Catfish Creek IA 01-TRK-124

Assessment Comments

Assessment is based on the results of routine water quality monitoring conducted from 2000-04 by IDNR staff of the Upper Mississippi River "Long-Term Resource Monitoring Program (LTRMP) at Bellevue, IA.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses are assessed (monitored) as "fully supported" based on results ambient water quality monitoring conducted from 2000-2004.   Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream reach.   The source of data for this assessment is the results of routine water quality monitoring conducted at station CF00.3M from 2000 through 2004 by IDNR staff of the Upper Mississippi River "Long-Term Resource Monitoring Program (LTRMP) at Bellevue, IA (see http://www.umesc.usgs.gov/data_library/water_quality/water_quality_page.html.  

EXPLANATION:  The assessment of the Class B(WW) uses is based on results of IDNR/LTRMP chemical/physical monitoring at station CF00.3M from January 2000 through September 2004.   Due to budgetary problems, monitoring was not conducted from September 2002 through March 2004.   Samples were collected monthly during all months of the year.   The parameters analyzed included dissolved oxygen, pH, ammonia-nitrogen, total phosphorus, total nitrogen, total suspended solids, and chlorophyll.   A summary of these data show no violations of the Class B(WW) water quality criteria for temperature, pH, or dissolved oxygen 43 samples collected.   One of 43 samples did exceed the Class B(WW) chronic criterion for ammonia nitrogen:  the sample collected on August 25, 2004 contained 0.68 mg/l of ammonia nitrogen.   This level slightly exceeded the temperature/pH-dependent chronic criterion of 0.55 mg/l.   According to U.S.  EPA guidelines for Section 305(b) reporting, if, for a dataset where at least 10 samples have been collected over a three-year period, up to one sample can violate water quality criteria without indicating impairment; however, if more than one sample exceeds the criterion, impairment (“partial support”) is indicated.   If, however, more than 10% of the samples exceed state criteria for toxics (including ammonia-nitrogen), the aquatic life uses are "not supported" (see pg 3-18 of U.S.  EPA 1997b).   Thus, the single violation in the 43 samples collected over the three-year period at Catfish Creek does not indicate impairment of aquatic life uses.  

Fish consumption uses remain "not assessed" due to the lack of monitoring in this stream reach.