A-54 
interpolation elements) and vetting by outside experts is needed. Indeed, although 
the CFD approach is beginning to get featured in scientific venues, it has not yet 
been reviewed as part of the scientific literature. The panel sees this as an overdue 
next step for necessary for its acceptance, further development, evaluation, and 
application. 
The panel contrasted the CFD approach with existing state and jurisdictional water 
quality criteria and attainment procedures that are based strictly upon the observed 
sample, where site selection is not based upon probability sampling, inferences are 
not based upon error structure, and monitoring does not involve a scientifically 
rational design. Indeed, standard practice for assessing compliance with water 
quality criteria throughout the US is to sample monthly at a fixed set of stations and 
make judgments about compliance strictly from those samples. Sampling stations 
are typically located for convenience (e.g., bridge overpasses), there is reluctance to 
re-evaluate and change location (so as to maintain a time series at a fixed point), and 
no consideration is given to representativeness of the sample for the space/time not 
sampled. Thus the previous method used by the Chesapeake Bay Program, similar to 
the approaches used in other states, was simply based on EPA assessment guidance 
in which all samples in a given spatial area were compiled and attainment was 
assumed as long as > 10% of the samples did not exceed the standard. In this past 
approach all samples were assumed to be fully representative of the specified space 
and time and were simply combined as if they were random samples from a uniform 
population. This approach was necessary at the time because the technology was not 
available for a more rigorous approach. But it neglected spatial and temporal patterns 
that are known to exist in the standards measures. The CFD approach was designed 
to better characterize those spatial and temporal patterns and weight samples 
according to the amount of space or time that they actually represent. 
6.2 THE CFD APPROACH AND PEER REVIEW 
The panel views the CFD approach as innovative, one that has general application in 
water quality attainment assessments, but scientific acceptance of the approach will 
require that it is subjected to more extensive and targeted peer-review in the scien¬ 
tific literature. Because the CFD is a regulatory tool, it is particularly important that 
the approach is effectively communicated to the scientific community at large, for 
general acceptance but more critically for the sustained research and development 
that the CFD, as a nascent approach, requires. As highlighted elsewhere, bias and 
imprecision that can occur due to small sample densities, non-independence in 
temporal trends, and inadequate spatial interpolations. Such work is novel and 
should elicit interest among biostatisticians as it addresses questions of both funda¬ 
mental and applied consequence. 
Although, continued working groups, involvement through STAC of expert biosta¬ 
tisticians, and related reports such as this one will remain important in scientific 
acceptance of the CFD approach, the panel recommends immediate attention in 
subjecting the CFD to traditional peer review. One or several review papers should 
be submitted by CFD principals that lay out the theory, general approach and lists 
emergent scientific issues to stimulate other scientists to begin to address such 
issues. Several such papers might be appropriate given potential interest by 
appendix a 
The Cumulative Frequency Diagram Method for Determining Water Quality Attainment 
