West Fork Cedar River IA 02-WFC-802

Assessment Comments

Assessment remains based on results of (1) IDNR/UHL biocriteria sampling in 2006 and (2) U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2002.

Basis for Assessment

[Note:  Prior to the current (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 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), this segment is also now presumptively 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 presumptive Class A1 (primary contact recreation) uses are "not assessed" due to the lack of information upon which to base an assessment.   The Class B(WW1) aquatic life uses are assessed (evaluted) as fully supporting based on results of IDNR/UHL biological monitoring in 2006.   Fish consumption uses remain assessed (monitored) as “fully supported” based on results of U.S.  EPA/IDNR fish contaminant monitoring near Allison in July 2002.  

EXPLANATION:  The assessment of the Class B(WW1) aquatic life uses was based on data collected in 2006 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 (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 2006 FIBI score was 65 (good) and the BMIBI score was not available due to flooding removing the artificial substrates.   The aquatic life use support was assessed 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 non-riffle site FIBI BIC for this ecoregion is 44.   This assessment is considered evaluated because the drainage area (554 mi2) above this sampling site 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, 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

Fish consumption uses remain assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Allison in 2002.   The composite samples of fillets from channel catfish and smallmouth bass had very low levels of contaminants.   Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.105 ppm; total PCBs: 0.094 ppm; and technical chlordane: 0.045 ppm.   Levels of primary contaminants in the composite sample of smallmouth bass fillets were as follows: mercury: 0.080 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 segment of the West Fork Cedar River:  the levels of contaminants do not exceed any of the new (2006) advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.