Executive Summary

With the evolution of different water quality monitoring and analysis methods among organizations, even within a single agency, there have been significant consequences in terms of our ability to assess the quality of our nation's waters. In ambient water quality monitoring, many programs have used prescriptive methods without documenting associated method performance or data quality. This has resulted in unknown or poor quality data and uncertainty in the comparability of data collected across programs or organizations (ITFM 1995a). Consequently, monitoring groups outside the agency collecting the data do not know which information can be used with confidence, resulting in limited data sharing across organizations. This is a significant problem because: (a) assessments of aquatic resources on broad geographic scales (basins for example) or from state to state are not easily feasible and (b) opportunities for increased resource efficiency or for minimizing duplication of efforts are missed. Many organizations have recognized the limitations of a prescriptive methods approach and after much deliberation, the Interagency Task Force on Monitoring Water Quality (ITFM) recommended that a performance-based approach be used to address these limitations (ITFM 1995b).

The reliance on prescriptive methods, without appropriate method performance documentation, has also had significant consequences in compliance water quality monitoring. Due to current bureaucratic and administrative constraints, it is time consuming, resource intensive, and cumbersome to modify existing methods or add new improved methods to the Federal Register. The result is that more sensitive, less expensive, faster, or more modern methods, developed either by federal agencies or consensus organizations, have not been easily implemented or encouraged in compliance or ambient monitoring.

Consistent with one of the goals of the Clean Water Action Plan (USEPA 1998), the National Methods and Data Comparability Board (MDCB) under the National Water Quality Monitoring Council (NWQMC) endorses development of a performance based system as one of its top priorities. A performance-based system will provide a mechanism to: (a) enhance data comparability among various monitoring programs and databases to provide data of known quality, and (b) encourage the implementation of better or more cost-effective methods. A performance-based approach permits the use of any scientifically appropriate method that demonstrates the ability to meet established method performance criteria (e.g., accuracy, sensitivity, bias, precision) and complies with specified data quality needs or requirements. Key aspects of the MDCB endorsement of performance-based system include; a) the need to establish concise measurement quality objectives (MQOs) or data quality objectives (DQOs) for each parameter reported; b) the need for demonstrated methods capable of meeting these MQOs or DQOs or regulatory limits; c) the need for adequate reference materials to assist laboratories in demonstrating the appropriateness of a given method (prescriptive or performance-based); d) the need for laboratories to adequately document method performance, and e) the successful completion of a pilot program to demonstrate the advantages and viability of a performance-based approach. In addition, several implementation issues need to be resolved such as real or perceived liability and confidentiality of patented methods or intellectual property. The MDCB recognizes that several types of performance-based systems have been proposed or used by different programs and that there is a need to develop a unified national approach. The MDCB endorses the need for validated methods and concise, achievable performance criteria. The MDCB also recognizes that there are outstanding issues concerning how such an approach would be implemented in compliance or ambient water quality monitoring. The training requirements to implement a performance-based system, and to reach some level of national comparability, are extensive due to the diversity of water quality monitoring programs and data requirements. The MDCB recognizes that adequate training and education of data generators, auditors, and users is central to the successful implementation of a performance-based system, particularly in compliance monitoring programs. The EPA Office of Water PBMS Implementation Plan, which uses reference methods and stated performance criteria, is recognized as an important step towards implementing PBMS. The MDCB and the National Council should act as the focal point for harmonizing existing or proposed performance-based systems so that a sound, unified approach can be achieved and implemented in an intelligent, fair manner on an inter-organizational basis.

Click below for the full PBMS paper:
Performance Based Methods System (PBMS) Paper

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