The Air Force used principles of the Triad Approach to meet soil and sediment cleanup requirements under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) for base closure. Field-based analytical methods provided defensible data for polychlorinated biphenyls (PCBs), pesticides, polycyclic aromatic hydrocarbons (PAHs), and metals, which met the project objective of ensuring that soil and sediment contamination in excess of remediation goals would not reach human and environmental receptors. These methods produced an adaptive sampling program and a high-density data set of documented quality that managed uncertainty for the project stakeholders, allowing real-time decision making regarding contaminant extent, completeness of remediation (excavation), and disposition of remediated wastes in compliance with Toxic Substances Control Act (TSCA) and the Resource Conservation and Recovery Act (RCRA). The Triad Approach saved the Air Force more than 50 percent of the analytical costs and approximately 25 percent of the total project cost by eliminating the need for off-site laboratory analysis and further helping to compress the remediation and restoration schedule from three to two construction seasons (i.e., May through October).
|Site Name||Loring Air Force Base|
|Site Type||Surface Impoundment/Lagoon|
|Site Regulatory ID||EPA ID# ME9570024522/Site ID# 0101074|
|Project Lead Organization||Air Force Base Conversion Agency (AFBCA)|
|Project Lead Type||U.S. Air Force Lead|
|Regulatory Lead Program||Base Realignment and Closure (BRAC)|
|Triad Project Status||Field Program Completed|
|Reuse Objective Identified||Yes|
Loring Air Force Base (AFB) was a 9,000-acre military installation that began operation in 1952 and closed in September 1994 as part of the Base Realignment and Closure (BRAC) process. During base closure efforts, the Air Force identified 15 operable units (OUs) requiring investigation. A remedial investigation/feasibility study (RI/FS) was completed in April 1997 for OU-13 ? Basewide Surface Water/Sediment. The RI identified eight separate areas that required remediation, one of which was the Flightline Drainage Ditch Wetlands.
The Flightline Drainage Ditch Wetlands area is located between a spill containment facility and a trout stream, the East Branch of the Greenlaw Brook. The spill containment facility was a clay-lined detention basin designed to prevent fuel spills and other contamination from traveling from the flightline, through the Flightline Drainage Ditch, 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 RI/FS, investigators found a number of contaminants of concern in these wetlands, including PCBs, lead, dichlorodiphenyldichloroethane (DDD), dichlorodiphenyldichloroethylene (DDE), dichlorodiphenyltrichloroethane (DDT), chlordane and PAHs. Water flowing from the Flightline Drainage Ditch and associated wetlands continued towards the East Branch of Greenlaw Brook, which was used for fishing both on and off the Base.
The Air Force submitted a final Remedial Action Report for OU-13 in August 1999. The remedial action at OU-13 required only 8 months of field work spanning two construction seasons (1997 and 1998). The Flightline Drainage Ditch Wetlands area, in particular, was completely remediated in only 3 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. The evaluation found that the same action would have occurred for 92.7 percent of the samples. This review indicated that the on-site laboratory operated within the acceptable decision error rates specified in the Loring AFB basewide quality assurance project plan (QAPP). Therefore, the actions taken based on the results were technically defensible.
Consumption of contaminated fish from a popular fishing stream near the site was identified as a major route of human exposure. On this basis, the project team?s goals included the need to eliminate contaminated sediment transport from site source areas (a detention basin and drainage ditch) into the stream and its associated wetlands. Project objectives were developed as follows:
The Triad Approach helped to reduce the overall cleanup cost by saving time and money in the following ways:
Without the on-site laboratory, the field team would have needed quick turnaround analysis from off-site laboratories to keep the expensive removal equipment operating. Based on financial data obtained from the Air Force, the use of an on-site laboratory saved more than 50 percent of the project?s potential analytical costs for off-site laboratories (actual total analytical cost was approximately $730,000 versus total estimated cost of $1,560,000 using an off-site laboratory). Since the total cost of OU-13 was almost $15,000,000, the on-site analysis alone saved 5 percent of the total project cost.
In addition, using a Triad Approach 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 project 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 team originally planned to do the remediation in two construction seasons and the restoration in the 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. Because 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.
The conceptual site model (CSM) for the Flightline Drainage Ditch Wetlands described two deposition scenarios. The first scenario was the release of contaminants into the Flightline Drainage Ditch that were then transported downstream during high water events. When the ditch overflowed the banks, these contaminants were distributed and deposited into the wetlands. The second deposition scenario involved the direct application of insecticide to control black flies and mosquitoes. In addition, this scenario proposed that insecticides were mixed and handled in the area upstream from the Flightline Drainage Ditch. Upstream spills and releases would then follow the first deposition scenario.
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 risk posed by fish consumption, the contaminants also presented a risk through direct dermal contact and ingestion. The project team found the RI data inadequate for understanding the depth and areal extent of sedimentation in the flood plain area or any stratification of contaminants within the sediment column.
Based on discussions with the stakeholders, the project team developed a dynamic work strategy (DWS) work plan and associated field planning documents. These documents described the following activities:
The project team chose a DWS work plan 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, a significant amount of planning and pre-agreement was required by the project team and regulators on how to handle potential problems.
In addition, the project team worked closely with an organization of local citizens, the Restoration Advisory Board (RAB), 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 approximately 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.
Because the dynamic remediation and sampling program demanded sound, real-time decision making, the primary members of the project team were highly qualified and experienced in their areas of responsibility. Most of the project team spent much or all of their time in the field. In addition, due to the importance of interim data communication for real-time decision-making, the Data Manager was designated as full-time on the project to promote data integrity, completeness, and throughput.
The FS called for the removal and disposal of soils and sediments with contaminants of concern above the remediation goals. In order to determine which soils or sediments met these criteria, the project team developed a three-tiered sampling strategy 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 these contaminants.
The screening sampling strategy utilized a high-resolution site characterization (HRSC) approach, which involved collecting individual samples and transect samples at judgmental locations (with input from wetlands specialists and stakeholders) in the ditch and the surrounding wetlands and floodplain. These samples were collected in 6-inch intervals down to 2 feet deep (or the bottom of the sedimentation zone) in obvious depositional areas. If the analytical results of the screening sampling indicated that an area contained soil/sediment above the remediation goals, the field team would remove an initial 2 feet of soil/sediments.
Once the initial removal was completed, systematic grid confirmation sampling was initiated every 50 feet within the ditch, floodplain, or where additional contamination was suspected, collecting a sufficient number of samples for 90 percent statistical confidence based on EPA sampling guidance (EPA, 1989). Initially, all of the confirmation samples were intended for analysis at an off-site laboratory using SW-846 methods with 24- to 48-hour turnaround. However, during the field work the project team made modifications to the plan that increased the use of on-site analysis (see the Real-time Technologies section of this profile). If the analytical results from confirmation sampling were still above cleanup criteria, the field team removed an additional 2 feet of soil or sediment and repeated the grid sampling. If these follow-up grid samples indicated that cleanup criteria were still not met, then a geotextile layer was placed over the contaminated soil and covered with clean soil.
The field team consolidated all removed contaminated soils or sediments at a staging area where disposition sampling was performed in accordance with EPA SW-846 sampling guidance (EPA, 1997) and MEDEP requirements. The original work plan called for 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 project team again modified the planning documents to use on-site data for disposition, once the field laboratory demonstrated its ability to provide sufficient data quality (see the Real-time Technologies section of this profile).
After determining contaminant concentrations for the removed soil/sediments, 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 saved substantial resources on the less contaminated waste. The disposal criteria, in accordance with EPA regulations, stated that the field team would:
The DWS was captured in decision trees that were incorporated into the work plan. Examples of these decision trees are presented in a more detailed Case Study (PDF, 3.8 MB) that has been prepared for the Flightline Drainage Ditch cleanup. The decision trees incorporated the site-specific remediation goals for sediment that had been developed for Loring AFB cleanup programs. The decision trees also incorporated data deliverable preparation and review by project stakeholders. In addition to the decision trees, a more detailed data management and flow diagram was incorporated into the work plan (PDF, 3.8 MB).
Using a HRSC strategy, supported by the DWS work plan decision logic, the field team collected screening samples at 271 locations for on-site analysis in May and June 1997. Most of these samples (236) were collected over a 3-day period, with the remaining samples collected to further delineate chlordane hotspots based on the initial results.
When the on-site data indicated that approximately 70 percent of the wetlands would require some excavation, the project team modified the HRSC sampling approach 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 361 confirmation locations for PCBs, PAHs, chlordane, DDT/DDE/DDD, and lead.
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 confirmation 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 2 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 2 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 2 feet of uncontaminated backfill soils. The remaining 2 feet at these locations were covered with soil/sediment comparable in physical characteristics to what was removed.
The DWS work plan for the excavation program incorporated approved field-based methods that had been specified in the basewide QAPP for Loring AFB. The methods chosen for the field analysis were:
For the GC methods, the project used a micro-extraction technique (Modified Spittler Extraction) rather than full volume extraction generally used in fixed-based laboratories. Three-point calibrations (with correlation coefficients greater than 0.995 and calibration verifications every 20 samples) were used for GC screening analyses, whereas five-point calibrations consistent with SW-846 Method 8000 calibration criteria and frequency requirements were used for on-site confirmation analyses.
For lead, the XRF calibration was performed according to the manufacturer?s instructions, with the low standard less than or equal to one-half the associated remediation goal. Samples from the field were ground to pass a pre-set sieve size.
The field team delivered samples to the on-site laboratory twice per day where the samples were generally analyzed in the order that 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 project 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 project team on the areas requiring initial excavation. The team then staked out the areas chosen and recorded their locations with the global positioning system (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.
After the on-site laboratory demonstrated a high level of data quality with the GC methods, the project team and stakeholders allowed its use for analysis of confirmatory samples with the stipulation that full off-site laboratory quality assurance/quality control (QA/QC) protocols be used. This decision changed the number of off-site analyses for confirmation samples from the originally planned 100 percent to zero. However, the field team still split 5 to 7 percent of the cleanup confirmation samples with MEDEP to verify that the on-site GCs were producing acceptable data.
The on-site confirmation method was further adopted over the course of the field program for confirmation of the on-site screening data. Originally, the project team planned to analyze and send 10 percent of the screening samples off-site for confirmation. However, these confirmation samples were moved to the on-site laboratory and the project team was further able to reduce the percentage of off-site confirmatory analysis from 10 percent to 5 to 7 percent of the screening samples.
The team and stakeholders also allowed TSCA disposition analysis for PCBs to be performed on-site using the more stringent, "off-site" QA/QC protocols. Furthermore, during the first construction season, the field team found it could correlate total contaminant concentrations from the on-site analyses to TCLP results in certain soil types. Consequently, it proposed that on-site analysis be used as a substitute for the TCLP. This proposal was adopted during the second construction season, allowing the field team to replace TCLP analysis with GC and XRF methods. After this decision was made, the field team completed all disposition analyses at the on-site laboratory for OU-13.
As an additional note on the field-based methods, the basewide QAPP for Loring AFB provided for the option of using immunoassay (IA) test kits rather than transportable GCs for analysis of PCBs and PAHs. However, in the year prior to the work on the Flightline Drainage Ditch Wetlands, the field team had used IA test kits for these analyses and encountered several problems including difficulties in achieving consistent results and clogged filters during extraction for some of the kits due to clayey soils. Moreover, the IA test kits targeted concentration ranges that did not match the project decision criteria. Consequently, the cost of analysis per sample location was higher than expected and a higher number of samples than planned were being sent off site during the screening stage. Therefore, the project team decided to exercise the option in the QAPP for using transportable GCs instead of IA test kits.
TQRS not prepared
The basewide QAPP developed for Loring AFB addressed on-site and off-site performance requirements for the analysis of soil and sediment samples. Quality control (QC) was measured via the data quality indicators of accuracy, precision, representativeness, completeness, and comparability (PARCC). It also covered sampling and handling, number and type of QC samples, and surrogate and control sample recovery requirements from the various applicable methods. The frequency of collection and analysis of field and laboratory QC samples met the requirements of the QAPP. For on-site confirmation analyses, QC protocols (such as method blank, laboratory control sample, matrix spike/matrix spike duplicate (MS/MSD), and surrogate) were commensurate with EPA SW-846 guidance for GC methods. Additionally, confirmation samples from 18 locations were split and analyzed by MEDEP.
The overall decision uncertainty was lowered in a practical sense for the project stakeholders through the high-resolution, high-density data set. Additional QC practices were applied to further manage decision uncertainty and affirm data quality. For example, precision (replicate) samples were collected at locations where data showed concentrations near the remediation goal. These data were used to confirm that adequate sample preparation and homogenization occurred. The data were also used to determine if actions were required in areas where results were near the remediation goal. When results indicated matrix heterogeneity in a given area, the project team was able to increase the sampling density, at minimal cost impact, in those areas where incorrect decisions would be risky from a protectiveness aspect.
A project Internet home page was maintained so that project team members and stakeholders could review data from remote locations, thereby speeding up the decision-making process. This password-protected website contained daily and weekly reporting of data and analytical results. The website data management process also ensured that the progress was accurately tracked and that construction operations were in compliance with regulatory standards. 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 project team members.
The prime contractor used a server for storing the project data. The server consisted of two computer systems capable of supporting a geographic information system (GIS): one was in the contractor?s home office and the other on site. Supporting computers also were set up in 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 were also uploaded to the website to allow more convenient viewing by the Air Force and other stakeholders.
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., Arc Info, ArcView, Intergraph MGE).
|EPA. 2003. Dynamic Field Activity Case Study: Soil and Sediment Cleanup, Loring Air Force Base. Office of Solid Waste and Emergency Response (5201G), EPA/540/R-02/006. April. http://www.epa.gov/superfund/programs/dfa/casestudies/ (3.8 MB)|
|Public Health Assessment. Loring Air Force Base, Limestone, Aroostook County, Maine.|
To update this profile, contact Cheryl T. Johnson at Johnson.Cheryl@epa.gov or (703) 603-9045.