Assessment Comments

Assessment remains based on: (1) results of IDNR/UHL ambient water quality monitoring downstream of Independence (station 10100002) from 2004 through 2006, (2) results of biological monitoring by IDNR Fisheries in 2002, (3) results of EPA/IDNR fish tissue (RAFT) monitoring in 2000 approximately 1 mile southeast of Independence, and (4) results of an IDNR fish kill investigation in August 2005.

Basis for Assessment

SUMMARY:  Class A1 (primary contact recreation) uses remain assessed (monitored) as “fully supported.”  The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" based on occurrence of a fish kill in 2005.   Fish consumption uses remain assessed (evaluated) as "fully supported" based on results of U.S.  EPA/IDNR fish contaminant monitoring in 2000.   The sources of data for this assessment include (1) results of IDNR/UHL ambient water quality monitoring downstream of Independence (station 10100002) from 2004 through 2006, (2) results of biological monitoring by IDNR Fisheries in 2002, (3) results of EPA/IDNR fish tissue (RAFT) monitoring in 2000 approximately 1 mile southeast of Independence, and (4) results of an IDNR fish kill investigation in August 2005.   (Note:  routine ambient monitoring at IDNR/UHL station 10100002 downstream from Independence was discontinued in 2006.)

EXPLANATION:  The Class A1 (primary contact recreation) uses remain assessed as “fully supported.”  The geometric mean level of indicator bacteria (E.  coli) in the 24 samples collected from the IDNR/UHL ambient station during the recreational seasons of 2004, 2005, and 2006 (57 orgs/100ml) is well-below the Iowa Class A1 water quality criterion of 126 orgs/100ml.   According to U.S.  EPA guidelines for Section 305(b) reporting, “full support” of primary contact recreation uses is suggested if the geometric mean level is below the water quality criterion.  

The results of IDNR/UHL ambient water quality monitoring from 2004 through 2006 also suggest "full support" of the Class B(WW1) uses due to the lack of violations of state water quality criteria for pH, dissolved oxygen, and ammonia-nitrogen in the approximately 35 samples collected during the 2004-2006 period.   In addition, no violations of Class B(WW1) chronic criteria occurred in the seven samples analyzed for the pesticide chlorpyrifos during this period.   None of the ten samples analyzed for toxic metals violated the respective Class B(WW1) criteria.  

Results of biological monitoring conducted in 2002 by the IDNR Fisheries Bureau suggest that the Class B(WW1) aquatic life use should be assessed (evaluated) as "fully supported."  A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the Fisheries sampling data.   The biological metrics are based on the numbers and types of 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).   The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2002 evaluated FIBI was 65 (good).   The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI score 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 1994-2004.   The riffle site FIBI BIC for this ecoregion is 65.   The segment passed the FIBI BIC 1/1 times in 2002.  

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 a single sample collected in 2002.   Additionally, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).  

The occurrence of a fish kill in this river segment late August, 2005, however, suggests that the Class B(WW) uses of this river segment should be assessed (evaluated) as impaired.   IDNR Fisheries staff investigated the kill.   Seventeen dead channel catfish ranging in length from 12 to more than 20 inches were found immediately downriver from the Independence Dam; only channel catfish appeared to have been affected by the kill.   The kill was attributed to stress associated with high water temperatures and was not caused by a pollutant.   According to IDNR’s assessment and listing methodology, a single fish kill attributed to non-pollutant sources within the most recent three-year period suggests that the aquatic life uses should be assessed (evaluated) as “partially supported.”  Due to lack of a pollutant source, this type of kill is not appropriate for Section 303(d) listing but is appropriate for Subcategory 2b of Iowa's Integrated Report.  

Fish consumption uses remain assessed (evaluated) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring downstream from Independence in 2000.   The composite samples of fillets from channel catfish and smallmouth bass 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.   Levels of contaminant in fish tissue samples from the 2000 RAFT sampling conducted in this segment of the Wapsipinicon River were all below IDNR/IDPH advisory trigger levels.   Thus, these results suggest no justification for issuance of a consumption advisory for this waterbody and “full support” of fish consumption uses.