Assessment Comments

Assessment is based on: (1) results of IDNR/UHL ambient monthly water quality monitoring conducted on the Upper Iowa River near Dorchester (station 10030001) during the period January 2004 through December 2006, (2) results of monitoring conducted by the Long-Term Resource Monitoring Program at LTRMP station UI02.9M from 2002-04, (3) results of monitoring for indicator bacteria conducted at Upper Iowa River Watershed project Site 30 near New Albin from April 2004 through October 2006, (4) results of IDNR/UHL biological monitoring in 2002 and 2005, and (5) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2004 and 2006.

Basis for Assessment

[Note:  Prior to the current (2008) Section 305(b) cycle, this stream segment was designated for Class A1 (primary contact recreation) uses and B(WW) aquatic life 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 remains designated for both primary contact recreation uses (still termed Class A1) and for aquatic life uses (now termed Class B(WW1).   In addition, this assessment segment also remains designated for fish consumption uses (now termed Class HH (human health/fish consumption) uses).]

SUMMARY:  The Class A1 (primary contact recreation) uses are assessed (monitored) as “not supported” due to high levels of indicator bacteria that exceed state water quality criteria.   The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported".   Fish consumption uses are assessed (monitored) as "partially supported based on issuance of a fish consumption advisory for this segment of the Upper Iowa River in 2008.   Sources of data for this assessment include (1) results of IDNR/UHL ambient monthly water quality monitoring conducted on the Upper Iowa River near Dorchester (station 10030001) during the period January 2004 through December 2006, (2) results of monitoring conducted by the Long-Term Resource Monitoring Program at LTRMP station UI02.9M from January 7, 2002 through September 20, 2004, (3) results of monitoring for indicator bacteria conducted at Upper Iowa River Watershed project Site 30 near New Albin from April 2004 through October 2006, (4) results of IDNR/UHL biological monitoring in 2002 and 2005, and (5) results of U.S.  EPA/IDNR fish contaminant (RAFT) monitoring in 2004 and 2006.  

EXPLANATION:  The Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" due to levels of indicator bacteria (E coli) that exceed state water quality criteria.   A total of forty-five samples from this assessment segment were analyzed for indicator bacteria (E.  coli) during recreational seasons of 2004 through 2006:  24 samples were analyzed at the INDR/UHL ambient water quality monitoring station near Dorchester; 21 samples were analyzed at Upper Iowa River Watershed Project site 30 near New Albin.  

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 of E.  coli bacteria in the 24 samples analyzed at the IDNR/UHL ambient monitoring station near Dorchester was 103 orgs/100 ml; this geometric mean is below the Iowa water quality standard of 126 orgs/100 ml.   These results are consistent with results of previous monitoring that show generally low levels of indicator bacteria in this river segment.   Although the geometric mean for E.  coli meets state water quality criteria, six of the 24 samples (25%) exceeded Iowa’s single-sample maximum criterionsample maximum criterioncriterion 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 criterionsample maximum criterion, 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 criterionsample maximum criterion, 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 21 samples collected during the recreational seasons of 2004 through 2006 (153 orgs/100ml) at UIRW project Site 30 near New Albin exceeded the Iowa Class A1 water quality criterion of 126 orgs/100ml.   Seven of the 21 samples (33%) exceeded Iowa’s single-sample maximum criterionsample maximum criterion of 235 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if the geometric mean 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).   Note:  LTRMP monitoring does not include analysis for indicator bacteria.

The Class B(WW1) aquatic life uses were assessed (monitored) as "fully supported."  Similar to the previous (2006) assessment cycle, 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(WW1) criterion of 30 ug/l.   This violation occurred on July 6, 2004; the level of lead in the sample was 40 ug/l.   None of the subsequent seven samples analyzed for lead during from October 2004 through January 2006 contained levels of lead above the Class B(WW1) chronic criterion.   The occurrence of this single violation of a water quality criterion for a toxic parameter does not suggest an impairment:  according to U.S.  EPA guidelines for Section 305(b) water quality assessments (U.S.  EPA 1997b, page 3-18), 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.   None of the 29 samples analyzed from LTRMP station UI02.9M from 2002-2004 violated Class B(WW1) criteria for dissolved oxygen or pH; none of the 16 samples analyzed for ammonia exceeded Class B(WW1) criteria (maximum value 0.09 mg/l).

This evaluated biological assessment was based on data collected in 2002 and 2005 as part of the DNR/UHL stream biocriteria and REMAP projects.   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 2002 FIBI score was unavailable and the BMIBI score was 58 (good).   The 2005 REMAP FIBI scores were 57 (good) and 82 (excellent).   The 2005 REMAP BMIBI scores were 87 (excellent) and 76 (excellent).   The FIBI average (n=2) was 70 and the BMIBI average (n=3) was 74.   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 52 and the BMIBI BIC for this ecoregion is 61.   This assessment is considered evaluated because the drainage area (938 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 “partially supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Dorchester in 2004 and 2006.   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 from the 2004 RAFT monitoring exceeded 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 (impaired)”; this was the assessment used for the 2006 305(b) cycle.

The composite samples of fillets from the 2004 samples of 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 exceed the IDNR/IDPH trigger level of 0.30 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.  

The composite samples of fillets from the 2006 RAFT samples of golden redhorse (Moxostoma erythrurum) and smallmouth bass had similarly high levels of mercury.   Levels of mercury in the composite sample of golden redhorse fillets was 0.362 ppm, and the level of mercury in the composite sample of smallmouth bass fillets was 0.37 ppm.   According to the IDNR/IDPH advisory protocol, if two consecutive samplings show that contaminant levels are above an advisory trigger level in fillet samples, a consumption advisory will be issued.   Because levels of mercury in both the 2004 and 2006 samples of smallmouth bass exceed the IDNR/IDPH trigger level of 0.30 ppm for a one meal per week consumption advisory, a consumption advisory was issued for this segment by IDNR in March 2008.   Because level of mercury in the sample of the bottom-feeding golden redhorse was also greater than the advisory level, all fish species were included in the one-meal/week advisory.   The existence of a consumption advisory for this assessment segment suggests that the fish consumption uses are “partially supported.”  The original advisory issued in 2006 covered the Upper Iowa River from the Lower Dam in eastern Winneshiek County upriver to County Road W20 approximately 5.5 miles upriver from Decorah.   This new advisory extends the existing advisory issued in 2006 downriver from the Lower Dam to state highway 76.