Cedar River IA 02-CED-450

Assessment Comments

Assessment is based on the results of (1) U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2006 and (2) IDNR/UHL stream REMAP biological monitoring in 2006.

Basis for Assessment

SUMMARY:  The Class A1 (primary contact recreation) uses remain "not assessed" due to the lack of water quality information upon which to base an assessment.   Fish consumption uses are assessed (monitored) as "fully supported" based on results of U.S.  EPA/IDNR fish contaminant (RAFT) monitoring in 2006.   The Class B(WW1) aquatic life uses are assessed (evaluated) as "fully supported" based on results of IDNR/UHL stream REMAP biological sampling in 2006.  

EXPLANATION:  The Class A1 uses remain "not assessed" due to the lack of water quality data or information upon which to base an assessment.  

This evaluated biological assessment was based on data collected in 2006 as part of the DNR/UHL stream REMAP project.   A series of biological metrics that 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 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 54 (good) and the BMIBI score was 43 (fair).  The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51.   This site passed the BMIBI BIC using the BMIBI UAV of 8 points.   This assessment is considered evaluated because the drainage area (7243 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 both the FIBI and BMIBI BICs, 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 are assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near West Branch in 2006.   The results from the 2006 sampling show low levels of the primary contaminants (chlordane, PCBs and mercury) in the composite sample of common carp fillets:  mercury:  0.266 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 support of fish consumption uses in Iowa’s rivers and lakes.   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 2006 RAFT sampling conducted in this assessment segment:  levels of all contaminants from this monitoring were below advisory trigger levels, thus suggesting the continued “full support” of fish consumption uses.