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Table 6. Metric scores and impairment ratings for Rock Creek 

 based on a comparison of diatom metrics at the 

 downstream study site to metrics at the upstream 

 control site (#1) using Protocol II and Table 12 in 

 Bahls (1993) . Underlined values indicate full support 

 of aquatic life uses, minor impairment, and good 

 biological integrity; all other values indicate 

 full support of aquatic life uses, no impairment, and 

 excellent biological integrity. 



Metric Rock Creek Station 



Shannon Diversity Index 100 117 



Pollution Index 100 106 



Siltation Index 100 62 



Similarity Index 100 51 



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