How long are field measurement locations and results valid since it may not be possible to archive samples and locations may not be protected?
The issue of sample archiving and/or preservation of the original support for measurement results can be important in the context of data defensibility. This question capture two distinctly different issues: (1) How does one preserve the original sampled media to allow replicate analyses in the future to validate the original result? (2) How does one ensure the sample remains representative of the decision unit (e.g., barrel, area of contaminated sediment, groundwater point of compliance, etc.) over time? For ex situ sample analyses, (real-time or traditional) preserving sampled media is straightforward. If sample preservation is a requirement for a program for whatever reason, arrangements can be made for sample archiving that insure the long-term integrity of the sample and that controls chain of custody. For measurements that are in situ, or in other words that measure some key parameter directly for environmental media, the issue becomes one of being able to document the exact meas
