Assessment Comments

Assessment is based on results of (1) IDNR/UHL monthly ambient monitoring south of Garber from 2000-02; (2) LTRMP (USGS) ambient monitoring near the mouth, (3) U.S. EPA/IDNR fish tissue (RAFT) monitoring in 2000, and (4) 2002 IDNR Fisheries data: Fish IBI = 39 (fair).

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses are assessed (monitored) as "fully supported/threatened" based on results of IDNR/UHL ambient water quality monitoring from 2000-02.   Fish consumption uses remain assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2000.   Sources of data for this assessment include (1) results monthly monitoring from January 2000 through December 2002 at the IDNR ambient station (STORET station 10220001) located at the County Road C43 bridge south of Garber approximately 1 mile downstream from confluence with the Volga River, (2) results of routine water quality monitoring conducted at station TK04.8M from 2000 through 2002 by IDNR staff of the Upper Mississippi River "Long-Term Resource Monitoring Program (LTRMP) at Bellevue, IA, (3) results of U.S.  EPA/IDNR fish tissue (RAFT) monitoring in 2000 near Garber, and (4) 2002 IDNR Fisheries sampling results.  

EXPLANATION:  The Class B(WW) aquatic life uses were assessed as "fully supported/threatened" based on results of monthly monitoring from the IDNR ambient station south of Garber and from the LTRMP station near the mouth of the river combined with the results of the 2002 IDNR Fisheries sampling results (see below).   Monitoring at these stations showed no violations of Class B(WW) water quality criteria for conventional pollutants or ammonia in the 36 samples analyzed at each station.   In addition, none of the 10 sampled analyzed for common pesticides at the IDNR/UHL station violated their respective Class B(WW) criteria.  

The assessment was partially based on data collected in 2002 as part of a DNR Fisheries stream sampling project: Manchester research station.   A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the Fisheries sampling data.   The biological metrics are based on the numbers and types of 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).   The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2002 evaluated Fish IBI was 39 (fair).   The aquatic life use support was assessed (evaluated) as Partially Supporting (=PS), based on a comparison of the F-IBI score with biological assessment criteria established for previous Section 305(b) reports.   The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.    However, this site was a larger river and was sampled by a boat shocker.    Because the biological assessment criteria were calibrated for wadeable streams, it was decided to downgrade the aquatic life use support assessment as "fully supported/threatened" based on the data above.   More sampling needs to be conducted in the future to determine the severity of impairment.   In addition, more calibration needs to be completed on the biological assessment criteria for larger rivers.

Fish consumption uses remain assessed (monitored) as "fully supported" based on the 2000 EPA/IDNR fish tissue (RAFT) sampling near Garber.   The composite samples of fillets from channel catfish and smallmouth bass collected in 2000 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:  chlordane: < 0.03 ppm; dieldrin:  0.0094; total PCBs:  0.195 ppm; mercury:  0.034 ppm.   Levels of primary contaminants in the composite sample of smallmouth bass fillets were as follows:  chlordane: < 0.03 ppm; total PCBs:  <0.10 ppm; mercury:  0.084 ppm.