Wolf Creek IA 02-CED-530

Assessment Comments

Assessment is based on results of IDNR ambient monthly monitoring near LaPorte City.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses were assessed as "fully supported."  Fish consumption uses were not assessed.   The primary sources of data for this is the results of DNR monthly ambient water quality monitoring conducted on Wolf Creek near LaPorte City during the 2000-2001 biennial period.   EXPLANATION:  Results from DNR ambient monthly monitoring at the LaPorte City station show no violations of Class B(WW) water quality criteria in the 24 samples analyzed for conventional parameters (e.g., dissolved oxygen, pH, and ammonia-nitrogen), in the 4 samples analyzed for toxic metals, or in the six 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 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 above).   The more recent IDNR monitoring, however, did not detect levels of dieldrin in the six samples analyzed during the 2000-2001 biennial period.   Thus, the assessment of support of the Class B(WW) uses was revised from "partially supporting" to "fully supporting."  Fish consumption uses were not assessed due to the lack of recent fish tissue monitoring in this stream segment.   The assessment of fish consumption used developed for the 2000 reporting cycle (fully supported) was based on results of USGS/NAWQA fish tissue monitoring in September 1995 (see assessment for the 2000 report above).   These data are now considered too old (greater than five years) for accurately characterizing current water quality conditions.