Assessment Comments

Assessment is based on results of: (1) IDNR/UHL ambient monthly monitoring NW of Cedar Falls from 2002-04; (2) biological monitoring conducted in 2001 by IDNR Fisheries Bureau: FIBI = 61 (good); and (3) 2003 IDNR/UHL REMAP sampling: FIBI = 45 (fair) and BMIBI = 77 (excellent).

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses are assessed (monitored) as “fully supported” based on results of ambient water quality monitoring, IDNR Fisheries biological monitoring data and IDNR/UHL REMAP data.   Fish consumption uses remained "not assessed" due to the lack of fish contaminant monitoring in this stream segment.   The sources of data for this assessment are (1) the results of IDNR monthly ambient monitoring from January 2002 through December 2004 at the county road T75 bridge approximately 3.5 miles northwest of Cedar Falls (STORET station 10070001), (2) results of biological monitoring conducted in 2001 by the IDNR Fisheries Bureau and (3) results of IDNR/UHL REMAP biological monitoring in 2003.

EXPLANATION:  Results of IDNR ambient water quality monitoring station NW of Cedar Falls during the 2002-2004 assessment period showed no violations of Class B(WW) water quality criteria.   That is, no violations of state water quality criteria for conventional parameters (dissolved oxygen, pH, and ammonia-nitrogen) occurred in the samples collected (51 samples for dissolved oxygen and pH; 39 samples for ammonia-nitrogen) during this monitoring period.   Levels of pesticides were below levels of detection in the samples analyzed during the assessment period (from 7 to 10 samples were analyzed for pesticides).  

This assessment remains partially based on results of biological monitoring conducted in 2001 as part of a DNR Fisheries stream sampling project: Manchester research station and in 2003 by IDNR/UHL as part of the REMAP 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 collected in the stream sampling reach.   The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2001 FIBI score was 61 (good).   The 2003 FIBI score was 45 (fair) and the 2003 BMIBI score was 77 (excellent).   The aquatic life use support was assessed as fully supporting (= FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports.  The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   The non-riffle FIBI BIC for this ecoregion is 44 and the artificial substrate BMIBI BIC for this ecoregion is 52.

Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream reach.