Assessment Comments
Assessment remains based on: (1) monthly monitoring from January 2004 through December 2006 at the IDNR/SHL 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 2009 near Keokuk, (3) results of 2006 fish contaminant monitoring conducted as part of the IDNR/SHL REMAP biological monitoring project (REMAP Site 202), and (4) 2006 IDNR/SHL stream REMAP biological sampling near Farmington.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses remain assessed (monitored) as “partially supported” (IR 5a) due to levels of indicator bacteria that exceed state water quality criteria. The Class B(WW1) aquatic life uses remain assessed (monitored) as "fully supported" (IR 2a) based on results of ambient chemical/physical water quality monitoring from 2004-06 and on the results from the 2006 IDNR/SHL stream REMAP sampling. Fish consumption uses are assessed (monitored) as "fully supported" (IR 2a) based on results of fish contaminant monitoring in 2009. 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 2009 near Croton,(3) results of 2006 fish contaminant monitoring conducted as part of the IDNR/SHL REMAP biological monitoring project (REMAP Site 202), and (4) 2006 IDNR/SHL stream REMAP biological sampling near Farmington. This is the same assessment as that developed for the upriver segment, IA 04-LDM-0010_2 and is the same assessment developed for the previous IR cycles. Note: routine ambient monitoring at IDNR station 10560001 was terminated in November 2006.
EXPLANATION: The Class A1 uses remain assessed as "partially supported" based on results of monitoring for indicator bacteria (E. coli) at the IDNR/SHL ambient monitoring station on the Des Moines River south of Keokuk. 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) was below the Iowa Class A1 water quality criterion of 126 orgs/100ml, thus suggesting relatively low levels of bacteria in this river segment (note: IDNR/SHL ambient monitoring at this monitoring station was terminated after 2006). The relatively low geometric mean for E. coli for the 2004-06 period is consistent with previous assessments that have shown relatively low levels of indicator bacteria in this river segment. Six of the 24 samples (25%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting, if the geometric mean of E. coli is less than the applicable state criteria, the contact recreation uses should be assessed as "fully supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b). Thus, these data suggest that the Class A1 uses should be assessed as “fully supported. These EPA guidelines, however, also suggest that if more than 10% of samples exceed the single-sample maximum criterion for indicator bacteria, the primary contact recreation uses should be assessed as "partially supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). According to IDNR’s assessment/listing methodology, the monitoring data from 2004-06 suggest that significantly greater than 10% of the samples exceed IDNR’s single-sample maximum criterion, thus suggesting that the Class A1 uses should be assessed as “partially supported/impaired.” Because these data are now older than five years, the assessment type is changed from “monitored” (a higher confidence assessment) to “evaluated” (a lower confidence assessment). Regardless, the previously-identified bacteria impairment remains in place.
Results of ambient chemical/physical water quality monitoring from 2004-06 suggested 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.
The results of the 2006 IDNR/SHL stream REMAP biological sampling support the results of the ambient WQ sampling and also suggest that 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 IDNR/SHL 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 62 (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 1994-2008. The FIBI BIC for this ecoregion is 33 and the BMIBI BIC for this ecoregion is 41. This segment passed the FIBI BIC 2/2 times and passed the BMIBI BIC 2/2 times in 2006. This assessment is considered evaluated because the drainage area (14214 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. In addition, these data are now greater than five years old; thus, they are not reliable enough on which to base a "monitored" assessment.
This aquatic life assessment is now also considered "evaluated" based on a change in the 2010 IDNR assessment methodology. IDNR now requires a segment have two or more biological samples collected from the segment in multiple years over a five-year period to be considered “monitored”. This segment had multiple samples collected; however, the samples were not collected in multiple years nor in the last five years.
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 remain assessed (monitored) as “fully supported” based on results of (1) U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Keokuk in 2009 and (2) IDNR/UHL REMAP monitoring near Farmington in 2006. Results of fish contaminant monitoring conducted in this assessment segment in September 2006 as part of the IDNR/UHL REMAP project (Site 202) showed low levels of contaminants in the composite samples of common carp fillets: mercury: 0.258 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. The 2009 RAFT composite samples of fillets from common carp and freshwater drum had generally low levels of the primary contaminants. The 2009 sample of common carp fillets contained the following: mercury: 0.22 ppm; total PCBs: 0.136 ppm; and technical chlordane: 0.086 ppm. The level of mercury in the 2009 sample of freshwater drum fillets was 0.181 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. The fish contaminant data generated from the 2009 RAFT sampling and the 2006 REMAP sampling conducted in this assessment segment, however, show that the levels of contaminants do not exceed any of the advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.
