Wolf Creek IA 02-CED-530

Assessment Comments

Assessment is based on results of (1) IDNR/UHL ambient monthly monitoring near LaPorte City from 2000-02 and (2) USGS NAWQA fish contamiant monitoring in 1995.

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.   Fish consumption uses are 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 2000-2002 assessment period and (2) results of fish contaminant monitoring conducted in 1995 as part of the U.S.  Geological Survey’s National Water Quality Assessment Program (NAWQA).  

EXPLANATION:  Results from DNR ambient monthly monitoring at the LaPorte City station show no violations of Class B(WW) water quality criteria in the 39 samples analyzed for conventional parameters (e.g., dissolved oxygen, pH, and ammonia-nitrogen), or in the 10 samples analyzed for pesticides.   For the 2000 reporting cycle, the Class B(WW) uses were assessed as "partially supported" based on results of monitoring conducted on Wolf Creek near Dysart from March 1996 to September 1998 by USGS as part of the National Water Quality Assessment Program (NAWQA).   Although this USGS monitoring showed no violations of Class B(WW) water quality criteria for pH, dissolved oxygen, or ammonia-nitrogen in the 54 samples collected, and showed only a single violation of the Class B(WW) chronic water quality criterion for chlorpyrifos in the 52 samples analyzed, three of 52 samples collected for this program contained violations of the Class B(WW) chronic water quality criterion for dieldrin (see assessment for the 2000 report).   The more recent IDNR monitoring, however, did not detect levels of dieldrin in the 6 samples analyzed during the 2000-2001 assessment period.   Thus, for the 2002 reporting cycle, the assessment of support of the Class B(WW) uses was revised from "partially supporting" to "fully supporting.”  Based on the lack of detectable levels of dieldrin in the four additional samples analyzed during 2002 (total of 10 samples for the 2000-02 assessment period), this assessment remains valid for the 2004 reporting cycle.  

Fish consumption uses are  assessed 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).