Mill Creek IA 06-LSR-1615

Assessment Comments

Assessment is based on results of the IDNR stream use assessment in October 1994, combined with DNR fishery survey in June 1989, both conducted in O'Brien county.

Basis for Assessment

Continued to use the assessment of support of the Class B(LR) aquatic life uses developed for the 1996 report (=FST).   Results of the 1989 DNR survey show that nearly all the expected fish taxa (8 of 9) for streams in the NW Iowa Loess Prairies (47a) subecoregion were present.   Although this suggests full support of the Class B(LR) uses, these data are nearly 10 years old; thus, continue to use the 1996 assessment.   Additional monitoring is needed to update this assessment.  

For the 2000 report:  SUMMARY:  The Class B(LR) aquatic life uses were assessed as "fully supported / threatened."  EXPLANATION:  The primary basis for the previous assessment of the Class B(LR) uses was the DNR fish survey from June 1989.   Results from this survey are now too old (greater than five years) for developing an assessment of current water quality conditions.   The current assessment is based on results on a 1998 DNR/UHL biocriteria sampling of fish and benthic macroinvertebrates.   Based on a comparison to results of ecoregion reference site sampling, the fish community was rated fair (Fish IBI=43), and the macroinvertebrate community was rated good (MB IBI=75),  These results suggest that the aquatic life uses are "fully supported / threatened."  

For the 2002 report:  SUMMARY:  The Class B(LR) aquatic life uses remain assessed as "fully supported / threatened" (minor impacts).   EXPLANATION:  The aquatic life uses remain assessed as "fully supported / threatened" based on results of the IDNR/UHL biocriteria monitoring conducted on this stream segment in 1998 (see assessment for the 2000 report above).   These data are less than five years old and, according to IDNR's methodology for Section 305(b) assessments, are thus appropriate for characterizing current water quality conditions.