Hitting a Triple
- By Ratana Kanluen
- Jul 01, 2003
What would you say to an innovation in site investigation methodology that would enable you to generate better site data, reduce the error and variability of your sampling data, and has been proven to reduce site investigation analytical costs by an average of fifty percent? What if you also found out that this method was supported and promoted by both the U.S. Environmental Protection Agency and the U.S. Army Corps of Engineers and its use is being required on more and more federal cleanup contracts? You would probably say "What is it?" and "How soon can I get it?"
This innovation is a new way of looking at site investigations called the Triad Approach. The Triad Approach is a site investigation methodology that relies on the use of field analytical technologies and flexible sampling plans to generate better more accurate site data, with fewer trips to a site, at a lower cost.
A Look at the Record
Over the past 25 years, hundreds of thousands of contaminated sites have been investigated. EPA studied thousands of these projects and learned a number of techniques that have been used to streamline site work and make sampling and analysis more accurate and useful.
The traditional approach to site investigations involves mobilization of crews and equipment to a site, collection of samples in a random grid pattern, sending them off to a traditional fixed laboratory and then demobilizing (or letting expensive equipment sit idle at the site) for the average turnaround time of 14 to 21 days for the data. Once the data is ready, the project manager analyzes and interprets it and, more often than not, he or she uncovers gaps in the data that prevent a full understanding concerning the distribution of contaminants at the site. The project manager is then forced with the choice of making remedial decisions with incomplete data -- which can lead to very costly mistakes -- or re-mobilizing to the site to collect additional samples and wait a few more weeks. This pattern of re-mobilization and re-sampling may be repeated a number of times until the data generated meet the specifications for the project. This process is inefficient and wastes time and money.
By using field analytical tools during the sampling project, analytical data is available immediately in the field and adjustments to the sampling plan can be made to collect additional samples or different types of samples to fill in the gaps in data as they are uncovered.
On the other hand, EPA uncovered a number of projects that did not follow this pattern. These projects were completed in less time, with fewer mobilizations and at significantly lower costs. A common denominator of these more efficient projects was the use of field analytical tools and a flexible field sampling plan created by a multidisciplinary team of experts. In this model, the experts first determine what data will be needed to make appropriate remedial decisions about the site. Using the achievement of this data set as their goal, they develop their sampling plan which will include the use of field analytical tools. By using field analytical tools during the sampling project, analytical data is available immediately in the field -- while the sampling team is still at the site -- and adjustments to the sampling plan can be made to collect additional samples or different types of samples to fill in the gaps in data as they are uncovered. This eliminates return trips to the site while providing better quality data. Furthermore, field analytical technologies are generally less expensive than laboratory analysis. The single site mobilization combined with a lower analytical bill significantly reduces the cost of site investigations.
These three steps -- upfront planning by a multidisciplinary team of experts, flexible sampling plans, and the use of real-time measurements in the form of field analytical tools -- form the basis of the Triad Approach. The overarching goal of the program is to identify and manage those uncertainties that could cause errors during characterization or remediation. The Triad Approach recognizes that too much emphasis has been placed on laboratory analytical methods and far too little attention has been given to the uncertainty, inefficiency and costs introduced by many other important aspects of traditional sample collection and analysis, such as sampling technique, sample preservation, laboratory subsampling and sample extraction, digestion and preparatory work.
Traditional sampling plans also fail to adequately ensure that the samples collected are representative of the actual conditions at the site. This is a particularly acute problem when dealing with sites with heterogeneous contaminant distribution (organic explosives, for example, are particularly problematic in this respect). Studies have shown that far more uncertainty and error in site investigation data sets can be attributed to sampling uncertainty than to analytical precision (i.e., more of the uncertainty and error can be reduced through innovations and improvements in the way data and samples are collected and analyzed than can be gained through the use of greater precision in laboratory analytical techniques). By using field analytical techniques and the real-time data they produce to make better sampling decisions in the field - decisions that reduce the error and uncertainty in the sampling data set - the overall quality of the site sampling data can be greatly improved. This approach also offers the added benefit of significantly reduced costs.
There are many types of field-analytical technologies that can be used to generate data under a Triad Approach project. These technologies include x-ray fluorescence (XRF), photoionization detectors (PID), flame ionization detectors (FID), organic vapor analyzers (OVA) and onsite gas chromatograph/mass spectrometer (GC/MS) units, but none are being used as frequently and gaining as wide acceptance as immunoassay.
The Power of Immunoassay
Immunoassay technology uses an antibody directed against the contaminant as the method of detection of the compound. Antibodies are very specific for the compounds that they will recognize and to which they will bind. Immunoassay uses this principle to develop a very accurate analytical detection technology.
The immunoassay analytical system that people outside of the environmental industry are most familiar with is home pregnancy tests. Home pregnancy tests are immunoassay tests that rely on an antibody that recognizes a pregnancy hormone. The binding of the antibody to the hormone is detected by a strip that turns color.
Environmental immunoassays work on the same principle, but the method of detecting whether the antibody has detected the target compound varies. Some are strip assays, while most environmental immunoassays are tests that are developed in a reaction tube or well plate and the reaction causes a color change that is either detected visually or by a very sensitive spectrophotometer.
Immunoassay technology offers analytical selectivity, sensitivity, portability, and rapid turnaround time. Immunoassay kits can be tailored to target specific analytes or classes of analytes, depending upon the needs of the project. They also have the capability of detecting target analytes at very low levels, as low as parts per trillion levels for some analytes, which are needed in many environmental applications.
Immunoassays are available for a wide range of common environmental contaminants including organic explosives (e.g. TNT, RDX), hydrocarbons and petroleum compounds e.g., benzene, toluene, ethyl benzene and xylene (BTEX), total peteroleum hydrocarbon (TPH), etc, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dioxins, contaminants from biological sources (microcystins, pathogens, etc) and many common pesticides (atrazine, DDT, metolachlor and many others).
In one well publicized project, known as the Wenatchee Tree Fruit Test Plot site, investigation of a site contaminated with organochlorine pesticides showed the potential of the Triad Approach. According to the EPA report on the project, the approach, which included the use of immunoassay analysis for DDT and cyclodienes in the field, permitted rapid characterization, excavation and segregation of soil. Characterization and cleanup at the site were accomplished with a single four-month field mobilization, and the entire project cost was reduced to $589,000 from an estimated $1,200,000 using a traditional site characterization approach. This project is an excellent example of the power of the Triad Approach and the reader is strongly encouraged to read this report.
These three steps - upfront planning by a multidisciplinary team of experts, flexible sampling plans, and the use of real-time measurements in the form of field analytical tools - form the basis of the Triad Approach.
In another more recent project, S2C2 Inc., a New Jersey-based environmental services company that specializes in the implementation of the Triad Approach, recently completed a brownfield investigation at a site in Trenton, N.J. Prior to field mobilization a thorough initial assessment of the site was performed. This assessment included a complete historical review, the locating and sampling of potential areas of concern, and laboratory analysis to confirm site specific compounds of concern. Through this process the appropriate analyte list and field analytical techniques were selected.
One of the primary contaminants identified was PCBs, which is a group of toxic, persistent chemicals formerly used in electrical transformers and capacitors for insulating purposes. Because the PCB distribution on the large (greater than 20 acre) site was random, a large number of samples would need to be collected for a complete characterization of the site. Immunoassay technology was selected for the analysis to allow for in-field decision-making to conduct the characterization program in the most efficient and cost effective manner possible.
During a period of approximately seven days, over 200 soil samples were collected and analyzed using RapidAssay® immunoassay PCB test kits. A percentage of these samples were sent off site for laboratory analysis to serve as collaborative data (the correlation of the laboratory data with the data generated on-site was very high). As the data was generated and analyzed in the field, subsequent sample locations were selected for analysis. This iterative process was continued until a clear understanding of the distribution of the PCBs was developed.
As a direct result of the ability to rapidly obtain accurate data in the field, the site delineation process was conducted in a fraction of the time that would have been needed using conventional off-site laboratory analysis and long turnaround times. This time savings produced significant savings in labor and mobilization costs.
Correcting Old Myths
If field analytical technologies are this useful, if they can save time, money and increase the accuracy of the data generated at a site, is there a reason that they are not more widely used? The answer to that question can be found in the many myths that surround the use of field analysis.
First, many believe that EPA allows the use of field analysis for screening purposes only and that for real sample analysis (i.e., the data that will be submitted to regulators for approval and site closure) the use of fixed laboratory data is required. This is not the case.
In some programs, for example many water and wastewater programs, EPA prescribes the analytical technique that must be used for regulatory reporting. For EPA site investigation and cleanup programs, however, this is not the case. These programs operate on what is known as the Performance-Based Measurement System (PBMS). PBMS philosophy specifies what needs to be measured but does not specifically require any particular analytical method to make that measurement. This means that any analytical method may be used, so long as that method has been demonstrated to accurately measure the contaminant or parameter of concern in the matrix being investigated (i.e., soil, water) at the detection level needed for the decisions being made about the site. Considering that many immunoassay test systems have been validated by EPA under SW-846 EPA Resource Conservation Recovery Act (RCRA) Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, immunoassay has clearly been shown to meet this standard and can be used for final reporting to regulatory agencies.
Immunoassay technology uses an antibody directed against the contaminant as the method of detection of the compound.
Another reason cited for avoiding the use of field analysis is legal liability. Specifically, project managers want to know that if they are ever called into court they have data they can rely on to be admissible; and many believe that this means they must use a laboratory.
Yet, the standards for data admissibility in federal and state courts do not distinguish between analysis done in a laboratory and that done in the field. Numerous court cases have set precedence that in order for data to be accepted as evidence the analytical technique used needs to be generally recognized in the scientific community and must be shown to be, in the words in one famous U.S. Supreme Court case Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579 (1993) , "relevant and reliable." No distinction is made between data developed in the laboratory and data developed in the field. A variety of factors, including the training and experience of the personnel performing the analysis and the accuracy and reliability of the test method used, determine the weight given to the evidence by the court, but these rules are no different for field or laboratory-based analytical technologies.
There have been many successful applications of the Triad Approach and, as more people learn about the benefits it offers, there are sure to be many more. For environmental consultants keenly aware of the competitive requirements of their business, an education in the principles and application of the Triad Approach is a must. As the Triad Approach becomes incorporated into more and more projects and rightly becomes the standard of the industry, it offers a new level of efficiency and sophistication for all of us who practice the art and science of environmental remediation.
This article originally appeared in the June 2003 issue of Environmental Protection, Vol. 14, No. 5.
This article originally appeared in the 07/01/2003 issue of Environmental Protection.