Assessment Comments
Assessment is based on: (1) results of monitoring conducted by USGS near New Providence from March 2008 through December 2010 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, 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 remain assessed (monitored) as “not supported” (IR Category 5a) 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 assessment segment. Fish consumption uses remain “not assessed” due to the lack of recent fish contaminant monitoring in this assessment segment. The designated human health (HH/fish) uses are assessed (evaluated) as “partially supported” (IR Category 3b) due to violations of the HH/fish criterion for dieldrin. The sources of information for this assessment include (1) results of monitoring conducted by USGS on South Fork Iowa River at station 05451210 located 2 miles northeast of New Providence from March 2008 through December 2010 and (2) a review of the history of fish kills in this watershed. Although the previous (2010) assessment also used data from USGS station 05451200, monitoring at this station during the 2008-10 timeframe was limited to a maximum of two samples per parameter over the three-year period; this limited amount of data is not useful for purposes of Section 305(b) assessments or Section 303(d) listings. Also, the previous (2010) assessment used data for indicator bacteria provided by the National Laboratory for Agriculture and the Environment (NLAE), Ames, IA, from 2003-09 for their station SF450 located approximately 2.5 miles NNE of New Providence. Data for the current (2012) assessment period were requested from NLAE in October 2011. The IDNR request was acknowledged by NLAE, but the data were not received by IDNR and are thus were not used for this assessment.
EXPLANATION: The monitoring conducted by USGS on South Fork Iowa River does not include analysis for indicator bacteria. Thus, results of monitoring for indicator bacteria (E. coli) by the NLAE approximately 2.5 miles NNE of New Providence (station SF450) from 2006-08 were used. Based on this monitoring, the Class A1 uses remain 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, pH, or ammonia-nitrogen in the approximately 50 samples collected from March 2008 through December 2010 at station 05451210 and (2) no violations of the Class B(WW1) chronic water quality criterion for pesticides in the 36 samples analyzed during this period. According to U.S. EPA guidelines and IDNR’s assessment/listing methodology, these results suggest “full support” of the Class B(WW1) aquatic life uses.
Results of monitoring conducted 2003-09 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. 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 documented in the lower segments of this stream occurred over 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 assessment segment, the Class B(WW1) uses are assessed as “fully supported”.
Fish consumption uses remain 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 2008-2010 period showed that four of 36 samples (11%) contained “estimated” levels of dieldrin that violated Iowa’s HH/fish criterion of 0.00052 ppb; the remainder of the samples were below the level of detection (0.009 ug/l). According to USGS, concentrations are reported as “estimated” because there is some uncertainty in the value. Also, 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.
Based on the results of USGS monitoring for dieldrin, the Human Health designated use (including the fish consumption use) is assessed (evaluated) as “partially supporting” (IR Category 3b-potentially impaired). According to IDNR’s assessment/listing methodology, if the average level of a toxic metal or pesticide is greater than its respective human health criterion, impairment ("nonsupport") of the Human Health use is indicated. However, the samples with detectable levels of dieldrin were too few (four) and the method detection level (0.009 ug/l) was far too high (16 times the HH criterion for dieldrin) to allow calculation of a meaningful summary statistic (i.e., mean) for dieldrin at this monitoring station. Also, levels of dieldrin in Iowa fish have declined significantly since the early to mid-1980s when levels of 300 ppb to 500 ppb were not un common (see ftp://ftp.igsb.uiowa.edu/igspubs/pdf/WFS-2006-05.pdf). Thus, the HH/fish consumption uses are assessed (evaluated) as “partially supported” (IR Category 3b) for the 2012 Integrated Reporting cycle. IR Category 3b waters will be added to Iowa’s list of waters in need of further investigation.
