Assessment Comments
Assessment is based on: (1) results of monitoring conducted by USGS near New Providence from January 2006 through December 2008 by USGS (station 05451210), bacteria monitoring conducted by the National Laboratory for Agriculture and the Environment from 2006-08 near New Providence (station SF450), and and (3) a review of the history of fish kills in this watershed.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this river 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 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), this segment is also now presumptively 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).]
SUMMARY: The presumptive 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 (monitored) as "fully supported" based on (1) results of chemical/physical water quality monitoring and (2) the lack of recent fish kills in this watershed. Fish consumption uses are “not assessed” due to the lack of recent fish contaminant monitoring in this assessment segment. The designated human health (HH/fish) uses are assessed (monitored) as “fully supported” despite levels of dieldrin in water occasionally that exceed Iowa’s Human Health criterion. The sources of information for this assessment include (1) results of monitoring conducted by USGS on South Fork Iowa River at two stations: station 05451210 located 2 miles northeast of New Providence from January 2006 through December 2008 and station 05451200 from June 2007 through September 2008, (2) results of monitoring conducted by the National Laboratory for Agriculture and the Environment (NLAE), Ames, IA (*formerly, National Soil Tilth Laboratory), from 2003-09 approximately 2.5 miles NNE of New Providence (station SF450), and (3) a review of the history of fish kills in this watershed.
EXPLANATION: The monitoring conducted by USGS on South Fork Iowa River from 2006-2008 did not include analysis for indicator bacteria. Monitoring by the NLAE approximately 2.5 miles NNE of New Providence (station SF450) from 2006-08, however, did include analysis for indicator bacteria (E. coli). Based on this monitoring, the Class A1 uses are assessed (monitored) as "not supported." The geometric mean of E. coli in the 63 samples collected at station SF450 (1,626 orgs/100 ml) far exceeds the Iowa Class A1 water quality criterion of 126 orgs/100ml. Fifty-five of the 63 samples (87%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and according to IDNR’s assessment/listing methodology, if the geometric mean level 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). Note: the geometric mean of E. coli at station SF450 is based on raw data for the 63 samples collected during the recreation seasons of 2006 through 2008. If daily duplicate samples and other serially correlated samples collected on consecutive days are averaged, the geometric mean of the resulting 19 independent measurements of E. coli is 630 orgs/100 ml with 14 of the 19 samples (74%) exceeding Iowa’s single-sample maximum criterion. Thus, whether raw data or averaged data are used, the results of monitoring at this station suggest “nonsupport” of the presumptive Class A1 (primary contact recreation) uses.
The assessment of support of the Class B(WW1) uses is based on the USGS/NAWQA monitoring near New Providence that showed (1) no violations of Class B(WW1) water quality criteria for dissolved oxygen or ammonia-nitrogen in the approximately 65 samples collected from January 2006 through December 2008 at station 05451210 and in the two samples collected at station 05451200 from June 2007 through September 2008 and (2) no violations of the Class B(WW1) chronic water quality criterion for pesticides in the samples analyzed during this period. The level of pH in two of the 69 samples analyzed from station 05451210 violated the Class B(WW1) criterion of 6.5 pH units. The frequency of pH violations at this station (3%), however, does not suggest impairment of either the Class B(WW1) aquatic life uses or the presumptive Class A1 primary contact recreation uses. According to U.S. EPA guidelines (U.S. EPA 1997b, page 3-17), a violation frequency of less than 10% for conventional parameters such as pH suggest "full support" of aquatic life uses.
Results of monitoring by the NLAE approximately 2.5 miles NNE of New Providence (station SF450) from 2003-09 also suggest “full support” of the Class B(WW1) uses. This monitoring included continuous monitoring for dissolved oxygen, pH, and water temperature for the years 2003, 2005, and 2009. Due to the lack of data for the 2006-08 period that was used for the 2010 Section 305(b)/303(d) assessment/listing cycle, all data from station SF450 from 2003, 2005, and 2009 were used for this assessment. Data for daily maximum, mean, and minimum values were provided to Iowa DNR. None of the 539 daily maximum and minimum values exceeded the Class B(WW1) pH criteria of 9.0 and 6.5 pH units, respectively, with pH values ranging from 8.8 to 6.9 units over the 2003-09 period. None of the 330 daily maximum values for water temperature exceeded Iowa’s “added heat” criterion of 32C. Of the 568 daily minimum values for dissolved oxygen, 35 values (6.2%) were below Iowa’s Class B(WW1) criterion of 5.0 mg/l (minimum value = 4.39 mg/l). These minimum values tended to occur in the late night or early morning hours during summer months (July through August). According to U.S. EPA guidelines (U.S. EPA 1997b, page 3-17), a violation frequency of less than 10 % for conventional parameters such as dissolved oxygen suggests "full support" of aquatic life uses.
Although the results of chemical/physical monitoring suggest full support of aquatic life uses, the watershed of the South Fork Iowa River has a history of repeated fish kills, most often in the upper reaches of the stream. The most recent kill for this watershed in the IDNR Fish Kill Database occurred in the headwaters (Hamilton County reach) in September 2001 and was caused by animal waste. The most recent kill documented in the lower segments of this stream occurred approximately 15 years ago (July 1995). Thus, based on the (1) results of water quality monitoring and (2) the lack of recent fish kills in this watershed, the Class B(WW1) uses are now assessed as “fully supported”.
Fish consumption uses are not assessed due to the lack of recent fish contaminant monitoring in this river segment. Previous assessments were based on results of fish contaminant monitoring conducted by USGS in 1995 as part of the National Water Quality Assessment project. These data are now considered too old (greater than 10 years) to accurately characterize current water quality conditions. Results of water quality monitoring at USGS station 05451210 during the 2006-2008 period showed that six of 56 samples (11%) contained “estimated” values of dieldrin ranging from 0.002 to 0.007 ppb. According to USGS, concentrations are reported as “estimated” because there is some uncertainty in the value. All these estimated values far exceed Iowa’s human health (HH/fish) criterion of 0.00052 ppb. According to USGS, the results of a review these data indicate that there is no indication that these estimated sample results are the result of contamination from lab processing and analysis. Thus, the estimated dieldrin concentrations are legitimate and can be compared to the respective water quality criterion. Although USGS acknowledges some uncertainty regarding “estimated” values, the dieldrin values from station 05451210 all far exceed Iowa HH/fish criterion of 0.00052 ppb. For purposes of Section 305(b) assessment, Iowa DNR views the Human Health criterion for dieldrin as analogous to a chronic criterion for a toxic parameter. Thus, impairment of the HH use by dieldrin would be suggested if significantly more than 10% of the samples violated this criterion. According to IDNR’s assessment/listing methodology, the frequency of violation of the HH criterion for dieldrin (six of 54 samples or 11%), however, is not significantly greater than 10 percent; thus, these violations do not indicate impairment of the HH/fish-consumption use.
