Ann B. Strong, Chief, Environmental Chemistry Branch

U.S. Army Engineer Waterways Experiment Station

The Methods and Data Comparability Board (MDCB) of the National Water Quality Monitoring Council advocates the promotion of a performance based methods system or measurement system (PBMS) as one of its top priorities in providing a mechanism that will allow data comparability among various monitoring programs and data bases. MDCB originally defined PBMS as a process that permits the use of any appropriate method that demonstrates the ability to meet established criteria and complies with specified data quality needs. In the 6 October 1997 Federal Register, the Environmental Protection Agency (EPA) defines PBMS as "a set of processes wherein the data quality needs, mandates or limitations of a program or project are specified, and serve as criteria for selecting appropriate methods to meet those needs in a cost effective manner." A slightly different definition was presented by Kinney and Caliandro (1998), "PBMS is a set of processes wherein a monitoring program’s DQOs are designated rather than specifying which approved analytical method must be used for monitoring. The analyst uses these DQOs as the criteria for selecting appropriate methods to meet these needs...".

The MDCB feels that initial implementation of PBMS should embrace the following concepts:

To make PBMS a viable system for data comparability, minimum data base information is needed:

Method or measurement performance criteria must be defined to insure that data quality meets project requirements:

Requirements for implementation of PBMS necessitate training- training- training for both data generators and data users as the liability for appropriate data shifts to the site contractor or owner. Training should include the sample collection process and pre-laboratory activities. Additional prerequisites include matrix specific performance evaluation materials, a laboratory accreditation process, and a systematic audit of activities.

Some disadvantages to implementation include:

Implementation within EPA, as the primary regulator requiring environmental monitoring, is proceeding with a proposed streamlining process (USEPA, Mar 98) to reduce the regulatory burden of prescriptive methods required under the Clean Water Act and the Safe Drinking Water Act and applies to both chemical and biological methods. This proposals would allow analysts to use professional judgement to modify and develop alternatives to established EPA methods. The streamlining process is very similar to that originally proposed by the MDCB. EPA later published as notice of intent to implement PBMS for all of its media programs (USEPA, Oct 1997) and developed generic check-lists with program specific requirements (available on the Internet at http://www.epa.gov/pbms) . The requirement that only SW-846 methods be used for RCRA will be eliminated. In anticipation of this shift to a performance based process, update 3 of SW-846 was written in PBMS format with method performance criteria included. An initial and continuing demonstration of method performance are required and must be documented. Implementation of PBMS does not negate the need or use of standard or consensus methods; it only eliminates the mandate that they be used. The Deputy EPA Administrator has issued a requirement that each EPA agency develop a PBMS implementation plan by 30 September 1998. Even with implementation by EPA, individual states may elect to continue to require "approved" methods.

Whether we call PBMS a "methods" system or a "measurement" system, the basic goals are the same—to provide information of known quality that will satisfy user needs. The MDCB endorses the need for reference methods even though some of EPA’s programs propose eliminating this requirement. Incorporation of a full-blown PBMS raises concern with both the data producers and the data users that EPA agencies will submit widely divergent implementation proposals for their various programs. There is also great apprehension that the expertise required by auditors/evaluators will not be available.

Although initial implementation of PBMS is directed to laboratory operations, field methods and pre-laboratory operations must be an integral part of the system if we are to meet our goal of producing comparable monitoring data of known quality that provide the answers we need to make adequate environmental assessments.