Assessment Comments
Assessment is based on: (1) results of monthly monitoring from 2010 through 2012 at the IDNR/SHL ambient city monitoring station located downstream from Fort Dodge near Kalo (STORET station 10940003), (2) results of U.S. EPA/IDNR fish tissue (RAFT) monitoring near Dolliver State Park in 2005 and downstream of Fort Dodge in 2009, (3) results of 2006 fish contaminant monitoring conducted as part of the IDNR/SHL REMAP biological monitoring project (REMAP Site 221), and (4) IDNR/SHL biological sampling conducted in 2012.
Basis for Assessment
[Note 1: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(WW) aquatic life uses, including fish consumption uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008, and due to the completion of a Use Attainability Analysis in 2007, this segment is also now designated for Class A1 (primary contact recreation) uses. This segment remains designated for warmwater aquatic life use (now termed Class B(WW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption uses).]
[Note 2: This assessment (except the biological sampling) was also used for the adjacent downstream segment of the Des Moines River (IA 04-UDM-0040-1).]
SUMMARY: Despite relatively low levels of indicator bacteria during the 2010-12 monitoring period, the Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" (IR 5a). The Class B(WW1) aquatic life uses are assessed (evaluated) as "fully supported" (IR 2a) based on results of biological monitoring in 2006. Fish consumption uses are assessed (monitored) as "fully supported" (IR 2a) based on results of fish contaminant monitoring in 2005, 2006, and 2009. The sources of data for this assessment include (1) results of monthly monitoring from 2010 through 2012 at the IDNR/SHL ambient city monitoring station located downstream from Fort Dodge near Kalo (STORET station 10940003), (2) results of U.S. EPA/IDNR fish tissue (RAFT) monitoring near Dolliver State Park in 2005 and 2009, (3) results of 2006 fish contaminant monitoring conducted as part of the IDNR/SHL REMAP biological monitoring project (REMAP Site 221), and (4) IDNR/SHL biological sampling near Fort Dodge in 2012.
EXPLANATION: Despite relatively low levels of indicator bacteria during the 2010-12 assessment period, the Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" based on results of monitoring for indicator bacteria (E. coli). The geometric means of indicator bacteria (E. coli) in the 25 samples collected during the recreational seasons of 2010 through 2012 at IDNR station 10940003 downstream from Fort Dodge were as follows: the 2010 geometric mean was 99 orgs/100 ml, the 2011 geometric mean was 129 orgs/100 ml, and the 2012 geometric mean was 32 orgs/100 ml. Only the 2011 geometric mean exceeded—and only very slightly exceeded—the Class A1 criterion of 126 orgs/100 ml. The 2011 geometric mean is the only one of the geometric means from 2008 through 2012 to exceed the Class A1 criterion, thus indicating very low levels of indicator bacteria in this assessment segment. Five of the 25 samples (20%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml. According to IDNR’s assessment methodology two conditions need to be met for results of monitoring for indicator bacteria to indicate “full support” of the Class A1 (primary contact recreation) uses: (1) the geometric mean of the samples from each recreation season of the three-year assessment period must be less than the state’s geometric mean criterion of 126 E. coli orgs/100 ml and (2) not more than 10% of the samples during any one recreation season exceeds the state’s single-sample maximum value of 235 E. coli orgs/100 ml. If a sampling season geometric mean exceeds the state criterion of 126 orgs/100 ml during the three-year assessment period, the Class A1 uses should be assessed as “not supported.” Also, if significantly more than 10% of the samples in any one of the three recreation seasons exceed Iowa’s single-sample maximum value of 235 E. coli orgs/100 ml, the Class A1 uses should be assessed as “partially supported.” This assessment approach is based on U.S. EPA guidelines (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Thus, because at least one geometric mean exceeded the Class A1 criterion during the 2010-12 assessment period, the Class A1 uses are assessed as “not supporting”.
The ambient water quality monitoring data indicate that the Class B(WW1) aquatic life uses should be assessed (monitored) as "fully supported.” Ambient chemical/physical monitoring conducted at the IDNR city station downstream from Fort Dodge from 2010-2012 showed no violations of Class B(WW1) water quality criteria for dissolved oxygen, pH, temperature, ammonia-nitrogen, chlorine, or sulfate in the 36 samples collected or in the three samples analyzed for toxic metals (including mercury). These results suggest that the Class B(WW1) uses should be assessed as "fully supported."
In agreement with the results of the ambient water quality monitoring, the results from the 2012 IDNR/SHL large river biological sampling indicate that the Class B(WW1) aquatic life uses should be assessed (evaluated) as "fully supported.” This biological assessment was based on data collected in 2006 as part of the IDNR/SHL stream large river sampling 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 collected in the stream sampling reach. The biological metrics were combined to make a benthic macroinvertebrate index (BMIBI). The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2012 BMIBI score was 72 (good). The aquatic life use support was assessed (evaluated) as filly supporting (=FS), based on a comparison of the BMIBI score with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The BMIBI BIC for this ecoregion is 62. This assessment is considered evaluated because the drainage area (4,259 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 the BMIBI BIC, 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.
This segment of the Des Moines River was sampled as part of the 1998-99 statewide study of freshwater mussels in Iowa streams and rivers (Arbuckle et al. 2000). 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 streams and rivers from the mid-1980s to the late 1990s. For stream segments having four or more species reported for the 1984-95 survey, 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. The results of this sampling on the Des Moines River, however, do not meet IDNR guidelines for developing an assessment of support for the aquatic life uses. Species richness of freshwater mussels at the one sample site in this segment was 2 in the 1984-85 period and was 0 in the 1998-99 period, respectively, for percent change of minus 100%. Based on these results, the aquatic life uses are considered “not assessed” due (1) to IDNR’s assessment methodology in which assessment decisions are developed only for those stream segments having an average of four or more species reported in the 1984-85 (Frest) survey and (2) the difficulty of interpreting status of mussel communities showing relatively low species richness during the both the historical (1984-85) and current (1998-99) surveys.
Fish consumption uses remain assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Dolliver State Park in 2005 and downstream of Fort Dodge in 2009, and REMAP monitoring near Coalville in 2006. The 2005 composite samples of fillets from common carp and freshwater drum had low levels of contaminants. Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.183 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. Levels of primary contaminants in the composite sample of freshwater drum fillets were as follows: mercury: 0.139 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. The September 2006 IDNR/UHL REMAP project (Site 221) fish tissue monitoring showed low levels of the primary contaminants in the composite samples of common carp fillets: mercury: 0.239 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. The 2009 composite samples of fillets from common carp and freshwater drum had low levels of contaminants. Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.193 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. The level of mercury in the composite sample of freshwater drum fillets was 0.149 ppm. The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes. The fish contaminant data generated from the 2005 and 2009 RAFT and 2006 REMAP sampling conducted in this assessment segment suggest that levels of all contaminants from this monitoring were below advisory trigger levels, thus suggesting the continued “full support” of fish consumption uses.
