Assessment Comments

Assessment is based on results of (1) IDNR/UHL ambient monthly monitoring near St. Joseph from 2002-04, (2) IDNR/UHL biological (biocriteria) sampling in 2002, and (3) U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2002.

Basis for Assessment

[Prior to the 2004 assessment, this segment was referred to as IA 04-EDM-0010_2.   It was broken into two segments, now listed as IA 04-EDM-0010_2 and IA 04-EDM-0010_3 to reflect the location descriptions and classifications as described in the Surface Water Classification.  All previous assessments referring to the original segment (IA 04-EDM-0010_2) can now be found listed in the documentation for segment IA 04-EDM-0010_3.]

SUMMARY:  The Class B(WW) aquatic life uses are assessed (monitored) as "fully supported" based on results of biological monitoring in 2002.   Results of monthly ambient chemical/physical water quality monitoring during the assessment period show good water quality.   Fish consumption uses are assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2002.   The sources of data for this assessment include (1) results from the IDNR ambient monthly monitoring station from 2002 through 2004 near St.  Joseph in Kossuth County (STORET station 10550001), (2) results of IDNR/UHL biological monitoring conducted in 2002 as part of the IDNR/UHL stream biocriteria project, and (3) results of U.S.  EPA/IDNR fish contaminant (RAFT) monitoring near Algona in July 2002.

EXPLANATION:  The Class B(WW) uses are assessed as "fully supported " based on results of IDNR/UHL biological monitoring in 2002.   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 benthic macroinvertebrate taxa and 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) and a benthic macroinvertebrate index (BM-IBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2002 BM-IBI score was 66 (good).  The aquatic life use support was assessed (evaluated) as fully supported (=FS), based on a comparison of the BM-IBI score with biological assessment criteria established for previous Section 305(b) reports.   The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.

None of the approximately 35 samples collected during the 2002-2004 assessment period violated Class B(WW) water quality criteria for pH or ammonia-nitrogen.   None of the approximately 7 samples analyzed for pesticides or the 10 samples analyzed for toxic metals violated state water quality criteria.   One of the 34 samples analyzed for dissolved oxygen, however, violated the Class B(WW) criterion of 5.0 mg/l (this sample contained a dissolved concentration of 3.7 mg/l).   According to U.S.  EPA guidelines (U.S.  EPA 1997b, page 3-17), however, a violation frequency of less than 10 % for conventional parameters such as dissolved oxygen nonetheless suggest "full support" of aquatic life uses.   Thus, the percentages of violations of the dissolved oxygen criterion at this station (3%) does not suggest an impairment of aquatic life uses in this stream segment.  

Fish consumption uses were assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Algona in 2002.   The composite samples of fillets from channel catfish and walleye had low levels of contaminants.   Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.069 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm.   Levels of primary contaminants in the composite sample of walleye fillets were as follows: mercury: 0.154 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm.

The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses.   Prior to 2006, IDNR used action levels published by the U.S Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa.   In an effort to make Iowa’s consumption more compatible with the various protocols used by adjacent states, the Iowa Department of Public Health, in cooperation with Iowa DNR, developed a risk-based advisory protocol.   This protocol went into effect in January 2006 (see http://www.iowadnr.gov/fish/news/consump.html for more information on Iowa’s revised fish consumption advisory protocol).   Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest either a threat to, or impairment of, fish consumption uses.   This scenario, however, does not apply to the fish contaminant data generated from the 2002 RAFT sampling conducted in this assessment segment:  the levels of contaminants do not exceed any of the new (2006) advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.