Validating existing data in the Environmental Technology Verification Program.
Establishing the credibility of existing data is an ongoing issue, particularly when the data sets are to be used for a secondary purpose, i.e., not the original reason for which they were collected. If the secondary purpose is similar to the primary purpose, the potential user may have little difficulty establishing credibility since the acceptance criteria for both purposes should be similar. If the secondary purpose is different, then data credibility may be more difficult to establish because the experiment generating the data may not have been conducted optimally for the secondary purpose and all of the necessary quality assurance data ("metadata") may not have been collected. In either case, a process will be required to determine the acceptability of the data. For this reason, at the time the U.S. Environmental Protection Agency (EPA) Environmental Technology Verification (ETV) program was established, similar certification and verification programs run by states or foreign countries routinely used existing data sets, for cost reasons, rather than generate new data by testing. The issue of whether existing data could be used in the ETV program immediately surfaced. In response, a policy and a process that addressed existing data were written and published in Appendix C of the ETV Quality and Management Plan (Hayes et al., 1998). This paper discusses how the ETV program determines the credibility of existing data used to verify the performance of environmental technologies.