Assessment Comments
Assessment remains based on results of (1) IDNR/UHL biological (REMAP) sampling in 2002 and 2005 and (2) U.S. EPA/IDNR fish tissue (RAFT) monitoring in 2000.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses remain “not assessed” due to the lack of monitoring data upon which to base an assessment. The Class B(WW1) aquatic life uses remain assessed (evaluated) as “partially supported” based on results of IDNR/UHL biological (REMAP) monitoring in 2002 and 2005. Fish consumption uses remain assessed (evaluated) as "fully supported" based on results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2000. Because the fish contaminant data upon which this assessment is based are now older than five years, the assessment category is changed from a “monitored” (i.e., a higher confidence assessment) to “evaluated” (i.e., lower confidence assessment).
Note: This waterbody was mistakenly placed in Category 3b of Iowa's 2008 Integrated Report. Due to the assessment of fish consumption uses as "fully supported," however, this waterbody should have been placed in Category 2b of the 2008 IR.
EXPLANATION: Routine water quality monitoring is not conducted in this river segment; thus, data upon which to base assessments of the Class A1 uses are not available.
The Class B(WW1) aquatic life uses remain assessed (evaluated) as “partially supported” based on results of IDNR/UHL biological (REMAP) monitoring in 2002 and 2005. 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 (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2002 FIBI score was 33 (fair) and the 2005 FIBI scores were 36 (fair) and 45 (fair). The 2002 BMIBI score was 39 (fair) and the 2005 BMIBI scores were 20 (poor) and 16 (poor). The aquatic life uses were assessed (evaluated) as partially supported (=PS), based on a comparison of the FIBI score with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004. The non-riffle habitat FIBI BIC for this ecoregion is 32 and the BMIBI BIC is 62. This segment passed the FIBI BIC 3/3 times and passed the BMIBI BIC 0/3 times in the last seven years. This assessment is considered evaluated because the drainage area (2210-2236 mi2) above the sampling sites was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria. Even though this site passed the FIBI BIC and failed to meet the BMIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it doesn’t fall in the calibrated watershed size. Several game fish species and species considered sensitive to stream degradation were present in the fish survey.
This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology. IDNR now requires a segment have two or more biological samples collected from the segment in multiple years between 2004 and 2008 to be considered “monitored”. This segment had multiple samples collected in the previous 10 years (1999-2008); however, the multiple samples collected during 2004-2008 were not collected in multiple years. According to IDNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). IDNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation).
Fish consumption uses were assessed (evaluated) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Adel in 2000. The composite samples of fillets from channel catfish had low levels of contaminants. 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. The fish contaminant data generated from the 2000 RAFT sampling conducted in this segment of the North Raccoon River shows that the levels of contaminants do not exceed any of Iowa’s advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.
