Assessment Comments
Assessment is based on results of (1) results of monitoring for indicator bacteria conducted at UIRW Site 17 near Freeport from April 2004 through October 2006 as part of the Upper Iowa River Watershed project, (2) results of monitoring at one site for the 1998-99 statewide assessment of freshwater mussels in Iowa streams (Arbuckle et al. 2000), (3) IDNR/UHL stream REMAP biological sampling near Decorah in 2006, and (4) U.S. EPA/IDNR fish tissue (RAFT) monitoring in 2002, 2005, and 2006 near Decorah.
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 primary contact recreation uses (still termed Class A1) and for aquatic life uses (now termed Class B(WW1). In addition, this assessment segment 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. The Class B(WW1) aquatic life uses are assessed (evaluated) as "not supported" based on results of a 1998-99 statewide assessment of freshwater mussels in Iowa streams. Contrary to the mussel findings, fish and benthic macroinvertebrate communities sampled in 2006 indicate "full support" of Class B(WW1) aquatic life uses. Fish consumption uses are assessed as “partially supported” based on results of fish contaminant monitoring in 2002, 2005, and 2006. Sources of data for this assessment include (1) results of monitoring for indicator bacteria conducted at UIRW Site 17 near Freeport from April 2004 through October 2006 as part of the Upper Iowa River Watershed project, (2) results of monitoring at one site for the 1998-99 statewide assessment of freshwater mussels in Iowa streams (Arbuckle et al. 2000), (3) 2006 IDNR/UHL stream REMAP sampling, and (4) U.S. EPA/IDNR fish tissue (RAFT) monitoring in 2002, 2005, and 2006 near Decorah.
EXPLANATION: The Class A1 uses are assessed (monitored) as “not supported” due to levels of indicator bacteria (E. coli) that exceed state water quality criteria.
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 A1 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 18 samples collected at UIRW site 17 during the recreational seasons of 2004 through 2006 (142 orgs/100ml) slightly exceeds the Iowa Class A water quality criterion of 126 orgs/100ml. In addition, seven of the 18 samples (28%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and the IDNR 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). Also, U.S. EPA guidelines for Section 305(b) reporting state that if more than 10% of samples exceed the single-sample 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 (i.e., seven of 18 samples, 39% exceeding) suggest significantly greater than 10% of the samples exceed IDNR’s single-sample maximum criterion, thus also suggesting that the Class A uses should be assessed as impaired.
The Class B(WW1) uses remain assessed as "not supported" based on information from the 1998-99 statewide survey of freshwater mussels (Arbuckle et al. 2000). Because the data upon which this assessment is based are more than five years old, the assessment type is changed from “monitored” (i.e., a higher confidence assessment) to “evaluated” (i.e., a lower confidence assessment). Despite the change in assessment type, this segment remains Section 303(d)-impaired due to a decline in freshwater mussels. Results from this survey suggest a potential impairment to the aquatic life uses of this stream segment. As part of this study, sampling results from 1998 and 1999 (Arbuckle et al. 2000) were compared to results from stream sites surveyed in 1984 and 1985 by Frest (1987). On a statewide basis, this comparison showed sharp declines in the numbers of mussel species ("species richness") in Iowa’s streams and rivers from the mid-1980s to the late 1990s. Results of this comparison were used by staff of the Iowa DNR to assess the degree to which the aquatic life uses of the sampled stream segments are supported. For purposes of Section 303(d) listing, this assessment was based on the percent change in the number of species of freshwater mussels found in the 1984-85 survey versus the 1998-99 survey. Greater than a 50% decline in species richness from the 1984-85period to the 1998-99 period suggests an impairment of the aquatic life uses. Species richness of freshwater mussels at the one sample site in this stream segment was 6 in the 1984-85 period and was 0 in the 1998-99 period for a percent change of minus 100%. Based on these results, the aquatic life use are assessed as "not supported" for purposes of both Section 303(d) listing and Section 305(b) reporting. As presented by Arbuckle et al. (2000), the potential causes of declines in species richness of Iowa's freshwater mussels include siltation, destabilization of stream substrate, stream flow instability, and high in-stream levels of nutrients (phosphorus and nitrogen). Their study also suggested the importance of stream shading provided by riparian vegetation to mussel species richness. Additional monitoring is needed to better define the biological status of this stream segment as well as the site-specific causes and sources of impairment of these uses that may exist. Because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence). Despite this change in assessment type, this waterbody remains in IR Category 5b.
Contrary to the mussel findings in the late 1980s, the fish and benthic macroinvertebrate communites appear to be healthy. 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 81 (excellent) and the BMIBI score was 75 (good). 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 (584 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 upstream from Decorah in 2002, 2005 and 2006 and on the issuance of a fish consumption advisory in 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 RAFT sampling conducted in this segment of the Upper Iowa River: levels of mercury in samples of smallmouth bass from consecutive samplings exceeded advisory trigger levels, thus suggesting the need for a consumption advisory. According to IDNR’s assessment methodology, the existence of a one-meal/week consumption advisory indicates that fish consumption uses should be assessed as “partially supported”.
For the 2002 RAFT sampling, 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: 0.036 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm. Levels of primary contaminants in the composite sample of smallmouth bass fillets were as follows: mercury: 0.334 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm. The level of mercury in the sample of smallmouth bass (0.0.334 ppm), however, exceeded the IDNR/IDPH trigger level of 0.30 ppm for a one meal per week consumption advisory (this level is well below the “do not eat” trigger level for mercury of 1.0 ppm).
For the 2005 RAFT sampling, levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.036 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm. Levels of primary contaminants in the composite sample of smallmouth bass fillets were as follows: mercury: 0.334 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm. Similar to the 2002 sampling, the level of mercury in the smallmouth bass fillets at this site exceeded the IDNR/IDPH trigger level of 0.3 ppm.
The 2006 RAFT sampling produced similar results. The composite sample of smallmouth bass fillets contained 0.32 ppm of mercury. The sample of golden redhorse (Moxostoma erythrurum) fillets contained 0.567 ppm of mercury. Both of these levels were above the 0.3 one-meal/week advisory trigger level.
According to the IDNR/IDPH advisory protocol, if two consecutive samplings show that contaminant levels are above the trigger level in fillet samples, issuance of a consumption advisory is justified. Because the levels of mercury in samples of smallmouth bass fillets from this river segment consistently have been at or above the advisory trigger level, a one-meal/week advisory was issued by IDNR and IDPH in January 2006. This advisory originally covered the reach of the Upper Iowa River from the Lower Dam in eastern Winneshiek County to the county road bridge approximately 5.5 miles upriver (northwest) from Decorah. Additional fish contaminant (RAFT) monitoring in 2006 resulted in extending this advisory downriver from the Lower Dam to state highway 76.
