Assessment Comments
Assessment is based on: (1) results of monitoring conducted on South Fork Iowa River 2 miles northeast of New Providence from January 2004 through December 2006 by USGS as part of the National Water Quality Assessment Program (NAWQA) (eastern Iowa river basins study unit, station 05451210) and (2) a review of the history of fish kills in this watershed.
Basis for Assessment
[Note: Prior to the current (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 “not assessed” due to the lack of information upon which to base an assessment. 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 sources of information for this assessment include (1) results of monitoring conducted on South Fork Iowa River 2 miles northeast of New Providence from January 2004 through December 2006 by USGS as part of the National Water Quality Assessment Program (NAWQA) (eastern Iowa river basins study unit, station 05451210) and (2) a review of the history of fish kills in this watershed.
EXPLANATION: The monitoring conducted by USGS on South Fork Iowa River from 2004-2006 did not include analysis for indicator bacteria. Thus, due to this lack of information, an assessment of support of the presumptive Class A1 uses was not developed.
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 40 samples collected from January 2004 through December 2006 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 one of the 43 samples analyzed from the USGS station violated the Class B(WW1) criterion of 6.5 pH units. The frequency of pH violations at this station (2%), however, does not suggest impairment. 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.
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 10 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 NAWQA project. These data are now considered too old (greater than 10 years) to accurately characterize current water quality conditions.
