EPA-700-8-87-037
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
HAZARDOUS WASTE GROUND WATER TASK FORCE
GROUND WATER MONITORING EVALUATION
HUGHES AIRCRAFT, U.S. AIR FORCE PLANT NO. 44
TUCSON, ARIZONA
April 1988
Mark G. Filippini
Donn Zuroski
U.S. Environmental Protection Agency
Region 9
U.S. Envirohmenta! Protection Agency
5, Library (PL-12J)
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April 29, 1988
UPDATE OF THE HAZARDOUS WASTE GROUND WATER TASK FORCE EVALUATION
OF HUGHES AIRCRAFT/U.S. AIR FORCE PLANT No. 44, TUCSON, ARIZONA
The United States Environmental Protection Agency's Hazardous
Waste Ground Water Task Force (Task Force) in conjunction with
the State of Arizona Department of Health Services (now the
Department of Environmental Quality) and the Arizona Department
of Water Resources conducted an evaluation of the ground water
monitoring program at Hughes Aircraft/U.S. Air Force Plant No. 44
(Hughes/AFP #44) located in Tucson, Arizona. Onsite field inspections
we^e conducted between April 20 and 24, 1987. The evaluation of
the facility focused on (1) determining if the facility was in
compliance with applicable regulatory ground water requirements
and policies under the Resource Conservation and Recovery Act
(RCRA), (2) determining the nature of hazardous waste constituents
present in the ground water, and (3) identifying inactive solid
waste management units.
Hughes/AFP #44 is one of 58 facilities that are to be
evaluated by the Task Force. The Task Force effort came about in
response to concerns by Congress and the public as to whether
hazardous waste treatment, storage, and disposal facilities are
complying with the State and Federal ground water monitoring
regulations.
The results of the chemical analysis of ground water samples
collected from existing monitoring wells at the facility indicated
the presence of several previously unidentified organic contaminants
and elevated levels of radionuclide parameters in a RCRA perched
zone well. Due to the deficiencies in the design of the ground
water monitoring system, it cannot be determined if the compounds
are the result of releases from the RCRA units or solid waste
management units (SWMU's) at the facility. Additional work will
be necessary to determine the nature, extent, and origin of these
compounds.
In order to comply with ground water monitoring permit
requirements, a facility's ground water monitoring system must be
capable of immediately detecting a release of hazardous waste
constituents from a regulated unit. Hughes/AFP #44 does not have
in place a ground water monitoring system capable of meeting
these requirements. Hughes/AFP #44 has been operating under a
Federal Facility Compliance Agreement since May, 1984, which
authorized use of an alternative ground water monitoring system.
That agreement terminates on issuance of a RCRA operating permit.
In October 1987, EPA and the State of Arizona received from
Hughes Aircraft a revised Part B permit application which includes
a proposal to install a ground water monitoring system consistent
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with current technical guidance. Both agencies are reviewing the
proposed system. It is anticipated that a determination on the
issuing of an operating permit by the Agencies will be made by
September 1988.
EPA conducted a RCRA Facility Assessment to determine the
status of solid waste management units (SWMU's) at Hughes/AFP #44
in August of 1987. Over 100 solid waste management units (SWMU's)
were documented at the Hughes/AFP #44 facility. Only limited
investigations on selected units have been conducted by the
facility/ and most units have not been properly characterized. A
thorough characterization of these units and any required corrective
measures will be necessary to meet the requirements of the 1984
Hazardous and Solid Waste Amendments (HSWA) to RCRA.
Despite documented ground water contamination, the facility has
claimed that no continuing sources of contamination exist at this
site. Hughes/AFP #44 is currently operating a pump and treat
system to remove contaminants from the ground water. In February,
1988, Hughes Aircraft notified EPA that they have sampled and
analyzed soils at an on-site abandoned waste disposal unit and have
determined that the soil is contaminated with TCE. The facility
has implemented only limited source control measures to correct
continuing releases.
Should it be determined by the Arizona Department of Environ-
mental Quality and the Regional Administrator of EPA that the
Part B application meets the RCRA Part 264 requirements for an
operating permit, corrective action conditions will be written
into the permit to address the SWMU's. These permit conditions
will require the facility to identify, characterize, and take
appropriate corrective action on all SWMU's at the facility as
required under the HSWA portion of RCRA. Further, the permit
would require upgrading of the ground water"monitoring system.
If the agencies deny the operating permit, appropriate
enforcement action, rather than permit conditions, could be taken
to assure that releases from the SWMU's are addressed and that an
adequate ground water monitoring system is installed.
In response to actions taken by Hughes Aircraft during the Task
Force inspection EPA has initiated an in-depth investigation into
possible violations of RCRA related to waste handling, waste
disposal and record keeping procedures at Hughes/AFP #44.
Based on this Task Force investigation the facility must
do the following:
1. Submit an adequate hydrogeologic site characterization
report which includes identification of potential pathways
for contaminant migration and a determination of the impact
of the Installation Restoration Program (CERCLA) pump and
treat system on the local hydrogeology.
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2. Install a ground water monitoring system capable of meeting
the requirements of RCRA §264 Subpart F.
3. Provide an updated Sampling and Analysis Plan that establishes
the procedures to be used by the facility and identifies the
laboratory that will analyze the samples.
4. Conduct a ground water assessment program to determine the
source of the elevated radionuclides detected in the perched
zone well.
5. Determine the existence, nature, content, and impact on the
ground water of all SWMU's on the facility.
As stated above, it is anticipated that the technical aspects
of the above items will be addressed through the permitting process.
Enforcement action may be pursued if necessary.
This concludes the Hazardous Waste Ground Water Task Force
evaluation of the Hughes Aircraft/U.S. Air Force Plant #44
facility.
Donn Zuroski
U.S. Environmental Protection Agency
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CONTENTS
Page
I. EXECUTIVE SUMMARY 1
-A. INTRODUCTION 1
1 Task Force Objectives 1
2 Background 3
B. SUMMARY OF FINDINGS AND CONCLUSIONS 8
1 Ground Water Monitoring System 8
2 Task Force Sampling Data 9
3 Conclusions 10
II. TECHNICAL REPORT 12
A. BACKGROUND 12
1 Site History 12
2 Enforcement History 12
a. CERCLA Enforcement 13
b. RCRA Ground Water Enforcement 15
B. INVESTIGATIVE METHODS 16
1 Facility Inspection/Records Review 16
2 Sampling Audit 17
3 Sampling Program 18
C. WASTE MANAGEMENT UNITS AND OPERATIONS 20
1 Current RCRA Units 20
2 Solid Waste Management Units 21
D. SITE GEOLOGY/HYDROGEOLOGY 23
1 Geomorphology 23
2 Geology 24
3 Soils 29
4 Hydrogeology 29
5 Climate 30
E. INTERIM STATUS GROUND WATER MONITORING 31
1 Current Monitoring System 31
2 Sampling & Analysis Plan and Field Procedures 36
(continued)
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II. (Continued) page
F. TASK FORCE DATA COLLECTION/RESULTS 38
1 Sample Collection Methods 38
2 Results of Task Force Data 42
REFERENCES . 46
APPENDICIES
APPENDIX A Analytical Parameters
APPENDIX B Review of Neutron Probe System at Hughes Aircraft
Report from Environmental Monitoring Systems
Laboratory --Las Vegas
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I. EXECUTIVE SUMMARY
A. INTRODUCTION
1. Task Force Objectives
This report summarizes the results of investigations
conducted during April 1987 at the Hughes Aircraft/Air Force
Plant 144 in Tucson, Arizona by the U.S. Environmental Protection
Agency.
Operations at hazardous waste treatment, storage, and disposal
(TSD) facilities are regulated by the Resource Conservation and
Recovery Act. Regulations promulgated pursuant to RCRA (40 CFR
Parts 260 through 265, effective on November 19, 1980 and sub-
sequently modified) address hazardous waste site operations
including monitoring of ground water to ensure that hazardous
waste constituents could be immediately detected if released
to the environment. The regulations for TSD facilities are
implemented (for EPA administered programs) through the hazardous
waste permit program outlined in 40 CFR Part 270.
The Adminstrator of the Environmental Protection Agency
(EPA) established a Hazardous Waste Ground Water Task Force
(Task Force) to evaluate the level of compliance with ground
water monitoring requirements at commercial off-site and selected
on-site TSD facilities and address the cause of non-compliance.
The Task Force comprises personnel from an EPA Headquarters core
team, Regional Offices, and the States.
The prinicipal objective of the inspection at Hughes Aircraft
was to determine compliance with the requirements of 40 CFR Part
265, Subpart F - Ground Water Monitoring. Compliance with related
requirements of the Part 265 interim status regulations, Hazardous
and Solid Waste Amendments of RCRA, and the corresponding State
regulations was also investigated. Additionally, the ground
water monitoring program proposed for final Part B permitting
status was evaluated for compliance with Part 270.14(c).
Recent amendments to RCRA require that facilities seeking a
RCRA permit must also address solid waste management units at tho
facilities; therefore, ground water monitoring systems associated
with any solid waste management units at the facility were also
evaluated.
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Specific objectives were as follows:
0 To determine if the facility is in compliance with interim
status ground water monitoring requirements of 40 CFR
Part 265 as promulgated under RCRA and the State equivalent
(as the State of Arizona has received RCRA authorization).
0 To determine if the ground water monitoring program described
in the facility's RCRA Part B permit application complies
with 40 CFR Part 270.14(c).
0 To determine if the ground water at the facility contains
hazardous waste constituents.
0 To determine if the ground water monitoring system can
immediately detect any statistically significant amounts
of hazardous waste constituents that migrate from the
waste management area to the uppermost aquifer underlying
the facility.
0 To determine if Hughes has developed and is following an
adequate plan and procedures for ground water sampling
and analysis.
0 To determine if the ground water quality assessment program
outline (or plan, as appropriate) is adequate.
0 To determine if recordkeeping and reporting procedures for
ground water monitoring are adequate.
0 To identify active and inactive solid waste management units.
To accomplish these objectives, the investigation consisted
of several discrete components including a ground water sampling
program, a sampling audit, and a complete record review.
Frances Schultz, Donn Zuroski, and Mark Filippini of EPA Region 9
comprised the investigation team. The team included Steve Callaway
from Arizona Department of Health Services, Bob Henckel with the
Arizona Department of Water Resources, Dan Opalski with EPA
Region 9 Superfund, and other State and EPA personnel.
Sampling of six facility wells, direction of the four person
Versar Inc. contract sampling team, and the audit of the facility
sampling procedures was conducted by Frances Schultz of the Field
Operations Branch, EPA Region 9.
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2. Background
Hughes Aircraft Company has operated U.S. Air Force Plant
No. 44 under contract as a government-owned, contractor-operated
(GOCO) military facility since 1951. The Plant is located on
Air Force property in Tucson, Arizona, immediately adjacent to the
Tucson International Airport (Figure 1 & 2).
The plant site encompasses 2,257 acres and includes 67
structures. Hughes employs 6,000 people at this plant, which
manufactures tactical missile systems. The RCRA regulated units
at the facility are part of an industrial wastewater treatment
plant (IWWTP) which is designed to recycle 75% of its industrial
wastewater back into the industrial water supply. The IWWTP,
constructed in 1977, is located at the southwest corner of the
plant site and includes 15 holding ponds, 20 evaporation beds, and
two tank treatment systems covering approximately 33 acres (Figure 3).
These units receive three listed hazardous wastes: F007, spent
cyanide plating bath solutions from electroplating operations;
F008, plating bath sludges from electroplating operations; and
F009, spent stripping and cleaning bath solutions from electro-
plating operations, plus two characteristic waste streams containing
chromium (D007) and lead (D008).
Ground water contamination at the Tucson International Airport
area was discovered in the early 1950's. Intensive investigations
of the ground water did not occur until 1979 when Hughes initiated
a ground water quality sampling program prompted by EPA.
Several areas of contamination have been identified in the
area (Figure 4). Ground water samples were found to contain
heavy metals, trichloroethylene (TCE), dichloroethylene (DCE),
and trichloroethane (TCA).
Most of the monitoring and clean-up activities occuring at
the facility are being directed by the Air Force under the
Installation Restoration Program, the Department of Defense's
CERCLA process. A ground water extraction treatment and reinjec-
tion system, which includes air stripping and ion exchange to
remove contaminants, went on line in April 1987.
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-H-
ScaJe o 2so wo an 300
Figure 1. Regional Location of AFP 44, Tucson. Arizona
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Saguaro National
Monument
Saguaro National
Monument
Davis-Monthan
AFB
San Xavier
Indian Reservation
Tucson
International
Airport
Santa Rita
Experimental
Range
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Location of formerly
used Percolation Bed
MOOUNO WASTt MINf
CVAfOMATION BCOS
\
WASTE BRINE
EVAPORATION
BEOS
SLUDGE DRYING
BEOS
MNOMt
1
FIG ORE 3 IWWTP PONDS AND BEOS (see Figure 4)
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• OUNOARY OF AIR FORCE LAND
EXPLANATION
APPROXIMATE LIMITS OF
TCE CONTAMINATION
I DURING 1884 (DASHED
I WHERE UNKNOWN
OK INFERRED)
Los Reales Road
Boundary
I'MILE
Figure 4
LOCATION OF TUCSON AIRPORT AREA
TUCSON »IH*OKT AREA
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B. SUMMARY OF FINDINGS AND CONCLUSIONS
The findings and conclusions presented in this report reflect
conditions existing at the facility and practices used by the
facility at the time of the Task Force investigation in April
1987. Subsequent actions taken by the facility, the State of
Arizona, and EPA Region 9 since the investigation are summarized
in the accompanying update cover memo attached to this report.
1. Ground Water Monitoring System
The Task Force investigated the interim status ground water
monitoring program implemented by Hughes Aircraft/Air Force Plant
144. The consensus opinion of the Task Force is that, although
the facility was in compliance with the 1984 Federal Facility
Compliance Agreement (FFCA) entered into between EPA and the Air
Force, the ground water monitoring program is not in compliance
with 40 CFR Part 265 Subpart F or 40 CFR Part 270.14 (c). The
FFCA allowed the current monitoring system, consisting of perched
zone wells and neutron probes, in lieu of a system meeting the
265 Subpart F requirements.
According to 265.90, an owner/operator of a land disposal
facility must implement a ground water monitoring system capable
of determining the facility's impact on the quality of the ground
water in the uppermost aquifer underlying the facility. This
program was to be implemented, by November 1981. At the time of
the Task Force investigation, the facility had not implemented
such a program but was operating in accordance with the Federal
Facility Compliance Agreement.
According to 270.14 (c), an owner/operator must submit an
application for a Part B RCRA Permit which proposed a ground
water monitoring system capable of meeting 264 Subpart F. The
ground water monitoring system proposed by Hughes in its last
three RCRA Part B Permit applications, the latest at the time of
this investigation being January 1987, failed to meet any of the
270 requirements but instead proposed to continue the alternate
ground water monitoring system imposed by the FFCA in 1984.
The FFCA monitoring system is based on the belief that any
leak from the ponds will migrate horizontally in the vadose zone
and then be detected by the neutron probe system, or that the
leak will affect the water level in the perched zone and will be
noted in sampling of the perched zone wells. The capability of
the system to detect leaks has not been adequately demonstrated.
The present ground water monitoring system is inadequate because:
1) The neutron probe system has not been demonstrated to be capable
of detecting releases from the RCRA units.
2) The 'present monitoring wells placed in the perched zone
do not monitor the uppermost aquifer immediately under the
RCRA units per 265.91 (a).
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3) There are no designated upgradient wells as required in
265.91 (a)(l).
4) Most of the wells monitored under the FFCA are dry wells.
Analysis is performed only when the ground water is high
enough so that the wells can be sampled.
5) Wells are not constructed properly as required per 265.91(c)
or RCRA guidance.
6) Facility never conducted analysis of Appendix III parameters
(EPA Interim Primary Drinking Water Standards) as is required
per 265.92(c).
7} Ground water sample analysis is inadequate for RCRA 265
monitoring purposes because there is no annual analysis for
phenolSr total organic carbon, or total organic halogens
as required per 265.93(d).
8) The facility's sampling and analysis plan is incomplete.
9) Sampling personnel did not follow all procedures described in
the sampling and analysis plan in the field.
10) Facility does not have an outline for a ground water quality
assessment program as required per 265.93(a).
11) Facility has not conducted any statistical analysis of ground
water monitoring data as is required per 265.93(b).
12) Facility has not determined the influence of the CERCLA pump
and treat system on the local ground water flow.
13) Facility has failed to submit a proposed ground water monitoring
program per 270.14(c)(l) through (8).
2. Task Force Sampling Data
As part of the Task Force investigation, samples were collected
from six facility wells. Only one of the six wells sampled was
part of the the RCRA monitoring program. The purpose of sampling
non-RCRA wells was to confirm reported levels of contaminants and
sample for expanded parameters. The sampling was not meant to
establish any releases from the regulated units. Well placement
and construction, as well as the existence of solid waste management
units in the area, precluded the Task Force from being able to make
meaningful determinations of releases from the data. Samples were
analyzed for Appendix IX and RCRA indicator parameters (Appendix A).
Results of the Task Force data are provided in Section II F 2.
The Task Force data on the six sampling points confirmed the iden-
tification of a total of five different organic compounds in the
Hughes wells. In addition, two unknown hydrocarbons and elevated
radionuclides were detected in RCRA monitoring well S-10.
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As expected based on Superfund investigations, trichloroethene
(TCE) and 1 , 1-dichloroethene (DCE) were found in most wells. TCE
was found in all wells except M-15. Levels ranged from 79 to
1800 ppb. DCE was found in wells S-10, M-2B and M-41 at levels
ranging from 22 to 230 ppb. Trans-1, 2-dichloroethene was also
detected in well M-41.
Well S-10 was found to be the most heavily contaminated well,
where, in addition to TCE and DCE, Caprolactam (20 ppb), 1-Hexanol
2-Ethyl (9 ppb) and two unknown hydrocarbons were detected. Levels
of metals and many indicator parameters were also higher in S-10
than in surrounding regional aquifer wells. Radionuclide levels in
well S-10 were dramatically higher than in all other wells sampled.
Total radium was reported at 33j^4 pCi/1, gross alpha was reported
at 180*90 pCi/1, and gross beta was reported at 350^90 pCi/1.
These levels of radionuclides were two orders of magnitude higher
than in surrounding wells. It could not be determined if these
levels are naturally occuring or indicate some unknown source.
Levels of barium, chromium, and nitrate nitrogen were also elevated
in well S-10. Dissolved barium was reported at 219 ppb, dissolved
chromium was reported at 281 ppb/ and nitrate nitrogen was reported
at 11,000 ppb.
These results indicate some unknown source or sources of
contamination exist in the area, either solid waste management
units or RCRA units. Limitations of the Task Force data and the
inadequacy of the monitoring system make it impossible to confirm
the existence and nature of these sources. This demonstrates the
limited capabilities of the neutron probe system, the perched zone
wells and the analytical parameters selected.
3. Conclusions
In summary, we have found the following at the facility as a
result of this investigation:
8 The facility does not have in place a ground water monitoring
system capable of meeting RCRA 40 CFR Parts 265 or 264 ground
water monitoring requirements.
0 The facility has not submitted a hydrogeologic site characteriza-
tion report as required under S 270.14(c).
0 Several facility wells sampled by the Task Force have shown
unreported levels of some organic and inorganic
constituents indicating the possibility of some unknown sources
of contamination not yet identified by the facility.
The designated RCRA monitoring wells are not properly designed
or constructed.
Hughes' groundwater sampling and analysis plan is incomplete.
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Th e facility did not follow all procedures described in the
sampling and analysis plan.
Proper reporting procedures for ground water monitoring data and
recordkeeping procedures in the field are not being followed.
The facility does not have a ground water quality assessment
outline.
A determination of the influence of the Installation Restoration
Program (CERCLA) pump and treat system on the local ground water
flows has not been conducted.
A thorough analysis of location and content of the solid waste
management units at the facility and their potential impact on
the ground water has not been conducted.
Although a ground water restoration program is in place at the
facility, only limited source control investigations or measures
have been conducted at the facility.
Despite the documented existence of over 100 solid waste manage-
ment units at the facility, facility-generated reports claim
that no continuous sources of ground water contamination exist.
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II. TECHNICAL REPORT
A. BACKGROUND
1. Site History
Hughes Aircraft operates U.S. Air Force Plant 44 (AFP 44).
The plant has been active since 1951. Hughes/AFP #44 is a
government-owned, contractor-operated (GOCO) operation. The
facility has a workforce of 6000 people employed manufacturing
tactical missile systems. The installation encompasses 2,258
acres of desert land. Over 80 percent of the installation property
is undeveloped.
Industrial wastewaters generated by processing operations
have been treated on-site since production began in 1952. Treat-
ment methods have evolved from batch and flow-thru treatment to
the present day zero-discharge system.
From 1952 until 1961, processing solutions of sulphuric,
hydrofluoric, nitric, hydrochloric, acetic, and phosphoric acids
were diluted in tanks and discharged into a natural drainage
wash. Records indicate that approximately 20,000 gallons per week
were disposed of in this manner.
In 1954 a batch treatment plant came on line. The plant
treated concentrated solutions of chrome and concentrated
solutions of cyanide wastewaters. The cyanide solutions were
oxidized, the chromic solutions were reduced from hexavalent to
trivalent chromium. The treated solutions were then mixed with
cooling water blowdown and discharged through the natural drainage
wash into unlined ponds. Facility records indicate that approxi-
mately 160 gallons per week were disposed of in this manner.
In 1962 a flow-through treatment system was added to the
batch treatment facility. This system handled rinsewaters other
than solutions of chrome and cyanide. The system generated a
heavy metal sludge which was sent to unlined drying beds. The
treated wastewaters were discharged through the natural drainage
wash into unlined ponds. Records indicate that between 1962 and
1977 approximately 15,000 gallons of chrome and cyanide wastewaters
per week and 1,250,000 gallons of rinsewaters per week were dis-
charged to the natural drainage wash.
Between 1952 and 1977 general industrial wastes and industrial
wastewaters were disposed of on site in ponds, pits and drainage
channels. Waste types included machining coolants and lubricants,
TCA, TCE, methylene chloride, paint sludges and thinners, plating
and deburring rinsewater, acid solutions, caustics, cyanide
solutions, heavy metal sludge, alcohols, and flammable solvents
including acetone and MEK.
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In 1977 a zero discharge wastewater treatment plant come on
line. The new treatment plant employed batch treatment of cyanide
and acid wastes as well as a flow-through system to treat general
industrial wastes. In 1984 the wastewater treatment plant ponds
were retrofitted with double liners with a leak detection system.
Over 100 solid waste management units (SWMU's) have been
identified at the facility. They include unlined pits, unlined
wastewater ponds, sludge drying beds, drainage channels, explosive
pits, and numerous tanks. Historic and present waste management
practices are detailed in the RCRA Facility Assessment report
discussed later and included in the EPA Hughes file.
The facility is now pursuing a RCRA Part B permit for the
wastewater treatment plant surface impoundments. The facility
has proposed as part of their permit the ground water monitoring
system agreed to in the 1984 Federal Facility Compliance Agreement
consisting of the neutron probe and the perched zone wells.
2. Enforcement History
a. CERCLA Enforcement
Ground water contamination in the Tucson International Airport
area was discovered in the early 1950's. Intensive investigation
of ground water contamination did not occur until 1979 when Hughes
initiated a ground water quality sampling program prompted by the
EPA.
In March 1981 an investigation conducted by EPA (under CERCLA)
identified trichloroethylene (TCE) and chromium contamination in
the ground water around the Tucson International Airport. As a
result, seven municipal wells were removed from service. Subsequent
investigations have resulted in the delineation of three distinct
areas of contamination. The largest encompasses about five square
miles of aquifer surface area. Most of the contamination is
believed to be within the uppermost 100 feet of the saturated
zone, although a thorough site characterization report has not been
submitted.
In November 1982, Hughes and the U.S. Air Force assumed
responsibility for investigating contamination south of Los
Reales Road, while EPA assumed responsibility for investigating
contamination north of Los Reales Road (see Figure 4). Ground
water samples at Hughes were found to contain trichloroethylene
(TCE), dichloroethylene (DCE), trichloroethane (TCA), hexavalent
chrome, benzene, xylene, and chloroform. Hughes and the Air Force
have concluded that contamination beneath the facility had been
caused by past disposal of waste solvents and chromium and claimed
that no continuing sources existed on the facility (Hargis and
Montgomery, Phase I, 1982). Consequently, the Installation
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Restoration Program (IRP) conducted by the Air Force in 1985 did
not contain any proposed source control measures despite the
existence of over 100 SWMU's at the facility. This study concluded
that the contamination had moved off-site.
The Tucson Airport Area Remedial Investigation (RI) was
concluded in 1985 and covered that portion of the known contamina-
tion north of Los Reales Road (i.e. that portion not covered by the
Air Force IRP). The RI was managed by ADHS under a cooperative
agreement with EPA Region 9. Major components of the RI included
drilling, testing and sampling of ground water, development of a
solute transport model, studies of potential sources of ground
water pollution, and interpretation of hydrogeologic and water
chemistry quality data.
Studies of the Tucson International Airport Area have classi-
fied three aquifers in the area of contamination; the upper, the
lower, and the undivided aquifer. The undivided aquifer has been
defined by Hargis & Montgomery (Phase II, 1982) as that portion
of the regional aquifer which does not contain a perched zone.
Hargis and Montgomery have stated that the undivided portion of
the aquifer does not exist beneath the facility (i.e. the perched
zone extends beneath the entire portion of the wastewater treatment
plant RCRA units).
To date, over 100 monitoring wells have been drilled to
identify, characterize, model, and monitor the contamination in
the area. These wells have shown that: the perched zone has been
contaminated with chromium, toluene, TCE, TCA, and DCE; the upper
aquifer zone has been contaminated with chromium, TCE, TCA, and
DCE; the lower aquifer zone has been contaminated (to a lesser
degree) with chromium TCE, TCA and DCE.
Eighteen remedial alternatives were designed and analyzed by
consultants to the Air Force as part of the Remedial Action Plan
(RAP) for Hughes. The Air Force selected ground water extraction,
treatment, and recharge as the preferred remedy. The remedial
system includes a network of ground water extraction wells, a
treatment plant, and a network of wells to inject the treated
ground water. This project involves pumping, treating, and
recharging approximately 26 billion gallons of water. The treatment
plant will be in full operation by 1988. The Air Force estimates
that at least 10 years will be required to remove the volatile
organic compounds and chromium. Extraction and injection wells
surround the RCRA surface impoundments at the facility.
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b. RCRA Ground Water Enforcement
RCRA ground water monitoring at Hughes/AFP 144 is currently
regulated by the state of Arizona under regulations equivalent to
40 CFR Part 265, Subpart F. The following is a summary, in
chronological order, of major permiting and enforcement milestones.
- In November of 1980, the facility notified EPA as a RCRA TSD.
The Part B application requested a ground water monitoring
waiver. The waiver request was based on a leak detection
system which uses a neutron probe monitoring network and leachate
collection tubes under the ponds.
- An Interim Status inspection in September 1982 showed that sludge
beds listed as being lined on the Part A notification were, in
fact, unlined.
- A 1983 EPA report stated that an alternative to ground water
monitoring could include neutron probes, but that the neutron
probe system had been improperly installed.
- In April 1983, the facility notified ADHS that double liners would
be installed at the sludge beds.
- EPA issued a compliance order in June of 1983 for failure to
install a ground water monitoring system.
- A Federal Facilities Compliance Agreement (FFCA), signed in May
1984, waived 40 CFR 265 Subpart F ground water monitoring
requirements and allowed the facility to use an upgraded neutron
probe system used in conjunction with a water balance and
perched zone monitoring system.
- May 1984, EPA found the proposal to double line the IWTP
surface impoundments to be in compliance with current regulations.
- July 1984, EPA issued a Notice of Deficiency (NOD) stating that
the August 1983 Part B submittal was incapable of meeting 264
Subpart F.
- December 1984, a revised Part B which incorporated the ground
water monitoring system outlined in the FFCA was received.
- In January 1987, the facility submited an additional Part B
revision as a result of process changes at the facility (not as
a result of an NOD); the ground water portion is identical to
December 1984 version.
- In May 1987, the Task Force conducted an investigation at the
facility. In addition to sampling ground water monitoring wells,
several pre-RCRA solid waste management units were inspected.
- In August 1987, EPA conducted a RCRA Facility Assessment (RFA)
under the HWSA provisions. The RFA report was released in
September 1987. ,
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-16-
B. INVESTIGATIVE METHODS
Data gathering methods used for this investigation involved
four major areas: record reviews and facility personnel inter-
views, ground water sampling and analysis, audit of sampling
procedures, and investigations and inspections of on-site facility
operations and disposal areas. Record reviews, facility personnel
interviews, and on-site investigations were conducted by the
project leaders Mark Filippini and Donn Zuroski, EPA Region 9.
Both the ground water sampling and the sampling audit projects
were led by Frances Schultz of Region 9 Field Inspections Section.
A Project Plan was developed for the investigation by the project
leaders and includes a Sampling Plan developed by the Field Team
Leader. Laboratory audits, normally conducted during Task Force
investigations, were not done due to resource limitations.
However, the analytical laboratory used by 'the facility, Brown
and Caldwell of Pasadena, California, was audited in a previous
Task Force investigation of Casmalia Resources in 1986. The
Project Plan has been incorporated into this report by reference.
For a thorough review of the procedures used in this investigation
and for a comprehensive understanding of the results of this
report, the Project Plan should be consulted.
1. Facility Inspection/Record Review
The facility inspection involved three major areas: collection
and review of all pertinent data and documents relating to the
facility design and operation; interviews of facility personnel;
and inspections of facility units; operations and disposal areas.
In March 1987 Planning Research Corporation (PRC) Chicago,
Illinois, under contract to U.S. EPA Headquarters and the Task
Force, compiled an information/document package for the Hughes
Aircraft Facility. The PRC file consists of 14 volumes containing
a catalogue of all documents and correspondence regarding the
facility from EPA and State files. The PRC file was used as a
comprehensive review and reference document to aid in this investi-
gative process. Documents and records were also reviewed and
collected at the facility to verify information currently in
Government files and to supplement them with new information.
Documents requested of the facility were those known to be missing
from Government files, new information, documents not yet received
by the Agency, and documents of interest brought to our attention
through interviews with facility personnel. All document s_^re on
file with EPA Region 9.
Interviews of facility personnel and their contractors were
conducted throughout the investigation. The kickoff meeting, held
the first morning of the field investigation at the facility
offices, involved four facility representatives as well as Task
Force, Regional, and State representatives. Several other
interviews were held with selected facility personnel throughout
the investigation. All interviews were attended by State and/or
Region 9 Superfund representatives.
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-17-
Discussions from the meetings and interviews were documented
in field log books issued to each Task Force participant.
Notebooks were issued to Task Force, Versar, Regional and State
participants to document and log all activities observed and
conducted during the investigation. All notebooks were collected
at the end of the investigation, used in the report writing, and
are kept on file at Region 9.
Investigation of facility waste management units were also
conducted during the Task Force investigation. This included
current operating units, past disposal areas, and Superfund
sources. Between interviews with facility personnel, review of
aerial photographs, and walking and drive-through reconnaissance,
several previously undisclosed disposal areas, or Solid Waste
Management Units (SWMU's), were discovered.
This information was used to conduct a RCRA Facility Assess-
ment (RFA) as required by the RCRA permitting process. In August
1987 the Visual Site Inspection (VSI) portion of the RFA was con-
ducted by EPA contractor A.T. Kearney. The VSI was attended
by Region 9 Permits, Inspection, and CERCLA personnel, and State
personnel. The results of the RFA are presented in a report
developed by Kearney which was completed in September 1987.
Photo documentation of facility units and operation, Task
Force sampling operations, and facility sampling procedures was
conducted. Photography by Task Force representatives was prohi-
bited by the facility for security purposes. All photographs
were taken by facility representatives. Selected photographs were
then sent to the Task Force after security review. The photo
package sent by the facility is incorporated into the Sampling
Audit and Sampling and Documentation Reports by reference.
2. Sampling Audit
In order to assess the facility's ground water sampling
procedures, EPA audited a facility sampling demonstration given
by the facility sampling contractor, Hargis and Associates. The
sampling demonstration was limited to one well and two parameters
and was given on April 22, 1987. The audit included observa-
tion of sampling procedures, interviewing sampling personnel, and
collection of sampling-related documents.
The neutron probe system, used by the facility to meet the
conditions of the 1984 consent agreement with EPA, was also
investigated by the Task Force. A demonstration of the operation
of the probe system was arranged with the facility contractor who
operates the system. This audit included observation of the
probe procedures, interviewing the probe operators, collection
of pertinent documents, review of the operation plan, and photo-
documentation. Aldo Mazzella with EPA Environmental Systems
Monitoring Laboratory in Las Vegas conducted a review of the
neutron probe system for the .Task Force. His report is attached
as Appendix B of this report.
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-18-
3. Sampling Program
One of the objectives of the Task Force investigation at
Hughes Aircraft/Air Force Plant #44 was to sample selected facility
wells and analyze them for the RCRA indicator and Appendix IX
parameters, identified in Appendix A. The intent was to provide
an indication of the quality of the ground water beneath the site
in the vicinity of the RCRA units and to compare and confirm the
results with information provided by the facility.
All but one of the selected wells were CERCLA monitoring
wells, rather than RCRA wells. The selection of the wells was
based on an attempt to confirm past data and expand the number of
parameters analyzed for around the facility units. The selection
was not based on an attempt to determine releases from the RCRA
units. Due to improper well placement and construction, and
possible releases from SWMU's in the area, it would be impractical
to make determinations of releases from the regulated units
without further investigation.
From. April 20 to 23, 1987 six facility wells were sampled
(well locations are shown in Figure 5). In addition, five blank
samples and one replicate sample were taken, for a total of 11
samples. Split samples were provided to the facility. A four-
person sampling team from Versar and Planning Research Corporation
performed all the sampling.
The sampling activities were based upon the April 1987
Sampling and Analysis Plan (Schultz, 1987). Sampling procedures
are described in detail in the Sampling and Analysis Plan, Attach-
ment A of the Project Plan. Descriptions of the sampling protocol,
container and preservative details, shipping, and QA/QC procedures
are described in the Sampling Plan. The reader is referred to
the Sampling Plan and the Sampling Documentation Report, October
1987, for details of the procedures used during the investigation.
These reports are on file at the Region 9 office.
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• M-2B
M-41
^!J Location of formerly
used Percolation Bed
\
WASTE SHINE
EVAPORATION
BEDS
SLUOQC DRYING
BEOS
M-25
.1
• M-15
Figure 5
Relative; locations of wells sampled during Hughes/AFP £44 Task Force investigation
(Not to Scale)
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-20-
C. WASTE MANAGEMENT UNITS AND OPERATIONS
1. Current RCRA Units
The RCRA regulated units at Hughes/AFP |44 are process units
within the Industrial Wastewater Treatment Plant (IWTP). The IWTP
is designed to be a zero discharge facility designed to recycle 75%
of the (treated) industrial wastewater back into the industrial
water supply. The IWTP includes a control building, filter building,
two tank batch treatment systems, a sludge dewatering facility, and
a 33—acre secured area containing 15 holding ponds and 20 evaporation
beds (see Figure 5 above).
The following listed hazardous wastes are received at the IWTP:
spent cyanide plating bath solutions from electroplating operations
(F007); plating bath sludges from electroplating operations (F008);
and spent stripping and cleaning bath solutions from electroplating
operations (F009). In addition, two characteristic waste streams
containing chromium (D007) and lead (D008) are received at the IWTP.
The IWTP produces several liquid waste streams as well as
reclaimed water. The wastes include: waste brine from a reverse
oxidation (RO) system; scum and sludge from a dissolved air flotation
(DAF) system and reactor-clarifier units; treated alkaline waste;
treated acid waste; and filter backwash cleaning waste. The brine
from the RO system and the treated alkaline and acid wastes are
piped to the brine evaporation beds. The DAF sludge and scum,
reactor-clarifier sludge, and filter backwash cleaning waste are
piped to the sludge dewatering facility.
Batch Treatment Systems
There are two batch treatment systems at the IWTP. One is used
to treat concentrated acid waste (CAW), the other to treat concentrated
alkaline solutions (CAS). Both systems employ similar equipment and
processes. Both systems discharge treated waste to the waste brine
evaporation beds.
The CAW reduces Cr-VI to Cr-III using sulfur dioxide under
acidic conditions. The Cr-III is then precipitated out using
sodium hydroxide under alkaline conditions.
The CAS oxidizes cyanide to cyanate using chlorine under
alkaline conditions. The cyanate is then oxidized to carbon dioxide
and nitrogen gas using chlorine under alkaline conditions.
Waste Brine Evaporation Beds
Twenty double-lined evaporation beds are on line at the IWTP.
These beds receive waste from the RO system, treated alkaline and
treated acid waste, and waste monoethanolamine. Annual waste brine
production at the IWTP is estimated at 40 million gallons. Annual
salt accumulation in the beds is estimated at 0.1 - 0.2 inches/yr.
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-21-
The beds are constructed with two 100 mil High Density Poly-
ethylene (HDPE) membranes separated by a drainage net. Each bed
contains a leak detection system using a collector pipe fed by
the drainage net between the HDPE membranes.
Holding Ponds
Fifteen wastewater holding ponds are on-line at the IWTP.
These ponds store general industrial waste during periods of high
flow or IWTP shut down. The ponds have the same construction as
the brine ponds.
Sludge Dewatering Facility
This unit consists of a thickening tank and a plate and frame
filter press. Sludge and scum from the DAF, sludge from the
reactor-clarifier units, and backwash cleaning wastes are piped to
the thickening tank and then to the press. The filter cake is sent
to a hazardous waste landfill, the filtrate is sent to the DAF
clarifier.
2. Solid Waste Management Units (SWMU's)
Based on investigations conducted during the Task Force
inspection and a RCRA Facility Assessment (RFA) conducted in
August 1987 by A.T. Kearney, an EPA contractor, 164 Solid Waste
Management Units have been identified at the facility. Several
of these units are known to be contributing to ground water
contamination at the facility while many others are suspected or
could be potential sources of contamination. Several SWMU's
were discovered during the Task Force investigation that had not
been reported to EPA by the facility as is required under CERCLA.
Several problems were encountered during the RFA which made
it difficult to identify and characterize all the SWMU's at the
facility. In several areas EPA was denied access due to security
reasons. Recent construction and removal operations also obscured
attempts to identify units. The facility's reluctance to provide
information on several areas also made investigations difficult.
It was also noted that the not all SWMU's were investigated
under the Air Force Remedial Investigation (RI) and IRP. It was
concluded in the RI that no continuing sources of ground water
contamination existed at the facility despite the existence of
over 100 SWMU's.
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-22-
Some of the major solid waste management units so far identified
at the facility include the following:
a) Twelve unlined pits which received methylene chloride, TCE,
TCA, other solvents, paint sludges and thinners;
b) Unlined wastewater ponds which received plating rinsewaters,
cooling tower blowdown, concentrated solutions of cyanide and
chromium;
c) Two sludge drying beds. One lined with a plastic membrane, the
other lined with bentonite. These beds received wastewaters
containing chromium, cyanides, cadmium, silver, lead, copper
compounds, and heavy metal sludges;
d) Unlined drainage channels which led to the Arroyo Wash at the
Nogales Highway. These channels received wastewaters from the
unlined wastewater ponds as well as chrome and cyanide-free
rinsewater, acid solutions after batch treatment, and batch
treated chrome and cyanide containing wastewaters, paint booth
wash, cooling blowdown;
e) Three fire training areas where alcohols and flammable solvents,
including acetone and MEK, were discharged directly onto the
ground;
f) An unlined explosive pit where ordnance was detonated;
g) Numerous below and above ground storage tanks containing
solvents, oils, gasoline, and diesel fuel.
Based on the results of the work performed under the RFA,
several inactive units appear to warrant soil sampling and
investigations to verify contamination and to delineate the
horizontal and vertical extent of contamination. These are:
Inactive Landfill Site 1 (Unit 100), Inactive Landfill Site 2
(Unit 101), Inactive Surface Impoundment Site 4 (Unit 103),
Inactive Surface Impoundment Site 5 (Unit 104), Inactive Fire
Training Area East of Building 811 (Unit 107), Inactive Fire
Training Area in FACO Area (Unit 108), Inactive Fire Training
Area West of Building 801 (Unit 109), Magnesium Disposal-Ignition
Area (Unit 110), Explosion Pit (Unit 111), Trash Pile (Unit 112),
Fill Material Area (Unit 113), and Ditches (Unit 164).
All the SWMU's at the facilty must be addressed, as well as
any ground water contamination, before a final permit can be
issued under RCRA. These units must be addressed either under
RCRA or CERCLA authorities.
Details on all the SWMU's at the facility are presented in
the Hughes/AFP 144 RFA report developed by A.T. Kearney, September
1987. This report is part of the Region 9 file on Hughes Aircraft,
Air Force Plant #44.
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-23-
D. SITE GEOLOGY/HYDROGEOLOGY
1. Geomorphology
Hughes Aircraft/Air Force Plant #44 lies 15 miles south of
downtown Tucson (latitude 32° 06' 00", longitude 110° 55' 44").
The facility is bordered to the north by Tucson International
Airport, bordered to the west by the San Xavier Indian Reservation,
and bordered to the south and east by undeveloped land.
The altitude of Hughes/AFP #44 is approximiately 2,600 feet
above mean sea level (msl). This facility lies on relatively
flat terrain with 60 feet of relief over two miles (maximum slope
of less than one percent towards the northwest).
The facility is located in the Tucson basin, which is within
the Sonoran Desert section of the Basin and Range physiographic
province. This province is generally characterized by north to
northwest trending fault-block mountains separated by either
desert plains or broad gently sloping alluvial basins. The basin
covers approximately 1,000 square miles. To the north and east
are the Santa Rita, Empire, Rincon, Tangue Verde and Santa Catalina
Mountains. To the west are the Sierrita, Black, and Tucson
Mountains (USGS 86-4313). The eastern and northern ranges are at
altitudes between 6,000 and 8,000 feet above msl, with peaks
greater than 9,000 feet above msl. The ranges to the west are
between 3,000 and 6,000 feet above msl.
The Tucson basin is drained by the Santa Cruz River, which
flows to the northwest through the basin. Major tributaries to
the Santa Cruz River in the vicinity of Hughes include Julian
Wash, Pantano Wash, Arroyo Wash, and Rillito Creek. All the
tributaries flow to the west or northwest, toward the Santa Cruz
River. These drainage ways are dry most of the year, flowing
only during and immediately after rainstorms.
Surface flow on the plant property is controlled by two
intermittent streams, a series of drainage channels, and a sub-
surface storm drain system (SAIC, 1985). General surface drainage
is west and northwesterly toward the Santa Cruz River. There are
two intermittent streams on the plant property, one through the
southern portion of the property, the other through the northwest
portion of the property. These streams meet and drain to the
west toward Nogales Highway. The storm drain system at Hughes/
APF #44 directs surface runoff from the main facility area to
drainage channel which runs west, in the direction of the river
(SAIC, 1985).
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-24-
2. Geology
The mountains surrounding the Tucson basin are comprised of
crystalline igneous, metamorphic, volcanic, and sedimentary
rocks. Ages vary from Precambrian to late Tertiary (SAIC, 1985).
The basin is filled with several thousand feet of sediments
(alluvium) which are derived from the surrounding mountain ranges
(Figure 6). These deposits are considered to be less than 13
million years old. The major alluvium sources consist of granite,
granite-gneiss, schist, andesite, basalt, and limestone. The
sediments are interbedded locally with volcanic flows, agglomerates,
and tuffaceous sediments.
These basin fill deposits are characterized by the following:
a) They retain their original depositional slopes
b) They contain facies relationships largely consistent with
present configurations of the basin.
c) They are only locally deformed by tectonics.
d) They rest upon a Middle Miocene unconformity.
The basin fill includes four sediment groups (Figures 7 & 8)
1) surficial deposits
2) the Fort Lowell Formation
3) the Tinaja Beds
4) the Pantano Formation
Surficial Deposits
The surficial deposits are thin, discontinuous terrace gravels,
stream channel and floodplain deposits which overlie the Fort
Lowell Formation. These deposits are mainly gravel, gravelly
sand, and localized sand and sandy silt. These deposits range in
thickness from featheredge to several tens of feet.
Fort Lowell Formation ^--==-— .
This formation, overlying the Tinaja Beds, is comprised of predomi-
nantly silty gravel near the basin margins, grading to a silty
sand and clayey silt in the center of the basin. The Fort
Lowell Formation is 300 to 400 feet thick in the center of the
basin (Hargis & Montgomery, 1982). This formation is estimated
to be of Quaternary age.
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-25-
£ Air Force Plant
44
Source: CH2M Hill. 1982
Figure 6 Geologic Map Showing Distnbutipn and
Estimated Thickness of Unconsolidated Sed.ments
in the Area of AFP 44. Tucson. Ar.zona
-------
Figure 7 Location of Cross-Section Line A-A' at AFP 44. Tucson. Arizona (see Figure 8
for cross-section)
-------
2160
Eiiplanation
llns.lllll.lKvl /mil!
r ~~ 1 Alii tii,il«n| imMiws til VMfly I l
II iHl I i*vrl I in I
N)
-J
',,..„.. liMI l'«l,
Figure S Geologic Cross-Section A-A' Across AFP 44. Tucson. Arizona
(see Figure 7 for cross-section location)
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-28-
Tinaja Beds
The Tinaja Beds range in thickness from a featheredge to greater
than 5,000 feet. These beds are comprised of sand and gravel at
the margins of the basin. In the center of the basin they grade
to gypsiferous, clayey silt and mudstone.
Pantano Formation
This formation is a silty sandstone that includes gravel with
interbedded volcanic flows and tuffaceous sediments. The Pantano
formation is estimated to range from a few hundred to 1,000 feet
(Hargis & Montgomery, 1982). This formation was dated as middle
Tertiary by Finnel (USGS, 86-4313).
The central part of the Tucson basin is a triangular down-
faulted block which is bounded by the Santa Cruz fault, an unnamed
fault running parallel to Rillito and Tanque Verde Creeks, and
another unnamed fault trending northeast through the basin (Hargis
& Montgomery, 1982).
The alluvial deposits at Hughes/AFP #44 vary due to differ-
ences in depositional environments. Fine grained sediments such
as silts and clays were deposited as river mouth alluvial fans or
on terraces at low water velocities during flood stages as rivers
overflowed their banks. Coarser materials such as sands and
gravels were deposited in stream beds. These sediments were
distributed laterally as streams changed course (SAIC, 1985).
Hargis and Montgomery (1982) found the upper 175 to 225 of
alluvium at the facility to correlate to the Fort Lowell Formation.
The underlying sediments have been drilled to a depth of 600 feet
and appear to correlate with the Tinaja Beds. The entire thickness
of the Tinaja Beds has not been penetrated by drilling at the
facility. The depth of the underlying Pantano Formation is unknown.
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-29-
3. Soils
The Soil Conservation Service (SCS) has identified five distinct soils
in the vicinity of Hughes:
1) The Cave series, a shallow, well-drained, moderately
permeable soil, commonly formed in gravelly mixed alluvium on
low hills and valley fill;
2) The Yaqui series consists of deep, well-drained soils formed in
mixed, calcareous alluvium on alluvial fans;
3) The Nickel series consists of deep, well-drained soils formed on
dissected terraces in alluvium that originated from mixed rock sources;
4} The Sahuarita series consists of deep, well-drained soils formed
on alluvial fan terraces in mixed calcareous alluvium; and
5) The Riggs series consists of deep, moderately well-drained, low
permeability soils that form in mixed alluvium on alluvial fans
and flood plains.
4. Hydrogeology
The regional aquifer in the Tucson basin has been classified
into three zones by Hargis & Montgomery (Phase I, 1982), upper
zone, a lower zone, and an area where the two merge called the
undivided aquifer. Under the facility Hargis & Montgomery claim
the aquifer is divided into an upper zone and a lower zone,
separated by an extensive clay confining layer (aquitard). Where
this confining layer does not exist, the aquifer is classified as
undivided. The undivided portion of the aquifer is reported not
to exist under the facility. In addition to the aquitard there
is a perched lens of approximately 100 acres under the facility.
The upper zone and the lower zone are assumed to be hydrogeologically
connected. Only regional site characerization has been conducted,
and no site characterization report has been submitted for the RCRA
Part B permit application.
a. Water bearing zones
Perched Zone
This zone lies approximately 60-95 feet below the surface. The
thickness of the perched lens varies from approximately 1 to 5
feet. This zone is comprised primarily of sandy clay and clay.
The sandy clay pinches out north of the plant. Water levels in
this zone appear to fluctuate in response to rainfall and runoff
events. Hargis and Montgomery (1987) have concluded that this
lens is recharged from percolation of runoff along a network of
arroyos and from runoff ponding in low areas.
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-30-
Upper Aquifer Zone
The upper aquifer zone extends approximately from 100 to 200 feet
below the surface. This zone is comprised of fine-to-coarse sand
with gravel, occassional lenses of cobbles, and lenses of clay
(Hargis & Montgomery, 1982).
Lower Aquifer Zone
The lower aquifer zone extends from 200 feet to a depth of
approximately 600 feet below the surface. This zone is comprised
of clayey sediments interbedded with lenses of sand, sandy clay,
and clayey sand.
b. Occurrence and Movement
Ground water occurs under unconfined conditions in both the
perched zone and the upper zone of the regional aquifer system.
In the lower zone of the regional aquifer, groundwater occurs
under semiconfined conditions (Hargis & Montgomery, 1982).
The direction of flow in both the upper and lower zones beneath
the facility is to the northwest. The hydraulic gradient for the
upper zone is approximately 15 feet per mile. In the perched zone
groundwater flow radiates away from a central mound.
Ground water is the principle source of irrigation, municipal,
industrial, and domestic water in the Tucson basin. Pumping
rates have exceeded recharge rates, and substantial declines in
water levels have occurred in the northern and southwestern parts
of the basin. Most of the recharge to the ground water flow
system in the alluvial aquifer is derived from infiltration along
the major stream channels and from mountain-front recharge.
5. Climate
The climate of the Tucson area is characterized by warm semi-
arid conditions associated with low latitude deserts. Mean annual
precipitation is approximately 11.2 inches,. Mean relative humidity
is 37.5%. The net precipitation for this area (mean annual
precipitation minus mean annual evaporation) is minus 55 inches
per year. The annual average temperature is 68°F.
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-31-
E. INTERIM STATUS GROUND WATER MONITORING
1. Current Monitoring System
Over 100 ground water monitoring wells currently exist at the
Hughes/AFP #44 facility; however, not all are designated as RCRA
monitoring wells. The first RCRA Part B Permit Application was
submitted in August 1983. In that application the facility claimed
an exemption from the ground water monitoring program because the
impoundments were lined. The facility supported the waiver with
data obtained from a neutron probe system. Consequently, the
application contained no interim status ground water monitoring
data.
In response to an inspection conducted in August 1982, a
complaint was issued to the facility in June 1983 asserting that
the neutron probe system was not capable of detecting leakage
from the ponds and that the facility could not support the claimed
ground water monitoring waiver. EPA also determined that the
neutron probe system did not constitute an acceptable alternative
ground water monitoring system.
In the intervening months, EPA Region 9 staff and the facility
agreed upon improvements to the neutron probe system and installa-
tion of the 19 S-series wells to monitor the perched zone. This
allowed the facility to use the perched zone/neutron probe system
as an alternative ground water monitoring system. The facility,
however, refused to pay the requested $17,000 penalty. This led to
a referral of the case to the U.S. Department of Justice (DOJ) in
March 1984 and an Administrative Hearing, with an Administrative
Law Judge in May 1984.
The results of the Administrative Hearing upheld Hughes'
contention that, because they were acting under contract to the
Air Force as a GOCO, they were considered to be a federal facility
and therefore not subject to any fines levied by EPA. Consequently,
the DOJ referral was also retracted and a Federal Facility Compliance
Agreement (FFCA) was signed with no penalty.
In July 1984, EPA issued the first NOD for the August 1983
Part B submittal. The revised Part B was received in December
1984. An additional Part B revision was submitted in January
1987; however, it was a result of process changes at the facility
and not a NOD. The ground water portion of the January 1987
Part B was identical to the December 1984 version. That version
of the Part B application was the one in effect at the time of
the Task Force investigation. —-^ „> _ ___
The present RCRA monitoring system consists of 26 perched
zone wells (Figure 9) and 30 neutron probes (Figure 10). The
FFCA requires the facility to sound perched zone wells B3, B6,
B7, B9, B19, C3, P8, and all S-series wells monthly. Whenever a
well shows a water level rise of over one foot, that well must be
-------
I 1 1 1
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-------
EXPLANATION
N-2
NEUTRON LOGOINO HOLE
N-23
N-24
Drainage Channel
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HANI
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FIGURE 10 LOCATION MAP FOR NEUTRON LOGGING HOLES
-------
-34-
sampled for chromium, nickel, copper, and sulfates. All of the
above wells are required to be sampled (if not dry) on a quarterly
basis. No statistical analysis has been conducted on the data
generated from these samples. The neutron probe system is also
monitored on a quarterly basis.
Perched zone wells generally consist of 2 or 3 inch PVC pipe,
capped and slotted at the base with pea gravel filter pack, and
cemented inside a 6 inch surface casing (see Figure 11). These
wells do not meet current design or construction standards for
RCRA monitoring wells. The wells contain excessive screen lengths,
contain no annular seal, do not contain a filter pack matched to
the aquifer material, and do not monitor the uppermost aquifer
system as is required. The monitoring system is also not based
on an adequate hydrogeologic site characterization plan.
The neutron probe system consists of 30 neutron logging holes.
The neutron holes are constructed around the 20 brine evaporation
beds and the 15 holding ponds. Fifteen probes surround the evapo-
ration beds, 14 probes surround the holding ponds. The quarterly
logs are compared to previous logs to determine if there has been
an increase in soil moisture content.
The effectiveness of the system is based on the assumption
that any flow from a pond leak will be in the horizontal direction.
The radius of influence for neutron probes is very limited. Any
liquid that leaves the ponds must come within the radius of
influence of the probe in order to be measured. The probes are
logged on a quarterly basis, so the assumption is that any migrating
liquid will move horizontally, and will remain in the unsaturated
zone until the the logging event.
Review of the system by technical staff of the EPA Environmental
Monitoring Systems Laboratory (EMSL) in Las Vegas has revealed the
system to be inadequate and undeinonstrated as to its capability
to meet its designed intent. It was determined that a number of
aspects of the neutron probe system need to be investigated before
the system could be considered acceptable for a leak detection.
The effects of the casing material and grout on the probe
sensitivity and detectability has not been determined. The
cement used in the annulus of the access tube contains about 33%
water which affects the sensitivity of the system. It should
also be established that no leaks existed from the ponds before
the monitoring of the system was initiated. Since all the access
tubes were not in place before the evaporation ponds, it cannot
be determined what pre-pond background conditions were and whether
existing log moisture contents reflect existing long term leaks.
The system also relies on the existence of continuous layers of
clay and caliche to produce lateral movement of releases in the
vadose zone. The continuity of these layers had not been estab-
lished, nor has any direction been suggested for this lateral
movement. Finally, some modeling of unsaturated zone flow is
needed to provide a leak detection confidence level for the
system. The complete EMSL report is attached as Appendix B.
-------
-35-
DEPTH BELOW
LAND SURFACE
IN FEET
•0-
•100-
X
i
o
w
I *J
Sx
\
•" STEEL CAP
PADLOCK
2" THREADED PLUG
•«" STEEL CASINO (traffic protection)
•CONCRETE SEAL
•CONCRETE. SURFACE SEAL
•30" BOREHOLE
•2" PVC
•NATIVE SOILS (DRILL CUTTINOS):
Clayey Milt placed at bottom,
manor material placed in upper
portion* of boreftoie
•PEA 3RAVEL, '/," TO V,"
•PERFORATIONS' l" s '/,'
nerixantal slatv, «/foct
•Z' OlAMCTtR PLUa
FIGURE 11 SCHEMATIC DIAGRAM OF MONITOR WELLS
CONSTRUCTED IN THE PERCHED ZONE (From Hargis, Phase II)
-------
-36-
2. Sampling and Analysis Plan and Field Procedures
The sampling demonstration given by the facility at well
M-2A as part of our sampling audit cannot be extrapolated to a
full-scale sampling effort because of the limited number of field
conditions and procedures actually observed. A detailed review
of the sampling procedures observed during the audit is provided
in the Ground Water Sampling Audit report prepared by Frances
Schultz, April 1988. As with the other supporting documents
and reports/ it is incorporated into this report by reference and
is part of the Task Force file.
The sampling procedures conducted by the facility and their
contractor were generally inadequate. Deficiencies included
the following:
- The well was not inspected prior to sampling (animal borings
at the well pad were observed by the auditor)
- The water level indicator was not decontaminated after
samplings.
- Depth to water and depth to bottom of well (sounding) is
not generally taken at every sampling event prior to purging.
- Gloves were not worn throughout most of the purging and
sampling procedure.
- Casing volume (used to determine purge volume) was calculated
using historical data rather than a field measurements.
- Purge water (potentially a hazardous waste) has been disposed
of onto the ground in the past.
- The bailer line was observed to contact the ground during
the bailing process.
- A ground covering was not used around the base of the well.
- Field parameters were not measured in quadruplicate as
required in 40 CFR 265.93(b).
- PVC bailers were used for purging and sampling, rather than
bailers made of inert materials. Bailers were not constructed
to minimize sample^disturbance.
- Volatile organic compounds were collected last and allowed
to aerate as water was poured from bailer.
- Samples were not sent to the lab as "blind". Identifica-
tion of the well was provided on the labels, giving the
lab the opportunity to compare earlier results and possibly
influence their analysis.
-------
-37-
- Non-reproducible custody seals were not used.
- Thorough logbooks were not kept before and during field
work.
The sampling procedures used by the facility and it's
sampling contractors must be corrected before the data collected
by the facility can be considered unbiased and representative of
the ground water.
-------
-38-
F. TASK FORCE DATA COLLECTION/RESULTS
1. Sample Collection Methods
In order to determine the quality of the ground water beneath
the facility, selected wells around the RCRA regulated units were
sampled. Between April 20 and 23, 1987, EPA sampling contractor,
Versar Inc., sampled six facility wells. The list of wells
sampled during the investigation, including dates and times of
sampling, is provided in Table (1).
The sampling points were selected during a preliminary
meeting of State and Task Force personnel. Selection was made
based on well location, construction, screen interval, and previ-
ous water quality data in order to obtain samples most indicative
of potential ground water contamination. The sampling was not
meant to establish any releases from the regulated units. Well
placement and construction, as well as the existence of solid
waste management units in the area, precluded the Task Force from
being able to make meaningful determinations of releases from the
data.
The wells chosen for this sampling effort include five wells
which reach the upper zone of the regional aquifer: two wells
upgradient from the industrial wastewater treatment plant (IWWTP)
ponds and three wells downgradient from the ponds. The sixth
well is screened in the perched zone, upgradient from the ponds.
The wells screened in the regional aquifer are part of a
group of 47 M-series wells that were installed into the upper or
lower zone of the regional aquifer (Figure 12). The wells were
installed in 1981, '82 and '84 as part of the Superfund investiga-
tions at the site. Wells M-15 and M-25 represent wells upgradient
of the units, and wells M-2B, M-41 and M-9 represent wells downgrad-
ient of the units. As mentioned, these wells are not designated
as upgradient or downgradient RCRA wells.
Well S-10 was chosen to provide an indication of the water
quality in the perched zone (see Figure 9). It was chosen because
of the high level of contamination previously found in the well
and the likelihood that sufficient water would be present in the
well to allow for adequate purging and sampling.
Samples were analyzed for RCRA Indicator Parameters and RCRA
Appendix IX parameters (see Appendix A). Samples for organic
analysis were sent to EMSI in Camarillo, California; samples for
inorganic analysis wera sent to Centec in Salem, Virginia; dioxin
and furan samples were sent to Compu-Chem in Research Triangle
Park, North Carolina; and radionuclide samples were analyzed at
Acculabs Research in Wheat Ridge, Colorado.
All the wells were measured prior to purging for depth to
the water table. That data is presented in Table 2. The wells
were purged using dedicated submersible impeller pumps, with
the exception of well S-10 which was purged using a bailer.
-------
-39-
Table 1
SAMPLING DATA
WELL t
S-10
S-10
M-2B
M-9
M-15
M-25
M-41
M-41
(Dupli-
cate)
SAMPLE *
MQA 870
FAC 29
MQA 870
FAC 29
MQA 878
FAC 35
MQA 872
FAC 31
MQA 867
FAC 27
MQA 869
FAC 28
MQA 871
FAC 32
MQA 876
FAC 34
DATE
4/21
4/22
4/23
4/23
4/21
4/21
4/23
4/23
TIME
17:10 -
18:15
14:22 -
15:44
15:03 -
16:26
10:34 -
11:26
10:40 -
11:30
14:40 -
15:40
9:44 -
12:18
9:44 -
12:18
PARAMETERS
METHOD COLLECTED
3" Teflon VQA(2)*, PCC, PCK,
Bailer TOX, Ext. Ccg. (3),
Total metals,
Dissolved metals,
TOC
" Ext. Org. (3),
Dioxins/Furans (2),
Phenols, Cyanide,
Anions, Sulfides,
Radionuclides
(partial).
Facility's All
dedicated
submersible
impeller
punp
All
All
All
All
All
*Numbers in parentheses indicate the number of sanple containers filled.
-------
AIR FORCE LAND
EXPLANATION
• WELL* PERFORATED
IN THE UPPER AQUIFER
• WELLS PERFORATED
IN THE LOWER
AQUIFER. REGIONAL
UNDIVIDED AQUIFER
OR COMPOSITE UPPER
AND LOWER AQUIFERS.
•M-
o.a
MIIE8
f MILE
Figure 12
LOCATION OF WELLS
SAMPLED IN THE
TUCSON AIRPORT AREA
TUCSON AIRPORT AREA •
-------
-41-
Table 2
WELL *
S-10
M-2B
M-9
M-15
M-25
M-41
SAMPLE f
MQA 870
FAC 29
MQA 878
FAC 35
MQA 872
FAC 31
MQA 867
FAC 27
MQA 869
FAC 28
MQA 871
FAC 32
DATE
4/21
4/23
4/23
4/21
4/21
4/23
PURGE EATA
DEPTH TO
WATER
TIME (ft.)
11:05 - 95.51
12:20
14:25 - 106.88
14:37
9:35 - 111.93
10:18
9:00 - 123.51
9:30
14:15 - 117.05
14:40
8:55 - 119.68
9:42
CASING PURGE
VOLUME VOLUME
(gal.) (gal.)
3.4 5
56 80
57.2 175
30.9 98
40.9 147
41.2 150
-------
-42-
The submersible pumps were operated by a portable generator.
Operation of the generator and hookups to the submersible pumps
were conducted by facility employees. Purge water was
discharged into 55-gallon drums for measurement and eventual
disposal. The purge water was shipped and disposed of as a
hazardous waste due to the Superfund off site disposal policy.
As the ground waters were known to contain contaminants from a
Superfund site and the operations were funded by EPA, it was
necessary to dispose of the purge water as a hazardous waste at
an acceptable RCRA disposal or treatment facility. USPCI in Utah
was selected as the most cost effective disposal facility meeting
the requirements of the Superfund off site disposal policy (May
6, 1985 memorandum from Jack McGraw).
The Task Force team attempted to purge three casing volumes
of water from each well, if possible. This was achieved on all
wells except S-10 and M-2B. Well S-10 was purged to dryness while
M-2B was purged of 1.4 casing volumes due to confusion in the
reported casing diameter. Casing volumes were calculated using
the casing size and the length of the water column. Actual purge
volumes are presented in Table 2.
Wells were sampled as soon after purging as possible. A lag
time of less than three hours was attempted at all wells. Well
S-10 was slow to recover and required that sampling be conducted
over a two-day period. At well S-10 some parameters were collected
the day of purging and others were collected the following day
after recovery (see Table 1).
Sample parameters were collected in priority order as designa-
ted in the Sampling Plan with the exception of two wells where
the order was altered for well-specific reasons. The list of
sample parameters, volumes, containers, and preservation methods
are given in priority order of collection in Table 3.
Samples were shipped the same day or the day following
collection by next-day delivery Federal Express to the respective
labs. Complete details for sample collection, preservation, and
shipment are given in the Sampling Plan and Sampling Documentation
Report. The reader is referred to the documents for further
elaboration on procedures used in the field.
2. Results of Task Force Data
Results of the Task Force data are provided in Table 4 ..
The Task Force data on six sampling points confirmed the identi-
fication of a total of five different organic compounds in the
Hughes wells. In addition, two unknown hydrocarbons and elevated
radionuclides were detected in well S-10.
-------
-43-
Table 3: Aliquots and Containers for Water Samples
to be Collected at Hughes Aircraft, Tucson, Arizona
arameters
f / Type of
Sample Container
Preservation
Comments
olatile Qrganics
•urgeable Organic Carbon }
(POC) )
>urgeable Organic Halogens)
(POX) )
Retractable Organics
Acid Extractables )
Base/Neutral Extractables)
Pesticides/PCBs )
Herbicides
Dioxins/Furans
Metals (Total)
Metals (Dissolved)
Total Organic Carbon
(TCC)
Total Organic Halogens
(TOX)
Phenolics
Sulfide
Cyanide
Radionuclides
Gross Alpha
Gross Beta
Radium
2 / 40 ml glass vials
teflon septa
1 / 40 ml glass vial
teflon septa
1 / 40 ml glass vial
tefon septa
Cool, 4°
Cool, 4°
Cool, 4°
8/1 liter anber
glass bottles
Cool, 4°
1/1 liter Polyethylene HNO3 to pH<2
bottles Cool, 4°
1/1 liter Polyethylene HNO3 to pH<2
bottles Cool, 4°
1 / 4 oz glass jar
1/1 liter amber
glass bottle
1/1 liter amber
glass bottle
1 / 4 oz glass
bottle
H2S04 to pH<2
Cool, 4°
Cool, 4°
No Head Space
No Head Space
No Head Space
Filter prior
to preservation
No Head Space
H2SO4 to pH<2
Cool, 4°
Zinc Acetate, NaOH
Cool, 4°
1/1 liter Polyethylene NaOH to pH>12
bottle Cool, 4°
1/1 gallon Cubetainer )
or )
4/1 liter Polyethylene)
bottles )
to pH<2
Anions
1/1 liter Polyethylene Cool, 4*
bottle
-------
Table 4. Summary of Organic and Inorganic Parameters Analyzed from April 1987
Ground Water Task Force Sampling at Hughes Aircraft, AFP 44.
WELT/SAMPLE
COMPOUND
(ppb unless noted)
1 ,1-Dichloroethene
Trans-1 , 2-Dichloroethene
Trichloroethene
Caprolactam
1-Hexanol, 2-Ethyl
Unknown Chlorinated
Hydrocarbon
Unknown Hydrocarbon
Metals(Total/Dissolved)
Aluminum
Barium
Calcium (ppm)
Chromium
Copper
Iron
Lead
Magnesium (ppm)
Manganese
Nickel
Potassium
Sodium (ppm)
Vanadium
Zinc
Indicators
Chloride (ppm)
Nitrate Nitrogen
Sulfate (ppm)
POC
POX
TOC
TOX
pH
SpjC (urn/cm)
Total Radium (pCi/1)
Gross Alpha "
Gross Beta "
M-15
/84
/43.7
/9.8
/35.3
/15
_/577
6.6
500
35
34
7.5
400
0.1+0.2
2+2
3+3
M-25
95
/83
/42.3
/9.4
/6
/36.9 H
^/423
7.5
500
32
40
62
7.0
360
0.2+0.3
4+3
4+3
S-10
140
1100
20
9
8
20
/226
/219
/102
/281
/23.4
/16
/49.2
/455
52
11000
143
460
1282
2300
725
7.4
700
33+4
180+90
350+90
M-9
79
/5U7
/ll
V11.5_
/34.9
/16
14
900
44
62
7.5
390
0.2+0.2
4+3
1+2
M-2B
22
230
223/
99/95
55.7/68.5
46/37
32/24
953/
16/5.2
12.4/15
29/
1610/
30.4/38.3
642/753
22
2300
76
110
208
268
7.1
500
0.1+0.2
9+4
4+3
M-41
230
13
1800
/96.3
/69
V.21-5 ,
/984
/57
/861
40
3100
140
580
1426
914
7.4
700
0.2+0.3
7+4
1+3
M-41
Duplicate
210
1500
62/
60/64
79.9/96.2
68/74
104/
5.1/2.5
17.7/21.2
30/
2400/1370
46.3/56.1
717/853
39
3100
142
560
1714
924
7.4
700
0.2+0.3
4+4
2+3
EQUIP
BLANK
154/
16/
6.3/
0.26/
1180/
0.25/
35/
54
0.1+0.2
0+1
0+2
EQUIP
BLANK
127/
0.29/
1360/
/17
30
16
0.0+0.2
1+1
-1+2
FIELD
BLANK
78
-0.1+0.1
0+1
-1+2
TRIP
BLANK
/17
48
-------
-45-
Trichloroethene (TCE) and 1,1-dichloroethene (DCE) were found
in most wells (which is consistent with CERCLA sampling results).
TCE was found in all wells except M-15 ranging in levels from 79
to 1800 ppb. DCE was found in wells S-10, M-2B and M-41 at
levels ranging from 22 to 230 ppb. Trans-1,2 dichloroethene was
also detected in well M-41.
Well S-10 was found to be the most heavily contaminated well
where, in addition to TCE and DCE, Caprolactam (20 ppb), 1-Hexanol,
2-Ethyl (9 ppb) and two unknown hydrocarbons were detected.
Levels of metals and many indicator parameters were also higher
in S-10 than surrounding regional aquifer wells. Radionuclide
levels in well S-10 were dramatically higher than all other wells
sampled. Total radium was reported at 33^4 pCi/1, gross alpha
was reported at 180+^0 pCi/1, and gross beta was reported at
350_+90 pCi/1. These levels of radionuclides were two orders of
magnitude higher than surrounding wells. It cannot be determined
if these levels are naturally occuring or reflect some unknown
source. Levels of barium, chromium, and nitrate nitrogen were
also elevated in well S-10. Dissolved barium was reported at 219
ppb, dissolved chromium was reported at 281 ppb, and nitrate
nitrogen was reported at 11,000 ppb.
-------
-46-
REFERENCES
Project Plan, Hazardous Waste Ground Water Task Force, Hughes
Aircraft, U.S. Air Force Plant #44, Tucson, Arizona. Mark
Filippini and Donn Zuroski, USEPA Region 9, April 1987.
Ground Water Sampling Plan, Hughes Aircraft, U.S. Air Force
Plant #44, Tucson, Arizona, Frances Schultz, USEPA Region 9,
April 1987.
Ground Water Sampling Audit Report, Hughes Aircraft, Tucson,
Arizona, Frances Schultz, USEPA Region 9, April 1988.
Sampling and Documentation Report, Hughes Aircraft Company,
Tucson, Arizona, Frances Schultz, USEPA Region 9, October 1987.
Installation Restoration Program Phase I—Records Search, Air
Force Plant 44, Tucson, Arizona, Science Applications Interna-
tional Corp., October 1985
Annual Static Water Level Basic Data Report, Tucson Basin and
Avra Valley, Pima County, Arizona, City of Tucson, Tucson Water,
Planning Division, 1981
Results of the Tucson Airport Area Remedial Investigation, Phase I,
Volume I, Summary Report, Arizona Department of Health Services,
Phoenix, Arizona September 1985
Results of the Tucson Airport Area Remedial Investigation, Phase I,
Volume II, Contaminant Transport Modeling, Arizona Department
of Water Resources, Hydrology Division, November 1985
Distribution and Movement of Trichloroethylene in Ground Water in
the Tucson Area, Arizona, U.S. Geological Survey, Water-Resources
Investigations Report 86-4313
Summary of 1986 Hydrologic Monitoring Program, U.S. Air Force
Plant No. 44, Tucson, Arizona, Volume I, Hargis and Associates
Inc., June 1987
Phase I Investigation of Subsurface Conditions in the Vicinity of
Abandoned Waste Disposal Sites, Hughes Aircraft Company
Manufacturing Facility Tucson, Arizona, Volume I, Hargis and
Montgomery, Inc., January 1982
Phase II Investigation of Sublurface Conditions in the Vicinity
of Abandoned Waste Disposal Sites, Hughes Aircraft Company
Manufacturing Facility Tucson, Arizona, Volume I, Hargis and
Montgomery, Inc., March 1982
Draft Remedial Action Plan, United States Air Force Plant No. 44,
Tucson, Arizona, April 10, 1985
-------
RCRA INDICATOR PARAMETERS
Anions Cyanide
Phenols Radium
TOC Gross Alpha
TOX Gross Beta
POC Turbidity
POX Specific Conductance
Metals - Dissolved pH
Metals - Total
-------
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APPENDIX B
Review of Neutrom Probe System at Hughes Aircraft
Report from Environmental Monitoring Systems
Laboratory - Las Vegas
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SB
,
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY-LAS VEGAS
P.O. BOX 93478
LAS VEGAS. NEVADA 89193-3478
(7O2/798-210O • FTS 545-210O)
DEC 2 2 1327
SUBJECT: Review of Neutron Probe System at Hughes Aleraft Facility
•£r*-~ - X4 xy^g"^7'
FROM: Aldo T. Mazzella c —— / /• /^g_ •_ -^
Geophysicist
Aquatic and Subsurface Monitoring Branch
Advanced Monitoring Systems Division
TO: Donn Zuroski
Field Operations Branch
Toxics and Waste Management Division
Region 9
I have reviewed the five reports on the Neutron Probe Monitoring System
for moisture detection at the Hughes Aircraft facility and have discussed
them with Eric N. Koglin, a hydrologist in our Branch. My review comments
are attached.
Attachment
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Review of Neutron Probe System for Hughes Aircraft Facility, Tucson, Arizona
I have reviewed the following five reports on the neutron probe system
for the Hughes Aircraft facility:
1) "Construction and Testing of Pilot Neutron Logging System Hughes Aircraft
Company Manufacturing Facility Tucson, Arizona," December 18, 1981;
2) "Results of Additional Testing Pilot Neutron Logging System Hughes Aircraft
Company Manufacturing Facility Tucson, Arizona," April 19,1982;
3) "Results of Construction and Testing of Neutron Logging System Hughes
Aircraft Company Manufacturing Facility Tucson, Arizona," March 3,1983;
4) "Evaluation of 1983 Quarterly Neutron Logs, U.S. Air Force Plant
No.44," June 22, 1984;
5) "Results of Quarterly Neutron Logging January 1987 Hughes Aircraft Company
Tucson, Arizona," February 9, 1987.
My comments on the system can be divided into two separate areas, one
addresses the sensitivity of the neutron probe in the well completion
configuration, and the other area addresses the spatial variability of the
well locations and their ability to detect lateral movement of fluids in
the vadose zone.
One of the most important questions that the reports fail to address
is the sensitivity of the neutron probe when it is used in the wells at the
Hughes Aircraft facility. A conversion of the count rate to moisture
content is not presented. I plotted some of the data from report 12 of
neutron counts verses moisture content measured from core samples. This is
shown in Figure 1. Thirty-one points are plotted from wells N-l and N-5.
With the exception of four points at the highest moisture content, 21% and
above, the counts and core moisture content do not appear to be very veil
correlated. Figure 2 shows a similar plot for veil N-14 for January
26,1983, from report #3. Fifteen points are plotted. The correlation
appears to be better, however, there still appears to be some scatter and
outlier points.
The wells were completed with a .2 inch thick steel wall casing and a
1.125 inch thick cement grout in the annulus. The cement was about 33Z
water by weight. This is not an optimum well completion method for a
neutron probe moisture monitoring system. According to L.G. Vilson, 1980,
"The results of field studies by Halpenny (personal communication, 1979)
showed that bound water within grout markedly attenuates the flux of fast
neutrons from a source. Consequently, the sensitivity of a logger in
detecting water content changes in the surrounding formations is
correspondingly reduced." Based on this, it would seem imperative that the
radius of investigation and sensitivity of the combined probe-veil
configuration should be established. The sensitivity for detecting changes
in the moisture content should be evaluated for the different formations
and moisture content levels.
An additional consideration is that the neutron moisture logs only
indicate the water content of the soils. According to L.G. Vilson, 1980,
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"Water may move through a specific subsurface horizon without causing
a change in storage. Consequently, a neutron log may not manifest water
movement in this case." (See also Everett et al. 1984). The change in
water content in the various formations should be determined under dynamic
conditions with different levels of water flow. Since all the monitoring
wells were not in place before the evaporation ponds, one does not know the
pre-pond background conditions and whether the existing log moisture
contents may be reflecting an existing long term leak.
The initial work done at well N-l is of interest and concern. This was
a percolation test with a 700 gallons per day leak. "No apparent moisture
increases have been observed in neutron logging hole N-l." (reference 14
above). A number of conclusions and recommendations were made in report #4
to address this problem. Was this work conducted? I found no further
reports discussing this problem.
A number of pieces of information are not available in the reports. Is
the neutron probe an axial symmetric or decentralized tool, what was the
detector, and what is the diameter of the tool? This information would be
useful to help evaluated the system and the reproducibility of the
measurements. Some of the reproducibility questions are answered in the
last report of February 9, 1987, where various rate effects are evaluated.
However, the above questions should be answered.
The present system relies upon the existence of continuous layers of
clay and caliche to produce lateral movement in the vadose zone of any
leak. The continuity of these layers has not been established, nor has any
direction been suggested for this lateral movement. Is it assumed to be
isotropic? Many core logs were taken, however, there is not any discussion
about the continuity between the logs. No surface elevations were given for
the wells, and so I did not attempt to draw any cross sections. The
distance between the monitoring veils is on the order of 200 to 400 feet.
Without establishing a direction of flow in the perched zones, one must be
concerned about missing a leak because of the spatial location of the
wells. Some modelling of unsaturated zone flow is needed to provide a leak
detection confidence level for the monitoring well network system.
In report 14, increased moisture content is observed in holes N-23 and
N-24 at a depth of about 30 feet. This is attributed to lateral movement
of water from an arroyo due to "record breaking rainfalls." The distance
of the arroyo is indicated as "immediately north of neutron logging holes
N-23 and N-24." This distance should be specified. No moisture increases
were indicated in neutron hole N-22, about 100 feet to the south of wells
N-23 and N-24. One should be concerned and at least provide an explanation
for why this moisture was not observable at N-22 and possibly other holes,
such as N-12, 13, 14, 19, and 21. If a significant amount of water
observed at N-23 and N-24 did not reach N-22, 100 feet away, then, since
the ponds are over 200 feet across, is it equally possible that a leak in
the ponds would not reach holes N-23 and N-24?
Conclusions
There are a number of aspects of the neutron probe borehole
configuration that need to be investigated before the system could be
considered acceptable for a leak detection monitoring network. These are:
(1) The sensitivity of the neutron probe in the borehole for detecting
changes in the moisture content should be evaluated for the different
formations and moisture content levels. In particular, the effects of the
casing material and grout on the probe sensitivity and detectability
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should be evaluated.
(2) It should be established that no leaks existed from the ponds
before the monitoring of the wells was initiated. The change
in water content of the various formations should be determined
under dynamic conditions with different levels of water flow.
(3) The continuity of the clay or caliche layers throughout the pond
area must be established.
(4) Some modelling of unsaturated zone flow is needed to provide a
leak detection confidence level for the monitoring well network system.
Unless the results of the above items prove conclusively that a
leak from any area of the ponds reaches the edges and is detectable, this
neutron probe system is not acceptable as a stand alone monitoring network.
Consideration should be given to other methods, including other surface
geophysical and cross borehole geophysical methods, such as described
by Peters et al. (1982), and EarthTech Corporation (1981).
References:
Vilson, L.G., June 1980, "Monitoring in the Vadose Zone: A Review
of Technical Elements and Methods", EPA-600/7-80-134, U.S.
Environmental Protection Agency, Las Vegas, Nevada.
Everett, L.G., Vilson, L.G., and Hoylman,E.V., 1984, "Vadose Zone
Monitoring for Hazardous Waste Sites", Noyes Data Corporation, Park Ridge,
New Jersey.
Peters, V.E., Schultz, O.U., and Duff, R.M., 1982, Electrical Resistivity
Techniques for Locating Liner Leaks, EPA project report, Municipal
Environmental Research Laboratory, Cincinnati, Ohio.
EarthTech Research Corporation, 1981, Assessment of Innovative Techniques
to Detect Landfill Liner Failings, EPA project report, Cincinnati, Ohio.
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Region 5. Library :.-,.-
77 Wesl Jackson Boulevard, 12th FlOOf
Chicago, H 6Ct04-3590
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