Assessment Comments

Assessment is based on: (1) the results of IDNR/UHL ambient monthly water quality monitoring conducted on the West Fork Cedar River at Finchford (IDNR station 10070003) during the 2004-2006 assessment period, (2) results of IDNR/UHL biological monitoring conducted from 2000-2002 as part of the IDNR biocriteria project, (3) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring near Allison in 2002 and (4) IDNR Fisheries Bureau fish sampling conducted in 2005.

Basis for Assessment

[Note:  Prior to the current (2008) Section 305(b) cycle, this river 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 assessed (monitored) as "not supported" due to levels of indicator bacteria that violate state water quality criteria.   The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" based on results of biological monitoring.   Fish consumption uses remain assessed (monitored) as “fully supported” based on fish contaminant monitoring in 2002.   Sources of data for this assessment include (1) the results of IDNR/UHL ambient monthly water quality monitoring conducted on the West Fork Cedar River at Finchford (IDNR station 10070003) during the 2004-2006 assessment period, (2) results of IDNR/UHL biological monitoring conducted from 2000-2002 as part of the IDNR biocriteria project, (3) results of U.S.  EPA/IDNR fish contaminant (RAFT) monitoring near Allison in 2002 and (4) IDNR Fisheries Bureau fish sampling conducted in 2005.  

EXPLANATION:  The presumptive Class A1 uses are assessed (monitored) as "not supported" based on results of ambient monitoring for indicator bacteria (E.  coli).   Due to recent changes in Iowa’s Water Quality Standards, Iowa’s assessment methodology for indicator bacteria has changed.   Prior to 2003, the Iowa WQ Standards contained a high-flow exemption for the Class A criterion for indicator bacteria (fecal coliforms) designed to protect primary contact recreation uses:  the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) did not apply "when the waters [were] materially affected by surface runoff."  Due to a change in the Standards in July 2003, E.  coli is now the indicator bacterium, and the high flow exemption was eliminated and replaced with language stating that the Class A criteria for E.  coli apply when Class A1, A2, or A3 uses “can reasonably be expected to occur.”  Because the IDNR Technical Advisory Committee on WQ Standards could not agree on what flow conditions would define periods when uses would not be reasonably expected to occur, all monitoring data generated for E.  coli during the assessment period, regardless of flow conditions during sample collection, will be considered for determining support of Class A uses for purposes of Section 305(b) assessments and Section 303(d) listings.  

The geometric mean level of indicator bacteria (E.  coli) in the 35 samples collected during the recreational seasons of 2004 through 2006 (195 orgs/100ml) exceeds the Iowa Class A1 water quality criterion of 126 orgs/100ml.   Fourteen of the 35 samples (40%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting and according to IDNR’s assessment/listing methodology, if the geometric mean level of E.  coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "not supported" (see pgs 3-33 to 3-35of U.S.  EPA 1997b).  

None of the approximately 40 samples collected during the 2004-2006 assessment period at the IDNR monthly station violated Class B(WW1) water quality criteria for ammonia-nitrogen; no violations occurred in the approximately 10 samples analyzed for pesticides and toxic metals.   One of 42 samples, however, did violate the respective Class B(WW1) criteria for dissolved oxygen and pH.   According to U.S.  EPA guidelines (U.S.  EPA 1997b, page 3-17), however, a violation frequency of less than 10 % for conventional parameters such as dissolved oxygen and pH do not suggest an impairment of aquatic life uses.   Thus, the percentages of violations of the dissolved oxygen and pH criteria at this station (both 2%) do not suggest an impairment of aquatic life uses in this stream segment.

Despite results of chemical/physical monitoring which suggest “full support” of the Class B(WW1) aquatic life uses, results of IDNR/UHL biological monitoring from 2000-2002 and IDNR Fisheries monitoring in 2005 suggest (evaluated) “partial support” of these uses.   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 2000-2002 BMIBI scores were 39, 45, 50 (fair).   The BMIBI average was 44.7.   The 2005 Fisheries FIBI score was 35 (fair).   The aquatic life use support was assessed (evaluated) as Partially Supporting (=PS), 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 non-riffle FIBI BIC for this ecoregion is 44 and the artificial substrate BMIBI BIC for this ecoregion is 52.   This assessment is considered evaluated because the drainage areas (824 and 850 mi2) above this sampling sites were greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria.   Even though this site failed to meet 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 remain assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Allison, Iowa, in 2002.   The composite samples of fillets from channel catfish and smallmouth bass had 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: 0.08 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 assessment segment:  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.