Wapsipinicon River IA 01-WPS-350

Assessment Comments

Assessment remains based on results of (1) 2004 and 2010 IDNR/SHL biological sampling, (2) ISU statewide survey of freshwater mussels in 1998-99 and (3) results of IDNR mussel surveys in 2012, and (4) EPA/IDNR fish contaminant monitoring in 2003.

Basis for Assessment

[Note:  Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(WW) aquatic life uses, including fish consumption uses.   Due to changes in Iowa’s surface water classification that were approved by U.S.  EPA in February 2008, and due to completion and approval of a use attainability analysis, this segment is also now designated for Class A1 (primary contact recreation) uses.   This segment remains designated for warmwater aquatic life use (now termed Class B(WW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption uses).]

SUMMARY:  The Class A1 (primary contact recreation) uses remain "not assessed" (IR 3a) due to the lack of information upon which to base an assessment.   The Class B(WW1) aquatic life uses remain assessed as “fully supporting” (IR 2a) based on results of biological sampling 2004 and 2010.   The previous impairment of the freshwater mussel community of this segment was de-listed for the 2012 IR cycle based on results of new (2012) mussel surveys.   Fish consumption uses remain assessed (evaluated) as “fully supported” based on results of fish contaminant monitoring in 2003 conducted as part of the U.S.  EPA/IDNR (RAFT) fish tissue monitoring program.   Sources of data for this assessment include (1) results of IDNR/SHL biological sampling in 2004 and 2010, (2) results of the 1998-99 statewide assessment of freshwater mussels in Iowa streams by Arbuckle et al.  (2000), (3) mussel surveys conducted by Iowa DNR staff in August 2012 and (4) EPA/IDNR fish contaminant monitoring in 2003.  

EXPLANATION:  Results from the IDNR/SHL biological sampling in 2004 and 2010 suggest that the Class B(WW1) uses should be assessed (evaluated) as "fully supported."  This assessment is based on data collected in 2004 and 2010 as part of the IDNR/UHL stream REMAP and biocriteria projects.   The 2004 REMAP FIBI scores were 46 (fair), 55 (good); and BMIBI scores were 86, 79 (excellent), and 70 (good).   The 2010 FIBI score was 57 (good) and the BMIBI score was 60 (good).   The aquatic life use support assessment was assessed as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports.   The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008.   The non-riffle habitat FIBI BIC for this ecoregion is 44 and the natural substrate BMIBI BIC for this ecoregion is 70.   This segment passed the FIBI BIC 3/3 times and passed the BMIBI BICs (2x natural and 2x artificial) 4/4 times.   For the 2006 assessment, this segment was assumed to contain stable riffle habitat based on best professional judgment and anecdotal data.   However, quantitative habitat data from the 2004 REMAP sampling was discovered and analyzed.   After comparing the results of the quantitative habitat data analysis to the riffle habitat requirements, it was determined that the sample site should be classified as "non-riffle" instead of "riffle".  

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 over a five-year period to be considered “monitored”.   This segment had multiple samples collected in the previous nine years.   Thus, the results of biological (fish/macroinvertebrate) sampling suggest that the aquatic life uses should be assessed (evaluated) as "fully supported."    

Results of IDNR surveys of freshwater mussels at two sites in this assessment segment in August 2012 suggest that the biological impairment of the Class B(WW1) aquatic life uses based on the apparent decline of freshwater mussels no longer exists.  The following is a summary of these surveys:

--Number of freshwater mussel species from surveys conducted in 1984 (Frest (1987), in 1998 (Arbuckle et al.  2000), and IDNR Watershed Improvement Section staff (J.  Kurth) in August 2012:

               1984           1998               2012
Site 12:        10              2                  9
Site 13:        9               6                  12

The original impairment was based on a comparison of sampling results from 1998 and 1999 (Arbuckle et al.  2000) to results from stream sites surveyed in 1984 and 1985 by Frest (1987).  Impairment was based on the percent change in the number of species of freshwater mussels found in the 1984-85 survey versus the 1998-99 survey.  Greater than a 50% decline in species richness from the 1984-85 to the 1998-99 period suggested an impairment of the aquatic life uses.  Based on IDNR’s assessment approach, the degree of decline (>50%) in the number of freshwater mussel species in this segment suggested “partial support” (impairment) of the Class B(WW) aquatic life uses for purposes of both Section 303(d) listing and 303(d) reporting.  Results of the IDNR's surveys in 2012, however, show recovery in the number of freshwater mussel species at the sites used to identify the original impairment (Sites 12 and 13), with 90% as many species found at Site 12 in 2012 than were found in 1984, and three more species were found at Site 13.  Due to the lack of a protocol for identifying biological thresholds that indicate "full support" of a freshwater mussel community, this impairment is moved from Category 5b of Iowa's Integrated Report to IR Category 3a (insufficient information to develop an assessment of support of uses).  

Fish consumption uses remain assessed (evaluated) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Twin Ponds Park in 2003.   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: 0.142 ppm; total PCBs: 0.094 ppm; and technical chlordane:  <0.03 ppm.   Levels of primary contaminants in the composite sample of walleye fillets were as follows:  mercury:  0.095 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.   The levels of contaminants in the sample collected from this assessment segment as part of the 2003 RAFT do not exceed any of Iowa’s advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.   Because these data are now over five years old, the data are considered less able to represent current water quality conditions; thus the assessment type is changed from a “monitored” (higher confidence) to an “evaluated” (lower confidence) assessment.