The relaxation of both the sample size and the standard deviation criteria (Scenario D) 
increases the number of segment-periods classified as “healthy” from 10 to 16. However, 4 
of these additional CFD curves extend into “degraded” CFD space to a degree that calls into 
question the accuracy of their classification as healthy (Figure A-3). 
space 
Figure A-2. Scenario C - illustrates the impact from relaxing the sample size criterion from n 
> 10 to n > 8 while maintaining the standard deviation criterion of S.D. < 1.0. 
Relaxing the screening criteria for defining healthy segments based on the B-IB1 with respect 
to minimum sample size and maximum standard deviation increases the number of healthy 
segments that can be used to generate the biologically-based reference curve. However, the 
increased uncertainty of accurate classification resulting from relaxation of the criteria far 
outweighs the potential benefit of increased sample size. For the reference CIMS dataset, the 
EPA recommended methodology results in a total sample size of 24 segment-periods, of 
which 10 are classified as healthy and 14 are classified as degraded. Accounting for the trade 
offs with segment classification risks, this present method is supported as sufficient in 
generating a low risk sample size for elucidating the boundary between acceptable (i.e. those 
which allow a healthy benthic community to persist) and unacceptable violations of the deep¬ 
water DO criteria. 
44 
