Raven Creek IA 02-IOW-723

Assessment Comments

Assessment is based on results of USGS ambient water quality monitoring conducted on Raven Creek near Montour from April through December 2006.

Basis for Assessment

[Note:  Prior to the current (2008) Section 305(b) cycle, this stream segment was designated only for Class B(LR) aquatic life 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.   The stream remains designated for aquatic life uses (now termed Class B(WW2) aquatic life uses).   Thus, for the current (2008) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) 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 Class B(WW2) aquatic life uses are assessed (evaluated) as "fully supported” based on results of chemical/physical monitoring in 2006.   The assessment of support of the Class B(WW2) uses is based on the results of USGS ambient water quality monitoring conducted on Raven Creek near Montour from April through December 2006.

EXPLANATION:  The monitoring conducted on Raven Creek in 2006 USGS 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.  

Results of the USGS ambient water quality monitoring from April through December 2006 showed no violations of Class B(WW2) water quality criteria in the approximately six samples analyzed for dissolved oxygen, pH, and ammonia.   In addition, none of the approximately seven samples analyzed for toxic metals and pesticides exceeded the respective Class B(WW2) chronic criteria.   The number of samples collected at this station (seven) is relatively low and does not meet IDNR guidelines for developing a “monitored” (higher confidence) assessment (i.e., at least 10 samples collected over a three-year period).   Thus, the assessment type is considered “evaluated” (lower confidence).