Assessment Comments

Assessment is based on (1) 2002 biocriteria data from the Dorchester monthly site(evaluated): BM-IBI= 58 (good); (2) DNR monthly fixed monitoring station near Dorchester, and (3) EPA/IDNR fish tissue (RAFT) monitoring in 1998.

Basis for Assessment

SUMMARY:  The Class A (primary contact recreation) uses are assessed as “partially supported” due to high levels of indicator bacteria.   The Class B(WW) aquatic life uses were assessed (evaluated) as "fully supported".   Fish consumption uses are assessed as "fully supported/threatened" (impaired) based on results of fish contaminant monitoring in 2004.   Sources of data for this assessment include (1) results of DNR ambient monthly water quality monitoring conducted on the Upper Iowa River near Dorchester (station 10030001) during the period January 2002 through December 2004, (2) results of monitoring for indicator bacteria conducted at UIRW Site 30 near New Albin from July 2002 through June 2003 as part of the Upper Iowa River Watershed project (3) results of IDNR/UHL biological monitoring in 2002, and (4) results of U.S.  EPA/IDNR fish contaminant (RAFT) monitoring in 2004.   Note:  this is the same assessment as used for the next down-river segment:  IA 01-UIA-0090-0.

EXPLANATION:  The Class A (primary contact recreation) uses are assessed as "partially supported" due to high levels of indicator bacteria (E coli).   Fifty-six samples from this station were analyzed for indicator bacteria (E.  coli) during recreational seasons of 2002 through 2004.  

Due to recent changes in Iowa’s Water Quality Standards, Iowa’s 2006 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 the 2006 Section 305(b) assessments and Section 303(d) listings.  

The geometric mean of E.  coli bacteria in the 56 samples analyzed at the IDNR/UHL station was 59 orgs/100 ml; this geometric mean is well-below the Iowa water quality standard of 126 orgs/100 ml.   Fourteen of the 56 samples, however, (25%) exceeded the EPA-recommended single-sample maximum value of 235 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting, if more than 10% of samples exceed the single-sample maximum value, the primary contact recreation uses are "partially supported" (see pgs 3-33 to 3-35of U.S.  EPA 1997b)  According to IDNR’s assessment/listing methodology, these results suggest significantly greater than 10% of the samples exceed IDNR’s single-sample maximum value, thus suggesting that the Class A uses should be assessed as “partially supported/impaired”.  

The geometric mean level of indicator bacteria (E.  coli) in the 31 samples collected during the recreational seasons of 2003 and 2004 (61 orgs/100ml) at UIRW project Site 30 was well-below the Iowa Class A water quality criterion of 126 orgs/100ml, thus also suggesting relatively low levels of bacteria in this stream segment.   Six of the 31 samples (19%), however, exceeded Iowa’s single-sample maximum value of 235 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting, if levels of E.  coli exceed the single-sample maximum value in more than 10% of the samples, the primary contact recreation uses should be assessed as “partially supported” (see pgs 3-33 to 3-35of U.S.  EPA 1997b).   According to IDNR’s assessment/listing methodology, these results suggest significantly greater than 10% of the samples exceed IDNR’s single-sample maximum value, thus suggesting that the Class A uses should be assessed as “partially supported/impaired”.  

The Class B(WW) aquatic life uses were assessed as "fully supported".   None of the approximately 36 samples from the IDNR/UHL station analyzed for conventional pollutants and ammonia, and none of the approximately 10 samples analyzed for pesticides and toxic metals other than lead exceeded a state Class B(WW) criterion.   .   Of the ten samples analyzed for toxic metals, only one sample violated a Class B(WW) criterion:  one of the ten samples analyzed for lead exceeded the Class B(WW) criterion of 30 ug/l.   This violation occurred on July 6, 2004; the level of lead in the sample was 40 ug/l.   According to U.S.  EPA guidelines for Section 305(b) water quality assessments (U.S.  EPA 1997b, page 3-18), however, one violation of a water quality criterion for a toxic pollutant in an abundant data set (at least 10 samples over at three-year period) does not indicate an impairment of aquatic life uses.  

As noted in the 2004 Section 305(b) assessments for this river segment, results of biological monitoring conducted in 2002 as part of the IDNR/UHL stream biocriteria project suggest “full support” of the aquatic life 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 (F-IBI) and a benthic macroinvertebrate index (BM-IBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2002 Fish IBI score was unavailable and the BM-IBI score was 58 (good).  The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the BM-IBI score with biological assessment criteria established for previous Section 305(b) reports.  The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.

Fish consumption uses were assessed (monitored) as “fully supported / threatened” (impaired) based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Dorchester in 2004.   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 (IDPH), 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 applies to the fish contaminant data generated from the 2004 RAFT sampling conducted in this assessment segment.   Although previously assessed as “fully supported”, the levels of contaminants now exceed one or more advisory trigger levels, thus suggesting a potential need to issue a consumption advisory before the next assessment/listing cycle.   Iowa DNR’s assessment methodology states that if elevated levels of contaminants suggest the potential for a consumption advisory, the fish consumption uses should be assessed as “fully supported/threatened”.  

The composite samples of fillets from common carp and smallmouth bass had generally low levels of contaminants.   Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.228 ppm; total PCBs:  0.13 ppm; and technical chlordane: <0.03 ppm.   Levels of primary contaminants in the composite sample of smallmouth bass fillets were as follows: mercury: 0.486 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm.   The levels of mercury in 2004 samples of both common carp and smallmouth bass, however, exceed the IDNR/IDPH trigger level of 0.20 ppm for a one meal per week consumption advisory:  the level of mercury in the sample of common carp fillets was 0.228 ppm and in the sample of smallmouth bass fillets was 0.486 ppm.   According to the IDNR/IDPH advisory protocol, two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory.   Because, however, the level of contaminants in the 2004 sample of smallmouth bass fillets was more than twice the 1 meal/week advisory trigger level, the fish consumption uses are assessed as “fully supported/threatened” (impaired).   Additional (follow-up) monitoring will be conducted in 2006 to determine whether an advisory is needed for this waterbody.