Wolf Creek IA 02-CED-530

Assessment Comments

Assessment is based on results of (1) IDNR/UHL ambient monthly monitoring near LaPorte City from 2002-04; (2) USGS NAWQA fish contamiant monitoring in 1995 and (3) 2004 IDNR/UHL REMAP sampling: FIBI = 45 (fair), BMIBI = 50 (fair). Non-riffle site FIBI BIC = 44; artificial substrate BMIBI BIC = 52.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses were assessed (monitored) as "fully supported" based on results of ambient water quality monitoring conducted from 2002 through 2004 and IDNR/UHL REMAP sampling conducted in 2004.   Fish consumption uses remain assessed (evaluated) as fully supporting based on results of fish contaminant monitoring in 1995.   The primary sources of data for this are (1) the results of DNR monthly ambient water quality monitoring conducted on Wolf Creek near LaPorte City (STORET station 10070002) during the 2002-2004 assessment period; (2) results of fish contaminant monitoring conducted in 1995 as part of the U.S.  Geological Survey’s National Water Quality Assessment Program (NAWQA) and (3) IDNR/UHL REMAP biological sampling conducted near LaPorte City.  

EXPLANATION:  The assessment was based on data collected in 2004 as part of the DNR/UHL stream 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 2004 FIBI score was 45 (fair) and the BMIBI score was 50 (fair).   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 site FIBI BIC for this ecoregion is 44 and the artificial substrate BMIBI BIC for this ecoregion is 52.

Additionally, results from DNR ambient monthly monitoring at the La Porte City station show no violations of Class B(WW) water quality criteria in the approximately 45 samples analyzed for conventional parameters (e.g., dissolved oxygen, pH, and ammonia-nitrogen), or in the 10 samples analyzed for pesticides during the 2002-2004 assessment period.   (See assessments developed for the 2000, 2002, and 2004 reporting cycles for a description of previous detections of the pesticides chlorpyrifos and dieldrin in this stream segment).  

Fish consumption uses remain assessed (evaluated) as “fully supported” based on results of USGS fish contaminant monitoring in 1995 conducted as part of the NAWQA program (see assessment for the 2000 report).   However, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is changed from "monitored" (indicating an assessment with relatively high confidence) to "evaluated" (indicating an assessment with relatively lower confidence).