Assessment Comments

Assessment based on results of (1) IDNR/UHL biological (biocriteria) monitoring in 2000 and 2002 and (2) IDNR/UHL ambient monthly water quality monitoring near Pisgah from 2002-2004.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses are assessed (monitored) as "fully supported” based on (1) results of ambient chemical/physical water quality monitoring from 2002-2004 and (2) results of biological monitoring for fish and aquatic macroinvertebrates in 2000 and 2002.   Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this river segment.   The sources of data used for this assessment include (1) results of IDNR/UHL monthly ambient chemical/physical water quality monitoring conducted during the 2002-2004 assessment period at the County Road F20 bridge west of Pisgah (STORET station 10430002 (formerly station 950032)) and (2) results of IDNR/UHL biological monitoring conducted in 2000 and 2002 as part of the stream biocriteria project.  

EXPLANATION:  Both types of monitoring conducted in this river segment suggest “full support” of the Class B(WW) aquatic life uses.   Monitoring at the IDNR/UHL ambient water quality monitoring station near Pisgah showed no violations of Class B(WW) water quality criteria during the 2002-2004 assessment period for dissolved oxygen (minimum value = 7.1 mg/l), pH (range = 7.9 to 8.5 units), or ammonia-nitrogen (maximum value = 0.78 mg/l) in the 36 samples analyzed.   In addition, levels of toxic metals in the ten samples analyzed, and levels of pesticides in the seven samples analyzed, were all below Class B(WW) chronic criteria.   These results suggest "full support" of the Class B(WW) aquatic life uses.   During the previous (2004) assessment cycle, one of the eight samples analyzed for pesticides contained chlorpyrifos above the Class B(WW) chronic criterion:  the sample collected on May 2, 2001 contained 0.05 ug/l and thus exceeded the Class B(WW) chronic criterion of 0.041 ug/l.   None of the 11 samples analyzed for chlorpyrifos during the 2002-04 assessment period, however, contained a detectable level of this pesticide.  

Results of IDNR/UHL biological monitoring in 2000/2002 also suggest “full support” of the aquatic life uses of this stream.   This assessment was based on data collected in 2000/2002 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 2002 BMIBI score was 51 (fair) and the 2000 FIBI score was 39 (fair).   The aquatic life use support was assessed (evaluated) as fully supporting”, 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 31 and the BMIBI BIC for this ecoregion is 54.   This segment is considered FS because the FIBI score was greater than the FIBI BIC and the BMIBI score plus the UAV (8) was greater than the BMIBI BIC.

Fish consumption uses remain "not assessed" due to the lack of recent fish contaminant monitoring in this river segment.