In the Spring of 2004, the U.S. Air Force (USAF) instituted the Florida Triad Initiative at three active installations representing different major commands. MacDill Air Force Base (MAFB), under the direction of the USAF Air Mobility Command, selected a Site Investigation (SI) and Cleanup Design at Area of Concern (AOC) 82, Building 35, to implement the Triad approach.
Systematic planning for the investigation began in September 2004. Highlights of the project from the Triad perspective include:
Field activities were initiated in October 2004, including a geophysical investigation that revealed the presence of multiple USTs not otherwise documented in archival documents. November 2004 activities included installation of piezometers, the collection of soil samples from 28 locations, and the collection of 11 DPT groundwater samples. Five monitoring wells were subsequently installed. In December and January, soil samples were collected from an additional 21 "step-out" locations per the dynamic work plan. The sampling programs revealed the presence of soil contaminated with Resource Conservation and Recovery Act (RCRA)-listed waste (chlordane), and groundwater contaminated above groundwater target levels. Because of funding constraints, additional groundwater investigations to delineate extent of aquifer contamination above target levels were stopped in order to focus on soil contamination issues. Subsequent sample efforts focused on additional soil samples for extent characterization (5 locations) and for listed waste refinement (18 locations).
A report produced in May 2005, "Triad Based Confirmatory Sampling Report for Area of Concern 82: Pesticide Storage Facility," captured the results of the soil sampling effort. It was determined that chlordane was the primary contaminant of concern in soils at the site. Chlordane-contaminated soils were delineated in three dimensions. Contaminated soil and the USTs were to be excavated and disposed of off-site in a future performance-based task.
|Site Name||Area of Concern (AOC) 82, Building 35, MacDill Air Force Base|
|Location||MacDill Air Force Base, FL|
|Site Regulatory ID||FL/EPA# FL6570024582|
|Project Lead Organization||MacDill Air Force Base staff|
|Project Lead Type||U.S. Air Force Lead|
|Regulatory Lead Program||RCRA Corrective Action|
|Triad Project Status||Field Program Completed|
|Reuse Objective Identified||Yes|
|Proposed Reuse:||Residential (preferred), Industrial (acceptable)|
AOC 82 is located within the industrial section of MAFB. The Site consists of Building 35 and surrounding lands encompassing an area of 6,000 square feet. Building 35 is a one-story concrete block structure with a footprint of roughly 600 square feet that was constructed in 1941 and that has been used as a gas and oil house, a liquid fueling and dispensing facility, a civil engineering (storage, pavement, and grounds) facility, and as a locksmith shop. Site history did not reveal the presence of USTs, although a relic fuel dispensing island and vent pipes suggested that USTs could be present. Given the potential presence of USTs and pesticide usage associated with a typical pavement and grounds shop, a number of potential release locations were integrated into a preliminary CSM including: the USTs, pump island, storage room areas, loading ramps, and a grassy area east of the building where pesticide container rinsing could have occurred.
There were insufficient funds to conduct interim remedial activities.
The primary project objective was to plan and execute an iterative Site Investigation (SI) and Remedial Investigation (RI) in an accelerated manner with a minimum number of field mobilizations, developing closure strategies for the site in a matter of months rather than years. Specific objectives for this site included the following:
This project was part of the U.S. Air Force’s (USAF’s) Florida Triad Initiative. The purpose of this initiative was to promote implementation of the Triad approach at three USAF facilities in the state of Florida and also to position the USAF for a broader future application of this approach in order to comply with new performance based management initiatives. More information on Initiative is available at the Florida Triad Initiative.
No formal cost comparison was performed.
Systematic planning for the Triad investigation at MAFB began in September 2004 with an initial meeting that included technical, managerial, and regulatory team members. Contractor personnel prepared the initial draft of the CSM for the AOC based on available data. The draft CSM for the site provided a description of potential release mechanisms, potential contaminants, and potential exposure pathways. The team refined the CSM based upon input from the first systematic planning meeting and additional site information as it was discovered. The team then developed sampling strategies to address specific questions regarding possible contamination at the site while fulfilling the State of Florida sampling requirements.
Uncertainty was managed by delineating to “clean” (per the definition agreed upon by the stakeholders) in three dimensions for soil, the assumption being that contaminated soil would be removed as part of an interim or final remedy.
The analytical strategy involved using a collaborative data set for pesticide contamination assessment. Results from the 24-hour microextraction analysis method were used to determine whether or not the more definitive method (EPA Method 8081B) should be used for archived samples.
Collaboration between the USAF, U.S. Army Corps of Engineers (USACE), USACE contractor, and FDEP staff was good in large measure because participants had a long history of interactions via partnering. The FDEP representative had confidence in the USACE and USACE contractor. As a result, the project team could build upon existing social capital in their application of the Triad approach.
The project team consisted of:
The project team was composed of professional and environmental engineers, risk assessors, biologists, professional geologists, and chemists. Additional technical oversight and Triad facilitation was provided by the Air Force Center for Environmental Excellence (AFCEE) and Argonne National Laboratory (ANL). Policy oversight was provided by U.S. Air Force Headquarters and Headquarters Air Mobility Command.
The executed work plan was not a true dynamic work strategy, but a coordinated set of several mobilizations targeted at swift site characterization and removal of USTs. The team determined that this was an acceptable mobilization method for the site due to the ease of site access during field efforts.
The approach involved the selection of sample locations based upon the potential release locations as identified during the first systematic planning meeting and described in the draft CSM. Soil sample locations were also established based upon geophysical investigation results; for example, inferred locations of vent lines, fill lines, and USTs, or OVA screening of soil sample locations. As results were received, “step out” soil sample locations were identified based upon the need to discover the extent of contamination above State of Florida soil cleanup target levels (SCTLs) and federal maximum contaminant levels (MCLs) for groundwater.
Decision logic was designed to characterize the site in a series of field activities that ultimately occurred over a 6-month time frame. The team developed field efforts to meet three overall data goals:
A geophysical investigation was conducted during the first field effort to confirm the presence or absence of USTs on the site. If USTs had not been detected, the tank investigation would have been closed. However, USTs were detected. The proper authorities were notified; the size and contents of the tanks were determined; and the USTs and integral piping were removed.
Piezometers were installed to evaluate the groundwater flow direction during the second field effort. Piezometer locations were determined based on previously accumulated site knowledge with no rigorous in-field decision logic applied.
Soil and groundwater sampling was conducted during the third field effort. A fast-turnaround microextraction method was used in conjunction with EPA SW-846 Method 8081B to identify soil and groundwater contaminated with chlordane and other pesticides. Microextraction was used to determine the concentration of chlordane in soils. All chlordane non-detect samples and 10 percent of all chlordane detected samples reported from the microextraction method were subsequently analyzed by the laboratory using Method 8081B. If microextraction analysis indicated that samples contained chlordane below the SCTLs or MCLs, the laboratory analyzed replicate samples using Method 8081B. If analysis indicated exceedance of the SCTL for chlordane at a sampling location, the field team stepped out to collect additional samples. This process continued until the field team fully delineated the horizontal and vertical limits of contamination in soil.
Due to fund restrictions, the team did not fully delineate groundwater contamination. However, the following decision logic was developed by the project team for application in a future groundwater contaminant delineation program. When analysis of a groundwater sample indicates that the concentrations of groundwater contaminants do not exceed groundwater threshold limits (MCLs), no further action will be required. If analysis of a groundwater sample indicates that the concentration of groundwater contaminants does exceed groundwater threshold limits, groundwater will be examined for visual indications of free product. If free product is observed, a discharge notification form will be submitted to state and county regulators. Whether or not free product is observed, field screening methods will be applied to additional groundwater samples to delineate the horizontal and vertical extent of contaminants. Once this information is collected, the team will recommend locations for permanent monitoring wells. Once agreement is reached, wells will be installed and sampled. If groundwater contaminant threshold limits are not exceeded in the monitoring wells, no further action will be needed. If groundwater contaminant threshold limits are exceeded in the wells, a risk assessment will be performed.
"Real time" decision making for the AOC 82 investigation was not based primarily on in-field, real-time analytical methods. Rather, because the USACE contractor is located at MAFB and could mobilize to the site with ease, fast turnaround off-site laboratory methods were deemed to be sufficient for efficient decision-making. Decision logic was designed so that field characterization results could be presented to the project team in periodic "advance data packages" (ADPs) which included a geographic information system (GIS) and spreadsheet representation of results. The ADPs were used during team-wide teleconference updates to guide subsequent field efforts.
To delineate pesticide contamination in soil, the team employed a fixed laboratory-based pesticide microextraction technique that provided field technicians with a 24-hour to 5-day turn around time in place of EPA Method 8081B, a standard pesticide analytical technique that requires a 30-day turn around time. Laboratory costs increased as turnaround time decreased; therefore, the turnaround time varied for each mobilization depending on the needs of the team at that time.
To evaluate the presence of petroleum contamination that may have resulted from potential UST and piping releases, soil was analyzed in the field using an OVA meter to select locations for DPT sampling and analyses per an MAFB Standard Operating Procedure (SOP).
TQRS not prepared
MacDill follows a Basewide Environmental Restoration Work Plan (BERWP), Revision 5 (June 2003) for all RCRA corrective action activities. This plan documents field sampling methods, laboratory analytical methods, and quality assurance/quality control (QA/QC) protocols.
At each scientific management decision point, USACE and Earth Tech staff performed a data verification step before ADPs were released to the rest of the project team for discussion.
As discussed previously, the field team assessed the accuracy of the microextraction method through collaborative sample analysis using EPA SW-846 Method 8081B. Team members determined, through statistical analysis, that the results produced by the microextraction method varied from those produced by Method 8081B by 5 to 10 percent. Team members partially attribute the high correlation between these methods to the attention that was paid to sample support, which primarily involved rigorous homogenization of samples prior to sample splitting. Method agreement could also have been facilitated by the low sorbing potential of chlordane on the quartz sand that constitutes most of the site soils.
Data management was achieved through the use of ADPs, which are GIS-based summaries of data. An FTP site was used to convey data from the field to the rest of the project team for discussion and decision-making.
To update this profile, contact Cheryl T. Johnson at Johnson.Cheryl@epa.gov or (703) 603-9045.