Little Fox River IA 04-FOX-996

Assessment Comments

Assessment remains based on results of UGSG ambient water quality monitoring in 1998 and 1999 near Cantril.

Basis for Assessment

[Note:  Prior to the current (2008) Section 305(b) cycle, this stream segment was classified only for general 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 now presumptively designated for Class A1 (primary contact recreation) uses and for Class B(WW1) aquatic life uses.   According to the Iowa Water Quality Standards, all perennial rivers and streams and all intermittent streams with perennial pools that are not specifically listed in the Iowa surface water classification are designated as Class A1 and Class B(WW1) waters.   Thus, for the current (2008) assessment, perennial flow is presumed, and the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria.]

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 presumptive Class B(WW1) aquatic life uses remain assessed as "fully supporting" based on results of ambient water quality monitoring conducted by the U.S.  Geological Survey in 1998 and 1999 near Cantril in Van Buren County.     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).   This is the same assessment as that developed for the 2004 and 2006 assessment/listing cycles.

EXPLANATION:  Continued to use the assessment of support of the aquatic life uses developed for the 2000 report.   The data upon which this assessment was based were collected by USGS in 1998 and 1999.   The following is taken from the assessment developed for the 2000 reporting cycle [reference to "Class B(LR)" is changed to "Class B(WW2)" to reflect recent changes in the Iowa WQ Standards]:   The USGS monitoring showed no violations of Class B(WW2) water quality criteria for dissolved oxygen, pH, and ammonia-nitrogen in the 13 samples collected.   None of the nine samples analyzed contained toxic metals above Class B(WW2) chronic criteria.    Although not designated for Class C (drinking water) uses, four of the 11 samples from this station analyzed for pesticides during the 1998-1999 period exceeded the U.S.  EPA MCL of 3.0 ug/l.   None of the 13 samples analyzed exceeded the nitrate MCL of 10.0 mg/l.   Thus, based on results of chemical water quality monitoring 1998-1999 biennial period, the general aquatic life uses of this stream reach are assessed as "fully supported."  Biological monitoring is needed to determine the status of the aquatic communities of this stream reach.