East Nishnabotna River IA 05-NSH-1816

Assessment Comments

Assessment is based on results of fish tissue (RAFT) monitoring in 1999 near Red Oak.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses were considered "not assessed."  Fish consumption uses were assessed as "fully supporting / threatened."  EXPLANATION:  Due to the lack of data from either chemical or biological monitoring for this river reach, the assessment of support of the Class B(WW) uses was changed from "fully supporting / threatened" to "not assessed."  Fish consumption uses were assessed as "fully supporting / threatened" based on results from EPA/DNR fish tissue (RAFT) monitoring in 1999 near Red Oak that showed the level of technical chlordane in the composite sample of channel catfish fillets (0.18 ppm) exceeded ½ of the FDA action level of 0.30 ppm.   Based on DNR's assessment methodology, a contaminant level above ½ of the respective FDA action level suggests that fish consumption uses should be assessed as "fully supported/threatened."  Levels of other contaminants in the sample of channel catfish, and levels of all contaminants in the composite sample of fillets from freshwater drum, were below ½ of the respective FDA action levels and DNR levels of concern.   Follow-up monitoring will be conducted in this river reach to better determine trends in the levels of chlordane in the bottom-feeding fish of this river reach.