Assessment Comments
Assessment is based on: (1) monthly monitoring from January 2004 through December 2006 at the IDNR/UHL ambient station located at the Highway 61 bridge south of Keokuk (STORET station 10560001; formerly station 410085), (2) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2005 near Croton, (3) results of 2006 fish contaminant monitoring conducted as part of the IDNR/UHL REMAP biological monitoring project (REMAP Site 202), and (4) 2006 IDNR/UHL stream REMAP biological sampling near Farmington.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" based on results of monitoring for indicator bacteria (E. coli) from 2004-06; the Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" based on results of ambient chemical/physical water quality monitoring from 2004-06 and on the results from the 2006 IDNR/UHL stream REMAP sampling. Fish consumption uses are assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2005 and 2006. The sources of data for this assessment include results of (1) monthly monitoring from January 2004 through December 2006 at the IDNR/UHL ambient station located at the Highway 61 bridge south of Keokuk (STORET station 10560001; formerly station 410085), (2) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2005 near Croton,(3) results of 2006 fish contaminant monitoring conducted as part of the IDNR/UHL REMAP biological monitoring project (REMAP Site 202), and (4) 2006 IDNR/UHL stream REMAP biological sampling near Farmington. This is the same assessment as that developed for the upriver segment, IA 04-LDM-0010_2.
EXPLANATION: The Class A1 uses are assessed (monitored) as "partially 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 24 samples collected during the recreational seasons of 2004 through 2006 (79 orgs/100ml) is below the Iowa Class A1 water quality criterion of 126 orgs/100ml, thus suggesting relatively low levels of bacteria in this river segment. This result is consistent with previous assessments that have shown relatively low levels of indicator bacteria in this river segment. Six of the 24 samples (25%), however, exceeded Iowa’s single-sample maximum criterion 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 criterion 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 that the violation frequency of Iowa’s single-sample maximum criterion is significantly greater than 10%, and thus these results suggest impairment of the Class A1 uses of this river segment.
Results of ambient chemical/physical water quality suggest that the Class B(WW1) aquatic life uses should be assessed (monitored) as "fully supported." Results of monitoring from the IDNR ambient station at Highway 61 near Keokuk from 2004 through 2006 showed no violations of Class B(WW1) water quality criteria for dissolved oxygen or ammonia-nitrogen in the 36 samples collected, for toxic metals in the ten samples analyzed, or for pesticides in the seven sampled analyzed. As has been typical of monitoring results from this station, however, levels of pH occasionally violate the Class B(WW1) criterion of 9.0 pH units. During the 2004-2006 period, one of the 35 samples (3%) had a pH value greater than 9.0 units, with a maximum value of 9.1 units. Violations of the high-pH criterion in this river segment have tended to occur on days when dissolved oxygen levels were at or above 100% saturation, and these conditions suggest that high levels of primary productivity may have resulted in the high levels of pH observed. According to U.S. EPA guidelines for Section 305(b) reporting (U.S. EPA 1997b: page 3-17), a violation frequency for conventional parameters (including pH) of less than 10% does not suggest an impairment of aquatic life uses.
Supporting the results of the ambient WQ sampling, the results of the 2006 IDNR/UHL stream REMAP biological sampling also suggest the Class B(WW1) aquatic life uses should be assessed (evaluated) as "fully supported." 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 scores were 48 (fair) and 40 (fair). The 2006 BMIBI scores were 49 (fair) and 57 (good). The FIBI average was 44 and the BMIBI average was 53. 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 33 and the BMIBI BIC for this ecoregion is 41. This assessment is considered evaluated because the drainage area (14258 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.
For the 2006 305(b) cycle, biological data collected less than one mile from the confluence of the Des Moines and Mississippi Rivers were used for the assessment. After reviewing the situation, IDNR decided that the biological data collected in the upstream segment (IA 04-LDM-0010_2) were more representative of the IA 04-LDM-0010_1 segment than the data collected near the confluence. Although the data from both segments generated evaluated assessments because of the drainage areas of the sampling sites, it is the opinion of IDNR that the 2006 biological data collected from the IA 04-LDM-0010_2 segment will be used, in part, to assess the aquatic life uses of this segment until additional biological data can be collected. The 2003 biological data collected in the lower end of this segment, and the generated aquatic life assessment, can be found here: http://programs.iowadnr.gov/adbnet/assessment.aspx?aid=6994.
Fish consumption uses are assessed (monitored) as “fully supported” based on results of (1) U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Croton in 2005 and (2) IDNR/UHL REMAP monitoring near Farmington in 2006. The 2005 RAFT composite samples of fillets from common carp and freshwater drum had generally low levels of the primary contaminants. The 2005 sample of common carp fillets contained the following: mercury: 0.196 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. The 2005 sample of freshwater drum fillets contained the following: mercury: 0.152 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. Results of fish contaminant monitoring conducted in this assessment segment in September 2006 as part of the IDNR/UHL REMAP project (Site 202) showed similar results in the composite samples of common carp fillets: mercury: 0.258 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 2005 RAFT sampling or the 2006 REMAP 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.
