Dynamic Workplans and Adaptive Sampling and Analysis Programs 

 

 

 

        The ability to rapidly assess environmental contaminants at purported or existing hazardous waste sites is an essential component of the nation's environmental restoration program. Each site, whether owned by the public or private sector, must be evaluated to determine whether risk to human health or the environment exists. If the data obtained supports the notion that either no risk or an acceptable level of risk exists for the intended land usage, then no further action is required. If, on the other hand, sufficient risk is determined to require a full site characterization, the site investigation effort must delineate the nature, extent, direction, concentration and rate of movement of the contamination. Field analytics can support dynamic investigations when data are produced quickly enough to make next step decisions. This requires that neither sample collectors nor analysts sit idle waiting for one another.

 

 

Dynamic Workplans - Adaptive Sampling and Analysis Strategies

        Successful hazardous waste site investigations should be focused with goals and objectives clearly defined. This does not mean, as has been past practice, that the site investigation process should result in workplans that are "etched in stone."  Figure 1 compares the traditional and dynamic adaptive sampling and analysis programs. The traditional workplan relies on pre-specified sampling locations, pre-specified numbers of samples to be collected, and pre-specified types of analysis. The traditional site investigation is static in its application. It does not provide a framework for changes in direction based on what is learned in the field. Samples are collected, packaged and typically sent off-site for analysis. Because data turnaround times can be long, from several weeks to several months, analytical results are unavailable while the sampling team is still on site to address data "surprises" or concerns. Experience has shown that multiple field investigations within the same or subsequent seasons are required to fill data gaps. Traditional site investigations result in several trips to the field by sample collection and survey teams before the site study can be completed. This same static process is used during hazardous waste site cleanups as well.

 

        In contrast, dynamic workplans rely on an initial conceptual model and an adaptive sampling and analysis strategy, see Figure 1. Rather than dictate the details of the type of sample analysis to be performed and the location and number of samples to be collected, dynamic workplans specify the decision-making logic that will be used in the field to determine which analytes to analyze, where to collect the samples, and when to stop sampling. Adaptive sampling and analysis programs change as the conceptual model for the site is refined based on the results obtained in the field.  

 

        The initial conceptual model contains the best available information at the start of the project. It depicts the three dimensional site profile based on vadose zone and groundwater flow systems that can exert influence on contaminant movement. The conceptual site model is updated as additional data become available during the site investigation or cleanup. The conceptual model is dynamic in nature. It changes as on-site activities proceed and reflects the "new" knowledge gained through field studies.  A successful adaptive sampling and analysis program requires analytical instrumentation and methods that are field-practical and can produce verifiable data fast enough to support the on-site decision making process, see Figures 2-4.  Performance-based measurement systems meet this challenge, see Figures 5-7.   

 

        A videotape of the Hanscom Air Force Base (Bedford, MA) dynamic site investigation project can be found on EPA's web site at http://www.clu-in.org/video/hanscom.htm as well as an EPA case study, which describes the results of the project. Briefly, the Hanscom project involved re-investigation of three sites that were previously studied by the Air Force using the traditional process.  Based on the previous findings, a groundwater collection system and treatment facility was constructed for VOCs.  The optimum operating condition for the influent concentration was 10 ppm. The plant was operating at 0.05 ppm at the time of the Tufts study and had an annual operating cost of $600,000.  We analyzed VOCs and SVOCs in the field by rapid screening and quantitative GC/MS, see ultrafast GC/MS.  Metals were analyzed on-site by ICP/OES.  The total number of samples analyzed during the two week study is shown below.  The EPA conducted a laboratory audit in the field, reviewed the SOP's and MDL studies, and verified all field data.  The Air Force re-designed the groundwater collection system based on the Tufts data, which increased the influent concentration to ~ 8 ppm.

 

               number of samples analyzed                                                 sample analysis time

 

       

        A cost comparison between rapid quantitative GC/MS on-site and off-site laboratory analysis is shown in Figures 8 and 9.  In addition, the dynamic workplan guideline and work performed by others using this approach can be found at http://www.epa.gov/superfund/programs/dfa/dynwork.htm.

 

 

see also: dynamic workplan (PowerPoint presentation) and subsurface detection of organics

 

 

Selected Publications

“Accelerated GC/MS Analyses of Samples from Former Manufactured Gas Plant Sites.” D.M. Mauro, S. Smarason, and A. Robbat, Jr., Electric Petroleum Research Institute, March 2000, TR-114786.  Abstract

 

"Dynamic Workplans and Field Analytics: Metals Assessment by Inductively Coupled Plasma Optical Emission Spectroscopy." R. L. Simpson III, C.L. Bock, and A. Robbat, Jr., Remediation 9(4), 1999, 65-78. Abstract

 

"Fast Gas Chromatography/Mass Spectrometry Analysis in Support of Risk-based Decisions." A. Robbat, Jr., S. Smarason, and Y. Gankin, Field Anal. Chem. Technol. 3(1) 1999 55-66.  Abstract

 

"Dynamic Work Plans and Field Analytics, The Keys to Cost-Effective Hazardous Waste Site Investigations." A. Robbat, Jr., S. Smarason, and Y. Gankin, Field Anal. Chem. Technol. 2(5) 1998 253-265. Abstract

 

"Field Analytics, Dynamic Workplans." The Encyclopedia of Environmental Analysis and Remediation, contributed by A. Robbat, Jr., ed. by R.A. Meyers, John Wiley & Sons, Inc. New York, NY., July 1998, 1674-1687. Abstract

 

"Field Determination of VOCs in Soil and Water by Purge-and-Trap and Thermal Desorption GC/MS." Current Protocols in Field Analytical Chemistry, contributed by Y.V. Gankin, S. Smarason, and A. Robbat, Jr. ed. by V. Lopez-Avila, John Wiley & Sons, New York, 1998, 1B.1.1-1B.1.12.

 

"Field Determination of SVOCs in Soil by Thermal Desorption GC/MS." Current Protocols in Field Analytical Chemistry, ed. by V. Lopez-Avila, contributed by .V. Gankin, S. Smarason, and A. Robbat, Jr., John Wiley & Sons, New York, 1998, 2B.3.1-2B.3.10.

 

"On-site Analysis of Metal Contaminants by ICP-OES.", Current Protocols in Field Analytical Chemistry, contributed by R. Simpson and A. Robbat, ed. by V. Lopez-Avila, John Wiley & Sons, New York, 1998, 3D.2.1-3D.2.16. Abstract

 

"Adaptive Sampling and Analysis Programs for Contaminated Soils." R. Johnson, J. Quinn, L. Durham, G. Williams, and A. Robbat, Jr., Remediation 2 1997 81-96.  Abstract