Assessment Comments

Assessment based on results of (1) IDNR/UHL biological monitoring in 2001: FIBI = 68 (good), BMIBI = 54 (good) and (2) IDNR/UHL water quality monitoring conducted in 2001 as part of TMDL development.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses are assessed (monitored) as “fully supporting” based on results of biological monitoring in 2001.   Fish consumption uses were "not assessed" due to the lack of fish contaminant monitoring in this stream reach.   The sources of data for this assessment include the results of (1) IDNR/UHL monthly monitoring conducted from March to November 2001, near the mouth of Buffalo Creek at Anamosa (Site 11; STORET station 11530001) in support of TMDL development for this stream reach and (2) IDNR/UHL biological monitoring in August 2001 conducted as part of the stream biocriteria project.  

EXPLANATION:  The Class B(WW) aquatic life uses were assessed as "fully supported" due to the lack of violations of state water quality criteria for pH, dissolved oxygen, and ammonia-nitrogen in the nine samples collected from the TMDL monitoring station during 2001.   These samples were not analyzed for toxic metals or toxic organic compounds.   The available data do, however suggest good water quality, including relatively low levels of ammonia-nitrogen.   No fish kills were reported for this segment of Buffalo Creek in 2000, 2001, or 2002.  

Biological assessment data were collected in 2001 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 (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 68 (good) and the BMIBI score was 54 (good).  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 FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51.

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