructed with 4 feet (1.2 m) of bridge-slot
casing and 9.8 feet (3.0 m) of double-cased stainless steel
screen filled with 3/8-inch (1.0 cm) Teflon beads. Final
completion of the well included the placement of a gravel
pack and a bentonite and cement slurry. The well was
completed at the surface with a concrete pad and bolted
well head. The as-built configuration of the UVB
treatment well showing the depth of screen intervals and
well construction materials is provided as Figure 4-10.
The upper and lower screen sections were separated within
the well by an inflatable packer installed at 66.7 feet (20.3
m) bgs. The packer was pierced by an intake pipe that
provided flow from the lower screen section to the
55
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56
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groundwater stripping unit located in the upper section of
the well. The internal stripping unit components consisted
of a Grandfos Model KP 300 MI submersible pump, a
pinhole (diffuser) plate, a double-wall stripper reactor,
internal centralizers and leveling ballast, and an air intake
pipe. A diagram showing the as-built internal components
of the UVB system well is presented as Figure 4-11. The
discharge throat of the pump was equipped with a 15-
millimeter orifice flow restrictor that provided a constant
upward flow rate of approximately 22 gallons per minute
(83.3 liters per minute) (Weston 1994). To minimize
downhole corrosion, the stripping unit components were
constructed with high density polyethylene or aluminum.
The downhole components of the system well were free-
floating and were self-adjusting to fluctuations in
groundwater elevation.
The above-ground components of the UVB treatment
system included a blower, moisture separator, process air
stream piping, electrical supply, and two 1,800-pound
(816.5 kg) vapor phase carbon adsorption units. The
configuration of the above-ground UVB system
components is shown in Figure 4-12.
4.3.1.2 Operating Parameters
The UVB system was sampled and monitored by Weston
on a regular basis to evaluate the system's performance.
System operating parameters monitored by the developer
included relative humidity, air temperature, linear flow
velocity, pressure in the system's air streams, and VOC
removal in the groundwater discharged from the system.
These parameters were collected from the UVB treatment
well's fresh air intake pipe and the four sampling ports, VI
through V4, installed in the air stream piping by the
developer (Figure 4-12). A summary of the operating
parameter results measured during the demonstration is
presented in Section 4.3.2.2.6.
4.3.1.3 System Maintenance
Routine maintenance and inspection of the UVB system
were performed by the developer four times during the 12-
month demonstration period. The system was shut down
during routine maintenance and inspection for 1.5 to 4
hours. Items inspected during routine maintenance
included: the direction of rotation of the blower fan, fan
belt wear, bearings of the blower motor for wear, water
content in the moisture knockout pot, cables holding the
packer in place, air pressure in the packer, air hose for
wear, pinhole plate for iron buildup and biofilm, vacuum
gauge readings, binding or clogging in the fresh air pipe,
buoyancy of the UVB system, and air to water ratio (air
flow rate and water flow rate). The internal stripping
components were removed by hand and required at least
two technicians. In addition to routine maintenance, the
system was inspected and operating parameters monitored
during regular scheduled sampling activities to provide an
indication of system performance. A summary of
maintenance activities performed by Weston is provided
in Table 4-6. In general, maintenance conducted on the
UVB system during the demonstration consisted of
adjustments to optimize stripping condition within the
well. Ah- stripping of VOCs was optimized by
maximizing both the length of the stripping column and
the volume of air introduced to the well through the
diffuser plate. These functions are controlled by changing
the depth of the stripping unit and the vacuum at the well
head.
System maintenance and inspection was conducted by the
developer throughout the demonstration with the
exception of the period from December 7, 1993 to
February 3,1994. From May 4 to December 7,1993, the
system operated with few problems, requiring only
scheduled maintenance.
The only problem identified during this period was the
displacement of the inflatable packer identified on
November 4,1993. Displacement of the well packer may
have allowed the recirculation of water within the UVB
well casing, possibly causing a greater dilution effect on
the influent contaminant concentrations. However, the
sixth monthly sampling event conducted on October 25,
1993 did not exhibit anomalously low influent
concentrations. From December 7, 1993 to February 3,
1994, no maintenance was conducted due to developer
contractual renegotiations with the March AFB.
After maintenance and inspection resumed in February
1994, several additional problems potentially affecting
system performance were documented. From February 3
to May 17,1994 the system was documented four different
times as having low intake air flow rate and operating at a
depth 2 to 3 feet (0.6 to 0.9 m) lower than preferred by the
developer. Because of the increased depth of the stripping
unit, the vacuum applied during this period may have been
unable to overcome the additional pressure head from the
increased water column. Subsequently, little or no air may
have been introduced to the diffuser plate (as documented
57
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58
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Table 4-6. Maintenance Summary
Date
Weston Maintenance Log
May 4,1993
July 20,1993
Sept 14,1993
Nov4,1993
Dec 7,1993
Dec 7,1993
through
Feb3,1994
Jan 10,1994
Jan 11,1994
Feb3,1994
Feb 18,1994
Feb24,1994
System turned on.
System components pulled to perform routine maintenance. Total down-
time of system: 2 hours, 15 minutes.
System components pulled to perform routine maintenance. Total down-
time of system: approximately 4 hours.
System operating at a lower than desired depth. Discovered that inflatable
packer appears to have raised inside of UVB well casing 2-3 feet (0.6-0.9
m). Deflate packer, push down to desired depth, and reinflate. Packer
motion within the well may indicate short-circuiting across the packer within
the well.
System components pulled to perform routine maintenance. Total down-
time of system: approximately 4 hours.
System was not monitored during this period due to contract renegotiation.
Pull system components to perform maintenance in preparation for up-
coming dye study. Also change original 15 mm flow restrictor for 20 mm
flow restrictor. Total down-time of system: 3 hours, 20 minutes.
Pull system components to fine-tune previous maintenance. Replace
newly installed 20 mm flow restrictor with original 15 mm flow restrictor.
Total down-time: 1 hour, 25 minutes.
Very low intake air flow recorded. May indicate insufficient air-stripping
capabilities within the well.
No intake air flow recorded. Stripping components appear to be operating
at a depth approximately 2 feet (0.6 m) lower than preferred. May indicate
insufficient air-stripping capabilities within the well. Raise system and
secure in place at desired intake air flow rate.
Base personnel report that discharge pipe from system had "fallen off."
Base personnel shut system blower off, but did not shut off submersible
pump. Weston personnel arrive at site on February 25,1994, reinstall
discharge pipe, and turn on blower. Total down-time of blower only: 20
hours, 50 minutes. After restarting system, notice that riser pipe is riding
unusually low. Raise pipe and secure at optimal air intake flow rate.
Mar 18,1994 Very low intake air flow recorded. May indicate insufficient air-stripping
capabilities within the well. Raise system and secure in place at desired
intake air flow rate.
May 11,1994 During biweekly sampling of wells W1 and W3, notice that riser is only
approximately 3 feet (0.9 m) above flange, as opposed to normal height of
approximately 6 feet (1.8 m) above flange. Unable to secure pipe after
raising up. Leave as is.
60
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Table 4-6. Maintenance Summary (continued)
Date Weston Maintenance Log
May 17,1994 Pull system components for routine maintenance. During removal of
components, notice that the third (lowest) buoyancy tank has a hole. This
hole has allowed buoyancy tank to fill with water. This filling with water
caused components to operated at a lower than optimal depth (as noted
several times since February 3,1994). Replace buoyancy tank. System
appears to be operating at preferred elevation and intake air flow. Total
down-time of system: 2 hours.
Aug 26,1994 Riser pipe is riding higher than normal. Adjust to preferred level. System
appears to respond favorably to adjustment.
Oct 26,1994 System shut off completely by Tetra Tech in order to safely perform
additional drilling near the UVB. System restarted on November 3,1994.
Total down-time of system : 135 hours, 30 minutes.
Dec 2,1994 System shut off and pilot program completed at 0815. Components left in
place pending decision by March AFB on final disposition of system.
61
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in the maintenance records), causing a decrease in air-
stripping efficiency of the system. The developer
attempted to alleviate this problem by securing the system
in place at the desired depth and air intake flow rate. This
solution appeared to have had mixed success and required
additional adjustments to the depth of the stripping unit
until the system was removed for maintenance on May 17,
1994. During this maintenance, the leveling ballast
reportedly had filled with water, causing the stripping unit
to operated at a depth lower than preferred by the
developer. After fixing the leveling ballast, no additional
problems were encountered with, the depth of the stripping
unit. Since the system maintenance problems were
encountered immediately after monitoring and inspection
resumed, it is possible that problems may have also been
present while the system was not being monitored.
However, with the exception of the effluent sample
collected in the eighth monthly monitoring event, no
anomalous data were apparent during this period to
suggest significant reduction hi system performance.
The level of system performance from December 7,1993
to May 17, 1994 appears to have affected the effluent
results of at least two monthly monitoring events. Review
of TCE concentrations in the samples collected from the
system effluent in the eighth (December 27, 1993) and
twelfth (April 27, 1994) monthly monitoring events
indicates that stripping efficiencies were significantly
reduced. Since collection of this anomalous data
correlates with documented and inferred maintenance
problems, effluent concentrations during these events may
not be indicative of optimal operation of the UVB system
and will not be used to evaluate of the stripping efficiency
of the system. No other correlations between increased
effluent concentration and reduced system performance
due to maintenance problems were apparent.
4.3.2 Results and Discussion
This section presents the results of the SITE demonstration
of the UVB technology at Site 31, March AFB, California.
The results are presented by project objective and have
been interpreted in relation to each objective. The specific
primary and secondary objectives are shown at the top of
each section in italics followed by a discussion of the
objective-specific results. Data quality and conclusions
based on these results are presented in Sections 4.3.3 and
4.3.4.
4.3.2.1 Primary Objectives
Primary objectives were considered critical for the
evaluation of the Weston/lEG UVB treatment system.
Three primary objectives were selected for the SITE
demonstration of the UVB technology. The results for
each primary objective are discussed in the following
subsections.
Primary Objective P1
Determine the concentration to -which the UVB technology
reduces TCE and DCE in groundwater discharged from
the treatment system.
This objective was achieved by collecting 12 monthly
samples at the influent (Wl) and effluent (W2) sampling
locations and analyzing the samples for TCE and DCE.
The analytical results for TCE and DCE in the system
influent and effluent wells are summarized in Table 4-7.
These results indicate that the UVB treatment system
effectively removed target compounds from the
groundwater. DCE was reduced to below 1 ug/L (the
analytical method detection limit) in all sampling events in
the groundwater discharged from the treatment system.
However, the UVB system's ability to remove DCE could
not be meaningfully estimated due to the low (less than 4
Ug/L) influent concentration of DCE. Additionally, TCE
was reduced by greater than 93 percent in all events except
the fifth, eighth, and twelfth monthly monitoring events.
TCE concentrations in the system's effluent for the eighth
monthly monitoring event showed no indication of
contaminant reduction. This lack of TCE reduction
appears to be a direct result of operating conditions, as
discussed in Section 4.3.1.3. Additionally, maintenance
performed on the system after samples were collected
during the twelfth monthly monitoring event indicated
that the system required adjustments to the depth of the
stripping reactor. During this event, TCE showed a
reduction of only 37 percent, significantly less than
previous events. This decrease in contaminant reduction
appears to be related to the UVB system operating at a
lower depth than preferred by the developer. The results
from the fifth monthly monitoring event may also reflect
slightly diminished operating performance of the UVB;
however, no maintenance problems were identified
immediately before or after the event. During the
demonstration, TCE concentrations hi samples from the
influent well ranged from 14 ug/L to 220 ug/L with an
62
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arithmetic mean of approximately 56 ug/L. Influent TCE
concentrations were significantly lower than TCE
concentrations detected in samples from the surrounding
groundwater monitoring wells located both up-gradient
and downgradient of the system. The persistently low
influent concentrations of target compounds observed
during me demonstration are most likely due to
groundwater recirculation caused by the UVB system.
According to the developer, up to 90 percent of the effluent
water is recaptured by the UVB system, diluting
contaminant levels in the influent groundwater.
Not including the eighth and twelfth monthly monitoring
events, TCE was reduced on average by greater than 94
percent in the groundwater discharged from the UVB
treatment system. The mean concentration of TCE in
samples of the discharged groundwater was approximately
3 jig/L with only one event (third month) above 5 fig/L.
During the third monthly monitoring event, TCE was
reduced by 93 percent, which is approximately the mean
reduction efficiency observed during the demonstration.
This reduction suggests the system was operating at
normal conditions and that the elevated (16 jig/L) effluent
concentration of TCE may be due to the high influent
concentration of TCE (220 ug/L) noted during the event.
The upper confidence limit (UCL) for TCE in samples of
the treated groundwater (excluding the eighth and twelfth
monthly monitoring events) was determined at the 95
percent confidence level using a one-tailed Student's t-
test The UCL was calculated using the following
equation:
UCL^9S — x + (£y/square root of n)
Where:
x
t
s
n
Sample arithmetic mean contaminant
concentration
Student's t-test statistic value for a one-
tail test at the 95 percent confidence level
Sample standard deviation
Sample size (number of measurements)
The following parameters were calculated from the TCE
concentration data presented in Table 4-7 to determined
the UCL.
TCE
x = 3.06
t= 1.833
s = 4.65
n=10
For the calculation of the mean and standard deviation,
sample concentrations below the method detection limit
were assigned the concentration value of the detection
limit (1 |Ag/L). Given the parameters above, the UCL for
TCE in the treated effluent at the 95 percent confidence
level was calculated to be approximately 6 ug/L.
TCE concentrations in the treated water appeared
normally distributed and were usable to calculate the UCL.
However, the UCL for DCE at the 95 percent confidence
internal was not calculated because of the lack of
significant DCE concentrations in the system influent
(mean concentration of 1.6 ug/L) and subsequent
treatment of DCE in all sampling events to below the
method detection limit (1 jig/L).
Primary Objective P2
Estimate the radius of circulation cell of the groundwater
treatment system.
The radius of circulation cell of the UVB system was
estimated using both direct and indirect methods. Because
of the heterogeneous and anisotropic conditions and
potential structural control of groundwater flow at Site 31,
use of both methods was necessary to provide an accurate
estimate of the radius of circulation cell. The radius of
circulation cell was estimated directly by conducting a dye
trace study, which consisted of injecting fluorescent dyes
into the groundwater and subsequently monitoring the
surrounding wells to document dye movement or lack
thereof. The radius of circulation cell was further
evaluated indirectly by (1) modeling the groundwater flow
of the UVB system, (2) analyzing aquifer pump test data,
and (3) assessing changes in target compound
concentrations and the fluctuation of dissolved oxygen
measured in samples from the surrounding groundwater
monitoring wells. The results of both the direct and
indirect methods used to estimate the UVB system's
radius of circulation cell are discussed below. A summary
of the results used to estimate the radius of circulation cell
is provided at the end of the section.
Direct measurement of the radius of circulation cell -
Dve Trace Study
The UVB system's radius of circulation cell was estimated
by conducting a dye trace study that included the analysis
of groundwater grab samples and passive receptors for
fiuorescein and rhodamine WT dyes in wells Wl, W2,
63
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PW1 through PW8, 31OW1, 31PW1, and 4MW14. The
results of the dye study provided both qualitative and
quantitative information on the system's circulation cell.
The qualitative results demonstrate the interconnection
between the UVB system and wells PW1, PW2, and PW3.
The quantitative results provide information for
calculation of aquifer characteristics, groundwater
velocities, and radius of circulation cell of the UVB
system. A discussion of the qualitative and quantitative
results is provided below. A detailed presentation of the
results and conclusions of the dye trace study is provided
in the dye trace study report, Appendix A.
The results from the dye trace study show that a circulation
cell developed between wells Wl and PW2 over a distance
of about 40 feet (12.2 m). Hydraulic interconnection was
demonstrated between wells W2 and P W3 over a distance
of about 45 feet (13.7 m); however, the results do not
indicate whether this interconnection is primarily due to
UVB system circulation or to natural groundwater flow in
the downgradient direction. The absence of dye in wells
other than those installed in the downgradient direction
(southeast) shows that the circulation cell developed less
than 40 feet (12.2 m) in all other directions. Thus, the
radius of circulation cell of the UVB circulation cell was
shown to be at least 40 feet (12.2 m) in the downgradient
(southeast) direction and less than 40 feet (12.2 m) in all
other directions. The interpreted extent of the radius of
circulation cell is depicted in Figure 4-13.
Indirect measurement of the radius of circulation cell -
Modeling
Groundwater modeling is commonly applied to evaluate
and design groundwater treatment systems. Most models
are based on multiple assumptions of the hydrogeologic
conditions at the site. However, these assumptions may
not accurately depict subsurface conditions, especially at a
complex anisotropic and heterogeneous sites such as Site
31. Although limited in accuracy, groundwater modeling
of the UVB system may provide valuable information on
the extent of the system's radius of circulation cell.
Since the UVB system creates a three-dimensional flow
pattern with both vertical and horizontal flow components,
the developer claims that standard numerical capture zone
models do not apply to the UVB circulation cell. Although
standard numerical models may not accurately describe
the circulation zone of the UVB system, they will provide
a conservative estimate of the maximum extent of the
radius of circulation cell since the circulation cell of
vertical wells will be significantly smaller than those
associated with traditional capture wells of equivalent
discharge (Ross et al. 1992).
The radius of circulation cell of the UVB system at Site 31
has been estimated by the developer using the equations
and graphical solutions developed by Dr. Bruno Herrling
(Herrling et al. 1991). These equations and graphical
solutions have been developed over several years and are
based on theoretical and empirical data generated during
operation of the system at other sites. A detailed
description of this model is presented in Appendix B. The
assumptions and calculations for the estimation of the
radius of circulation cell at Site 31 using the Herrling
model were prepared by Weston and are documented in
the draft treatment selection report for the UVB treatment
system (Weston 1994). Based on the Herrling model, the
UVB system circulation cell at Site 31 has a radial distance
of approximately 83 feet (25.3 m) (Weston 1994). This
distance, according to the developer, approximates the
widest part of a roughly elliptical circulation cell.
The Herrling model indicates that the shape of the
circulation cell depends on the anisotropy (horizontal (KJ
over vertical (Kv) conductivity: K^/K^) and the distance
between injection and extraction intervals. These
parameters also influence the amount of water recirculated
by the treatment system. The magnitude of the ratio of K^
and Kv is directly proportional to the effective radius of the
treatment system. Therefore, smaller ratio values result in
a larger percentage of recycled water and, consequently, a
smaller effective radius. Increasing the distance between
the system influent and effluent will also increase the
radius of circulation cell by reducing the amount of
recirculation of flow between the extraction and injection
zones. The radius of circulation cell depends on the
distance between the upper and lower screens. The
distance between the upper and lower screens is restricted
by the thickness of the aquifer. Natural groundwater flow
also influences the circulation pattern by skewing the cell
in the direction of groundwater flow. According to the
developer, the Herrling model has been validated based on
empirical data gathered during implementation of the
UVB system at other sites. The SITE demonstration did
not assess other models nor did it evaluate the validity the
Herrling model.
Based on data generated during operation of the UVB
system at other sites, the developer claims that wells
65
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OIL/WATER
SEPARATOR
Groundwatw Gradient
PW4
LEGEND
^. GROUNDWATER MONITORING WELL LOCATION
Q UVB TREATMENT SYSTEM LOCATION
GROUNOWATER GRADIENT
APPROXIMATE EXTENT OF DYE DETECTION
INFERRED EXTENT OF DYE DETECTION
Figure 4-13. Estimated UVB radius of circulation cell plan view.
66
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within the system's radius of circulation cell will exhibit
an increase in contaminant concentration followed by a
decrease. The increase in dissolved contaminant
concentrations reportedly is related to the dynamics of the
UVB system, which facilitates the partitioning of
contaminants through dissolution, diffusion, and
desorption. The increased partitioning of contaminants to
the dissolved phase through these processes is driven by
increased groundwater flow rates within the system's
radius of circulation cell and by the increased
concentration gradient established by the reinjection and
recirculation of treated water within the aquifer.
According to the developer, the subsequent decrease in
contaminant concentration is due to the removal of
contaminants by the UVB system. During the SITE
demonstration, contaminant levels in both inner and outer
well clusters showed an increase, followed by a decrease,
in target compound concentrations. This may suggest, as
interpreted by the developer's claims, that both well
clusters are within the system's circulation cell and that the
radius of circulation cell of the UVB system extends to at
least 90 feet (27.4 m).
An alternate interpretation of these data suggests that
peaks in target compound concentrations are the result of
the downgradient migration of a high concentration
contaminant plume originating from the vicinity of the
UVB well. As discussed above, this increase in
contaminant concentration may be caused by the
dynamics of the UVB system. As the sources of increased
contamination (adsorbed, absorbed, or liquid contaminants)
are depleted as a result of increased diffusion and
advection, contaminants are no longer readily available
for partitioning to the dissolved phase. This will result in
decreased contaminant levels in the groundwater as the
slug migrates downgradient.
The results of the SITE demonstration indicate a
correlation between contaminant peaks in the inner and
outer well clusters and groundwater flow velocity and
direction. Given the calculated maximum groundwater
velocity from the dye trace study, the occurrence of peak
concentrations matches the travel tune for groundwater to
move downgradient from the UVB system well to the
inner and outer cluster of wells. Since the movement of
contaminants may be controlled by ambient groundwater
flow, the data may support the alternate interpretation and
suggest that a slug of contamination originating at the
UVB system is moving toward the inner and outer cluster
of wells. This interpretation suggests that neither the inner
nor the outer cluster of wells is in the radius of circulation
cell of the UVB system and that the radius of circulation
cell is limited (less than 40 feet [12.2 m]) since
contaminant transport may be controlled by groundwater
flow in the downgradient direction. The data further
support this conclusion, as indicated by the convergence
and stabilization of target compound concentrations
shown in Figures 4-14 and 4-15. Samples from wells
within the radius of circulation cell should continue to
show decreasing concentrations of target compounds
throughout the remediation process. A clear trend in the
convergence and stabilization of contaminant concentration
data has been documented; however, it is possible that
contaminant concentrations within the radius of circulation
cell may continue to decrease over time and that the
system was not monitored over a long enough period to
show the full effects of the UVB system on contaminant
concentration.
An additional interpretation of the data is that the observed
contaminant concentration peaks correspond to the
growth of the UVB system's circulation cell. According to
the developer, the three-dimensional circulation cell
progressively builds on itself like an onion skin. The
observed data could be interpreted to reflect the
advancement of the circulation cell as it builds outward.
As the circulation cell front moves past a monitoring well,
a subsequent increase and decrease of dissolved
contaminant concentration would be observed due to the
dynamics of the UVB system as discussed above. This
interpretation of the data would suggest that both inner and
outer well clusters are within the UVB system's radius of
circulation cell. This interpretation appears to be a
possible explanation of the observed data, assuming that
the circulation cell grows in the downgradient direction at
the rate of groundwater flow. However, the developer
claims the full circulation cell requires approximately 1
month to become established for most sites, which is much
faster than the observed results would indicate. It is
possible that hydrogeologic conditions at Site 31 have
slowed establishment of the circulation cell; however, it
appears unlikely that it would slow to coincide with
groundwater flow velocity and direction.
Indirect measurement of the radius of circulation cell -
Dissolved Oxygen Distribution
The developer claims that samples from monitoring wells
within the system radius of circulation cell will show an
increase in dissolved oxygen concentrations. The field
67
-------
measurement results for dissolved oxygen are presented in
Figure 4-16. The dissolved oxygen data are considered
suspect due to low and erratic readings of the instrument.
In addition, several dissolved oxygen meters were used
during the demonstration, which may attribute to the
variability of the data. Although the data are of suspect
quality and should be used with qualification, a consistent
trend in the dissolved oxygen concentrations in wells Wl
and W2 was observed that is considered meaningful since
it occurred throughout the demonstration, regardless of
instrumentation. This trend indicates that the system
influentdissolved oxygen concentrations were continually
higher than effluent dissolved oxygen levels. This trend
appears to indicate that the UVB system is removing
dissolved oxygen from the groundwater and appears to
contradict the developer's claim of increased oxygenation
within the UVB system's circulation cell. Due to the
suspect quality of dissolved oxygen data and the lack of
observable trends in dissolved oxygen in the surrounding
monitoring wells, however, the UVB system's radius of
circulation cell could not be meaningfully estimated based
on variations in dissolved oxygen concentrations.
Estimation of the radius of circulation cell
Based on the dye tracer study, the radius of circulation cell
was measured to be at least 40 feet (12.2 m) in the
downgradient direction. Modeling of the radius of
circulation cell by the developer further suggests that it
may extend to a distance of approximately 83 feet (25.3
m). However, site-specific data from the pump test
indicate that it is more likely less than 60 feet (18.3 m).
The results of the dye tracer study appear to further suggest
that the shape of the circulation cell is narrow and
elongated in a downgradient direction (southeast). Target
compound distribution suggests that the radius of
circulation cell of the UVB system may be less than 40 feet
(12.2 m) or greater than 90 feet (27.4 m) depending on the
interpretation of the data. Due to the number of variables
independent of effects of the UVB system on the aquifer
that may influence target compound concentrations and
dissolved oxygen measurements, these methods did not
provide a reliable or conclusive estimate of the radius of
circulation cell of the UVB system.
Primary Objective P3
Determine -whether TCE and DCS concentrations are
reduced in groundwater (both vertically and horizontally)
within the radius ofcirculation cell of the UVB system over
the course of the pilot study.
This objective was achieved by collecting and analyzing
groundwater samples for TCE and DCE from wells Wl,
W2, and PW1 through PW6 prior to treatment system
startup and at approximately 1-month intervals throughout
the duration of the pilot study (12 months). Due to the lack
of apparent target compound concentration trends
attributable to operation of the UVB system in the deep
wells, monitoring of wells PW3 and PW6 was
discontinued after the first 6 months of the demonstration.
TCE and DCE results from the demonstration are
presented in Tables 4-8 and 4-9 and are plotted as a
function of tune in Figure 4-14 and Figure 4-15.
Based on the data used to estimate the radius ofcirculation
cell at Site 31, the inner well cluster is likely to be within
the estimated radius ofcirculation cell of the UVB system,
while the outer well cluster was determined to likely lie
outside the estimated radius ofcirculation cell. However,
since the outer well cluster was installed downgradient of
the UVB system, it is possible that the data collected from
these wells may be representative of target compound
concentrations in the outer portion of the radius of
circulation cell. Review of the analytical results from the
inner and outer well clusters revealed several trends hi
target compound concentrations.
Samples from shallow and intermediate inner cluster wells
(PW1 and PW2) showed a sharp increase in TCE
concentrations in the second monthly monitoring event.
TCE concentrations peaked in samples from these wells in
the third monthly monitoring event followed by a gradual
decrease in concentrations from the fourth to the ninth
monthly monitoring events. After the ninth monthly
monitoring event, TCE concentrations hi samples from the
inner cluster shallow and intermediate wells appeared to
converge and stabilize to below baseline levels for the
remainder of the demonstration at an average concentration
of approximately 293 ug/L. The intermediate zone well
samples showed the greatest change, exhibiting a
reduction hi TCE concentration of approximately 64
percent from the baseline concentration of 750 \ig/L while
samples from the shallow zone well exhibited a reduction
of 39 percent from baseline concentrations of 530 ug/L.
During the demonstration, the magnitude of reduction of
TCE appeared to correlate with the baseline concentrations;
the higher the baseline concentration, the larger the
increase and subsequent decrease in concentration
observed.
Target compound concentrations in the shallow and
intermediate outer cluster wells (PW4 and PW5) showed a
68
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similar trend to that observed in the inner well cluster:
increasing concentrations from baseline levels followed
by a subsequent decrease in concentrations. TCE
concentrations in the shallow and intermediate outer
cluster wells showed a gradual increase in concentrations
in the fourth monthly monitoring event and peaked in the
seventh monthly monitoring event. After peaking, TCE
concentrations decreased sharply until the tenth monthly
monitoring event and appeared to converge and stabilize at
a concentration of approximately 263 \ig/L for the
remainder of the demonstration. Although concentrations
in outer cluster shallow well samples were reduced to
below baseline levels, the intermediate well samples
continued to exhibit elevated target compound
concentrations above baseline levels. The shallow well
samples exhibited a reduction in TCE concentrations of 5 5
percent from the baseline concentration of 650 jig/L, while
the intermediate well samples showed an increase of 43
percent from the baseline concentration of 120 ug/L.
These changes suggest that TCE concentrations are
homogenizing vertically in the outer cluster shallow and
intermediate zone wells.
DCE concentrations in samples from the shallow and
intermediate inner and outer cluster wells exhibited a
similar trend to TCE concentrations except that DCE, for
the most part, was not detected above the method detection
limit in the inner and outer cluster shallow well samples.
DCE concentrations in the inner cluster intermediate zone
well samples appeared to converge and stabilize at an
average concentration of approximately 19 ug/L, a
reduction of about 86 percent from the baseline
concentration of 140 \ig/L. DCE concentrations in the
outer cluster intermediate well samples appeared to
converge and stabilize at a concentration of 15 ug/L, an
increase 88 percent from the baseline concentration of 8
TCE and DCE concentrations hi the deep inner and outer
cluster wells (PW3 and PW6) were not monitored for the
full duration of the demonstration. Based on the TCE and
DCE results in samples from these wells, no trends in the
target compound data were observed in samples from well
PW6; however, well PW3 indicated a peaking of target
compound concentrations in the third monthly monitoring
event. This trend appears similar to other wells in the inner
cluster, except that target compound concentrations
remained above background levels. Target compound
concentrations in samples from well PW6 also remained
above baseline levels at the termination of monitoring.
Due to the limited duration of monitoring of the deep
wells, the reduction of target compound concentrations in
this zone could not be definitively assessed.
The system influent well (Wl) also showed a similar trend
to that observed hi the inner well cluster: increasing
concentrations from the baseline levels, peaking in the
third monthly monitoring event, followed by a subsequent
decrease in concentrations. After peaking, concentrations
of target compounds decreased and stabilized with the
exception of the twelfth monthly monitoring event, which
exhibited a sharp increase hi concentration. Over the
course of the demonstration, the average TCE
concentration in samples from well Wl was 56 u.g/L. This
concentration is significantly less than the average
concentration measured in samples from well PW2, the
closest well screened at a similar depth, of 950 |ig/L.
Influent concentrations are controlled by the amount of
mixing and the contaminant concentration of treated and
untreated groundwater. The relatively low influent target
compound concentrations as compared to contaminant
levels in surrounding wells suggest that influent
concentrations were strongly controlled by recirculation
of the system effluent. Comparison of TCE concentrations
in wells Wl and PW2 samples suggest that on average as
much as 94 percent dilution in the system influent has
occurred (assuming that concentrations in PW2 are
representative of TCE concentrations in the intermediate
zone of the aquifer).
Based on the results presented in Tables 4-8 and 4-9, target
compound concentrations hi the shallow and intermediate
zone wells were reduced both vertically and horizontally
except in the intermediate outer cluster well, which
showed an increase in concentrations. Concentrations of
target compounds in these zones appeared to homogenize
as indicated by the convergence and stabilization of target
compound concentrations. Variations in target compound
concentrations were noted in the deep aquifer zone;
however, there was no evidence of reduction or
homogenization of the concentrations. This may be due to
the limited duration of monitoring of these wells.
4.3.2.2 Secondary Objectives
Secondary objectives provided additional information that
is useful, but not critical, for the evaluation of the UVB
system. Seven secondary objectives were selected for the
SITE demonstration of the UVB system. The results of
each secondary objective are discussed in the following
subsections.
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Secondary Objective SI
Assess homogenization of the groundwater -within the zone
of influence.
Aquifer homogenization-was assessed by examining the
levels and relative distribution of TCE and DCE within the
zone of influence as quantified from baseline and monthly
sampling and analysis activities. The results of baseline
sampling indicated that TCE and DCE stratification was
present in the shallow and intermediate zones of the
aquifer. Following the peaks in target compound
concentration in the third and seventh monthly monitoring
events, a converging and stabilizing trend was observed in
both the inner and outer cluster of wells in the shallow and
intermediate zones as depicted on Figures 15 and 16. The
stabilization of target compound concentration in the inner
and outer cluster wells (approximately 293 ug/L in the
inner cluster and 263 ug/L hi the outer cluster) suggests
that aquifer homogenization has occurred. The target
compound concentrations were not homogenized in the
deep wells during the monitoring period. The TCE
concentration hi the inner deep well ranged from 130 to
310 ug/L, and the TCE concentration in the outer deep
well ranged from 92 to 150 ug/L. The variable range in the
inner deep well suggests that concentrations were effected
hi a similar manner as the intermediate and shallow inner
wells. The TCE concentration hi the outer deep well was
more stable throughout the monitoring period, which
suggests that the UVB system effects were minimal for
that well.
Secondary Objective S2
Document selected aquifer geochemiccd characteristics
that may be affected by oxygenation and recirculation of
treated groundwater.
This objective was achieved by analyzing groundwater
from monitoring wells Wl, W2, and PW1 through PW6
for dissolved oxygen, dissolved organic carbon, specific
conductance, alkalinity, oxidation/reduction potential,
pH, total dissolved solids, and dissolved metals. The
results documenting the selected geochemical
characteristics are presented in the TER (PRC 1995).
These results were used to assess the potential oxidation of
mineral surfaces and precipitation of dissolved metals;
changes in dissolved organic carbon; and the presence of
dissolved salts caused by increased oxygen hi the
groundwater.
Groundwater conductivity values measured hi the field
appeared to decrease with depth and appeared correlate
with the analytical results for TDS. Additionally, pH
measurements showed a trend of increasing with depth.
These observed trends do not appear related to UVB
system operation. Total dissolved solid results exhibited a
general increasing trend from the baseline monitoring
event, which may indicate a steady increase hi
groundwater flow in the aquifer because of UVB system
operation. No clear trends were apparent from the
alkalinity or dissolved organic carbon results. The
temperature data is relatively consistent and apparently,
not affected by the UVB system. No clear trends were
apparent from the field measurements of dissolved
oxygen, temperature, or redox potential. However, the
presence of an iron-orange colloidal/precipitant substance
observed in well W2 after the second monitoring event
suggests changes hi conditions favorable to precipitation
of metals. This condition appeared to be localized
adjacent to the UVB system. Iron-orange precipitant
suggests that iron is precipitating out of solution due to
either and increase in pH or increase in redox potential.
Groundwater analytical results for dissolved metals
exhibited no clear trends in the data to indicate the
precipitation of dissolved metals. The data are variable for
barium, chromium, cobalt, iron, nickel, potassium,
selenium, vanadium, and zinc. Fluctuations hi some of
these metal concentrations may be related to well
construction activities or other sources of contamination.
The data for boron, calcium, magnesium, manganese,
molybdenum, silicon, and sodium were relatively constant
and do not indicate effects from the UVB system. The data
for aluminum, antimony, arsenic, beryllium, cadmium,
copper, lead, mercury, silver, tin, and thallium contained
too many results below the method detection limit to allow
a meaningful evaluation of the data.
Secondary Objective S3
Determine whether the treatment system induces a
vacuum in the vadose zone that suggests vapor transport.
This objective was achieved by periodically reading the
vacuum gauge and collecting soil gas samples for analysis
of VOCs in the vapor monitoring well, VI. Readings were
taken before treatment system startup and at monthly
intervals for 6 months. The results of the vacuum
measurements and soil gas samples are presented in Table
4-10.
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No indications of the presence of a vacuum in the vapor
monitoring well were observed during the demonstration.
Results from vapor monitoring well VI indicate that
VOCs were present in the vadose zone. TCE was present
in the soil vapor in all monitoring events, while DCE was
not detected in any monitoring event. The concentration
of TCE was consistently high with TCE concentrations
averaging 40,800 parts per billion on a volume to volume
basis. The consistent and high concentration of TCE in the
vadose zone suggests that significant volatilization of TCE
has occurred in the subsurface. The constant VOC
concentrations and the lack of observed indications of a
vacuum suggest that the UVB system has little or no effect
on volatile organic compounds in the vadose zone in the
vicinity of well VI.
Although the developer claims that the UVB system has
applications to cleanups of both groundwater and soil gas,
the system installed at Site 31 was designed to remove
VOCs from the groundwater only. The critical design
feature that allows the cleanup of both the groundwater
and soil gas in the vadose zone is the placement of the
upper effluent screen. The top of the upper screen of the
UVB well installed at Site 31 was located immediately
above the groundwater table, thus inhibiting the removal
of a significant volume of soil gas from the vadose zone.
Given the design features of the UVB well installed at Site
31, the UVB well did not significantly affect transport of
contaminants in the vadose zone as indicated by the results
from the SITE demonstration,
Secondary Objective S4
Estimate the capital and operating costs of constructing a
single treatment unit to remediate groundwater
contaminated with TCE and DCE.
This objective was achieved by using capital cost
information provided by the developer, measuring
electricity consumption, and estimating kbor requirements.
A detailed estimate of the capital and operating costs of
constructing a single treatment unit to remediate
groundwater contaminated with TCE and DCE is
presented in Section 3.0. Cost have been assigned to one
of 12 categories applicable to typical cleanup activities at
Superfund and RCRA sites and include fixed and annual
variable costs. One-time capital costs for a single
treatment unit were estimated to be $180,000; variable
annual operation and maintenance costs for the first year
were estimated to be $72,000, and $42,000 for subsequent
years. Based on these estimates, the total cost for
operating a single UVB system for 1 year was calculated to
be $260,000. Since the time required to remediate an
aquifer is site-specific, costs have been estimated for
operation of a UVB system over a range of time for
comparison purposes. Therefore, the cost to operate a
single UVB system was calculated to be $340,000 for 3
years, $440,000 for 5 years, and $710,000 for 10 years.
Additionally, the costs for treatment per 1,000 gallons
(3,785 L) of groundwater were estimated to be $260 for 1
year, $110 for 3 years, $88 for 5 years, and $71 for 10
years. The costs for treatment per 1,000 liters (264.2
gallons) of groundwater were estimated to be $69 for 1
year, $29 for 3 years, $23 for 5 years, and $19 for 10 years.
The cost of treatment per 1,000 gallons (3,785 L) refers to
the amount of groundwater pumped through the system.
Potential users of the treatment technology should be
aware that typically 60 to 90 percent of the water pumped
through the system is recirculated water.
Secondary Objective S5
Document pre- and post-treatment off-gas volatile
organic contaminant levels.
This objective was achieved by periodically collecting
process air samples from locations A1, A2, and A3 (Figure
4-9) and chemically analyzing the samples for VOCs.
Sample point A1 is the ambient air sampling port, A2 is the
groundwater stripped sampling port, and A3 is the post air-
treated sampling port. The results of the air analysis is
presented in Table 4-11.
The results from air monitoring of the UVB treatment
system indicated that low concentrations of TCE are being
removed from the groundwater. TCE concentrations
detected in the pre-air treatment samples correlate to
trends observed in target compounds concentrations in the
inner cluster monitoring wells: increasing concentration
from the baseline event to the third monthly monitoring
event with a subsequent decrease in concentrations. The
post-air treatment samples from the fifth and sixth
monitoring events exhibited higher concentrations than
did pre-air treatment samples. This apparent contradiction
may be attributed to analytical variability when the sample
concentration is at or near the method detection limit.
Secondary Objective S6
Document system operating parameters.
81
-------
Table 4-11. UVB Process Air TCE Removal Summary
Trichloroethene ppb.
f/V
Sample Description
1st
5/93
2nd
6/93
3rd
7/93
4th
8/93
5th
9/93
6th
10/93
A-1
Ambient Air
<1.00
1.08
1.40
1.56
2.92
2.02
A-2
A-3
Percent
Notes:
(D
Pre-Air 4.32 3.26 6.76 6.02
Treatment
Post-Air <1.00 <1.00 2.16 1.80
Treatment
Reduction™ 76.9 69.3 68.0 70.1
Percent reduction = FfC,. * - C» «1 / C,» «1 x 1 00: where C,. .* = ore-air treatr
1.82 <1.00
2.08 2.60
-14 -160
lent and
Hg
c(*-a) * post-air treatment
Inches of mercury
Parts per billion on a volume to volume basis
The following process data were provided by Weston:
• Relative humidity measured at the fresh air well
intake, before the blower, after the blower, between
primary and secondary carbon canisters, and from the
carbon adsorption unit exhaust stack
• Temperature measured at the fresh air well intake,
before the blower, after the blower, between primary
and secondary carbon canisters, and from the carbon
adsorption unit exhaust stack
• Linear flow velocity measured at the fresh air well
intake, before the blower, after the blower, between
primary and secondary carbon canisters, and from the
carbon adsorption unit exhaust stack
• Pressure measured at the fresh air well intake, after the
blower, between primary and secondary carbon
canisters, and from the carbon adsorption unit exhaust
stack
A summary of the system operating parameters results is
shown in Table 4-12.
Secondary Objective S7
'! '
Evaluate the presence of aerobic biological activity in the
saturated and vadose zone.
This objective was achieved by periodically collecting and
analyzing air samples from the vadose zone well (VI) and
process air stream locations Al and A2, and by collecting
and analyzing groundwater samples from wells Wl and
W2 and PW1 through PW6. Air samples were analyzed
for fixed gas: nitrogen, oxygen, and carbon dioxide, and
groundwater samples were analyzed for dissolved oxygen,
temperature, and dissolved organic carbon. The fixed gas
results are summarized Table 4-13.
Based on discussions with EPA staff who have extensive
experience in assessing the presence of subsurface
bioactivity, it was deemed acceptable to assume that the
source of increased CO2 levels, combined with a reduction
in O2 levels, in the soil gas was due to increased bioactivity
in the soil, groundwater, or both. Carbon dioxide
concentrations measured in the vapor monitoring well,
VI, indicate that carbon dioxide has increased by more
than 2 percent since baseline monitoring. Several
fluctuations in O2 level were observed; however, there was
82
-------
Table 4-12. System Operating Parameters
Sample
Location
Air Intake
V1
V2
V3
V4
Notes:
Temperature
(°C)
Mean Ranae
18.4
20.4
28.4
25.7
23.4
psia
scfm
fpm
5.5-37.1
10.9-27.2
17.4 - 47.0
13.5-40.2
10.8-35.0
Relative Humidity
(%)
Mean Ranae
75
84
66
72
70
19-
44-
20-
31-
38-
100
100
100
100
100
Mean
14.15
13.96
14.96
14.81
14.71
Vacuum
(psla>
Ranae
13.70-
13.70-
14.46 -
14.71 -
14.70 -
Pounds per square inch absolute = 703.1 kilograms
Standard cubic feet per minute
Feet per minute = 0.5080 centimeters per second
14.57
14.12
15.03
14.84
14.72
Air Flow
(scfm)
Mean Ranae
157 13-568
199 64-279
235 76 - 847
225 63 - 782
253 74 - 898
Velocity
(fpm)
Mean Ranae
2905 220 - 9999
2301 752-3217
2639 877 - 9287
2522 691-8519
2833 802 - 9999
per square meter
no evidence of a downward trend of these concentrations.
The minor changes in CO2 and O2 measured suggest that
bioactivity in the soil and groundwater was not
significantly enhanced by operation of the UVB system.
Additionally, CO2 concentrations measured at the UVB
system's intake and after the blower reveal minor
fluctuations of relative CO2 concentration. These results
also suggest that bioactivity due to increased dissolved
oxygen levels hi the groundwater was not significantly
enhanced due to operation of the UVB system.
4.3.3 Data Quality
This section summarizes the data quality for groundwater
and ah* samples collected and analyzed during the UVB
SITE demonstration. This data quality assessment was
conducted to incorporate the analytical data validation
results and the field data quality QC results, evaluate the
impact of all QC measures on the overall data quality, and
remove all unusable values from the investigation data set.
The results of this assessment were used to produce the
known, defensible information employed to define the
investigation findings and draw conclusions.
A validation review of the analytical data for groundwater
and air samples collected during the UVB SITE
demonstration was conducted to ensure that all laboratory
data generated and processed are scientifically valid,
defensible, and comparable. Data were validated using
both field QC samples and laboratory QC analyses. The
field samples included equipment blanks, field blanks, and
trip blanks. Laboratory samples included method blanks,
surrogate recoveries, initial and continuing calibration,
matrix spike/matrix spike duplicate, and samples/sample
duplicate. Results from these samples were used to
calculate the precision, accuracy, representativeness,
comparability, and completeness of the data.
Summaries of analytical quality control data are provided
in the TER(PRC 1995) to facilitate validation and analysis
of the data. In general, all data quality indicators met the
QA objectives, specified in the Quality Assurance Project
Plan (QAPP) (PRC 1993) for the UVB SITE
demonstration, indicating that general data quality was
good and that the sample data are usable as reported. All
data quality indicators associated with the baseline and
first, seventh, eighth, ninth, eleventh, and twelfth monthly
sampling events met all acceptance criteria specified in the
QAPP (PRC 1993). Data quality outliers from the other
sampling events are identified and discussed in Table 4-
14. None of the outliers discussed in Table 4-14 were
determined to inhibit the usefulness of the demonstration
data in evaluating the demonstration project objectives.
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Additionally, QC control charts of precision and accuracy
for VOCs, as determined by MS recoveries and MS/MSD
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4.3.4 Conclusions
This section presents the conclusions of the UVB SITE
demonstration at March AFB, California. The conclusion
are presented in relation to each objective. For the SITE
demonstration of the UVB technology, three primary and
seven secondary objectives were selected. The
conclusions for each objective are summarized below:
Primary Objectives;
3J*1_ Determine the concentration to which the UVB
technology reduces TCE and DCE in groundwater
discharged from the treatment system.
The UVB effectively removed target compounds from the
groundwater. The UVB system reduced TCE in the
groimdwater discharged from the treatment system to
below 5 ug/L in nine out of the 10 monthly monitoring
events and on average by greater than 94 percent during
events in which the system operated without apparent
maintenance problems. The mean concentration of TCE
in the water discharged from the system was
approximately 3 ug/L; however, the upper confidence
limit for TCE in the treated groundwater at the 95 percent
confidence level was calculated to approximately 6 ug/L.
The UVB system reduced DCE to less than 1 ug/1 in
groundwater discharged from the treatment system;
however, the system's ability to remove DCE cannot be
meaningfully estimated due to the low (less than 4 ug/1)
influent concentration of DCE.
£2, Estimate the radius of circulation cell of the
groundwater treatment system.
The radius of circulation cell was evaluated directly and
indirectly by conducting a dye tracer study, modeling of
groundwater flow, analyzing site-specific aquifer pump
data and assessing changes in target compound
concentrations and dissolved oxygen levels. The results
indicate that the radius of circulation cell is at least 40 feet
(12.2 m) in the downgradient direction and may extend as
far as 90 feet (27.4 m) depending on the interpretation of
data.
Based on the dye tracer study, the radius of circulation cell
was measured to be at least 40 feet (12.2 m) hi the
downgradient direction. Modeling of the radius of
circulation cell by the developer further suggests that it
may extend to a distance of approximately 83 feet (25.3
m). The results of the dye tracer study appear to further
suggest that the shape of the circulation cell is narrow and
elongated in a downgradient direction (southeast). An
aquifer test performed on well 31OW1 indicated that a
pumping well's radius of circulation cell is 60 feet.
Target compound distribution suggests that the radius of
circulation cell of the UVB system may be less than 40 feet
(12.2 m) or greater than 90 i»et (27.4 m) depending on the
interpretation of the data. Due to the number of variables
independent of effects of the UVB system on the aquifer
that may influence target compound concentrations and
dissolved oxygen measurements, these methods did not
provide a reliable or conclusive estimate of the radius of
circulation cell of the UVB system.
P3 Determine whether TCE and DCE concentrations
have been reduced in groundwater (both vertically and
horizontally) -within the radius of circulation cell of the
UVB system over the course of the 12-month pilot study.
Based on the demonstration results, target compound
concentrations in the shallow and intermediate zone wells
were reduced both vertically and horizontally except hi the
intermediate outer cluster well, where samples showed an
increase in concentrations. TCE concentrations hi
samples from these wells were reduced by an average of
approximately 52 percent. Concentrations of target
compounds in these zones appeared to homogenize, as
indicated by the convergence and stabilization of target
compound concentrations. Variations hi target compound
concentrations were noted in the deep aquifer zone;
however, there was no evidence of reduction or
homogenization of the concentrations. This may be due to
the limited duration of monitoring of these wells.
SI Assess homogenization of the groundwater within
the zone of influence.
88
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A convergence and stabilization of TCE and DCE
concentrations was observed in the shallow and
intermediate zones of the aquifer, which suggests
homogenization of contaminant concentrations in the
groundwater.
S2 Document selected aquifer geochemical
characteristics that may be affected by oxygenation and
recirculation of treated groundwater.
No clear trends were observed to indicate significant
precipitation of dissolved metals, changes hi dissolved
organic carbon, or the presence of dissolved salts caused
by the increase in oxygen in groundwater.
S3 Determine •whether the treatment system induces
a vacuum in the vadose zone that suggests vapor transport.
Although the developer claims that the UVB system has
applications to cleanup of both groundwater and soil gas,
the system installed at Site 31 was designed to remove
halogenated hydrocarbons from groundwater only. The
VOC concentrations and vacuum measurements in the
vapor monitoring well indicate that transport of
contaminants was not significantly affected by operation
of the UVB system as currently designed. Changes in
system design and operating parameters may, however,
lead to significant transport of contaminants in the vadose
zone.
S4 Estimate the capital and operating costs of
constructing a single treatment unit to remediate
groundwater contaminated-with TCE and DCE.
One-tune capital costs for a single treatment unit were
estimated to be $180,000; variable annual operation and
maintenance costs for the first year were estimated to be
$72,000, and $42,000 for subsequent years. Based on
these estimates, the total cost for operating a single UVB
system for 1 year was calculated to be $260,000. Since the
time required to remediate an aquifer is site-specific, costs
have been estimated for operation of a UVB system over a
range of time for comparison purposes. Therefore, the
cost to operate a single UVB system was calculated to be
$340,000 for 3 years, $440,000 for 5 years, and $710,000
for 10 years. Additionally, the costs for treatment per
1,000 gallons (3,785 L) of groundwater were estimated to
be $260 for 1 year, $110 for 3 years, $88 for 5 years, and
$71 for 10 years. The costs for treatment per 1,000 liters
(264.2 gallons) of groundwater were estimated to be $69
for 1 year, $29 for 3 years, $23 for 5 years, and $19 for 10
years. The cost of treatment per 1,000 gallons (3,785 L)
refers to the amount of groundwater pumped through the
system. Potential users of the treatment technology should
be aware that typically 60 to 90 percent of the water
pumped through the system is recirculated water.
S5 Document pre- and post-treatment off-gas
volatile organic contaminant levels.
The results from air monitoring of the UVB treatment
system indicated that low concentrations of TCE were
removed from the groundwater. TCE concentrations
reduced by the UVB system correlate to trends observed in
target compound concentrations in the inner cluster
monitoring wells (that is, increasing concentrations from
the baseline event to the third monthly monitoring event
with a subsequent decrease in concentrations).
S6 Document system operating parameters.
The temperature of the internal monitoring ports ranged
from 18.5 to 44.7 °C; the relative humidity ranged from 27
to 100 percent; the vacuum ranged from 13.81 to 15.03
pounds per square inch absolute (9,709.8 to 10,567.6
kilograms per square meter); the air flow ranged from 100
to 898 standard cubic feet per minute (47.2 to 423.9 liters
per second); and the velocity ranged from 1,109 to 9,999
feet per minute (563.4 to 5,079.5 cm/s). According to the
developer, the water flow rate was maintained at 22 gpm (5
cubic meters per hour or 83.3 liters per minute).
S7 Evaluate the presence of aerobic biological
activity in the saturated and vadose zones.
Bioactivity in the soil and groundwater did not appear to be
significantly enhanced by UVB system operation.
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Section 5
UVB Technology Status
The UVB technology is a process patented by IEG mbH,
D-72770, Reutlingen, Germany. The UVB is an in situ
system for remediation of contaminated aquifers,
especially those contaminated with volatile and semivolatile
organic compounds (SVOCs) or heavy metals (Weston
1992). According to the developer, the UVB technology
combines chemical, physical, and biological processes for
the treatment of adsorbed, dissolved, and free phase VOC
and SVOCs. Since its inception in 1986, the UVB
technology has been applied at some 80 sites hi Europe.
Additionally, the developer claims mat the technology has
achieved regulatory acceptance intheU.S. at both the state
and federal levels. A UVB system was first installed at a
U.S. site in September 1992; currently, 22 UVB systems
are operating in eight states.
The developer has provided four select case studies that
document operation of the UVB system at sites in the U.S.
and Germany. The case studies provided by the developer
are present in Appendix B. Two of the cases are from sites
in Germany and involve the remediation of chlorinated
hydrocarbons (TCE, 1,1,1-trichloroethane, and
dichloromethane) in groundwater. The two cases from the
U.S. document the remediation of groundwater
contaminated with benzene, toluene, ethylbenzene, and
xylene at an underground storage tank site in Troutman,
North Carolina, and Weston's interpretation of the data
collected at March AFB, California independent of the
SITE demonstration from May 4, 1993 to December 2,
1994.
90
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Section 6
References
American Public Health Association (APHA). 1992.
Standard Methods for the Examination of Water and
Wastewater. 18th Edition. Washington, D.C.
American Society for Testing and Materials (ASTM).
1990. Analysis of Reformed Gas by Gas Chromatography,
D1946.
Evans, G. 1990. "Estimating innovative technology costs
for the SITE program." Journal of Air and Waste
Management Assessment. Volume 40, Number 7. July.
Fetter, C.W. 1988. "Applied Hydrogeology." Merrill
Publishing Company. Second Edition.
Herrling, B.. J. Stamm, EJ. Alesi, P. Brinnel, F.
Hirschberger, and M.R. Sick. 1991. "InSituGroundwater
Remediation of Strippable Contaminants by Vacuum
Vaporizer Wells (UVB): Operation of the Well and
Report About Cleaned Industrial Sites." June.
IT Corporation. 1994. Personal communication between
Mr. Ben Hough (Tetra Tech) and Mr. Walter Grinyer (IT
Corp), project manager for the Seismic Surveying of
March Air Force Base, California. November
PRC Environmental Management, Inc. (PRC). 1993.
"Roy F. Weston, Inc., Unterdruck-Verdampfer-Brunnen
(UVB) Technology SITE Demonstration at March Air
Force Base, California, Final Quality Assurance Project
Plan." April.
PRC. 1995. "Draft Technology Evaluation Report (TER),
Roy F. Weston, Inc., Unterdruck-Verdampfer-Brunnen
(UVB) Technology SITE Demonstration at March Air
Force Base, California." January.
Ross, D., Philip, R.D., and G.R. Walter. 1992. "Prediction
of Flow and Hydraulic Head Fields for Vertical
Circulation Wells." Ground Water. Volume 30, Number
5. September-October.
Small M.C. and T.N. Narasimhan. 1993.
Removal of Volatile Compounds Using a
Vacuum Vaporizer Well." January.
"In Situ
Tetra Tech, Inc. 1993a. "Seismic Reflection Survey,"
Sites 2, 27, and 31, March Air Force Base, Riverside
County, California. Draft Report Prepared by NORCAL
Geophysical Consultants, Inc. August.
Tetra Tech, Inc. 1993b. "Revised Draft Basewide
Groundwater Modeling Program Conceptual Model
Development and Numerical Model Design Report."
March AFB, California. December.
Tetra Tech, Inc. 1994. Personal communication between
Mr. Ben Hough (Tetra Tech) and Mr. Bob Jons (Tetra
Tech, Inc.), Hydrologist modeling groundwater flow at
March Air Force Base. November.
i
The Earth Technologies Corporation (TETC). 1993.
"March AFB IRP Site 31 Aquifer Testing." Draft Report.
TETC. 1994. "Installation Restoration Program, March
Air Force Base Draft Final Remedial
Investigation/Feasibility Study Report for Operable Unit
1." March.
U.S. Environmental Protection Agency (EPA). 1983.
Methods for Chemical Analysis of Water and Wastes.
EPA-600/4-79-020. Environmental Monitoring and
Support Laboratory, Cincinnati, Ohio, and subsequent
EPA-600/4 technical additions.
EPA. 1987a. Alternate Concentration Limit (ACL)
Guidance. Part 1: ACL Policy and Information
Requirements. EPA/530/SW-87/017.
91
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EPA. 1987b. Test Methods for Evaluating Solid Waste,
Volumes IA-IC: Laboratory Manual, Physical/Chemical
Methods; and Volume II: Field Manual, Physical/
Chemical Methods, SW-846, Third Edition, (revision 0).
Office of Solid Waste and Emergency Response,
Washington, D.C.
EPA. 1988a. "Guidance for Conducting Remedial
Investigations and Feasibility Studies under CERCLA."
EPA/540/G-89/004. October.
EPA. 1988b. Compendium of Methods for the
Determination of Toxic Organic Compounds in Ambient
Air, Second Edition, Atmospheric Research and Exposure
Assessment Laboratory in Office of Research and
Development. EPA/600/4-89/017.
EPA. 1989. "Control of Air Emissions from Superfund
Air Stripping at Superfund Groundwater Sites." OSWER
Directive 9355.0-28. June.
RoyF.Weston(Weston). 1992. "Application of Vacuum
Vaporization Well Technology at Site No. 2 at March
AFB." November.
Weston. 1994. "Pilot Study for Innovative Technology
UVB-Vacuum Vaporization Well, Site 31 March Air
Force Base, CaliforniaDraft Treatment Selection Report."
April.
92
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Appendix A
Dye Trace Study Report
93
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A.1 Introduction
PRC Environmental Management, Inc. (PRC), received
an assignment from the U.S. Environmental Protection
Agency (EPA) to conduct a Super-fund Innovative
Technology Evaluation (SITE) demonstration of tiie
Unterdruck-Verdampfer-Brunnen (UVB) groundwater
treatment system at Site 31, March Air Force Base (AFB),
California. The demonstration was conducted by Roy F.
Weston, Inc. (Weston), in association with IEG
Technologies Corporation (IEG). PRC completed field
evaluation activities in accordance with the Quality
Assurance Project Plan (QAPP) for the UVB demonstration
(PRC 1993). One of the primary objectives of the
demonstration was to estimate the radius of circulation
cell of the UVB technology. However, the UVB system's
radius of circulation cell could not be meaningfully
estimated under the originally planned demonstration
activities due to a lack of contaminant concentration
reduction in the aquifer and the inapplicability of the
aquifer flow evaluation method (Jacobs straight-line
method) proposed in the QAPP. Therefore, EPA
instructed PRC to perform a dye trace study to evaluate the
UVB technology's area of influence. PRC prepared a dye
trace study plan as an amendment to the QAPP to describe
the study approach, field procedures, and analytical
methods (PRC 1994a).
This report documents the field and analytical procedures,
results, and conclusions of the dye trace study drawn to
support the Innovative Technology Evaluation Report
(ITER) to be prepared for the UVB system.
A.1.1 Background
The UVB technology is an in situ groundwater
remediation technology that combines air-lift pumping
and air stripping to remediate aquifers contaminated with
volatile organic compounds. A UVB system consists of a
single well with two hydraulically separated screened
intervals installed within a single permeable zone. The
air-lift pumping occurs in response to negative pressure
introduced at the wellhead by a blower. A mechanical
pump draws water into the well through the lower screened
portion of the well. Simultaneously, air stripping occurs as
ambient air (also flowing in response to the vacuum) is
introduced through a sieve plate located within the upper
screened section of the well, causing air bubbles to form in
the water pulled into the well. The rising air bubbles
provide the air-lift pump effect that moves water toward
the top of the well and draws water into the lower screened
section of the well. This pumping effect is supplemented
by a submersible pump which ensures that water flows
from bottom to top in the well. As the air bubbles rise
through the water column, volatile compounds are
transferred from the aqueous to the gas phase. The rising
air transports volatile compounds to the top of the well
casing, where they are removed by the vacuum blower.
The blower effluent is treated before discharge using
granular activated carbon.
The transfer of volatile compounds is further enhanced by
a fluted and channelized column that increases the contact
time between the two phases and minimizes the
coalescence of air bubbles.
Once the upward stream of water leaves the stripping
reactor, the water falls back through the well casing and
returns to the aquifer through the upper well screen. This
return flow to the aquifer, coupled with inflow at the well
bottom, circulates groundwater around the UVB well. The
extent of the circulation pattern is known as the radius of
circulation cell, which determines the volume of water
affected by the UVB system. A more detailed description
of the UVB system is presented in the ITER.
The hydraulic conductivity of the aquifer affects the radius
of circulation cell of the UVB system. The UVB system
circulation cell includes both untreated and previously
treated groundwater, and its radius is directly proportional
94
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to the ratio of the horizontal to vertical hydraulic
conductivity (Kh to Kv) of the aquifer. Thus, larger ratio
values will result in a greater effective radius. Based on
data contained in the draft report "March AFB IRP, Site
31, Aquifer Testing" (TETC 1993), the radius of
circulation cell (ro) was estimated to be 60 feet (18.3
meters [m]) (see Appendix A), and aquifer characteristics
values were calculated for transmissivity (T, 6,800 gallons
per day per foot [gpd/ft] [9.75 x 10"4 meters squared per
second {m2/s}]) and Kh (90.5 gallons per day per foot
squared [gpd/ft2] [4.26 x 10'3 centimeters per second (cm/
s}]). The calculated value for storativity of the aquifer
underlying Site 31 may be several orders of magnitude low
based on the data from the short-term pumping tests
(TETC estimates a month-long pumping test would be
necessary to accurately calculate storativity). Since
storativity values calculated from the aquifer test were not
considered representative of aquifer conditions, storativity
of the uneonfined aquifer (specific yield) is approximated
by effective porosity (TETC 1994). Storativity can be
approximated by effective porosity in uneonfined aquifers
since storativity of an uneonfined aquifer represents an
actual dewatering of the soil pores. The average effective
porosity at the site is 25 percent (TETC 1994). Because of
the heterogeneous and anisotropic nature of the alluvial
deposits at the site, the value of Kh is estimated to be an
order of magnitude greater than Kv.
In addition to the calculated hydraulic conductivity,
information was gathered on the pumping rate and
hydraulic gradient to estimate the time required for treated
water from the UVB system to travel to the outer perimeter
of the circulation cell. The UVB system operated at a
pumping rate of about 20 gallons per minute (gpm) (75.7
liters per minute) during demonstration activities. Water
level elevations measured before and during the UVB
demonstration showed that the potentiometric surface is
relatively flat with minor undulations of generally less
than 1 foot (0.3 m) across Site 31. Based on the calculated
hydraulic conductivity, the pumping rate, and the
observed hydraulic gradient, it was estimated that treated
water from the UVB system would reach a radial distance
of 40 feet in 30 to 45 days.
A.1.2 Purpose and Goals
The overall purpose of the dye trace study was to achieve
the second primary objective stated in the UVB QAPP: to
estimate the radius of circulation cell of the groundwater
treatment system (PRC 1993). To estimate the radius of
circulation cell, both primary and secondary dye trace
study goals were established. Primary goals were
considered critical to evaluate the radius of the UVB
system's circulation cell. Secondary goals provided
additional information that was useful for understanding
aquifer characteristics, but not critical for establishing the
radius of circulation cell. These goals were achieved by
injecting dyes into the aquifer and subsequently
monitoring their movement by collecting groundwater
samples.
The primary and secondary goals for the dye trace study
are listed below (PRC 1994a).
Primary
• Demonstrate hydraulic interconnection between the
UVB system and distant sample locations
• Demonstrate circulation of groundwater within the
UVB circulation cell
• Estimate the radius of circulation cell of the UVB
system
Secondary
• Estimate maximum and average groundwater velocities
produced by the UVB system
• Quantify selected aquifer characteristics
A.1.3 Dye Trace Study Design
The dye trace study used water-soluble dyes that could be
detected both visually and by measuring the fluorescent
emissions resulting from ultraviolet light excitation. The
dye trace study was based on PRC Standard Operating
Procedure 98, which was appended to the dye tracer study
plan (PRC 1994a). The basic design for the dye trace study
was a two-dye approach consisting of injecting one dye
into the outlet of the UVB system (diverging test) and
injecting a second dye in well PW2 (converging test), the
intermediate depth well from the well cluster nearest the
UVB system. A two-dye approach was selected to reduce
the time required to demonstrate circulation in the zone
between the UVB system and wells PW1 and PW2.
Sodium fiuorescein (uranine or yellow-green xanthene)
was selected as the dye for the diverging test, in which dye
was injected in the upper screened interval of the UVB
95
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system and spread radially outward. Rhodamine WT (red-
purple xanthene) was selected for the converging test, in
which a dye was injected in well PW2 and flowed back to
the lower screened interval of the UVB system. Both dyes
are considered environmentally safe (EPA 1991).
Fluorescein was selected for the diverging test because
greater dilution occurs in a diverging test and this dye can
be detected at very low concentrations. Greater dilution
occurs in the diverging test because the dye is expected to
diverge radially from the injection point with some
preferential movement in the downgradient direction (dye
in the converging test is expected to travel preferentially
toward the convergence point with some dye movement in
the downgradient direction). Because fluorescein
fluoresces with a higher intensity than rhodamine WT,
fluorescein theoretically has a lower limit of detection on
a scanning spectrofluorophotometer. (Theoretically,
rhodamine WT has a lower limit of detection on a
fluorometer because rhodamine WT (1) has a narrower
emission bandwidth, and (2) the peak emission frequency
is higher than most naturally occurring background
fluorescence.) Rhodamine WT dye was selected for its
contrasting fluorescent color (bright yellow-orange) as
compared to fluorescein (bright green).
The appropriate quantities of dye for this study were
determined by assuming a target concentration of 10
micrograms per liter (ug/L) in the circulation cell and dye
recovery of only 1 percent. A conservative estimate of dye
toss of 99 percent (1 percent recovery) was used to account
for adsorption, attenuation, and degradation of dye in the
aquifer. The volume of water in the circulation cell was
estimated at 448,800 gallons (1,698,708 liters), and the
dyes were obtained in 7.5 percent (fluorescein) and 20
percent (rhodamine WT) solutions. The minimum dye
quantities at these concentrations were thus calculated as
5.7 gallons (21.6 liters) of fluorescein and 1.89 gallons
(7.2 liters) of rhodamine WT (Appendix B). The
movement of the dye was monitored by sampling wells
three times a week. Monitoring wells within 50 feet (15.2
m) of the UVB system were sampled at a higher frequency
during the first week of the study. Wells sampled
included: Wl, W2, PW1, PW2, PW3, PW4, PW5, PW6,
PW7, PW8,31OW1,31PW1, and 4MW14 (well locations
are shown on Figure A-l). Well construction information
on these wells is provided in Table A-l. Wells PW1
through PW6 were installed linearly downgradient of the
UVB system well. Wells PW1 and PW4 are shallow
(screened 38 to 58 feet [11.6 to 17.7 m] below ground
surface [bgs]); wells PW2 and PW5 are intermediate
(screened 65 to 75 and 68 to 78 feet [19.8 to 22.9 and 20.7
to 23.8 m] bgs); and wells PW3 and PW6 are deep
(screened 90 to 105 and 91 to 106 feet [27.4 to 32.0 and
27.7 to 32.3 m] bgs). The downgradient direction was
originally determined to be to the southwest based on a
preliminary contour map of November 1992 groundwater
elevations at Site 31 (TETC 1994). New data collected
after the UVB system was turned off in December 1994
also shows that groundwater flow direction is to the
southeast. A detailed discussion of the groundwater
gradient is presented in Section 3.3.
Sampling methodology consisted of using dedicated,
disposable bailers to collect groundwater samples from
the screened portion of each well. Point source bailers
were used to collect the samples from wells not screened
across the water table. The collected samples were
transferred to amber bottles for subsequent quantitative
analysis. The quantitative results were confirmed by use
of activated carbon units (bugs) installed as passive dye
receptors in the screened interval of sampling wells. The
bugs were changed weekly and qualitatively analyzed for
the presence of dye.
Analytical methodology included both field and
laboratory methods. Field analysis consisted of visual
examination of water samples using both ambient and
ultraviolet lighting to examine for dye presence. At low
concentrations (approximately 10 ng/L), both dyes were
readily visible with these simple methods. Additionally, a
scanning spectrofluorometer was used in the on-site
laboratory for the analysis of fluorescent emissions. The
scanning spectrofluorometer can detect lower dye
concentrations and is not significantly affected by
background interferences.
Wells were monitored for dye for 4 months. This period
was the maximum duration deemed practical based on
conservative estimates of dye travel time from the UVB
system to outer perimeter well PW5.
96
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OIL/WATER
SEPARATOR
^ 310Wt
Vfc
LgGEMO
GROUNDWATERMONiTORJNG WELL LOCATION
UVB TREATMENT SYSTEM LOCATION
GROUNDWATER GRADIENT
Figure A-l. Well location map.
97
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A.2 Methodology
This section describes the methods and procedures used
for field and analytical activities. An overview of the dye
trace study is provided in Section 2.1. The field sampling
activities are described in Section 2.2, and the analytical
activities are addressed in Section 2.3.
A.2.1 Dye Trace Study
The activities associated with the dye trace study included
(1) collecting background samples and evaluating
background fluorescence, (2) injecting the dye, (3)
collecting carbon bugs and groundwater grab samples, (4)
qualitatively analyzing carbon bug samples to determine
the presence or absence of dye, (5) quantitatively
analyzing groundwater samples to measure dye
concentrations, and (6) field and laboratory quality
assurance and quality control (QA/QC) samples and
calibration checks to measure accuracy, precision, and
instrument performance.
Background samples consisted of both carbon bugs from
wells PW1, PW2, PW4, and PW5, and grab samples from
all monitoring wells. The carbon bugs were analyzed
qualitatively, and the grab samples were analyzed both
qualitatively and quantitatively. Grab samples of
groundwater were collected from the wells three times per
week, and the carbon bugs were changed weekly. The grab
samples were qualitatively analyzed by observation under
visual-ambient light conditions and under visual
ultraviolet light. The grab samples also were analyzed on
a scanning spectrofluorometer to quantify the dye
concentration. The carbon bugs were eluted and visually
inspected for the presence of dye. The QA/QC program
consisted of field (equipment) and laboratory blank
samples, duplicate samples, matrix spike and matrix spike
duplicate (MS/MSD) samples, trip blanks (for the carbon
bugs), and calibration standards for each type of dye. A
more detailed discussion of the field and analytical
activities is presented in the following sections.
A chronology of key events is provided in the following
summary:
• January 10, 1994: Carbon bugs installed for
background fluorescence study
• January 18, 26, and February 2, 1994: Groundwater
grab samples collected for background fluorescence
study
• January 26, 1994: Carbon bugs collected for
background fluorescence study
• January 27, 1994: Method detection limit study
conducted
• February 2, 1994: Background fluorescence study
conducted (analysis of background groundwater grab
samples and carbon bugs)
• February 8, 1994: Dye injected into groundwater
monitoring wells PW2 and W2
• February 8, 1994 through February 14, 1994:
Groundwater samples collected from wells PW1,
PW7, PW8, and 31OW1 at accelerated frequency (see
Section 2.2.4 for details)
* February 9, 1994: Groundwater samples collected
from wells Wl, PW4, PW5, 4MW14, and 31PW1 at
normal frequency (three times per week)
• February 9, 1994: Fluorescein detected in well Wl
• February 25, 1994: Well PW3 added to sample
collection locations
99
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• February 25, 1994: Rhodamine WT detected in well
PW3
• March 28,1994: Fluorescein detected in well PW1
• April 8,1994: Fluorescein detected in well PW3
• April 27,1994: Well PW6 added to sample collection
locations
• May 4,1994: Rhodamine WT detected in well Wl
• May 27, 1994: Sampling for dye trace study
terminated
A.2.2 Field Procedures
This section describes the procedures used for field
activities, including dye injection, sample collection
(including frequency and location), and the field QA/QC
plan.
A.2.2.1 Dye Injection
The liquid forms of fluorescein and rhodamine WT were
chosen to avoid potential mixing problems in the field.
The dyes were handled separately to avoid cross
contamination. The dyes were injected on February 8,
1994, Two gallons (7.6 liters) of rhodamine WT were
Injected into well PW2 at 0950 hours, and 6 gallons (22.7
liters) of fluorescein were injected into well W2 at 1000
hours. The dyes were injected through dedicated hoses to
control the depth of injection and to avoid dye loss on the
inside of the well casing. The rhodamine WT was injected
into the bottom of the screen in well PW2 at a depth of 74
feet (22.6 m) bgs. The depth for rhodamine WT injection
was selected to intercept the converging portion of the
circulation cell near the elevation of the UVB system
intake. However, subsequent observations showed that
Uie dye was diluted across the entire water column in well
PW2, and that the injected dye did not remain in the
injection interval. The fluorescein dye was injected at the
top of well W2, which was screened across the
groundwater table. The depth for fluorescein injection
was selected to intercept the diverging portion of the
circulation cell near the elevation of the UVB system
discharge. Observations of grab samples from W2 also
indicate that fluorescein was diluted across the entire
water column in the well (40 to 55 feet [12.2 to 16.7 m]
bgs). The dilution of dye across the water column in both
injection wells (PW2 and JV2) does not impact the study
goals since no groundwater was removed from eitherwells
during the course of the study with the exception of grab
samples.
A.2.2.2 Sample Collection
This section describes the sample collection procedures
for grab samples of groundwater and for the carbon bugs.
A.2.2.2.1
Grab Samples
Groundwater samples were collected from 15 locations in
13 wells (see Section A.2.2.4 for frequency and location
information). The samples were collected by lowering
dedicated, disposable bailers to the required sampling
interval of the well screen.. To address concerns over the
frequency of purging effects on the UVB system flow field
and subsequent dye trace study results, purging of
monitoring wells was kept to a minimum and was
restricted to monthly groundwater sampling as specified
in the QAPP (PRC 1993). Therefore, the groundwater
samples collected for the dye trace study were collected
without purging the wells. Since the wells were not purged
before sample collection, the bailers were lowered and
retrieved with care to minimize mixing water between the
casing and screened sections of the well. This approach
did not adversely affect the dye trace study results due to
the stability of the selected dyes and the frequency of
sampling. On retrieval from each well, the collected
groundwater samples were poured into 250 milliliter (mL)
amber glass sample containers.
A.2.2.2.2 Carbon Bugs
The dye trace study used activated carbon passive dye
receptors known as "bugs" for collecting composite
samples for qualitative analysis. The bugs provided visual
evidence of the presence of dye by adsorbing dye and then
releasing it when washed with an elutriate solution. The
bugs accumulate dye even from very low concentrations in
the groundwater and, thus, provide confirmation of
positive detections at very low concentrations. The bugs
were suspended by a teflon-coated wire line in the
screened interval of each well in the sample network. The
bugs consisted of activated coconut charcoal, size 6 to 14
mesh, contained in packets made of nylon window screen.
Before use, the activated charcoal was kept fresh in airtight
containers. On retrieval, each bug was sealed separately in
a plastic bag with a prelabeled sample tag attached.
100
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A.2.2.3 Background Samples
Groundwater grab samples were collected on January 18
and 26 and February 2,1994, before dye was injected into
the aquifer. In addition, carbon bugs were placed in wells
PW1, PW2, PW4, and PW5 for 16 days beginning January
10, 1994. These background samples were collected to
evaluate interference from natural or introduced
background fluorescence. The samples were collected as
described in Section A.2.2.2 and analyzed as described in
Section A.2.3. The results of the analysis are presented in
Section A.3.1.1.
The background samples also were used to establish the
minimum detection limit (MDL) and reportable detection
limit (RDL) for the scanning spectrofluorometer used for
this study. (A description of this unit is given in Section
2.3.2.) Initial calibration standards ranging from 0.01 |4,g/
L to 100.0 jig/L were analyzed to evaluate the instrument
response, and the background samples were checked for
fluorescent emissions and interference at low concentrations
of dye. Based on the instrument response and analysis of
the background samples, the RDL was established at 1 ug/
L and the MDL was established at 0.1 |J,g/L. These
threshold limits were sufficiently low to measure the
target dye concentration of 10 |ig/L. The background
samples were stored as described in Section A.2.2.5 for
use as reference checks of background fluorescence.
A.2.2.4 Sample Collection
Frequency and Location
The locations at which samples were collected during the
dye trace study are shown on Figure A-l. Groundwater
grab samples were initially collected from 13 locations in
11 wells, and later from 15 locations in 13 wells after wells
PW3 and PW6 were added to the sampling well network.
WellPW3 was added on February 25,1994, and well PW6
was added on April 27,1994. Wells PW3 and PW6 were
added to the sampling program to obtain additional data
from the deep portion of the aquifer at Site 31. The sample
collection depths are summarized on Table A-1. Samples
were collected from the top of the screened interval in
shallow wells W2, PW1, PW4, PW7, and PW8. Samples
were collected from mid-screen in intermediate wells
PW2, PW5, Wl, and 31OW1. In wells 4MW14 and
31PW1, which have 40-foot (12.2 m) screen lengths,
samples were collected from the top of the screened
interval for the diverging trace study and from the bottom
of the screened interval for the converging trace study.
Wells PW3 and PW6 have 15-foot (4.6 m) screens and are
approximately 105 feet (32.0 m) deep. Samples were
collected from mid-screen at a depth of about 98 feet (29.9
m) bgs. Wells were sampled by increasing order of
anticipated dye concentration, with the anticipated highest
concentration wells sampled last. (This approach
corresponds to sampling the outer perimeter wells first.)
In general, samples were collected from the sampling well
network at a frequency of three times per week on
nonconsecutive days. A summary of the sampling and
analysis plan is presented in Table A-2.
However, shallow wells PW1, PW7, PW8, and 31OW1,
which are all located within 50 feet (15.2 m) of the UVB
system well, were sampled at an increased frequency
during the first week of the dye trace study. The increased
sampling frequency occurred as follows: (1) for the first
day, one sample per hour for the first 8-hour period, one
sample every 2 hours for the second 8-hour period, and one
sample every 4 hours for the third 8-hour period; (2) for the
second day, the wells were sampled once every 8 hours for
a 24-hour period; (3) for the third through fifth days, the
wells were sampled once per day. This increased
frequency was used to monitor potential early dye
movement during the initial period of the study.
The carbon bugs were suspended at the top of the well
screen in shallow wells PW1, PW4, PW7, and PW8 and at
mid-screen for intermediate wells PW2, PW5, Wl, and
31OW1. Bugs were placed at both the top and bottom of
the 40-foot (12.2 m) screens in wells 4MW14 and 31PW1.
The bugs were changed on a weekly basis.
A.2.2.5 Field QA/QC
The field QA/QC program consisted of collecting MS/
MSD samples, equipment rinsate blanks, and trip blanks.
Groundwater grab samples were collected, handled, and
transported in accordance with the QAPP (PRC 1993).
The MS/MSD samples were collected at a frequency of
one pair for every 20 groundwater samples. The
equipment rinsate samples were collected at a frequency
of one for every groundwater grab sampling event. To
minimize the potential for cross contamination between
wells, disposable point-source bailers were used to collect
the groundwater samples from each monitoring well.
Sample integrity requirements outlined in the QAPP (PRC
1993) were followed with additional requirements for
sample storage and holding times. Groundwater samples
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were placed in 250 mL amber bottles and stored in the dark
at 4°C to minimize dye destruction caused by ultraviolet
light. In addition, the samples were analyzed within 14
days of collection, usually on the same day as collection.
A carbon bug trip blank was used to evaluate the potential
for dye contamination introduced in the field or during
transport. The trip blank accompanied the sample carbon
bugs during installation and collection, and the trip blank
was analyzed in the same manner as the sample carbon
bugs.
A.2.3 Analytical Procedures
This section describes the procedures used for qualitative
and quantitative analyses of the samples. Qualitative
analyses included observation of groundwater samples
and of elutriated carbon bugs under visual and ultraviolet
light conditions; quantitative analysis provided a
measurement of dye concentrations using a scanning
spectrofluorometer. All samples were allowed to
equilibrate to the same temperature as the calibration
standards before analysis.
A.2.3.1 Qualitative Analyses
This section describes the qualitative procedures used for
the visual determination of the presence or absence of dye
under ambient light and visual-ultraviolet light conditions.
A.2.3.1.1 Visual - Ambient Light
The presence or absence of dye was first evaluated by
visual examination of each sample. Visual assessment is
possible at low concentrations (about 10 ng/L) of the
selected dyes. A sample aliquot was placed in a clear glass
container and viewed in a uniformly lighted area. A white
backdrop was used to enhance dye identification.
Standards of prepared dye concentrations were used for
comparison.
A.2.3.1.2 Visual - Ultraviolet Light
The presence or absence of dye was further evaluated by
visual examination of each sample under ultraviolet light.
Visual assessment is possible at lower concentrations
(relative to ambient light) under ultraviolet light. The
sample aliquot in the clear glass container was viewed
under long wavelength (365 nanometer [nm]) ultraviolet
light in a darkroom. A dark backdrop was used to enhance
dye identification. Standards of prepared dye
concentrations were used for comparison.
A.2.3.1.3 Carbon Bugs
The carbon bugs were analyzed as backup confirmation of
the presence or absence of dye in the groundwater
samples. The carbon bugs were analyzed by elutriating the
charcoal and looking for the presence of dye on and above
the surface of the charcoal. For this analysis, the charcoal
was placed in clear glass containers and viewed in a dark
room against a dark backdrop. The elutriated charcoal was
viewed under both white light (by shining a focused beam
through the elution) and under ultraviolet light. Because
the carbon bugs accumulate dye over time, very low
concentrations can be detected using this procedure.
For this study, the presence of absorbed dye on the
charcoal was determined using two types of elutriant:
KOH and Smart solutions. The KOH solution consisted of
6 to 7 grams of potassium hydroxide dissolved in 100 mL
of 70 percent isopropyl alcohol. The Smart solution
consisted of 38 percent ammonium hydroxide, 43 percent
1-propanol, and 19 percent distilled water. The solutions
were prepared weekly as needed.
A.2.3.2 Quantitative Analysis
This, section describes the procedures used for quantitative
analysis of groundwater samples to measure dye
concentrations. The type of instrument used is described,
as well as calibration and QA/QC procedures.
A.2.3.2.1 Scanning Spectrofluorometer
A scanning spectrofluorometer was used to measure dye
concentrations in terms of degree of fluorescence. Forthis
study, an Aminco SPF-500 was used. An on-site building
was designated as an analytical laboratory during the
study. A scanning bandwidth separation of 5 nm between
400 and 700 nm was selected for this study. An excitation
bandwidth of 5 nm and an emission bandwidth of 10 nm
were used to produce and measure fluorescent emissions.
The maximum excitation frequency is 490 nm for
fiuorescein and 555 nm for rhodamine WT, and the peak
emission frequency is 520 nm for fiuorescein and 580 nm
for rhodamine WT.
103
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A.2.3.2.2
Calibration Procedures
Calibration ofthespectrofluorometer required preparation
of known concentration solutions of the respective dyes
using distilled water. Concentration steps did not exceed
an order of magnitude and were prepared for the expected
range of sample concentrations. Using dye from the test
lot, a working solution of 100 ug/L was prepared for each
dye in accordance with published procedures (EPA 1988;
Wilson, et al, 1986). From the working solutions, initial
calibration standards were prepared in the following
concentrations: 0.01 ug/L, 0.1 ng/L, 1.0 ng/L, 10.0 ug/L,
and 100.0 jxg/L. Calibration curves were generated for
comparison to sample measurements to obtain the
sample's dye concentration. The temperatures of the
samples and of the calibration standards were allowed to
equilibrate before equipment calibration and subsequent
analysis to minimize potential variations in fluorescent
intensity.
A.2.3.2.3 Laboratory QA/QC
The laboratory QA/QC program included MS/MSD
analyses and continuing calibration checks consisting of
laboratory blanks, laboratory blank spikes, and laboratory
blank spike duplicates. Continuing calibration checks
were run at a frequency of 1 per every 10 samples and at the
end of each sample batch. The continuing calibration
check samples consisted of distilled water and a spike of
both dyes at a concentration of 10 ug/L. The acceptance
criteria was plus or minus 20 percent of the true value. The
dye tracer study plan (PRC 1994a) required instrument
recalibration in the event the calibration verification fell
outside the acceptance criteria. After each batch of
samples was analyzed, calibration of the instrument was
verified by a final calibration check. In the event that the
final calibration check failed to meet the 20 percent
acceptance criteria, the instrument was recalibrated and
any samples analyzed since the previous acceptable
calibration check were reanalyzed. All equipment
calibrations were made at the same sample temperature as
the groundwater samples.
Analytical accuracy was assessed by measuring the
percent recovery (%R) of MS samples. Precision was
measured by comparing the results of the MS sample with
the MSD sample. The calculation of the accuracy and
precision data quality indicators was performed in
accordance with the QAPP for the UVB demonstration
(PRC 1993). There are no established quality assurance
objectives (QAO) for quantitative analysis of dye traces;
however, for this study, Q AOs of 5 0 to 15 0 percent for %R
and 50 percent for relative percent difference (RPD) of MS
and MSD analyses were used (PRC 1994a). These
acceptance criteria are based on similar QAOs established
for organic compounds under EPA's contract laboratory
program.
The frequency of MS/MSD analyses was 1 pair per 20
groundwater samples. Corrective action was implemented
when an analytical error was discovered or the established
acceptance criteria were not met. Corrective actions
included: recalibrating the instrument, reanalyzing the
samples (if within holding time), resampling and
reanalyzing the new samples, evaluating and amending
analytical procedures, or accepting the data with an
acknowledged level of uncertainty.
104
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A.3 Results and Data Interpretation
This section provides a. summary of qualitative and
quantitative analytical results for the dye trace study,
including QA/QC results. An assessment of conformance
with the QAOs is presented by evaluation of %R and RPD.
The data are interpreted by qualitative and quantitative
evaluation methods.
A.3.1 Summary of Results
This section summarizes (1) qualitative and quantitative
results for the background fluorescent study, (2)
qualitative results for the carbon bugs and visual
examination of groundwater grab samples, (3) quantitative
results of spectrofluorometric analysis, and (4) QA/QC
results.
A.3.1.1 Background Results
Grab samples and carbon bugs were collected from select
groundwater monitoring wells before injecting dye into
the aqu'fer. The results of the qualitative and quantitative
analyses of these samples are presented in Table A-3.
These results indicate that there were no detected
interferences from natural or introduced background
fluorescence.
A.3.1.2
Qualitative Results
After dye injection, grab samples of the groundwater were
collected for qualitative analysis with each carbon bug.
The qualitative analysis results were found to be the same
for visual observation of grab samples under ambient and
ultraviolet light and for elution of the carbon bugs. These
results are summarized in Table A-4. The results show
that rhodamine WT was visible in samples from well PW2
for the duration of the study. Rhodamine WT was not
observed in samples from any other wells monitored with
carbon bugs. Fluorescein was visible in samples from the
UVB system well (Wl) for the duration of the study, and
fluorescein was visible in samples from well PW1
beginning April 4, 1994, for the remainder of the study
duration. Quantitative analysis showed that fluorescein
was detected in samples from well PW1 on March 28,
1994 (one week prior to detection by the carbon bugs). It
is believed that dye breakthrough in well P W1 occurred on
March 26 or 27, and that the concentration of dye adsorbed
onto the charcoal at the time of collection on March 28 had
not reached the visible threshold.
Different solutions were used to elute the carbon bugs for
fluorescein and rhodamine WT, as described previously in
Section A.2.3.1.3. Throughout the study period, the
ability of both solutions to release both dyes from the
charcoal was visually compared to contrast the relative
performance of the KOH solution to release rhodamine
WT and of the Smart solution to release fluorescein.
Based on a review of literature, the KOH solution was
expected to be more effective for releasing fluorescein,
and the Smart solution was expected to be more effective
for releasing rhodamine WT. However, no qualitative
difference was observed between the effectiveness of
either solution in releasing either type of dye. Both
solutions worked well for releasing both types of dye.
A.3.1.3
Quantitative Results
The results of quantitative analyses are summarized in
Table A-5. The results show positive determination of
fluorescein in UVB system wells Wl and W2, and in
monitoring wells PW1 and PW3. Rhodamine WT was
detected in wells PW3 and Wl. The samples from all other
wells were below detection limits for both dyes.
Fluorescein was detected in samples from well PW1 on
March 28,1994, the 48th day of the study. The dye was
detected in samples from well PW3 on April 8, 1994, the
59th day of the study. Rhodamine WT was detected in
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deep well PW3 on February 25, 1994, the 17th day of the
study, when the well was sampled for comparison with the
sampling well network results. Wells PW3 and PW6 were
not included with the original sampling locations because
the deep wells were not expected to yield critical results
for evaluation of the circulation cell in the upper portion of
the aquifer. Deep wells PW3 and PW6 were added to the
sampling well network after rhodamine WT was detected
in samples from well PW3. Rhodamine WT was detected
in samples from UVB system well W1 on May 4,1994, the
85th day of the study. The rhodamine WT dye in UVB
system well Wl was detectable only during one other
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A.3.2 Data Quality
The scanning spectrofluorometer was initially calibrated
with five standards of each dye (0.01, 0.10,1.0,10.0, and
100.0 ug/L). Calibration records are included in the
laboratory logbook notes provided in the Technology
Evaluation Report (TER) for UVB SITE demonstration
(PRC 1995). Daily calibrations consisted of an 8-point
curve for fluorescein (1.0, 2.0, 5.0, 8.0, 10.0, 20.0, 50.0,
and 100.0 u.g/L)-and a 5-point curve for rhodamine WT
(1.0, 10.0, 20.0, 50.0, and 100.0 ug/L). Calibration and
continuing calibration checks included blanks, blank
spikes (BS), and blank spike duplicates (BSD).
Continuing calibration checks were performed at a
frequency of 1 per 10 samples and at the end of each
sample batch. Records of continuing calibration checks
also are included in TER (PRC 1995). The results of
continuing calibration checks for both dyes show an
average instrument response difference from true
concentration of 5.4 percent for rhodamine WT and 16.7
percent for fluorescein. These ranges are within the
established acceptable range of 20 percent. The following
calculation was used to measure the instrument response
difference for the continuing calibration checks:
IRD= — X100%
Where:
IRD = Instrument response difference
Crs=Measured concentration in reference standard during
calibration
C^ = Measured concentration in continuing calibration
sample (spiked at the same concentration as reference
standard)
The accuracy and precision of quantitative analysis was
tested by analyzing an MS sample and an MSD sample at
a frequency of 1 per 20 samples. These results are shown
in Tables A-6 and A-7. Due to laboratory error, MS/MSD
analysis did not begin until March 7,1994. On analysis,
matrix interference was found for fluorescein. The
average %R for fluorescein was 245.5 percent, which is
outside the established acceptance range of 50 to 150
percent. The high fluorescein %R range (between 99 and
360 percent) is attributed to either matrix interference in
the groundwater or instrument error, as discussed below.
The %R for rhodamine WT averaged 96.6 percent; none of
the rhodamine WT %R values fell outside the acceptance
range. The RPD for fluorescein was 5.6 percent and was
2.7 percent for rhodamine WT. The RPD for both dyes
was within the established acceptable range of 50 percent
Instrument performance was checked by BS/BSDs. The
%R for fluorescein was found to range between 15 and 170
percent with an average of 83.9. The RPD for fluorescein
was found to range between 0 and 57.1 percent, with an
average of 14.0. The fluorescein %R data for the BS/BSD
fell outside the acceptable range of 50 to 150 percent on 10
occasions; the fluorescein RPD data fell outside the
acceptable range of 50 percent only once. The accuracy
deviations for fluorescein may not be entirely attributed to
instrument performance since the instrument calibration
and continuing calibration checks were within acceptable
limits. In addition, the difference between fluorescein
average %R for MS/MSD (245.5) and BS/BSD (83.9) data
indicates a large influence due to matrix interference.
The rhodamine WT data BS/BSD results show that the %R
ranged between 77 and 110 percent with an average of
96.7, and the RPD ranged between 0 and 22.7 percent with
an average of 2.9. The rhodamine WTBS/BSD data are all
within acceptable limits.
Corrective actions were implemented to identify and
correct the cause for the high fluorescein %R readings.
First, the instrument was recalibrated, and the samples
were reanalyzed. However, no problems were found with
instrument calibration. The sampling and analytical
procedures were evaluated for technical adequacy and to
identify potential deficiencies in the sampling and analysis
program. The program was found to be technically
adequate, and no deficiencies were identified. Therefore,
the accuracy variance is attributed to matrix interference
in the groundwater (possibly from the volatile organic
compound [VOC] contamination). Although background
samples did not show fluorescence from the VOCs in the
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emission range of fluorescein, the reaction of VOCs with
the dye may exaggerate the measured fluorescence.
Therefore, all fluorescein concentration values shown in
Table A-5 are considered estimated due to matrix
interference. The matrix interference does not affect any
of the study goals since all the primary and secondary
goals are based on detection of the presence or absence of
dye rather than accurate measurement of dye concentration.
A.3.3 Data Interpretation
This section presents the results of the dye trace study. An
overview of the hydrogeologic conditions affecting the
dye trace study results is provided in Section A.3.3.1.
Interpretation of the qualitative and quantitative results of
the dye trace study is addressed in Section A.3.3.2.
A.3.3.1 Hydrogeologic Conditions
Data collected during the dye trace study indicate that
hydrogeologic conditions at Site 31 exert a controlling
influence over the movement of groundwater and likely
the subsequent distribution of dye during the dye trace
study. The primary hydrogeologic factors affecting the
dye trace study results are groundwater flow direction and
anisotropy and heterogeneity of the aquifer.
A.3.3.1.1
Groundwater Flow Direction
The downgradient direction of groundwater flow was
originally determined to be to the southeast based on a
preliminary contour map of the November 1992
groundwater elevations at Site 31 (TETC 1994). This flow
direction corresponds to the general groundwater gradient
over the majority of the base, gently sloping to the
southeast. After heavy rains during the winter of 1992-93,
an apparent change in groundwater flow direction was
observed at the site (TETC 1994). This change was
interpreted to be in response to recharge along Heacock
Storm Drain, located along the eastern boundary ofthe
base. Recharge from the storm drain appears to have
caused localized groundwater mounding, which in turn
locally affects the direction of groundwater flow. The
mounding of groundwater in response to the recharge
appears to have temporarily redirected the groundwater
flow toward the west-southwest along the eastern portion
ofthe base, which includes Site 31. However, wells west
of Site 31 appear not to have been affected by groundwater
recharge from Heacock Storm Drain, and data from these
wells continue to indicate a groundwater flow direction to
the southeast.
Groundwater level elevations were collected before and
during the UVB demonstration. Based on contouring of
the groundwater elevations, the potentiometric surface
appears relatively flat with generally less than 1 foot (0.3
m) change of gradient across the entire area of Site 31. Due
to the relatively flat gradient and the linear distribution of
groundwater monitoring wells at the site, the groundwater
flow direction could not be precisely determined.
However, groundwater levels measured during operation
ofthe UVB system suggest that wells PW1 through'PW6
are downgradient (southeast) of the treatment system.
Since startup of the UVB system, additional wells
screened across the groundwater table have been installed
in the immediate vicinity ofthe treatment system. These
additional wells will allow an accurate measurement ofthe
groundwater gradient once the UVB system has been shut
down. The UVB system was turned off on December 4,
1994 and the groundwater elevation was subsequently
measured over a 7-day period until the measurements
stabilized. The results ofthe December 9 measurements
indicate that groundwater flow is to the southeast.
Modeling of groundwater flow at March AFB by Tetra
Tech, Inc., suggests that the site is located at the
convergence of the two flow directions (PRC 1994c). This
convergence appears to have caused a trough in the
groundwater gradient. Several interpretations for the
change in gradient direction at the site have been proposed,
including shallow bedrock and structural discontinuity
(PRC 1994c). However, boring log data from the site
suggest that the depth to weathered bedrock on site
averages 100 feet or more, it is unlikely that bedrock
topography has significantly affected the groundwater
gradient direction at the site. In addition, more recent data
show that temporary changes in groundwater flow
direction may result from precipitation and subsequent
recharge.
A.3.3.1.2 Anisotropy and Heterogeneity
In addition to the natural groundwater gradient direction,
the anisotropy and heterogeneity of the aquifer plays a
significant roll in controlling the movement of
groundwater and subsequent distribution of dye. These
factors are magnified especially when an induced flow,
such as the UVB circulation cell, is placed on the aquifer.
Induced groundwater flow resulting from the UVB system
is influenced by the anisotropy and heterogeneity of the
116
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aquifer and locally may not flow in the normal
downgradient flow direction.
Since the aquifer consists of alluvial deposits, anisotropic
conditions are likely present. The value of Kh at the site is
estimated to be an order of magnitude greater than Kv
(TETC 1994). In addition to anisotropic conditions in the
alluvial deposits, structural controls, such as fractures and
faults, may significantly affect groundwater flow in the
aquifer.
During the UVB demonstration, a seismic reflection
survey was conducted at Site 31 by Tetra Tech, Inc. Afault
was interpreted from the reflection data at a depth of about
100 feet (30.5 m) bgs trending northwest/southeast,
parallel to Graeber Street (Figure A-l). The trend of this
feature roughly parallels the downgradient direction and
may influence groundwater flow. The specific effects
caused by this feature were not investigated during the dye
trace study. Additional information concerning the
identified feature can be found in the seismic reflection
survey prepared by Tetra Tech, Inc. (1993).
Recent unpublished geophysical investigative results
from March AFB support the presence of a fault at the base
(PRC 1994b). Preliminary data from this investigation
appear to correlate with the seismic reflection survey
conducted at Site 31 by Tetra Tech, Inc. This correlation
suggests that a well-developed fracture zone parallel to
Graeber Street (southeast trending) may be present. If
present, this fault could provide a preferential conduit for
groundwater flow. An interpreted zone of higher
conductivity is currently being used by Tetra Tech, Inc.,
for its base-wide groundwater modeling and appears to
provide the best match for the observed groundwater data
collected at the base (PRC 1994c). This interpretation may
also explain the observed distribution of rhodamine WT
and fluorescein during the dye trace study. A detailed
discussion of the interpreted linear discontinuity and site
anisotropy and heterogeneity is provided in the ITER
A.3.3.2 Interpretation of Dye Trace
Study Results
The results of the dye trace study provide both qualitative
and quantitative information. This information provides
data that are used to demonstrate the hydraulic
interconnection between the UVB system and wells PW1,
PW2, and PW3, calculate aquifer characteristics and
groundwater velocities, and estimate of the radius of
circulation cell of the UVB circulation cell.
A.3.3.2.1 Interconnection of
Groundwater Flow
The presence of fluorescein dye in samples from wells
PW1 and PW3 shows interconnection between these
points and UVB system well W2. Likewise, the presence
of rhodamine WT in samples from well PW3 shows
interconnection with well PW2. The presence of
rhodamine WT hi samples from UVB system well Wl
indicates that a circulation cell has developed between the
UVB system and well PW2. The absence of dye in any of
the surrounding wells, however, suggests that groundwater
movement is in the southwest direction, downgradient,
rather than within a well developed, symmetrical
circulation cell around the system.
The absence of rhodamine WT in samples from well PW1
and the absence of fluorescein in samples from well PW2
indicates an uneven distribution of dye within the UVB
circulation cell. The uneven distribution of dye may
reflect different flow regimes due to heterogeneous,
anisotropic deposits, or the linear discontinuity discussed
above. The screened intervals of wells Wl, PW2, and
PW5 are in well-graded, fine to coarse sand with little fine
to medium gravel and no silt or clay-sized particles. The
over- and underlying intervals are finer sands with some
silt. The lack of dye mixing within the screened intervals
of wells PW1 and PW2 may be due to variable litho logics
in the aquifer system. The presence of both dyes in
samples from well PW3 indicates that the flow regimes
mix in the deeper interval. Because fluorescein was
detected in samples from well PW1 but not in samples
from well PW2, the fluorescein probably mixes into the
deeper interval between the UVB system and well PW1.
The mixing phenomenon in the deeper interval may be due
to the specific gravity of the dyes (fluorescein = 1.050,
rhodamine WT - 1.19). Because the dyes are slightly
heavier than water, they may tend to sink under Site 31
conditions. Also, because of the lack of dye mixing in well
PW2 (and the presence of rhodamine WT in UVB system
well Wl), UVB system well Wl appears to draw water
from the intermediate interval, but not from the upper
interval. The study results do not indicate whether
groundwater is drawn from the deeper interval.
Fluorescein breakthrough from UVB system well W2 to
well Wl occurred within 24 hours after dye injection,
117
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indicating a high degree of groundwater circulation within
the system (Figure A-2). The concentration of dye in
samples from UVB system well Wl continued to increase
over the next 14 days until equilibrium was reached
between the UVB system wells (Wl and W2). Using an
estimated Kv of approximately 9.05 gpd/ft2 (1.40 x 10'5
feet per second; 4.26 x 10"4 cm/s) (one order of magnitude
less than Kh), it is unlikely that fiuorescein dye traveled a
minimum distance of approximately 8.8 feet (2.7 m)
vertically through the saturated sediments between wells
Wl and W2 within 24 hours. This suggests that a
preferential pathway of groundwater flow likely exists.
Three potential preferential pathways were identified:
bridging of grout during well completion, leakage around
the packer, and conduits of flow in the aquifer.
Review of well completion logs suggests that during
grouting an adequate seal was emplaced between the two
well screens. However, it is possible that conduits in the
seal (bridging) may have occurred during emplacement of
the bentonite chips. The packer used to separate the upper
and lower screen intervals consisted of an inflatable rubber
tire with a hole in the center of the steel rim to house the
educter pipe. The seal between the steel rim and educter
pipe is loose to allow the internal components of the UVB
system to move freely within the treatment well. This seal
is a likely source of groundwater recirculation. The third
possible source of groundwater recirculation is from
effects of the interpreted fault. Conduits of flow, such as
fractures, may be associated with the fault. These conduits
may be continuous between the upper and lower screened
sections of the UVB system well, causing a high degree of
groundwater circulation to occur.
A.3.3.2,2
Groundwater Velocities
The groundwater maximum velocity was estimated by
dividing the horizontal distance between the injection and
sampling point by the first arrival time of the dye at the
sampling point. Dye breakthrough curves were drawn to
estimate first arrival and maximum concentration times
and to show the decline of dye concentration in the
injection wells (Figures A-2, A-3, and A-4). The dye
breakthrough curves shown on Figures A-3 and A-4 do not
display typical bell-shaped patterns. The shape of the
curves may reflect the nature of groundwater flow in the
porous aquifer (rather than channelized or conduit flow),
or the curves may become more typical with an extended
monitoring period. (The dye concentration hi well PW1
was rising at the end of the study period.)
Fiuorescein breakthrough in well PW1 is shown on Figure
A-3. The breakthrough occurred between March 25,1994
(concentration < 1 ug/L) and March 28, 1994
(concentration = 230 ug/L). Based on a travel time of 46
to 47 days and the distance between wells W2 and PW1
(35.18 feet [10.7m]), an estimate of the maximum
groundwater velocity is between 0.75 and 0.76 feet per day
(feet/day) (2.65 x 10"* and 1.68 x 10"4 cm/s). Based on the
shape of the breakthrough curve, the travel time for
maximum concentration is believed to extend beyond the
monitoring period of the study. Because the average
groundwater velocity is calculated based on the travel time
for the maximum dye concentration, the average
groundwater velocity was not estimated. The maximum
concentration travel time may be prolonged due to the
recirculation within the UyB system between wells W2
and Wl, as indicated on Figure A-2.
The breakthrough curves shown on Figure A-4 represent
fiuorescein and rhodamine WT concentrations in samples
from well PW3. Because rhodamine WT was found in
samples from well PW3 on the first sampling event
(February 25, 1994), these data were not used to estimate
first tune of arrival. The appearance of fiuorescein in well
PW3 on April 8,1994, however, confirmed the maximum
groundwater velocity estimate provided by sample results
from well PW1 (45.3 feet/59 days = 0.77 feet/day [13.8 m/
59 days = 0.2339 m/day or 2.72 x 10"4 cm/s]). The graphs
of dye concentrations in samples from well PW3 appear to
have leveled off, but the concentrations did not appear to
be declining at the end of the monitoring period.
Therefore, the well PW3 data do not provide a firm
estimate of the maximum concentration time or the
average groundwater velocity.
A.3.3.2.3
Radius of Circulation Cell
The results show that an elongated circulation cell
developed between wells Wl and PW2 over a distance of
about 40 feet (12.2 m). Hydraulic interconnection was
demonstrated between wells W2 and PW3 over a distance
of about 45 feet (13.7 m); however, the results do not
indicate whether this interconnection is primarily due to
UVB system circulation or to groundwater flow in the
downgradient direction. The absence of dye in wells other
than those installed in the downgradient direction
(southeast) shows that the circulation cell developed less
than 40 feet (12.2 m) in all other directions. Furthermore,
the results may indicate that the circulation cell did not
develop at all hi the other directions. Thus, the area of
118
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I
=
120
-------
3
5 P,
«•> r:
I
1
J-
(i9jTi/sHHMSojK>pi)
HAQ
ii u
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121
-------
influence of the UVB circulation cell was shown to be at
least 40 feet (12.2 m) in the downgradient (southeast)
direction and less than 40 feet (12.2 m) in all other
directions.
122
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A.4 Conclusions
This section presents the conclusions regarding the
primary and secondary goals.
Primary Goals (PG)
• PG-1: Demonstrate hydraulic interconnection between
the UVB system and distant sample locations
This goal was achieved by analyzing passive receptors and
groundwater samples for fluorescein and rhodamine WT
from wells Wl, W2, PW1, PW2, PW3, PW4, PW5, PW6,
PW7, PW8 31OW1, 31PW1, and 4MW14. The results
show interconnection between the UVB system and wells
PW1, PW2, and PW3. These wells are believed to be
downgradient of the UVB system. The results show the
presence of a short-circuit circulation pattern between
wells W2 and Wl, and an elongated circulation cell
between the UVB system and wells PW1, PW2, and PW3.
Although dye was not detected in the outer cluster wells
(PW4, PW5, and PW6) during the study period, it is
believed that dye movement will follow natural
groundwater flow in the downgradient direction toward
the outer cluster wells. However, dye was not visibly
apparent in the outer cluster wells on February 1 and 2,
1995.
• PG-2: Demonstrate circulation of groundwater
within the UVB circulation cell
Confirmation of hydraulic interconnection between the
UVB system and wells PW1, PW2, and PW3 shows that
the UVB system is producing an elongated circulation
pattern in a downgradient direction. Circulation of the
groundwater within the UVB system was verified by the
detection of fluorescein in samples from well PW1 and of
rhodamine WT in samples from UVB system well Wl.
There is no indication, however, of a well-developed
circulation cell between the UVB system and remote wells
that are not downgradient of the system. The uneven
distribution of dye within the aquifer suggests different
flow regimes in heterogenous, anisotropic deposits.
Based on the dye trace study results, it appears that a
narrow and elongated circulation cell may have developed
to a distance of at least 40 feet (12.2 m) in a downgradient
direction and less than 40 feet (12.2 m) hi all other
directions. However, the mixing aspect of the circulation
cell does not appear to be well developed. In addition, the
movement of the groundwater appears to be driven in a
downgradient direction, rather than within a well-
developed circulation cell.
Secondary Goals (SG)
• SG-1: Estimate maximum and average groundwater
velocities produced by the UVB system
The maximum groundwater velocity was calculated
between wells W2 and PW1 and between wells W2 and
PW3. The average groundwater velocity could not be
calculated because the maximum dye concentration peak
did not occur during the study period. The prolonged
period of dye breakthrough is probably due to attenuation
of the dye in the aquifer. Dye breakthrough occurred
between wells W2 and PW1 (a distance of 35.18 feet [10.7
m]) in 46 or 47 days. The maximum groundwater velocity
is thus calculated to be between 0.75 and 0.76 feet/day
(2.65 x 10-4 and 2.68 x 10"4 cm/s). Dye breakthrough
between wells W2 and PW3 confirms the maximum
groundwater velocity estimate. Themaximum groundwater
velocity between W2 and PW3 (a distance of 45.30 [13.8
m] feet in 59 days) is 0.77 feet/day (2.72 x 10"4 cm/s).
• SG-2: Quantify selected aquifer characteristics
The hydraulic conductivity between wells W2 and PW1
(Khl) and between wells W2 and PW3 (Kh2) is calculated
in the following equation:
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ve
K= —
Where;
K = hydraulic conductivity
v =» groundwater velocity (0.75 and 0.77 feet/day [2.65 x
10"1 and 2.72 x 10^ cm/s] from SG-1)
e « formation porosity (25 percent [TETC 1994])
i ** hydraulic gradient (0.014 April 1993 average gradient
[TETC 1994])
For wells W2 and PW1:
1^, = (0.75 feet/day [2.65 x 1Q-4 cm/s])(0.25)/(0.014)
K,,, = 13.39 feet/day or 100.4 gpd/ft2 (4.72 x 10'3 cm/s)
For wells W2 and PW3:
KM = (0.77 feet/day [2.72 x 10"4 cm/s])(0.25)/(0.014)
13.75 feet/day or 103.1 gpd/ft2 (4.85 x 10'3 cm/s)
These measured values are only slightly higher than the
previously calculated average site Kh value of 90.5 gpd/ft2
(4.26 x 10'3 cm/s) (TETC 1993), and the measured values
compare favorably within the same order of magnitude
estimate. The higher conductivity value obtained in this
study may reflect preferential flow in the downgradient
direction. An estimate of the aquifer transmissivity is
calculated for a saturated thickness of 75 feet (22.9 m)
using the following equation:
Where:
T = transmissivity
K> hydraulic conductivity (100.4 and 103.1 gpd/ft2 [4.72
x 10-J and 4.85 x 1 0'3 cm/s] from SG-2)
b <= saturated thickness (75 feet [22.9 m])
For wells W2 and PW1:
T = (1 00.4 gpd/ft2 [4.72 x 10's m/s])(75 feet [22.9 m])
T = 7,530 gpd/ft (1 .08 x 1 O'3 m2/s)
For wells W2 and PW3:
T« (103.1 gpd/ft2 [4.85 x 10'5 m/s])(75 feet [22.9 m])
T = 7,732.5 gpd/ft (1 .1 1 x 10"3 ma/s)
These estimates are close to the previous calculations
average site value of 6,800 gpd/ft (9.75 x 10"4 m2/s) (TETC
1993). The previous estimates based on the pump test of
well 31OW1 may reflect the average transmissivity of the
aquifer. The estimates obtained under the dye trace study
may reflect preferential flow in the downgradient
direction.
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A.5 References
PRC Environmental Management, Inc. (PRC). 1993.
Final Quality Assurance Project Plan for the
Superfund Innovative Technology Evaluation
Demonstration of the Roy F. Weston, Inc.,
Unterdruck-Verdampfer-Brunnen (UVB) Technology.
April.
PRC Environmental Management, Inc. (PRC). 1994a.
"Dye Tracer Study Plan." Amendment to the Final
Quality Assurance Project Plan, Roy F. Weston, Inc.,
Unterdruck-Verdampfer-Brunnen (UVB) Technology
Site Demonstration at March Air Force Base,
California. Februarys.
PRC. 1994b. Record of Telephone Conversation
Regarding Seismic Surveys at March Air Force Base,
California. Between Mr. Ben Hough, PRC, and Mr.
Walter Grinyer, IT Corporation. November 2.
PRC. 1994c. Record of Telephone Conversation
Regarding Ground-water Flow Modeling at March Air
Force Base, California. Between Mr. Ben Hough,
PRC and Mr. Bob Jons, Tetra Tech, Inc. November 2.
PRC. 1995. "Draft Technology Evaluation Report
(TER), Roy F. Weston, Inc., Unterdruck-Verdampfer-
Brunnen (UVB) Technology SITE Demonstration at
March Air Force Base, California." January 27.
Tetra Tech, Inc. 1993. "Seismic Reflection Survey,"
Sites 2, 27, and 31, March Air Force Base, Riverside
County, California. Draft Report Prepared by
NORCAL Geophysical Consultants, Inc. August 4.
The Earth Technologies Corporation (TETC). 1993.
"March AFB IRP Site 31 Aquifer Testing." Draft
Report.
TETC. 1994. "Draft Final Remedial Investigation/
Feasibility Study Report For Operable Unit 1, March
Air Force Base, California." March.
U.S. Environmental Protection Agency (EPA). 1988.
Application of Dye-Tracing Techniques for
Determining Solute Transport Characteristics of
Groundwater in Karst Terrains. EPA 904/6-88-001.
EPA. 1991. Groundwater Handbook, Volume II:
Methodology. EPA/625/6-90/016b.
Wilson, Jr., J. P., E. D. Cobb, and F. A. Kilpatrick. 1986.
Fluorometric Procedure for Dye Tracing (Revised).
U.S. Geological Survey. Techniques of Water-
Resources Investigation. TWI3-A12.
125
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Appendix AA
Estimation of Aquifer Characteristics
The MARCH AFB. SITE 31. AQUIFER TESTING
(TETC 1993) report contained data for a pumping test in
observation well 31OW1. Well 31OW1 was pumped at a
constant rate of 8 gallons per minute (gpm) (30.3 liters per
minute). After 1,212 minutes of pumping, well 31OW1
went dry at approximately 32 feet (9.8 meters) of
drawdown. Within that time frame, identifiable
drawdown was observed in adjacent wells 31PW1 (50 feet
(15.2 meters) north of the pumped well) and 4MW14
(almost 64 feet (19.5 meters) northwest of the pumped
well).
Using the hydrogeologic parameters from the pump test
conducted at Site 31 and the distance-drawdown method,
the radius of circulation cell was estimated to be about 60
feet (18.3 meters). The distance-drawdown method is a
modification of the Jacob straight line method to
determine the distance at which a pumping well does not
affect the water level. This method is based on the Theis
equation and is valid for long pumping times and nearby
wells.
The distance-drawdown method averages the differences
of hydraulic conductivity measured in the wells due to
aquifer anisotropy and provides an estimate of the radius
of circulation cell under average conditions in the aquifer.
A distance-drawdown plot was drawn based on drawdown
and recovery data from the pump test of well 31OW1 and
using wells 4MW14 and 31PW1 as observation wells
(TETC 1993). Using the distance-drawdown method, the
observed drawdown was plotted on an arithmetic scale
with distance plotted on a logarithmic scale. A best fit
straight line was drawn through the data points until it
intercepted the zero drawdown line. The 60-foot (18.3-
meter) estimate is considered approximate due to
variations in the observed drawdown data caused by
aquifer anisotropy.
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Appendix AB
Dye Concentration Calculations
The equation for calculation of dye volume is: Assume only 1 percent is recovered: 100 x dye volume :
5.7 gallons (21. 6 liters)
Dye Volume=
(Final ConcenfaationTWater Volume to be Dyed")
(Dye Concentration)(Dye Specific Gravity)
Assume volume of water to be dyed is 60.000 cubic feet
(ft3) (1,699.2 cubic meters).
60,000 ft3 x 7.48 gallons/ft3=448.800 gallons
(1,699.2 cubic meters x 1,000 liters per cubic meter=
1,699,200 liters)
Assume final concentration is 10 micrograms per liter=
1 X 10-8
The specific gravity of rhodamine WT, 20 percent
solution, is 1.19; the specific gravity of fluorescein, 7.5
percent solution, is 1.050.
For rhodamine WT, 20 percent solution:
Dye Volume=
(I x 10-g¥448.800 gallons Fl. 699.200 litersT>
0.0189 gallons (0.0714 liters)
Assume only 1 percent is recovered; 100 x dye volume =
1.89 gallons (7. lliters)
For fluorescein, 7.5 percent solution:
Dye Volume=
(1 x 10-gV448.800 gallons n.699.200 liters^ _
(0.075)(1.050)
0.0570 gallons (0.2158 liters)
127
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Appendix B1
In Situ Groundwater Remediation: Pilot Study of the UVB-Vacuum
Vaporizer Well, March Air Force Base, Cal fornia
128
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95-WP103.05
INTRODUCTION -
The Unterdruck-Verdampfer-Brunnen (UVB) technology (roughly translated to Vacuum Vaporizer Well)
is an in-situ system for ground-water remediation, particularly for aquifers contaminated with volatile
organic compounds (VOC). The UVB system was developed and patented by DsG mbH, Reutlingen,
Germany, and is now being demonstrated and used in the United States.
In conjunction with the technology developer (EEG Technologies Corporation), Roy F. Weston, Inc.
(WES-TON) has completed an 18-month demonstration program of the UVB system at March Air Force
Base (AFB), Riverside, California under subcontract to Black & Veatch Waste Science, Inc. The system
has been demonstrated for March AFB, the U.S. Environmental Protection Agency, Office of Research
and Development (USEPA ORD) under the Superfund Innovative Technology Evaluation (SITE)
Program, and the U.S. Army Corps of Engineers, Omaha District who is administering the innovative
technology program for March AFB. This is the first application of the UVB system at a federal facility.
STUDY OBJECTIVES
March AFB is committed to the testing of innovative technologies for remediation of contaminants found
on the base. The primary objective of the study was to evaluate the feasibility of the UVB system for
removal of chlorinated hydrocarbons (primarily trichloroethene (TCE)) from the groundwater, and to
evaluate cost effectiveness of the treatment.
SITE DESCRIPTION
March AFB. is located east of the City of Riverside, Riverside County, California, approximately 60 miles
east of Los Angeles. The study was conducted at Site 31 (Unconfirmed Solvent Disposal), Operable
Unit 1 (Figure 1).
Site 31 is underlain by fine-grained sediment dominated by fine-grained sand and silt As is typical of
alluvial and fluvial deposits, individual lithologic units tend not to be laterally continuous. Based on
lithologic logs available from this and previous site studies, the following generalized alluvial sequence
underlies Site 31: fine sandy silt to clayey silt and silty fine sand to depths of about 40-50 feet below
ground surface (bgs); relatively continuous interval of clean sand (i.e., containing few fines) to about 50-
60 feet bgs; interbedded silt, sand and minor clay extending to weathered granitic basement rock.
The first occurrence of saturated soil is reported in most boring logs between approximately 45-55' feet
bgs. Dry to slightly moist conditions were reported between approximately 100-120 feet bgs in 31MW1.
This fine-grained interval is considered a barrier to the vertical flow of groundwater in this location and,
at least locally, appears to separate the alluvial aquifer into two zones. This interpretation is further
supported by a groundwater elevation head differential between 31MW1 and adjacent 4MW14 of
approximately 4.5 feet. The depth to weathered granitic basement rock is irregular, ranging from
approximately 30-160 feet bgs across the site.
The hydrogeologic conditions at Site 31 are fairly complex and hydraulic parameters appear to vary
widely in both vertical and horizontal directions. Depth to groundwater in developed wells is
approximately 40 feet bgs. Groundwater flow direction across the site is predominately toward the south
at an average gradient of approximately 0.007 feet/foot. Based on aquifer test results conducted on
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! 95-WP103.05
•monitoring wells 3IOWI and 31PWI, the following average hydraulic parameters are calculated (Earth
Technologies Corporation, 1994):
i
• Hydraulic conductivity (k) 90.5 gpd/ft2 (average Site 31 value)
Hydraulic gradient (i) 0.007 (December 1994 average condition)
• Effective porosity (nj 27.2%
« Transport velocity (V) 0.31 ft/day
i
TECHNOLOGY DESCRIPTION
n
i
The UVB technology uses a system of chemical, physical, and biological processes to treat VOC-
contaminated groundwater and subsurface soils. The UVB system consists of a specially adapted
groundwater treatment well, a negative pressure stripping reactor, an aboveground vacuum extraction
blower, and an off-gas treatment system if necessary (e.g., activated carbon adsorption units)(Figure 2).
The UVB treatment well is constructed with two screened zones: one section which is placed at the
bottom of the treatment interval, and one section which straddles the groundwater interface. The
borehole annulus between the two screened zones is sealed with bentonite. A packer is installed in the
treatment well between the two screened zones to ensure one directional flow of the groundwater through
the treatment well. A pipe is placed through the packer and connected to a pump which provides
groundwater from the lower zone to the upper zone where the stripper reactor is situated. The upper end
of the pipe terminates at the reactor.
«
The upper, closed part of the well, is maintained at below atmospheric pressure by a centrifugal blower.
The air for the in-situ stripping is drawn in through a 3-inch diameter fresh air pipe: the upper end is
open to the atmosphere, and the lower end terminates in a pinhole plate (diffuser) located hi the reactor.
Soil air is also drawn into the treatment well from the vadose zone through the upper well screen. The
negative pressure within the upper part of the well also causes a water level rise within the treatment
well.
i
The stripper reactor is balanced below the groundwater level within the treatment well and is free-
floating to allow for changing water levels. The location of the reactor with respect to the water level
hi the well determines the ratio of air that is drawn from the atmosphere through the ah* intake pipe, to
the air that is drawn into the well from the vadose zone through the upper screen! This also controls the
air to water ratio within the stripper reactor since only the air drawn from the surface through the air
intake pipe is directed to the pinhole plate in the stripper reactor. Balancing of the system within the
well is achieved by installing buoyancy tanks below the pump.
|
The zone within the well between the pinhole plate and the water surface is the stripping zone, in which
an air bubble flow develops and strips VOCs from the groundwater. The rising air bubbles produce an
ak lift pumping effect, which moves the water, and causes a suction effect at the bottom of the well.
Stripped ah* from the groundwater, and extracted soil gas, is transported up through the casing and
blower, for treatment, if necessary, before venting to the atmosphere.
The upward-streaming, stripped groundwater leaves the well casing through the upper screen section of
the treatment well. The mass of flowing groundwater leaving the upper screen is counterbalanced by
the flow of groundwater toward the lower screened section, thereby setting up a three-dimensional
groundwater circulation cell around the UVB well. Contaminated groundwater flows toward the well
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95-WP10305
.through the lower screen and is moved up in the treatment well to the stripping zone by the action of
the pump as well as the air lift effect. The water is stripped of VOCs, and is returned to the grouridwater
flow regime through the upper screen. The artificial groundwater circulation cell established by the UVB
system is superimposed over the natural groundwater flow surface, and results in a three-dimensional
flow regime around the UVB well.
Treatment Well Construction
Prior to installation of the UVB treatment well, a pilot soil boring was installed using the dual-tube
percussion drill rig to a depth of 1 18.5 ft bgs to collect soil samples and obtain Uthologic information.
The pilot boring was partially sealed with bentonite Upon completion. The UVB treatment well was then
drilled at the location of the pilot boring to a total depth of 87.5 feet using a 26 inch bucket-auger drill
rig.
Figure 2 shows the construction details of the UVB treatment well. The well is 16 inches in
and consists of two screened sections separated by blank mild steel casing. The lower (influent) screen
section is comprised of 12 ft of steel bridge-slot casing, while the upper (effluent) screen section is
comprised of three feet of bridge-slot casing with an additional 12 ft of double-cased stainless steel
screen which is filled with 3/8-inch Teflon beads.
Within the annulus of the borehole, three 2-inch PVC monitoring wells with stainless steel screens were
installed. One well (Wl) is screened at approximately the same interval as the influent portion of the
treatment well, to allow collection of groundwater samples specific to the influent portion of the
treatment cell. The two remaining monitoring wells within the annulus (W2 and W3) are both screened
between 40-55 feet bgs. These wells were installed to allow collection of groundwater samples specific
to the effluent portion of the treatment well. Wells W2 and W3 were installed at the same depths and
at 180° from each other.
Treatment Well Internal Components
Virtually all of the down-hole components of the UVB treatment well including the double-wall stripper
reactor, pinhole (diffuser) plate, internal centralizers, and piping are made of high density polyethylene
(HOPE), with the. exception, of the upper 40 feet of the 3-inch diameter fresh air intake pipe, which is
made of aluminum. The use of HOPE minimizes the number of metal pieces mat would corrode while
being submerged in groundwater over extended periods of time.
The pump used in the UVB treatment well is a Grundfos KP 300 MI submersible pump equipped with
a 1 5 mm orifice flow restrictor to provide a consistent upward flow within the well. The calculated
pump rate is approximately 22 gpm. The entire set of UVB down-hole components (except for the
packer) is free-floating and can adjust to fluctuations in groundwater elevations.
Aboveground Treatment System Components
Figure 3 shows the layout of the aboveground UVB system installed at Site 31. The entire system is
enclosed by a chain-link fence equipped with a locking gate. The blower is located adjacent to the UVB
well-head and the suction side of this blower is connected to the 16-inch well casing via a 4-inch HDPE
pipe to create a vacuum in the casing. The blower is mounted on a moisture knockout drum. No
accumulation of liquid has occurred during the study. Four-inch diameter PVC pipe is used to connect
the discharge side of the blower to two 1800-Ib vapor phase carbon canisters. Four sampling/monitoring
ports (VI through V4) are installed within the aboveground airstream piping network (Figure 3).
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"CAPTURE ZONE" COMPUTATION
The UVB creates a complex, three-dimensional ground-water circulation cell with a flow pattern having
a vertical component in addition to horizontal flow. The UVB "capture zone" and size of the three-
dimensional groundwater circulation cell have been estimated using equations and graphical solutions
developed over several years by Dr. Bruno Herrling of the Groundwater Research Group,
Hydromechanics Institute, University of Karlsruhe, Germany. A discussion of the geometry created
around a UVB and the assumptions used in the model is provided in Herrling, et al. (1991).
Based on the following hydraulic parameters and well specifications, the upstream and downstream
stagnation points, the distances BB and BT and cross-sectional UVB "capture zone" area, and the spacing
requirements for additional UVB's have been estimated.
ii
i = 0.007 (hydraulic gradient)
ka » 4.3xlO*5 m/s (horizontal hydraulic conductivity)
kv «• 4.3x10"* m/s (vertical hydraulic conductivity)
V * 3xlO"7 m/s (Darcian velocity)
H - 13.72m (thickness of treatment zone)
Q » 5 mVhr (discharge through the UVB)
aT = 4.2 m (length of upper screen section)
% = 3.6m (length of lower screen section)
,i
Using the corresponding dimensioning diagrams from Herrling et al., the following values were obtained
for the UVB at Site 31:
i
S — 34.3m (112 ft) (distance to the upstream and downstream stagnation points
from the well axis)
BT s 27.4m (90 ft.) (capture width at the top of the aquifer)
BB = 106.3m (349 ft.) (capture width at the bottom of the aquifer)
A = 1,176m2 (12,660 ft2) (cross sectional area of UVB "capture zone")
D ^ 72m (236 ft.) (predicted spacing distance between UVBs for most
efficient plume capture)
i
The width at the top and bottom of the capture zone is calculated for a distance five times the stagnation
point upstream of the UVB. In plan view, the radial distance of the circulation cell perpendicular to flow
is calculated using the equation BT+BB/4. This equation yields a plan view radial distance for the
circulation cell of approximately 110 feet The result of this analysis is shown on Figure 4.
!
MONITORING AND SAMPLING PROGRAM
j
The monitoring and sampling program designed to generate data necessary for evaluating the treatment
effectiveness consisted of the following major elements:
• Pilot boring and soil sampling.
• Baseline (pre-startup) groundwater sampling."
• Operational monitoring.
Air monitoring and sampling.
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95-WP103.05
Treatment well groundwater sampling.
Perimeter wells groundwater sampling.
Sampling and analytical procedures were performed following stringent methods outlined in the Quality
Assurance/Quality Control Plan and Sampling and Analysis Plan developed and approved for this project.
Pilot Boring and Soil Sampling
The pilot boring was drilled using a dual-tube percussion drill rig equipped with a down-hole hammer
and California-modified split-spoon samplers. Soil samples were "collected virtually continuously for the
following objectives:
• Geotechnical analysis.
• Chemical analysis.
• Microbiological analysis.
• Lithoiogic description and field screening.
Baseline Groundwater Sampling
Groundwater samples were collected prior to system startup from wells scheduled to be used for the
long-term monitoring to establish baseline chemical conditions. A wide range of chemical analyses were
performed including VOC, metals, general minerals and water quality parameters. Baseline samples were
not collected from 31PWI, PW7, or PW8 which were added to the monitoring network after startup.
Operational Monitoring
The 18-month operational monitoring consisted of air monitoring and sampling, treatment well
groundwater sampling, and perimeter wells groundwater sampling.
Air Monitoring and Sampling. The primary objectives of the air monitoring, sampling and analysis
program were to monitor the system operating parameters, to evaluate the removal rates of VOC's from
the groundwater, and to evaluate the efficiency of the off-gas treatment units. This consisted of
recording air flow parameters including linear flow velocity, relative humidity, temperature,
vacuum/pressure, and relative VOC concentrations at the air intake pipe and at four ports installed in the
above-ground airstream piping. Air samples were also collected primarily from port V2 and V3 (Figure
3) for laboratory analysis of VOC concentrations.
Treatment Well Groundwater Sampling. Groundwater samples were collected frequently
(approximately 165 rounds) from the two-inch diameter monitoring wells affixed to the UVB treatment
well. Concentrations in these wells (Wl and W3) are considered to represent the influent and effluent
groundwater conditions, respectively. Initially, sampling frequency was very rapid at startup, reducing
to twice per week months 2-6, and finally to biweekly for the following 12 months.
Analysis consisted of VOC's on every sample, as well as six rounds for alkalinity, nitrogen, phosphate,
BOD, COD and carbon dioxide, and three rounds for microbiological analysis. Field parameters
(temperature, specific conductance, pH and dissolved oxygen) were also recorded on each sample round.
Perimeter Wells Groundwater Sampling. Perimeter wells were sampled for VOC analysis monthly
for the first six months, and bimonthly for the following 12 months. Field parameters (temperature,
specific conductance, pH and dissolved oxygen) were also recorded on each sample round.
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'. 95-WP103.05
RESULTS AND DISCUSSION
!
Pilot Boring and Soil Sampling
The most significant results of the pilot boring and soil sampling was the lithoiogic logging. The
identification of very low permeability sediments below approximately 85 feet bgs within what is still
considered the upper water zone influenced the well construction. The ability of the UVB to drive
vertical circulation through a thick interval of low hydraulic conductivity sediments is limited.
Therefore, the well was constructed above 85 feet to ensure that a circulation cell would be created.
Although the results of the geotechnical and chemical analyses assisted in further defining site soil
characteristics, these results did not contribute significantly to the evaluation of the UVB groundwater
treatment and are not presented here.
Baseline Groundwater Sampling
The VOC analyses showed TCE concentrations ranging from 3.4 /*g/l to 1,000 jig/1 in samples obtained
from the perimeter wells. Except for monitoring well 31MW1 (3.4 pg/1), the TCE concentrations ranged
between 160 /tg/1 and 940 /ig/1 (Table 1). The presence of a relatively lower TCE concentration in
monitoring well 31MW1 supports the earlier finding that the groundwater within the alluvial aquifer at
Site 31 occurs in two zones. TCE concentrations of 6.4 jig/1 and 33.0 pg/1, respectively, were found in
the groundwater samples collected from the monitoring wells attached to the treatment well (Wl and
W3). A possible explanation for relatively low TCE concentrations (compared to perimeter wells) in
these samples is that water was used during well installation, which may have contributed to temporary
dilution of actual groundwater concentrations.
i
Operational Monitoring - Air Monitoring and Sampling
System Operating Parameters. Figure 5 is a graphical representation of the airstream flow data
measured at sample ports INTAKE and V2 as a function of time. These points represent the volume of
air entering the treatment well and used in air stripping (INTAKE), and the volume of air being
discharged by the blower (V2), which is a combination of intake air and air removed from the
unsaturated zone through soil vapor extraction.
I
The fluctuation in flow rates recorded in a few rounds hi the first few days after start-up is attributed
to equipment malfunction or operator error and are not considered to represent actual flow conditions.
The very low flow rates measured at the INTAKE in the initial seven weeks is attributed to the method
used for measuring air flow. Following modification to the INTAKE air monitoring port as shown on
Figure 5, the air flows at port V2 correlate very closely with air flows at the INTAKE port, indicating
that little to no air flow was occurring from the vadose zone. Since the UVB well is not located within
an area of soil contamination, soil vapor extraction was not performed during this pilot study.
Air Sampling Results. Air samples were collected from the four sample ports located on the
aboveground components of the system. The compounds detected in the air samples included: acetone,
benzene, 2-butanone, carbon disulfide, carbon tetrachloride, chloroethane, chloromethane,
dichloromethane, ethylbenzene, styrene, toluene, trichloroethane, trichloroethene, tetrachloroethene,
tetrachlorofluoromethane (F-l 1), and xylenes. The following trends were observed in the air analytical
data:
:]
Total VOC concentrations in the airstream peaked at 825.6 /ig/cu.m a few days following startup,
134
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95-WP 103.05
then stabilized at low concentrations between 1.3 to 75.7 /ig/cu.m after approximately one month
of operation.
• The chlorinated compounds chloroethane, chloromethane, dichloromethane, PCE, 1,1,1-TCA, and
TCE were detected in the groundwater and in the airstream.
The overall concentrations of VOCs within the air stream are much lower than was calculated
based upon anticipated removal rates from the groundwater
The highest VOC concentrations were from BTEX compounds which are not thought to be
associated with the groundwater at Site 31. Since the treatment well is located near an active
runway, the elevated BTEX concentrations most likely reflect ambient conditions.
Sample ports VI and V2 showed consistent results for sampling rounds where both samples were
collected, indicating that samples collected from either sample port are indicative of the air
concentrations being extracted from the UVB well.
Operational Monitoring - Treatment Well Groundwater Sampling
The TCE analytical results for groundwater sampling performed at the UVB treatment well are plotted
on Figure 6. Samples from well Wl are representative of the groundwater conditions in the lower, or
influent well screen, and samples from well W3 are representative of treated groundwater exiting the
UVB well in the upper .well screen.
Influent-TCE-concentrations, as measured~at well Wl, have" variecl between non-defect and 320 ng/1
throughout the pilot study. The highest influent concentrations, as well as the highest variability in
influent concentrations, occurred during the first five months of operation. This time frame corresponds
to the highest concentrations in the adjacent monitoring wells. The influent concentration peaks observed
during the 19-month pilot study probably reflect the inhomogeneity in the distribution of TCE entering
the treatment cell from upgradient areas.
For the most part, the effluent concentrations, as measured at well W3, have varied between non-detect
and IS jig/1 throughout the study. Eight anomalous peaks hi the effluent concentrations are exceptions
(Figure 6). These peaks in the effluent concentrations are explained as follows:
* Peaks 1, 2, and 3 are single sample occurrences corresponding to low concentrations in
monitoring well Wl. It is suspected that the samples collected during these sample rounds were
inadvertently switched between wells Wl and W3.
• Peaks 4 and .5 are suspected to be a response to system maintenance performed prior to those
sampling events. This interpretation is based solely on the coincident occurrence of the
maintenances and anomalous peaks, and not on a predicted theoretical basis. Unlike the single
sample anomalies discussed above, the concentration data for these two peaks are comprised of
several sampling rounds conducted over 1-2 weeks.
• Peaks 6 and 7 occurred following the development of a hole in one of the buoyancy tanks of the
UVB system. This occurrence caused the system to ride lower ha the water thereby reducing, or
eliminating, intake air flow and subsequent air stripping. Based on the groundwater sample data
135
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9S-WP 103.05
and air flow data, the hole developed sometime following the maintenance conducted on January
10/11, 1994, but prior to the February 3, 1994 sample round. The damaged buoyancy tank was
discovered and replaced on 17 May 1995,
Peak 8 occurred in early November 1994, following the system being shut down from October
26, 1994 to November 3, 1994 to allow for drilling beneath the power lines.
Disregarding the data from these anomalous peaks in the effluent concentrations, a comparison of influent
TCE concentrations to the effluent TCE concentrations for the stripper unit indicates that a TCE removal
percentage of greater than 90% was achieved in 95% of the sample rounds and a TCE removal
percentage of greater than 95% was achieved in approximately 77% of the sample rounds. It is evident
from this data that the UVB vacuum vaporization well is effectively treating the groundwater (removing
TCE) across the system. The UVB system effluent TCE concentrations as measured at monitoring well
W3 were below the Federal MCL of 5 ug/1 in 85% of the samples.
i
Operational Monitoring - Perimeter Wells Groundwater Sampling
Results of the groundwater TCE analyses for both the treatment and perimeter monitoring wells are
shown on Figure 7. For monitoring wells PW1 through PW6, data generated by PRC Environmental
Management, Inc. is also plotted. PRC was retained by the EPA SITE Program to perform field
sampling and technical analysis for this project
I
Several important trends are evident from review of the TCE plots and the summary concentration data
on Table 1.
I
• The final TCE concentrations in wells that are both within the treatment ce.ll, and have sufficient
data available to establish a trend, are lower than their initial concentrations. These wells include
PWl, PW2, PW4, PW5, 4MW14, and 310W1.
5
The concentrations in wells considered most affected by the UVB (PWl, PW2, PW4, PW5,
4MW14, and 31OW1) showed a marked increase following startup, followed by decrease after
several monttis of operation. Similar trends have been observed in previous UVB groundwater
remediation programs and have been attributed to mobilization of contaminants from the pore
spaces, particularly in the capillary fringe (Herrling et al., 1991). The increase and subsequent
decrease is delayed from PWl to PW4 (and from PW2 to PW5) which reflects the increased
travel time as the treatment cell expands over time.
j
• Wells screened deeper than the treatment interval (PW3, PW6, and 31MW1) do not appear to be
affected by the UVB.
• Well 3IMW4 is considered laterally outside of the capture zone as evident by fairly consistent
TCE concentrations.
* The monitoring well data is generally consistent with the capture zone model computation results.
Based on a comparison of Figures 4 and 7, it is evident that monitoring wells PWl, PW2, PW4,
PWS, PW7, PW8, 4MW14, 31PW1, and 31OW1 are located within the treatment zone.
Monitoring wells PW3, PW6, and 31MW1, are screened below the treatment interval.
Monitoring well 31MW4 is laterally outside of the treatment zone.
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95-WP103.05
An average TCE reduction of greater than 60% occurred in the monitoring wells which have data
available prior to system startup and are within the treatment zone (Table 1).
Mass Removals - The Mass Balance
The mass of VOCs removed from the groundwater was estimated by comparing the UVB well
groundwater influent concentrations to the effluent groundwater concentrations. The concentration of
VOCs removed multiplied by the average water flow through the stripping reactor (based on the pump
performance) resulted in an average removal rate for TCE from the groundwater to be on the order of
10 grams per day. The mass of VOCs collected in the air stream was determined by multiplying the air
sample concentrations by the average air flow rate, assuming that all the air flow was from the ambient
air intake pipe and no air flow was from the vadose zone. This resulted in an average removal rate for
TCE, as collected in the air stream, to be on the order of 0.1 grams per day.
This mass balance estimate shows at least an order-of-magnitude difference between the water and the
air side of the mass balance equation. That is, the mass balance estimate shows that the amount of TCE
entering and not leaving the UVB system through the water side, can not be accounted for by detailed
monitoring of the TCE being removed on the air side of the system. The assumption associated with
this analysis is that there are only two compartments to the mass balance. Based on these results, it is
suspected that the simple two-compartment conceptual model for TCE removal by air stripping as the
primary treatment mechanism may be overly simplified and should be further evaluated.
CONCLUSIONS
An 18-month demonstration project of the UVB Vacuum Vaporizer Well technology has been completed
at Site 31, March AFB. The primary objective of the study was to evaluate the feasibility of the UVB
system for removal of chlorinated hydrocarbons from the groundwater. The monitoring and sampling
program designed to generate data necessary for evaluating the system effectiveness consisted of soil
sampling, baseline groundwater sampling, air monitoring and sampling, and treatment and perimeter
groundwater monitoring well sampling. Conclusions derived from analysis of the data are as follows:
• Except for the scheduled maintenances, the system operated without interruption for the entire
18 months.
• During normal operating conditions, TCE removal of greater than 95% was achieved..
• Effluent TCE concentrations were below the Federal MCL in 85% of the samples.
• Final- perimeter well TCE concentrations for those wells within the treatment zone are lower than
their initial concentrations.
• Perimeter well TCE concentrations for those wells within the treatment zone showed a marked
increase in the first few months of operation. These results are attributed to mobilization of
contaminants from the pore spaces, particularly in the capillary fringe.
• Capture zone evaluation using Healing's model estimated the radius of the treatment cell at
approximately 110 feet
Perimeter well results validated the calculated treatment cell size.
• The calculated mass of contaminants removed from the groundwater and from the air samples
is at least an order-of-magnitude off. It is suspected that additional treatment mechanisms other
than air stripping may be performing a significant role in TCE removal.
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95-WP103.05
Table 5-4 Summary of Monitoring Well Results
Well
Number
31MW1
31MW4
31OW1
31PW1
4MW14
PW1
PW2
PW3
PW4
PW5
PW6
PW7
PW8
Screened
Interval
(fcbgs)
150-160
75-95
60-80
50-90
34-75
37.5-57.5
64.5-74.5
90-105
37-57
68.25-78.25
91-106
35-55
35-55
Initial
TCE Cane.
(ugflL) .
3.4
170
940
2
160
400
1,000
130
480
270
130
2
2
TCE Cone. Range
During Study
-------
Figure I - Site Layout Map
3 05
«t{t air "W. 1 il"
139
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Figure 2 - L'VB Vacuum Vaporizer Well Cross-Section.
95-WP 103,05
To
HIM»
Ground Surface
Monitoring Wells (W2 & W3)
with Stainless Steel Screen
(40 ft to 55 ft)
1 PVC 2 inch Deep •
Monitoring Well (W1)
with Stainless Steel Screen
(69.7 ft to 79.7 ft)
Unsaturated
..«**.— rr:^ Zone
IK
GnoSS3*^SwF --~'7"-
.l™""^^
3 Double— cased Sejreem^^^v
^1 -9 ft+« /*«— f*5! >*•"*
f*i jv*n IrtMHii
-------
Figure 3 - I'VE Vacuum Vaporizer \\ell System.
95-VVP103 05
141
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Figure 4 - UVB "Capture Zone" at Site 3L
W.\VT10305
-------
Figure 5 - Comparison of Air Flow Rates.
95-WP103 05
I.
O «0
o
10
1
(mjat)
143
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Figure 6 - Concentration of ICE During 18-.vfonth Study in Wells Wl and W3.
95-WP103
144
< iiiiii .1 .iiu i ' • i i 'Lhri, 'Jii'iifiiiiiiiiii,!1 >iiSi!L
-------
Figure 7 - Results of TCE Analysis in Treatment and Perimeter Wells.
95-WP103 05
145
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Appendix B2
Case History of Hydrocarbon Remediation Using the
UVB technology at a UST Site in Troutman, North Carolina
146
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CASE HISTORY OF HYDROCARBON REMEDIATION USING THE UVB TECHNOLOGY
AT A UST SITE IN TROUTMAN. NC
by
William G. Langley and Eric J. Klingel
IEG Technologies
Charlotte, NC
J. Kevin Slaughter
EA Engineering, Science and Technology
Charlotte, NC
Elliot J. Nightingale
Nightingale Geologic Consultants, P.C.
Charlotte, NC.
Abstract
UVB (German acronym for "Vacuum Vaporizer Well") is a patented in-situ remediation
technology for the restoration of aquifers, the vadose zone, and the capillary fringe. The UVB
technology can be applied to treat single- or multi-phase volatile organic compounds (VOCs)
and semi-volatile organic compounds (SVOCs). The UVB system uses a combination of
physical and biological processes for the removal of organic contaminants. The UVB can be
configured to simultaneously treat the saturated zone, capillary fringe, and/or vadose zone.
The UVB is a trua in-situ process in that there is no above-ground water treatment or
discharge. Only the off air stream is vented at the surface.
Since its inception in 1986, the UVB technology has been applied at some eighty sights in
Europe. The technology has achieved regulatory acceptance in the U.S. at both the state and
federal levels. A UVB system was first installed at a U.S. site in September 1992. Currently,
there are twenty-two UVBs installed and operating in eight states in the U.S. This paper
describes the remediation progress using the UVB at an underground storage tank (UST) site
in Troutman, North Carolina. After twenty-five months of operating the UVB at this site, the
magnitude and extent of the dissolved petroleum hydrocarbon (BTEX) plume has been
significantly reduced.
Introduction
UVB (Unterdruck Verdamfer Brunnen - German for Vacuum Vaporizer Well) is a patented
technology that offers a number of variations for the treatment of adsorbed, dissolved, and
free phase VOCs and SVOCs. (Patent held by lEG mbH, D-72770, Reutlingen, Germany.) It
is highly adaptable to varying hydrogeologic conditions including confined and unconfined
aquifers, and aquitards. Simultaneous treatment of the vadose zone, capillary fringe, and
saturated zone is possible. At the present time in the U.S., twenty-two UVBs are operating
in eight states.
Following a brief narrative on the basic system concept, a description of the treatment zone
and monitoring results are presented for a UVB which has been operating for twenty-five
months at a UST site in Troutman, North Carolina.
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Basic System Concept
As shown In Figure 1, the UVB system consists of a specially adapted groundwater well with
two separate screen sections, a groundwater treatment gnit located inside the well casing
(typically a "stripping reactor"), an above-ground mounted blower, and an optional ofr-air
treatment system. The blower creates a reduced pressure within the air-tight well casing.
Atmospheric air is introduced to the system, by virtue of the pressure differential, via a fresh
air pipe which is open at the ground surface and connected to the stripping reactor located
in the wall casing. Fresh air is drawn through the fresh air pipe into the stripping reactor
where it is directed to a sieve plate. As air bubbles migrate upward from the sieve plate, they
strip the VOCs dissolved in groundwater passing through the stripping reactor. The off-air
stream, which now includes vapor-phase contaminants, is brought to the surface by the
blower and treated as necessary.
j
The rapidly expanding and rising air bubbles produce.an air-lift pump effect which, together
with the vacuum in the weli casing, elevates the groundwater in the well and causes suction
at the lower well screen. The subsequent fail of groundwater along the walls of the well
produces an oscillating hydraulic pressure which forces the water horizontally through the
upper screen into the aquifer. A portion of the treated groundwater eventually migrates from
the upper screen to the lower screen by means of an extensive three-dimensional groundwater
flow field. In the presence of a natural groundwater flow, a portion of the flow entering the
well casing will be new upstream waters which have entered through the upstream capture
zone. An equal portion leaving the well casing will exit the circulation cell through the
downstream release zone. These flows and the dimensions of the capture zone, circulation
celt, and release zone can be calculated using design aids based on numerical simulations of
the groundwater hydraulics.
:|
Aerobic biodegradation of organic contaminants is enhanced by the recirculation of
oxygenated groundwater into the aquifer. The vadose zone and capillary fringe are remediated
by virtue of their exposure to the upper screened section of the UVB well by soil flushing and
soil vapor extraction mechanisms.
Case History; Troutman. North Carolina
A UVB 400 mm system (16 inch diameter well casing) was installed in September 1992 at
a former retail gasoline facility in the Piedmont physiographic province in west central North
Carolina. A site map depicting well locations and isopleths of total BTEX concentrations prior
to UVB activation appear in Figure 2. The saturated regolith consists of saprolite from a depth
of about 45 feet from land surface to the top of weathered rock at about 65 feet from land
surface. The saprolite is heterogeneous and varies in grain size from medium to fine sand, to
silt with clay, and is derived from the bedrock, a quartz-biotite gneiss.
A diagram showing the construction details of the UVB weli is given as Figure 3. Depth to
water at this site is 45 feet below ground surface. Groundwater flow is to the south and the
approximate hydraulic conductivity "is 1.9 x 10"* cm/sec. A 20 foot interval of the saturated
zone is being addressed by the UVB system.
148
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Prior to initiation of active remedial measures, dissolved petroleum hydrocarbon constituents
historically were present in all five original monitoring wells (MW-1 through MW-5, Figure 2).
Additional monitoring wells (MW-6 and DW-1) were installed after UVB system activation to
better define both the lateral and vertical extent of petroleum hydrocarbon contamination. The
lateral extent of dissolved BTEX in ground water has been interpreted from analytical data
gathered prior to activation of the UVB and after system start-up. Vertical hydrocarbon extent
is being monitored through the Type 111 monitoring well DW-1 completed in bedrock and
located cross gradient to the UVB system.
The UVB system was activated on September 17, 1992. The capture zone, circulation cell,
and release zone were calculated to encompass the areas shown in Figure 4. The capture
zone is defined by the width Bt at the top of the aquifer and the width Bb at the bottom of
the aquifer. The initial hydrocarbon removal rate in the off-air stream was estimated to fan
34.3 Ibs/day (Table 1). Since a portion of the upper screen is open to the vadose zone, soil
vapor extraction is occurring. However, about 95% of the initial removal rate was attributed
to hydrocarbon removal from the saturated zone and capillary fringe. One day after start-up,
the removal rate was 23 Ibs/day. Since operating day 58 to the present (operating day 796),
the removal rate has remained below 1.3 Ibs/day. Prior to the most recent sampling event
the stripping reactor efficiency has ranged from 58% to 100% for BTEX and from 95% to
100% for IPE, based on the analytical results for the shallow and deep UVB annulus wells
(Table 2). Results from the most recent sampling event (operating day 796) revealed that the
BTEX concentrations were higher in the shallow annulus well than in the deep annulus well,
which is a reversal of the normal trend. This was likely due to the fact that sampling occurred
only a few hours after restarting the system following a shut-down. Hydrocarbon removals
and reductions are summarized in Tables 1 and 2, and Figures 5 and 6.
A significant decrease in the concentration of dissolved BTEX near the center of the plume at
MW-3 (10 ft from the UVB well) has been observed since the first round of sampling after
start-up through the most recent sampling event on operating day 796 (Table 2). At startup,
dissolved BTEX was 1719 ug/l at MW-3. All post start-up dissolved BTEX concentrations at
MW-3 have been less than 254 ug/l. Also, comparing dissolved constituent concentrations
in the other monitoring wells, the lateral extents of the dissolved BTEX plume (Figures 2 and
6, Table 2) and dissolved IPE plume (Table 2) have diminished.
In addition to the physical removal of VOCs which takes place within the stripping reactor, the
UVB also introduces dissolved oxygen (DO) into the circulating groundwater. As expected,
there is a characteristic increase in DO between the deep and shallow annulus wells of the
UVB (Figure 7). Moving out into the aquifer, there is a rapid decrease with distance from the
UVB as evidenced by the DO measurements in MW-3 (Table 4). This decrease is likely due
to dilution, mixing, and biodegradation of hydrocarbons in the aerobic zone surrounding the
UVB well.
149
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Table 1 . Offgas data from the UVB site at Troutman, NC
Operating Day
(Date)
1
2
9
16
23
30
44
58
79
93
273
352
473
603
733
781
Volatile Hydrocarbon
Concentration (ppm)
371.48
298.06
164.80
45.38
84.S3
64.13
5O.01
14.0O
3.71
18.61
0.13"
12.53
1.47
11.30
9.38
13.09
Air Row Hate
(cfm)
350
3OO
350
444
250
243
235
267
247
284
300
270
250
250
200
200
Estimated Removal
Rate (Ib/day)
34.3
23.4
15.2
4.8
5.6
4.1
3.1
O.S9
0.24
1.24
0.01
1.25
0.14
1.10
0.69
0.97
* Sample analyzed by laboratory. All other sample* analyzed by portable GC.
Table 2. Concentration* (ug/1) of petroleum hydrocarbon compound* in flroundwater at UVB *ite,Troutmon, NC
Operating
Day
•307 ••
1
58
148
273
352
473
609
796
Well
Number
MW-1
(44'-54'J •••
BOX
BQL
BQL
BOJ.
BOX
BQL
BQL
Benzene
ClOB/U*
8
BOX
BOX
BQL
BOX
BOX
BQL
BOX
BQL
Toluene
{1000 US/1)
11
BOX
BQL
BQL
BQL
BQL
BQL
BQL
BQL
Ethyl-
benzene
<29ug/1|
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
Total
Xyienea
{630 ug/l)
12
2
BQL
BQL
BQL
BQL
BQL
BOX
BQL
Total
BTEX
31
2
SQL
BQL
BQL
BQL
SQL
BQL
BQL
MTBE
UOOuo/ll
BQL
BQL
BQL
130
130
BQL
BQL
BQL
BQL
IPE
IOU
160
120
BQL
BQL
77
110
10
20
71
• North Carolina 2L Standards..
DL » Detaotfon limit.
•* Negative values are day* before UVB •tart-up.
BQL - Below quantitation limit.
*•• Screened Interval.
150
-------
Table 2. Continued.
Operating
Day
-307
1
58
143
273
609
733
796
-307
1
58
148
273
352
473
609
733
796
-307
1
148
273
796
-307
1
148
273
798
Well
Number
MW-2
(44'-54')
MW-3
(47.5<-57.51)
MW-4
(44--541)
MW-5
<42'-52')
Benzene
(1 ug/l>*
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
840
1600
18
55
9.3
2.5
98
39
237
32
BQL
BQL
BQL
SQL
BQL
BQL
BQL
BQL
BQL
BQL
Toluene
(IOOOug/1)
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
15
63
2.5
1.3
BQL
BQL
4.2
BQL
BQL
3
BQL
BOL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
Ethyl-
benzene
(29 Ufl/l)
BQL
BQL
SQL
SQL
SQL
BOL
BQL
BQL
BQL
3
1
1
BQL
BQL
BQL
BQL
BQL
BQL
BQL
2
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
Total
Xyienes
(630 ug/l)
. BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
69 '
53
2.7
2.9
SQL
1.2
3.9
BQL
17
13
BQL
13
BQL
BQL
BQL
BQL
BQL
SQL
BQL
BQL
Total
BTEX
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
924
1719
23.2
60.2
9.3
3.7
106
39
254
41
BQL
15
BQL
BQL
BQL
BQL
BQL
BQL
BQL
. BQL
MTBE
(200 ug/t)
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
SQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
SQL
BQL
BQL
BQL
BQL
BQL
IPE
(DL)
74
56
56
BQL
BQL
BQL
BQL
BQL
2600
2000
850
1100
590
480
1200
690
2000
663
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
* North Carolina 2L Standard*.
OL - Detection limit.
•» Negative values are days before UVB start-up. *•* Screened interval.
BQL - Below quantitation limit.
151
-------
Tabta 2. (oontlnuod)
Operating
Day
148
273
352
473
609
733
736
143
273
352
473
609
733
736
S3
145
273
3S2
473
609
733
791
1
58
148
273
352
473
609
733
796
Well
Number
MW-6
(40.51- SO.S'J
DW-1
(B7'-97')
UVB-Shailow
(40--491)
UVB-Daep
(eo.a'-e^s1)
Banzona
(1 ug/ll '
1
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
6.2
BQL
BQL
BQL
2
6.5
9.4
11
24
2.9
2
BQL
6
IS
71
660
140
220
50
334
41
6
Toluene
[1000 us/1)
1.3
1
BQL
SQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
7.8
13
26
61
7.4
8
BQL
22
6
5
22
4.4
3.3
3
BQL
BQL
2
Ethyi-
benzene
(29 ug/ll
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
1.8
4.1
BQL
BQL
BQL
2
3
1.1
BQL
1.1
1.2
BQL
BQL
BQL
BQL
.Total
Xylenes
(530 ug/l)
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
3
2.5
6.8
18
3.1
4
BQL
14
11
8.7
53
30
25
3.9
BQL
3
4
Total
BTEX
2.3
1
BQL
BQL
BQL
BQL
BQL
BQL
BQL
6.2
BQL
BQL
BQL
2
17.1
24.9
45.6
105
13.4
14
BQL
44
38
85.8
735
176
250
56.9
334
44
12
MTBE
(200 ug/ll
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
IPE
(DU
10
21
13
10
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
BQL
10
25
40
41
18
SOL
SQL
12
600
1400
1100
1000
960
780
110
434
300
• North Carolina 2L Standard*.
DL - Detection limit.
•• Negative values are day* before UVB start-up. ••• Screened Interval.
BQL • Below quantitation limit.
152
-------
Table 3. Dissolved oxygen concentrations (mg/l) in graundwatsr at the UVB aita in Troutman, NC
Operating
Day
-6
1
1.1
2
3
16
23
30
44
58
79
273
352
473
609
733
796
MW-1
3.20
1.75
1.44
1.10
1.OO
1.20
1.25
1.30
1.30
1.90
1.65
0.79
1.60
NS
3.20
NS
1.50
MW-2
5.20
3.70
3.55
3.15
2.20
2.50
3.27
3.55
2.95
3.30
3.55
7.30
NS
NS
4.20
6.50
7.OO
MW-3
NS
NS
NS
NS
1.50
1.00
2.00
1.70
0.75
2.30
o.ao
1.11
0.20
NS
0.10
0.20
0.5O
MW-4
6.40
NS
NS
5.15
3.25
4.50
6.10
5.90
5.40
5.90
6.40
8.39
NS
NS
7.50
8.10
7.80
MW-5
4.70
NS
NS
NS
0.80
1.30
3.25
1.10
1.00
0.90
1.40
6.60
NS
NS
0.20
6.80
7.00
UVB A
Daep
0.95
O.95
1.20
0.82
0.8O
O.75
1.40
0.75
0.9O
O.80
O.6O
NS
0.20
NS
O.30
3.30
O.60
UVBB
Shallow
NS
8.80
9.00
8.30
5.50
7.80
9.60
8.90
8.90
10.50
8.10
8.79
7.80
NS
8.40
8.80
9.30
NS - Not sampled.
153
-------
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156
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