Assessment Comments
Assessment is based on results of (1) statewide assessment of freshwater mussels in Iowa (Arbuckle et al. 2000) (2) monitoring conducted in 2002-03 for indicator bacteria as part of the Upper Iowa River Watershed project, and (3) EPA/DNR fish contaminant monitoring in 2002 and 2005.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses are assessed (monitored) as “not supported” due to high levels of indicator bacteria. The Class B(WW) aquatic life uses are assessed (monitored) as "not supported" based on results of a 1998-99 statewide assessment of freshwater mussels in Iowa streams. Fish consumption uses are assessed as “partially supported” based on results of fish contaminant monitoring in 2002 and 2005. Sources of data for this assessment include (1) results of monitoring for indicator bacteria conducted at UIRW Site 17 near Freeport from July 2002 through June 2003 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), and (3) U.S. EPA/IDNR fish tissue (RAFT) monitoring in 2002 and 2005 near Decorah.
EXPLANATION: The Class A uses are assessed as “not supported” due to levels of indicator bacteria (E. coli) that exceed state water quality criteria. The geometric mean level of indicator bacteria (E. coli) in the 32 samples collected during the recreational seasons of 2003 and 2004 (133 orgs/100ml) slightly exceeded the Iowa Class A water quality criterion of 126 orgs/100ml. In addition, nine of the 32 samples (28%) exceeded Iowa’s single-sample maximum value 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).
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 Class B(WW) uses remain assessed (monitored) as "not supported" based on information from the 1998-99 statewide survey of freshwater mussels (Arbuckle et al. 2000). Results from this assessment 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 Water Quality Bureau 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. The confidence level of this assessment is relatively high; thus the assessment type is considered “monitored” in the context of Section 305(b) reporting. According to Iowa DNR’s assessment methodology, waterbodies identified as “impaired” based on a “monitored” assessment are candidates for Section 303(d) listing. 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 (monitored) 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.
Fish consumption uses were assessed (monitored) as “partially supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring upstream from Decorah in 2002 and in 2005. 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 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, exceeds the IDNR/IDPH trigger level of 0.20 ppm for a one meal per week consumption advisory (this levels 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 0.2 ppm.
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 level of mercury in sample of smallmouth bass fillets from the next (2005) sampling (0.292 ppm) also exceeded this advisory trigger level, issuance of a fish consumption advisory is justified. This advisory was issued by IDNR and IDPH in January 2006 and covers 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.
