Assessment Comments

Assessment based on results of (1) IDNR/UHL biological (biocriteria) monitoring in 2002 (BM-IBI= 52 (good)) and (2) IDNR/UHL ambient monthly water quality monitoring near Pisgah from 2000-2002.

Basis for Assessment

[Note:  For the 2002 report, the previous waterbody segment for the Soldier River (IA 06-SOL-0010-0), which extended 35 miles from its mouth to confluence with East Soldier River near Ute in Monona Co., was split into two subsegments:  (1) mouth to confluence with an Jordan Creek near Moorhead (Monona Co.) (IA 06-SOL-0010-1, this one) and (2) Jordan Creek to East Soldier River near Ute, Monona Co.  (IA 06-SOL-0010-2).   See historical assessments from this subsegment for previous Section 305(b) assessments for the original 35-mile river reach.]

SUMMARY:  The Class B(WW) aquatic life uses are assessed (evaluated) as "fully supported / threatened" based on (1) results of ambient chemical/physical water quality monitoring and (2) biological monitoring for fish and aquatic macroinvertebrates.   Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this river segment.   The sources of data used for this assessment include (1) results of IDNR/UHL monthly ambient water quality monitoring conducted during the 2000-2002 assessment period at the County Road F20 bridge west of Pisgah (STORET station 10430002 (formerly station 950032)) and (2) results of IDNR/UHL biological monitoring conducted in 2002 as part of the stream biocriteria project.  

EXPLANATION:  Both types of monitoring conducted in this river segment suggest only a threat to full support of the Class B(WW) aquatic life uses.   Monitoring at the IDNR/UHL ambient water quality monitoring station near Pisgah showed no violations of Class B(WW) water quality criteria during the 2000-2002 assessment period for dissolved oxygen (minimum value = 6.1 mg/l), pH (range = 7.7 to 8.9 units), or ammonia-nitrogen (maximum value = 2.0 mg/l) in the 36 samples analyzed.   (Note:  two dates during the 2000-2002 period had ammonia-nitrogen levels of 2.0 mg/l:  May 6, 2001 and May 2, 2001.   If the corresponding pH values for these samples had not been relatively low (less than 8 units), these ammonia concentrations would have likely violated state standards).   One of the eight samples analyzed for pesticides, however, contained chlorpyrifos above the Class B(WW) chronic criterion:  the sample collected on May 2, 2001 contained 0.05 ug/l and thus exceeded the Class B(WW) chronic criterion of 0.041 ug/l.   According to U.S.  EPA guidelines for Section 305(b) reporting (U.S.  EPA 1997b, page 3-18), results for toxic parameters for least 10 samples collected over a three-year period are needed to develop a "monitored" assessment.   Further, these guidelines allow up to one violation of aquatic life criteria in these 10 samples before "impairment" is suggested.   According to IDNR's methodology for Section 305(b) reporting, the occurrence of this single violation indicates that the Class B(WW) uses should be assessed as "fully supporting / threatened."  Because only eight samples were collected at the Pisgah during the 2000-2002 assessment period, too few data are available for a "monitored" assessment.   Thus, the aquatic life uses are assessed ("evaluated") as "fully supported / threatened" based, in part, on the single violation of the Class B(WW) chronic criterion for chlorpyrifos.  

Results of IDNR/UHL biological monitoring in 2002 also suggest only threats to the full support of the aquatic life uses of this stream.   This assessment was based on data collected in 2002 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 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 Fish IBI score was not available and the BM-IBI score was 52 (good).  The aquatic life use support was assessed (evaluated) as fully supporting/threatened (=FS/T), based on a comparison 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.   The assessment type for this biological assessment is also considered "evaluated" (relatively lower confidence assessment) due to the availability of data for only one (aquatic macroinvertebrates) of the two indicator communities (fish and aquatic macroinvertebrates) typically sampled as part of IDNR/UHL biocriteria monitoring.  

Fish consumption uses remain "not assessed" due to the lack of recent fish contaminant monitoring in this river segment.