r/EPA
United States
Environmental Protection
Agency
Dynamic Field Activity Case Study:
Soil and Sediment Cleanup, Loring Air Force Base
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Office of Solid Waste and
Emergency Response (5201G)
EPA/540/R-02/006
OSWER No. 9200.1-44
April 2003
Dynamic Field Activity Case Study:
Soil and Sediment Cleanup,
Loring Air Force Base
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Notice
This document has been funded by the United States Environmental Protection Agency (EPA)
under Contract 68-W-02-033. The document was subjected to the Agency's administrative and
expert review and was approved for publication as an EPA document. Mention of trade names
or commercial products does not constitute endorsement or recommendation for use.
ill
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IV
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Acknowledgments
The Office of Emergency and Remedial Response would like to acknowledge and thank the
individuals who reviewed and provided comments on draft documents. The reviewers include
EPA headquarters and regional offices, state environmental programs, United States Department
of Defense, United States Department of Energy, and representatives from the private sector.
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VI
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Contents
Notice iii
Acknowledgments v
Exhibits viii
Abbreviations ix
Abstract 1
Background 1
Using a Systematic Planning Process 1
Reviewing Existing Site Information 4
Selecting the Project Personnel 4
Identifying the Remedial Objectives 6
Refining the Conceptual Site Model 6
Preparing Sampling and Measurement Strategies 7
Screening Sampling Strategy 7
Initial Removal Strategy 7
Confirmation Sampling Strategy 8
Final Removal Strategy 8
Disposition Strategy 8
Selection of Appropriate Equipment and Contractors 9
Writing a Dynamic Work Plan 9
Conducting the Dynamic Field Activity 10
Writing a Final Report 17
Estimated Cost and Time Savings 17
Lessons Learned 18
Coordination of Team Members 18
On-Site Data Generation 19
References 20
Appendix A: Data Management Plan Summary A-1
Appendix B: Quality Assurance Project Plan Summary B-1
VII
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Exhibits
Number Title
1 Operable Unit 13—Basewide Surface Water Sediment 2
2 Flight Line Drainage Ditch Wetland 3
3 Flightline Drainage Ditch Wetlands Remediation Goals For Constituents of
Concern 5
4 Fish Tissue Remediation Goals for Constituents of Concern 5
5 Screening Sampling Decision Tree 11
6 Confirmation Sampling Decision Tree 12
7 Excavation Decision Tree 13
8 Screening Sampling Data Management Flow Diagram 14
9 Screening Sample Locations for FLDD Wetlands 16
10 Analytical Cost Comparison for Flightline Drainage Ditch Wetlands
(Soils/Sediments) 18
VIM
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Abbreviations
BCT BRAC Cleanup Team
BRAC Base Realignment and Closure
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
DDD di chl orodiphenyl di chl oroethane
DDE di chl orodiphenyl di chl oroethene
DDT di chl orodiphenyltri chl oroethane
DEP Department of Environmental Protection
DQO data quality objective
ECD electron capture detector
EPA U.S. Environmental Protection Agency
FID flame ionization detector
GC gas chromatograph
GPS global positioning system
IT information technology
OU operable unit
PAH polyaromatic hydrocarbon
PCB polychlorinated biphenyl
QA quality assurance
QAPP quality assurance project plan
QC quality control
RI remedial investigation
TCLP toxicity characteristic leaching procedure
TSCA Toxic Substances Control Act
XRF x-ray fluorescence
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Dynamic Field Activity Case Study:
Soil and Sediment Cleanup, Lor ing Air Force Base
Abstract
The Air Force used a dynamic field activity (i.e., a project that combines on-site data
generation with on-site decision making) to meet CERCLA soil and sediment cleanup
requirements at Loring Air Force Base. The use of field-based analytical methods in the base-
wide surface water/sediment remediation action provided defensible data that met the project
objective of ensuring that soil and sediment contamination in excess of remediation goals would
not reach potential human and environmental receptors. The dynamic field activity saved the Air
Force more than 50 percent of the analytical costs and approximately 25 percent of the total
project cost by helping to compress the remediation and restoration schedule from three to two
construction seasons (i.e., May through October).
Background
Loring Air Force Base, located near Limestone, Maine, and the Canadian border, was a
9,000-acre military installation that began operation in 1952 and closed in September 1994 as
part of the Department of Defense Base Realignment and Closure (BRAC) process. During base
closure, the Air Force identified 15 operable units (OUs) requiring investigation. The CERCLA
remedial investigation/feasibility study (RI/FS) was completed in April 1997 for one of these,
OU-13—Basewide Surface Water/Sediment. The RI identified eight separate areas, presented in
Exhibit 1, that required remediation. This case study discusses the CERCLA remedial action
activities at one of these areas, the Flightline Drainage Ditch Wetlands, and provides a
description of how dynamic field activities can be used for site cleanup.
The Flightline Drainage Ditch Wetlands, illustrated in Exhibit 2, are located between a
spill containment facility and a trout stream, the East Branch of Greenlaw Brook. The spill
containment facility was a clay-lined detention basin designed to prevent fuel spills and other
contaminants from traveling from the flightline through the Flightline Drainage Ditch and
downstream into environmentally sensitive areas. Discharges from the spill containment facility
flowed into the 20-acre Flightline Drainage Ditch Wetlands. These wetlands contained a number
of small ponds created by a series of beaver dams that acted as sediment basins. During the
CERCLA RI/FS, investigators found a number of contaminants of concern in these wetlands,
including PCBs, lead, DDT/DDD/DDE, chlordane, and PAHs. Water flowing from the
Flightline Drainage Ditch and associated wetlands continued toward the East Branch of
Greenlaw Brook, which was used for fishing both on and off the Base.
Using a Systematic Planning Process
The dynamic field activity for the Flightline Drainage Ditch Wetlands remedial action
was guided by EPA's seven-step data quality objective (DQO) process (EPA 1994a). The
systematic planning process included the following information:
• Reviewing existing site information;
• Selecting the project personnel;
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Exhibit 1
Operable Unit 13—Basewide Surface Water Sediment
LORING AIR FORCE
BASE BOUNDARY
NOSE DOCK AREA
DRAINWAYS
SPILL
CONTAINMENT
FACILITY
UNDERGROUND
TRANSFORMER
SITE WETLAND
STORM SEWER
DRAINLINE
FLIGHT LINE
DRAINAGE DITCH
EAST BRANCH OF
GREENLAW BROOK
FLIGHT LINE DRAINAGE
DITCH WETLAND
NOTE: AU ARtAS ABE PAfll OF
OKRA81E UNIT 13 EXCEPT
AS NOTED.
4000
I
8000
I
SCALE IN FEET
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I
a)
+- 0)
a)
c
0)
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• Identifying the objectives;
• Refining the conceptual site model;
• Preparing sampling and measurement strategies; and
• Selecting appropriate analytical methods, equipment, and contractors.
Reviewing Existing Site Information
Based on the RI, the BRAC Cleanup Team knew:
• The Flightline Drainage Ditch Wetlands consisted of a drainage ditch that was below the
watertable and an accompanying floodplain;
• The contaminants of concern included PCBs, lead, chlordane, PAHs, and 4,4-
DDT/DDD/DDE (see Exhibit 3); and
• The concentrations of a number of constituents of concern were elevated in fish tissue.
Exhibit 4 indicates that PCB concentrations (derived from Aroclor-1260) in fish tissue
were almost 1,000 times the remediation goal which was based on human health effects
from the consumption offish and almost 70 times higher than a level at which there
would be an observable effect in the fish themselves.
Selecting the Project Personnel
The BRAC Cleanup Team consisted of remedial project managers and supporting staff
from the Air Force, EPA, and State of Maine, as well as the Air Force contractor. This group
established a mutually agreed upon decision-making chain-of-command for the oversight of the
work. Since the approach to this remediation was dynamic, the Air Force's prime contractor
proposed a planning team whose members were very qualified and experienced in their areas of
responsibility. The positions and qualifications of the team included:
Project manager: A civil engineer with more than 20 years of engineering and
management experience. His primary functions were providing client relations,
management oversight of site activities, and ensuring that adequate resources were
available to the remediation team. He functioned out of the home office.
Project engineer/technical team leader: A civil engineer with more than 20 years of
engineering and environmental management experience. He filled the role of a technical
team leader by ensuring implementation of the work plan and overseeing the work. Since
the decision-making process for the soil removal project was not as complicated as other
dynamic field activities (e.g., complex characterization activities), he was able to spend
part of his time in the home office and part in the field. While he was off-site, he used the
project's website for real-time data management, while a very experienced construction
engineer oversaw the field activities.
Project geologist: A geologist with more than 10 years of experience in environmental
work. His primary responsibility was to oversee the collection of environmental and
geotechnical soil and sediment samples. He was on site for the entire length of the
remedial action.
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Exhibit 3
Flightline Drainage Ditch Wetlands
Remediation Goals For Constituents of Concern
Constituent of
Concern
PCBs(Aroclor-1260)
Lead
Total 4,4- DDT/DDD/DDE
Total Chlordane
Benzo(a)anthracene
Benzo(a)pyrene
Benzo(b)fluoranthene
Benzo(k)fluoranthene
Chrysene
Dibenz(a,h)anthracene
lndeno(1 ,2,3-c,d)pyrene
Total PAH
Ditch Sediment (mg/kg)
1.0
218
0.350
0.6
51.4
5.14
51.4
514
5,140
5.14
51.4
35
5.0
155
0.372
0.315
51.4
5.14
51.4
514
5,140
5.14
51.4
597
Exhibit 4
Fish Tissue Remediation Goals for Constituents of Concern
Constituent of
Concern
PCBs(Aroclor1260)
PCBs(Aroclor1242)
4,4 -DDT
4,4 -DDE
4,4 -ODD
Heptaclor
Chlordane, Alpha
Chlordane, Gamma
Maximum Detected
Concentration in
Fish Tissue (mg/kg)
2.1
0.074
0.14
0.044
0.076
0.0031
0.042
0.014
Remediation
Goal for Fish
Tissue1
(mg/kg)
0.0022
0.0022
0.013
0.013
0.18
0.00098
0.0034
0.0034
Fish Tissue LOEC2
(mg/kg)
0.0312
0.031
>0.4
1.09
0.6
4.5
not available
not available
1 Based on human health effects.
2 Lowest Observed Effect Concentrations for fish tissue residues based on information provided by NOAA and
included in the Environmental Residue-Effects Database (ERAD).
Project chemist: The project chemist was responsible for developing the quality assurance
project plan (QAPP) and sampling strategy. He was available for consultation at the
home office. His background included more than 20 years experience in analytical
chemistry and QA/QC.
Construction supervisor: A civil engineer with more than 20 years of construction
experience. His primary responsibility was oversight of the construction contractors. He
was on site for the entire length of the remedial action.
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Data management: A data manager worked full time on the project. He was a chemist,
supported by information technology (IT) staff, and had more than 20 years experience in
analytical chemistry and data management. He divided his time between the site and
home office.
Identifying the Remedial Objectives
Because the RI/FS identified consumption of contaminated fish as a major route of
human exposure, the BRAC Cleanup Team's goals included the need to eliminate contaminated
sediment transport from the Flightline Drainage Ditch into the adjoining wetland and the East
Branch of Greenlaw Brook, including its associated wetlands. As a result, the BRAC Cleanup
Team developed a number of DQOs to ensure that the remedial action would prevent soils and
sediments with contamination levels in excess of their remediation goals from reaching potential
human and environmental receptors, particularly through elimination of PCB exposure to the
food chain. The DQOs included:
• Analytical data will be of sufficient quality and quantity to guide site activities. To meet
this objective, screening results will be compared with applicable site-specific
remediation goals to determine the remediation boundaries for each site and to define
areas that may exceed Toxic Substances Control Act (TSCA) criteria and the toxicity
characteristic leaching procedure (TCLP) hazardous waste criteria. In addition,
confirmatory analysis will be of sufficient quality to demonstrate that soils remaining
after remediation do not contain target analytes above remediation goals.
• Disposition analysis (i.e., analysis of removed soil and sediments for waste
characterization and disposal) will be of sufficient quality to be compared with TSCA
criteria, including the disposition of PCBs, and TCLP criteria, which controls the
disposition of metals or pesticides.
• Data on soil and sediment classification will be of sufficient quality and quantity to
recreate the stream and wetland to its pre-contaminated condition.
Refining the Conceptual Site Model
The conceptual site model presented in the RI for the Flightline Drainage Ditch Wetlands
described two deposition scenarios that were known to have occurred based on Air Force Base
records and personnel interviews. The first deposition scenario was that contaminants of concern
had been released or disposed of into the Flightline Drainage Ditch and were transported
downstream during high water events (e.g., snow melts, excessive precipitation). When the ditch
overflowed its banks, these contaminants were distributed and deposited into the wetlands.
The second deposition scenario involved direct application of insecticide to control
blackflies and mosquitos. In addition, this scenario proposed that insecticides were mixed and
handled in the area upstream from the Flightline Drainage Ditch Wetlands. Upstream spills and
releases would then follow the first deposition scenario described above.
Both deposition scenarios included ongoing toxic exposure to flora and fauna in the
stream and wetlands. The RI had determined that the contaminants, especially PCBs, had
entered the food chain and were present in trout used for human consumption. In addition to the
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risk posed by fish consumption, the contaminants also presented a risk through direct dermal
contact and ingestion.
The BRAC Cleanup Team found the RI data inadequate for understanding the depth and
areal extent of sedimentation in the flood plain area. In addition, they could not determine
whether any stratification of contaminants existed within the sediment column. Consequently,
they planned to seek this information during the remedial design to ensure adequate cleanup.
Preparing Sampling and Measurement Strategies
The feasibility study called for the removal and disposal of soils and sediments with
contaminants of concern above the remediation goals (refer to Exhibit 3). In order to determine
which soils or sediments met these criteria, the BRAC Cleanup Team developed three strategic
sampling steps to identify contamination: screening sampling, confirmation sampling, and
disposition sampling. Because PCBs constituted 90 percent of the risk at the site, the strategy
focused on this contaminant in particular.
Screening Sampling Strategy
Before implementing the full screening program, the BRAC Cleanup Team decided to
sample obvious deposit!onal areas for stratification of PCB contamination to determine if
specific layers of sediments were more likely to be contaminated. To do this, the field team
planned to collect samples at 6-inch intervals to a depth of two feet or until they reached the
bottom of the sediment layer, whichever was less. The BRAC Cleanup Team intended to use
this information to decide whether to implement a simple random or a stratified sampling
strategy.
The field team would select screening samples by first dividing the drainage ditch into
transects every 100 feet. At each transect they would use their professional judgement to select
nearby sample locations that are likely areas of sedimentation. If the ditch was six feet across or
less, they would collect only one sample. If it was wider, they would collect as many as three
samples. They would also use known hot spot locations, found by this sampling event or
previous investigations, to select additional sampling locations that are half the distance to
adjacent samples.
They would then sample the floodplain by extending the transects into the wetlands. The
field team would decide the number and location of samples on these transects based on input
from the project wetlands specialist and the regulatory agencies. Exhibit 5 presents the decision
tree used for taking screening samples. Originally, the BRAC Cleanup Team planned to analyze
screening samples on site and send 10 percent off site for confirmation. However, during the
field work, modifications were made that increased the use of on-site analysis.
Initial Removal Strategy
If the analytical results of the screening sampling indicate that an area contained
soil/sediment above the remediation goals, the field team would remove an initial two feet of
soils/sediments.
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Confirmation Sampling Strategy
Once the field team completes the initial removal, they would implement a confirmation
sampling strategy over the same area to ensure that the remaining soil met established cleanup
criteria with a 90 percent confidence level for identifying hot spots. To do this they planned to
collect confirmation samples:
• Every 50 feet within the ditch;
• Where they suspected addition contamination; and
• Within the flood plain based on the statistical method recommended by EPA guidance
(U.S. EPA, 1989).
All of the confirmation samples would be analyzed at an off-site laboratory using SW-846
methods with 24- to 48-hour turnaround. Exhibit 6 shows the decision tree used for confirmation
sampling data. Note that this was the initial plan as it was approved. During the field work the
BRAC Cleanup Team made modifications to the plan that increased the use of on-site analysis.
Final Removal Strategy
If the analytical results from confirmation sampling indicate that cleanup criteria were not
met, the field team would remove two additional feet of soil and collect followup samples
according to EPA statistical sampling guidance (U.S. EPA, 1989). If the followup sampling
indicates that cleanup criteria still were not met, then they would place a geotextile layer over the
contaminated soil and cover it with clean soil (Exhibit 7 presents the decision logic on
excavation and remediation).
Disposition Strategy
The field team would consolidate all removed contaminated soils at a staging area where
they would perform disposition sampling in accordance with EPA solid waste sampling guidance
(U.S. EPA, 1997) and Maine DEP requirements. The original work plan called for the samples
to be analyzed by an off-site laboratory by the TCLP for metals and pesticides and by SW-846
method 8081 for PCBs. However, the BRAC Cleanup Team modified the planning documents
once the field laboratory demonstrated its ability to provide sufficient data quality.
After determining contaminant concentrations for the removed soil/sediment, the field
team planned to implement the disposal criteria described in the work plan. By taking advantage
of a base-operated landfill, the Air Force could save substantial resources on the less
contaminated waste. The disposal criteria, in accordance with EPA regulations, stated that the
field team would:
• Dispose of soil in the base landfill if the soil did not exhibit the RCRA characteristic for
toxicity based on TCLP analysis (for the metals and pesticides) and contained below 50
ppm of PCBs, as provided for in TSCA;
• Dispose of soil in a specially constructed cell within the base landfill if the soil did not
fail the TCLP but had greater than 50 ppm and less than 1,000 ppm of PCBs; and
• Dispose of soil at an off-site licensed hazardous waste landfill if it failed the TCLP and
could not be treated on site to universal treatment standards, or contained more than 1,000
ppm of PCBs.
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Selection of Appropriate Equipment and Contractors
The BRAC Cleanup Team selected the equipment and subcontractors needed to
implement this remedial action based on suggestions from the prime contractor. As a federal
project, the prime contractor competitively bid each contracting element and awarded them on a
time-and-materials basis with mobilization, demobilization, and standby charge provisions,
depending upon the service being contracted.
The prime contractor negotiated a contract with a local analytical company to provide
transportable GCs for on-site analysis of PCBs, pesticides, and PAHs as well as an XRF
instrument for on-site analysis of metals. In addition, the prime contractor retained two off-site
laboratories for confirmatory analysis of the on-site methods and for analysis of the confirmation
and disposition samples. The contracts included provision for both regular and quick turn-
around analysis (24 to 48 hours). These were indefinite quantity contracts which specified a
basic number of analyses and throughput with a provision for more up to a stated maximum (if
needed).
Note that the project used the term "confirmation" for two separate activities. The first
context refers to a sample that was split between the off-site and on-site laboratories to "confirm"
that field-based analytical methods were providing acceptable results. In the second context,
"confirmation" refers to a sample that was collected to determine if a discrete area met clean-up
criteria. These samples were not splits but they did have a high level of QA/QC applied to them.
Writing a Dynamic Work Plan
The BRAC Cleanup Team chose a dynamic approach because they believed it would
offer substantial cost savings by increasing the speed of decision making, thereby reducing the
time needed for site remediation and restoration. Because the cost savings depended on reducing
delays in decision making, there needed to be a significant amount of planning and pre-
agreement among the BRAC Cleanup Team members on how to handle potential problems.
In addition, the BRAC Cleanup Team worked closely with an organization of local
citizens, the Restoration Advisory Board, to ensure that the citizens understood the remediation
plan and how the remediation would reduce or eliminate risk of contaminant exposure, and that
they were comfortable with the decision-making process. Meetings were scheduled about every
other month and an open door policy was put in place so that community members could meet
with the Air Force remedial project manager to express concerns or ideas on an "as needed"
basis.
The overall quality assurance project plan for Loring Air Force Base provided for the
option of using either immunoassay test kits or transportable GCs for analysis of PAHs and
PCBs. However, in the year prior to the work on the Flightline Drainage Ditch Wetlands the
field team had used immunoassays for these analyses and encountered several problems,
including:
• The need to conduct numerous analyses of the same sample due to multiple decision
criteria for PCBs (i.e., less than 50 ppm, 50 to 1,000 ppm, greater thanl,000 ppm);
• Difficulty in achieving consistent results because field chemists were required to perform
numerous dilutions; and
• Clogged filters during extraction for some kits due to clayey soils.
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Consequently, the cost of analysis per sample location was higher than expected, and an
excessive number of samples were being sent off-site during the screening stage. Therefore the
BRAC Cleanup Team decided to exercise the option in the QAPP for using transportable GCs
instead of immunoassay test kits.
Based on discussions with the BRAC Cleanup Team and the Restoration Advisory Board,
and through the completion of the systematic planning process, the prime contractor developed a
dynamic work plan and associated field planning documents. These documents described the
following activities:
• On-site analysis of screening samples for PAHs, PCBs, and total petroleum hydrocarbons
(TPH) using transportable GCs. Note that use of on-site analysis expanded during field
work to include confirmation and no-further-action samples.
• Sampling, analytical, and excavation decisions by the field team according to decision
trees developed by the BRAC Cleanup Team (refer to Exhibits 5, 6, and 7).
• Selection of initial sampling locations based on professional understanding of
sedimentation zones. Probabilistic sampling would then be used to confirm removal of
contamination.
• Expedited distribution of all analytical data to stakeholders. During the second
construction season, the BRAC Cleanup Team would use a password protected website
for displaying data. The data management flow-chart used for determining which data
were added to the website is shown in Exhibit 8. In addition, Appendix A provides
detailed information on the approved data management plan.
After the BRAC Cleanup Team reviewed the plans, they made some minor modifications.
For instance, the State of Maine requested splitting a percentage of samples for analysis by their
laboratory in addition to any sent to an off-site commercial laboratory. Once the changes were in
place, they accepted the plans.
Conducting the Dynamic Field Activity
After the field team demonstrated it could achieve a high level of data quality with the
on-site GCs, the BRAC Cleanup Team allowed their use for analysis of confirmatory samples
with the stipulation that the off-site laboratory QA/QC protocols, provided in Appendix B, be
used. This decision changed the number of off-site analyses of samples used to determine if an
area met the cleanup criteria from the originally planned 100 percent to zero. However, the field
team still split 5 to 7 percent of the cleanup confirmation samples with the State of Maine to
verify that the on-site GCs were producing acceptable data. In addition, the BRAC Cleanup
Team changed the confirmatory analysis of screening samples from 10 percent to 5 to 7 percent
using the more stringent QC protocols at the on-site laboratory, and they allowed disposition
analysis for PCBs on-site using the more stringent QC protocols.
The field team selected the screening sampling locations as described in the dynamic
work plan. By the end of the Flightline Drainage Ditch Wetlands dynamic field activity, the field
team had collected screening samples at 271 locations in two stages. The first stage consisted of
a three-day period in late May 1997 when the field team collected 236 samples for on-site
analysis. Based on the results of these samples, they collected 35 additional samples at locations
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Exhibit 5
Screening Sampling Decision Tree
Collect Sample
Collect Position
Data
Analyze Sample
Air Force Concurrence
-Yes
Enter Site Specific
Geographic Data
Download Position
Data
Download Analytical
Results
Create Tables and
Figures
Additional
Sampling
Required
Air Force Concurrence
Delineation of
Contamination
BCT Review
Source: Bechtel Environmental, Inc. 1998b
11
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Exhibit 6
Confirmation Sampling Decision Tree
Download Analytical
Results
Remediation Goals
Achieved?
Source: Bechtel Environmental, Inc. 1998b
12
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Exhibit 7
Excavation Decision Tree
Excavate to 2 ft.
Confirmation sampling
and analysis
Restore per \
Interim Restoration Plans]
(IRP) (ABB/Woodlot) J
Confirmation sampling
and analysis
Restore per IRP or as
directed by BCT
Yes
BCT Consultation
''Place geotextile and\
over with a minimum 2ft
of common borrow and
restore per IRP or as I
directed by BCT /
13
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that contained high levels of chlordane in mid-June. These sampling locations are presented in
Exhibit 9.
The field team delivered samples to the on-site laboratory twice a day where they were
generally analyzed in the order they were received. However, the technical team leader was free
to move any sample to the front of the queue by designating it as critical. Because the BRAC
Cleanup Team set guidelines for determining the extent of initial excavations, the Air Force was
able to use the guidelines to make decisions quickly and confidently, knowing the regulators
would concur. As chemists analyzed the samples, the Air Force received recommendations from
the prime contractor on the areas requiring initial excavation. The field team then staked out the
areas chosen and recorded their locations with the GPS prior to beginning soil excavation.
Results also were made available to stakeholders at various levels of validation/verification
according to the data management plan.
When the BRAC Cleanup Team realized that approximately 70 percent of the wetlands
would require some excavation, they made a decision to perform confirmation sampling over the
whole site rather than just the excavated areas. These data provided further statistical evidence
that all of the hot spots in the wetlands had been identified. Altogether, they sampled and
analyzed 355 confirmation locations for PCBs, PAHs, chlordane, DDT/DDD/DDE, and lead. An
additional 6 locations were sampled and analyzed for PCBs only. Samples from 18 locations (5
percent) were split and analyzed by the State of Maine. It is also worth noting that they did not
send any confirmation samples to the commercial laboratories because the on-site laboratory
provided confirmatory level analysis (i.e., QC protocols were equivalent to the off-site
laboratory's, and the QC sample results gave them confidence in their data).
Based on the results of the confirmation sampling, the field team identified 35 areas
where remediation goals were not met. At 29 of these areas, regulators determined that
contamination levels were close enough to the remediation goals that no further excavation was
necessary for protection of human health and the environment. Consequently, the field team
covered these areas with two feet of soil/sediment that was comparable to what they had
removed. The six remaining areas, however, were still significantly above the remediation goals.
At these locations they removed two additional feet of soil/sediment. Follow-up confirmation
sampling again revealed that contamination was still present at levels significantly above the
remediation goals. After discussions with regulators, the field team covered these areas with a
geotextile and two feet of uncontaminated backfill soils. The remaining two feet at these
locations was covered with soil/sediment comparable in physical characteristics to what was
removed.
After the first construction season, the field team found it could correlate contaminant
concentrations in specific soil types to results from the TCLP analysis. Consequently, it
proposed to the BRAC Cleanup Team that it be allowed to use a surrogate to the TCLP. This
proposal was adopted during the second construction season, allowing the field team to replace
TCLP analysis with GC and XRF methods. Since six of the seven areas within OU-13, including
the Flightline Drainage Ditch, were remediated in 1997, this proposal was only used at the
remaining OU-13 area, which consisted of the Greenlaw Brook and its tributary, the East Branch
(refer to see Exhibit 2). After this decision was made, the field team completed all disposition
analyses on site.
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Writing a Final Report
The Air Force submitted a final Remedial Action Report for OU-13 in August 1999. The
remedial action at OU-13 required only eight months of field work spanning two construction
seasons (1997 and 1998). The Flightline Drainage Ditch Wetlands area, in particular, was
completely remediated in only three months of the 1997 season, and restoration activities were
concluded during the 1998 construction season. The Flightline Drainage Ditch Wetlands action
resulted in the removal and disposal of approximately 44,940 cubic yards of contaminated
sediment and soils. For all of OU-13, 152,328 cubic yards were excavated and disposed.
At the conclusion of the field work, the prime contractor conducted an evaluation of the
on-site versus off-site analytical results to determine whether an action would have been different
if off-site data were used instead of on-site data. They compared the on-site and off-site
laboratory results on 591 confirmation analyses from 112 split samples collected during the 1997
and 1998 construction seasons for the whole OU-13 (e.g., multiple analyses on each split may
have included lead, total chlordanes, total DDT/DDD/DDE, PCBs, and total PAHs). As
expected, the on-site laboratory GCs had higher detection limits than the off-site due to the
smaller extraction sample size of the on-site method. However, the evaluation found that the
same action would have occurred in 92.7 percent of the samples (548). In 6.4 percent (38
samples), the on-site laboratory indicated a false positive decision error with respect to the action
level (i.e., an action was taken that could have been avoided if the off-site data had been used).
In 0.9 percent (5 samples), the on-site laboratory indicated false negatives (i.e., an action should
have been taken but was not). This review indicated that the on-site laboratory operated within
the acceptable decision error rates specified in the QAPP. Consequently, the results of the off-
site laboratories and those of the on-site laboratory generally agreed, and the actions taken based
on these results were technically defensible.
Estimated Cost and Time Savings
Based on financial data obtained from the Loring Air Force Base remedial action, the use
of an on-site laboratory saved the Air Force more than 50 percent of the project's potential
analytical costs of off-site laboratories. Without the on-site laboratory, the field team would have
needed quick turnaround analysis from the off-site laboratories to keep the expensive removal
equipment operating. Exhibit 10 provides a summary of the actual analytical costs and compares
them to the prices listed in the work plan that the Air Force would have paid if they requested
quick turnaround off-site analysis. For the 1997 construction season, estimated cost for on-site
analysis of PCB/pesticides was $109.40 per sample; PAHs were $86.11 per sample; and lead
analysis by XRF was $6.25 per sample.
Use of the on-site laboratory for the Flightline Drainage Ditch Wetland saved the Air
Force more than $100,000 (i.e., $184,496 projected off-site costs minus $80,458 actual on-site
costs) in confirmation analysis costs alone. They saved additional resources through on-site
analysis of screening samples, but because of contractor labeling protocols, the savings from
screening samples for this area could not be separated from the overall project. The total on-site
laboratory costs for all of OU-13 were approximately $730,000. Had all the samples been
analyzed by an off-site laboratory, the cost to the project would have been $1,560,000.
Consequently, the on-site laboratory saved the project approximately $830,000, or over 50
percent the total analytical cost. Since the total cost of OU-13 was almost exactly $15,000,000,
the on-site analysis alone saved 5 percent of the total project cost.
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Exhibit 10
Analytical Cost Comparison for
Flightline Drainage Ditch Wetlands (Soils/Sediments)
Analyte
PCBs/
Pesticides
PAHs
Lead
Totals
Number of
Confirmation
Samples
Analysized1
402
395
395
On-site Cost
per Sample
$109.4
$86.10
$6.25
Actual On-site
Costs
$43,979
$34,010
$2,469
$80,458
Bid Rate for
Quick Turn for
Off-site Analysis
$264
$184
$14.40
Avoided Off-site
Analytical Costs
$106,128
$72,680
$5,688
$184,496
In addition, using a dynamic field activity provided the Air Force with further cost
savings because OU-13 required ecological restoration after the soil excavation was complete.
Early in the remediation process, the field team found that the flexibility provided by the on-site
laboratory allowed it to modify the general restoration plan in real-time to fit the remedial
excavation activities and begin the restoration efforts almost in tandem. Although the BRAC
Cleanup Team originally planned to do the remediation in two construction seasons and the
restoration in a third season, the restoration was actually completed with the removal activities in
the second construction season—saving a year in time and additional mobilization and labor
costs. Based on the fact that remediation of the entire site cost about $15,000,000 for less than
two full seasons of work, if a third season had been required, the project would have likely cost
at least another $5,000,000.
Lessons Learned
The BRAC Cleanup Team learned several lessons as it applied a number of innovative
techniques that differed from activities typical conducted during remedial actions. The following
points are taken from project reports and conversations with project personnel.
Coordination of Team Members
• Close coordination in the field among the prime contractor's sampling team, the Air
Force, Maine Department of Environmental Protection, and EPA provided for quick
problem-solving and helped streamline the sampling process.
• The project Internet home page was a very valuable tool because it allowed BRAC
Cleanup Team members to review data at remote locations, thereby speeding up the
decision-making process.
• In spite of the fact that disseminating analytical data to stakeholders in a timely manner
was labor intensive, the process saved resources for the project as a whole by aiding
decision making among BRAC Cleanup Team members.
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On-Site Data Generation
• On-site analysis enabled an expedited decision-making process which resulted in
substantial cost savings.
• The field team had difficulty using immunoassay test kits because these kits were
designed for targeting concentration ranges that did not match the project decision
criteria. The lesson from this experience was that while immunoassays do have their
place in dynamic field activities, their intended use should be scrutinized carefully before
choosing them over other available field-based analytical methods. In addition, a method
applicability study should be run on a few samples with site-specific matrices before
implementing an analytical program.
• Project planners can negotiate much lower prices on immunoassay test kits if they buy
large quantities directly from the manufacturer.
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References
Bechtel Environmental, Inc. 1997. Loring Air Force Base. Technical Memorandum:
Confirmation Analysis by On-site Laboratory. U.S. Air Force Center for Environmental
Excellence (AFCEE), Brooks Air Force Base, Texas.
Bechtel Environmental, Inc. 1998a. Loring Air Force Base, Remediation ofBasewide Surface
Water/Sediment (OU-13) and Removal at Base Exchange Service Station Wetland (OU-5),
Quality Assurance Project Plan, Revision 1. U. S. Air Force Center for Environmental
Excellence (AFCEE), Brooks Air Force Base, Texas.
Bechtel Environmental, Inc. 1998b. Loring Air Force Base, Remediation ofBasewide Surface
Water/Sediment (OU-13) and Removal at Base Exchange Service Station Wetland (OU-5), Field
Sampling Plan, Revision 1. U.S. Air Force Center for Environmental Excellence (AFCEE),
Brooks Air Force Base, Texas.
Bechtel Environmental, Inc. 1998c. Loring Air Force Base, Remediation ofBasewide Surface
Water/Sediment (OU-13) and Removal at Base Exchange Service Station Wetland (OU-5),
Remedial Action Work Plan, Revision 1. U.S. Air Force Center for Environmental Excellence
(AFCEE), Brooks Air Force Base, Texas.
Bechtel Environmental, Inc. 1998d. Loring Air Force Base, Remediation ofBasewide Surface
Water/Sediment (OU-13) and Removal at Base Exchange Service Station Wetland (OU-5),
Remedial Action Interim Report for 1997 Construction Season. U.S. Air Force Center for
Environmental Excellence (AFCEE), Brooks Air Force Base, Texas.
Bechtel Environmental, Inc. 1998e. Loring Air Force Base, Remediation ofBasewide Surface
Water/Sediment (OU-13) and Removal at Base Exchange Service Station Wetland (OU-5),
Remedial Action Work Plan, Addendum 1, April 1998. U.S. Air Force Center for Environmental
Excellence (AFCEE), Brooks Air Force Base, Texas.
Bechtel Environmental, Inc. 1998f Loring Air Force Base. OU-13 Data Management
Implementation Plan. U.S. Air Force Center for Environmental Excellence (AFCEE), Brooks
Air Force Base, Texas.
Bechtel Environmental, Inc. 1999. Loring Air Force Base, Remedial Action Report for
Flightline Drainage Ditch Wetlands, East Branch Greenlaw Brook Wetlands, Greenlaw Brook,
and Chapman Pit Manganese Sediment Removal Area, 1997 and 1998 Construction Seasons.
U.S. Air Force Center for Environmental Excellence (AFCEE), Brooks Air Force Base, Texas.
USEPA. 1989. Methods for Evaluating the Attainment of Cleanup Standards, Volume 1: Soils
and Solid Media, EPA/230/02-89/042.
USEPA. 1994. QA/G-4 Guidance for the Data Quality Objectives Process, EPA/600/R-96/055.
USEPA, 1997. Test Methods for Evaluating Solid Waste, SW-846. Office of Solid Waste,
Washington, DC.
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Appendix A
Data Management Plan Summary
Introduction
This summary is intended to provide the reader with an understanding of the structure of
a data management system (hardware/software), the personnel specifically required to operate it,
and the actual process used to ensure timely and reliable outputs. The goal of the process at
Loring Air Force Base was to provide raw data tables and visual aids within two days of data
collection, verify the data within three days, and verify the validated data within four days with
electronic posting at each stage for remote computer viewing by stakeholders.
Database Management Hardware Overview
The prime contractor used a server for storing the project data. The server consisted of
two computer systems capable of supporting GIS: one was in the prime contractor's home office
and the other on site. Supporting computers also were set up at the site office. Contractor staff
at the home office processed data that came from the site and off-site laboratory. The processed
data could be accessed directly from the site or other remote computers. The data also were
loaded on a website that was created to allow more convenient viewing by the Air Force and
other stakeholders.
Data Management Software Overview
The main data processing software included a relational database that contained several
boiler-plate formats for viewing data. The data were accessed directly by other compatible
software and were transferred into compatible software spreadsheet tables. In addition, the Air
Force used data visualization software that was compatible with a number of other data
visualization systems (e.g., Arclnfo®, Arc View®, Intergraph® MGE).
Staffing
Laboratory Liaison. The individual who tracked all data transmittal packages and maintained
communications with the on- and off-site laboratory facilities that were concerned with sampling
methods and testing controls.
Field Team. One or more individuals who ensured that field data (such as GPS surveying, well
construction, soil texture logging, soil testing for borrow) were properly recorded; field activities
were carried out according to procedures; and data quality was checked before the data were
transmitted to the home office for entry into the central database.
Data Management Coordinator. The individual who gave direction to the data management
specialist and ensured that the requirements of the Data Management Plan were met; that
hardcopy records were processed according to project requirements; and that verification/
validation activities occurred as planned.
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Data Management Specialist. The individual who ensured that all project information was
entered into the central database and that entered data were accurately processed. This individual
also assisted in the output of standard reports, pre-printed sample labels, and chain-of-custody
forms.
Data Verifier/Validator. Since turnaround time was important, this position required at least
two individuals (the number of individuals normally required varies depending on the site). The
verifier ensured that analytical and field measurement data fulfilled the requested laboratory
analyses and were verified as complete, within known ranges. The verifier performed a 10
percent completeness check on electronic deliverable data versus hardcopy and a 100 percent
check on review qualifiers. The validator determined whether the data were complete within
known ranges, the analyses were performed per method, and identified any problems. The
validator also qualified data that did not meet criteria.
GIS/Data Visualization Specialist. The individual(s) who: maintained consistent spatial data
across all the geographic study areas; developed interfaces between the spatial data component of
the maps and the associated data in the main database; and assisted in producing the visualization
products for the project field team, home office, and stakeholders. (At some sites, a GIS/Data
Visualization Specialist may be required in both the home office and in the field.)
Sample Data Management Work Processes
The following section describes the project team's actions that made the semi-real time
system work. Exhibit 8 presents a decision-tree flow diagram of the process.
Preplanning
Preplanning included designing a database. This activity involved identifying the data to
be collected and their associated data fields; then developing data flow regimes to identified
potential bottle-necks. In going through this process, the prime contractor discovered that it was
able to meet the project requirements with a pre-existing database structure, genetically
developed for other projects.
Sample Information Flow
Day 0. On day 0 the sample team collected the samples and completed the chain-of-custody
forms. Concurrent with the sampling, the sampling team collected GPS position data.
(Generally, if the number of sampling locations and their identification numbers are known
before the sampling takes place, this information can be entered into the main database and the
GPS before the sampling begins.) Samples were taken to the laboratory at noon and at the end of
the day (around 1700 hours). The drop-off times were shortened or lengthened depending upon
the distance to the on-site laboratory and other factors. Information on the chain-of-custody
documents was hand entered into the main database. The GPS data were returned to the field
office only at the end of the day.
Day 1. The Day 0 GPS data were post-processed to correct for signal degradation introduced by
the Department of Defense. (This no longer occurs.) The location data were then checked and
downloaded to the main database. The on-site laboratory completed analysis of the samples and
submitted an electronic data document and hardcopy to the laboratory liaison at the home office
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by the end of the day. (The liaison may be on site depending upon the costs of locating one
there.)
Day 2. After the laboratory liaison reviewed the data received at the end of Day 1 for any gross
errors, the electronic data document was downloaded to the main database and posted on the
project homepage in an Interim Results Table as unverified and unvalidated data. (Had
immunoassay results been involved, an electronic data document would have been created from
the field analytical logbook, since these measurements are not electronically generated.) By the
end of the day, a visualization software plot of the unverified and unvalidated data was created
and posted to the project homepage. To produce three-dimensional displays, the geologist's
subsurface soil descriptions were taken electronically in the field or transcribed at the home
office from hardcopy into software that was compatible for downloading with the main database.
Day 3. Screening data verification was performed on approximately 10 percent of the unverified
and unvalidated data posted on Day 2. Unacceptable data were resubmitted to the on-site
laboratory for rework. Acceptable data, classified as verified/unvalidated, were used to update
the main database. The verified/unvalidated results were posted to the project homepage,
replacing the unverified and unvalidated results posted on Day 2. The verified/unvalidated
results were then used to update the visualization software plot created on Day 2. The updated
plot was posted to the project homepage. Decisions made using the unverified and unvalidated
data were verified, and confirmation sampling data was 100 percent verified.
Day 4. Validation was performed on approximately 10 percent of the screening data posted on
Day 3 (100 percent of the confirmation sampling data was validated). Unacceptable data was
resubmitted to the on-site laboratory for rework and were reported as rejected in the main
database. After validation, the database was updated with the validation qualifiers, and the data
were noted as verified/validated. The updated visualization was posted to the project homepage.
Decisions made using the verified and unvalidated data were checked.
Data Access
The project set up several remote access methods to the data and GIS generated maps and
provided local access at the site and the home office. The project homepage allowed direct
access to the information via the Internet. A "Desk Top to Web Top" application was created.
Data owners who generated project information, such as database reports or maps, accessed files
on the project server. The project homepage contained hyperlinks to these files in their native
file format. When owners entered their desk top environment and performed their normal work
processes, project staff accessing the "web top" saw the latest information automatically. Data
were stored in one location only, thereby minimizing data processing and updating.
Three options were considered to supplement the project homepage and provide access to
data. One option would have provided access to the database and all standard prime home office
computing applications using a dial-up remote server access. The end user would have needed a
modem and a prime contractor remote server access software kit to utilize this option. Another
option would have provided access via a virtual private network, which is an extranet that allows
secure access to external users wanting to browse information within the prime's corporate
firewall. This option would have been more expensive than the first option because it requires
the user to have a hardware server with virtual private network client software installed. A third
option for accessing the database would have involved an intranet web account that was secured
within the prime's corporate firewall. The third option was chosen for this project because it did
not require the user to have any special hardware or software.
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Issues and Concerns
Data Entry. The majority of the data were generated electronically. Had field generated data
(e.g., analytical, geological, hydrogeological) not been produced electronically and thus hand
keyed, the level of effort required to produce the proposed turnaround times would have been
greater. (Although all field-generated data eventually have to be reduced to an electronic format,
costs increase when it has to be done within an expedited time frame.)
Data Verification and Validation. The prime contractor maintained its own relatively large
chemistry group that was capable of doing data validation and verification in-house. Hence it
had control of the process from start to finish. In many cases, this type of work is subcontracted.
(Involving a subcontractor presents a logistics and cost problem, since the subcontractor has to
maintain staff at the prime's home office or have the hardcopy data shipped to the prime, creating
an extra step. In addition, 24-hour turnaround times may increase the subcontractor's costs
because they make management of overall client workload more difficult.)
As noted above, this project did not require a large geology/hydrogeology effort.
However, the non-chemistry data required verification and validation in the same timeframe to
ensure that field decisions were based on accurate depictions of subsurface conditions.
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Appendix B
Quality Assurance Project Plan Summary
Introduction
The quality assurance project plan (QAPP) developed for Loring Air Force Base
addressed on-site and off-site performance requirements for the analysis of soil and sediment
samples. This summary emphasizes several details of the on-site activities that were called for in
the QAPP.
Off-Site Laboratory
SW-846 methods were used to conduct off-site laboratory analyses. The method
detection limits for the analyses were capable of detecting the contaminants of concern at the
remediation goal levels established for them (see Exhibit 3). State of Maine methods 4.1.25
(diesel range organics) and 4.2.17 (gasoline range organics) also were used. The QAPP set forth
precision, accuracy, completeness, representativeness, and comparability requirements for the
sampling and analysis. It also covered sampling and handling, number and type of QC samples,
and surrogate and control sample recovery requirements from the various applicable methods.
On-Site Laboratory and Analysis
In keeping with the structure of most dynamic work plans, the QAPP outlined the QA and
QC requirements for a variety of potential methods. While not all of them were used, pre-
approval was obtained from the regulators for them. The methods chosen for the field analysis
were:
• Soil Screening for PCBs by Immunoassay (Draft EPA Method 4020).
• Soil Screening for PAHs by Immunoassay (Draft EPA Method 4035).
• Soil Screening for Petroleum Hydrocarbons by Immunoassay (Draft EPA Method 4030).
• Soil Screening for Pesticides/PCBs by Gas Chromatography (Modified EPA Method
8081).
• Soil Screening for Petroleum Hydrocarbons by Gas Chromatography (Modified Maine
Methods 4.1.25 and 4.2.17).
• Soil Screening for PAHs by Gas Chromatography (Modified EPA Method 8100).
• Soil Screening for Lead and Zinc by X-Ray Fluorescence (EPA Field Analytical Support
Method F100.001).
• On-Site Confirmation Analysis for PAHs by Gas Chromatography (Modified EPA
Method 8100). Added in July 1997.
• On-Site Confirmation Analysis for Pesticides/PCBs by Gas Chromatography (Modified
EPA Method 8081). Added in July 1997.
The PCB and PAH immunoassay calibration instructions required standards to equilibrate
to ambient temperature before use. The calibration instructions also allowed users to follow the
instructions of any given test kit, since these are frequently revised, and to maintain all records
pertaining to calibration for review and assessment.
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For the two metals of concern (lead and zinc), the XRF calibration curves were generated
according to the manufacturer's instructions. The lowest standard was less than or equal to one-
half the associated remediation goal. The instrument was energy calibrated a minimum of once
per day with a pure copper standard or a standard recommended by the manufacturer.
Calibration curves were verified initially and at a 10 percent frequency on a continuing basis.
Samples from the field were ground to pass a pre-set sieve size.
The requirements for calibrating the on-site gas chromatographs reflected the quality
needed for the decision. For screening purposes, the following calibration steps were required:
• Initial calibration consisted of at least three standards for each target analyte. The lowest
standard was less than or equal to one-half the associated remediation goal.
• Acceptable calibration was achieved when the correlation coefficient of the curve (r) was
>0.995, or r2 was >0.9899, or the relative percent difference of calibration factors was less
than 30 percent.
• Continuing calibration was verified each day prior to sample analysis and for every 20
samples analyzed. The difference had to be within 20 percent.
For the GC, the project used a micro-extraction technique (Modified Spittler Extraction)
for obtaining samples for analysis rather than full volume extraction generally used in fixed
laboratories.
Since confirmation samples were used to determine if an area met the project's
remediation standards, their QC requirements were higher and consisted of the following:
• Calibration curves developed from a minimum of five standards. The relative percent
difference of the calibration factors had to be less than or equal to 20 percent or the
correlation coefficient (r) >0 .998.
• A daily calibration check standard was analyzed at the beginning of each day, and for the
analysis to continue, the percent difference (%D) was required to be less than or equal to
15 percent.
• Continuing and closing calibration checks were analyzed after every 10 injections/
analyses and at the end of the day. The acceptance criteria for the %D was less than or
equal to 15 percent.
In addition to the above, the on-site laboratory prepared and analyzed the following for
confirmation samples:
Method Blank. Method blanks were run at a frequency of one per preparation batch,
where a batch did not exceed 20 samples. If target analytes exceeded the practical
quantitation limit in the method blank then corrective actions were performed, which
included (but were not limited to) determining the source of contamination, reanalyzing
for the failed analytes and re-extracting/reanalyzing all associated samples.
Surrogate. Surrogates were added to each standard, blank, and sample. The laboratory
determined control limits for surrogate recovery on a matrix-specific basis and conformed
to the following requirements:
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Modified Method 8081 Organochlorine Pesticides and PCBs: Suggested
surrogates tetrachloro-m-xylene and decachlorobiphenyl with recovery limits in
soils of between 30 and 150 percent.
Modified Method 8100 PAHs: Suggested surrogates 2-fluorobiphenyl and 1-
fluoronaphthalene with control limits in soil that were laboratory-derived.
Matrix Spike/Matrix Spike Duplicate. MS/MSD pairs were prepared at a frequency of 1
per 20 samples per matrix. The recovery of the MS analyte had to meet the criteria of the
LCS for that analyte. (Had the recovery been outside the established limit, the MS would
have been analyzed again for that analyte. If the reanalysis also was out of control for
that analyte, then all affected samples would be qualified for that analyte.)
Laboratory Control Samples. LCS was prepared at a frequency of 1 per preparation
batch. A batch was not to exceed 20 samples. The laboratory determined control limits
for the LCS on an analyte-specific basis. The laboratory-determined limits fell within the
EPA established multi-laboratory control limits for the LCS. (Had the recovery of the
LCS been outside control limits, all samples associated with the LCS would have been
reanalyzed. If the recovery was still outside control limits, the entire batch would be re-
extracted and reanalyzed.)
Confirmation Sampling Grid Calculations
The following equations were used to calculate the number of samples and grid spacing:
long axis (L) = [hot spot area/* *x hot spot shape]05
grid interval (Gx) = L/(L/G) where (L/G) = 0.78
number of samples (n) = A/GX2
grid interval (G 0) = 0.866 x Gx
Based on the total excavation area, a hot spot size (described as a percent of the total
excavated area) was estimated, and the number of confirmation samples and maximum grid
spacing were calculated. The following conditions and parameters were assumed:
• A = the excavated area as measured at ground surface
• triangular grid is used
• expected shape (ES) of hot spot = 0.5 (ES = S/L, S is short axis length and L is long axis
length)
• area of hot spot ellipse = (3.14)(S)(L)
• L/G = 0.78 where G = grid interval (x-axis) and the tolerable false positive decision error
rate is 10 percent
• grid interval (y-axis) = (G)(.866) to account for the 30 degree angle (e.g., cos 30 = .866)
• grid nodes are offset by one half the x axis grid spacing (triangular grid)
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