Assessment Comments
Assessment is based on results of IDNR/UHL biological (biocriteria) monitoring in 2000: Fish IBI= 5(poor).
Basis for Assessment
SUMMARY: The Class B(LR) aquatic life uses are assessed (monitored) as "partially supported" based on results of IDNR/UHL biological (biocriteria) sampling in 2000. Except for a change in the assessment category ("monitored" vs. "evaluated"), this is the same assessment as that developed for the 2002 reporting cycle.
EXPLANATION: The assessment was based on data collected in 2000 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 fish species that were collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (F-IBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2000 Fish IBI score was 5 (poor). The aquatic life use support was assessed as partially supporting (=PS), based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established specifically for the 2002 Section 305(b) report. The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.
NOTE: The IDNR assessment methodology for biological data was changed in Fall 2005 during U.S. EPA's review of Iowa's 2004 Section 303(d) list such that only one of the two IBI scores for target groups (fish and aquatic macroinvertebrates) is now needed for a "monitored" assessment. Previously, the IDNR methodology required that IBI values for both target groups be present in order for an assessment to be considered "monitored" (of higher confidence); if only one of the two IBIs was available, the assessment was considered "evaluated" and of lower confidence. Based on this revision in methodology, the assessment type for this assessment was changed to "monitored." Thus, the F-IBI score of 5 (poor) from monitoring in 2000 indicates impairment that is now appropriate for addition to Iowa's 2004 Section 303(d) list, and this waterbody was moved from IR Category 3b to 5b.
