Assessment Comments
Assessment is based on results of (1) USGS/NAWQA monitoring of water quality from 2002-04, (2) USGS/NAWQA fish contaminant monitoring in 1995, and (3) occurrence of fish kills in the watershed.
Basis for Assessment
SUMMARY: The Class B(WW) 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. The fish consumption uses remain assessed (evaluated) as “fully supported" based on results of fish contaminant monitoring in 1995. 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 2002 through August 2004 by USGS as part of the National Water Quality Assessment Program (NAWQA) (eastern Iowa river basins study unit, station 05451210), (2) results of fish contaminant monitoring conducted as part of the USGS NAWQA program near New Providence in 1995 and (3) a review of the history of fish kills in this watershed.
EXPLANATION: The assessment of support of the Class B(WW) uses for the 2006 reporting cycle is based on the USGS/NAWQA monitoring near New Providence that showed (1) no violations of Class B(WW) water quality criteria for pH, dissolved oxygen, or ammonia-nitrogen in the approximately 25 samples collected from January 2002 through August 2004 and (2) no violations of the Class B(WW) chronic water quality criterion for pesticides in the 22 samples analyzed during this period.
Although these results 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 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(WW) uses are now assessed as “fully supported”.
Fish consumption uses were assessed (evaluated) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Providence, IA, in 1995 as part of the USGS NAWQA project. Because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).
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. Prior to 2006, IDNR used action levels published by the U.S Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa. In an effort to make Iowa’s consumption more compatible with the various protocols used by adjacent states, the Iowa Department of Public Health, in cooperation with Iowa DNR, developed a risk-based advisory protocol. This protocol went into effect in January 2006 (see http://www.iowadnr.gov/fish/news/consump.html for more information on Iowa’s revised fish consumption advisory protocol). Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest either a threat to, or impairment of, fish consumption uses. This scenario, however, does not apply to the fish contaminant data generated from the 1995 sampling conducted near Providence: levels of all contaminants from this monitoring were below advisory trigger levels, thus suggesting the continued “full support” of fish consumption uses.
