United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPA/ROD/R04-92/114
September 1992
c/EPA Superfund
Record of Decision:
New Hanover County Airport
Burn Pit, NC
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NOTICE
The appendices listed in the index that are not found in this document have been removed at the request of
the issuing agency. They contain material which supplement but adds no further applicable information to
the content of the document All supplemental material is, however, contained in the administrative record
for this site.
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50272-101
REPORT DOCUMENTATION
PAGE
1. REPORT NO.
EPA/ROD/R04-92/114
3. Recipient. Acceeiion No.
4. TWe and Sukxrte
SUPERFUND RECORD OF DECISION
New Hanover County Airport Burn Pit, NC
First Remedial Action - Final
5. Report Dete
09/29/92
7. Auttwr(e)
8. Performing Organization Rept No.
». PcrfoimMgOrgaintalion Name end Mdree*
10. Pro|KVTmk/Woik Unit No.
11. Contrect(C) or GrantfG) No.
(C)
(G)
12. SponewingOrg*nizilionNem*indMdr*e»
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
13. Typo of Report ft Period Covered
800/000
14.
15. SupplMranUryNolM
PB93-964006
16. Abetnct (Limit: 200 norde)
The New Hanover site is located on Gardner Road approximately 500 feet west of the New
Hanover County Airport terminal, New Hanover, North Carolina. Land use in the
vicinity of the site is commercial, industrial, and residential. The site was
originally developed as a military hospital; however, from 1968 to 1979, the site was
used for fire-fighter training purposes. During training exercises, jet fuel,
gasoline, petroleum storage bottoms, fuel oil, kerosene, and sorbent materials from
oil spill cleanup were burned in a pit. During its active years, water from the pit
was allowed to flow onto land surfaces. Inspections conducted after the pit was
abandoned showed that most of the standing liquid in the pit was water. The bottom of
the pit and the soils immediately surrounding the pit were black with characteristics
similar to tar. In addition to the burn pit area, fire-fighting activities resulted
in contamination at several other site areas, including an auto burn area; a railroad
tank burn area; an aircraft mock-up area; a fuel tank and pipelines area; and two
stained soil areas north of the burn pit. In 1990, under EPA order, the PRP removed
waste materials, contaminated water, surface and subsurface soils, and structures.
Removed and disposed of were approximately 12,500 gallons of contaminated water;
(See Attached Page)
17. Document Anelyeie a. Deecrlptore
Record of Decision - New Hanover County Airport Burn Pit, NC
Remedial Action - Final
Contaminated Media: soil, gw
Key Contaminants: VOCs (benzene), metals (chromium, lead)
b. Mentffien/Open-Ended Terrne
118. AveilibUty State
1S. Security Clara (Thie Report)
None
20. Security daw (Thto Peg*)
None
21. No. ofPege*
96
22. Price
(SeeANSJ-ZM.1B)
SM MMructfon* on fewre*
OPTIONAL FOHM 272 (4-77)
(Formerly NDS-35)
Deportment of Commerce
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EPA/ROD/R04-92/114
New Hanover County Airport Burn Pit, NC
First Remedial Action - Final
Abstract (Continued)
3,200 tons of contaminated soil; drums; and dismantled structures and pipelines. This
ROD addresses restoration of the aquifer to drinking water quality as a final action for
this site. The primary contaminants of concern that affect the soil and ground water are
VOCs, including benzene; and metals, including chromium and lead.
The selected remedy for this remedial action includes no further action for site soil
based upon the reduced contamination levels and elimination of sources by the
1990 removal action. The selected ground water remedy includes a 1-year period for the
collection of additional data on the quality of the ground water; following a '
treatability study, the actions taken to treat the estimated 9.7 million gallons of
contaminated ground water will consist of a ground water extraction system, an onsite air
stripping process to remove volatile organics, and a pipeline discharging the treated
ground water to the Northside POTW system; a review of the existing ground water
monitoring system to ensure proper monitoring of ground water quality and the
effectiveness of the ground water extraction system; and ground water monitoring for a
4-year period and aquifer monitoring every year following discontinuation of ground water
extraction. If, at the end of any 5-year period, certain portions of the aquifer cannot
be restored to their beneficial use, the following contingencies may apply as a
modification to the existing system: engineering controls or long-term gradient controls
will be provided by low-level pumping; consideration of a waiver chemical-specific ARARs
for the aquifer; institutional controls to restrict access to certain portions of the
aquifer; continued monitoring of specific wells; and reevaluation of remedial
technologies for ground water restoration. The estimated present worth for this remedial
action is $1,932,800, including an O&M cost of $1,073,700 calculated for a 4.5-year
period.
PERFORMANCE STANDARDS OR GOALS: A "No Action" alternative was selected for the soils;
therefore, no clean-up levels were established. Chemical-specific ground water clean-up
levels are based on the North Carolina Water Quality, EPA, and MCL standards and include
benzene 1 ug/1; chromium 50 ug/1; and lead 15 ug/1.
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RECORD OF DECISION
REMEDIAL ALTERNATIVE SELECTION
NEW HANOVER COUNTY AIRPORT BURN PIT SUPERFUND SITE
WILMINGTON, NEW HANOVER COUNTY
NORTH CAROLINA
PREPARED BY:
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION IV
ATLANTA, GEORGIA
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DECLARATION FOR THE P2CORD OF DECISION
SITE NAME AND LOCATION
New Hanover County Airport Burn Pit
Wilmington, New Hanover County, North Carolina
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action for the New
Hanover County Airport Burn Pit Superfund Site in Wilmington, North Carolina,
chosen in accordance with the Comprehensive Environmental Response,
Compensation, and Liability Act of 1980, as amended by the Superfund
Amendments and Reauthorization Act of 1986, and, to the extent practicable,
the National Oil and Hazardous Substances Pollution Contingency Plan. This
decision is based on the administrative record file for this Site.
The State of North Carolina conditionally concurs with the selected remedy.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from this Site, if not
addressed by implementing the response action selected in this Record of
Decision, may present an imminent and substantial endangennent to public
health, welfare, or the environment. Presently, no unacceptable current or
future risks were identified associated with the New Hanover Site; however,
concentrations of contaminants in the groundwater are above federal maximum
concentration levels and state groundwater quality standards.
DESCRIPTION OFTTHE SELECTED REMEDY
The selected remedy addresses the elevated concentrations of groundwater
contaminants and restores the aquifer to drinking water quality. No further
action is required for Site soils.
The selected remedy, Alternative GW3, will permanently remove contaminants in
the groundwater through groundwater extraction and on-site, above-ground
treatment. The following activities are involved in this alternative:
• A one year period for the collection of additional data on groundwater
quality.
• Following a treatability study, contaminated groundwacar will be
extracted from within and at the periphery of the plume via extraction
wells and piped to an on-site, above-ground treatment process.
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Pretreatment may be required to remove total suspended solids and iron.
The pretreatment step would generate c by-product sludge.
Treatment process consists of an air stripper to reduce the levels of
contamination to the pretreatment requirements of the publicly owned
treatment works. Additional treatment will be achieved by the publicly
owned treatment works.
STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the environment,
complies with federal and state requirements that are legally applicable or
relevant and appropriate to the remedial action, and is cost-effective. This
remedy utilizes permanent solutions and alternative treatment technology to
the maximum extent practicable, and satisfies the statutory preference for
remedies that employ treatment that reduces toxicity, mobility, or volume as a
principal element. Since this remedy may result in hazardous substances
remaining in the groundwater on-site above the chemical-specific applicable
requirements, a review will be conducted within five years after commencement
of remedial action to ensure that the remedy continues to provide adequate
protection of human health and the environment.
Greer C. Tidwell
Regional Administrator
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THE DECISION SUMMARY
FOR THE
RECORD OF DECISION
NEW HANOVER AIRPORT BURN PIT SITE
WILMINGTON, NEW HANOVER COUNTY
NORTH CAROLINA
PREPARED BY:
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION IV
ATLANTA, GEORGIA
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TABLE OF CONTENTS
SECTION PAGE No
1.0 INTRODUCTION x
2. 0 SITE LOCATION AND DESCRIPTION 1
3.0 SITE HISTORY 1
4.0 ENFORCEMENT ACTIVITIES 7
5.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION 8
6.0 SCOPE AND ROLE OF RESPONSE ACTION WITHIN SITE STRATEGY -. 10
7.0 SUMMARY OF SITE CHARACTERISTICS 10
7.1 Soils 11
7.1.1 Surface Soils 15
7.1.2 subsurface Soils 18
7 .2 Groundwater 24
7.3 Hydrogeological Setting 25
7.4 Pathways and Routes of Exposure 36
8.0 SUMMARY OF SITE RISKS 42
8.1 Contaminants of Concern .. 42
8.2 Exposure Assessment 43
8.3 Toxicity Assessment 44
8.4 Risk Characterization 47
8.5 Risk Uncertainty 51
8.6 Ecological Risk 51
8.7 Summary 52
9.0 DESCRIPTION OF ALTERNATIVES 52
9.1 Applicable or Relevant and Appropriate Requirements 53
9.1.1 Action-Specific Applicable or Relevant and
Appropriate Requirements 53
9.1.2 Chemical-Specific Applicable or Relevant and
Appropriate Requirements 53
9.1.3 Location-Specific Applicable or Relevant and
Appropriate Requirements 54
9.2 Remedial Alternatives to Address Soil Contamination 54
9.3 Remedial Alternatives to Address Groundwater
Contamination 54
9.3.1 Alternative GW1: No Action/Long Term
Monitoring 60
9.3.2 Alternative GW2: Vertical Barrier/Cap 62
9.3.3 Alternative GW3: Groundwater Extraction and
Physical Treatment (Air Stripping) with
Discharge to Publicly Owned Treatment Works 63
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TABLE OF CONTENTS
SECTION PAGE No
9.3.4 Alternative GW4: Groundwater Extraction
and Physical/Chemical Treatment (Chromium
Reduction, Metals Precipitation, and Air
Stripping) with Discharge via On-Site
Spray Irrigation 64
9.3.5 Alternative GW5: Groundwater Extraction
and Physical/Chemical Treatment (chromium
Reduction, Metals Precipitation, and Air
Stripping) with Discharge to Surface Water
(Smith Creek) 65
10.0 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES 66
10.1 Threshold Criteria 66
10.1.1 Overall Protection of Human Health and
the Environment 65
10.1.2 Compliance with Applicable or Relevant
and Appropriate Requirements 68
10.2 Primary Balancing Criteria 68
10.2.1 Long-Term Effectiveness and Permanence 68
10.2.2 Reduction of Toxicity, Mobility, or Volume 73
10.2.3 Short-Term Effectiveness 73
10.2.4 Implementability 73
10.2.5 Cost 74
10 .3 Modifying Criteria 74
10.3.1 State of North Carolina Acceptance 74
10.3.2 Community Acceptance 74
11.0 DESCRIPTION OF THE SELECTED REMEDY 75
11.1 Performance Standards to be Attained 76
11.2 Groundwater Remediation 76
11.3 Additional Conditions/Additional Data Requirements/
Monitor Existing Conditions 79
11.4 Cost 80
12.0 STATUTORY DETERMINATION 80
12.1 Protection of Human Health and the Environment 80
12.2 Compliance with Applicable or Relevant and
Appropriate Requirements 80
12 .3 Cost Effectiveness 80
12.4 Utilization of Perr:..r^ent Solutions and
Alternative Treatment Technologies or
Resource Technologies to the Maximum
Extent Practicable 81
12.5 Preference for Treatment as a Principal Element 81
13.0 SIGNIFICANT CHANGES 81
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APPENDICES
Appendix A - State of North Carolina's Letter of Conditional Concurrence
Appendix B - Proposed Plan Fact Sheet
Appendix C - Responsiveness Summary
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LIST OF FIGURES
FIGURE
PAGE NO.
Figure 1. Map Showing Site Vicinity 3
Figure 2. Map Illustrating Features/Locations
of Structures On the Site 4
Figure 3. Topographic Map of Site and Surrounding
Locating Nearest Residences 5
Figure 4. Map Depicting Estimated Extent of Groundwater
Contamination 14
Figure 5. Map Locating Surficial Soil Sampling Locations 16
Figure 6. Map Locating Subsurface Soil Sampling Locations 19
Figure 7. Map Locating Temporary Monitoring Wells 26
Figure 8. Map Showing Locations of Permanent Shallow
and Deep Monitoring Wells 29
Figure 9. Site Hydrogeologic Cross-Section Location Map 37
Figure 10. Site Hydrogeologic Cross-Section B-B' 38
Figure 11. Water Level Elevations - April 9, 1991 39
Figure 12. Water Level Elevations - April 17, 1991 40
Figure 13. Water Level Elevations - May 7, 1991 41
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LIST OF TABLES
TABLES
PAGE NO.
Table 1. .Contaminants Detected in Each Environmental Medium 12
Table 2. Concentration and Frequency of Detections of
Contaminants Found in Surficial Soils
and Corresponding Preliminary Remediation Goals 17
Table 3. Concentrations and Frequency of Detections of
Contaminants Found in Subsurface Soils
and Preliminary Remediation Goals 20
Table 4. Analytical Data Summary for Subsurface Soils
Including Frequency of Detections and Range
of Concentrations 23
Table 5. Concentrations and Frequency of Contaminants
Detected in Groundwater Samples Collected
from Temporary Monitoring Wells and
Preliminary Remediation Goals 27
Table 6. Concentrations and Frequency of Contaminants
Detected in Groundwater Samples Collected
from Permanent Monitoring Wells and
Preliminary Remediation Goals 30
Table 7. Analytical Data Summary for Groundwater Samples
Collected from Permanent Monitoring Wells 34
Table 8. Chemicals of Concern 43
Table 9. Potential Pathways of Human Exposure to Contaminants 45
Table 10. Daily Intake for Chemical of Concern 46
Table 11. Future Exposure Assumption Used to Estimate Risk 47
Table 12. Slope Factors and RfDs Used to Estimate Carcinogenic
and Noncarcinogenic Risk 49
Table 13. Human Health Risk 50
Table 14. Evaluation of Process Options 55
Table 15. Potential Action-Specific ARARs for Groundwater 56
Table 16. Potential Chemical-Specific ARARs for Groundwater 58
Table 17. Groundwater Remediation Levels 60
Table 18. Potential Location-Specific ARARs 61
Table 19. Summary of the Threshold Criteria Evaluation -
Public Health and Environmental Effects -
of the Alternatives 67
Table 20. Summary of the Primary Balancing Criteria
Evaluation of the Alternatives 69
Table 21. Summary of Present Worth Costs for the Remedial
Alternatives 75
Table 22. Remediation Goals and Corresponding Risks 77
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List of Acronyms
ARAR - Applicable or Relevant and Appropriate Federal, State or
Local Requirements
AWQC - Ambient Water Quality Criteria
CAA - Clean. Air Act
CERCLA - Comprehensive Environmental Response, Compensation, and
Liability Act of 1980 (Superfund)
cm/sec • - centimeters per second
CRP - Community Relations Plan
CSF - Cancer Slope Factor
CWA - Clean Water Act
BSD - Explanation of Significant Difference
EPA - Environmental Protection Agency
FS - Feasibility Study
GAC - Granular Activated Carbon
gpm - gallons per minute
HI - Hazard Index
HQ - Hazard Quotient
HRS - Hazardous Ranking System
LDRs - Land Disposal Restrictions
MCLs - Maximum Contaminant Levels
MCLGs - Maximum Contaminant Level Goals
rag/kg - milligrams per kilogram
mph - miles per hour
MW - Monitoring Well
NCAC - North Carolina Administrative Code
NCDHR - North Carolina Department of Human Resources
NCDNRCD - North Carolina Department of Natural Resources and Community
Development
NCDEHNR - North Carolina Department of Environment, Health, and Natural
Resources
NCGS - North Carolina General Statute
NCP - National Oil and Hazardous Substances Pollution Contingency
Plan
NOAA - National Oceanic and Atmospheric Administration
NPDES - National Pollution Discharge Elimination System
NPL - National Priority List
O&M - Operation and Maintenance
PAHs - Polycyclic Aromatic Hydrocarbons
PCBs - Polychlorinated Biphenyls
POTW - Publicly Owned Treatment Works
ppm - parts per million
PRPs - Potentially Responsible Parties
PW - Present Worth
RA - Remedial Action
RCRA - Resource Conservation and Recovery Act
RfD - Reference Dose
RD - Remedial Design
RI - Remedial Investigation
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List of Acronyms
RME - Reasonable Maximum Exposure
ROD - Record of Decision
SARA - Superfund Amendments and Reauthorization Act of 1986
SDWA - Safe Drinking Water Act
SFFRs - Submerged Fixed Film Reactors
SVOCs - Semi-volatile Organic Compounds
TAL • - Target Analyte List
TBC - To Be Considered
TCL - Target Compound List
TCLP - Toxicity Characteristic Leaching Procedure
TMV - Toxicity, Mobility, or Volume
ug/kg - micrograms per kilogram
ug/1 - micrograms per liter
UV/OX - Ultraviolet/Oxidation
VOCs - Volatile Organic Compounds
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RECORD OP DECISION
SUMHARY OP REMEDIAL ALTERN iTIVE SELECTION
POR THE HEW HANOVER COUNTY AIRPORT BURN PIT SUPERPUND SITE
WILMINGTON, NEW HANOVER COUNTY, NORTH CAROLINA
1.0 INTRODUCTION
The New Hanover County Airport Burn Pit Superfund Site (New Hanover Site or
the Site) was proposed for the National Priority List (NPL) in June 1988 and
was finalized on the list in March 1989 with a Hazardous Ranking System (HRS)
score of 39.39. As of March 1992, the Site was ranked/grouped 518 out of
1218 NPL sites across the country.
The New Hanover Site Remedial Investigation (RI) and Feasibility Study (FS)
have been completed. The RI, completed in January 1992, characterized the
nature and probable extent of the uncontrolled hazardous waste at the Site.
The Baseline Risk Assessment, completed in August 1992, defined the risk posed
by the hazardous waste described in the RI. The Proposed Plan Fact Sheet,
based on the May 18, 1992 draft FS document, provided the public a summary of
the detailed analysis of the No Action remedial alternative for soil and the
five (5) remedial alternatives for groundwater remediation.
This Record of Decision (ROD) has been prepared to summarize the remedial
selection process and to present the selected remedial alternative.
2.0 SITE LOCATION AND DESCRIPTION
The New Hanover Site is located on Gardner Road approximately 500 feet west of
the New Hanover County Airport in New Hanover County. The airport is
approximately \& miles north of Wilmington, North Carolina at latitude
34°16'29" north and longitude 77°54'55m west. Figure 1 shows the location of
the Site within the State of North Carolina and the County of New Hanover.
The 1,500 square foot burn pit was located near the center of a 4-acre plot as
shown in Figure 2.
Land use in the vicinity of the Site is commercial, industrial, and
residential. There are rental car maintenance facilities, a closed
sawmill/lumberyard, and a trucking company to the east of the Site. The land
immediately northeast, north, west and south of the Site is forested with
mixed southern hardwood forest, typical of the coastal plain area. This
wooded area extends for approximately 300 to 500 feet west and north and
800 feet south of the Site. The closest residential area is approximately
1,100 feet to the west of the Site. This residential area is separated from
the Site by a road, railroad tracks, and a we led area (refer to Figure 3).
3.0 SITE HISTORY
The New Hanover County Airport, originally called the Bluthenthal Airport, was
built in the l92Q's as a civil air facility owned by New Hanover County. In
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NEW HANOVER COUNTY
AIRPORT BORN PIT
RECORD 0? DECISION
-2-
1942, the Department of Defense requisitioned the airport for the United
States (U.S.) Army Air Corps. Between 1947 and 1948, the Army deeded the
airport back to the County. During the Korean War, the airport operations
were assumed by the U.S. Marine Corps for military purposes and during the
Vietnam conflict, the U.S. Air Force took control of the airport. Between the
Korean War and the Vietnam conflict and following the Vietnam conflict, the
airport operations were under the control of the County. The facility was
renamed the New Hanover County Airport in 1970.
The Site was originally developed as a military hospital during World War II.
The construction date of the original burn pit is unknown, but a second pit
was constructed in 1968 and used until 1979 by the Air Force and Cape Fear
Technical Institute for firefighter training purposes. The Wilmington Fire
Department and a number of fire departments in New Hanover County used the
facility for firefighter training purposes from 1968 to 1974. The burn pit
was of earthen construction, 30 feet by 50 feet in dimension, surrounded by a
3 foot berm, located near the center of a. 4-acre open field. The bottom of
the pit did not extend below the land surface.
Jet fuel, gasoline, petroleum storage tank bottoms, fuel oil, kerosene,
sorbent materials from oil spill cleanups, and on at least one occasion,
confiscated marijuana were burned in the pit. It is estimated that between
100 to 500 gallons of ignitable fuel were used during each firefighting
training exercise. Water was the primary fire extinguishing agent; however,
carbon dioxide and dry chemicals were also used.
Inspections conducted after the pit was abandoned showed most of the standing
liquid in the pit was water. During its active years, water from the pit was
allowed to flow onto the land surface. The bottom of the pit and the soils
immediately surrounding the pit were black with characteristics similar to
tar.
In addition to the burn pit, there were other areas of the Site contaminated
as a result of the firefighting training activities. These areas can be
located in Figure 2 and include:
an auto burn area,
a railroad tank car burn area,
an aircraft mock-up made of 55 gallon drums burn area,
the fuel supply tank,
the pipeline from the supply tank to each burn area, and
two stained soil areas north of the burn pit.
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FIGURE t
SITE LOCATION MAP
NEW HANOVER BURN PIT
WILMINGTON, NORTH CAROLINA
&EPA
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FIGURL 2
SITE MAP
NEW HANOVER BURN PIT
WILMINGTON, NORTH CAROLINA
LEGEND
DERM/ROAD
EXCAVATION
Culvert
APPROXIMATE SCALE
125 62.5 125
xEPA
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FIGURE 3
TOPOGRAPHY OP SITE AND SURROUNDING AREA/
LOCATING NEAREST RESIDENCES
ORIGINAL
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NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD 0? DECISION
-6-
Several concrete block buildings (apparently constructed as part of the
military hospital) are located onsite. Only the building referred to as the
"smoke house" was used in the firefighting training exercises. These concrete
block buildings do not contain any hazardous wastes.
The fuel distribution system consisted of an above ground storage tank and an
underground pipeline system. The fuel pipeline system was buried
approximately 1 foot below land surface. The pipeline extended from the
storage tank northwest to a junction box. The valve controlling flow to the
burn pit was located approximately half-way along this segment of the
pipeline. At the junction box, valves controlled flow to the other three
firefighter training areas. These features can be located in Figure 2.
In addition, a small amount of medical waste (discarded syringes which were
apparently burned) was noted in the area of the aircraft mock-up during the
confirmation sampling (December, 1990). A manhole accessing the former
infirmary's septic tank was also located. The potentially responsible parties
(PRPs) agreed to dispose of the medical waste as part of the removal plan; the
contents of the septic tank were investigated by U.S. Environmental Protection
Agency (EPA) as part of the RI.
In 1985, sampling by the New Hanover County Department of Engineering showed
heavy metals and volatile organic compounds (VOCs) in the pit sludge. In May
1986, the North Carolina Department of Health Services sampled the bottom
sludge layer of the pit and soil adjacent to and outside of the pit. Detected
in these samples were heavy metals, polycyclic aromatic hydrocarbons (PAHs),
and VOCs. The County applied for a Non-Discharge Permit to close out the burn
pit by land application of the pit contents. The permit was granted because
the statutory response time was exceeded by the State. However, the State
suggested that New Hanover County not land farm the pit contents because of
concerns over possible lead and chlorinated solvent contamination. The County
complied with this request.
Originally, efforts were made to dispose of the pit material by incineration
or recycling. These efforts were unsuccessful because of the high solids and
water content resulting in a low British Thermal Unit value for the material.
It was also found that it was not feasible to pump the sludge.
A survey for hazard ranking purposes was conducted at the Site•on
January 9, 1987. The Site was proposed on the NPL in June 1988 and was
finalized on the NPL in March 1989. The Site ranked 518 out of 1218. The
total HRS score was 39.39. The individual scores for groundwater, surface
water, and air were 67.69, 7.83, and 0.0, respectively.
The Agency for Toxic Substances and Disease Registry (ATSDR) conducted a
health assessment of the New Hanover Site in March 1989. The Health
Assessment concluded that the Site is of potential public concern because of
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NEW HANOVER COUNTY
X1RTORT BURN PIT
RECORD OF DECISION
-7-
risk to human health resulting from possible exposure to hazardous substances
at concentrations that may result in adverse human health effects.
EPA entered an Administrative Order on Consent (AOC) with the PRPs on
June 21, 1990 outlining the removal actions to be performed at the Site. This
AOC gave the PRPs approval to conduct the removal action. The removal began
in November 1990 and was completed in December 1990. The PRP sponsored
removal involved removing waste materials, contaminated water, and
contaminated surface and subsurface soils. A total of 12,500 gallons of water
was removed from the pit and 6,000 gallons of water was removed from on-site
tanks. Contaminated surface and subsurface soils were removed from the
firefighter training areas. In addition, structures associated with
firefighter training activities were dismantled and removed, including the
fuel supply tank and its associated underground piping system, the railroad
tank car, the automobile bodies and the aircraft mock-up made of 55-gallon
drums. A total of 3,220 tons of contaminated soil and debris were removed.
Excavated areas were backfilled to grade with 2,680 cubic yards of clean soil.
During the removal, 5 drums of blue paint sludge from around the perimeter of
the Site were also removed. These drums were overpacked and properly disposed
of in accordance with Resource Conservation and Recovery Act (RCRA)
regulations.
The removal of wastes and contaminated soils significantly altered the scope
of the RI/FS. Characterization of the Site consisted of confirming that the
source had been moved, confirming that the presence of any residual soil
contamination v i not adversely impact either human health or the
environment, de .ng 3iw.e specific geology, and hydrogeology and t'~a extent of
groundwater con .-naticn, and conducting an endangered species survey.
4.0 ENFORCEMENT ACTIVITIES
The "Responsible Party Search' document was completed by EPA on July 20, 1988.
Information reruest letters purs :~nt to Section 104 of Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA) and Section
3007 of RCRA ware sent to the identified PRPs.
The following entities were identified as PRPs for the New Hanover Site:
• New Hanover County (current owner/prior operator),
• City of Wilrr._ngton (generator/prior operator - trained firefighters at
the Site),
• Cape Fear Technical Institute Foundation, Inc. (prior generator/operator
- trained fire fighters at the Site),
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NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OF DECISION
-8-
. United States Customs Service (prior generator/operator reportedly
burned confiscated drugs at the Site), and
• United States Air Force (prior generator/operator - trained firefighters
at the Site).
CSX Transportation, Inc. was initially identified as a PRP, however, they were
excluded from the final list of PRPs because the only material CSX reportedly
contributed to the Site was diesel fuel. Diesel fuel is not a hazardous
substance under CERCLA by virtue of the petroleum exclusion found in Section
101(14) of CERCLA, 42 U.S.C. § 9601(14).
Providing the opportunity to conduct the RI/FS, special notice letters were
sent to the PRPs on September 20, 1989. The PRPs submitted a good faith offer
prior to the end of the 60-day moratorium, however, the Agency found the good
faith offer to be deficient. Therefore, the moratorium was not extended an
additional 30-days to allow for the completion of the RI/FS AOC negotiations.
Consequently, the Agency initiated Fund monies to conduct the RI/FS.
The PRPs, however, did sign an AOC to conduct a removal action at the Site in
May 1990. The AOC required the PRPs to conduct a cleanup of the surface and
subsurface soils. This work was done between November and December 1990 and
was overseen by the Agency.
Similarly, by issuance of a. special notice letter, the PRPs will be offered
the opportunity to conduct the remedial design/remedial action (RD/RA) as
specified in this ROD.
5.0 HIGHLIGHTS OP COMMUNITY PARTICIPATION
Community relations activities for this Site were initiated in May 1990, in
conjunction with the development of the RI/FS work plan. Community officials,
civic leaders, and residents in the immediate vicinity of the Site were
interviewed to determine the current level of Site awareness, gauge potential
concerns, and provide a basis for developing and implementing a comprehensive
community relations plan for the Site.
Information Repositories/Administrative Records for this Site were established
at the New Hanover County Public Library and in EPA, Region IV Regional
Information Center in Atlanta, Georgia. A Community Relations Plan (CRP)
identifying a proactive public outreach strategy was developed at the
direction of EPA, Region IV staff and submitted to the information
repositories prior to initiating RI field work. The following describes the
community relations activities conducted by the Agency for this Site.
-------
NEH HANOVER COONTY
AIRPORT BUSH PIT
RECORD Of DECISION
-9-
Two fact sheets and the Proposed Plan Fact Sheet were distributed to the
public during the New Hanover RI/FS. The first fact sheet, disseminated in
March 1991, provided the community a description of the Site, a brief history
of the Site, a summary of previous investigations at the Site, a brief
overview of the Superfund program, a list of RI and FS objectives, a time
frame for .activities, a list of contacts for more information and community
relations activities, and a glossary of terms and acronym- commonly used in
the Superfund program.
This fact sheet preceded the first public meeting. This public meeting, the
•Kick-Off Meeting", was held on April 4, 1991. The following topics were
emphasized at this meeting: the Superfund process, community relations
activities, field work as proposed in the RI/FS Work Plan, and a question arid
answer session.
A second Fact Sheet was distributed in December 1991. This fact sheet
summarized the findings and conclusions of the RI, restated the objectives of
the FS, and provided a revised time frame for future activities at the Site.
The public was informed through the Proposed Plan Fact Sheet and an ad
published on June 3, 1992 in the Wilmington Morning Star newspaper of the
June 11, 1992 Proposed Plan Public Meeting. The Proposed Plan Fact Sheet was
mailed to the public on June 8, 1992. The basis of the information presented
in the Proposed Plan was the draft FS document dated, May 18, 1992. A press
release reminding the public of the upcoming public meeting was also issued on
June 8, 1992.
The goals of the Proposed Plan meeting were to review the remedial
alternatives developed, identify the Agency's preferred alternative, present
the Agency's rationale for the selection of this alternative, encourage the
public to voice its own opinion with respect to the remedial alternative
selected by the Agency, and inform the public that the public comment period
on the Proposed Plan would run from June 11, 1992 to July 13, 1992. The
public was also informed a 30 day extension to the public comment period could
be requested and that all comments received during the public comment period
would be addressed in the Responsiveness Summary.
During the meeting, a request was made for the 30-day extension which extended
the public comment period on the Proposed Plan to August 12, 1992. A notice
/•is mailed on July 6, 1992 to addressees on the mailing list informing them of
tnis extension. An ad was also published in the July 8, 1992 edition of the
W -ington Morning .r newspaper informing the public tha7- the public comment
pc_:iod had been ext*. .ad to August 12, 1992.
-------
HEW HANOVER COCNTY
AIRPORT BDJOJ PIT
RECORD OF DECISION
-10-
6.0 SCOPE AND ROLE OP RESPONSE ACTION WITHIM SITE STRATEGY
The intent of the remedial action presented in this ROD is to restore the
aquifer to drinking water quality at this Site. This remedial action involves
the extraction and treatment of the contaminated groundwater at the Site.
Soils do not need further remediation as the November/December 1990 removal
action successfully removed the residual wastes and the contaminated soils.
This is the only ROD contemplated for the Site and no other operable units are
anticipated.
7.0 SUMMARY OP SITE CHARACTERISTICS
The overall nature and extent of contamination at the Site is based upon
analytical results of environmental samples collected from surface and
subsurface soils, from the groundwater, and the chemical /physical and
geological/hydrogeological characteristics of the area. Environmental samples
were collected over a period of time and activities. These activities
included the following sampling events: New Hanover County, 1985; State of
North Carolina, 1986; removal action in November/December 1990; RI field
activities in April 1991, May 1991, and November 1991; and an additional
groundwater sampling in July 1992. The majority of these samples were
analyzed for the entire target compound list (TCL) and target analyte list
(TAL). The TCL includes volatile and semi-volatile organic compounds,
pesticides, and polychlorinated biphenyls (PCBs); the TAL includes inorganics
such as metals and cyanide. TCL volatile and semi-volatile organic compounds
and TAL metals were detected in the environmental media sampled at the Site.
No PCBs, pesticides, or cyanide were detected in any of the environmental
samples collected at the Site and therefore, these contaminants will not be
discussed in the following sections. Based on the history of the Site, no
RCRA listed wastes are present at the Site.
An additional sampling effort was conducted by EPA in May 1990 to assess
potential contamination at the Site. These data was used to define areas to
be addressed during the removal action. These data and other data collected
prior to the 1990 removal no longer reflects current conditions at the Site
and therefore, these sets of data were not incorporated into this ROD.
Control samples were collected for surface soils, subsurface soils, and
groundwater. No surface water or sediment samples were collected as there is
very little likelihood that the nearest stream would have been impacted by
Site activities. The nearest surface streams to the Site are Smith Creek,
1 mile north (Plgura 3), and Northeast Cape Fear River, a little less than 2
miles to the east.
Tabla 1 lists the contaminants detected in each environmental medium sampled
at the Site. Contaminants followed by an asterisk (*) are the chemicals of
-------
NEW HANOVER COUNTY
AIRPORT BUHK PIT
RECORD OF DECISION
-11-
concern. The following sections discuss the results of samples collected at
the conclusion of the removal action and the RI.
Air samples were not collected as part of the RI/FS effort. However, the air
was monitored during the RI field work as part of the health and safety
effort. Based of the information collected, the quality of the air at and
around the Site is not currently being adversely impacted by the Site.
Preliminary remediation goals (PRGs) for soils and groundwater were developed
by the Agency for contaminants known to be at the Site in January 1991. The
PRGs developed for soil contaminants employed the most stringent risk based
scenario - having the contaminants present in the surface soils. The
groundwater PRGs included State groundwater quality standards, applicable
maximum concentration levels (MCLs), and cleanup goals based on the most
stringent risk based scenario - ingesting contaminated groundwater. The PRGs
were presented in the May 1991 RI Work Plan.
The source of contamination and the resulting contaminated soils were removed
by the PRP sponsored removal action in 1990. The analytical data from soil
samples collected at the completion of the removal action were utilized in the
RI. This data confirms that the removal was successful in removing the
contaminated soil.
Contaminants detected in the groundwater included VOCs, semi-volatile organic
contaminants (SVOCs), and metals. Benzene was the only contaminant
consistently detected above Federal MCLs. Benzene, chloroform,
1,2-dichloroethane, and ethylbenzene were detected above State groundwe.- -
quality standards. The total volume of groundwater impacted by the Sit is
estimated to be 9.7 million gallons. The plume of contamination is del. :eated
in Figure 4.
7.1 SOILS
Twenty-seven (27) soil samples collected at the Site were incorporated into
the RI report. As stated previously, the analytical data for soil samples
collected prior to the 1990 removal action are no longer suitable as they do
not reflect current conditions at the Site. Therefore, these samples were not
integrated into the RI report or the ROD.
Twenty-one (21) of these soil samples were collected at the completion of the
November/December 1990 removal action. Nineteen (19) of which were collected
below grade, at the bottom of the excavations prior to filling the excavations
in with clean fill. The results of these samples reflect subsurface soil
conditions. Two (2) surface soil samples were collected during this time
frame. They were collected at the only locations where surface water could
possibly leave the Site. This drainage is made possible by the presence of
-------
SEB HAHOVER COUNTY
AIRPORT BURN FIT
RECORD OF DECISION
-12-
TABLE 1 CHEMICALS DETECTED IN EACH ENVIRONMENTAL MEDIUM
*IWWTO>3*^
Benzene *
Carbon Disulfide
Chloroform *
1, 2-Dichloroethane *
Ethylbenzene *
Methyl Ethyl Ketone
Toluene
Total Xylenes
w^Ki^^^a^-^^ ?•&?* \*-$\'^ ::
Anthracene
Benzo (a) Anthracene
Benzo (a) Pyrene
Benzo (B and/or K) Fluoranthene
Chrysene
niethyl Phthalate
2, 4 -Dimethy Iphenol
Di-N-Butylphthalate
Fluoranthene
2 -Methy Inaphthalene
2 -Methy Iphenol
3- and/or 4 -Methy Iphenol
Naphthalene
Phenol
Phenanthrene
Pyrene
^bKa&tsm^
X
X
X
X
i*^^:®|*3ffe
X
X
X
X
X
X
X
X
X
X
X
X
^Jx-^-i-:" , *'**".,','
f «fjf&fr&NJfy%fSJ£9z& ?
X
X
X
X
X
X
X
X
=PxgL vASfe^
X
X
X
X
X
. X
X
* - Chemical of Concern
-------
NEW HANOVER COUNTY
AIRPORT BORN PIT
RECORD OF DECISION
-13-
-s
TABLE 1 CHEMICALS DETECTED IN EACH ENVIRONMENTAL MEDIUM
(CONTINUED)
|;SftJRfl3lllfCS , •• ^**' *f' ,v -'• S 1, ' vily^'X-^V J''~
Aluminum
Arsenic
Barium
Beryllium
Calcium
Chromium *
Cobalt
Copper
Iron
Lead *
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Potassium
Sodium
Strontium
Tin
Titanium
Vanadium
Yttrium
Zinc
v " rf'V'v%nSv'«W;y»
/ i '/v,-. ;5G***v' '<"iy 'V'
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
s .. , ••••, ft^: «-^ K%f^
** q#&x&&ii%$$&^K
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
* - Chemical of Concern
-------
AI'I'KOXIMAII
Sill HOUNOAHY
I'OSSlffll SURI ACE WAItR
OHAINAU AREAS
IIMKWAHY MOMIOR Will
SIIAHOW MONIIOK Will
1)1 IP UOMIOR Will
AI'I'HOXIMAII IIUIIS Of
CHOUNOWAIIH CONIAUNAIION
APPROXIMATE TOTAL EXTENT OF CONTAMINATION IN THE SURFICIAL AQUIFER
NEW HANOVER COUNTY AJRPORr BURN PIT SITE
,,TJIGURE
WILMINGTON, NORTH CAROLINA
ORIGINAL
-------
NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD Of DECISION
-15-
culverts that run underneath the earthen berm that surrounds the entire Site
at these locations (refer to Figure 2). Flow through these culverts will only
occur under very heavy downpour conditions. These samples were collected to
confirm that no contamination has left the Site via surface water runoff.
The other six (6) soil samples were collected as part of the RI. Five of
these soil samples, 2 surface and 3 subsurface, were collected in April 1991.
The last soil sample, a surface sample, was collected in November 1991.
7.1.1 SURFACE SOIL
The locations of the five (5) surface soil samples are shown in Figure 5.
Samples BP-01 and BP-02 were collected during the removal and samples
NH-001-SC, NH-003-SL, and SED-001, were collected during the RI. The
analytical results for these surface soil samples, the frequency the
contaminants were detected, and the PRGs for particular contaminants are
presented in Table 2.
As stated earlier, there are no on-site surface water features except for
occasional periodic wet areas following heavy rains. The perimeter drainage
ditch inside the berm surrounding the Site is neither a perennial surface
water feature nor does it <• nnect to any surface water drainage feature
off-site. Samples BP-01 ai . BP-02 were collected in the drainage pathway
where culverts run underneath the berm. Under very extreme wet weather
conditions, these culverts would allow surface water to drain from the Site at
these two locations. It was for this reason that these samples were collected
here. Although these samples were collected in the culvert drainage pathway,
they are considered as surface soil samples. No contamination was detected at
location BP-02 and 3 unidentified SVOCs (2.0J rag/kg) were detected at BP-01.
This data confirms that no significant quantities of contaminants have
migrated off-site via this route.
Total xylene at a concentration of 0.01 milligram/kilogram (rag/kg) and
one unidentified SVOC (7.0 mg/kg) was found in sample NH-001-SC, the
background/control surface soil sample. NH-003-SL, which was collected near
the burn pit area outside the clean fill area, showed no evidence of
contamination. This helps verify that the remo- il achieved vts goal of
removing contaminated surface soils. Several cc ,-aminants, total xylene
(0.0069J mg/kg), toluene (0.0061J mg/kg), phenol (0.18J mg/kg), and
one unidentified SVOC (3.0 mg/kg) were detected in sample SED-001.
As can be seen in Table 2, al. contamination, organic or inorganic, detected
in the surface soil samples were considerably below the established PRGs.
-------
LEGCND
FIGURE 5
SURFACE SOIL
SAMPLING LOCATIONS
:::: BERM/ROAD
— EXCAVATION
A SURFACE SOIL SAMPLE
APPROXIMATE SCALE
123 0 62.5 129
( IN FEET )
1 Inch - m It.
TANK CAR
BURN AREA
-------
NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OP DECISION
-17-
TABLE 2 CONCENTRATION AND FREQUENCY OF DETECTIONS OF CONTAMINANTS FOUND IN
THE SURFACE SOILS AND THE CORRESPONDING PRELIMINARY REMEDIATION GOALS
Concentrations in mg/kg
Chemical
PRG
Frequency
of
Detection
NH-001SC
4/10/91
Control
BP-01
12/11/90
BP-02
12/11/90
NH-003SL
4/10/91
SED-001
11/19/91
J -- Estimated value
N/D -- Not Detected
N/A -- Not Applicable
PRG — Preliminary Remediation Goal
-------
NEW HANOVER COONTT
AIRPORT BOSK PIT ROD
-18-
7.1.2 SUBSURFACE SOILS
Nineteen (19) subsurface soil samples were collected at the conclusion of the
November/December 1990 removal action. These samples were collected to
confirm that the removal action successfully removed the soil contamination to
concentrations below the PRGs. The majority of the removal excavations were
dug down until the underlying saturated zone was encountered which averaged at
a depth of 3 feet. The confirmation subsurface soil samples, BP-03 through
BP-21, were composite samples collected from the bottom of the excavation.
The sampling locations were selected to deliberately bias the results. The
intent of this sampling effort was to represent a "worse case" scenario of
Site conditions to ensure that the removal action removed all soils with
concentration above the PRGs. The sampling locations are shown in Figure 6.
Table 3 presents the analytical results for the contaminants detected in the
subsurface soil samples along with the appropriate PRG. Table 4 summarizes
the data presented in Table 3 by providing the frequency of detection and the
range of concentrations for all the contaminants detected in the subsurface
soils.
Three additional subsurface soil samples were collected as part of the RI
effort. Their locations are also shown in Figure 6. Sample NH-002SL was the
subsurface background or control sample. The sample designated NH-013SL was
collected in an effort to confirm the findings of sample BP-13 and the sample
designated as NH-018SL was collected in an effort to confirm the findings of
sample BP-18. Both samples BP-13 and BP-18 were collected as part of the
removal action. The analytical results for these three samples are also
included in Tables 3 and 4.
The PRGs for contaminants known to be present in the soils at the Site are
presented in the second column in Table 3. As can be seen in comparing the
levels of organics and inorganics detected in the samples collected from the
Site to these remediation goals, only one PRG was exceeded. This was for
total carcinogenic PAHs in sample BP-21. The PRG for total carcinogenic PAHs
is 0.31 mg/kg and the total concentration of carcinogenic PAHs found in sample
BP-21 was 0.643 mg/kg. However, two additional samples (BP-18 and NH-018SL)
were collected from the same location. Sample BP-18 was a duplicate of BP-21
and NH-018SL was collected during the RI. It is important to note the
complete absence of any PAHs in either of these samples.
Due to the presence of several VOCs in sample BP-13, an additional sample,
NH-013SL, was collected as part of the RI. Sample NH-013SL was collected at
approximately the same location and depth as BP-13. As can be seen in
Table 3, only one VOC, ethylbenzene, was detected at a concentration of
0.031 mg/kg. This is significantly below the levels of contamination detected
in BP-13.
-------
NEW HANOVER BURN PIT SITE
FIGURE 6
SUBSURFACE SOIL
SAMPLING LOCATIONS
LEGEND
BERM/ROAO
EXCAVATION
SAMPLE LOCATION
APPROXIMATE SCALE
&EPA
c
"P
—)
-------
NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OF DECISION
-20-
TABLE 3
CONCENTRATIONS AND FREQUENCY OF DETECTIONS OF CONTAMINANTS FOUND IN
THE SUBSURFACE SOILS AND THE CORRESPONDING PRELIMINARY REMEDIATION GOALS
(Concentrations in mg/kg)
Chemical
PRO*
NH-
002SL
4/10/91
Control
BP-03
12/11/90
BP-04
12/11/90
BP-05
12/11/9
0
BP-06
12/11/9
0
BP-07
12/11/9
0
BP-08
12/11/
90
BP-09
12/11/9
0
88H^<8^ - '-' -" '' ',.,- ' -
Ethylbenzene
Total Xylene
fil^liii
Anthracene
200,000
3,000
N/D
N/D
0.072
0.46
w$&ro&s?^ *, -•• s '**» '-' " -
Benzo (a) Anthracene*
Benzo (B and/or K)
Fluoranthene*
Benzo (a) Pyrene*
Diethyl Phthalate
Fluoranthene
2-Methyl Naphthalene
Naphthalene
Phenanthrene
Pyrene
Chromium
8,200
0.31
0.31
N/A
N/A
82,000
8,200
8,200
8,200
61,000
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
0.08J
0.068J
0.063J
1.6
0.048J
iil«^ -j'» " ' . " - "-t "''-<' -
Lead
15
500
1.7
N/D
4.0
5.4J
3.3
4.5J
2.6
3.4J
3.1
4.8J
2.8
4.1J
2.3
8.2J
2.8
3.8J
PRO - Preliminary Remediation Goal * - The sum total of carcinogenic PAHs is not to exceed 0.31 mg/kg
+ - Denotes Carcinogenic PAH N/D - Not Detected N/A - Not Applicable
-------
-21-
HEW HANOVER COUOTY
AIRPORT BURN PIT
RECORD OP DECISION
TABLE 3 CONCENTRATIONS
THE SUBSURFACE
Chemical
PRG*
Benzene
Ethylbenzene
Total Xylenr
AND FREQUENCY OF DETECTIONS OF CONTAMINANTS FOUND IN
SOILS AND THE CORRESPONDING PRELIMINARY REMEDIATION GOALS (CONTINUED)
(Concentrations in mg/kg)
i
i
0.41
BP-lu
12/11/90
BP-11
12/11/90
'&^^&S^3
200,000
3,000
I WSWii^m--f;?> ?V*' ' : ' ' * , J'{- s ' :
3.7
O.oadJ
0.37J
0.35J
u.96J
0.78J
11.0
1.6J
2.0J
^-; ---:<:
15
500
4.3
19J
5.2
38 J
2.1
3.2J
3.2
7.4J
2.8
8.5J
2.9
13J
3.0
23J
2.2
2.6J j
PRO - Preliminary Remediation Goal * - The sum total of carcinogenic PAHs is not to exceed 0.31 mg/kg 1
•f - Denotes Carcinogenic PAH N/D - Not Detected N/A - Not Applicable ||
-------
-22-
NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OP DECISION
TABLE 3 CONCENTRATIONS AND FREQUENCY OF DETECTIONS OF CONTAMINANTS FOUND IN
THE SUBSURFACE SOILS AND THE CORRESPONDING PRELIMINARY REMEDIATION GOALS (CONTINUED)
(Concentrations in mg/kg)
Chemical
PRG*
Ethylbenzene
Total Xylene
f&M^i^im^^S^^^^M
Anthracene
Benzo (a) Anthracene*
Benzo(B and/or K)
Fluoranthene*
Benzo (a) Pyrene*
Chrysene*
Diethyl Phthalate
Fluoranthene
2-Methyl Naphthalene
Naphthalene
Phenanthrene
Pyrene
Chromium
Lead
200,000
3,000
BP-18
12/12/90
BP-19
12/12/90
BP-20
12/12/90
BP-21
12/12/90
NH-013SL
4/17/91
NH-018SL
4/17/91
'/*—-;- ^ v<
8,200
0.31
0.31
N/A
0.31
N/A
82,000
8,200
8,200
8,200
61,000
15
500
3.0
18J
0.32J
0.05J
$s$$&?&
3.2
7.6J
',fr, , '*'
' •. '*&*'.!'*.. ..'... 1
3.2
\-" ^-t-f"'f<
2.9
7.3J
'."*"*'.-, "'•
0.053J
0.16J
0.25J
0.083J
0.15J
0.24J
0.25J
yf'5^:;-
2.2
61 J
0.031J
ff ., '' f * J * i *!• " ^ "" % ' <•£
f '" s "•
2.9
4.3
f * ff '$
1.9
2.8
PRG - Preliminary Remediation Goal * - The sum total of carcinogenic PAHs is not to exceed 0.31 mg/kg
+ - Denotes Carcinogenic PAH N/D - Not Detected N/A - Not Applicable
-------
NEW HMJOVER COCNTY
AIRPORT BURN PIT
RECORD OP DECISION
-23-
TABLE 4 ANALYTICAL DATA SUMMARY FOR SUBSURFACE SOILS
Concentrations in mg/kg
Chemical
YQliMKdSl? GtoBtitifa&lfe^--^'*'''^ &*>$&f'.^ ••' !^ *' 'A&Kt
^'^;^\;% >-S2 - /'^'IwJ^^^^ >i "'^' .1.'^
1/22
4/22
3/22
0.14J
0.031J - 2.6
0.46 - 3,9
1/22
1/22
1/22
1/22
1/22
1/22
1/22
7/22
2/22
6/22
3/22
22/22
21/22
0.053J
0.16J
0.25J
0.083J
0.15J
0.068J
0.08J
0.063J - 11.0
1.6
0.098J - 2.0J
C.048J - 0.25J
1.7 - 5.2
2.6J - 61J
J - Estimated Value
-------
NEW HANOVER CODNTT
AIRPORT BORK PIT
RECORD OP DECISION
^ -24-
7.2 GROPiroWATBR
Contaminants detected in the groundwater also included VOCs, SVOCs, and
metals. Contaminants were found in both the shallow and deep zones of the
upper water bearing formation. No monitoring wells (MWs) were completed in
the underlying aquifer.
The investigation on the quality of the groundwater occurred in several
phases. Initial groundwater samples were collected from temporary monitoring
wells installed during the November/December 1990 removal action. The second
round of groundwater samples were also collected from temporary wells which
were installed as part of the RI in April 1991. The location of these
temporary wells are presented in Figura 7. All the analytical data from the
temporary wells is presented in Tabla 5. It is important to note the almost
total absence of contaminants in the temporary wells installed during the RI.
This data establishes that the plume has not migrated in a south-
southwestwardly direction. The presumed regional groundwater flow direction
which is to the south, towards Smith Creek. The presence of the acetone is
attributable to the alcohol used to clean the sampling equipment between
sampling events.
Based on the analytical data from the temporary wells, six permanent
monitoring wells were installed at the Site later on in the RI. The location
of these wells are shown in Figura 8. Four (4) of the wells are deemed
shallow as the screened portion intercepts the water table. The screened
interval is 5-15 feet below land surface and these wells are designated by
•S'. The 10 foot screens in the two deeper wells were set on top of the clay
layer encountered at the Site at a depth of approximately 30 feet. The deep
wells are designated by "D*.
Four rounds of groundwater samples have been collected and analyzed from these
permanent wells. Full analytical scans were run on all but the second round
of samples. Only TCL VOCs were analyzed for in the samples collected during
second groundwater sampling event. The analytical data is presented in
Tabla 6 and is summarized in Tabla 7.
A total of eleven (11) different VOCs were detected in the groundwater;
however, the presence of acetone was introduced through field activities and
hence, is not considered a Site contaminant. The detection of chloroform may
'-?.ve also been introduced through field activities. Potable water was used in
tne installation and construction of the monitoring wells at the Site. The
potable water was obtained from a fire hydrant connected to the public water
supply system and stored in a portable tank kept at the Site. Chloroform was
detected in a water sample collected directly from the portable storage tank.
This sample was collected and analyzed as part of the quality assurance/
quality control effort of the RI.
-------
NEW HANOVER COUNT*
AIRPORT BURN PIT
RECORD OF DECISION
25-
Benzene, ethylbenzene, and total xylenes were the most frequently detected
contaminants as well as being present in the highest concentrations. A total
of. seven (7) different SVOCs were found in the groundwater.
2,4-Dimethylphenol, naphthalene, and 2-methylnaphthalene were the most
frequently detected SVOCs as well as being present in the highest
concentratibns. Twenty-one (21) metals were detected in the groundwater.
They all occur naturally. The high levels of chromium in the April 1991 data
is attributable to sediment suspended in the samples. The November 1991
analytical data more closely depicts the actual levels of chromium, as well as
the other metals, in the groundwater at the Site. Only the analytical data
for the heavy metals (chromium, lead, and mercury) are included in Tablas 6
and 7.
As can be seen, the greatest concentrations of organic contaminants including
both VOCs and SVOCs, are in the well nest designated MWS-002 and MWD-002.
These wells are approximately 50 feet southeast of where the burn pit was
located. The highest levels of benzene at 0.11 milligram/liter (mg/1) were
detected in both of these wells. 2,4-Dimethylphenol has also been detected in
every sample collected from these two wells but at lower concentrations.
Numerous VOCs and SVOCs were also detected in the two control wells, MWS-001
and MWD-001. VOCs detected in MWS-001 include benzene, ethylbenzene, and
total xylenes. VOCs detected in MWD-001 included the same VOCs as in MWS-001
and two (2) SVOCs, 2-methylnaphthalene and naphthalene. Because of the radial
flow of groundwater at the Site, as is discussed in Section 7.3, this pair of
wells do not represent true background conditions. Several organic chemicals
were sporadically observed in wells MWS-003 and MWS-004. Pigura 4 delineates
the plume of groundwater contamination.
The metals beryllium and lead were detected in only one (1) groundwater sample
which was collected from MWS-001. The concentration for lead, 0.022 mg/1, is
just above the MCLs for lead, 0.015 mg/1. Based on these findings, metals are
not considered to be significant Site related contaminants. The plume shown
in Figure 4 is based on the organic contaminant benzene.
7.3 HYDROCBOIiOCICAL 3BTTIHQ
New Hanover County is located within the Coastal Plain Physiographic Province.
Generally, the sequence of rock types beneath New Hanover County consists of
unconsolidated and consolidated sedimentary rock of predominantly coastal and
marine origin that begin at land surface and unconformably overlie crystalline
rock at depth. Potable water supplies are obtained from the relatively
shallow sedimentary formations. Groundwater occurring at greater depths is
undeveloped due to saline conditions. Groundwater 2Iow associated with the
fresh water aquifers beneath New Hanover County are largely effected by
topography, surface water features, and the geologic structure.
-------
FIGURE 7
LOCATIONS OF TEMPORARY MONITORING WELLS
USED DURING THE 1990 REMOVAL ACTION AND
THE APRIL 1991 REMEDIAL INVESTIGATION
LF.GEND
HKI;
•::•:' Y\VATI' '
KI-:M< 'VAi, A' "rii 'ii TKMI
Will,I. I,'"'AT I
KKMMI'IAI. IIIVI-::TI.:A
TKHr<'|
-------
HEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD or DECISION
-27-
TABLE 5 CONCENTRATIONS AND FREQUENCY OF CONTAMINANT DETECTIONS FOUND IN
GROUNDWATER SAMPLES COLLECTED FROM TEMPORARY MONITORING WELLS IN
DECEMBER 1990 AND THE CORRESPONDING PRELIMINARY REMEDIATION GOALS
(Concentrations in mg/1)
Chemical
PRG
Frequency of
Detection
BP-22
BP-23
BP-24
BP-25
ilitlllM '' -- V~
Acetone
Benzene
Carbon Disulfide
Chloromet-'
Ethylbenzene
Total Xvlenes
N/A
0.001
N/A
N/A
0.029
0.4 .
5/11
3/11
1/11
1/11
2/11
2/11
0.008J
0.001J
0.002J
0.22
0.12
0.002J
^^^^^^^^^M^^^^^^^.^fJ^l^^''T^ \^~::\ , "' ' *
Diethyl Phthalate
Di-N-Butylphthalate
2, 4-Dimethylphenol
2-Methylnaphthalene
Naphthalene
N/A
N/A
N/A
0.2
0.2
1/4
1/4
1/4
2/4
2/4
0.001J
0.001J
0.019
0.022
0.002J
0.002J
0.015
'4*$$\$^' &$&,%$'):& , :-'" V ; t' .
Chromium
Mercury
0.05
N/A
0/4
1/4
0.0016J
PRG - Preliminary Remediation Goal
N/D - Not Detected J - Estimated Value N/A - Not Applicable
-------
HEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OP DECISION
-28-
TABLE 5 CONCENTRATIONS AND FREQUENCY OF CONTAMINANT DETECTIONS FOUND IN
GROUNDWATER SAMPLES COLLECTED FROM TEMPORARY MONITORING WELLS IN
APRIL 1991 AND THE CORRESPONDING PRELIMINARY REMEDIATION GOALS (CONTINUED)
( Concentrations in mg/1)
Chemical
Acetone
Benzene
Carbon Disulfide
Chloromethane
PRG
NH-004
NH-005
NH-006
NH-007
NH-008
NH-009
NH-010
feM«M*^,^^::^/,h*> *& .:<* *-.'. ' ' ;
N/A
0.001
N/A
N/A
3.1J
0.68J
2.1J
0.0012J
0.0043J
0.0045J
0.51J
0.89J
PRG - Preliminary Remediation Goal
N/D - Not Detected N/A - Not Applicable
-------
FIGURE S
LOCATION OF I LRMANENT WELLS
NEW HANOVER BURN PIT
WILMINGTON, NORTH CAROLINA
LEGEND
BERM/ROAD
EXCAVATION
APPROXIMATE SCALE
123 0 •21 125
MWS • MONITORING WELL (SHALLOW)
MWO - MONITORING WELL (DEEP)
••'/ TANK CAR
BURN AREA
( IN FEET )
1 Inch - 125 ft.
-------
-30-
NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OF DECISION
TABLE 6 CONCENTRATIONS AND FREQUENCY OF DETECTIONS OF CONTAMINANTS
FOUND IN THE GROUNDWATER SAMPLES COLLECTED IN APRIL 1991
AND THE CORRESPONDING PRELIMINARY REMEDIATION GOALS
(Concentrations in mg/1)
Chemical
Benzene
Carbon Diaulfide
Chloroform
1 , 2-Dichloroethane
Ethylbenzene
Toluene
Total Xylenes
ws^^Sai/i^iASm^^
2, 4-Dimethylphenol
2-Methylnaphthalene
2-Methylphenol
Naphthalene
9SMSK:^^^S^K
Chromium
Lead
PRG
MWS-001
Control
0.001
N/A
N/A
N/A
0.029
1.0
0.4
N/A
0.2
N/A
0.2
ll^istfii^liit&kl '£?'$
0.05
0.015
0.0035J
N/D
0.0021J
N/D
0.0033J
N/D
0.0108J
N/D
N/D
N/D
N/D
0.082
N/D
MWD-001
Control
MWS-002
MWD-002
MWS-003
MWS-004
t0^^i?il^6^irvv;;I>-;i4f'd .. *// *v *'*"/' *<•'-
0.0079J
N/D
N/D
N/D
0.0085J
0.002J
0.0253J
*$Sf&M:;f:.
0.0023J
0.06J
0.0027J
N/D
^t!^iHSv^
0.072
N/D
0.11
0.043J
0.0058J
0.0194J
:^^^*/%
0.054
0.016J
0.0051J
0.009J
$ ^!8tei
0.058
0.11
0.0044J
0.034
0.014J
0.082J
^^f't^
0.042J
0.0061J
0.011J
r'r\&;'''-;,;r\
0.06
0.0018J
0.0029J
0.00089J
",' :
''',"<:', -.*.
0.065
0.0012J
.. f-
'•.'"','
0.071
ma - Preliminary Remediation Goal N/A - Not Applicable N/D - Not Detected J - Eatinated Value
8 - Shallow Monitoring Well (acraened interval 5-15 (eat below aurface)
D - Deep Monitoring well (ecreenad intervel 17-27 feet below aurfaca)
-------
NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OP DECISION
-31-
TABLE 6 CONCENTRATIONS AND FREQUENCY OF DETECTIONS OF CONTAMINANTS
FOUND IN THE GROUNDWATER SAMPLES COLLECTED IN APRIL 1991
AND THE CORRESPONDING PRELIMINARY REMEDIATION GOALS (CONTINUED)
(Concentrations in mg/1)
Chemical
Benzene
PEG
0.001
Chloroform
1, 2-Dichloroethaue
Ethylbenzene
Methyl Ethyl Ketone
Toluene
Total Xylenes
1
N/A
0.029
N/A
1.0
0.4
MWS-001
Control
0.0011
0.0034J
N/D
0.0012J
N/D
0.0041J
MWD-001
Control
MWS-002
MWD-002
MWS-003
MWS-004
i- /V" •;"£—
0.0077
0.0017J
N/D
0.0074J
0.0015J
0.0219J
0.031
0.0015J
0.0092J
0.064J
0.0025J
0.0091J
0.094
0.0027J
0.030
0.013J
0.082J
0.00051J
0.0016J
0.00077J
PRO - Preliminary Remediation Goal N/A - Not Applicable N/D - Not Detected J - Estimated Value
S - Shallow Monitoring Well (screened Interval S-1S feet below surface)
D - Deep Monitoring Well (screened interval 17-27 feet below surface)
-------
-32-
NEW HANOVER COUOTY
AIRPORT BURN PIT
RECORD Of DECISION
TABLE 6 CONCENTRATIONS AND FREQUENCY OF DETECTIONS OF CONTAMINANTS
FOUND IN THE GROUNDWATER SAMPLES COLLECTED IN NOVEMBER 1991
AND THE CORRESPONDING PRELIMINARY REMEDIATION GOAL (CONTINUED)
(Concentrations In mg/1)
Chemical
Benzene
PRO
0.001
MWS-001
Control
•I
0.0042
MWD-001
control
0.0077
MWS-002
0.074
MWD-002
0.11
MWS-003
MWS-004
MWD-003
Dup. of
MWD-002
0.0078
SFC-001
MWT-001
Ethylbenzene
0.029
0.0045J
0.0088
0.028
0.037J
0.0087
Toluene
1.0
N/D
0.0011J
0.0059J
0.0011J
Total Xylenes
2,4-Dimebhylphenol
0.4
N/A
0.0131J
N/D
0.025
0.0036J
0.0078J
0.0223
0.066J
0.0410
0.0259
0.0034J
2-Methylnaphthalene
0.2
N/D
0.019
0.018
2-Methylpheuol
N/A
N/D
0.0038J
0.0037J
3- and/or 4-Methylphenol
N/A
N/D
0.0029J
0.0026J
0.02
Beryllium
N/A
0.0014
N/P
Chromium
0.05
0.034
0.014
0.011
0.03
0.0081
0.031
0.012
0.071
0.0042
Lead
0.015
0.022
N/D
PRG - Preliminary Remediation Goal N/A - Not Applicable N/D
S - Shallow Monitoring Well (screened interval 5-15 feet below surface)
D - Deep Monitoring Well (screened interval 17-27 feet below surface)
- Not Detected
Estimated Value
-------
-33-
NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD Of DECISION
TABLE 6 CONCENTRATIONS AND FREQUENCY OF DETECTIONS OF CONTAMINANTS
FOUND IN THE GROUNDWATER SAMPLES COLLECTED IN JULY 1992
AND THE CORRESPONDING PRELIMINARY REMEDIATION GOAL (CONTINUED)
(Concentrations In mg/1)
Chemical
Benzene
1, 2-Dlchloroethane
Methyl Butyl Ketone
Ethylbenzene
Toluene
Total Xylenes
Bls(2-ethylhexyl)phthalate
2, 4-Dlmethylphenol
2-Methylnaphthalene
2-Methylphenol
3- and/or 4-Methylphenol
Naphthalene
Chromium
Lead
PRG
MWS-001
Control
MWD-001
Control
MWS-002
MWD-002
K^ ~*H ;Vt£K>!-ri€ H ." # - -
0.001
N/A
N/A
0.029
1.0
0.4
N/A
N/A
0.2
N/A
N/A
0.2
0.05
0 015
0.0052
N/D
N/D
0.0071
0.00051J
0.0141J
N/D
0.0027J
0.022
0.0033J
N/D
0.025
N/D
N/D
0.014
N/D
N/D
0.016
0.0014J
0.041
N/D
0.0052J
0.03
0.0074J
0.0055J
0.035
N/D
N/D
0.088
0.0018J
0.05
0.039
0.0008SJ
0.0109J
0.018J
0.012J
0.02J
C^"^t{£CTt^';
0.096
0.039
0.0028J
0.038J
^^^^^^^^Ev^S^ 'f ^
0.033J
0.009J
0.01J
*'' W» *$*" >,
MWS-003
MWS-004
' T/i ""/'•• *% '-••'•' ,>,
0.00052J
&^ ',<,&&$^^>r;f '-^'"' ^'^-
O.OS6
-"'"- * :,, '*' '
PRG - Preliminary Remediation <5oal N/A - Not Applicable N/D - Not Detected J - Estimated Value
S - Shallow Monitoring Well (screened interval S-15 feet below surface)
D - Deep Monitoring Well (screened interval 17-27 feet below surface)
-------
NEW HANOVER COOWTT
AIRPORT BORN PIT
RECORD Of DECISION
-34-
TABLE 7 ANALYTICAL DATA SUMMARY FOR GROUNDWATER
Chemical
YOJiJMSXWB: 'b»OMBK!»\-; ? ' ^"" ^ N "
• 11- ' ---"'-* - -- ^^ ---""- - — — - - "* "•" ^v.\ \ SJ
Acetone
Benzene
Carbon Disulfide
Chloroform
Chloromethane
1, 2-Dichloroethane
Ethylbenzene
Methyl Butyl Ketone
Methyl Ethyl Ketone
Toluene
Total Xylenes
feMfflS^^J^ssSaSw^^^S^SSw!?'^^?^^^^^^^'
Bis (2-ethylhexyl)phthalate
Diethyl Phthalate
Di -N-Buty Iphthalate
2 , 4 -Dime thy Iphenol
2 -Methy Inaphthalene
2 -Methy Iphenol
3- and/or 4- Methy Iphenol
Naphthalene
^J. . " ^S^Vj^Jy^^^^^^^^^^^^^^^^^^^^^^f
Beryllium
Chromium
Lead
Mercury
Froquancy
of
Dataction
Ranga of
Concentrations
(mg/1)
^r^rutTT cl:il*^K^%^!;lf
5/38
20/38
2/38
8/38
1/38
3/38
19/38
1/38
1/38
14/38
20/38
1/25
1/25
1/25
12/25
9/25
8/25
3/25
12/25
1/25
15/25
1/25
1/25
0.51J - 3.1J
0.0011 - 0.51J
0.0018J - 0.0043J
0.00051J - 0.0034J
0.0045J
0.0018J - 0.0044J
0.001J - 0.12
0.05
0.064J
0.00051J - 0.014J
0. 0.0077 J - 0.082J
0.0056
0.001J
0.001J
0.002J - 0.054
0.012J - 0.065
0.0027J - 0.0074J
0.0026J - 0.0055J
0.0015J - 0.035
0.0014
0.0081 - 0.082
0.022
0.0016J
-------
SW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OF DECISION
-35-
Regionally, the Site is located on the western side of a north-south trending
topographic divide. In the area of the Site, 25 to 31 feet of unconsolidated
quartz sand overlies a 5 foot unnamed clay layer (blue clay layer). The
precise extent of the clay layer is not known, however, it is believed to be
continuous beneath the Site as its presence was confirmed in four location
across the Site. Beneath the blue clay were light gray, medium to coarse
grained quartz sand and clay lenses to a depth of approximately 60 feet below
land surface. Hard, consolidated, sandy, phosphatic, fossiliferous limestone
with calcite filled fractures was encountered underlying these sand and clay
lenses. This limestone is believed to be the Castle Hayne Limestone, which
ends somewhere in the vicinity of the Site. A clay aquitard separates the
sandstone aquifer (Pee Dee) from the Castle Hayne beneath the Site.
The groundwater under the Site is designated as Class GA in accordance with
North Carolina's groundwater classification system and Class IIB under U.S.
EPA Groundwater Classification Guidelines (December 1986). The Class GA
classification means that the groundwater is an existing or potential source
of drinking water supply for humans as defined in Title 15, North Carolina
Administrative Code, Subchapter 2L (T15 NCAC 2L). EPA classifies the upper
zone of the aquifer (i.e., the groundwater above of the blue clay layer) as
Class IIB since the aquifer is of drinking quality but is not currently being
used as a source of drinking water. The groundwater beneath the blue clay
layer is assumed to be interconnected with the Castle Hayne Limestone
formation and is therefore, classified as IIA. Class IIA is defined as a
aquifer that is currently being used as a source of drinking water. For these
reasons, the groundwater needs to be remediated to a level protective of
public health and the environment as specified in federal and state
regulations governing the quality and use of drinking water. Both the Pee Dee
and the Castle Hayne are major sources of drinking water for New Hanover
County.
The permeability of the blue-gray clay unit was determined in the laboratory
to be 2.03 x 10~7 centimeters/second (cm/sec). A Site hydrogeologic cross-
section B-B' located on Plgur* 9 and shown in Figur* 10 indicates the
hydrogeologic units encountered beneath the Site.
The New Hanover Site and surrounding area are topographically and
hydraulically bounded by Smith's Creek to the south and southwest, small
tributaries to the Northeast Cape Fear River to the north and northeast, and
the Northeast Cape Fear River to the west. Essentially, all overland drainage
that occurs within this area is toward the Northeast Cape Fear River, which
combines flow with the Cape Fear River and eventually discharges to the
Atlantic Ocean. From the Site, it is approximately 4,800 feet to the nearest
topographically downgradient perennial surface water feature. Smith's Creek.
From this point. Smith's Creek meanders to the Northeast Cape Fear River for
an overland distance of approximately two miles. From the point of its
confluence with Smith's Creek, the Northeast Cape Fear River flows southward
-------
MEM HANOVER COUWTY
AIRPORT BORN PIT
RECORD OF DECISION
-36-
for approximately two miles and combines with the Cape Fear River. Flow
continues southward for approximately 20 miles until the Cape Fear River
discharges to the Atlantic Ocean.
The surface water drainage at the Site is markedly influenced by the surficial
sands. The surficial sands are permeable, allowing most precipitation to
infiltrate into the sands and recharge the surficial aquifer or become
evapotranspirated through the grasses growing at the Site. The surficial
sands are permeable enough such that overland flow does not occur during most
precipitation events.
As stated previously, the entire Site is surrounded by elevated roads which
form a berm around the Site. Outside of the elevated roads is a perimeter
ditch. Although perimeter ditches and drainage culverts are present, surface
water runoff from the Site does not occur. It is estimated that 90 percent of
the precipitation effectively recharges the undifferentiated deposits with the
remaining 10% evaporating.
The upper water bearing formation is under water table or atmospheric
conditions. The water table elevation at the Site is approximately 27 to
28 feet above NGVD29 (National Geodetic Vertical Datum of 1929). Typical
depths to the water table ranged from approximately 2.3 to 3.8 feet below land
surface. Figure 11, 12, and 13 present the static water table elevations
observed at the Site. Groundwater elevations near the middle of the Site
indicate a somewhat mounded water table condition. This may be due to the
recent removal activities which may have altered the hydraulic properties of
the Site soils at the former pits. The estimated hydraulic gradient across
the Site was observed to range between 0.0008 feet/feet on 04/09/91 to 0.00002
feet/feet on 05/07/91. The horizontal groundwater velocity in the upper water
bearing zone (above the blue clay layer) is 9.9 feet/year. The regional
groundwater flow direction is generally to the south. The groundwater below
the blue clay layer is under confined conditions but since no monitoring wells
were installed below this formation during the RI, no specific information was
collected on the properties of this aquifer.
7.4 PATHWAYS ACT) ROUTES OP EXPOSURE
Tabla 8 lists the chemicals of concern and why these particular constituents
are considered chemicals of concern at the New Hanover Site. The chemicals of
concern include VOCs and metals. These chemicals of concern pertain to the
groundwater only.
An exposure pathway is the route or mechanism by which a chemical agent goes
from a source to an individual or population. Each exposure pathway includes
the following:
-------
AI'I'KOXIMAII
Sill HUUNIIAKY
1IUCOKAKY
(IIISI HVAIION WILL
MIAilOW UONIIOR MIL
Dili' UONIIOH Will
II SI UOHINC
// IANK CAN
'/ UUKN AlflA
POOR QUALITY
SITE H YDROGEOLOGIC CROSS-SECTION LOCATION MAP
NEW HANOVER COUNTY AIRPORf BURN PIT SITE
WILMINGTON, NORTH CAROLINA
FIGURE 9
-------
B'
SCUTHWEST
B
§
II
.-> :•!!:•:
•4.88'lr u '
I
I
* -:=2742_ „ ^r^-TT^r_-r^---_;-:-:-->Z78ir_------- ;
3 : -—« «« .rr^cc^_-.Svr..vvvvvv! :-:-:-M-:-I-M-I-M-I-M-M-I----------------------'-!i-»I-:-3 -
•. • ^
-23 -
-30 -
0 • . • i i •
': • ..
•.•',! ••
... il • - -20
. I • «
SiLTV SANO
ME3IUM "0 C3ARSE SAND
H CLAY
SLUE-GRAY CLAY
^'NE SANO
SANDY
. MESTONE
=C~N-CME"3IC SuSFACE
S *-• S.RFC^l.
iMcy 7. -?9')
50
5C
HORIZONTAL
SCALE :N
SITE HYDROGEOLOGIC CROSS-SECTION B-B'
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
- WILMINGTON, NORTH CAROLINA FIGURE 10
POOR QUALITY
ORIGINAL
-------
LEGFNO
til HU/HOAI >
rnitniiniomin IXCAVAllON
A
O
I'OSSIUI SUHIACI WAItH
DHAINAGI ANLAS
IIMHOKAHV fll/OMHIH
011 Sill UONIIOR M'll
WAIIH 11VII CONIOUR (II. AMSl)
IXIKAJ'(IIAIII) WAKR It VII
CQNIOUH (It AtlSl)
OStC-001 (ApptannDote location)
•X \SIII UOUNUAW
\ \
WATER LEVEL ELEVATIONS - April 9,1991
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
POOR QUALITY
x QRIGINM
FIGURE
-------
WAIIH ICVCL
CONIOUN (II AUSl)
O SI COO I (Appronmole tocolKxi)
WATER LEVEL ELEVATIONS - April 17,199
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
FIGURE
WILMINGTON, NORTH CAROLINA
:
-------
LIGEND
- z.: UtNM/H(MU
nnirniiiinnrm [ XCAVAIION
O
-2; J
POSSUM f SUHIACl WAIIH
DKAINAU ARUC
OUSIHVAIION «HU
SIIAUOW MOMIOR Wll
III 11' UOMIOH Mil
011 SHI UOWIOR Will
WAIIH HVtl CONIOUR (II AIISl)
IXIKAHOIAIIO WAIfR HVtl
CONIOUK (It AMSI)
O -JC 001 (Appfoiiniole (ocolnn)
AIM'KOXIMAIt
SIU HOUNDAMY
WATER LEVEL ELEVATIONS - May 7,1991
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
-------
HW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OF DECISION
-42-
A source and mechanism of chemical release to the environment,
A transport medium (e.g., soil or groundwater),
An exposure point (where a receptor will contact the medium), and
An exposure route (i.e., ingestion, inhalation, or dermal contact).
A pathway is considered complete when all of the above elements are present.
Table 9 summarizes the evaluation of potential exposure pathways for the New
Hanover Site.
The two transport mechanisms most likely to occur at the New Hanover Site are
air and groundwater. Air could become an exposure pathway due to the
volatilization of contaminants from the water when a person takes a bath or
shower. Groundwater would also become an exposure pathway if the contaminated
groundwater is used as potable water.
Based on the information collected during the RI, neither of these two
transport mechanisms are presently occurring. Therefore, there are no current
unacceptable risks presented by the Site. As can be seen, the only potential
risks are future risks associated with use of the contaminated groundwater as
a source of potable water.
8.0 SUMMARY OP SITE RISKS
CERCLA directs that the Agency must protect human health and the environment
from zur-rent and future exposure to hazardous substances at Superfund sites.
In order to assess the current and future risks from the New Hanover Site, a
baseline risk assessment was conducted in conjunction with the RI. This
section of the ROD summaries the Agency's findings concerning the impact to
human health and the environment if contaminated media (i.e., groundwater) at
the Site were not remediated. The baseline risk assessment for this Site is
presented as a stand alone document in the New Hanover administrative record.
8.1 CONTAMIHAHTS OF COKCKRH
Table 8 provides a comprehensive list of the contaminants identified as
chemicals of potential concern at the Site in the groundwater. The
contaminants of concern consist of four (4) VOCs and two (2) metals.
Table 10 provides the reasonable maximum exposure concentrations which were
used in calculating the carcinogenic and noncarcinogenic risks associated with
each chemical of concern.
-------
NOT HANOVER COONTY
AIRPORT BOKS PIT
RECORD OF DECISION
-43-
TABLE 8 CHEMICAL'S OF CONCERN
Benzene
Chloroform
1,2-Dichloroethane
Ethylbenzene
Chromium
Lead
Exceeded NCAC and Federal Drinking Wacer Standard, a carcinogen
Exceeded NCAC Groundwater Quality Standard, a carcinogen
Exceeded NCAC Groundwater Quality Standard, a carcinogen
Exceeded NCAC Groundwater Quality Standard, a noncarcinogen
Exceeded NCAC Groundwater Quality Standard, a carcinogen
Exceeded Federal Drinking Water Standard, a carcinogen
The chemicals of concern listed in Table 8 were found in the groundwater. The
extent of the plume was shown in Figure 4 and the range of concentrations,
including the maximum concentration for each contaminant detected in the
groundwater at the Site was presented in Table 7. The contaminants included
in Table 8 were contaminants whose concentrations exceed established
applicable or relevant and appropriate requirements (ARARs).
When firefighting exercises were discontinued, the Site became inactive. The
Site is on property under the direction of the New Hanover Airport authority;
consequently, there is no current onsite land use. According to the 1989
Master Plan for the airport, the Site is in an area which is designated for
industrial development.
There are residents within a three-mile radius to the Site who obtain drinking
water from private wells. The nearest private potable wells are approximately
2,000 feet from the Site. However, these wells are typically completed in the
lower fresh water bearing formations such as the Castle Hayne Limestone and
Pee Dee formation, as the groundwater in the shallow zone contains high levels
of dissolved inorganic constituents (i.e., sulfates).
8.2 EXPOSURE ASSESSMENT
The objective of the exposure assessment is to estimate the type and magnitude
of potential exposures to the chemicals of concern that are present at the
Site. The results of the exposure assessment are combined with chemical-
specific toxicity information to characterize potential risks.
-------
NEW HANOVER COONTY
AIRPORT BORN PIT
RECORD OF DECISION
-44-
There are no current receptors as the 1990 removal eliminated any surface
contamination and the contaminated groundwater remains on Site, therefore the
contaminated groundwater is not being used as a source of potable drinking
water. The primary future human receptors at the Site may be off-site
residents (adult and children) through the use of contaminated groundwater as
a potable source of water. Although, the impacted groundwater is not
currently being used as a drinking water source, EPA and the State of North
Carolina have classified the aquifers underlying the Site as Class II-A/II-B
and GA aquifers, respectively. Therefore, these resources should be
maintained at drinking water quality.
Table 11 provides a summary of the exposure and intake assumptions which were
used in the baseline risk assessment.
8.3 TOXICITY ASSESSMENT
The toxicity assessment was conducted to further determine the potential
hazard posed by the chemicals of concern for which exposure pathways have been
identified. Available evidence is weighed in regards to the potential of
particular contaminants to cause adverse effects in exposed individuals and to
provide, where possible, an estimate of the relationship between the extent of
exposure to a contaminant and the increased likelihood and/or severity of
adverse effects.
Cancer slope factors (CSFs) have been developed by EPA's carcinogenic
Assessment Group for estimating excess lifetime cancer risks associated with
exposure to potentially carcinogenic chemicals. CSFs, which are expressed in
units of milligrams/kilogram/day'1 [ (mg/kg/day)"1], are multiplied by the
estimated intake of a potential carcinogen, in (mg/kg/day), to provide an
upper-bound estimate of the excess lifetime cancer risk associated with
exposure at that intake level. The term "upper-bound' reflects the
conservative estimate of the risks calculated from the CSF. Use of this
approach makes underestimation of the actual cancer risk highly unlikely.
CSFs are derived from the results of human epidemiological studies or chronic
animal bioassays to which animal-to-human extrapolation and uncertainty
factors have been applied.
Reference doses (RfDs) have been developed by EPA for indicating the potential
f.~r adverse health effects from exposure to chemicals exhibiting
noncarcinogenic (systemic) effects. R(Ds, which are expressed in units of
mg/kg/day, are estimates of lifetime daily exposure levels for humans,
including sensitive individuals, which will result in no adverse health
effects. Estimated intakes of chemicals from environmental media (i.e., the
amount of chemical ingested from contaminated drinking water) can be compared
to the R,D. R{Ds are derived from human epidemiological studies or animal
studies to which uncertainty factors have been applied (i.e., to account for
-------
NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OP DECISION
-45-
TABLE 9 POTENTIAL PATHWAYS OF HUMAN EXPOSURE TO CONTAMINANTS
Air
Inhalation of dust
and volatilea
Inhalation of
volatiles
Local population (trespassers)
Local residents
Unlikely. Contaminated surficial and
subsurface soils removed. Burn pit and
other areas show signs of revegetation.
Yes. Volatiles present in groundwater.
Potential for exposure by volatilization
of contaminants during a shower or bath.
Groundwater
Ingestion; dermal
contact
Users of water from municipal,
industrial, commercial, or
residential wells
Potential future exposure. Current?" no
known contaminated residential wells.
Private wells are within 3 mile radius of
the Site.
Sediment
Dermal absorption
Local population (trespassers)
Unlikely. Sediments are not exposed for
direct contact. Sediments are not
contaminated with VOCs or PAHs.
Soil
(Onsite)
Incidental
ingestion; dermal
absorption
Local population (trespassers)
Unlikely. Contaminated surficial and
subsurface soils removed. Confirmation
samples verify appropriate cleanup. Site
under jurisdiction of airport security.
Surface
Water
None
Not applicable.
No. No permanent surface water bodies
onsite or offsite bodies of water
impacted by Site activities.
-------
-46-
NEH HANOVER COUNTY
AIRPORT BURN PIT
RECORD OP DECISION
TABLE 10 DAILY INTAKE FOR CHEMICALS OF CONCERN
Contaminant
Benzene
Frequency of
Detection
Kxpoure Point
Concentration
for Inge»tion
-------
trm HANOVER COUNTY
AIRPORT BURN PIT
RECORD or DECISION
-47-
TABLE 11 EXPOSURE ASSUMPTIONS USED TO ESTIMATE RISK
Co,, (contaminant concentration in
groundwater [mg/1])
IR
Bio
EF
ED
BW
DY
YL
(Ingest ion -Rate [I/day])
(Relative bioavai lability
factor [unit less])
(Exposure frequency
[days /year] )
(Exposure duration [years])
(Average body weight for an
adult [kg])
(days in a year)
(years in lifetime or period
over which risk is being
estimated, 70 year lifetime
for carcinogens; 30 years for
noncarcinogens )
-^K^li^Ki3^£t^^4iBmrtrrW^
* 5.V./. "X / VW'^W***. ,fj Af+tf •fffjT'Vf-.vfy^^^ %*-''>»^% .. r „
-
Contaminant specific
2
Ingest ion 1.0
Inhalation 1.0
350
30
70
365
For carcinogens - 70 years
For noncarcinogens - 30 years
the use of animal data to predict effects on humans). These uncertainty
factors help ensure that the RfDs will not underestimate the potential for
adverse noncarcinogenic effects to occur.
The Agency has derived CSFs and RfDs for the contaminants of concern at the
Site for use in determining the upper-bound level of cancer risk and non-
cancer hazard from exposure to a given level of contamination. These values
are provided in Table 12.
8.4 RISK CHARACTERIZATIOH
The risk characterization step of the baseline risk assessment process
integrates the toxicity and exposure assessments into quantitative and
qualitative expressions of risk. The output of this process is a
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MEM HANOVER COOSTT
AIRPORT SOW PIT
RECORD op DECISIOtT
-48-
characterization of the site-related potential noncarcinogenic and
carcinogenic health effects.
Potential concern for noncarcinogenic effects of a single contaminant in a
single medium is expressed as the hazard quotient (HQ) (or the ratio of the
estimated intake derived from the contaminant concentration in a given medium
to the contaminant's reference dose). By adding the HQs for all contaminants
within a medium or across all media to which a given population may be
reasonably exposed, the Hazard Index (HI) can be generated. The HI provides a
useful reference point for gauging the potential significance of multiple
contaminant exposures within a single medium or across media. The HQs and His
for the exposure pathways (current and future) identified at the Site are
summarized in Tabl* 13.
The HQ is calculated as follows:
Non-cancer HQ = CDI/R,D, where:
GDI = Chronic Daily Intake
R£D = reference dose; and
GDI and RfD are expressed in the same units and represent
the same exposure period (i.e., chronic, subchronic, or
short-term).
For carcinogens, risk are estimated as the incremental probability of an
individual developing cancer over a life-time as a result of exposure to the
carcinogen. Excess life-time cancer risk is calculated from the following
equation:
Risk = GDI x SF, where:
Risk = a unit less probability (e.g., 2 x 10*5) of an
individual developing cancer;
GDI =. chronic daily intake averaged over 70 years (mg/kg-
day); and
SF = slope-factor, expressed as (mg/kg-day)-1
Excess lifetime cancer risks are determined by multiplying the intake level
with the cancer potency factor. These risks are probabilities that are
generally expressed in scientific notation (i.e., 1 x 10"6 or 1E-6). An
excess lifetime cancer risk of 1E-6 indicates that, .as a plausible upper-
bound, an individual has a one in one million chance of developing cancer as a
result of site-related exposure to a carcinogen over a 70-year lifetime under
the specific exposure conditions at a site.
EPA has set an acceptable carcinogenic risk range of 1E-4 to 1E-6, but prefers
that remediation of Superfund sites achieve a residual cancer risk no greater
than 1E-6. However, depending upon site factors, a risk of 1E-4, may be
considered protective.
-------
-49-
NEH HANOVER COUNTY
AIRPORT BURN PIT
RECORD Or DECISION
TABLE 12 SLOPE FACTORS AND R£Ds USED TO ESTIMATE
CARCINOGENIC AND NON-CARCINOGENIC RISK
Parameter
Cancer Slop* Factor (CSP)
Cla««
Benzene
Oral
(ing/kg/day)-1
Inhalation
(ing/kg/day)-
Human Carcinogen
2.9 X 10'2A
2.9 X 10-2A
Reference
Doie (R,D)
Oral
(mg/kg/day)
Chloroform
B2
Probable Human Carcinogen
6.1 X 10-3A
8.1 X 10'2A
1,2-Dichloroethane
B2
Probable Human Carcinogen
9.1 X 10-2A
9.1 X 10'2A
Ethylbenzene
Not Classifiable As To Human
Carcinogenicity
Chromium (+6)
Human Carcinogen
N/A
4.1 X
1 X 10-»A
(3 X 10-»)'A
5 X 10-3A
Lead
B2
Probable Human Carcinogen
NOTES'.
*
A
N/A
Inhalation reference dose
A quantitative assessment for lead cannot be performed as EPA has withdrawn its toxicity
criteria.
Integrated Risk Information System (IRIS)
Not available. There is inadequate evidence for carcinogenicity of hexavalent chromium by
the oral route.
-------
NEW HANOVER COUNTY
AIRPORT BORN PIT
RECORD OF DECISION
-SO-
TABLE 13 HUMAN HEALTH RISK
Parameter
Ingeation Risk
(Intake * CSF)
Inhalation Riak
(Intake * CSF)
Ingeation
Hazard Index
(Intake/RfD)
Benzene
Chloroform
1 , 2 -Dichloroethane
Ethylbenzene
3.7 x 10-5
7.9 x 10-7
7.5 x 10-6
/\/\/v
3.7 x 10-5
1.0 x 10-5
7.5 x 10-6
/V^N/S,
/V/\ /V
/^ /^^
/^/V/V
0.06
(O.oo2)a
4 i - "S^f-o.'?^
HS3RGJU
Chromium (+6)
xv/\/v 1t
0.45
Lead
TOTAL RISK
1 X 10-4
TOTAL HAZARD
<1
NOTES: a — Inhalation hazard index
A/v/v — Indicates that a risk value could not be calculated.
Chromium does not have an oral CSF.
* — Metals are not likely to volatilize from groundwater due to
their physical/chemical properties
CSF — Cancer slope factor
RfD — Reference Dose
-------
HW HANOVER CODNTt
AIRPORT BOHN PIT
RECORD OF DECISION
-51-
The carcinogenic upper-bound risk for each of the exposure pathways (current
and future) identified at the Site are summarized in Tabla 13. The
accumulative future risk and hazard index posed by the Site is 1 x 10'* and
<1, respectively.
8.5 RISK UHCERTAIHTY
There is a generally recognized uncertainty in human risk values developed
from experimental data. This is primarily due to the uncertainty of
extrapolation in the areas of (1) high to low dose exposure and (2) animal
data to values that are protective of human health. The Site specific
uncertainty is mainly in the degree of accuracy of the exposure assumptions.
The risk assessment is aimed at providing a conservative estimate of risk for
the Site. A number of uncertainty and assumptions made throughout the risk
assessment are likely to result in an overall overestimation rather than an
underestimation of risk. Soil samples may not necessarily be representative
of the Site in its present condition. It is likely that all contaminated
soils were removed in the PRP remediation and that surficial soils may not
pose a risk, however, since there is a lack of surficial soil data this could
not be verified. The exposure scenario also involves a number of
uncertainties. Consumption of 2 liters of contaminated drinking water per day
for 350 days a year represents the upper bound of potential exposure and has
been used because site-specific data were not available. This may be an
overestimation of the actual exposure that may occur in the future. The
scenario assumes that an adult is consistently being exposed to the same
concentrations for 30 years. The daily intake by ingestion is reported as
being equal to the daily intake by ingestion; the use of this assumption
yields an almost equal risk for the inhalation scenario. Dermal absorption of
vapor phase chemicals is considered to be lower than inhalation intakes in
many instances and is not considered in this risk assessment.
As a result of the uncertainties and assumptions described above, the risk
assessment is a conservative analysis intended to indicate the potential for
adverse impacts to occur and not an absolute estimate of risk to humans or a
specific population.
8.6 gCOLOCICAL RISK
An endangered species survey was conducted at the Site on April 15 and 16,
1991. Observations were scheduled from 5:00 a.m. in the morning to 7:00 p.m.
in the evening in order to encompass both nocturnal and diurnal fauna
foraging. Floral observations were conducted during the mid-morning and
mid-afternoon to maximize observation time. No endangered flora or fauna
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NW HANOVER COUHT*
AIRPORT BORN PIT
RECORD OF DECISION
-52-
species were identified during this survey. The flora diversity is typical
for a coastal range area which has undergone significant disturbance,
remediation, and subsequent re-vegetation. Grasses are the dominant
vegetation at the Site interspersed with wild strawberries, hay-scented fern,
and poison ivy. The fringe (ecotone) immediately adjacent to the Site is
dominated by scrubs including magnolia, poison sumac, southern bayberry, and
red maple. The dominant fauna observed were opossum, lizard and aerial
(passerine) species. Species diversity was limited due to poor habitat
suitability and stress, e.g. reforestation and urban impact including light
industry, roads, and housing adjacent to or nearby the Site.
8.7 SUMMARY
Actual or threatened releases of hazardous substances from this Site, if not
addressed by implementing the response action selected in this Record of
Decision, may present an imminent and substantial endangernjent to public
health, welfare, or the environment. Presently, no unacceptable current or
future risks were identified associated with the New Hanover Site; however,
concentrations of contaminants in the groundwater are above federal maximum
concentration levels and state groundwater quality standards.
The health risk posed by this NPL site is primarily from the future use of the
groundwater as a potable source. This is due to the presence of contaminants
at concentrations above EPA's MCLs for drinking water and the State of North
Carolina groundwater quality standards. These contaminants will be remediated
during the remedial action phase.
Presently, there is no known adverse impact on the eco-system resulting from
the Site.
9.0 DESCRIPTION OP ALTKRKXTIVBS
As stated previously, the 1990 removal action successfully remediated the
Site's soils and therefore, a 'No Action* alternative was the alternative
developed for soils.
Table 14 inventories those technologies that passed the initial screening for
remediating the contaminated groundwater. In the initial screening, process
options and entire technologies were eliminated from consideration if they are
difficult to implement due to Site constraints or contaminant characteristics,
or if the technology has not been proven to effectively control the
contaminants of concern. Table 14 also presents the results of the final
screening of the groundwater remediation technologies. Effectiveness,
implementability, and relative capital and operation and maintenance costs are
the criteria used for evaluating the technologies and process options in the
-------
MEM HANOVER COUNTY
AIRPORT BOSN PIT
RECORD or DECISION
-53-
final screening. Tabla li provides the rationale as to why certain
technologies were not retained for the detailed comparison. The process
options that were eliminated in the final screening are shaded.
The No Action alternative for soil and the retained five (5) groundwater
remediation' alternatives to address the estimated 9.7 million gallons of
contaminated groundwater are described below. As stated earlier, neither
surface water nor sediment remediation technologies were evaluated as these
environmental media do not exist at or near the Site and hence, have not been
adversely impacted by Site activities.
9.1 APPLICABLE OR RELEVAHT AND APPROPRIATE RBQTTIRBMgNTS (ARARa)
The environmental setting and the extent and characterization of the
contamination at the New Hanover Site were defined in Section 7.0.
Section 8.0 highlighted the human health and environmental risks posed by the
Site. Tabl* 8 lists the contaminants of concern observed in the groundwater
at the Site. This Section examines and specifies the cleanup goals for the
contaminants in the groundwater.
9.1.1 Action-Spacific ARARs
Action-specific requirements are technology-based and establish performance,
design, or other similar action-specific controls or regulations on activities
related to the management of hazardous substances or pollutants. Tabl* 15
lists all potential action-specific applicable or relevant and appropriate
requirements (ARARs).
9.1.2 rh*m1cal-Sp«elfic ARARa
Chemical-specific ARARs are concentration limits established by government
agencies for a number of contaminants in the environment. Chemical-specific
ARARs can also be derived in the Risk Assessment. Table 16 lists all of the
potential chemical-specific ARARs which may be pertinent at the New Hanover
Site. Discussed below is each environmental medium investigated at the New
Hanover Site as part of the RI and the associated chemical-specific ARARs.
As stated earlier, the 1990 PRP sponsored removal action successfully
remediated Site soils. Therefore, no additional cleanup goals, other than the
PRGs, were developed for Site soils.
As declared previous, the groundwater at the New Hanover Site is designated as
Class GA by the State and Class IIA/IIB by EPA. Since the groundwater above
the blue clay layer is a potential source of drinking water and the
-------
NEW HMWVER COUNTY
MRWRT BORN PIT
RECORD OP DECISION
-54-
groundwater below this layer is a source of drinking water, the groundwater
needs to be remediated to a level protective of public health and the
environment.
The Safe Drinking Water Act (SDWA) and North Carolina Administrative Code,
Title 15, Subchapter 2L (NCAC T15:02L.0202) establish MCLs and non-zero
maximum contaminant level goals (MCLGs) for numerous organic and inorganic
constituents. For contaminants that do not have either a federal or state
cleanup goal, risk-based remediation goal numbers were calculated. The
cleanup goals to be obtained at the New Hanover Site along with the source for
the stated goals are shown in Tabl* 17. This table lists the most stringent
state or federal requirements.
9.1.3 Location-Specific ARARa
Location-specific ARARs are design requirements or activity restrictions based
on the geographical and/or physical positions of the Site and its surrounding
area. These requirements and/or restrictions can be stipulated by federal,
state, or local governments. Tabl* 18 lists the location-specific ARARs that
apply at the New Hanover Site.
9.2 REMEDIAL ALTERNATIVES TO ADDRESS SOIL CONTAMINATION
The 'No Action* alternative was the only alternative included for the soils at
the New Hanover Site. This was made possible by the success of the 1990
removal action which effectively removed the source along with the
contaminated soils.
9.3 REMEDIAL ALTERNATIVES TO ADDRESS CROUNDWATBR CONTAMINATION
Five (5) alternatives were developed to address groundwater contamination at
the Site. They are:
Alternative GW1: No Action with Long Term Monitoring
Alternative GW2: Vertical Barrier/Cap
Alternative GW3: Groundwater Extraction and Physical Treatment (Air
Stripping) with Discharge to a Publicly Owned Treatment
Works (POTW)
Alternative GW4: Groundwater Extraction and Physical/Chemical Treatment
(Chromium Reduction, Metals Precipitation, and Air
Stripping) with Discharge via Spray Irrigation
-------
TABLE 14
Groundwitsf General
Response Actions
BsmsdJsl Technology
EVALUATION OF PROCESS OPTIONS
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
Proeus Option Effectiveness
tmplementablllty
Cost
Colectton
Treatment
Dtscharge
None
Access resticfons
Monitoring
Vertical bantera
Extraction
Physfcalfchemlcal
treatment
rtol applicable
Deed restrictions
Groundwaler monitoring
—[ Smrrywal
\wVlw Ww%^W)- 5^. \±&fj.ft.w f fjf j£f •
Does not achieve remedial action objectives
Effectiveness depends on continued future
knptemenlalon. Does not reduce contamination.
IfeeMfMdocumenfngcomflons. Does not
reduces risk by itself.
Elective, but susceptible to weathering. Capping
required to prevent mounting.
Effective If proprietary fetation chemicals are
used to ensure knpermeable barrier. Capping
required to prevent mounding.
Extradon weto
Prectollalton
Alrebtophg
p— •
required to prevent mourning.
Eftocfc* and relabto; conventional technology
Effective and relabto; conventional technology.
Requires sludge Disposal.
ERsctVe and relabto; Proper prekealment
required
ElfedveandreNabte; Proper orekeatment
required. Requkesdsposalol used carbon.
Effective and relabto
—I Chromium reduction Effeclve and ratable; Proper mentoring required.
Onsltedbcharge
onslledschanje
Spray Irrigatton
POTW
| Process option eimlnated from lirmer consktoraflor
Ptoelne to surface water
Effective and reiabte; Effluent needs to meet
required discharge imlte.
Efiecttveandrelable; Effluent needs to meet
required dtecharoe knits.
Effective and relable; Effluent needs to meet
required discharge Dmlts.
Not acceptable to local/public
government.
Legal requirements and authority
Alone, not acceptable to public/local
government
Readly Imptementabte, adequate safety
measures required when dggtog trench
None
NegligWecosl
Low capital, tow O&M
High capital, tow
maintenance.
Appropriate fixation chemicals Very high capital, low
would be required. Treatablllly maintenance.
tests may be required.
Readily Implemenlabte
ReadHyknplemenlabfe
Readily Imptementabte
Reaolylmptomentabto
Readily Imptementabte
ReadHy Imptementabte
Permit required; must provide storage
during cold and wet weather.
Further negotiations may be required
to ensure acceptance of treated water
byPOTW
Permll required
Permit required
Very high capital, tow
maintenance.
Ital, moderate O4M
High capital,
hlghOAM
Low capital,
towO&M
High capital, high O&M
High capital, moderate O&M
•
Moderate capital.
moderate O&M
Moderate capital.
moderate O&M
Low capital,
low O&M
Moderate capital.
low O&M
-------
MEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OP DECISION
-56-
TABLE 15 POTENTIAL ACTION-SPECIFIC ARARS FOR GROUNDWATER
FBP1KAL
Oroundwater Extraction and
Treatment
Resource Conservation and Recovery
Act (RCRA), as amended
Identification of Hazardous
Waste
Treatment of Hazardous Wastes
In a Unit
Requirements for Generation,
Storage, Transportation, and
Disposal of Hazardous Haste
safe Drinking Water Act (SDWA)
Primary Maximum Contaminant
Levels (MCL)
Maximum contaminant Level Goals
(MCLG)
Disposal - Discharge to surface
Water/PotTT
Clean Water Act (CWA)
Requires Best Available
Treatment Technology (BAT)
National Pollutant Discharge
Elimination System (NPDES)
Permit Regulation
42 U.S.C § 6901 et.
seq.
40 CFR 261
40 CFR 264.601
40 CFR 265.400
40 CFR 263
40 CFR 264
42 U.S.C § 3001 et.
seq.
40 CFR 142
40 CFR 142
50 FR 46936
(November 13, 1985)
33 U.S.C § 1351-1376
40 CFR 122
40 CFR 122 Subpart C
Federal requirements for classification and
identification of hazardous wastes.
Rules and requirements for the treatment of
hazardous wastes.
Regulates storage, transportation, and operation of
hazardous waste generators.
Primary MCLs are adopted for the protection of
human health but include ah analysis of feasibility
and cost of attainment.
EPA has also established MCLGs. The nonenforceable
standards are based on health criteria. The MCLGs
are goals for the nation's water supply.
Use of best available technology economically
achievable is required to control discharge of
toxic pollutants to POTW.
Use of best available technology economically
achievable for toxic pollutants discharged to
surface waters.
RA RA
RA RA
RA RA
RA
RA
RA
RA
RA RA
RA
RA
RA
RA
RA
RA
RA
RA
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-57-
NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OF DECISION
TABLE 15 POTENTIAL ACTION-SPECIFIC ARARa FOR GROUNDWA'.ER (CONTINUED)
W?«'#$»&48s!v&WS»«$W<«;'i <:&•>$•• -t-wx&A Xv*»3w!fft&«W KSVffi
Disposal - Discharge to Surface
Water/POTW
Clean Water Act (CHAl
Discharge must be consistent
with the requirements of a Water
Quality Management Plan approved
by EPA
Discharge must not Increase
contaminant concentrations in
off-site surface water
Super fund Amendments and
Reauthorization Act (SARA)
BTMP1
North Carolina Water Quality
Standards
North Carolina Groundwater
Standards
Wastewater Discharge to surface
Waters
North Carolina Air Pollution
Control Requirements
LOCAL
City of Wilmington POTW Discharge
Criteria
33 U.S.C § 1351-1376
40 CFR 122
S 121 (d)(2)(B)(lli)
42 U.S.C S 9601 et.
seq.
ISA NCAC chapter 2B
15A NCAC Chapter 2b
ISA NCAC Chapter 2H
ISA NCAC Chapter 2D
Article III
Section 12-76 to
12-162
Discharge must comply with EPA- approved Water
Quality Management Plan.
Selected remedial action must establish a standard
of control to maintain surface water quality.
Discharge must comply with Federal Water Quality
Criteria.
Surface water quality standards.
Groundwater quality standards, regulates injection
wells.
Regulates surface water discharge and discharge to
POTW.
Air pollution control air quality and emissions
standards.
Minimum quality standards for disposal to the
Northside POTW.
<4\vx&#tf&Y?*t*ft«j -
/>& '';: j&? ,', ; ' «fev -ifr*. ' *; im:
RA RA RA RA
RA - RA
RA RA RA
- RA - RA
RA RA RA RA
RA RA RA RA
RA RA RA
RA RA RA
NCAC - North Carolina Administrative Code
RA - Relevant and Appropriate
-------
-58-
NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OP DECISION
TABLE 16 POTENTIAL CHEMICAL-SPECIFIC ARARs FOR GROUNDWATER
FKDBRAL
Resource Conservation and
Recovery Act (RCRA), as
amended
RCRA Groundwater protection
Safe Drinking Water Act
(SOWA)
National Primary Drinking
Water Standards
Maximum Contaminant Level
Goals (MCLGs)
Clean Water Act (CWA)
Water Quality criteria
Comprehensive Environmental
Response, Compensation, and
Liability Act of 1980
(CERCLA)
Clean Air Act (CAA)
National Primary and
Secondary Ambient Air
Quality Standards
National Emissions
Standards for Hazardous Air
Pollutants (NESHAPs)
42 U.S.C §§ 6905,
6912, 6924, 6925
40 CFR Part 264
40 U.S.C § 300
40 CFR Part 141
Publication L. N2 99-
399, 100 Stat. 642
(1986)
33 U.S.C § 1251-1376
40 CFR Part 131
42 U.S.C § 9601 et.
seq.
40 U.S.C § 1857
40 CFR Part 50
40 CFR Part 61
Provides Cor groundwater protection
standards, general monitoring
requirements, and technical
requirements.
Establishes health-based standards
for public water systems (MCLs).
Establishes drinking water quality
goals set at levels of no known or
anticipated adverse health effects.
Sets criteria for water quality based
on toxicity to aquatic organisms and
human health.
Provides for response to hazardous
substances released into the
environment and the cleanup of
inactive hazardous waste disposal
sites.
Sets primary and secondary air
standards at levels to protect public
health and public welfare.
Provides emissions standard for
hazardous air pollutant for which no
ambient air quality standard exists.
No/Yes
Yes/Yes
Yes/Yes
No/Yes
Yes/Yes
Yes/Yes
Yes/Yes
The RCRA MCLs are relevant and
appropriate for groundwater at the
Site.
The MCLs for organic and inorganic
contaminants are applicable to the
groundwater contaminated by the Site
since it is a potential drinking
water source.
Proposed MCLGs for organic and
inorganic contaminants are
applicable to the groundwater used
for drinking water.
The AWQC for organic and Inorganic
contaminants are relevant and
appropriate.
Applicable to the New Hanover Site.
May be relevant or appropriate If
onsite treatment units are part of
remedial actions.
May be relevant or appropriate if
onsite treatment units are part of
remedial actions.
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NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OP DECISION
-59-
TABLE 16 POTENTIAL CHEMICAL-SPECIFIC ARARs FOR GROUNDWATER (CONTINUED)
JK'.'*£*S^ -.' */*-* Jr ? ^ ^C^ ^
gTATM
North Carolina Drinking
Water Act
North Carolina Drinking
Water and Groundwater
Standards
130A NCAC 311-327
15A NCAC Chapter 2L
Regulates water systems within the
state that supply drinking water that
may affect the public health.
Establishes groundwater classification
and water quality standards.
Applicable to groundwater at the Site.
No/Yes
Yes/No
Provides the state with the authority
needed to assume primary enforcement
responsibility under the federal act.
Guidelines for allowable levels of
toxic organic and inorganic compounds
in groundwater used for drinking
water. Applicable to ground:, iter at
the Site.
NCAC - North Carolina Administrative Code
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NEW HANOVER CODNTY
AIRPORT BORN PIT
RECORD O? DECISION
-60-
TABLE 17 GROUNDWATER REMEDIATION LEVELS
Contaminant
^a^^^Sxiit^!^^^^^
YV.14»»*il^ , j™ s ^*\VvOS\™>
Benzene
Chloroform
1, 2-Dichloroethane
Ethylbenzene
Kaximun
Concentration
Dataetad
(ng/1)
Remediation
Level
(ng/1}
Source of
Remediation
Level
^;yf^C;^^S^^^^^SI^^^ ^!
0.22
0.0034
0.0044
0.12
0.001
0.00019
0.00038
0.029
B
B
B
B
v."" "'"tj*. .woAv ^\^%^*^s«'4>^>?^^^^vAwMA»vci*isfrv v» ix-^^M^ v$&\'' '••is?** SKv^a-%^. wi-v -ft •> •'"• *J^ 2JX>"^^ %fjt*%>-*i.vs*&, •>•*$& S*^v.vw sx.jA -.-. •S-.-^x-.-x^-j 6¥^
Ssow***^1!^^ ^%*i^i|^s^**2W^?v^%y itw>^ ;s
Chromium
Lead
0.082
0.022
0.05
0.015
A/B
C
SOURCES FOR SPECIFIED REMEDIATION LEVELS
A - MCL
B - State Groundwater Quality Standards (NCAC 15-2L.0202)
C - Action Level - EPA, Region IV Established Action1 Level
Alternative GW5: Groundwater Extraction and Physical/Chemical Treatment
(Chromium Reduction and Metals Precipitation) with
Discharge to Surface Water (Smith Creek)
The costs proposed for the following remedial alternatives were developed
using a discount rate-of 10 percent over 30 years.
9.3.1 Alternative OWli Ho Action
The No Action alternative is included, as required by CERCLA and the National
Contingency Plan (NCP), to serve as a baseline for comparing the benefits
achieved through the other groundwater remediation measures. Under the No
Action alternative, the Site would be left "as is" without conducting any
further remedial actions. However, long term monitoring of existing
monitoring wells would be conducted to track changes in environmental quality
over an estimated 30-year period.
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-61-
NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OF DECISION
TABLE 18 POTENTIAL LOCATION-SPECIFIC ARARs
Resource Conservation
and Recovery Act
(RCRA), as amended
RCRA Location
Standards
Fish and Wildlife
Coordination Act
Floodplaln Management
Executive Order
Endangered Species Act
Wilderness Act
National Wildlife
Refuge System
42 U.S.C § 6901
40 CFR §
264.18(b)
16 U.S.C § 661-
666
Executive order
11988;
40 CFR 6.302
16 U.S.C § 1531
16 U.S.C S 1311
16 U.S.C 688
50 CFR 27
A TSD facility must be designed,
constructed, operated, and maintained to
avoid washout on a 100-year floodplaln.
This regulation requires that any federal
agency that proposes to modify a body of
water must consult with the U.S. Fish &
Wildlife Services. This requirement is
addressed under CWA S 404 Requirements.
Actions that are to occur in floodplaln
should avoid adverse effects, minimize
potential harm, restore and preserve
natural and beneficial value.
Requires action to conserve endangered
species or threatened species, including
consultation with the Department of
Interior.
Area must be administered in way as it
will leave it unimpaired as wilderness
and will preserve it as a wilderness.
Restricts activities within National
Wildlife Refuges.
No/Yes
No/Yes
No/No
No/Yes
No/No
No/No
Potential remedial alternatives within the
100-year floodplaln. Requirement is relevant
and appropriate.
Potential remedial alternatives may include
stream redirection during sediment dredging
activities. Potentially relevant and
appropriate.
Remedial actions are to prevent Incursion of
contaminated groundwater onto forc"|-ed
floodplain.
No threatened or endangered species or
critical habitats were identified In or near
the site.
No wilderness areas exist onsite or adjacent
to the site.
No wildlife refuge are exist onsite or
adjacent to the Site.
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HE» HANOVER COONTY
AIRPORT BURN PIT
RECORD 07 DECISION
-62-
A reduction in the levels of contamination may occur over time through natural
processes. If no biodegradation occurs, it is estimated that the levels of
benzene in the groundwater would remain above the groundwater cleanup goal for
over 100 years.
Although there is no current unacceptable risk associated with the
contaminated groundwater, this situation would change immediately if either a
potable well was installed near to or on the Site or if the plume migrates
northwest towards the private potable wells in the neighborhood located
1,100 feet in that direction. The reason there is no current risk is because
nobody in the vicinity of the Site is using the groundwater as a source of
drinking water. However, if a potable well was installed in or near the
plume, the risk would increase to 1 x 10~4. Since this alternative does not
involve any treatment or other remedial action, any reduction in the mobility,
toxicity, or volume (MTV) of the contaminants in the groundwater at the Site
would be the result of natural processes.
The No Action alternative could be readily implemented, and would not hinder
any future remedial actions. There are no capital costs associated with this
alternative; however, O&M costs would be incurred. O&M costs would include
the costs associated with the long-term monitoring effort and the need to
conduct long-term effectiveness and permanence reviews every five years when
hazardous materials are left at a site as required by Section 121(c) of
CERCLA. Capital Costs:
$ 0
PW O&M Costs: $215.000
Total PW Costs: $215,000.
Time to Implement: None
Estimated Period of Operation: 30 years
9.3.2 Alternative OW2i Vertical Barrier/Cap
This alternative involves containing the groundwater plume with a vertical
barrier (i.e., slurry wall) and the construction of an impermeable cap to
prevent precipitation to cause groundwater mounding within the area
encompassed by the vertical barrier. The vertical barrier would be
accomplished by employing a slurry wall to a depth of approximately 30 feet.
The slurry wall would be anchored in the 5 foot blue clay layer encountered
under the Site. Restrictions on future land use would be warranted.
Periodic sampling of the groundwater would take place in order to monitor
changes in both contaminant concentrations as well as defining the migration
of the plume. The need for additional monitoring and the frequency of the
sample monitoring would be resolved in the Remedial Design (RD).
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NEW HANOVER COUNTY
AIRPORT BORN PIT
RECORD OP DECISION
-63-
The capital costs include the installation of the slurry wall and the
construction of the cap. O&M costs would include maintenance of the cap,
periodic groundwater sampling, and the costs for conducting the 5 year reviews
as required by Section 121(c) of CERCLA.
Capital Costs: $ 925,900
PW O&M Costs: $ 161.800
Total PW Costs: $1,087,700
Time to Implement: 6 months for design and contractor
selection/8 months to construct
Estimated Period of Operation: 30 years
9.3.3 Alternative CW3; Oroundwater Extraction and Physical Treatment (Air
Stripping) with Discharge to POTW
This alternative involves the installation of a groundwater extraction system
to remove the 9.7 million gallons of contaminated groundwater, an air
stripping step to remove the VOCs, and discharging the treated groundwater to
the Northside POTW which is owned and operated by the City of Wilmington.
Groundwater would be extracted from within the plume and pumped to an onsite
treatment system. It is anticipated that the groundwater recovery system will
need three (3) extraction wells, each pumping at a rate of 5 gallons per
minute (gpm), to achieve the groundwater remediation. The air stripper will
achieve cleanup goals to meet the "below detection limit' for benzene
(i.e., 1.0 ug/1) requirement for discharge to the POTW. Treated groundwater
would flow from the air stripper to a sewer connection to the POTW. The point
of compliance for this alternative is the extent the plume has traveled in the
aquifer where levels of contaminants are above the cleanup goals specified in
Table 17.
Pretreatment of the groundwater may be required to remove total suspended
solids (TSS) and iron prior to air stripping. Pretreatment may consist of
clarification/equalization basins or multi-media filters to remove TSS
followed by either greensand filters or the addition of proprietary chemical
complexing agents to prevent iron from precipitating in the air stripping
tower. The sludge generated by this pretreatment step is .typically
non-hazardous. It will be tested to verify that it is non-hazardous. After
testing, the sludge will be disposed of in the most economical means. For
costing purposes, the use of a pretreatment system is included to avoid
fouling of the air stripper. It is assumed that no air quality control
equipment will be needed to capture VOCs released from the air stripper due to
their low concentrations in the groundwater.
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NEW HANOVER COUNT?
AIRPORT BORN PIT
RECORD OF DECISION
-64-
Even though two (2) heavy metals, chromium and lead, were included in the list
of chemicals of concern, no treatment step to remove these metals from the
extracted groundwater has been included in the treatment train for this
alternative. No treatment to remove these metals is warranted as the
analytical data presented Tables 5 and 7 clearly show that these metals are
below background levels and are not Site related. If these metals were Site
related contaminants, then they would have been detected more than once and at
levels significantly above those detected at this Site. Refer to Section 7.2
for the explanation of elevated chromium levels in the April 1991 groundwater
data.
The following work/information will need to be performed/generated in the RD:
additional groundwater modeling and aquifer testing, a treatability study to
size the groundwater treatment equipment, a resolution if a pretreatment step
is necessary and the specific technology to be used in the pretreatment step,
and a determination of how to dispose of any waste streams generated by the
Remedial Action (RA). Additional hydrogeological information is needed to
insure the extraction wells will accomplish their goals.
Capital Costs: $ 859,100
PW O&M Costs: §1,073.700
Total PW Costs: $1,932,800
Time to Implement: 6 months for design and contractor
selection/2 months to construct
Estimated Period of Operation: 4.5 years
9.3.4 Alternative OWit Oroundvater ExtractJen and Physical/Chemical
Trea*'iTt'yt (C**y<
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HO) HANOVER COUNTY
AIRPORT BORN PIT
RECORD OF DECISION
-65-
press. The water recovered from the dewatering operation would be recycled to
the treatment's influent stream, and the concentrated sludge/filter cake
analyzed and disposed offsite at a hazardous or solid waste landfill, as
applicable. The treated effluent from the filter would be discharged to the
air stripper to remove the VOCs. Following the air stripper, the treated
groundwater would then be pumped to the onsite spray irrigation system.
Operation of the extraction system during wet weather or freezing temperature
conditions requires provisions for sufficient storage of treated groundwater.
The following information will be generated in the RD: additional groundwater
modeling and aquifer testing to insure the extraction wells will accomplish
their goals, evaluate adequacy of existing groundwater monitoring system and
install additional monitoring wells if necessary, a treatability study to size
the equipment to treat the extracted groundwater, and a determination on what
to do with the typically non-hazardous sludge generated by the metals removal
step and the typically hazardous waste stream created by the chromium removal
process.
Capital Costs: $1,053,900
PW O&M Costs: SI.265,200
Total PW Costs: $2,319,100
Time to Implement: 6 months to design and select contractor/3
months to construct
Estimated Period of Operation: 4.5 years
9.3.5 Alternative GW5: Qro^^dwateir 1*ytractl.op »«d Phygj.cal/Chy^cal
Treatment (Chromium Reduction and Metala Precipitation) with
PJ8charo« to Surface Water
This alternative involves the installation of a groundwater extraction system
to remove the 9.7 million gallons of contaminated groundwater, chromium
reduction and metals precipitation, and discharge of the treated groundwater
to Smith Creek located approximately 4,000 feet south of the Site. The
groundwater extraction system would be identical to that described in Section
9.3.3. The metals removal process is defined in Section 9.3.4. Following the
removal of the metals, the treated groundwater would be piped and discharged
into Smith Creek via an NPDES permit. The point of compliance is the same as
specified in Alternatives GW3 and GW4. The RD would need to develop the same
range of information as described in Alternative GW4.
Capital Costs: $1,132,500
PW O&M Costs: $1.194,500
Total PW Costs: $2,327,000
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NW HANOVER COONTY
AIRPORT BURN PIT
RECORD OF DECISION
-66-
Time to Implement: 6 months for design and contractor
selection/4 months to construct and obtain
NPDES permit
Estimated Period of Operation: 5 years
10.0 SUMMARY OP COMPARATIVE AHXLYSIS OP ALTBRNXTIVB3
Section 9.0 describes the remedial alternatives that were evaluated in the
detailed analysis of alternatives set forth in the Remedial Investigation and
Feasibility Study Reports. This section summarizes the detailed evaluation of
these remedial alternatives in accordance with the nine (9) criteria specified
in the NCP, 40 CFR Section 300.430(e)(9)(iii). This section only summarizes
the comparison of the groundwater remedial alternatives as the "No Action*
remedial alternative was selected for the soils.
10.1 THRESHOLD CRITERIA
In order for an alternative to be eligible for selection, it must be
protective of both human health and the environment and comply with ARARs;
however, the requirement to comply with ARARs can be waived in accordance to
40 CFR Section 300.430(f)(1)(ii)(C). Table 19 summarizes the evaluation of
the (five) 5 groundwater remedial alternatives with respect to the threshold
criteria.
10.1.1 Overall Protection of Human Health in*^ the Environment
This criterion assesses the alternatives to determine whether they can
adequately protect human health and the environment from unacceptable risks
posed by the contamination at the Site. This assessment considers both the
short-term and long-term time frames.
As documented in the RI, no surface waters or sediments have been or could
adversely impacted by the Site. As a result of the 1990 removal action. Site
soils do not pose an unacceptable risk to either human health or the
environment under either current or future conditions at the Site.
Under current conditions, the groundwater does not pose an unacceptable risk
to human health or the environment. And in contemplating future use scenarios
for the Site in the Risk Assessment, the scenario that typically results in
manifesting the most protective risk, using contaminated groundwater as
potable water, the overall risk posed by the New Hanover Site is 1 x 10~4.
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tOH HANOVER COONTT
AIRPORT BURN PIT
RECORD Of DECISION
-67-
TABLE 19 SUMMARY OF THE THRESHOLD CRITERIA EVALUATION -
PUBLIC HEALTH AND ENVIRONMENTAL EFFECTS - OF -THE
ALTERNATIVES
'ff^^l^Ljul^^/^^^^' HH?
..-,''. •'•..• JMHB»«*"BUI>:vJ»dlWI«n*»W*Ty;::;-vy'::ii.i:-
GW1: No Action with Long
Term Monitoring
GW2 : Vertical Barrier/Cap
GW3 : Groundwater Extraction
and Physical Treatment
(Air Stripping) with
Discharge to POTW
GW4 : Groundwater Extraction
and Physical/Chemical
Treatment (Metals
Precipitation) with
Discharge via Onsite
Spray Irrigation
GW5: Groundwater Extraction
and Physical /Chemical
Treatment (Metals
Precipitation) with
Discharge to Surface
Water
^'4^'v'4^h? -^ $jv *j3Jj^^*Jjjj$!:
Does not eliminate any
exposure pathways or
reduce the level of
risk.
Offsite contaminant
migration would be
eliminated. Greatly
reduces potential risk
of ingest ion and
inhalation.
Offsite contaminant
migration would be
eliminated. Minimal
operation and
maintenance of treatment
system. Eliminates
potential risk of
ingestion and
inhalation.
Same as Alternative 3 .
Same as Alternative 3 .
- TfV^f^M* ytf ^ t\ii M * ^uW^-tl- S %
Not in compliance
Not in compliance
In compliance
In compliance
In compliance
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NB» HANOVER COONTY
AIRPORT BURN PIT
RECORD OF DECISION
-68-
Because the future risk posed by the contaminated groundwater is 1 x 10'*,
all five groundwater alternatives would be protective of human health and the
environment. However, as specified below the levels of contamination in the
groundwater exceed applicable or relevant and appropriate requirements for
groundwater.
10.1.2 Compliance vith Applicable or R«l«vant and Appropriate R«q\iir«nants
This criterion assesses the alternatives to determine whether they attain
ARARs under federal and state environmental laws, or provide justification for
waiving an ARAR. Section 9.1 defines the three types of ARARs:
action-specific, chemical-specific, and location-specific. Site-specific
ARARs are identified below.
MCLs and State groundwater quality standards are ARARs for Site groundwater.
By leaving contaminants above MCLs in the groundwater, neither Alternative GW1
nor GW2 would comply with these ARARs. Therefore, these alternatives would
not achieve the requirements of the NCP. Alternative GW3 through GW5 would
attain ARARs throughout the entire Site. Construction of the groundwater
recovery, treatment, and discharge system for Alternatives GW3 through GW5
would satisfy action-specific ARARs. The disposal of any sludge generated by
the groundwater treatment system will also comply with the appropriate ARARs.
10.2 PRIMARY BAIAMCING CRITERIA
These criteria are used to evaluate the overall effectiveness of a particular
remedial alternative. This evaluation is summarized in Tabl* 20.
10.2.1 Long-Tarm Egg«ctivan««a and P«man«Bc«
This criterion assesses the long-term effectiveness and permanence an
alternative will afford as well as the degree of certainty to which the
alternative will prove successful.
Under Alternatives GW1 and GW2, groundwater contamination would not be
actively remediated; therefore these alternatives cannot be considered to be
permanent or effective remedial solutions. The long-term effectiveness of
these two alternatives is questionable, because of the time it would require
for "Nature* to clean "Itself*. These remedies would rely on the natural
attenuation and the flowing groundwater to eventually remove all the
contaminants that have entered the groundwater at the Site. In effect,
Alternative GW2 would reduce the effectiveness of the natural attenuation
process.
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NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OF DECISION
-69-
TABLE 20 SUMMARY OF PRIMARY BALANCING CRITERIA EVALUATION OF THE ALTERNATIVES
GW1:
No Action/Long
Term Monitoring
Ongoing monitoring
of groundwater
contaminant levels
would be conducted
to assess
contaminants
migration. Does
not meet ARARs.
None.
None.
None.
215
GW2:
Vertical
Barrier/Cap
The potential for
offsite
contamination
migration is
greatly reduced.
ARARs are not met
at the Site.
Length of service
unknown (not
permanent)..
Greatly
reduces
mobility. No
reduction In
toxicity and
volume.
Potential
release of
organic
volatiles
during slurry
wall
installation.
Noise
nuisance due
to operation
of heavy
equipment.
Design of slurry wall and
Impermeable cap;
stormwater runoff drainage
and collection for cap.
Air monitoring during
implementation.
1.5
1,087.7
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NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OF DECISION
-70-
TABLE 20 SUMMARY OF PRIMARY BALANCING CRITERIA EVALUATION OF THE ALTERNATIVES (CONTINUED)
'4"f''
GW3:
Groundwater
Extraction and
Physical Treatment
(Air Stripping)
with Discharge to
POTW
permanent remedy.
ARARs are met.
Eliminates
M/T/V/ of
contaminants.
Eliminates
potential for
offslte
migration.
High degree of
risk reduction
for ingestion
and inhalation
of
groundwater.
Potential
release of
organic
volatiles
during
extraction
well
installation
and treatment
system
operation.
Noise
nuisance due
to operation
of drilling
equipment.
Design of extraction, treatment
and discharge systems. Air
stripping of benzene to 'below
detection limit* required.
Treatment of air stripping off-
gases may be required.
Pretreatment for total
suspended solids and iron may
be required. Discharge permit
acquisition under
consideration. Ongoing
monitoring of groundwater
contaminant levels and the
treatment system should be
conducted to assess extraction
and treatment systems
performance. Must meet City of
Wilmington POTW discharge
requirements and Clean Air Act
(CAA) requirements. No future
land use restriction would be
required.
4.5
1,932.8
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NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OP DECISION
-71-
TABLE 20 SUMMARY OF PRIMARY BALANCING CRITERIA EVALUATION OF THE ALTERNATIVES (CONTINUED)
GW4:
Groundwater
Extraction and
Physical/Chemical
Treatment
(chromium
.Reduction, Metals
Precipitation, and
Air Stripping)
with Discharge via
Spray Irrigation
Permanent remedy.
ARARs are met.
Eliminates
M/T/V/ of
contaminants.
Eliminates
potential for
offsite
migration.
Greatest
degree of risk
reduction for
ingestlon and
inhalation of
groundwater.
Potential
release of
organic
volatlles
during
extraction
well
installation
and treatment
system
operation.
Noise
nuisance due
to operation
of drilling
equipment.
Sludge/filter
cake
generation
from
precipitate.
Design of extraction, treatment
and discharge systems. Metals
precipitation should achieve NC
Drinking Water Quality
Standards for Inorganics. Air
stripping should achieve
standards for organlcs.
Treatment of air stripping off-
gases may be required.
Pretreatment for total
suspended solids and iron may
be required. Storage may be
required during wet weather and
under freezing temperature
conditions. Ongoing monitoring
of groundwater contaminant
levels and the treatment system
should be conducted to assess
extraction and treatment
systems performance. Must meet
NC Drinking Water Quality
Standards for groundwater and
CAA emissions requirements. No
land use restriction would be
required.
4.5
2,319.2
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NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD Of DECISION
-72-
TABLE 20 SUMMARY OF PRIMARY BALANCING CRITERIA EVALUATION OF THE ALTERNATIVES (CONTINUED)
GWS:
Groundwater
Extraction and
Physical/Chemical
Treatment
(Chromium
Reduction and
Metals
Precipitation)
with Discharge to
Surface Water
Permanent remedy.
ARARs are met.
Eliminates
M/T/V/ of
contaminants.
Eliminates
potential fpr
offslte
migration.
Reduce source
of groundwater
contamination.
Greatest
degree of risk
reduction for
Ingestion and
inhalation of
groundwater.
Potential
release of
organic
yolatiles
during
extraction
well
installation
and treatment
system
operation.
Noise
nuisance due
to operation
of drilling
equipment.
Sludge/filter
cake
generation
from
precipitate.
Design of extraction, treatment
and discharge systems. Metals
precipitation should achieve NC
Surface Water discharge
requirements for Inorganics. A
4,000 foot pipeline would be
required for discharge to Smith
Creek. Permit acquisition
under consideration. Ongoing
monitoring of groundwater
contaminant levels and the
treatment system should be
conducted to assess extraction
and treatment systems
performance. Must meet NC
Surface Water discharge
requirements. No land use
restriction would be required.
2,326.9
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NEV HMWVEK COUWTY
AIRPORT BOSN PIT
RECORD OP DECISION
-73-
Contaminant concentrations in the groundwater will be permanently reduced
through the groundwater extraction and treatment systems specified in
Alternatives GW3 through GW5.
10.2.2 Reduction of Mobility. Toxicity, or Voluma
This criterion assesses the degree to which the alternative employs recycling
or treatment to reduce MTV of the contaminants present at the Site.
Alternatives GW1 would not significantly reduce the mobility, toxicity, or
volume of contaminants in groundwater. Alternative GW2 would reduce the
mobility of the contaminants in the groundwater by impeding the natural flow
of groundwater through the use of a slurry wall and cap. Alternatives GW3
through GW5 would effectively reduce the mobility and volume of contaminants
in the aquifer through the groundwater recovery system. The groundwater
treatment processes for Alternatives GW3 and GW4 would completely comply with
the statutory preference for alternatives that reduce toxicity of
contaminants. Alternative GW5 would treat for metals, however, no definitive
treatment to reduce the toxicity of the organic contaminants is included in
this alternative.
10. .3 Short-T«rm Bff«etiv«n«««
This criterion assesses the short-term impact of an alternative to human
health and the environment. The impact during the actual implementation of
the remedial action is usually centered under this criterion.
All of the groundwater remediation alternatives can be implemented without
significant risk to the community or on-site workers and without adverse
environmental impacts.
10.2.4 Hnpl«m«ntability
This criterion assesses the ease or difficulty of implementing the alternative
in terms of technical and administrative feasibility and the availability of
services and materials.
None of the groundwater remediation alternatives pose significant concerns
regarding implementation. Design of the treatment systems for Alternatives
GW2 through GW5 cannot be completed until the discharge requirements are
defined. This determination is dependent on where the treated groundwater
will be discharged to. This decision will be finalized in the RD.
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NEW HANOVER COONTY
AIRPORT BORN PIT
RECORD OP DECISION
-74-
10.2.5 Coat
This criterion assesses the cost of an alternative in terms of total present
worth cost (PW). Total PW was calculated by combining the capital cost plus
the PW of the annual O&M costs. Capital cost includes engineering and design,
mobilization, Site development, equipment, construction, demobilization,
utilities, and sampling/analyses. Operating costs were calculated for
activities that continue after completion of construction, such as routine
operation and maintenance of treatment equipment, and groundwater monitoring.
The PW of an alternative is the amount of capital required to be deposited at
the present time at a given interest rate to yield the total amount necessary
to pay for initial construction costs and future expenditures, including O&M
and future replacement of capital equipment.
Total present worth costs for the soil alternative are:
Alternative SSI - No Action $ 0
Table 21 presents the total present worth costs for the groundwater
remediation alternatives.
10.3 MODIFYING CRITBRIA
State and community acceptance are modifying criteria that shall be considered
in selecting the remedial action.
10.3.1 State of Horth Carolina Acceptance
The State of North Carolina has reviewed and provided EPA with comments on the
reports and data from the RI and the FS. NCDEHNR has also reviewed the
Proposed Plan and EPA's preferred alternative and conditionally concurs with
the selected remedy as described in Section 11.0.
10 » 3 » 2
The Proposed Plan Fact Sheet was distributed to interested residents, to local
-ewspapers and radio and TV stations, and to local, State, and Federal
officials on June 8, 1992. The Proposed Plan public meeting was held in the
evening of June 11, 1992. The public comment period on the Proposed Plan
began June 11, 1992 and closed on August 12, 1992.
Only written comments submitted by a PRP were received during the public
comment period. The questions asked during the June 11, 1992 public meeting
and the Agency's response to the written comments are summarized in the
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HEW HANOVER COOWTY
AIRPORT BURN PIT
RECORD OF- DECISION
-75-
TABLE 21 SUMMARY OF PRESENT WORTH COSTS FOR REMEDIAL ACTION
ALTERNATIVES
GWl: No Action/Long Term Monitoring
GW2: Vertical Barrier /Cap
GW3: Groundwater Extraction and Physical
Treatment (Air Stripping) with Discharge
to POTW
GW4: Groundwater Extraction and
Physical/Chemical Treatment (Chromium
Reduction, Metals Precipitation, and Air
Stripping) with Discharge via Spray
Irrigation
GW5: Groundwater Extraction and
Physical/Chemical Treatment (Chromium
Reduction and Metals Precipitation) with
Discharge to Surface Water (Smith Creek)
-V- £•...; " - i^s^
0
925.9
859.1
1,053.9
1,132.5
&<&8$^V^ -iX- •• %«A,
215
161.8
1,073.7
1.265.2
1,194.5
f*k]|Brtfr^t ^'VftoGwnt*
||***tJi «MM» - •:
i^m^wto,, ,
215
1,087.7
1,932.8
2,319.1
2,327
Responsiveness Summary, Appendix A. Since no input was receive from the
community at large, it is infeasible to assess the community's acceptance of
the proposed remedy.
11.0 DESCRIPTION 07 THE SELECTED REMEDY
Alternative SSI was selected for the soil and Alternative GW3 for groundwater.
Briefly, the selected remedy for this Site is:
• no further action for Site soils;
• a one year period for the collection of additional data on the quality of
the groundwater;
• design and implementation of the groundwater remediation to be initiated
after the year of groundwater monitoring. The selected groundwater
remediation alternative consists of a groundwater extraction system, an
air stripping process to remove volatile organics, and a pipeline
discharging the treated groundwater to the Northside POTW system; and
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NEB HMWVER COUNTY
AIRPORT BORN PIT
RECORD OF DECISION
-76-
• a review of the existing groundwater monitoring system to insure proper
monitoring of groundwater quality and the effectiveness of the
groundwater extraction system. Additional monitoring wells will be added
to mitigate any deficiencies.
This remedy will reduce the levels of contamination in the groundwater to
below their Federal MCLs and State water quality standards.
11.1 PBRPORMAKCB STANDARDS TO BE ATTAPTED
Performance standards include any applicable or relevant and appropriate
standards/requirements, cleanup levels, or remediation levels to be achieved
by the remedial action. The performance standards to be met/attained by the
New Hanover remedial action include the following tables and Table 22:
• action-specific ARARs are inventoried in Tabl* 15,
• chemical-specific ARARs are inventoried in Table 16, and
• location-specific ARARs are inventoried in Tabla 18.
Tabl* 22 provides the remediation goals to be achieved at this Site. This
table also lists the risk level associated with each remediation goal. These
risks are based on the reasonable maximum exposure (RME) levels and summarizes
the information provided in Tables 10, 11, 12,. 13, and 17.
11.2 QROUKPWATBR RBMBDIATIOH
The groundwater remediation alternative selected for the New Hanover Site is
Alternative GW3 - Groundwater Extraction and Physical Treatment (Air
Stripping) with Discharge to POTW. A description of the selected remedial
alternative follows.
The contaminated aquifer will be remediated until the performance standards
specified in Table 22 are achieved. Figure 4 delineates the estimated
periphery of the plume emanating from the New Hanover Site. Following
treatment of the extracted groundwater, the groundwater will be discharged
into a sewer connection to the Northside POTW which is owned and operated by
the City of Wilmington. A sewer line exists along the perimeter roads to the
New Hanover County Airport.
It is anticipated that three (3) extracting wells, each pumping at a rate of
five (5) gpm will be necessary to achieve and maintain a sufficient drawdown
in the underlying aquifer to contain and remove the plume of contamination.
The extraction wells will be located within and near the periphery of the
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NEH HANOVER COUtRY
AIRPORT BURN PIT
RECORD 0? DECISION
-77-
TABLE 22 PERFORMANCE STANDARDS AND CORRESPONDING RISKS
Chemicals
of Concern
s «.v> SS-. •- V, ;• f, %v^ ^A%,
•• GRflSHEWRESli X\ &•£.',-. ••
*8WW*WT"*^ •• -
Benzene
Chloroform
1 . 2 -Dichloroethane
Ethylbenzene
Chromium
Lead
Remediation Levels
Performance
Goals
-'™|i~"<* ~ "ft- {=:
&>?&f&rc?«
1 ug/l
0.19 ug/l
0.38 ug/l
29 ug/l
50 ug/l
15 ug/l
Point of
Compliance
' < /EsJ^'- * ^ •. tr!
?&j&$K-*&&* $
The
Entire
Plume
of
Contaminated
Groundwater
Basis of
Goal
."&> s'^f^*?"'*^
i>>>^:k^\->'£i
State
State
State
State
State/MCL
Action Level
Corresponding Risk Levels
Chemical-Specific RME Risk
Cancer
jS'f" ' ± \> 'j'\'j'*'f '"
£k^&i^$' ***'*•*'
3 x 10-'
1 x 10-'
4 x 10-'
N/A
N/A
N/A
Non-cancer
\" s rv"< '- '
r -t - - ^ '•
N/A
N/A
N/A
0.008C
0.3'-c
___*
MCL - Maximum Concentration Level
Action Level - EPA, Region IV Established Action Level
State - State Groundwater Quality Standard (NCAC 15-2L.0202
K/A - Not Applicable
* - Chromium is not expected to volatilize during showering, and is
not considered a carcinogenic by the oral route.
* - No toxicity criteria available.
' - Value based on potential for noncarcinogenic effects, <1 will
not cause adverse effects.
plume. The extracted groundwater will be treated in an above-ground, on-site
air stripper. A pretreatinent step may be necessary to remove TSS and iron to
prevent fouling of the air stripper; however, due to the anticipated short
duration that the groundwater extraction system and air stripping unit may be
in operation, fouling of the air stripper may not be an impediment. The
necessity of a pretreatment step as well as the number, placement, and pumping
rate of the extraction wells will be determined in the RD. The air stripper
will be designed to achieve a less than 1 ug/l level of benzene in the
effluent. This 'less than 1 ug/l* (i.e., below detection) of benzene
concentration is a pretreatment requirement specified by the POTW. The
groundwater treatment process described above is not anticipated to generate
any by-products or waste streams.
Due to the possibility that biodegradation of the organic contaminants in the
groundwater is occurring, the design of the groundwater extraction, treatment,
and discharge parameters will not be started until after one additional year
of data on groundwater quality is collected.
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NEH HANOVER COUNTY
AIRPORT BURN PIT
RECORD OF DECISION
-78-
The goal of this remedial action is to restore the groiindwater to its
beneficial use, as defined in Section 7.3. Based on information obtained
during the RI, and the analysis of all of the remedial alternatives, EPA and
the State of North Carolina believe that the selected remedy may be able to
achieve this goal. Groundwater contamination may be especially persistent
below and just downgradient to where the burn pit use to be located, where
concentrations are relatively high. The ability"to achieve cleanup goals at
all points throughout the area of attainment, or plume, cannot be determined
until the extraction system has been implemented, modified as necessary, and
plume response monitored over time. If the selected remedy cannot meet the
specified performance standards, at all of the monitoring points during
implementation, the contingency measures and goals described in this section
may replace the selected remedy and goals for these portions of the plume.
Such contingency measures will, at a minimum, prevent further migration of the
plume and include a combination of containment technologies and institutional
controls. These measures are considered to be protective of human health and
the environment, and are technically practicable under the corresponding
circumstances.
The selected remedy will include groundwa.=r extraction for an estimated
period of 4 years, during which time the system's performance will be
carefully monitored on a regular basis and adjusted as warranted by the
performance data collected during operation. Modifications may include any or
all of the followings:
a) at individual wells where cleanup goals have been attained, pumping may
be discontinued;
b) alternating pumping at wells to eliminate stagnation points
c) pulse pumping to allow aquifer equilibration and encourage adsorbed
contaminants to partition into groundwater;
d) installation of additional extraction wells to facilitate or accelerate
cleanup of the contaminant plume.
To ensure that cleanup continues to be maintained, the aquifer will be
monitored at those wells where pumping has ceased on an occurrence of every
1 year following discontinuation of groundwater extraction.
If it is determined, on the basis of the preceding criteria and the system
performance data, that certain portions of the aquifer cannot be restored to
their beneficial use, all of the following measures involving long-term
management may occur, for an indefinite period of. time, as a modification of
the existing system:
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NEW HANOVER COUNTY
AIRPORT BURN PIT
RECORD OF DECISION
-79-
a) engineering controls such as physical barriers, or long-term gradient
control provided by low level pumping, as contaminant measure;
b) chemical-specific ARARs may be waived for the cleanup of those portions
of the aquifer based on the technical impracticability of achieving
further contaminant reduction;
c) institutional controls may be provided/maintained to restrict access to
those portions of the aquifer which remain above remediation goals;
d) continued monitoring of specified wells; and
e) periodic reevaluation of remedial technologies for groundwater
restoration.
The decision to invoke any or all of these measures may be made during a
periodic review of the remedial action, which will occur at 5 year intervals
in accordance with CERCLA Section 121(c).
11.3 ADDITIONAL CONDITIONS/ADDITIONAL DATA RBQUIRBMBHTS/MONITOR EXISTING
COHPITION3
In addition to delineating the work described above, this ROD and the RD will
also have to address a number of additional information/data requirements.
Since the RI was not able to completely delineate the extent of the
groundwater contamination, especially in the aquifer below the blue clay
layer, additional monitoring wells will need to be installed during the RD.
At a minimum, this effort will include the installation of at least two (2)
deep monitoring wells, completed below the blue clay layer. The analytical
data generated from samples collected from these deep wells will provide
sufficient information to determine if contaminants in the upper aquifer have
migrated into this lower aquifer. The placement of these and any additional
monitoring wells will be made after a review and evaluation of the existing
groundwater monitoring system. This review is to insure that the groundwater
monitoring system will provide adequate information to assess the long-term
quality of the groundwater and to demonstrate the effectiveness of the
groundwater extraction system. This review effort may also include additional
.-'oundwater modeling and aquifer testing. If a contaminant is found above its
groundwater remediation standard specified in Table 22, then the groundwater
extraction system will be extended to include this lower aquifer and all the
requirements specified in Sections 11.0, 11.1 and 11.2 of this ROD will apply
to the remediation of this lower aquifer.
In order to help establish a broader data base on groundwater quality and
establish whether or not biodegradation of the contaminants in the groundwater
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NEW HANOVER COWIY
AIRPORT BORN PIT
RECORD O? DECISION
-80-
is occurring, additional groundwater samples will be collected and analyzed.
Sampling will occur every four (4) months. These samples shall be collected
and analyzed for TCL VOCs and TAL metals.
11.A COST.
The total present worth costs for the selected alternative is $1,932,800. The
break down of this cost is specified below.
The present worth cost components of the extraction, air stripping, and
discharging to the local POTW are:
TOTAL CONSTRUCTION COST $ 859,100
PRESENT WORTH O&M COST $1,073,700
TOTAL PRESENT WORTH COST $1,932,800
12.0 STATUTORY DBTBRMIHATIOH
The selected remedy satisfies the requirements of Section 121 of CERCLA.
12.1 PROTECTION OP HUMAN HEALTH AMD THE ENVIROMMEHT
The selected remedy will permanently treat the groundwater. Dermal,
ingestion, and inhalation contact with Site contaminants will be eliminated
and risks posed by continued groundwater contamination will be abated.
12.2 COMPLIANCE WITH ARARS
The selected remedy will be designed to meet all Federal or more stringent
State environmental laws. A complete discussion of the ARARs which are to be
attained is included in Sections 9.1. These sections also describe the TBC
requirements.
12.3 COST-BFPBCTIVEHB3S
The selected groundwater remediation technology is more cost-effective than
the other acceptable alternatives considered. The selected remedy will
provide greater benefit for the cost because it permanently removes the
contaminants from the impacted aquifer.
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HEN HANOVER COURT
AIRPORT BURN PIT
RECORD OF DECISION
-81-
12.4 OTIIiIZATIOH OP PBRMMIBMT SOLUTIONS AMD ALTBRKXTIVB
TOCHHOLOGIBS OR KBSOURCB TECHNOLOGIES TO THE MMCIMOM EXTBOT PRACTICABLE
The selected remedy represents the maximum extent to which permanent solutions
and treatment can be practicably utilized for this action. Of the
alternatives that are protective of human health and the environment and
comply with ARARs, EPA and the State have determined that the selected remedy
provides the best balance of trade-offs in terms of: long-term effectiveness
and permanence; reduction in mobility, toxicity, or volume achieved through
treatment; short-term effectiveness, implementability, and cost; State and
community acceptance; and the statutory preference for treatment as a
principal element.
12.5 PREFERENCE FOR .TRBATMEHT A3 A PRINCIPAL ELEMENT
The preference for the treatment of contaminated groundwater is satisfied by
the use of the groundwater extraction system and air stripper to remove
volatile contaminants from the groundwater at the Site. Further treatment of
the discharged groundwater will be achieved at the POTW. The principal
threats at the Site will be eliminated by use of these treatment technologies.
13.0 SIOHIFICAMT CHAHQBS
CERCLA Section 117(b) requires an explanation of any significant changes from
the preferred alternative originally presented in the Proposed Plan
(Appendix B) . Below are the specific changes made in the ROD as well as the
supporting rationale for making those changes. The Proposed Plan was
disseminated to the public on June 8, 1992.
Table 2 of the Proposed Plan listed the contaminants of concern and their
corresponding remediation goals to be obtained by the remedial action. The
metal, beryllium, was included on this list as the concentration of this metal
detected in the groundwater at the Site was 1.4 ug/1 which was above the MCL
of 1.0 ug/1. However, the MCL for beryllium was revised since the
distribution of the Proposed Plan. The beryllium MCL revision, published in
the Federal Register on July 17, 1992 (Fed. Reg. 31,776 1992), changed the MCL
from 1 ug/1 to 4 ug/1. Consequently, the level of beryllium detected at the
Site, 1.4 ug/1, no longer exceeds the MCL; therefore, beryllium was deleted
from the list of chemicals of concern.
Table 2 of the Proposed Plan designated 5.0 ug/1, the MCL, as the cleanup goal
for the contaminant benzene instead of the State's groundwater water standard
of 1.0 ug/1. The MCL was selected as it was believed that 5.0 ug/1 was the
lowest concentration that current, laboratory analytical methodologies could
accurately and consistently detect. However, this is not the case. U.S. EPA
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HEM HANOVSR COUNTY
AIRPORT BURN PIT
RECORD OF DKISION
-82-
Method 602 can accurately and reliably detect concentrations of benzene down
in the 1 ug/1 concentration range. Consequently, the more stringent State
groundwater standard for benzene was incorporated into Table* 17 and 22 of
this ROD.
The Proposed Plan reported the cost for Alternative GW3 to be $1,152,100.
This cost, obtained from the May 18, 1992 draft Feasibility Study Report for
the New Hanover County Airport Burn Pit Superfund Site, was based on operating
the groundwater extraction and treatment system for 48 weeks. This duration
was calculated using an effective porosity of 5 percent for the affected
shallow aquifer. However, the Agency determined 5 percent for the effective
porosity was too low of a value for a silty, sand aquifer. The pumping
duration has been recalculated using the more appropriate value of 20 percent
for the effective porosity. The recalculation is as follows:
9,694,080 gallons x 3 pore volumes
__________________^___________^_______ = 3.7 years.
5 gpm x 3 extraction wells x 525,600 min/year
Based on the recalculation, including design and implementation, the duration
of the groundwater extraction and treatment system increased from 48 weeks to
4.5 years. Consequently, the cost of Alternative GW3 and the other
alternatives that involved pumping and treating increased. The cost for
Alternative GW3 rose from $1,152,100 in the Proposed Plan to $1,932,800.00 in
the ROD.
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APPENDIX A
CONCURRENCE LETTER FROM THE STATE OF NORTH CAROLINA
AND RESPONSE FROM THE AGENCY
-------
State of North Carolina
Department of Environment, Health, and,Natural Resources
Division of Solid Waste Management
James G. Martin, Governor William L Meyer
William W. Cobey, Jr., Secretary 24 September 1992 Director
Mr. Jon K. Bornholm
Remedial Project Manager
US Environmental Protection Agency
Region IV
345 Courtland Street, NE
Atlanta, GA 30365
RE: Concurrence on Record of Decision
New Hanover County Airport Burn Pit NPL Site
Wilmington, New Hanover County, NC
Dear Mr. Bornholm:
We have received and reviewed your responses to comments made on the Draft
Record of Decision. The Division of Solid Waste Management concurs with the_selected
remedial alternative with the following exception. The remediation goal for benzene at the
Site should be 1 ug/1. Benzene can be accurately detected at or below this level by US EPA
Method 602. Any deviation from this remediaton goal will require a waiver from the North
Carolina Division of Environmental Management. Areas wnere state water quality
standards are not achieved will require deed recordation.
If there are any questions, please call me at (919) 733-4996.
Sincerely,
Depu
cc: Curt Fehn, US EPA
Perry Nelson, NC DEM
P. O. Box 27687, Raleigh, North Carolina 27611-7687 Telephone S >-733-4996
An Equal Opportunity Affirmative Action Employer
-------
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION IV
345 COURTLAND STREET. N.E.
ATLANTA. GEORGIA 3O365
SEP 25 1992
4WD-NCRS
Mr. Michael A. Kelly
Deputy Director
North Carolina Department of Environment,
Health, and Natural Resources
Division of Solid Waste Management
P.O. Box 27687
Raleigh, North Carolina 27611-7687
RE : State ' s Concurrence on the New Hanover County Airport
Burn Pit Superfund Site Record of Decision
Dear Mr. Kelly:
EPA-Region IV appreciates the State's concurrence on the Record of Decision (ROD)
for the New Hanover County Airport Burn Pit Superfund Site located in Wilmington,
North Carolina. For the record, EPA would like to respond to your September 24,
1992 concurrence letter. Your letter, along with this response, will be included
in Appendix A of the ROD. These letters should stand as official documentation
that EPA-Region IV and North Carolina Department of Environment, Health, and
Natural Resources have agreed on the preferred alternatives at this point in
time.
For your information, the Agency has incorporated the States 's groundwater
standard of 1.0 ug/1 for benzene as the performance standard in the ROD. And th«
Agency recognizes that the Stat« may in the future put in place, pursuant to
State law (General Statute 130A-310.8), a deed recorda- ion/restrict ion to
document the presence of residual contamination which may -imit the future use
of the property.
Please contact me at (404)3457-7791 if you have any questions or comments
regarding this matter.
Sincerely yours, ••"•:
Jon K. Bornholm
Remedial Project Manager
cc: Curt Fehn, EPA
John Walch, NCDEHNR
Printed on Recycled Paper
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APPENDIX B
PROPOSED PLAN FACT SHEET
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