West Fork Cedar River IA 02-WFC-802

Assessment Comments

Assessment based on results of (1) IDNR/UHL biocriteria sampling in 1999 and (2) U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2002.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses are assessed (monitored) as fully supporting / threatened) based on results of IDNR/UHL biological monitoring in 1999.   Fish consumption uses are assessed (monitored) as “fully supported” based on results of U.S.  EPA/IDNR fish contaminant monitoring near Allison in July 2002.  

EXPLANATION:  The assessment of the Class B(WW) aquatic life uses was based on data collected in 1999 as part of the DNR/UHL stream biocriteria project.   A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data.   The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach.   The biological metrics were combined to make a fish community index of biotic integrity (F-IBI) and a benthic macroinvertebrate index (BM-IBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 1999 Fish IBI score was 70 (good) and the BM-IBI score was 54 (fair).   The aquatic life use support was assessed as fully supporting/threatened (=FST), based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established specifically for the 2002 Section 305(b) report.   The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.

Fish consumption uses were assessed as “fully supported” based on results of U.S.  EPA / IDNR fish contaminant (RAFT) monitoring near Allison in 2002.   The composite samples of fillets from channel catfish and smallmouth bass had very low levels of contaminants.   Neither sample contained levels of contaminants that approached even one-half the respective FDA action levels or IDNR levels of concern.   Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.105 ppm; total PCBs: 0.094 ppm; and technical chlordane: 0.045 ppm.   Levels of primary contaminants in the composite sample of smallmouth bass fillets were as follows: mercury: 0.080 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm.